05-26-2022, 12:15 PM
Aggregates for mortar & concrete
Taken from : Ambuja Technical Literature Series -5
1.0 INTRODUCTION
Concrete or mortar is made up of cement, water and aggregates (stone chips + sand) and at times chemical additives. In concrete, fine (sand) and coarse (stone chips or gravel) aggregates make up about 75% of the total concrete material. It is therefore significantly important to obtain the right type and quality of aggregates at site.
The aggregates form the main matrix of the concrete or mortar. The aggregate particles are glued together by the cement and water paste. There are two types of aggregates the coarse aggregates which form the main matrix and the fine aggregates which form the filler matrix between the coarse aggregates. With cement and water the entire matrix binds together into a solid mass called concrete.
Unlike cement, aggregates are not branded in our country and hence the suppliers and manufacturers seldom bother to give the required quality or specifications. It is always take it or forget it. It is therefore the responsibility of the Site Engineers and Supervisors to clean and/ or reprocess the aggregates so that they comply with the quality standards and specifications.
Aggregates influence the properties of concrete/mortar such as water requirement, cohesiveness and workability of the concrete in plastic stage, while they influence strength, density, durability, permeability, surface finish and colour in hardened stage.
2.0 TYPES OF AGGREGATES
The aggregates are generally classified into two types - natural and manufactured/ processed. Natural gravel aggregates are either dug from a pit or dredged from the river or creek (See Figure 1). Processed crushed rock aggregates are obtained by quarrying solid rock and then crushing it to a suitable size and grading (See Figure 2).
Aggregates obtained from the pits or dredged from the river, creek or sea are most often not clean enough or well graded to suit the quality requirement. They therefore require sieving (See Figures 3 & 4) and washing (See Figures 5 & 6) before they can be used in concrete.
Natural aggregates are produced by the forces of nature. They may be water worn resulting in rounded shape or may be crushed from massive boulders and hence angular in shape. The density of the aggregates vary depending on the porosity and type of parent material. They may be igneous (granite or basalt) or sedimentary (limestone) rock. Geologically aggregates may be from basalt, granite, limestone, quartzite, gabbro or schist etc. but generally they are all suitable for concrete depending on their degree of weathering, density and shape.
for more details download .....
Taken from : Ambuja Technical Literature Series -5
Taken from : Ambuja Technical Literature Series -5
1.0 INTRODUCTION
Concrete or mortar is made up of cement, water and aggregates (stone chips + sand) and at times chemical additives. In concrete, fine (sand) and coarse (stone chips or gravel) aggregates make up about 75% of the total concrete material. It is therefore significantly important to obtain the right type and quality of aggregates at site.
The aggregates form the main matrix of the concrete or mortar. The aggregate particles are glued together by the cement and water paste. There are two types of aggregates the coarse aggregates which form the main matrix and the fine aggregates which form the filler matrix between the coarse aggregates. With cement and water the entire matrix binds together into a solid mass called concrete.
Unlike cement, aggregates are not branded in our country and hence the suppliers and manufacturers seldom bother to give the required quality or specifications. It is always take it or forget it. It is therefore the responsibility of the Site Engineers and Supervisors to clean and/ or reprocess the aggregates so that they comply with the quality standards and specifications.
Aggregates influence the properties of concrete/mortar such as water requirement, cohesiveness and workability of the concrete in plastic stage, while they influence strength, density, durability, permeability, surface finish and colour in hardened stage.
2.0 TYPES OF AGGREGATES
The aggregates are generally classified into two types - natural and manufactured/ processed. Natural gravel aggregates are either dug from a pit or dredged from the river or creek (See Figure 1). Processed crushed rock aggregates are obtained by quarrying solid rock and then crushing it to a suitable size and grading (See Figure 2).
Aggregates obtained from the pits or dredged from the river, creek or sea are most often not clean enough or well graded to suit the quality requirement. They therefore require sieving (See Figures 3 & 4) and washing (See Figures 5 & 6) before they can be used in concrete.
Natural aggregates are produced by the forces of nature. They may be water worn resulting in rounded shape or may be crushed from massive boulders and hence angular in shape. The density of the aggregates vary depending on the porosity and type of parent material. They may be igneous (granite or basalt) or sedimentary (limestone) rock. Geologically aggregates may be from basalt, granite, limestone, quartzite, gabbro or schist etc. but generally they are all suitable for concrete depending on their degree of weathering, density and shape.
for more details download .....
Taken from : Ambuja Technical Literature Series -5