Chen Shujun, Kong Xiangzhi, Li Shuangxi, Wei Bo
College of Water Conservancy and Civil Engineering, Xinjiang Agricultural University, Urumqi 830052, China.
China Institute of Water Resources and Hydropower Research, Beijing 100038, China.
Materials (Basel). 2025 Apr 2;18(7):1618. doi: 10.3390/ma18071618.
As part of this study, mechanical property tests were carried out at different stages with different curing temperatures to elucidate the effect of temperature on the mechanical properties of concrete. The curing temperatures were laboratory curing temperature (standard curing at 20 °C) and variable temperature curing (simulated site ambient temperature curing) according to the actual temperature of previous construction sites. The compressive strength, split tensile strength, axial tensile strength, and modulus of elasticity values were tested, and the growth rates were calculated. According to previous experiments, the maturity indexes under two kinds of maintenance conditions were calculated based on the N-S maturity formula, F-P equivalent age calculation formula, and D-L equivalent age calculation formula proposed by the maturity theory. Moreover, logarithmic function, exponential function, and hyperbolic function fitting were carried out using the fitting software to study the developmental relationship between strength and maturity. The physical phase analysis of low-heat cement was performed using XRD and simultaneous thermal analysis, and pore structure analysis was conducted using the mercuric pressure method (MIP). We also conducted an SEM analysis of hydration products and the micromorphology of low-heat cement with 25% fly ash. Energetic spectroscopy analyzed the elemental content. In this study, it was found that temperature has a significant effect on the mechanical properties of concrete, with temperature having the greatest effect on splitting tensile strength. The strength of low-heat silicate cement concrete increases with maturity. The highest correlation coefficient was based on the hyperbolic function fit in the F-P equivalent age. The improved development of concrete strength in the later stages of the two curing conditions in this test indicates that low-heat cement is suitable for use in hydraulic tunnels. The low-heat cement generates a large number of C-S-H gels via CS in the late stage, filling the internal pores, strengthening the concrete densification to make the structure more stable, guaranteeing the late development of concrete strength, and imparting a micro-expansive effect, which is effective for long-term crack resistance in hydraulic lining structures.
作为本研究的一部分，在不同阶段采用不同养护温度进行力学性能试验，以阐明温度对混凝土力学性能的影响。养护温度分为实验室养护温度（20℃标准养护）和根据以往施工现场实际温度的变温养护（模拟现场环境温度养护）。测试了抗压强度、劈裂抗拉强度、轴心抗拉强度和弹性模量值，并计算了增长率。根据以往试验，基于成熟度理论提出的N-S成熟度公式、F-P等效龄期计算公式和D-L等效龄期计算公式，计算了两种养护条件下的成熟度指标。此外，使用拟合软件进行对数函数、指数函数和双曲线函数拟合，以研究强度与成熟度之间的发展关系。采用XRD和同步热分析对低热水泥进行物相分析，采用压汞法（MIP）进行孔结构分析。我们还对含25%粉煤灰的低热水泥的水化产物和微观形貌进行了SEM分析。能谱分析了元素含量。在本研究中，发现温度对混凝土力学性能有显著影响，其中温度对劈裂抗拉强度的影响最大。低热硅酸盐水泥混凝土的强度随成熟度增加。基于F-P等效龄期的双曲线函数拟合得到的相关系数最高。本次试验中两种养护条件后期混凝土强度的良好发展表明，低热水泥适用于水工隧洞。低热水泥在后期通过CS生成大量C-S-H凝胶，填充内部孔隙，增强混凝土密实度，使结构更稳定，保证混凝土后期强度发展，并具有微膨胀效应，对水工衬砌结构的长期抗裂有效。
