The effects of the properties of coarse aggregates on the workability of concrete

Abstract

Summary It is well known that different types of aggregate produce different degrees of workability when used in concrete of given mix proportions and water/cement ratio. A rounded aggregate will, for example, give concrete of higher workability than all angular aggregate. Thirteen coarse aggregates were investigated to determine the effects of their shape, surface texture and water absorptive capacity on the workability of concrete. An attempt has also been made to assess these effects quantitatively. The main conclusions were as follows. (1) Changes in the angularity of coarse aggregates have a greater effect on the workability of concrete than changes in the flakiness of the aggregates. Increased angularity and/or flakiness leads to a reduction in the workability of concrete. (2) Although there was a wide variation in the surface textures of the aggregates, no correlation was found between this property and the workability of concrete. (3) The differences in the capacities of the aggregates to absorb water were insufficient to produce significant changes in the compacting factor. No correlation was, therefore, found between this property and concrete workability. This does not rule out the possibility that highly porous aggregates when used in a dry condition will affect the workability of concrete.

Physical Characterization and Optimization of Fineness Moduli of Natural Sand from The North Region of Cameroon Used in Construction

“…Rounded aggregate contain fewer voids which result into higher workability. Hence, angular particles of aggregates tend to more packed, and possess higher strength and durability in hardened mix of concrete and mortar (Kaplan et al, 1958). The studied sand have sub-angular grains, so their use in concrete does not require much water.…”

Precise shape grading of coarse aggregate

“…It may be described as 100Va I s= --v;;- (4) where Va is the volume of the aggregate. For the purposes of the paper the indices will be expressed as dimensionless integers.…”

“…I s was then calculated in accordance with equation (4). As the analysis of the results assumes random values constrained by an S distribution, according to Francis 13 it was necessary for the sample size to exceed 30 in number as a prerequisite for probabilistic validity.…”

A New Method for Determining the Angularity of Particles

“…(5) Workability of concrete (KAPLAN, 1958 TRUESDALE et al, 1962). (9) Transportation of particles by wind and water (BAGNOLD, 1954; DALLA VALLE, (10) Erosive power of transported particles.…”