In this study, the shape of coarse aggregate particles has been related to the workability and compressive strength of cement concrete for rigid pavements. The shape characteristics such as elongation, flatness, shape factor, and...
moreIn this study, the shape of coarse aggregate particles has been related to the workability and compressive strength of cement concrete for rigid pavements. The shape characteristics such as elongation, flatness, shape factor, and sphericity were determined. Also,the slump and compressive strength of cement concrete were determined for various shapes of coarse aggregate. The test results indicated that there is a good correlation between some shape properties of aggregate, workability, and compressive strength.The highest compressive strength at different ages noted with concrete made from different shapes of coarse aggregates. Results indicate that the strength of concrete varies as a function of the shape of the coarse aggregate, which leads to the conclusion that the shape of aggregate shall be considered as an important parameter in deciding the suitability of coarse aggregate to prepare cement concrete for rigid pavements. I. INTRODUCTION To provide a stable and even surface for the traffic, the roadway is always provided with a suitably designed and constructed pavement structure. Thus, a pavement consisting of a few layers of pavement materials is constructed over a prepared layer of sub-grade to serve as a carriageway. Based on design consideration pavements can be classified as-Rigid pavements and Flexible pavement. Flexible pavements can be defined as the one consisting of a mixture of asphaltic or bituminous material and aggregates placed on a bed of compacted granular material of appropriate quality in layers over the subgrade. Rigid pavements are those, which possess noteworthy flexural strength or flexural rigid. The rigid pavement has the slab action and is capable of transmitting the wheel load stresses through a wider area below. Cement concrete is a composite material produced by the homogenous mixing of selected proportions of water, cement, and aggregates (fine and coarse). Strength is the most desired quality of a good concrete. It should be strong enough, at hardened state, to resist the various stresses to which it would be subjected. Aggregates are the most important constituents in cement concrete. For a long time aggregates were considered as inert materials, but after 1940 it was brought out that aggregates do show some reactivity. The mere fact that aggregates constitute 70-80% of the volume of concrete, their impact on various characteristics is undoubtedly considerable. Aggregates give the body to the concrete, reduce shrinkage, and affect the economy. Among all the characteristics of aggregates, the shape is most important because it affects the workability and compressive strength of cement concrete. Aggregates form the major portions of pavement structure and aggregates have to bear stresses occurring due to wheel loads on the pavement and on the surface-course they have to resist wear due to the abrasive action of traffic. Therefore, the properties of aggregates are of considerable significance to the highway engineers. Significant findings indicate that aggregate plays a more "active" role than was previously believed, and a better understanding will result from further research. Several authors have indicated the need for more research to determine the effect of aggregate particle shape on the properties of concrete at present there is only alimited amount of information concerning the effect of aggregate particle shape on concrete proportioning, workability, and strength. This lack of information is reflected in specifications that place conservative limits on allowable amounts of particles of certain shapes. The present study was undertaken to investigate the effect of different types of coarse aggregate effect on the fresh and hardened Portland cement concrete behavior by a means of aggregate shape indexes such as elongation, flatness, roundness, shape factor, and sphericity.
