Revised Lecture By Sir Janggo.docx

CONCRETE Concrete – is defined as the composition of paste (water and cement) and mineral aggregates (coarse and fine aggregates) mixed in the proportions specified. It is a construction material that is made of Portland cement (or some other form of hydraulic cement), aggregate ( gravel and sand), and water mixed in predetermined proportions. Concretes solidifies and hardens after mixing and placement due to a chemical process known as hydration.

311.2.2 FINE AGGREGATES It shall consist of natural sand, stone screenings or other inert materials with similar characteristics, or combinations thereof, having hard, strong and durable particles. Fine aggregate from different sources of supply shall not be mixed or stored in the same pile nor used alternately in the same class of concrete without the approval of the Engineer. It shall not contain more than three (3) mass percent of material passing the 0.075 mm (No. 200 sieve) by washing nor more than one (1) mass percent each clay lumps or shale. The use of beach sand will not be allowed without the approval of the Engineer. If the fine aggregate is subjected to five (5) cycles of the sodium sulfate soundness test, the weighted loss shall not exceed 10 mass percent. The fine aggregate shall be free from injurious amounts of organic impurities. If subjected to the colorimatic test for organic impurities and a color darker than the standard is produced, it shall be rejected. However, when tested for the effect of organic impurities on strength of mortar by AASHTO T 71, the fine aggregate may be used if the relative strength at 7 and 28 days is not less than 95 percent.

GRADING REQUIREMENTS FOR FINE AGGREGATES Sieve Desination

Mass percent Passing

9.5mm(3/8 in) 4.75mm(No.4) 2.36mm(No.8) 1.18mm(No.16) 0.600mm(No.30) 0.300(No.50) 0.150mm(No.100)

100 95-100 45-80 5 - 30 0-10

FINENESS MODULUS: Is the sum of total aggregates retained on specified sieve( N0.4 – 100) divided by 100. Based on ASTM C33, FM of fine aggregates must be within 2.3 to 3.1., the higher the FM the coarser the aggregates and usually a lower FM results in more paste making concrete easier to finish. In high cement factor used in the production of a high strength concrete, a coarser sand with a FM of 3.0 will produce concrete with the best workability and highest compressive strength . However, ACI table V have standards and corrections to be used in calculation of Concrete Mix Design. 311.2.3 COARSE AGGREGATE

It shall consist of crushed stone, gravel, blast furnace slag, or other approved inert materials (coralline or dolomites) of similar characteristics, or combinations thereof, having hard, strong, durable pieces and free from any adherent coatings. It shall contain not more than one (1) mass percent of material passing the 0.075 mm (No. 200) sieve, not more than 0.25 mass percent of clay lumps, nor more than 3.5 mass percent of soft fragments. If the coarse aggregate is subjected to five (5) cycles of the sodium sulfate soundness test, the weighted loss shall not exceed 12 mass percent. It shall have a mass percent of wear not exceeding 40 when tested by AASHTO T 96. If the slag is used, its density shall not be less than 1120 kg/m3. The gradation of the coarse aggregate shall conform to Table 311.2. Only one grading specification shall be used from any one source.

PARTICLE SHAPE AND SURFACE TEXTURE Particle shape includes two properties: sphericity and roundness. Sphericity is a measure whether the particles is compact in shape That is , if it is close to being a sphere or a cube as opposed to being flat (disk-like) or elongated ( needle-like). Roundness refers to a relative sharpness or angularity of the particle edges and corners. The higher the sphericity ( the closer the particle is to a sphere or cube ), the lower will be its surface area and, therefore, lower will be its demand for mixing water in concrete and lower will be the amount of sand needed in the mixture to provide workability. More angular and less spherical coarse aggregates will require higher mixing water and fine aggregate content to provide the needed workability.

Surface texture refers to degree of roughness or irregularity of the aggregate particle surface. Usually, terms such as rough, granular, crystalline, smooth, or a glassy are used to describe surface texture rather than using any quantitative method. Smooth particles will require less mixing water-cementitious material ratio to produce concrete with a given workability, but will have less bonding are with the cement paste than rougher particles. SIGNIFICANCE OF PARTICLE SHAPE AND SURFACE TEXTURE The shape and surface texture of the individual particles of sand, rock, gravel, slag, or light weight aggregate making up an aggregate will have an important influence on the workability of freshly mixed concrete and the strength of hardened concrete. Fine aggregate particle shape and texture affects concrete in one major way-through its influence on the workability of fresh concrete. Angular rough sands will require more mixing water in concrete than rounded smooth fine aggregates to obtain the same level of slump and workability, with other factors being equal. This in turn , will affect the water- cementitious material ratio if the cementitious content is held constant; or it will require an adjustment in the cementitious content if a certain water-cementitious material ratio is needed. The influence of fine aggregate shape and texture on the strength of hardened concrete is almost entirely related to its influence on the resulting water- cementitious material ratio of the concrete if the fine aggregate has a grading within the normally accepted limits and its grading is taken into account in selecting concrete proportions. Coarse aggregate shape and texture also affect mixing water requirement and water-

cementitious material ratio in a manner similar to that of fine aggregate. However, coarse aggregate particles , due to their much smaller ratio of surface area to volume , affect strength through a more complex relationship of aggregate to cement paste bonding properties and concrete water – cementitious material ratio. Therefore , the effects of aggregate shape and texture on the strength of hardened concrete should not be overgeneralized. It has been demonstrated that the failure of a concrete strength specimen most often starts as microcracks between the paste or mortar and the surfaces of the largerst coarse aggregate particles. This a bond failure mode. Angular rough-textured aggregates, for example have an increased surface area are bond to the cement paste when compared to similar size rounded particles. Considering all of the factors that have an effect on concrete strength, the following appear to be most important: 1. The surface area available for bond to the cement paste. Here, the shape and texture of the largest particles is the most important. 2. The type of surface texture of the largest pieces, which affects the bond strength per unit of surface area. The mineralogy and crystal structure of these pieces will affect bond strength. 3. The relative rigidity of the aggregate particles compared to the surrounding paste or mortar. The closer the deformation characteristics of the aggregate are to that of the surrounding media, the lower the stresses at the interface will be that developed at particle surfaces. 4. Maximum size of the aggregate. For a given water-cementitious material ratio, as the size of the larger particle is increased, the likelihood of a paste to aggregate bond failure increases since stresses at the interface will be higher than those for a smaller particles.

GRADING REQUIREMENTS FOR COARSE AGGREGATES

SIEVE DESIGNATION Standard mm. 75 63 50 37.5 25 19 12.5 4.75

Alternate U.S. Standard 3 IN 2 1/2 2 1 1/2 1 3/4 1/2 NO.4

MASS PERCENT PASSING GRADING A

GRADING B

GRADING C

100 90-100 25-60 0-10 0-5 -

100 90-100 35-70 0-15 0-5 -

100 95-100 35-70 10-30 0-5

ITEM 714 – WATER Mixing water is the water available to come in contact with cement particles during the initial phases of the chemical reaction between cement and water that takes place in the concrete. This Item covers criteria for acceptance of Questionable Water either natural or wash water for use in concrete. The mixing water shall be clear and apparently clean. If it contains quantities or substances that discolor it or make it smell or taste unusual or objectionable, or cause suspicion, it shall not be used unless service records of concrete made with it (or other information) indicated that it is not injurious to the quality, shall be subject to the acceptance criteria as shown in Table 714.1 and Table 714.2 or as designated by the purchaser. When wash water is permitted, the producer will provide satisfactory proof or data of non-detrimental effects if potentially reactive aggregates are to be used. Use of wash water will be discontinued if undesirable reactions with admixtures or aggregates occur.

Table 714.1 – Acceptance Criteria for Questionable Water Supplies

Physical Properties

Limits

Compressive strength, min. % Control at 7 days Time of Setting deviation from control Time of Setting (Gillmore Test) Initial Final Set Appearance Color Odor Total Solids pH value

90 from 1:00 earlier to 1:30 later No marked change No marked change Clear Colorless Odorless 500 parts/million max. 4.5 to 8.5

Table 714.2 – Chemical Limitation for Wash Water

Chemical Properties

Chemical Requirements, Minimum Concentration Chloride as CL (-1) expressed as a mass percent of cement when added to the concrete mixtures shall not exceed the following levels: 1. Prestressed Concrete 2. Conventionally reinforced concrete in a moist environment and exposed to chloride 3. Conventionally reinforced concrete in a moist environment and exposed to chloride 4. Above ground building construction where the concrete will stay dry Sulfate as SO4 , ppmA Alkalies as (Na2O + 0.658 K2O), Ppm Total Solids, ppm

Limits

0.06 percent 0.10 percent 0.15 percent No limit for corrosion

3000 600 5000

Wash water reused as mixing in concrete may exceed the listed concentreation of sulfate if it can be shown that the concentration calculated in the total mixing

water, including mixing water on the aggregate and other sources, does not exceed that stated limits. Water will be tested in accordance with, and shall meet the suggested requirements of AASHTO T 26. Water known to be of potable quality may be used without test.

