The effect of limestone powders on the fresh and hardened properties of self-compacting pastes, mortars and concrete

Abstract

Due to its unique properties, self-compacting concrete (SCC) needs a high percentage of powder to be able to satisfy the paste requirements for high viscosity as well as high deformability. This can be met by increasing the cement content but this will increase the overall cost of the project and create other problems such as a higher rate of hydration and higher drying shrinkage. Alternatively non-pozzolanic fillers are introduced as a replacement to cement to improve the particle packing and flow behaviour of the cementing paste in SCC. Previous studies have shown that limestone powders proved to be successful mineral admixtures in self-compacting concrete with a significantly high number of applications being listed in literature using this particular additive. In this study four different limestone powders were introduced in the mixes replacing the cement content at 3 replacement levels; 10%, 20% and 30 %. One foreign limestone powder with a high content of Calcium Carbonate (CaCo3) and three local limestone powders: one type of Upper Coralline Limestone, two types of Globigerina Limestone, were studied when forming part of a paste, when used in self-compacting mortar mixes and eventually self-compacting concrete. Their effects on the fresh properties of the pastes and mortars using different water/powder ratios as well as different superplasticiser dosages were studied.