Study on High-degree Recycled Aggregate for Concrete

本文介绍了一系列研究结果，以确定加热研磨法制备的高再生骨料的质量及其对普通混凝土和自密实混凝土的影响。采用加热研磨方法制成的骨料颗粒不粘附砂浆，满足日本建筑标准规范JAS5对钢筋混凝土工程中普通骨料的要求。机械粉磨再生骨料不能满足JAS5对普通骨料的要求，烘干比重小于2.4g/cm3，砂浆粘结，吸水率大于4.0%，对混凝土的干燥收缩和耐久性能造成不利影响。当烘箱干燥比重为2.5g/cm~3，吸水率为3.0%时，粘结砂浆的最大允许掺量为15%。含高浓度再生银…的混凝土具有较高固体体积百分比的集料与河流砾石具有与碎石相同的强度和耐久性。混凝土的含水率和干缩低于碎石混凝土，弹性模量高于碎石混凝土。与碎石混凝土相比，高再生骨料具有较高的流动性、较低的胶凝材料掺量、较低的超塑化剂掺量、较低的干缩率和较高的弹性模量，适用于自密实混凝土。加热、粉磨过程中产生的细度为400m2/kg的副产粉可作为自密实混凝土的外加剂，对混凝土质量无明显影响。通过一系列试验研究了高质量再生骨料混凝土在普通混凝土和超塑高性能混凝土上的性能。与相同坍落度的碎石混凝土相比，高质量再生骨料混凝土的含水率较低。抗压强度与水灰比相同的河流砾石强度相当，比碎石强度低10%。与碎石相比，碎石的抗拉强度和弹性模数较高，干缩率较低。较少

This report presents the results of series of studies conducted to determine the quality of high degree recycled aggregate made with heating & grinding method and its effects on normal and self-compacting concrete.High-degree recycled aggregates, made with heating and grinding method and free of adhered mortar on aggregate particles, satisfied the requirements for normal aggregates of Japanese Architectural Standard Specification JASS 5 for Reinforced Concrete work. Recycled aggregates, made with mechanical grinding method did not meet with the requirement of JASS 5 for normal aggregate, oven dry specific gravity being less than 2.4g/cm^3 and water absorption being higher than 4.0%due to adhered mortar, which causes deteriorating effects on drying shrinkage and durability of concrete. The allowable maximum value of adhered mortar content was found to be 15% for the specified oven dry specific gravity of 2.5g/cm^3 and water absorption of 3.0%. Concrete containing high-degree recycled ag … More gregates with higher percentage of solid volume as much as river gravel has the equivalent strength and durability as those with crushed stone. And water content and drying shrinkage were lower and modulus of elasticity of concrete was higher than those of crushed stone concrete. High-degree recycled aggregate was found to be applicable for self-compacting concrete, with higher fluidity, lower binder content, lower dosage of super-plasicizer, lower drying shrinkage and higher modulus of elasticity than those of crushed stone concrete. By-product powder with the fineness of 400m^2/kg generated in the process of heating & and grinding can be applicable as additives for self-compacting concrete without significant adverce effects on concrete quality.Series of experimental studies were carried out to determine the properties of concrete containing high quality recycled aggregates on normal concrete and super-plasticized high-performance concrete. High quality recycled aggregate concretes showed lower water content than those with crushed stone of the same slump. Compressive strengths were equivalent to those with river gravel of the same water cement ratio and were 10% lower than those with crushed stone. Tensile strengths and moduli of elasticity were higher and drying shrinkage were lower than those with crushed stone. Less