Sivamani Jagan, Renganathan Neelakantan Thurvas
Department of Civil Engineering, Kalasalingam Academy of Research and Education, Anand Nagar, Krishnankoil, Tamil Nadu, 626 126, India.
Environ Sci Pollut Res Int. 2022 Dec;29(57):85869-85882. doi: 10.1007/s11356-021-14420-5. Epub 2021 May 19.
To overcome the scarcity of river sand and dumping of construction and demolition wastes, the fine recycled aggregate (FRA) collected from C&D wastes is being utilized as a replacement to river sand. Many earlier studies reported that the higher water absorption of fine recycled aggregate and weak interfacial transition zone (ITZ) resulted in the development of the concrete with less strength and durability requirements. This study surmounts the above two factors through pre-saturation and a two-stage mixing approach (TSMA) technique. The concrete mixes prepared at 0.45 w/c ratios with 0%, 25%, 50%, and 100% of FRA were evaluated through hardened properties such as compressive strength, split tensile strength, flexural strength, and durability properties such as water absorption, sorptivity, shrinkage, rapid chloride penetration, and carbonation tests. The results indicate that the optimum level of replacement of fine recycled aggregate was 25% and the increase of fine recycled aggregate decreases the strength and durability properties. However, increased curing of concrete resulted in better strength and durability properties. The strength of the concrete was increased by 12% at 28 days and 17.46% at 90 days by two-stage mixing approach. The water absorption, porosity, shrinkage, chloride penetration, and carbonation of two-stage mixing approach was decreased by 7.45%, 15.38%, 16.57%, 18.18%, and 13.51% compared to normal mixing approach. Microstructural investigations show improvement in the interfacial transition zone with two-stage mixing approach compared to normal mixing approach.
为克服河砂短缺以及建筑与拆除废弃物倾倒问题，从建筑与拆除废弃物中收集的细再生骨料（FRA）正被用作河砂的替代品。许多早期研究报告称，细再生骨料吸水率较高以及界面过渡区（ITZ）薄弱，导致所制备的混凝土强度和耐久性达不到要求。本研究通过预饱和和两阶段搅拌法（TSMA）技术克服了上述两个因素。对水灰比为0.45、细再生骨料取代率分别为0%、25%、50%和100%的混凝土混合料进行了抗压强度、劈裂抗拉强度、抗弯强度等硬化性能以及吸水率、吸水系数、收缩率、快速氯离子渗透和碳化试验等耐久性性能的评估。结果表明，细再生骨料的最佳取代水平为25%，细再生骨料用量增加会降低强度和耐久性性能。然而，增加混凝土养护时间可提高强度和耐久性性能。采用两阶段搅拌法，混凝土在28天龄期时强度提高了12%，在90天龄期时提高了17.46%。与常规搅拌法相比，两阶段搅拌法的吸水率、孔隙率、收缩率、氯离子渗透和碳化分别降低了7.45%、15.38%、16.57%、18.18%和13.51%。微观结构研究表明，与常规搅拌法相比，两阶段搅拌法使界面过渡区得到了改善。
