Setting reaction of a olivine-based Mg-phosphate cement
Davide Bernasconi, Alberto Viani, Lucie Zárybnická, Simone Bordignon, Jose R. A. Godinho, Alexey Maximenko, Cem Celikutku, Sadaf Fatima Jafri, Elisa Borfecchia, Quentin Wehrung, Roberto Gobetto, Alessandrο Pavese
Abstract
The cementitious properties of natural Mg-rich olivine when reacted with a phosphoric acid solution are investigated, as a function of acid concentration and liquid/solid mass ratio. The obtained cements are composed of residual olivine crystals and amorphous silica nanoparticles dispersed in a dense and compact newberyite (MgHPO 4 ∙3H 2 O) matrix. The latter was mostly formed by packed micrometric tabular crystals, although evidence of the presence of a fraction of amorphous MgHPO 4 was also found. Water content in the raw mix was observed to play a pivotal role on the reaction pathway, either promoting porosity or hindering the crystallization of the products. Up to 57 % of olivine reactivity, whose dissolution was promoted by the curing temperature (60 °C) and low pH, was achieved. All in all, these results indicate that the industrial mineral olivine may serve a viable source of Mg for the production of phosphate cements. • Mg-olivine is tested for the first time as raw material in the production of MPC. • The cements are made of amorphous silica dispersed in a dense newberyite matrix. • The precipitated Mg-phosphates are mostly crystalline. • Water plays a pivotal role in defining the reaction pathways. • Up to 75 MPa of compressive strength is reached.