DETERMINATION OF SPECIFIC GRAVITY AND ABSORPTION OF FINE AND COARSE AGGREGATES

SIGNIFICANCE: 1. Bulk specific gravity is the characteristic generally used for calculation of the volume by the aggregate in various mixtures containing aggregate including portland cement concrete, analyzed on an absolute volume basis. 2. Absorption values are used to calculate the change in the weight of an aggregate due to water absorbed in the pore spaces within the constituent, compacted to the dry condition, when it is deemed that the aggregate has been in contact with water long enough to satisfy most of the absorption potential. CALCULATION: For Coarse Aggregate Bulk sp. gr. = A/ (B - C) Absorption, % = [(B – A)/A] x 100 Where: A = weight of oven-dry test sample in air, g, B = weight of saturated-surface-dry test sample in air, g, And C = weight of saturated test sample in water, g

or Fine Aggregate Bulk Sp. Gravity = A/ (B + S – C) Absorption, % = [(S – A)/A] x 100 Where: A = weight of oven-dry specimen in air, g B = weight of pycnometer filled with water, g C = weight of pycnometer with specimen and water to calibration mark. S = weight of saturated surface-dry specimen, g

ABRASION TEST

SIGNIFICANCE This test evaluates the structural strength of coarse aggregate. It gives an indication of quality as determined by resistance to impact and wear. The results do not automatically permit valid comparisons to be made between sources distinctly different in origin, composition or structure.

APPARATUS: 1. 2. 3. 4. 5. 6.

Los Angeles Machine. Standard sieves with pan and cover. Abrasive charges. Pans. Balance and weights. Oven-uniform temperature of 110+5oC (230+9oF).

PROCEDURE: The test sample shall consist of clean aggregate which has been oven-dried to constant weight/mass at 110+5oC and shall conform to one of the following table:

Sieve

Size

Grading and Weight of Test Sample, g

Passing

Retained on

A

B

C

D

37.5 mm

25 mm

1250+25

-

-

-

25 mm

19 mm

1250+25

-

-

-

19 mm

12.5 mm

1250+10

2500+10

-

-

12.5 mm

9.5 mm

1250+10

2500+10

-

-

9.5 mm

6.3 mm

-

-

2500+10

-

6.3 mm

4.75 mm

-

-

2500+10

-

4.75 mm

2.36 mm

-

-

-

5000+10

The abrasive charge shall consist of cast-iron spheres or steel spheres approximately 46.8 mm in diameter and each weighing between 390 and 455 grams. The charge depending upon grading of test sample shall be as follows:

Grading

No. of Spheres

Weight of charge, g

A

12

5000 + 25

B

11

4584 + 25

C

8

3330 + 20

D

6

2500 + 15

1) Place test sample and abrasive charge in the Los Angeles machine rotated at a speed of 30 to 33 rpm 500 revolutions. 2) At completion of test, discharge material from the machine. Make a preliminary separation of the samples on a sieve coarser than 1.70 mm. 3) Sieve finer portion on the 1.70 mm sieve, using the standing procedure of sieving aggregates. 4) Wash all materials coarser than 1.70 mm, dry to constant weight/mass at about 105oC to 110oC and weigh accurately to the nearest 1 gram.

CALCULATION: Express the difference between the original weight/mass and the weight/mass of material coarser than 1.70 mm sieve as a percentage of the original weight/mass of test sample. This value represents the percent abrasion loss.

Original mass of sample, g

Sample retained on -

No. 1.70 mm sieve, (No. 12) g

Percentage of Wear, % = ------------------------------------------------------------------------------- x 100 Original mass of sample, g

DETERMINATION OF ORGANIC IMPURITIES IN SANDS FOR CONCRETE

SIGNIFICANCE The test determines the presence of the injurious organic compounds in natural sands which are to be used in cement mortar or concrete. The purpose of the test is to furnish a warning that further tests of the sand are necessary before they are approved for use. APPARATUS:

Glass bottles – approximately 350 ml graduated clear glass prescription bottle with rubber, cork or other watertight stoppers, not soluble in the specified reagents. SAMPLE: Obtain a sample of sand weighing about 450g in accordance with standard procedure in Reducing Field Samples of Aggregate to Testing Size.

REAGENTS AND REFERENCE STANDARD COLOR SOLUTION

1. Sodium hydroxide solution (3 percent) – dissolve 3 parts by weight of sodium hydroxide (NaOH) in 97 parts of water. 2. Reference color standard solution – dissolve reagent grade potassium dichromate (K2Cr2O7) in concentrated sulfuric acid (sp. gr. 1.84) at the rate of 0.250 g per 100 ml of acid. The solution if necessary to effect solution. PROCEDURE: 1. Fill a glass bottle to the approximately 130 ml level with the sample of the sand to be tested. 2. Add a 3 percent NaOH solution in water until the volume of the sand and liquid, indicated after shaking, is approximately 200ml. 3. Stopper the bottle, shake vigorously, and then allow to stand for 24 hr.

UNIT WEIGHT/MASS DETERMINATION IN AGGREGATE

SIGNIFICANCE:

Values of unit weight/mass are used in volumetric- gravimetric evaluations. In volumetric batching of concrete aggregate, the unit mass should be known to convert weight/mass into loose volume.

CONCRETE MIX DESIGN

Fine Aggregates

CEMENT FACTOR 11 BAGS Structural Concrete Coarse Aggregates

Type: Natural Fine Modulos: 2.87 Bulk Sp. Gr.: 2.57 Moisture Content: 7.21 Absorption: 3.82 Dry Unit Wt.: 1791.76kg/m3 Sp. Gr. Cement: 3.12 Slump : 101.6mm

Type: Rounded Max Size: 19.0 mm Abrasion Loss: 29 Bulk Sp. Gr.: 2.60 Moisture Content: 1.75 Absorption: 2.09 Dry Unit Wt. Ave: 1559.70kg/m3

FOR STRUCTURAL CONCRETE:

Abs. Vol. of Concrete

𝟏 𝟏𝟏 (𝒄𝒆𝒎𝒆𝒏𝒆𝒕 𝒇𝒂𝒄𝒕𝒐𝒓)

Abs. Vol. of 40 kg Bag Cement

= . 𝟎𝟗𝟎𝟗

𝟒𝟎 𝟑.𝟏𝟐 (𝒔𝒑.𝒈𝒓.) 𝒙 𝟏𝟎𝟎𝟎𝒌𝒈/m3

= (𝟎. 𝟎𝟏𝟐𝟖𝟐)

Adjustment from table V for water content considering the max. size of aggregates.

Determine the corrected slump:

Slump correction

= =

Actual slump−Std.slump 25.4 101.6mm−76.2mm

(±3%)

25.4mm

= +3%

=

Net Water

𝟏𝟖𝟒+𝟏𝟖𝟒(𝟑%) 𝟏𝟖𝟗.𝟓𝟐 𝐥𝐢𝐭𝐞𝐫𝐬/𝐦𝟑

Abs. Vol. of Water per Bag =

189.52kg/m3 11 bags/m3x1000 kg/m3

= 0.01722 m3/bag

Abs. Vol. of Cement and Water = .01282 + .01722

= . 𝟎𝟑𝟎𝟎𝟒

Abs. Vol. of Fine Aggregates and Coarse = . 𝟎𝟗𝟎𝟗− . 𝟎𝟑𝟎𝟎𝟒

= . 𝟎𝟔𝟎𝟖𝟕 Corrections of Fine Aggregates, % of Total Aggregates. % sand of total aggregates = 46 considering 19mm dia. max. size Water/Cement

=

𝟏𝟖𝟗.𝟓𝟐 𝟏𝟏𝐱𝟒𝟎

= . 𝟒𝟑

Water/Cement Corrections

% F.m. corr =

=

.𝟒𝟑− .𝟓𝟕 (𝟏)

𝑨𝒄𝒕𝒖𝒂𝒍 𝒇.𝒎.−𝒔𝒕𝒅.𝒇.𝒎. 𝟎.𝟏

.𝟎𝟓

= −𝟐. 𝟖

= . 𝟓%

=

( 𝟐.𝟖𝟕−𝟐.𝟕𝟓 ) .𝟏

. 𝟓%

= .60 Total Corrections = .60% - 2.8% = -2.2%

% sand from table V = 46 – 2.2 = 43.8%

Abs. vol. of F.A = abs vol. of aggts. (43.8%) = .06087 (43.8%) = .02666

Abs vol. of C.A = .06087 - .02666 = 0.3421

Batch Weight

Abs Vol.

Sp. Gr.

CEMENT

.012821

3.12

1000

40

FINE AGGTS.

.02666

2.57

1000

68.516

COARSE AGGTS. .03421

2.6

1000

88.946

WATER

1.0

1000

17.22

.1722

Corrected Weight F.A = 68.516 ( 𝟏 +

𝟕.𝟐𝟏−𝟑.𝟖𝟐 𝟏𝟎𝟎

)

𝟕𝟎. 𝟖𝟒 𝒌𝒈 C.A = 88.946 ( 𝟏 − = 𝟖𝟖. 𝟔𝟒 𝒌𝒈

[𝟐.𝟎𝟗−𝟏.𝟕𝟓] 𝟏𝟎𝟎

)

DENSITY

UNCORRECTED CORRECTED

H2O = [ 40+ 68.516+ 88.946+ 17.22 ] – [ 40 + 70.84 + 88.64 ] H2O = 𝟏𝟓. 𝟐𝟎𝟐 𝒌𝒈

CONCRETE MIX DESIGN CEMENT FACTOR 10 BAGS FINE AGGREGATES

COARSE AGGREGATES

Type: Natural Fine Modulos: 3.61 Bulk Sp. Gr.: 2.65 Moisture Content: 5.65 Absorption: 2.67 Dry Unit Wt.: 1791.76kg/m3 Sp. Gr. Cement: 3.15 Slump : 101.6mm

Type: Rounded Max Size: 76.5 Abrasion Loss: 29 Bulk Sp. Gr.: 2.67 Moisture Content: 1.48 Absorption: 1.81 Dry Unit Wt. Ave: 1559.70kg/m3

TYPE OF CONCRETE PCCP 𝟏

Abs. Vol. of Concrete Abs. Vol. of Cement Net Water = 𝟏𝟒𝟖 +

= . 𝟏𝟎 m3

𝟏𝟎 𝟒𝟎

𝟑.𝟏𝟓 𝒙 𝟏𝟎𝟎𝟎

= 𝟎. 𝟎𝟏𝟐𝟔𝟗

𝟏𝟒𝟖(𝟏𝟎𝟏.𝟔−𝟕𝟔.𝟐)𝟑% 𝟐𝟓.𝟒

Abs. Vol. of Water and Cement:

− 𝟒. 𝟕(𝒇𝒐𝒓 𝒍𝒆𝒔𝒔 𝒘𝒐𝒓𝒌𝒂𝒃𝒍𝒆 𝒄𝒐𝒏𝒄. ) . 𝟎𝟏𝟒𝟕𝟕+. 𝟎𝟏𝟐𝟔 = . 𝟎𝟐𝟕𝟒𝟔

Abs. Vol. of Fine Aggregates and Coarse Aggregates = .10 - .02746 = .07254 Water/Cement Ratio =

𝟏𝟒𝟕.𝟕𝟒 𝟏𝟎𝒙𝟒𝟎

= 𝟎. 𝟑𝟔𝟗 𝒍𝒊𝒕𝒆𝒓𝒔/𝒌𝒈

Water/Cement Corrections (. 𝟑𝟔𝟗− . 𝟓𝟕) (

𝟏

𝟎.𝟓

= −𝟒. 𝟎𝟐

)

= 147.74

Corrections for Fineness Modulus: [𝟑. 𝟔𝟏 − 𝟐. 𝟕𝟓).

