Short -and long- term performances of extrudable reactive powder concretes

The results of an experimental study on the mix design and the characterization of extrudable reactive powder concrete (ERPC) are presented. Five concrete mixes were prepared with variable amounts of polycarboxylate superplasticizer (SP), silica fume (SF) and crushed quartz (CQ). The extrudability of the ERPC was first demonstrated through extrusion tests performed with a ram extruder at different compression speeds. Then, the influence of the dosages in SP, SF and CQ on early-age hydration rate, autogenous shrinkage, 28-days mechanical performances, gas permeability, total porosity and chloride penetration rate was quantified. The increase in SP dosage caused a retardation of hydration and an increase of early-age autogenous shrinkage. Moreover, the partial substitution of silica fume with crushed quartz had a positive effect on hydration rate, autogenous shrinkage and mechanical properties. This result was mainly attributed to a higher amount of water available for cement hydration, induced by the coarser particle size distribution of crushed quartz as compared with silica fume.