Report Of Aggregate .docx

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INTRODUCTION OF COARSE AGGREGATE Aggregates defined as inert, granular, and inorganic materials which are consist of stone and solid stone-like solid. Aggregates also commonly considered as inert because it accounted for 60 to 80 percent of the volume and 70 to 85 of the weight of concrete. Therefore, it is necessary to emphasis the properties of the aggregates including strength, density, durability, shrinkage, creep and thermal properties of the concrete. The compressive aggregate strength is the most important among them to select the aggregates.To obtain a quality concrete mix, the aggregate has to be clean, hard, free from absorbed chemicals, no presence of clay or fine materials that could cause the deterioration of concrete. Aggregates can be classified as two different types, coarse and fine. Coarse aggregates usually greater than 4.75mm where it retained on a No.4 sieve, while fine aggregate is less than 4.75mm passing through the No.4 sieve. Coarse aggregates which are consist of uncrushed gravel or stone are the product of natural disintegration. Most of the natural aggregates are obtained from the bed rock. Coarse aggregates are categorised into two groups which are single-size aggregate and graded aggregate. A singlesize aggregate usually based on the nominal size specification. It contains about 85 to 100 percent of material which passes through that specified size of the sieve and zero to 25 percent of which retained in the next lower sieve. Meanwhile the graded aggregate consists of more than one single-size aggregate. The size of the coarse aggregate will affect the strength and workability of the concrete. Reduction of cement content, water requirement and the reduction of cement of drying shrinkage will affected by a larger size of coarse aggregate. Other physical properties of aggregate must be known before mixing concrete to obtain desirable mixture. These are including shape and texture, size gradation, moisture content,specific gravity, reactivity, soundness and bulk unit weight. For the shape and texture of aggregate, it will affect the properties of fresh concrete rather than hardened concrete. This is because workability of mixture is influenced by smooth, flat or elongated particles that requiring more water to get a workable concrete. Thus, concrete is more workable when smooth and rounded aggregate is used instead of rough angular or elongated aggregate. Example of excellent aggregates which are the natural sands and gravel can be

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obtained.from riverbeds or seashores. In this, crushed stone will produce much more angular and elongated aggregates which it has a higher surface to volume ratio, better bond characteristics but require more cement paste to produce a workable mixture. In an addition, the cement content must also be increased to maintain the water-cement ratio. With this, flat and elongated particles can be avoided or limited to about 15 percent by weight of the total aggregate. Unit-weight measures the volume that graded aggregate and the voids between them will occupy in concrete. The void content between particles affects the amount of cement paste that requires for the mix meanwhile an angular aggregate increase the void content. So, larger sizes of well-graded aggregate and improved grading will decrease the void content. Besides, absorption and surface moisture of aggregate are measured when selecting aggregate because the internal structures of aggregate is made up of solid material so that voids may not contain water. The amount of water in the concrete mixture must be adjusted so that it included the moisture condition of aggregate. The grading or size distribution of aggregate is an important characteristic because it determines the paste requirement for workable concrete. Grading limits and maximum size are specified because these properties affect the amount of aggregate used as well as cement and water requirements, workability,pumpability, and durability of concrete. Therefore, when the water-cement ratio is correct, a wide range in grading can be used without a major effect on strength. Certain particle sizes of aggregate are omitted from the size when the gap-graded aggregate is specified. Gap-graded aggregate are used to obtain uniform textures in exposed aggregate concrete, thus, close control of mixture proportions is necessary to avoid segregation.

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OBJECTIVE To determine the physical properties of coarse aggregate required in mix design.

APPARATUS 1. Sieving pan ranging size from: a. 37.50mm b. 20.00mm c. 14.00mm d. 10.00mm e. 6.30mm f. 5.00mm g. 3.35mm h. pan 2. Weighing scale 3. 3000g of coarse aggregate 4. Oven 5. Wire mesh bucket 6. Drying cloth 7. Tray

PROCEDURE A. Sieve Analysis 1. A sample weighed 3000g of coarse aggregate was obtained from the lab. 2. The sieving pans were obtained as required sizes and cleaned.

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3. The weight of the empty sieving pans was recorded by weighing scale. 4. The sieving pans then were stacked according to the size from the pan to 3.35mm opening to the largest opening, 37.50mm, and then placed on the sieve shaker machine. 5. The aggregate sample was poured into the top sieving pan gently. 6. The screw to hold the sieving pan was tighten and the sieve shaker machine was turned on for 5 minutes. Ensure that the holding screw is tight to avoid from the sieving machine fall. 7. Each of the pan with the samples in were weighed and the data was recorded in a table. 8. The graph of sieve analysis was plotted according to the data obtained.

B. Specific Gravity and Absorption 1. A sample weighed 3000g of coarse aggregate was obtained from the lab. 2. The sample was washed to remove any impurities. 3. The sample then was dry in the oven for 24 hours at 105°C. 4. The sample then was immersed for 24 hours in water and weighed. 5. A piece of cloth was used to dry off the surface of the sample. Precaution steps was taken to avoid evaporation of water inside the sample. 6. The required sample was weighed to obtain its saturated surface dry (SSD) condition and noted as B. 7. The SSD sample was weighed in water and noted as C. 8. The sample then was dried to constant weight at a temperature 110 ± 5°C and let cooled in room temperature until it was comfortable to handle. 9. The sample was weighed and recorded as A. 10. The specific gravity was calculated by using the formula given: a. Bulk specific Gravity W OD A i. B.S.G (OD) = = B−C W SSD−W ¿ W SSD B ii. B.S.G (SSD) = = B−C W SSD−W ¿ b. Apparent Specific Gravity W OD A i. A.S.G = = A−C W OD−W ¿ Where: A=weight of the oven-dry sample in air (g) B=weight of the SSD sample in air (g)

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C=weight of the saturated sample in water (g) 11. The absorption percentage was calculated based on the following formula: W SSD−W B−A ×100 = ×100 a. Absorption percentage (%) = A W OD OD

DATA X Total Weight of Sample = 3000g.