.𝟓 .𝟏𝟎

= +𝟒. 𝟑% Total Corrections

+𝟒. 𝟑 −𝟒. 𝟎 −𝟑 − 𝟐. 𝟕𝟐% Table V

𝟑𝟏% − 𝟐. 𝟕𝟐% = 𝟐𝟖. 𝟐𝟖% Fine Aggregates:

𝟐𝟖𝟐𝟖 (. 𝟎𝟕𝟐𝟓𝟒)− . 𝟎𝟐𝟎𝟓𝟏

Coarse Aggregates: = . 𝟎𝟕𝟐𝟓𝟒−. 𝟎𝟐𝟎𝟓𝟏 = . 𝟎𝟐𝟎𝟓𝟏 =. 𝟎𝟓𝟐𝟎𝟑 Abs. Vol.

BATCH WEIGHT

Sp. Gr.

Density Water

UnCorr. Wt.

Corr. Wt.

Cement

.01269

x

3.15

X

1000

=

40

40

Fine Aggregates Coarse Aggregates

.02051

x

2.65

x

1000

=

54.351

55.97

.05203

x

2.67

x

1000

=

138.92

138.46

Water

14.774

x

1

x

1000

=

14.774

13.615

Corrected Weights: Uncorrected wt (𝐅. 𝐀)[𝟏 +

%𝒇𝒓𝒆𝒆 𝒘𝒂𝒕𝒆𝒓 𝟏𝟎𝟎

= 𝟓𝟒. 𝟑𝟓𝟏 [𝟏 + Fine Aggregates

𝟓.𝟔𝟓− 𝟐.𝟔𝟕 𝟏𝟎𝟎

]

= 𝟓𝟓. 𝟗𝟕

Uncorrected wt (𝐂. 𝐀)[𝟏 −

%𝒘𝒂𝒕𝒆𝒓 𝒓𝒆𝒒𝒖𝒊𝒓𝒆𝒅 𝟏𝟎𝟎

= 𝟏𝟑𝟖. 𝟗𝟐 [𝟏 − Coarse Aggregates

]

= 𝟏𝟑𝟖. 𝟒𝟔

]

𝟏.𝟖𝟏− 𝟏.𝟒𝟖 𝟏𝟎𝟎

]

Water Corrections = [ 𝟒𝟎 + 𝟓𝟒. 𝟑𝟓𝟏 + 𝟏𝟑𝟖. 𝟗𝟐] + 𝟏𝟒. 𝟕𝟕𝟒 − [𝟒𝟎 + 𝟓𝟓. 𝟗𝟕 + 𝟏𝟑𝟖. 𝟒𝟔] = 𝟏𝟑. 𝟔𝟏𝟓 𝒍𝒊𝒕𝒆𝒓𝒔/𝒌𝒈

Item 311 - Portland Cement Concrete Pavement A. Cement Quantity: 9.0 bags /m3 (40 kg/bag) Tests:

For every 2,000 bags or fraction thereof: 1 - Q, Quality Test

B. Fine Aggregate Quantity: A. 0.50 m3 /m3 concrete ----- if using rounded coarse aggregate. B. 0.54 m3 /m3 concrete ----- if using angular or crushed coarse aggregate. Tests: For every 1,500 m3 or fraction thereof: A. For a source not yet tested, or failed in previous quality test: 1 - Q, Quality Test (Grading, Elutriation (Wash), Bulk Specific Gravity, Absorption, Mortar Strength, Soundness, Organic Impurities, Unit Weight, % Clay Lumps and % Shale). B. For a source previously tested and passed quality test: 1 - Q, Quality Test (Grading, Elutriation (Wash), Bulk Specific Gravity, Absorption, and Mortar Strength).

For every 75 m3 or fraction thereof: 1 - G, Grading Test

C. Coarse Aggregate Quantity: a.) 0.77 m3 /m3 concrete ---- if using rounded coarse aggregate. b.) 0.68 m3 /m3 concrete ---- if using angular or crushed coarse aggregate. Tests: For every 1,500 m3 or fraction thereof: a.) For a source not yet tested or failed quality tests:

1- Q, Quality Test (Grading, Bulk Specific Gravity, Absorption, Abrasion, Soundness and Unit Weight).

b.) For a source previously tested and passed quality tests: 1 - Q, Quality Test ( Grading, Bulk Specific Gravity, Absorption and Abrasion).

For every 75 m3 or fraction thereof: 1 - G, Grading Test

D. Water Tests: 1 - Certificate from Project Engineer or 1 - Q, Quality Test if source is questionable.

E. Joint Filler 1.) Poured Joint Filler Tests: 1 - Q, Quality Test on each type of ingredient for each shipment

2.) Premolded Joint Filler Tests: 1 - Q, Quality Test on each thickness of filler for each shipment

F. Special Curing Agents Tests: 1 - Q, Quality test for each shipment

G. Steel Bars Tests: For every 10,000 kg or fraction thereof for each size: 1 - Q, Quality Test (Bending, Tension and Quality Analysis)

H. Concrete Tests: Flexural Strength Test on Concrete Beam Samples:

1 - Set consisting of 3 beam samples shall represent a 330 m2 of pavement, 230 mm depth, or fraction thereof placed each day. Volume of concrete not more than 75 m3

I. Completed Pavement Tests: Thickness determination by concrete core drilling on a lot basis. Five (5) holes per km per lane or five (5) holes per 500 m when two (2) lanes are poured concurrently.

Alexander D. Turingan - 09328774661

TABLE V APPROXIMATESAND AND WATER CONTENTS PER CUBIC METER OF CONCRETE Based on mix having a water cement ratio of 0.57 by weight of 27.7 liters per sack of cement. 76.2 mm. slump and natural sand having fineness modulus of about 2.75 For mixes having either properties see adjustment below Maximum size of Coarse Aggregate mm (inch) 12.7 19.0 25.4 38.1 50.8 76.2 152.4

(1/2) (3/4) (1) (1 ½) (2) (3) (6)

Rounded Coarse Aggregate Sand % of Net Water Content per Total cubic meter Aggregate by Absolute Kilograms Liters Vol. M3 51 199 199 46 184 184 41 178 178 37 166 166 34 157 157 31 148 148 26 131 131

Angular Coarse Aggregate Sand % of Net Water Content per Total cubic meter Aggregate by Absolute Kilograms Liters Vol. M3 56 214 214 51 199 199 46 192 192 42 181 181 39 172 172 36 163 163 31 146 146

Adjustment of above table for other condition CHANGES IN CONDITIONS STIPULATED IN TABLE V

Effect of Value in Table V Percent Sand Net water contents

Each 0.05 increase or decrease in water cement ratio

±1

0

Each 0.1 increase or decrease in fineness modulus of sand Each 25.4 mm increase or decrease in slump

± 1/2

0

0

±3 %

Manufactured Sand

+3

+ 8.9 kg

For less workable concrete as Pavement

-3

‒ 4.7 kg

QUALITY CONTROL IN CONCRETE CONSTRUCTION The two (2) composition of concrete: 1. Paste – water and cement 2. Mineral aggregate – coarse and fine aggregate Requirements of concrete: 1. It should have the required strength 2. It should be uniform, watertight, and resistant wear, weather and other destructive agencies. 3. It should not shrink excessively on cooling or dying on wetting. 4. High resistant to fire, chemicals or abrasion. Factors Affecting Strength/other characteristics of Concrete: 1. Quality of aggregate and cement 2. Quantity of mixing water and cement (the lower the water-cement ratio, the greater is the strength) 3. Curing conditions 4. Time of mixing 5. Age Curing: Is the process maintaining sufficient moisture and a favorable temperature in concrete during the hardening process so that the desired properties for concrete are developed. It is important to prevent undesirable reduction of moisture in the paste as soon as the concrete is placed. Loss of moisture at this age results in drying shrinkage and development of cracks in the paste. Two (2) principal methods or procedures for the protection and curing of concrete, namely: 1. By maintaining a moist environment by the application of water through ponding, spray, steams or saturated cover materials such as earth, sawdust, or burlap.

