The accumulation of end-of-life tires generates significant environmental/economic/social problems worldwide; however, these tires can potentially be used in engineering applications when recycled as crumb rubber (CR). One possibility is to use CR as a replacement for river sand in concrete to reduce the disposal of CR and the use of sand as well as to improve some of concrete’s properties, such as thermal performance and carbon footprint at the expense of some compressive strength reduction. In this study, a novel and simple multivariable model was developed to predict the compressive strength reduction of rubberized concrete (RC) based on a dataset of 287 concrete mixtures from 38 different studies. The approach used in this study quantified the significance of the impact of 10 mix design variables on the evaluation of compressive strength reduction. The final model proposed in this paper considers six explanatory variables (i.e., volume replacement of sand by CR, CR quantity, fine aggregate quantity, coarse aggregate quantity, cement quantity, and water quantity) to predict the compressive strength reduction in which a logarithmic transformation was implemented to achieve a more precise model. The proposed model reached a coefficient of determination of 0.89, significantly better than other existing models with which the proposed model was compared, resulting in a highly accurate and yet easy-to-implement model. Finally, practical design considerations were provided to be used in concrete mix design or the design of minor structural elements.

中文翻译：

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配合比对橡胶混凝土力学性能的影响：针对设计规定的多变量预测模型

报废轮胎的累积在全球范围内产生了严重的环境/经济/社会问题；然而，这些轮胎在以粒状橡胶 (CR) 形式回收后可用于工程应用。一种可能性是使用 CR 作为混凝土中河砂的替代品，以减少 CR 的处置和沙子的使用，并改善混凝土的一些性能，例如热性能和碳足迹，但代价是抗压强度有所降低。在这项研究中，基于来自 38 项不同研究的 287 种混凝土混合物的数据集，开发了一种新颖且简单的多变量模型来预测橡胶混凝土 (RC) 的抗压强度降低。本研究中使用的方法量化了 10 个配合比设计变量对抗压强度降低评估的影响的显着性。本文提出的最终模型考虑了六个解释变量（即，CR 替代砂子的体积、CR 数量、细骨料数量、粗骨料数量、水泥数量和水量）来预测抗压强度降低，其中对数变换是为了获得更精确的模型而实施的。该模型的决定系数达到了 0.89，明显优于与该模型进行比较的其他现有模型，从而形成了一个高精度且易于实现的模型。最后，提供了用于混凝土配合比设计或次要结构元件设计的实际设计考虑因素。