回收轮胎钢纤维再生骨料混凝土基本力学性能试验研究

混凝土的基本力学性能与破坏形态是反映试件在不同受力状态下承载能力与韧性的重要指标。为了研究回收轮胎钢纤维(RTSF)再生骨料混凝土的基本力学性能,试验设计了8组不同种类的混凝土试件。通过坍落度、含气量、立方体抗压、劈裂抗拉与抗折试验,系统的探究了RTSF体积掺量(0.25%、0.5%、0.75%和1.0%)和再生骨料取代率(质量分数分别为50%、75%和100%)对混凝土基本力学性能以及破坏形态的影响。研究表明:随着再生骨料取代率的升高,混凝土拌合物坍落度减小、含气量增大,各项力学性能均产生不同程度的降低;RTSF能够有效提高再生骨料混凝土的基本力学性能,且试件的破坏形态随RTSF掺量的增加呈现出明显的延性破坏特征。综合各项指标,当再生骨料取代率为50%时,RTSF体积掺量为0.5%的RTSF再生骨料混凝土力学性能最佳。其试件立方体抗压强度(28 d)较普通混凝土仅降低1.0%,而劈裂抗拉强度与抗折强度较普通混凝土分别提高9.6%和12.5%。此外其弯曲韧度指数I₅、I₁₀和I₂₀分别为普通混凝土的2.7倍、3.8倍和4.8倍。

Experimental Study on Basic Mechanical Properties of Recycled Tyre Steel Fiber Recycled Aggregate Concrete

The basic mechanical properties and damage modes of concrete are important indicators of the load-bearing capacity and toughness of the specimens under different stress conditions. To investigate the basic mechanical properties of recycled tyre steel fiber (RTSF) recycled aggregate concrete, 8 sets of concrete specimens of different types were designed for the test. The effects of RTSF volume fraction (0.25%, 0.5%, 0.75% and 1.0%) and recycled aggregate replacement rate(the mass fractions are 50%, 75% and 100%, respectively) on the basic mechanical properties and failure modes of concrete were systematically investigated by slump, gas content, cubic compressive, splitting tensile and flexural tests. The results show that with the increase of recycled aggregate replacement rate, the slump of concrete mixture decrease and the gas content increase, and the mechanical properties are reduced to different degrees. RTSF effectively improves the basic mechanical properties of recycled aggregate concrete, and the failure mode of the specimens shows obvious ductile damage characteristics with the increase of RTSF content. Comprehensive indicators, when the replacement rate of recycled aggregate is 50%, the mechanical properties of RTSF recycled aggregate concrete with RTSF volume content of 0.5% is the best. The cube compressive strength (28 d) of the specimens is only 1.0% lower than that of plain concrete, while the splitting tensile strength and flexural strength are 9.6% and 12.5% higher than that of plain concrete, respectively. In addition, the flexural toughness index I₅, I₁₀ and I₂₀ of the concrete are 2.7 times, 3.8 times and 4.8 times of that of the plain concrete, respectively.