Care should be taken to ensure that saturated cover materials do not dry out and absorb water fall from the concrete. 2. By prevention of loss of mixing water from the concrete by means of sealing materials, such as impervious sheets of paper or plastic, or by the application of a membrane forming curing compound to the freshly placed concrete. Shrinkage and Swelling: When concrete is kept continuously damp it slowly expands, but both the total amount and rate of expansion are normally so small that the volume is considered to remain constant. Usually concrete is not kept damp, hence it is subject to water loss and shrinkage, rather than expansion. The more porous the hardened paste, the greater is the shrinkage. With the same paste, the higher paste content of the concrete, the greater the shrinkage. Drying shrinkage is a primary cause of cracking in concrete. Heat of Hydration: Excessive temperature rise is undesirable for it may impair strength and cause cracking of the concrete. Some of the measures used to control rapid temperature rise are, using a lean mix or low heat type of cement, precooling materials and using ice with mixing water. Quality Control Measures: 1. 2. 3. 4. 5. 6. 7. 8.

Selection of Materials Design of Concrete Mixtures Aggregate Production Control Concrete Production Control Control in Transporting and Placing Control of Consistency Sampling and Testing of Concrete Mixtures Curing and Protection

Selection of Materials Quality of concrete is greatly dependent on the quality of the individual ingredients.

1. Aggregates: A quality aggregate consist of particles which are free from fractures, not easily abraded, favorably graded, and not flat or elongated, with rough surface textures, and which contain no minerals that interfere with cement hydration or react with cement hydration products to cause excessive expansion. Criteria to be considered in selecting aggregates: a. Once a grading is established it should be maintained constant within rather close tolerances. b. An aggregate with unfavorable particle shape should not necessarily be rejected, if other alternatives are very costly. c. An aggregate that contains appreciable amount of organic materials which may interfere materially with the setting of cement should not be used. d. An aggregate that will not produce concrete of the required strength should not be used. If required strength can be attained with an excessive cement factor, use of the aggregate is not economical and not advisable. e. An aggregate to be used in concrete exposed to severe weathering should be essentially free of particles that are soft or friable, or highly absorptive. f. An Aggregate containing substances that could react with alkalies in the cement to cause excessive expansion should not be used in concrete exposed to wetting unless it is required that low-alkali cement is used. 2. Cement There are various types of cement for different usages; for example, highly early strength, surface resistant or low heat. Type I Portland Cement is for general use and is the type ordinarily available. Design of Concrete Mixtures To determine the proportion of the ingredients that will produce concrete of the proper workability when fresh and the desired durability and the strength after it has hardened. Factors to be considered: 1. Requirements as to placing.

2. Interrelationships of cement content, water-cement ratio, and gradation of aggregate. 3. Required strength. 4. Quality of concrete necessary to satisfy the condition of exposure. 5. Considerations of economy Aggregate Production Control: After the aggregates have been selected, there should be constant check on cleanliness and gradation during production. In stockpiling aggregate at the plant site, care should be exercised such that there is no segregation of the coarse from finer sizes.

Concrete Production Control: 1. The measuring scales should be calibrated and checked periodically. 2. The moisture content of aggregate should be determined constantly for adjustment of mix proportions. 3. Measurement of aggregate, water and cement should be checked closely. 4. Segregation in coarse aggregate should be reduced to minimum by separating the material into several size fractions and batching the fractions separately. 5. Insure thorough mixing since it is essential for the production of uniform concrete. The usual specifications such as one (1) minute for ¾ cu.m. plus one (1) minute for each additional ¾ cu.m. of capacity can be used as guide for establishing initial mixing time to be followed should be base on mixer performance. Control in Transporting and Placing: A basic requirement for placing equipment and methods is that the quality of the concrete in terms of water-cement ratio, slump, homogeneity and air content must be preserved. Concrete should be placed in horizontal layers not exceeding 60 cm. in depth, avoiding inclined layers and cold joints. For monolithic construction each concrete layer should be placed while the underlying layer is still responsive to vibration, and layers should be insufficiently shallow to permit knitting the two together by proper vibration. On sloping surface, concrete should be placed at the lower portion of the slope first, progressing upward, thereby increasing natural compaction of the concrete.

Consolidation of Concrete: Internal vibration when properly applied is the most effective method of consolidating and placing concrete. Vibrators should not be used to move concrete laterally and should be inserted and withdrawn vertically at close intervals.

Control of Consistency: The consistency of the mixtures should be checked frequently by the slump test or ball penetration. The slump test is simple, but very important, since it is an indicator of water content or water-cement ratio. An excess of water in the mixture will cause a corresponding loss of potential strength. For economy, the lowest slump which can be placed properly should always be used, because if the water-cement ratio is fixed any increase in slump increases the cement requirement.

Recommended Ranges of Slump: TYPE OF CONSTRUCTION

Slump, mm (inch) Maximum

Slabs, beams and reinforced walls Building columns Reinforced foundation walls and footings Plain footings, caissons, and substructure walls Pavements Heavy mass construction

150 (6) 150 (6) 125 (5) 100 (4) 75 (3) 75 (3)

Minimum

75 75 50 25 50 25

(3) (3) (2) (1) (2) (1)

Sampling and Testing of Concrete Mixture: The sampling requirement is to obtain a set of three (3) cylinder samples for structural concrete or a set of three (3) beam samples for paving concrete for every 75 cu.m. or fraction thereof for each class of concrete. At least one set of samples shall be obtained for each day of concreting work. Particular attention should be given to the protection and curing of molded specimen for strength tests. Due to their small volume compared to the structure,

test specimens will be more adversely affected by big temperature and will dry more rapidly and completely than the concrete in-place. Test specimens used as the basis for acceptance of concrete as delivered to the jobsite should be protected from drying and temperature rise and should be transferred to standard continuous moist curing conditions in a laboratory at the age of one day. During the transfer, they should also be protected and handled carefully. Curing and Protection: Curing is keeping the concrete moist so that hydration of the cement can continue. It is done immediately after final placement of the concrete to prevent or minimize the occurrence of plastic shrinkage cracks. The exposed surface of normal cement concrete should be kept continuously moist for atleast 7 days, 14 days will be better. Sealing compounds are generally accepted as satisfactory means of curing, particularly if preceded by wet curing. The surface to be cured should still be moist when the seal is applied.

Protection from Damage: Heavy impact on green concrete will disturbed the mass should not be permitted Floors over which construction activities are carried on should be covered. Back filling against concrete should be done only when the concrete is strong enough to carry the load, and only if performed with care to avoid impact.

Significance of Site Inspection: There is no there are defects unsound although combination of the

substitute for site quality control inspection in concrete work. If in workmanship, the concrete structure may be structurally test results are satisfactory. This may be due to one or a following:

1. Addition of water after samples have been taken 2. Delayed placing 3. Unsuitable weather conditions (rain or excessive heat)

4. Inadequate compaction 5. Inadequate curing and protection 6. Contamination of concrete mix before or during placement.

Significance of Proper Sampling and Testing: Test results on concrete samples reflect the actual of the structure. If the sampling and testing of samples is defective, test results will be unsatisfactory but the concrete may be structurally sound. This may be due to one or a combination of the following:

1. 2. 3. 4. 5. 6. 7. 8.

Incorrect sampling Inadequate compaction of sample Contamination of sample Damage to sample Inadequate curing and protection of sample Incorrect test method and procedure Inaccurate test results Mixed samples

Preparation of Grade: After the subgrade or base has been placed and compacted to the required density, the areas which will support the paving machine and the grade on which the pavement is to be constructed shall be trimmed to the proper elevation by means of a properly designed machine extending the prepared work areas compacted at least 60 cm beyond each edge of the proposed concrete pavement. If loss of density results from the trimming operations, it shall be restored by additional compaction before concrete is placed. If any traffic is allowed to use the prepared subgrade or base, the surface shall be checked and corrected immediately ahead of the placing concrete. The subgrade or base shall be uniformly moist when the concrete is placed.

Setting Forms: 1. Base Support The foundation under the forms shall ne hard and true to grade so that the form when set will be firmly in contact for its whole length and at the specified grade. Any roadbed, which at the form line is found below

established grade, shall be filled with approved granular materials to grade in lifts of three (3) cm or less, and thoroughly rerolled or tamped. Imperfections or variations above grade shall be corrected by tamping or by cutting as necessary. 2. Form Setting Forms shall be set sufficiently in advance of the point where concrete is being placed. After the forms have been set to correct grade, the grade shall be thoroughly tamped, mechanically or by hand, at both the inside and outside edges of the base of the forms. The forms shall not deviate from true line by more than one (1) cm at any point. 3. Grade and Alignment The alignment and grade elevations of the forms shall be checked and corrections made by the Contractor immediately before placing the concrete. Testing as to crown and elevation, prior to placing of concrete can be made by means of holding an approved template in a vertical position and moved backward and forward on the forms. When any form has been disturbed or any grade has become unstable, the form shall be reset and rechecked.

Mixing Concrete: The concrete may be mixed at the site of the work in a central-mix plant, or in truck mixers. The mixer shall be of an approved type and capacity. Mixing time will be measured from the time all materials, except water, are in the drum. Readymixed concrete shall be mixed and delivered in accordance with requirements of AASHTO M 157, except that the minimum required revolutions at the mixing speed for transit-mixed concrete may be reduced to not less than that recommended by the mixer manufacturer. The number of revolutions recommended by the mixer manufacturer shall be indicated on the manufacturer’s serial plate attached to the mixer. The Contractor shall furnish test data acceptable to the Engineer verifying that the make and model of the mixer will produce uniform concrete conforming to the provision of AASHTO M 157 at the reduced number of revolutions shown on the serial plate. Mixed concrete from the central mixing plant shall be transported in truck mixers, truck agitators or non-agitating truck. The time elapsed from the time water

is added to the mix until the concrete is deposited in place at the Site shall not exceed forty five (45) minutes when the concrete is hauled in non-agitating trucks, nor ninety (90) minutes when hauled in truck mixers or truck agitators, except that in hot weather or under other conditions contributing to quick hardening of the concrete, the maximum allowable time may be reduced by the Engineer.

