Mechanical, hydration, and microstructural behavior of cement paste incorporating Zeolitic imidazolate Framework-67 (ZIF-67) nanoparticles

Zeolitic imidazolate frameworks (ZIFs) have recently emerged as attractive materials for several applications including the building and construction sector. Unlike most other 2D nanomaterials, ZIFs usually possess high porosity and specific surface area. In this work, the feasibility and compatibility of utilizing a small percentage of ZIF-67 (0–0.9 wt.%) as an additive to cement-based materials has been investigated. The mineralogy, morphology, and microstructure of the cement paste ZIF-67 composites were characterized using different techniques (i.e., SEM-EDX, Raman, and XRD). The compressive and direct tensile strengths, water absorption, dry density, and calorimetry heat flow tests of the cement paste ZIF-67 composites were also evaluated. The results revealed that the optimum content of ZIF-67 is 0.5 wt.% at which the composite exhibited 44.8 % and 113 % improvements in the compressive and direct tensile strengths, respectively, relative to the control mix at 28 days. These improvements are attributed to the production of crystalline CSH and sheet-like CH induced by the addition of ZIF-67 nanoparticles. The results also revealed that the dry density increased while the water absorption and total porosity decreased with increasing the nanoparticle content. A calorimetry heat flow test revealed that the addition of ZIF-67 nanoparticles decreased the time needed to reach the silicate and aluminate states while increasing the maximal heat flow. The findings reported in this study could lead to a new industrial application where improved mechanical and hydration properties of cement-based materials are achieved through the addition of tiny fractions of ZIFs nanoparticles.