Sab 2112 - L4 Aggregates
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AGGREGATES Strength Dimension stability Economy
Objectives Understand: Types of aggregates Characteristics and properties of aggregates Test of aggregates
Aggregates A rocklike material of various sizes and shapes used in the manufacture of concrete ASTM defines aggregates as granular material such as sand, gravel, crushed stone used with cementing medium to form mortar or concrete
Aggregates Natural – taken from natural deposits without change in their nature during production Manufactured – include blastfurnace slag, clay, lightweight aggregate
Aggregates Coarse Crushed Uncrushed
Fine Crushed Uncrushed
Based on sizes Fine aggregate – less than 5 mm (C, M, F)
Coarse aggregate – greater than 5 mm ( 10, 20, 40 mm)
Aggregates Crushed – sharp angular particles, from quarry, rough surface, good bond strength, low workability
Uncrushed Uncrushed – round shapes, smooth surface, from river, low bonding properties, high workability
Types of rock Granite – hard, tough and dense Sandstone – may contain clay Limestone – may contain clay
Types of aggregates based on specific gravity Lightweight aggregate Normal weight aggregate Heavyweight aggregate
Lightweight Aggregate Bulk density less than 1200 kg/m3 Used in manufacturing lightweight concrete, lightweight masonry block Porous, good thermal insulation Natural lightweight aggregate consists of particles derived from natural rocks, primarily those of natural volcanic origin
Cont. Manufactured lightweight aggregate – is produced by expanding some raw materials in a rotary kiln, on a sintering grate, or by mixing them with water
Normal Weight Aggregate Density in the range of 2300 – 2500 kg/m3 Mostly obtained from quarry, river Specific gravity in the range of 2.5-3.0 Suitable for most constructions Need to be cleaned from impurities Chloride content should be less than 1%
Heavyweight Aggregate Density in the range of 4000 – 8500 kg/m3 Used primarily to manufacture heavyweight concrete for protection against nuclear radiation Low workability Eg. Barite with specific gravity of 4.5
Properties of Aggregates A number of physical and mechanical properties affect durability, strength, and performance of construction products manufactured using aggregates The aggregate particles should retain their strength, shape, and texture when used with materials such as cement
Properties of Aggregates Compressive strength Specific gravity Bulk density Porosity Voids Absorption
Modulus of elasticity Moisture content Shrinkage Grading and fineness Chemical reactivity
Specific Gravity The ratio of the mass of a unit volume of a material at a specific temperature to the mass of the same volume of gasfree distilled water at that temperature The weight of aggregate particles depend on the moisture level. The specific gravity readings should be associated with the moisture level or moisture content measurement
Example Aggregate
Type
Specific Gravity
Granite
Normal weight
2.65
Gravel
Normal weight
2.70
Sand
Normal weight
2.60
Scoria
Lightweight
0.75
Pumice
Lightweight
0.75
Hematite
Heavyweight
5.00
Barite
Heavyweight
4.50
Moisture Content Two types of moisture:
Absorbed moisture Surface moisture
Absorbed Moisture The weight of water absorbed by dry aggregate particles in reaching the saturated surface dry condition. Usually expressed as a percentage of dry weight In this state there is no water on the surface of a particle, but all the pores are filled with water A particle will neither absorb moisture from nor contribute moisture to the surrounding
Surface Moisture The moisture that is in excess of absorbed moisture
Level of Absorption Granite – less than 1% Porous sandstone – as high as 13% Lightweight aggregate – in the range of 5 – 20%
Moisture Condition of Aggregates Oven dry Air dry Surface Saturated Dry Wet
Effect Moisture Content Moisture Design (kg)
Absorbed Additional (kg) (kg)
Actual Workability Strength/ (kg) Durability
OvenDry
10
2
0
8
Decrease
Increase
Air-Dry
10
1
0
9
Decrease
Increase
SSD
10
0
0
10
Required