Limitation of Mixing: No concrete shall be mixed, placed or finished when natural light is insufficient, unless an adequate and approved artificial lighting system is operated. During hot weather, the Engineer shall require that steps be taken to prevent the temperature of the mixed concrete from exceeding a maximum temperature of 320C. Concrete not in place within ninety (90) minutes from the time the ingredients were charged into the mixing drum or that has developed initial set shall not be used. Retempering of concrete or mortar which has partially hardened, that is remixing with or without additional cement, aggregate, or water, shall not be permitted.

Test Specimens: As work progresses, at least one (1) set consisting of three (3) concrete beam test specimens, 150 mm x 150mm x 525 mm shall be taken from each 330 m 2 of pavement, 230 mm depth, or fraction thereof placed each day. Test specimens shall be made under the supervision of the Engineer, and the Contractor shall provide all concrete and other facilities necessary in making the test specimens and shall protect them from damage by construction operations. Cylinder samples shall not be used as substitute for determining the adequacy of the strength of concrete. The beams shall be made, cured, and tested in accordance with AASHTO T 23 and T 97.

Joints: Joints shall be constructed of the type and dimensions, and at the locations required by the Plans or Special Provisions. All joints shall be protected from the intrusion of injurious foreign material until sealed.

1. Longitudinal Joint Deformed steel tie bars of specified length, size, spacing and materials shall be placed perpendicular to the longitudinal joints, they shall be placed by approved mechanical equipment or rigidly secured by chair or other approved supports to prevent displacement. Tie bars shall not be painted or coated with asphalt or other materials or enclosed in tubes or sleeves. When shown on the Plans and when adjacent lanes of pavement are constructed separately, steel side forms shall be used which will form a keyway along the construction joint. Tie bars, except those made of rail steel, may be bent at right angles against the form of the first lane constructed and straightened into final position before the concrete of the adjacent lane is placed. In lieu of bent tie bars, approved two-piece connectors may be used. Longitudinal formed joints shall consist of a groove or cleft, extending downward from and normal to the surface of the pavement. These joints shall be effected or formed by an approved mechanically or manually operated device to the dimensions and line indicated on the Plans while the concrete is in a plastic state. The groove or cleft shall be filled with either a premolded strip or poured material as required. The longitudinal joints shall be continuous. There shall be no gaps in either transverse or longitudinal joints at the intersection of the joints. Longitudinal sawed joints shall be cut by means of approved concrete saws to the depth, width and line shown on the Plans. Suitable guide lines or devices shall be used to assure cutting the longitudinal joint on the true line. The longitudinal joint shall be sawed before the end of the curing period of shortly thereafter and before any equipment or vehicles are allowed on the pavement. The sawed area shall be thoroughly cleaned and, if required, the joint shall immediately be filled with sealer. Longitudinal pavement insert type joints shall be formed by placing a continuous strip of plastic materials which will not react adversely with the chemical constituent of the concrete. 2. Transverse Expansion Joint

The expansion joint filler shall be continuous from form to form, shaped to subgrade and to the keyway along the form. Preformed joint filler shall be furnished in lengths equal to the pavement width or equal to the width of one lane. Damaged or repaired joint filler shall not be used. The expansion joint filler shall be held in a vertical position. An approved installing bar, or other device, shall be used if required to secure performed expansion joint filler at the proper grade and alignment during placing and finishing of the concrete. Finished joint shall not deviate more than 6 mm from a straight line. If joint fillers are assembled in sections, there shall be no offsets between adjacent units. No plugs of concrete shall be permitted anywhere within the expansion space. 3. Transverse Contraction Joint/Weakened Joint When shown on the Plans, it shall consist of planes of weakness created by forming or cutting grooves in the surface of the pavement and shall include load transfer assemblies. The depth of the weakened plane joint should at all times not be less than 50 mm, while the width should not be more than 6 mm. a. Transverse Strip Contraction Joint. It shall be formed by installing a parting strip to be left in place as shown on the Plans. b. Formed Groove. It shall be made by depressing an approved tool or device into the plastic concrete. The tool or device shall remain in place at least until the concrete has attained its initial set and shall then be removed without disturbing the adjacent concrete, unless the device is designed to remain in the joint. c. Sawed Contraction Joint. It shall be created by sawing grooves in the surface of the pavement of the width not more than 6 mm, depth should at all times not be less than 50 mm, and at the spacing and lines shown on the Plans, with an approved concrete saw. After each joint is sawed, it shall be thoroughly cleaned including the adjacent concrete surface. Sawing of the joint shall commence as soon as the concrete has hardened sufficiently to permit sawing without excessive raveling, usually 4 to 24 hours. All joints shall be sawed before uncontrolled shrinkage cracking takes place. If necessary, the sawing of any joint shall be omitted if crack occurs at or near the joint location prior to the time of sawing. Sawing shall be discounted when a

crack develops ahead of the saw. In general, all joints should be sawed in sequence. If extreme condition exist which make it impractical to prevent erratic cracking by early sawing, the contraction joint groove shall be formed prior to initial set of concrete as provided above. 4. Traverse Construction Joint It shall be constructed when there is an interruption of more than 30 minutes in the concreting operations. No transverse joint shall be constructed within 1.50 m of an expansion joint, contraction joint, or plane of weakness. If sufficient concrete has been mixed at the time of interruption to form a slab of at least 1.5 m long, the excess concrete from the last preceding joint shall be removed and disposed off as directed. 5. Load Transfer Device Dowel, when used, shall be held in position parallel to the surface and center line of the slab by a metal device that is left in the pavement. The portion of each dowel painted with one coat of lead or tar, in conformance with the requirements of the item 404, Reinforcing Steel, shall be thoroughly coated with approved bituminous materials, e.g., MC-70, or an approved lubricant, to prevent the concrete from binding to that portion of the dowel. The sleeves for dowels shall be metal designed to cover 50 mm plus or minus 5 mm, of the dowel, with a watertight closed end and with a suitable stop to hold the end of the sleeves at least 25mm from the end of the dowel. In lieu of using dowel assemblies at contraction joints, dowel may be placed in the full thickness of pavement by a mechanical device approved by the Engineer.

Final Strike-off (Consolidation and Fishing): The screed for the surface shall be at least 60 cm longer than the maximum width of the slab to be struck off. It shall be of approved design, sufficiently rigid to retain its shape, and constructed either of metal or other suitable material shod with metal.

Consolidation shall be attained by the use of suitable vibration or other approved equipment. In operation, the screed shall be moved forward on the forms with a combined longitudinal and transverse shearing motion, moving always in the direction in which the work is progressing and so manipulated that neither end is raised from the side forms during the striking off process. If necessary, this shall be repeated until the surface is of uniform texture, true to grade and cross-section, and free from porous areas.

Acceptance of Concrete: The strength level of the concrete will be considered satisfactory if the averages of all sets of three (3) consecutive strength test results equal or exceed the specified strength, fc ‘ and no individual strength test result is deficient by more than 15 % of the specified strength, fc ‘ . A set shall consist of a minimum of three (3) concrete beam specimens. Concrete deemed to be not acceptable using the above criteria maybe rejected unless the contractor can provide evidence, by means of core tests, that the quality of concrete represented by failed test results is acceptable in place. At least three (3) representative course shall be taken from each member or area of concrete in place that is considered deficient. The location of cores shall be determined by the Engineer so that there will be at least impairment of strength of the structure. The obtaining and testing of drilled cores shall be in accordance with AASHTO T 24. Concrete in the area represented by the cores will be considered adequate if the average strength of the cores is equal to at least 85% of, and if no single core is less than 75% of, the specified strength, fc ‘. If the strength of control specimens does not meet the requirements of this subsection, and it is not feasible or not advisable to obtain cores from the structure due to structural considerations, payment of the concrete will be made at an adjusted price due to strength deficiency of concrete specimens as specified hereunder: Deficiency in Strength of Concrete Specimens, Percent (%)

Percent (%) of Contract Price Allowed

Less than 5 5 to less than 10 10 to less than 15 15 to less than 20

100 80 70 60

20 to less than 25 25 or more

50 0

Figure 1. Components of a Typical JPCP

4.2 Joints Concrete slabs will crack randomly from natural actions such as shrinkage or curling. Therefore, joints are vital elements introduced into JPCPs to control cracking and horizontal movements of the slabs. Joints in JPCP include transverse contraction and construction joints, and longitudinal contraction and construction joints. Without joints, plain concrete pavements would be riddled with cracks within one or two years after placement. Even with JPCPs, incorrectly placed or poorly designed joints will result in premature cracking.

4.2.1 Joint Construction Joints are induced by saw cutting the concrete to a certain depth to force the cracks to occur at those locations (see Figure 9 for crack that has developed below the saw cut). The depth of the saw cut is limited to no more than 1/3 the thickness of the slab's depth. This one third depth saw cut is especially important over lean concrete base since it is much harder than other types of bases and creates more surface friction with the underside of the concrete slabs, which in turn can lead to more random cracking. The use of “early entry saws” is also allowed with a saw cut depth of 1/4 the slab thickness. Early entry saws are specialty saws used within the first few hours of concrete curing, and can also be efficiently used on faster curing rigid slab. Contractors can utilize a single or double saw cuts (see Standard Plan P20) for making transverse or longitudinal contraction joint.

