The durability and functionality of concrete overlay repairs are highly dependent on the extent of cracking and crack widths, which are difficult to predict. This article presents an experimental and analytical investigation on restrained shrinkage of overlays made with rapid hardening mortar mixes reinforced with recycled fibres. The investigated parameters include cement type (calcium sulfoaluminate cement-CSA and calcium aluminate cement-RSC), overlay depth, bond condition and fibre dosage. Sixteen composite prisms were tested to determine shrinkage strains and cracking development over time. Both plain (RSC) and fibre reinforced (FRSC) overlaid prisms made of calcium aluminate cement developed multiple cracks in less than 16 h due to their high shrinkage values, but 60% lower crack widths developed in FRSC. An effective analytical model is derived to estimate the crack spacing of concrete overlays. As concrete crack width predictive models are shown to be deficient in predicting the crack width of materials with flexural hardening properties, a semi-empirical approach is adopted to quantify the effect of fibres in such matrices. The predicted crack widths are in a good agreement with the experimentally measured values. The suggested model is expected to make a contribution towards safer and more sustainable solutions for concrete repairs.

混凝土覆盖层修复的耐久性和功能性高度依赖于难以预测的开裂程度和裂缝宽度。本文介绍了用再生纤维增强的快速硬化砂浆混合物制成的覆盖层抑制收缩的实验和分析研究。研究的参数包括水泥类型（硫铝酸钙水泥-CSA 和铝酸钙水泥-RSC）、覆盖深度、粘结条件和纤维用量。测试了 16 个复合棱柱，以确定随时间推移的收缩应变和开裂发展。由铝酸钙水泥制成的普通 (RSC) 和纤维增强 (FRSC) 叠加棱柱由于其高收缩值，在不到 16 小时内就出现了多条裂缝，但在 FRSC 中，裂缝宽度降低了 60%。推导出一个有效的分析模型来估计混凝土覆盖层的裂缝间距。由于混凝土裂缝宽度预测模型在预测具有弯曲硬化特性的材料的裂缝宽度方面存在缺陷，因此采用半经验方法来量化此类矩阵中纤维的影响。预测的裂纹宽度与实验测量值非常吻合。建议的模型有望为更安全、更可持续的混凝土修复解决方案做出贡献。预测的裂纹宽度与实验测量值非常吻合。建议的模型有望为更安全、更可持续的混凝土修复解决方案做出贡献。预测的裂纹宽度与实验测量值非常吻合。建议的模型有望为更安全、更可持续的混凝土修复解决方案做出贡献。