Properties of calcium silicate-based inorganic phosphate cement at room controlled conditions

Abstract

Calcium phosphate cement (CPC) is a kind of chemically bonded phosphate cement that undergoes acid-base reaction to gain strength at room temperature conditions. The existing mix composition and methods previously proposed for making CPC are unsustainable. Two methods for producing more sustainable cement were employed in this research. These procedures involved the modification of the liquid/powder (L/P) ratio to use both less phosphoric acid and a simplified mixing approach complying with EN 196–1. First, the strength evolution of the phosphate cement was examined using destructive and non-destructive methods to determine the reference age to characterise the cement samples. This was found to be 14 days at room temperature of 20 oC and relative humidity of 65%. Then, the compressive strength, flexural strength, split tensile strength, density, mass loss, porosity and morphology of the cement were studied with respect to three parameters (L/P, type of mould and curing age) identified to have significant influence on their behaviour. It was established that the new techniques applied were adequate for manufacturing lightweight structural products with minimal environmental impact. Also, the use of an L/P ratio of 1.00, a non-airtight mould and an increased curing age favoured the formation of cement with improved properties. The overall behaviour of CPC was linked to the reaction rate in the fresh state of the material.