Required
Wet
10
0
2
12
Increase
Decrease
Oven-Dry Is obtained when all the moisture is driven out of the pores by drying the aggregate to a constant weight at temperature of about 110 °C When mixing water is introduce into the concrete mix part of it will be absorbed by the aggregate resulting to less water for hydration process and workability of concrete
Air-Dry Is the condition when the amount of moisture in the particles is less than that of the saturated surface dry condition but more than which remains in oven dry condition Part of the mixing water will be absorbed by the aggregate during mixing of concrete
Surface Saturated Dry When all pores in the particles are filled with water but no moisture exists on the outside surface The mixing water will be used totally for the hydration process and workability of concrete
Wet When excess moisture (free water or surface moisture) remains on the surface of particles, as in sand exposed to rainwater There will be extra water in the concrete mix which will affect the compressive strength
How Level of Moisture Affect Workability Strength Durability
Example Determine the moisture content, absorption, and free moisture content of the fine aggregate sample. Initial sample weight = 1.2 kg Saturated surface dry weight = 1.14 kg Oven-dry weight = 1.06 kg
Moisture Content Moisture content = (Initial sample wt – Oven-dry wt) / (Oven-dry wt) * 100 = (1.2 – 1.06) / 1.06*100 = 13.2%
Absorption Absorption = (SSD wt – Oven-dry wt) / Oven-dry wt * 100 = (1.14 – 1.06) / 1.06*100 = 7.5%
Free Moisture Free Moisture = Moisture content – Absorption = 13.2 – 7.5 = 5.7%
BUKL DENSITY OF AGGREGATE
Bulk density Known as unit weight or dry-rodded weight The mass per unit volume of aggregate The mass is determined in dry condition and the volume includes the volume of voids
Void Represent the amount of air space in the aggregate or space between the particles Void content is generally expressed as percent of gross volume which is solid volume plus volume of voids
Porosity Is defined as the ratio of the volume of the pores in a particle to its total volume of solid volume plus the pore volume How it affects strength and durability?
Modulus of Elasticity Defined as the ratio of stress to corresponding strain below the proportional limit The modulus of elasticity of concrete increases with increase in the modulus of aggregate Creep and shrinkage of concrete also affected by the modulus of elasticity of aggregate
Compressive Strength Compressive strength of aggregate depends on the compressive strength of the original rock It will affect the compressive strength of concrete
Gradation/Grading Gradation refers to the proportions of aggregate distributed in specified particlesize range
Important property that affects mix proportions, workability, economy, porosity, durability and shrinkage of the finish product
Grading Refers to the process that determines the particle size distribution of a representative sample of the aggregate
Sieve analysis – the process of dividing a sample of aggregate into fractions of same particle size
Graded Normally graded aggregate – conforms to the grading limits Dense-graded aggregate – particle-size distribution with least voids Open-graded aggregate – particle-size distribution with many voids Gap-graded aggregate – one or more intermediate sizes are missing
Sieve Apparatus Larger to smaller sizes Square opening 10 minutes Weigh the aggregate retain
SIEVE
SHAKER
Grading limits (BS 882:1983) Sieve size
Overall limits
Coarse (C)
Medium Fine (F) (M)
5 mm
89-100
-
-
-
2.36
60-100
60-100
65-100
80-100
1.18
30-100
30-90
45-100
70-100
600 um
15-100
15-54
25-80
55-100
200
5-70
5-40
5-48
5-70
150
0-15
-
-
-
Example Sieve size
Mass Percentage retained (g) retained (%)
Percentage cumulative passing (%)
Grading (compare, M)
10.0 mm
0
0
100
5.00
6
2
98
-
2.36
31
10
88
65-100
1.18
30
10
78
45-100
600 um
59
19
59
25-80
300
107
35
24
5-48
150
53
17
7
-
Less 150
21
7
0
TOTAL
307
Particle Size Distribution
Effect Of Gradation
Strength and Durability
Corrosion
How do this occur?