Retained Sieve

Sieve +

Pass Percentage

Size

Sieve

Aggregate

(mm)

(g)

(g)

37.50 20.00 14.00 10.00 6.30 5.00

1584.0 1507.5 1362.0 1339.5 1286.5 1260.5

Cumulative

1584.0 2041.5 2593.5 2079.0 1661.0 1327.0

(%) Retained

Retained

Cumulative

Cumulative

Weight

Percentage

Weight

Percentage

(g) 0.0 534.0 1231.5 739.5 374.5 66.5

(%) 0.0 17.8 41.1 24.7 12.5 2.2

(g) 0.0 534.0 1765.5 2505.0 2879.5 2946.0

(%) 0.0 17.8 58.9 83.5 96.0 98.2

100.0 82.2 41.2 16.5 4.0 1.8

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3.35 pan

1319.5 767.0

1362.5 778.0

43.0 11.0

1.4 0.4

2989.0 3000.0

99.6 100.0

Figure C2-1 Table of sieve analysis. a. Bulk specific Gravity

W OD A = B−C W SSD−W ¿ W SSD B ii. B.S.G (SSD) = = B−C W SSD−W ¿ b. Apparent Specific Gravity W OD A i. A.S.G = = A−C W OD−W ¿ i. B.S.G (OD) =

Where: A=weight of the oven-dry sample in air (g) B=weight of the SSD sample in air (g) C=weight of the saturated sample in water (g) 2. The absorption percentage was calculated based on the following formula: W SSD−W B−A ×100 = ×100 a. Absorption percentage (%) = A W OD OD

CALCULATION a) Bulk Specific Gravity

2992 =2.65 2992−1816.7 2944.1 =2.61 (ii)B.S.G (SSD) = 2.9441−1816.7 b) Apparent Specific Gravity 2992 (i) = 2.55 2992−1816.7 (i) B.S.G (OD) =

0.4 0.0

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GRAPH

120

Passing Percentage (%)

100

80

60

Experi ment Bri tis h Sta nda rd Upper Li mi t Bri tis h Sta nda rd Lower Li mi t

40

20

0

0

5

10

15

20

25

Sieve Size (mm)

30

35

40

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Figure C2-2 Graph of Sieve Analysis.

DISCUSSION A. Sieve Analysis Based on the data recorded as shown in Figure C2-1, the most sample trapped in sieve pan is 14.00mm in size with 41.1% followed by size 10.00mm with 24.7% of sample retained. While the least amount is sample with size 37.5mm with 0% of sample retained. Thus, we had concluded that the we had obtained the sample of coarse aggregate size range of 14.00mm to 10.00mm. Aggregate that has size of more than 5mm in diameter is categories as coarse aggregate. After analyzing our result, we found that 98.3% of our sample is coarse aggregate. The other 1.7% of the sample was below 5mm in diameter which could not categories as coarse aggregate. From the graph shown in Figure C2-2, our sample follows the British Standard grading which it is in between the upper and lower limit passing sieve. During this experiment in progress, some error had been taken such as zero error when using the weighing scale. Another error that we had encountered was some of sample may had lost during the sieving process.

B. Specific Gravity and Saturation The value of bulk specific gravity that we obtained from this experiment is 2.65. The apparent specific capacity calculated is 2.61. The absorption capacity or percentage of saturation we obtained is 2.55.

CONCLUSION Based on the experiment we conducted, the highest percentage of aggregate trapped sized 14.00mm at 41.1%. On the other hand, 2.65 is the bulk specific gravity for the sample and the

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apparent specific gravity is 2.61. The percentage of saturation is 2.55 %. Aggregates physical and characteristic properties may affect on concrete mix properties. By conducting the experiment, the grading of aggregate can be determined. Its specific gravity is also calculated to obtain the weight to volume relationships. In order to mix a good concrete, aggregate must me examined properly as it is one of important material in the mix.

REFERENCES 1. Portland Cement Association. (2018). Cement and Concrete Application. 2. Retrieved from https://www.cement.org/cement-concrete-applications/concrete-materials/aggregates 3. Suryakanta. (2014). Clariffy Aggregates According to Size. 4. Retrieved from https://civilblog.org/2014/07/07/how-to-classify-aggregates-according-to-size/ 5. Pavement Interactive. (n.d). Coarse Aggregate Specific Gravity. 6. Retrieved from https://www.pavementinteractive.org/reference-desk/testing/aggregate-tests/coarseaggregate-specific-gravity/ 7. Dr. Aslan Al-Omari, Materials of Construction, retrieved from

http://faculty.ksu.edu.sa/aslam/Aslam%20Courses/Chapter%203_Construction %20Materials.pdf

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8. Roy Whitlow (2004). Basic Soil Mechanics. Pearson Education South Asia Pte Ltd. 9. Doran, D. (1992). Construction Materials Reference Book. Butterworth-Heinemann Ltd. 10.