Influence of metal-organic framework-based composite phase change materials on the hydration performance of cement containing heavy metals for collaborative disposal

The cement containing heavy metals for collaborative disposal (HMC) as a low-environmentalload cementitious material still encounters challenges related to temperature-induced cracking due to high hydration heat. In this paper, a paraffin (PA)/metal-organic framework (MOF) composite phase change material (CPCM) with excellent shape stability, thermal storage capacity, and thermal stability was creatively integrated into HMC, aiming to investigate the impacts of CPCM on the hydration heat release behavior. The compressive strength and hydration product evolution of HMC paste mixed with CPCM were also discussed. The experimental results demonstrated that CPCM notably reduced the initial hydration rate (especially the main exothermic peaks) and total hydration heat of HMC, regardless of the hydration temperature. Furthermore, the impact of CPCM on the hydration heat of HMC was found to be positively correlated with the dosage. Additionally, the compressive strength of composite paste decreased and chromium (Cr) leaching content increased due to the addition of CPCM, which can be attributed to the expansion of paste pores. But, the additional inclusion of minute quantities of ZIF-8 significantly ameliorated these negative effects. Moreover, CPCM, ZIF-8, and hydration temperatures did not change the type of hydration products in HMC, but they did affect the amount and microstructure of hydration products. CPCM indeed effectively reduced the hydration heat of HMC, this study offers new insights into the use of phase change materials to mitigate the thermal cracking issue in cementitious materials.