Arigato
Oh No.. You Can’t Catch Me
Objectives Understand: Types of aggregates Characteristics and properties of aggregates Test of aggregates
Aggregates A rocklike material of various sizes and shapes used in the manufacture of concrete ASTM defines aggregates as granular material such as sand, gravel, crushed stone used with cementing medium to form mortar or concrete
Aggregates Natural – taken from natural deposits without change in their nature during production Manufactured – include blastfurnace slag, clay, lightweight aggregate
Aggregates Coarse Crushed Uncrushed
Fine Crushed Uncrushed
Based on sizes Fine aggregate – less than 5 mm (C, M, F)
Coarse aggregate – greater than 5 mm ( 10, 20, 40 mm)
Aggregates Crushed – sharp angular particles, from quarry, rough surface, good bond strength, low workability
Uncrushed Uncrushed – round shapes, smooth surface, from river, low bonding properties, high workability
Types of rock Granite – hard, tough and dense Sandstone – may contain clay Limestone – may contain clay
Types of aggregates based on specific gravity Lightweight aggregate Normal weight aggregate Heavyweight aggregate
Lightweight Aggregate Bulk density less than 1200 kg/m3 Used in manufacturing lightweight concrete, lightweight masonry block Porous, good thermal insulation Natural lightweight aggregate consists of particles derived from natural rocks, primarily those of natural volcanic origin
Cont. Manufactured lightweight aggregate – is produced by expanding some raw materials in a rotary kiln, on a sintering grate, or by mixing them with water
Normal Weight Aggregate Density in the range of 2300 – 2500 kg/m3 Mostly obtained from quarry, river Specific gravity in the range of 2.5-3.0 Suitable for most constructions Need to be cleaned from impurities Chloride content should be less than 1%
Heavyweight Aggregate Density in the range of 4000 – 8500 kg/m3 Used primarily to manufacture heavyweight concrete for protection against nuclear radiation Low workability Eg. Barite with specific gravity of 4.5
Properties of Aggregates A number of physical and mechanical properties affect durability, strength, and performance of construction products manufactured using aggregates The aggregate particles should retain their strength, shape, and texture when used with materials such as cement
Properties of Aggregates Compressive strength Specific gravity Bulk density Porosity Voids Absorption
Modulus of elasticity Moisture content Shrinkage Grading and fineness Chemical reactivity
Specific Gravity The ratio of the mass of a unit volume of a material at a specific temperature to the mass of the same volume of gasfree distilled water at that temperature The weight of aggregate particles depend on the moisture level. The specific gravity readings should be associated with the moisture level or moisture content measurement
Example Aggregate
Type
Specific Gravity
Granite
Normal weight
2.65
Gravel
Normal weight
2.70
Sand
Normal weight
2.60
Scoria
Lightweight
0.75
Pumice
Lightweight
0.75
Hematite
Heavyweight
5.00
Barite
Heavyweight
4.50
Moisture Content Two types of moisture:
Absorbed moisture Surface moisture
Absorbed Moisture The weight of water absorbed by dry aggregate particles in reaching the saturated surface dry condition. Usually expressed as a percentage of dry weight In this state there is no water on the surface of a particle, but all the pores are filled with water A particle will neither absorb moisture from nor contribute moisture to the surrounding
Surface Moisture The moisture that is in excess of absorbed moisture
Level of Absorption Granite – less than 1% Porous sandstone – as high as 13% Lightweight aggregate – in the range of 5 – 20%
Moisture Condition of Aggregates Oven dry Air dry Surface Saturated Dry Wet
Effect Moisture Content Moisture Design (kg)
Absorbed Additional (kg) (kg)
Actual Workability Strength/ (kg) Durability
OvenDry
10
2
0
8
Decrease
Increase
Air-Dry
10
1
0
9
Decrease
Increase
SSD
10
0
0
10
Required
Required
Wet
10
0
2
12
Increase
Decrease
