Performance evolution of low heat cement under thermal cycling fatigue: A comparative study with moderate heat cement and ordinary Portland cement

As a promising and environmentally friendly cementitious material for mass concrete applications, the long-term performance evolution of low-heat cement (LHC) and moderate-heat cement (MHC) under the alternating environmental temperature remains unclear. To address this gap, a comprehensive comparative study based on laboratory acceleration test was conducted by evaluating the physicochemical properties and cracking behavior of LHC and MHC in comparison to ordinary Portland cement (OPC) following 1200 thermal cycles (TC) at temperatures ranging from 5 to 45 C. Cracking behavior is revealed by a quantitative identification analysis. The results indicate a negative linear relationship between porosity, crack density, and compressive strength, highlighting their competing mechanisms in determining the degree of damage under TC. TC sharply diminished the gel pores (<10 nm) and promoted the formation of capillary pores (50-1000 nm), which were the primary forms of pore coarsening observed. Notably, the different proportions of hydrated products such as HD-CSH, LD-CSH, and CH influence the toughness properties of the matrix and contribute to different resistances to cracking and the formation of cracks with varying fracture morphology, although they also impact the stability of the pore structure. Further analysis revealed different degrees of rehydration occurring within the first 200 cycles of both LHC and MHC, which contributed to the mitigation of performance degradation. Moreover, an increase in the water-to-cement (w/c) ratio had a tendency to coarsen the matrix and facilitate the formation of long and narrow cracks.