Quantifying the constraint effect of coarse aggregates on mortar shrinkage is essential for predicting the bulk shrinkage of concrete. This study investigated the formation and evolution of tensile strain/stress shells around coarse aggregate in concrete under dry conditions by using digital image correlation and lattice fracture modelling. The average constraint shell thickness and constraint index were proposed to quantify the range and degree of coarse aggregate constraint on mortar shrinkage. The results indicated that constraint range increased as size of coarse aggregates increased, with the growth rate of 0.079. The constraint degree of coarse aggregate is positively correlated with aggregate size and mortar drying shrinkage. Notably, the formation of drying-induced micro-cracks also consumes more drying shrinkage forces, resulting in lower bulk drying shrinkage in concrete. At last, a mathematical model was developed to predict the bulk drying shrinkage of concrete based on constraint index and then validated against experimental results.

中文翻译：

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干燥条件下粗骨料对混凝土砂浆收缩率约束的量化


量化粗骨料对砂浆收缩的约束效应对于预测混凝土的体积收缩至关重要。本研究通过使用数字图像相关性和晶格断裂建模，研究了干燥条件下混凝土中粗骨料周围拉伸应变/应力壳的形成和演变。提出了平均约束壳厚度和约束指数，以量化粗骨料约束对砂浆收缩的范围和程度。结果表明，约束范围随着粗聚集体尺寸的增加而增大，增长率为 0.079。粗骨料的约束程度与骨料粒度和砂浆干燥收缩率呈正相关。值得注意的是，干燥引起的微裂缝的形成也消耗了更多的干燥收缩力，从而降低了混凝土中的体积干燥收缩率。最后，建立了基于约束指数预测混凝土体积干燥收缩的数学模型，并结合实验结果进行了验证。