Investigation of composite anhydrite cement pozzolana binding material with different aggregates

Abstract

In this work the hardening process, strength, and structure of hydraulic composite unburnt natural anhydrite cement pozzalona binding material (ACPBM) with different aggregates have been investigated. Common inert aggregates (such as sand, crushed granite) and the ones made from a crushed up anhydrite rock were used for the investigation. It was established that the ACPBM with anhydrite aggregates has better strength and water resistance properties than the ACPBM of same composition with inert aggregates. The anhydrite aggregate is chemically active during the hardening of ACPBM. The surface layer of the aggregate interacts with the products of ACPBM’s hydration, and, therefore, the aggregate bonds firmly with the matrix of the binding material. As a result, a strong solid structure of hardening forms. The hardening activators of anhydrite activate the hydration of the aggregates’ surface and strengthen the adherence between them and the matrix of the binding material. The strength of hardened compositions may reach up to 40 MPa, the coefficient of softening in water is 0,85 – 0,95, moreover, due to a slow hydration of anhydrite component a permanent increase in strength is observed.