Aggregate Classification [Based on Shape] According to shape the aggregate is classified as Rounded aggregate Irregular or partly rounded aggregate Angular aggregate Flaky aggregate Elongated aggregate Flaky and elongated aggregate 1. Rounded Aggregate The aggregate with rounded shape has the minimum percentage of voids ranging from 32 to 33%. It gives minimum ratio of surface … Read more
Concrete is prepared by mixing aggregate, cement and water in such a proportion that it becomes workable in its plastic state and durable in its hardened state. Our aim is to satisfy both of these requirements i.e. workability and durability. Importance in terms of Workability A workable concrete can be achieved by adding more water, … Read more
Aggregate should have the following qualities Quality Requirements of Aggregate Aggregates should be strong, hard, dense, durable, clear and free from veins and adherent coating. Aggregates should be free from injurious amounts of disintegrated pieces, alkalis, vegetable matter and other deleterious substances. Flaky and Elongated pieces should not be present in aggregate mass. Aggregate crushing … Read more
Objective This test is intended to study the resistance of coarse and fine aggregates to weathering action and to judge the durability of the coarse aggregate. Apparatus Name Capacity Least count Balance 500 g 0.1 g Balance 5000 g 1 g Oven 105 to 1100C Sieves 80 mm, 63 mm, 40 mm, 31.5 mm, … Read more
Objective To determine the approximate percentage of light weight pieces (i.e. coal & lignite) in aggregate by means of sink-float separation in a heavy liquid of suitable specific gravity. Apparatus Name Capacity Least Count Balance 500 g 0.1 g Balance 5000 g 1 g Oven 100 to 1100C Sieve 300 micron, 4.75 mm … Read more
The following properties of aggregate affect the properties of hardened concrete. 1. Grading Aggregate grading has no significant effect on the properties of hardened concrete. 2. Bulk Density This has no direct effect but has an indirect effect on drying shrinkage. Bulk density is an indicator of packing capacity, which influences water requirement, which in … Read more
Grading In case of sands, it has been found that materials having a large deficiency or excess of any size fraction adversely affect the workability of concrete. The most important size fraction in a concrete sand are those passing the 0.30, 0.15 and 0.075 mm sieves. If these fractions are too low the concrete tends … Read more
Objective To determine quantity of silt in fine aggregates in the field Theory There are two types of harmful substances preset in fine aggregates i.e. organic matter produced by decay of vegetable matter and/or clay and silt, which form coating thus preventing a good bond between cement and the aggregates. If present in large quantities, … Read more
What is Gap Graded Aggregate? Generally we use well graded aggregate or continuous graded aggregate, which means representation of all the standard particle sizes in certain proportion. Assumption made in well gradation is that voids created by the higher size of aggregate will be filled-up by immediate next lower size of aggregate and again some … Read more
The volume increase of fine aggregate due to presence of moisture content is known as bulking. Fine sand bulks more as compared to coarse sand. Extremely fine sand particularly the manufactured fine aggregate bulks as much as about 40%. Note: Fine aggregate do not show any bulking when it is absolutely dry or completely saturated. … Read more