Abstract:

As a biomass ash， the large-scale disposal of incense stick ash （ISA） remains a major challenge. Partially replacing cement with ISA is an effective strategy to achieve resource recovery and reduce the carbon footprint of cement-based materials. However， the low early-age activity of ISA easily leads to low early mechanical properties of cement-based materials. To solve this problem， microwave can be used to stimulate the early reactivity of ISA， thereby improving the mechanical strength of composite cementitious materials. In this study， composite cement pastes containing 0%~20% ISA by mass were prepared and were cured under two conditions： microwave （M） curing and microwave followed by water （MW） curing. The effects of ISA content and curing condition on the compressive strength， mineral composition， pore structure， and nanomechanical properties of cement pastes were systematically investigated. The results show that both M and MW curing can improve the early compressive strength of cement pastes with ISA. Moreover， M and MW curing significantly refine the pore structure of samples and densify the microstructure. At the nanoscale， M and MW curing promote the formation of calcium silicate hydrate （C-S-H） gel and the transformation of low density （LD） C-S-H gel to high density （HD） C-S-H gel. This study aims to promote the application of ISA and microwave curing in cement-based materials and provide theoretical support for the performance optimization and sustainable design of green building materials.

Key words: incense stick ash, cementitious material, microwave curing, mechanical property, microstructure, nanoindentation