Studies On Sandy Slate Powder Used As Mineral Admixture

In the concrete engineering, using mineral admixture can reduce the dosage of cement and improve the performance of concrete. Though fly ash and blast furnace widely used in hydropower engineering, there might be a shortage for both material. Sandy slate powder used as substitute can not only meet the performance requirements, but also bring better economic benefits. In order to effectively exploit powder resource in engineering project, there should be studies on mechanism of sandy slate powder used as mineral admixture and its influence on concrete.This paper mainly discussed in three aspects:gelling system, concrete and microstructure. The changes of performance indexes were investigated under different conditions such as different dosage and fineness of sandy slate powder and different blending methods. Experimental results for gelling system and concrete shows that the dosage of mineral admixture is the main factors affecting the performance of concrete, and the fineness of sandy slate powder comes to be the secondary factors. Low dosage powder can improve the workability of concrete, relatively high dosage will increase the workability and strength of concrete. While mixed with fly ash, sandy slate powder compensates the decrease of concrete property, it is feasible to mix two mineral admixtures to meet the technical requirements in practice.By means of scanning electron microscopy (SEM), X-ray diffraction (XRD) and mercury intrusion porosimetry (MIP), hydration process, hydration products and pore structure of concrete mixed with sandy slate powder were investigated. Results show that sandy slate powder accelerates the early hydration. With the increasing dosage, the total amount of hydration products reduced and the pore filled well. Method of mixing fly ash and sandy slate powder makes the pore structure into a better condition, which can be considerably taken in practice.