Shrinkage and Mitigation Strategies to Improve the Dimensional Stability of CaO-FeO_x-Al₂O₃-SiO₂ Inorganic Polymers

Volumetric stability is an important aspect of the performance of building materials, and the shrinkage of CaO-FeOx-Al₂O₃-SiO₂-rich inorganic polymers (IPs) has not been thoroughly investigated yet. Hence, this paper describes the outcome of a study conducted to investigate ways to minimize their shrinkage using different curing regimes. Two different slags were used as case studies to assess the robustness of the developed mitigation strategies. IP pastes and mortars were cured at (i) room condition, (ii) in slightly elevated temperature (60 °C for 2 d) and (iii) in a water-saturated environment. The reaction kinetics and formed products were examined on IP pastes, while mortars were made to characterize the 28 d pore structure, autogenous shrinkage, drying shrinkage, and strength development. The results showed that the precursors' reactivity and curing conditions severely affect shrinkage mechanisms and magnitude. Volumetric changes in the plastic stage can be related to the precursors' reactivity but drying shrinkage was the driving mechanism affecting the volumetric stability of all IP mortars. Understanding the effect of a precursor's composition and curing conditions on shrinkage is fundamental to develop proper mitigation strategies and to overcome one of IPs' main technical drawbacks.