Engineering properties and microstructure analysis of magnesium phosphate cement mortar containing bentonite clay

The key goals of this study was to investigate the engineering characteristics and microstructure formation pattern of magnesium phosphate cement (MPC) mortar by adding bentonite clay (BC). For this purpose, consecutive dosages of BC were added in place of magnesia for preparing the surrogate specimens and kept in two static curing conditions like air and water for comparing the target objectives. The analytical results indicated that the consecutive increment of BC quantity up to 20% exhibited the satisfactory level of water absorption reduction, strength activity indices (SAI) and strength retention coefficient, where 10% and 15% BC contents greatly improved the density, porosity, water permeability resistant, compressive strength and flexural strength performance in both air and water environment than control MPC mortar over the whole test protocol time. MPC composites bearing 15% BC revealed the density, porosity and water diffusion coefficient (WDC) around 2.45 g/cm(3) at 14 d, 2.65% at 14 d and 0.04 mm(2)/s at 8 h, respectively, and the uniaxial compressive and flexural strength showed around 82.7 MPa and 11.4 MPa at 28 d in air curing regime. Additionally, the microstructure analyzed by XRD and SEM also corroborated the strength performances and engineering parameters of specimens. Fourier Transform Infrared spectroscopy (FTIR) analysis also showed the absence of new chemical groups formation between the interaction of BC and MPC pastes, which proved that BC acted only as pore-filled material for improving the engineering properties. The findings of the current study might be a potential solution to produce the cost-effective BC-MPC block with durable quality. (C) 2019 Elsevier Ltd. All rights reserved.