Oven-Dry Is obtained when all the moisture is driven out of the pores by drying the aggregate to a constant weight at temperature of about 110 °C When mixing water is introduce into the concrete mix part of it will be absorbed by the aggregate resulting to less water for hydration process and workability of concrete
Air-Dry Is the condition when the amount of moisture in the particles is less than that of the saturated surface dry condition but more than which remains in oven dry condition Part of the mixing water will be absorbed by the aggregate during mixing of concrete
Surface Saturated Dry When all pores in the particles are filled with water but no moisture exists on the outside surface The mixing water will be used totally for the hydration process and workability of concrete
Wet When excess moisture (free water or surface moisture) remains on the surface of particles, as in sand exposed to rainwater There will be extra water in the concrete mix which will affect the compressive strength
How Level of Moisture Affect Workability Strength Durability
Example Determine the moisture content, absorption, and free moisture content of the fine aggregate sample. Initial sample weight = 1.2 kg Saturated surface dry weight = 1.14 kg Oven-dry weight = 1.06 kg
Moisture Content Moisture content = (Initial sample wt – Oven-dry wt) / (Oven-dry wt) * 100 = (1.2 – 1.06) / 1.06*100 = 13.2%
Absorption Absorption = (SSD wt – Oven-dry wt) / Oven-dry wt * 100 = (1.14 – 1.06) / 1.06*100 = 7.5%
Free Moisture Free Moisture = Moisture content – Absorption = 13.2 – 7.5 = 5.7%
BUKL DENSITY OF AGGREGATE
Bulk density Known as unit weight or dry-rodded weight The mass per unit volume of aggregate The mass is determined in dry condition and the volume includes the volume of voids
Void Represent the amount of air space in the aggregate or space between the particles Void content is generally expressed as percent of gross volume which is solid volume plus volume of voids
Porosity Is defined as the ratio of the volume of the pores in a particle to its total volume of solid volume plus the pore volume How it affects strength and durability?
Modulus of Elasticity Defined as the ratio of stress to corresponding strain below the proportional limit The modulus of elasticity of concrete increases with increase in the modulus of aggregate Creep and shrinkage of concrete also affected by the modulus of elasticity of aggregate
Compressive Strength Compressive strength of aggregate depends on the compressive strength of the original rock It will affect the compressive strength of concrete
Gradation/Grading Gradation refers to the proportions of aggregate distributed in specified particlesize range
Important property that affects mix proportions, workability, economy, porosity, durability and shrinkage of the finish product
Grading Refers to the process that determines the particle size distribution of a representative sample of the aggregate
Sieve analysis – the process of dividing a sample of aggregate into fractions of same particle size
Graded Normally graded aggregate – conforms to the grading limits Dense-graded aggregate – particle-size distribution with least voids Open-graded aggregate – particle-size distribution with many voids Gap-graded aggregate – one or more intermediate sizes are missing
Sieve Apparatus Larger to smaller sizes Square opening 10 minutes Weigh the aggregate retain
SIEVE
SHAKER
Grading limits (BS 882:1983) Sieve size
Overall limits
Coarse (C)
Medium Fine (F) (M)
5 mm
89-100
-
-
-
2.36
60-100
60-100
65-100
80-100
1.18
30-100
30-90
45-100
70-100
600 um
15-100
15-54
25-80
55-100
200
5-70
5-40
5-48
5-70
150
0-15
-
-
-
Example Sieve size
Mass Percentage retained (g) retained (%)
Percentage cumulative passing (%)
Grading (compare, M)
10.0 mm
0
0
100
5.00
6
2
98
-
2.36
31
10
88
65-100
1.18
30
10
78
45-100
600 um
59
19
59
25-80
300
107
35
24
5-48
150
53
17
7
-
Less 150
21
7
0
TOTAL
307
Particle Size Distribution
Effect Of Gradation
Strength and Durability
Corrosion
How do this occur?
Arigato
Oh No.. You Can’t Catch Me
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