Test method proposal for assessing the occurrence of alkali-silica reaction (ASR) in magnesium phosphate cement matrices

Resumen

Replacing ordinary Portland cement (OPC) with alternative binders is a technical and economically feasible solution to reduce the environmental impact caused by civil construction. Among these binders, there are those belonging to the Chemically Bonded Phosphate Ceramics (CBPC) family, in which magnesium phosphate cement (MPC), originated by acid-base reactions, is included. However, due to the formation of different phases compared to OPC, an in-depth study of this material's durability is essential to understand the new matrix and its application possibilities. This paper proposes adapting the usual method of evaluating the alkali-silica reaction (ASR) in Portland cement matrices to evaluate MPC matrices. For this purpose, reference mortars with OPC and two MPC mortars with different M/P (magnesia/phosphate) molar ratios were cast with reactive aggregate to assess the occurrence of ASR. It was observed that after 56 days of testing, under low temperatures, the MPC mortars with the highest M/P molar ratio showed low expansion, while in the mortars with OPC, and MPC with the lowest M/P molar ratio, the aggregates showed deleterious reactions. The proposed adaptation of the ASR test method considering the particularities of MPC mortars was satisfactory.