为研究养护龄期对风积沙混凝土孔结构的影响,采用不同掺量的风积沙替代河砂制备风积沙混凝土,探究风积沙掺量及养护龄期对其孔结构及强度发展的影响规律。试验以抗压强度作为宏观指标,对不同掺量不同龄期风积沙混凝土进行测量,微观方面通过NMR分析了风积沙混凝土内部孔隙结构,并利用SEM观察其内部微观结构变化。结果表明,随着养护龄期的增加,混凝土内部孔隙率逐渐降低,抗压强度呈现增长的趋势。相同养护龄期下随着风积沙掺量的增加,混凝土的抗压强度先增加后减少,风积沙掺量为25%时提升效果最好,28 d龄期时抗压强度分别为ASC-0组、ASC-50组、ASC-75组和ASC-100组的1.02、1.08、1.11和1.19倍。通过灰色关联分析发现束缚流体饱和度、无害孔占比与风积沙混凝土抗压强度关联度较高,建立的GM(1,3)模型可预测不同养护龄期下风积沙混凝土的抗压强度。

[Objective] Owing to its abundant availability, aeolian sand can be used in concrete production. To investigate the influence of curing age on the pore structure of aeolian sand concrete, concrete specimens are prepared by replacing river sand with varying amounts of aeolian sand, and the effects of aeolian sand content and curing age on the development of pore structure and compressive strength are explored. [Methods] In the experiments, compressive strength was used as a macroscopic indicator for aeolian sand concrete specimens with different aeolian sand contents at different curing ages. At the microscopic level, nuclear magnetic resonance (NMR) was employed to analyze the internal pore structure, including T₂ spectrum, porosity, free fluid saturation (MFFI), and bound fluid saturation (BVI). Scanning electron microscopy (SEM) was used to observe the internal microstructure and monitor structural changes in the concrete. [Results] Results showed that the internal porosity of concrete gradually decreased with increasing curing age, while the compressive strength increased correspondingly. At the same curing age, the compressive strength of concrete initially increased and then decreased as aeolian sand content increased. The optimal improvement occurred at 25% aeolian sand replacement. At 28 d age, the compressive strength of the concrete with 25% aeolian sand replacement was 1.02, 1.08, 1.11, and 1.19 times that of ASC-0, ASC-50, ASC-75, and ASC-100, respectively. SEM observations showed that microcracks and pores gradually decreased with curing age, and ASC-25 exhibited superior compactness among all mixtures. The T₂ spectrum displayed three to four peaks, with the first peak as the dominant component. As the curing age increased, the proportion of the first peak area gradually increased in all groups. At 14 d age, the first peak proportions of ASC-0, ASC-25, ASC-50, ASC-75, and ASC-100 were 89.7%, 92.68%, 88.74%, 86.66%, and 86.13%, respectively. The proportion of harmless pores gradually increased in each group. For ASC-25, the harmless pore proportion was 43%, 48%, 60%, 63%, and 66% at 7, 14, 28, 56 d, and 84 d, respectively. The internal pore structure of the concrete gradually became denser. For ASC-25, the bound fluid saturation values were 91.51%, 92.72%, 94.53%, 95.21% and 96.37% at 7, 14, 28, 56 d, and 84 d, respectively, with corresponding porosities of 3.00%, 1.65%, 1.25%, 1.22%, and 1.04%, respectively. [Conclusion] The gray correlation analysis indicates that bound fluid saturation and the proportion of harmless pores are strongly correlated with compressive strength, with correlation coefficients exceeding 0.8. The compressive strength predicted by the GM(1,3) model closely matches the experimental results, with a maximum residual of 0.44 MPa, and the relative errors are all within 5%. The established GM(1,3) model can effectively predict the compressive strength of aeolian sand concrete at different curing ages, providing a reference for practical engineering applications.