4.2.2 Joint Types In the following, the two types of joints commonly used in JPCPs are discussed. 4.2.2.1 Transverse Joints Transverse joints are constructed at right angles to the longitudinal pavement joint in new JPCP construction as seen in Figure 2. On old previously built non-doweled rigid pavements, transverse joints were skewed. Caltrans has adopted short random patterned transverse joint spacing to reduce thermal movement at each joint and reduce the possibility of mid-panel cracking. The staggered joint spacing of 12, 15, 13 and 14 feet is utilized to reduce harmonic induced ride quality problems. According to the Caltrans HDM Index 622.4, doweled JPCP shall be used for all new state highway construction, lane widening, lane replacement, and reconstruction, especially for truck and HOV lanes. According to HDM Index 622.4, dowel bars are not required when: (1) Rigid shoulders placed or reconstructed next to a nondoweled existing concrete lane (See Standard Plan P-3) (2) Rigid shoulders placed or reconstructed next to a widened slab (See Standard Plan P-2) (3) Some individual slab replacements (see Standard Plan P-8) Because mechanical load transfer devices (dowel bars) are required in all new JPCPs, skewed transverse joints are not permitted. Dowel bars handle the load transfer and the need for skewing does not provide any significant benefit. Skewing also makes it difficult to place dowels along the transverse joint. Section 4.5 of this Guide provides additional information on load transfer across transverse joints. For lane/shoulder addition or reconstruction, when providing transverse joints, there are cases where the new joints may not line up with the existing transverse joint spacing in the adjacent lane. Standard Plan P18 shows three different cases of existing and new transverse joints alignment that can be encountered when reconstructing or adding concrete lane/shoulder adjacent to existing concrete pavement. To prevent translation of the existing transverse joints over to the new and weaker transverse joints, longitudinal isolation joints (see Section 4.3.1 for this topic) are provided.

Figure 2. Transverse Joints Perpendicular to Lane Lines and Longitudinal Joints 4.2.2.2. Longitudinal Joints Longitudinal joints (see Figure 3) are necessary to control cracking in the longitudinal direction where two or more lane widths are placed at one time. They are constructed at lane lines, typically in multiples of 12 feet. Tie bars (see Section 4.4) are placed at these joints to hold two abutting rigid pavement faces in contact.

Figure 3. Longitudinal Joint at Lane Line

4.3 Other Joints 4.3.1 Isolation Joint An isolation joint is a special longitudinal joint that is placed to prevent existing transverse joints or transverse working joints (joints that accommodate movements) from extending into the weaker newly placed rigid pavement. Isolation joints should be used when matching the existing transverse joints is not practical. They are placed to separate dissimilar rigid pavements/structures in order to reduce compressive stresses that could cause uncontrolled cracking. An isolation joint is required in (1) lane/shoulder addition or reconstruction where transverse joints do not align between new and existing, for which tie bars are required at the isolation joint, (2) interior lane replacement where joints do not align between new and existing, and (3) lane/shoulder addition or reconstruction where transverse joints align between new and existing, where tie bars are not required for the isolation joint. When adding the new lane, in many instances, an asphalt shoulder is removed. This may leave the abutting edge of concrete slab surface rough that will require saw cutting to remove any protruding pockets of concrete. This sawing requirement is covered in SSP 40-010. The isolation joint prevents the joints and cracks in the adjacent lane from propagating to the new added lane. A joint filler material is used to fill the isolation joint to prevent infiltration of incompressible materials. The filler material should be continuous from one edge of the slab to the other. The top of the filler material should be recessed below the surface of the slab to allow space for joint sealant application. 4.3.2 Construction Joint A construction joint is either (1) a transverse joint that joins together two consecutive slabs constructed at two different times, or (2) a longitudinal joint that joins two lanes that are paved in two separate passes. For nondowelled JPCPs (when permitted), tie bars are usually used to connect the two adjoining slabs together so as to act as one slab. It is important to have an adequate slab section to tie into as shown on the plans. Construction joint for doweled pavement shall coincide with the new joint spacing.

4.4 Tie Bars Tie bars are typically used at longitudinal joints (see Figure 4) and transverse construction joint in a nondoweled shoulder addition/reconstruction (see Standard Plan P-3) to hold tight the faces of abutting concrete in contact.

Figure 4. Tie Bars in a Longitudinal Joint Tie bars used in JPCP construction are 30-inch long Grade 60 No. 6 deformed steel bars, placed in the mid depth of the JPCP slab, perpendicular to the longitudinal construction and contraction joints. Tie bars are placed a minimum of 15 inches from transverse joint location in between slabs and at 18-inch spacing thereafter. The use of epoxy-coated tie bars is not necessary for JPCP, except in areas where corrosion is known to be a problem (e.g., because of the presence of salts or the application of de-icing salts). In California, tie bars are epoxy-coated as specified under SSP 40-010 and in conformance with Section 52-1.02B, “Epoxy-coated Reinforcement” in the Standard Specification. There is a limit of 50 ft wide tied JPCP lanes, based on national experience. When more lanes are tied together, there seems to be a tendency for the concrete slab to crack longitudinally. When the slabs are tied together they act as one slab and the friction between the base and the slabs is high enough to restrain movement, thus causing cracking in some cases. Therefore, tie bars should be omitted at one of the longitudinal joints when more than 4 lanes (or 3 lanes and a shoulder) are being tied together. The preferred longitudinal joint to omit tie bars would be an inside lane where truck or bus traffic will not occur. Standard Plan P18 includes lane schematics that cover most cases for isolation joint placement. Tie bars are recommended at longitudinal construction joints for lane/shoulder addition or reconstruction, but not recommended where isolation joints are required. Dowel bars (see below) at longitudinal joints without tie bars may be useful when there is a need to obtain some limited load transfer across the longitudinal joint. Standard Plan P-18 provides schematics on when and how to apply contact joints, isolation joints, and when to use dowel bars in lieu of tie bars.

4.5 Load Transfer Load transfer is the ability of a joint to transfer a portion of an applied load (the truck wheel) from one side of the joint to the other. Joint transfer is achieved by (1) mechanical load transfer devices such as dowel bars, (2) aggregate interlock across abutting edges of concrete, and (3) friction between concrete and stabilized base [lean concrete base, hot mixed asphalt, asphalt treated base, cement treated base, etc.]. The ideal transverse joint is one that has all three mechanisms available. The current Caltrans standard practice utilizes lean concrete or hot mixed asphalt as the base, dowel bars, and aggregate interlock. In the following a brief discussion of each mechanism is provided. 4.5.1 Dowel Bars Dowel bars are made of smooth, round, epoxy-coated Grade 60 steel bars that allow load transfer across the joint without restricting horizontal movement (see Figure 5). Dowel bars provide lower deflection, prevent pumping, corner breaks, and excessive slab curling and reduce the potential for faulting; thus keeping a smooth-riding pavement. Slab movements (rocking) are significantly reduced with the use of dowel bars as schematically seen in Figures 6 and 7 for dowelled and non-dowelled transverse joints. Generally, the number of dowel bars required along the transverse joint is dictated by the width of the slab.

Figure 5. Dowel Bars in a Transverse Joint

Figure 6. Slab Movements in Doweled Slab

Figure 7. Slab Movements in Non-doweled Slab Dowel bars also limit slab curling over time. Slab curling is defined as when the edges of the slab curl up or down as the temperature changes throughout the day and night causing rougher pavement profile and increased stresses on the edges of the concrete slabs, which accelerates spalling and cracking of the slab. Slab curling is caused by the temperature difference between the top and bottom of the concrete slab. Because the underside is insulated from temperature changes, the surface expands and contracts at a different rate compared to that of the underside of the slab. This causes the slab to become larger on the surface than the underside during the day resulting in the slab curling down on the edges as shown in Figure 8 (top drawing). At night, the process reverses and the surface shrinks compared to the underside causing the slab to curl up at the edges as shown in Figure 8 (bottom drawing). Warping is defined as the moisture fluctuations throughout the depth of the slab. Due to warping, slabs deform in the same manner as with curling as affected by the degree of moisture saturation, as shown in Figure 8. Again, dowel bars help prevent excessive warping and curling that can develop due to these moisture fluctuation and temperature differentials, thus keeping the pavement smoother (flatter).

Figure 8. Slab Curling and Warping Concept

4.5.2 Aggregate Interlock Aggregate interlock is the interlocking action between exposed aggregate particles in the opposing joint faces beneath the sawn joint (see Figure 9).

Figure 9. Aggregate Interlock Across Transverse Joint

For non-doweled JPCP, aggregate interlock (jagged crack area) beneath the saw cut portion of the joint provides most of the load transfer. Over time these aggregate interlock faces can wear and load transfer can drop. Because aggregate interlock deteriorates over time, especially when there are no dowel bars and/or stabilized base, Caltrans current practice requires dowel bars in all but a limited number of cases. Where truck volumes are low, there are standard designs available that do not require the stabilized base. 4.5.3 Stabilized Base Stabilized bases utilize a small percentage of cement or asphalt binder to stiffen the base, and can provide friction with the concrete slabs resting on them; thus helping in transferring the load from one side of the joint to the other. Historically, Caltrans used stabilized base (primarily cement treated base) with its pavements, which were non-doweled. Experience, however, has shown that these pavements fault prematurely requiring increased maintenance and earlier rehabilitation. Current design practice requires both dowel bars and stabilized base for pavements subject to high truck volumes. Because pavements with dowel bars have shown to be more cost effective and provide better performance than no-doweled pavements, current design practice for low volume routes still requires dowel bars but does provide designs that do not require a stabilized base.

