 Classification  Features in Influencing Concrete  Fine Aggregate-Sand  Coarse Aggregate-Gravel Aggregate

Features in Influencing Concrete Features in Influencing Concrete  Physical characteristics influence this behavior, such as particle size distribution, particle shape, surface texture, and hardness.  Chemical composition and reactivity influence the properties of hardened concrete.

 T he maximum amount of aggregate should be used in concrete mixtures.  Aggregate generally increases the quality and the economy of concrete.  In each cubic meter of Portland cement, water paste will cost approximately 4 times as much as that (solid volume) of aggregate.  Aggregates also have greater dimensional stability, particularly less drying shrinkage than Portland cement paste. Features in Influencing Concrete Features in Influencing Concrete

 Feasibility requirements restrict the amount of aggregate in concrete mixtures.  Aggregate particles in effect float in the paste of the mixture.  When there is insufficient paste to fill the voids in the aggregate particles, the mixture becomes granular, crumbly, and unworkable because of particle interference.  The following describes the factors which influence the amount of aggregate. Features in Influencing Concrete Features in Influencing Concrete

Slump  1.Slump—As the aggregate content increases without changes in the paste content, the slump decreases. Grading  2.Grading—Proper grading of aggregate particles decreases the volume of voids among the aggregate particles, which permits a greater aggregate content in a mixture, without particle interference. Entrainedair  3.Entrained air—Entrained air, in effect, increases the volume of paste and permits an increase in aggregate content at the same slump. Features in Influencing Concrete

 4.Particle shape and surface texture  4.Particle shape and surface texture—There is usually a smaller volume of voids in rounded, smooth aggregates.  5.Water-reducing admixtures  5.Water-reducing admixtures—Dispersing agents commonly referred to as water-reducing admixtures make the paste more fluid by releasing water trapped by the cement. This permits an increase in the aggregate content at a given slump.  6.Viscosity of paste—  6.Viscosity of paste—An increase in viscosity of paste decreases the allowable aggregate content.  7.Temperature—  7.Temperature—High temperature increases the viscosity of paste and reduces the aggregate content for the same slump. Features in Influencing Concrete