Hydration kinetics and microstructure development of Ultra-High Performance Concrete (UHPC) by high volume of phosphorus slag powder

Abstract

In this paper, the effect of phosphorus slag(PS)hydration kinetics and microstructural development of UHPC with different degree of substitute (20%, 40% and 60% by mass) were explored. Up to 60% substitution of cement by PS which still shown excellent mechanical property compared to without PS at the age of 60-days. The phase development is a qualitative discussion by thermal gravimetric analysis combined with XRD with Rietveld method, the pore structure is evaluated to MIP. The hydration products are characterized by SEM (scanning electron microscopy) with EDS (Energy-dispersive X-ray) analyses. The results shown that the utilization rate of cement has been significantly improved, for instance, the hydration rate of the cement is enhanced from 54.3% for PS0 to 87.0% for the UHPC with PS60; the Ca/Si ratio decreased with the enhance of PS content and the microstructure is become denser by SEM-EDS tests. The pozzolanic-reaction of PS cloud produce more hydrated products by thermodynamic calculation, which can optimize the pore structure of paste. And the growth trend of C–S–H gel is consistent with the compressive strength growth trend.