4.6 Subgrade, Subbase and Base Rigid pavements require base and, in some cases, subbase layer for structural support since the applied traffic loads is transferred across the rigid structure by providing only bearing stress applied to the underlying foundation. Base and subbase provide a working platform during construction. The majority of rigid pavements fail not because of concrete slab failure but by failure of materials below the concrete slab due to unstable or non-uniform materials, poor compaction, or poor drainage (e.g., either underground water percolating into the base or surface water leaching through the concrete and becoming trapped in the base). 4.6.1 Subgrade The load-bearing capacity of the subgrade soil has a significant impact on the performance of a JPCP. Anything that can be done to increase the load-bearing capacity or structural support of the subgrade will likely improve the overall strength and performance of the pavement. Generally, greater subgrade structural capacity can result in more economical pavement structures. The subgrade is the natural ground, graded and compacted, on which the pavement is built. Preparation of the subgrade includes:

1. Compacting soils at moisture contents and densities that will ensure uniform and stable pavement support. 2. Whenever possible, setting gradelines high enough and making side ditches deep enough to increase the distance between water table and pavement. 3. Crosshauling and mixing of soils to achieve uniform conditions in areas where there are abrupt horizontal changes in soil type. 4. Using selective grading in cut and fill areas to place the better soils nearer to the top of the final subgrade elevation 5. Improving extremely poor soils by treatment with or lime, or importing better soils, whichever is more economical.

Subgrade soil can vary widely over a short distance. Poor subgrade can be described as expansive (plasticity index greater than 12 and/or R-value of less than 10). Index 614.2 in the HDM states that organic and peat soils are compressible and not recommended for roadway construction. They should be removed, wherever possible, prior to placing the pavement structure. Subgrade stabilization is desirable for poor subgrade material under a rigid pavement. For example, lime may be used with expansive soils, cement with less plastic soils (plasticity index less than 10), and emulsified asphalt can be used with sandy soils. The binding characteristics of these materials generally increase the subgrade load bearing capacity. To eliminate or reduce subgrade moisture, installation of subdrains is necessary. Topic 614 in the HDM explains soil characteristics, testing, and available treatment options. Where subgrade conditions are not reasonably uniform, corrections is most economically and effectively achieved by proper subgrade preparation techniques, such as selective grading, crosshauling mixing at abrupt transitions, and moisture –density control of subgrade compaction. Particular attention is needed for the control of expansive soils and excessive differential frost heave. EXPANSIVE SOILS Excessive differential shrink and swell of expansive soils cause non-uniform subgrade support. As a result, concrete pavements may become distorted enough to impair riding quality. Several conditions can lead to pavement distortion and warping: 1.If expansive soils are compacted when too dry or are allowed to dry out prior to paving, subsequent expansion may cause high joints and loss of crown. 2. when concrete pavements are placed on expansive soils with widely varying moisture contents, subsequent shrink and swell may cause bumps, depressions, or waves on the pavement. 3. Similar waves may occur where there are abrupt changes in the volume-e

Experience has reveals that the volume changes of clays with a medium or low degree of expansion with a plasticity index of 15-28 and shrinkage limit of 10-16, and plasticity of less than 18 and shrinkage limit of 15, respectively has usually cause no problems for concrete pavements. Most soils sufficiently expansive to cause pavement distortion are in the AASHTO A-6 or A-7 groups. CONTROL OF EXPANSIVE SOILS The amount of volume change that will occur with a given expansive soil depends on several factors: 1. Climate- degree of moisture change that will take place in the subgrade throughout the year or from year to year. It is generally true that placement of a pavement will reduce the degree of moisture change in the underlying subgrade. 2. Load conditions- surcharge effect of the weight of soil, subbase, and pavement above the expansive soil. 3. Moisture and density conditions of the expansive subgrade at the time of paving. Knowledge of the enterrelationship of these factors leads to the selection of economical control methods. Subgrade Grading Operations- Test indicate that soil swell can be reduced by surcharge loads. Field measurements show that excessive swell at depths of 1 to 2 ft gradually decreases to a negligible amount at depths of 15 ft or more. Thus, excessive swell can be controlled by placing the more expansive soils in the lower part of the embankments and crosshauling less expansive soils for the upper part of the subgrade in both embankments and excavations. Selective grading and mixing of soils provide reasonably uniform conditions in the upper part of the subgrade and gradual transitions between soils with varying volume change properties. These operations are also used at cut-fill transitions to correct abrupt changes in soil type. In deep-cut sections of highly expansive soils, considerable expansion may occur due to the removal of the natural surcharge load and the consequent absorption of additional moisture. Since this expansion takes place slowly, it is essential to excavate these deep cuts well in advance of other grading work. Compaction and Moisture Control- Volume changes are further reduced by adequate moisture and density controls during compaction. To reduce volume changes, it is critical to compact highly expansive soils at 1 to 3 percent above optimum moisture, AASHTO T99. Where embankments are considerable height,

compaction moisture contents can be increased from slightly below optimum in the lower part of the embankment to above optimum in the top 1 to 3 ft. Research verifies that expansion is greatly reduced for most plastic soils when compacted at moisture contents exceeding AASHTO T99 optimum. Reseach also shows the strong influen

4.6.2 Subbase Layer The subbase layer is a planned thickness of specified material that is placed on the subgrade or under the basement material. This layer is not always used, but when it is needed it can provide for structural strength and/or a working platform. The essential function of a subbases is to prevent mud-pumping of fined-grained soils .A subbase layer is mandatory under the combination of soils, water, and traffic that is conducive to mud-pumping. Such conditions frequently exist in the design situation for major, heavily travelled pavements. Mud pumping is the forceful displacement of a mixture of soil and water that occurs under slab joints, cracks and pavement edges. Mud pumping can occur when concrete pavements are placed directly on finegrained, plastic soils and erodible subbases. Mud pumping necessary to occur due to following 1. Subgrade soil that will go into suspension 2. Free water between pavement and subgrade or subbase. 3. Frequent passage of heavy axle loads.

The other function of subbase is use as secondary, it aid in controlling of volume changes for severe conditions of high-volume subgrades. It also aid in reducing excessive differential frost heave. It provide drainage layer and a more stable working flat form for pavement construction.

4.6.3 Base Layer The base layer is immediately placed beneath the surface course. It can be treated (stabilized, bound) or untreated (unbound, unstabilized). It can provide a stable platform for the concrete paving, provides for additional load distribution, and contributes to drainage (if permeable base is used) and frost resistance. The primary purpose of the unbound aggregate or granular material is for structural support, but other uses include (1) improve drainage,

(2) minimize frost action damage and (3) minimize intrusion of fines from the subgrade into the pavement structure. Base courses constructed of stone fragments, slag and soil-aggregate mixture lie close to the surface; hence, they must posses high resistance to deformation in order to withstand the high pressure imposed upon them. The functions of a base course are prevention of pumping, drainage ,prevention of volume change of sub-grade, increased structural capacity and expedition of construction. Stabilized bases are the standard for all JPCPs with a Traffic Index (TI) greater than 11. For lower TI values, unstabilized aggregate base maybe used. The Department uses stabilized bases to provide a construction platform for the concrete paving machine and to minimize base erosion and the development of voids underneath the concrete slabs. Current standard designs use either lean concrete base or Hot Mix Asphalt–Type A (HMA-A). 3. BASE COURSE MIXTURE PREPARATION Base course Class A is a layer composed of coarse aggregate, fine aggregate and fines, i.e. material finer than 75 μm. The coarse aggregate fraction is material retained on the 4.75 mm sieve and is required to consist of hard, durable particles or fragments of crushed rock or gravel; the fine aggregate fraction is material passing the 4.75 mm sieve and retained on sieve No. 200 and consists of natural or crushed sand and fine mineral particles. Table 2. Class “A” Base Course Gradation

Figure 3. SNI Specification for Base Course Class A In this investigation, the coarse and fine aggregate used in the preparation of samples was 100% crushed rock; for the fines (material passing No. 200), materials having different Plasticity Index values were used. Crushed rock fines (Banjaran provided material having 0% Plasticity Index). As discussed before that materials having a PI values in the range of 6% 25% were obtained after sampling and characterizing samples from nine locations. Samples of base course Class A were prepared based on the median of the SNI specification as shown on Table 2 and Figure3. Mixed were prepared with 0%, 4%, 8%, 12% and 16% material passing sieve No. 200, i.e. finer than 75 μm. The gradations obtained are shown in Figure 4. A total of 15 mixture types were investigated, i.e. 5 fines contents and 3 values of Plasticity Index. Mixes are labeled as A, B and C in order of increasing Plasticity Index and 1 to 5 in order of increasing fines content.

Figure 4. Particle Size Distribution of Grading Investigated 4. RESULTS AND DISCUSSIONS One objective of the investigation was to determine the effect of the plasticity of the fines on the strength and permeability characteristics of unbound road-base Class A. Because of time constraints only three values of plasticity were investigated, i.e. soil with a PI value of 0% and 2 others in the range of 6 to 25%. Soil was sampled at a number of locations in Kabupaten Bandung (Bandung Municipality) and soils with the appropriate plasticity values were selected for the investigation. The tests were done in the Highway Laboratory and Soil Mechanics Laboratory of Bandung Institute of Technology. 4.1 Properties of Natural Soils The soil property of particular interest was the Plasticity Index, montmorillonite content was also determined on selected soils to avoid soils that have a high swelling potential. To determine the montmorillonite content, the methylene blue test was performed (done outside of Bandung Institute of Technology and helped by Material and Chemical Laboratory of the Department of Energy and Mineralogy Resources). After field investigations at nine locations, the Plasticity Index of the soil at the nine locations and the montmorillonite content of the soil at 4 locations were determined and the results are shown on Table 3 and Table 4.

The main criterion for soil selection was PI and the objective was to select 2 soils with widely different PI values but with acceptable montmorillonite content. Based on the Plasticity Chart developed by Casagrande, Cimareme soil is classified as an inorganic clay of medium plasticity and the Cipakem sol is classified as an inorganic clay of high plasticity and according the activity, soils from Cimareme and Cipakem are inactive clays.

