Effects of Microfine Aggregate in Manufactured Sand on Bleeding and Plastic Shrinkage Cracking of Concrete

Abstract

Construction industries have started utilizing manufactured sand as an effective alternative for river sand in concrete. High-grade parent rocks are crushed to obtain manufactured sand which also enables a considerable amount of microfine aggregate. The higher percentage of microfine aggregate could lead to both positive and negative effects on the performance of cement-based mixes. This research was done to examine the influence of varying microfine aggregate levels such as 0%, 3%, 6%, 9% and 12% (by weight) as the partial replacements of manufactured sand on bleeding and plastic shrinkage cracking of concrete. In addition to the varying microfine aggregate levels, some concrete mixes also included fly ash and superplasticizer to investigate the effect of freewater content in the mixes. The bleeding test data were taken as the on-site measurements, while the cracks resulted from plastic shrinkage cracking test were evaluated using an image processing technique. The results concluded that the microfine aggregate replacements and the effective water-to-cement ratio have a dominant effect on the selected concrete properties. With the increasing replacement levels, cumulative bleeding and crack initiation life were gradually decreased while a progressive increase was noticed for crack width, crack length and crack area.