Effects of zeolitic imidazolate framework-8 nanoparticles on physicomechanical properties and microstructure of limestone calcined clay cement mortar

The limitations of limestone calcined clay cement (LC³) include its low mechanical strength and high drying shrinkage, in addition to its durability, which has not been addressed well in previous studies. Therefore, the objective of the present study was to investigate the feasibility of enhancing the durability and physical and mechanical properties of LC³ mortar by incorporating zeolitic imidazolate framework-8 (ZIF-8) nanoparticles. Six mixes of LC³ mortar with 0, 0.1, 0.3, 0.5, 0.7, and 0.9 wt% ZIF-8 were prepared and tested. The microstructure of the LC³-ZIF-8 mortar was characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), and Raman spectroscopy. The optimal ZIF-8 content was 0.5 wt%, at which the workability was significantly reduced, and the tensile and flexural strengths were increased. Although the LC³-ZIF-8 mortar exhibited a lower compressive strength than the unmodified LC³ mortar, the former had higher flexural and tensile strengths because of the positive effect of ZIF-8 on promoting calcium hydroxide (CH) and monocarboaluminate (Mc). These findings were consistent with the SEM, XRD, and Raman spectroscopy results. The water absorption and drying shrinkage rates of the LC³-ZIF-8 mortar were lower than those of the unmodified LC³ mortar owing to the modification of the LC³ mortar pore structure upon the addition of ZIF-8 nanoparticles. This study provides a better insight into the feasibility of utilizing ZIF-8 nanoparticles as reinforcement for LC³-based materials.