4.2 Classification of the Aggregate Mixtures The grading curve of the mixtures investigated are shown in Figure 4 and the grading investigated are summarized in Table 5, again the number of 1 to 5 are represented the fine content of 0%, 4%, 8%, 12% and 16%. Classification of the mixtures investigated on the basis of the AASHTO system is given in Table 6.

SNI specifies that the Plasticity Index of the aggregate base course should not exceed 6%. Based on the Atterberg limits test results, value of Plasticity Index determine for mixtures Type B4, B5, C3, C4 and C5 are 6.35%, 7.23%, 6.31%, 9.20% and 12.64% respectively. These values exceed the maximum value of PI, the other mixtures are acceptable.

Figure 5. Effect of Quantity and Type of Fines on the Plasticity Index.

The results of the LL test gave values for mixtures Type B4, B5, C4 and C5 of 25%, 25.5%, 28% and 30% respectively. These exceed of the maximum value of 25% specified by standard but the other mixtures satisfy this requirement.

Figure 6. Effect of Quantity and Type of Fines on the Specific Gravity of the Combined Aggregate Fractions in the Mixtures 4.3 Compaction Test The maximum dry density of each mixture at the optimum water content was determined using the modified ASHTO compaction procedure. Material was compacted in the 6 in. diameter mold in five approximately equal layers to give a total compacted depth of about 5 in. Each layer was compacted by 56 uniformly distributed blows of a 10-lb hammer dropping freely from a height of 18 in. The influence of the fines content on the maximum dry density is shown on Figure 7 for mixture containing fines Type A, B and C,

Figure 7. Results of Modified Compaction Test on Unbound Aggregate Base The modified compaction test results shown in Figure 7 show that maximum dry density of aggregate base mixture Type A, i.e. material with non-plastic crushed stone fines, increases up to 8% fines content and then decreases with increased amount of fines. For mixtures containing plastic fines, mixtures Type B and C, maximum dry density is obtained at a fines content of 4%. At this fines content the maximum dry densities for mixtures Type A and Type C (high PI) are almost identical; the highest dry density is achieved by mixture B (medium PI). As fines content is increased above 4%, maximum dry density reduces. In the case of the mixture containing fines of high plasticity the reduction is most evident when of the mixture containing fines of medium plasticity, increasing the fines from 12% to 16% causes the most significant reduction in the maximum dry density. 4.4 CBR Test This test is used in determining the bearing capacity of unbound pavement layers. The test is useful for evaluating sub-grade soil, sub-base and road-base course material containing only a small amount of material retained on the 19.0 mm sieve. Samples of soil-aggregate mixture for the CBR test were prepared at optimum moisture content and soaked for 9 hours before the test was carried out. The influence of fines content on the

maximum dry density is shown on Figure 7 for mixtures containing fins type A, B and C. In all cases, the CBR value at 0.2” penetration exceeded the value at 0.1” penetration. The influence of the fines content on the soaked CBR value of the samples compacted at maximum density is shown on Figure 8.

Figure 8. Results of California Bearing Ratio Test on Unbound Aggregate Base Variation in soaked CBR with fines content follows a similar pattern to tat observed for maximum dry density. In the case of mixture Type A (nonplastic fines) the CBR value peaks at a fines content of 8%; in the case of mixtures Type B and C (medium and high plasticity fines, respectively) maximum CBR is achieved at a fines content of 5%. A minimum soaked CBR value of 80% is specified by standard and the mixture with 0% fines content does not meet this specification. The mixtures with non-plastic fines meet the specification up to a fines content of 16%, the maximum fines content investigated. The mixture with fines of medium plasticity meets the specification at fines contents of 4% and 8% while the mixture containing highly plastic fines just meets the specification at a fines content of 4%. The CBR of the mixture with highly plastic fines reduces very significantly as fines content is increased to 16%. 4.5 Permeability Test The permeability of a soil is a measure of its capacity to allow the passage of fluid through the soil. Procedure for the measurement of the permeability of a soil in the laboratory are of two types, Constant Head and Falling Head Tests. In this investigation the falling head method was used.

Preparation of samples used the modified compaction procedure. The diameter of the mold was 6 in. and the sample was compacted in 5 approximately equal layers by applying 56 uniformly distributed blows of a 4.54 kg hammer dropping freely from a height of a 8 in. to each layer.

The degree of permeability of Type A material (non-plastic fines) is classified as medium over the range of fines contents investigated and has a good drainage characteristics. Type B material (medium plastic fines) is also indicated to have a medium degree of permeability and good drainage characteristics over the range in fines content investigated. However at fines content of 12% and 16%, drainage characteristics are close to the boundary between good and poor. In the case of Type C material (highly plastic fines), the drainage characteristics of material containing 4% and 8% fines can be described as good although material with 8% fines is close to the boundary between good and poor. Material with 12% fines is on the boundary between good and poor while the drainage characteristics of material containing 16% fines fall into the poor category. Looking at the criteria for classification of permeability, all of the Type A materials and material Type B1 can be classified as having medium permeability; material Types B2, B3 and B4 and Type C1, C2 and C3 have low permeability and Type C4 is on the borderline between low and very low. Selection of the mixture should consider minimum soaked CBR value. However if the coefficient of permeability is also a criterion, mixture Type C2 with 4% of highly plastic fines and mixtures Type B2 and B3 with 4% and 8% medium plasticity fines are also acceptable.

Figure 9. Results of Permeability Test on Unbound Aggregate Base

5. CONCLUSIONS In this investigation, mixture of aggregate base Class A containing 0, 4, 8, 12 and 16% fines were investigated. The fines were of 3 type, i.e. nonplastic fines and fines with PI values of 9.47% (medium plasticity) and 24.09% (high plasticity). The conclusions reached are summarized as follows: a. Mixture containing 12% and 16% medium plasticity fines and 8%, 12% and 1% high plasticity fines have values of PI that exceed the 6% maximum specified by Indonesian standard. b. The maximum LL value of 25% specified by the Indonesian standard is exceeded by the mixture containing 16% medium plasticity fines and 12% and 16% high plasticity fines. c. A peak value of maximum dry density is evident as the fines content of the mixture is increased. In the case of the mixture containing non-plastic fines, maximum dry density has a peak value at 8% fines content. In the case of mixtures containing plastic fines, maximum dry density peaks at a fines content of 4%. d. The variation in soaked CBR with increase in fines content follows a pattern similar to that observed for maximum dry density. Mixture containing

non-plastic fines has a peak CBR value at 8% fines, the CBR of mixtures containing plastic fines peaks at 4% fines. e. The introduction of 4% fines to the mixture causes a very significant reduction in the permeability; there is a less dramatic reduction in permeability with further increase in the amount of fines. At any fines is considerably more permeable than the mixture made with plastic fines. Lean concrete base (LCB) is the typical type of base for JPCP primarily because it not only provides a stable platform for the rigid slab but is also constructed using the same plants and equipment as concrete. Lean concrete base is more rigid and less erodible than cement treated base (CTB). The September 1, 2006 Caltrans HDM edition (June 26, 2006 Metric edition) states that concrete can be substituted for LCB when justified for constructability or traffic handling. JPCP should not be bonded with LCB. A 1-inch thick interlayer of HMA-A should be placed between the JPCP and LCB. Hot Mix Asphalt–A (HMA-A) is another alternative to lean concrete base. It provides a smooth base layer, reduces friction, and provides a good bond breaker layer. HMA-A base layer consists of a combination of mineral aggregates and asphalt materials mixed mechanically in a plant. HMA-A provides flexibility to expand and contract with temperature fluctuations. HMA-A typically performs better than LCB in hotter climate regions like the desert environments and southern central valley because it provides more flexibility for concrete to expand and contract with temperature fluctuation. Asphalt Treated Permeable Bases (ATPB) has been used in the past to address water infiltration. This type of permeable base is useful where it is necessary to drain water beneath the pavement (see Figure 10). Water can enter the pavement as surface water through cracks, joints, and pavement infiltration. Saturation of the pavement or underlying subgrade, or both, generally results in a decrease in strength or ability to support heavy axle loads. Treated permeable base requires the use of edge drains or some other method of draining water out and away from the pavement. Otherwise, the collected water will become trapped. Trapping water beneath the concrete could create an undesirable condition known as pumping. Pumping removes fines from the saturated base layer (especially untreated ones) by creating dynamic upward and downward movements due to wheel loads at joints and cracks. This pumping action develops voids under the concrete slabs that eventually lead to faulting and premature cracking. It should be noted that if the edge drains are not maintained in good operating condition, entrapped water will create conditions that are typically worse than if no permeable base was provided. For these reasons, treated permeable bases are not recommended if edge drains could not be maintained, except where there is an existing treated permeable base that needs to be propagated for drainage purposes.

Figure 10. Difference Between Dense Graded (left) and Permeable (right) Bases One might consider an ATPB layer for low truck traffic locations if adequate low maintenance drainage is to be included in the design. If ATPB is desired in these locations, the designer should make sure that edge drains or other drainage systems can be maintained by field maintenance crews and should even include the costs to maintain drains in the report (separate from the construction cost estimate) so maintenance can pursue the resources and equipment needed to maintain the pavement drainage. Stripping (water washing away cement paste, binders, and fines) can be an issue for stabilized bases if care is not taken to specify materials that will not strip in the presence of water. As a precautionary measure, the Department no longer uses cement treated base (CTB) or cement treated permeable base (CTPB) as a base in JPCP construction. LCB is more tolerant to moisture and less susceptible to pumping and stripping so it should be used in lieu of CTB when widening next to a CTB layer. ATPB should be used in lieu of CTPB when widening next to an existing CTPB layer.