Obtenção de concreto leve utilizando agregados reciclados

Lightweight concrete can be obtained by replacing conventional aggregates by a lower density aggregate, such as expanded clay, which also present high porosity and high water absorption. These properties resemble those of recycled aggregates from construction waste, contributing to the achievement of a lightweight concrete. However, recycled aggregates have characteristics that make them very different: variable composition, low resistance to abrasion, more irregular shapes. This article analyses some properties of recycled coarse aggregates and their influence on the behaviour of lightweight concrete in fresh and hardened state. The study used two types of recycled coarse aggregates, one originating from concrete blocks with EPS (ARBCE) and another one from ceramic blocks (ARBC), with the purpose of understanding the variability of the materials characterising the composition of these aggregates in order to verify the feasibility of application of these aggregates in lightweight concrete. The aggregates were crushed by two different equipments (mortar mixer mill and hammer mill). The recycled aggregates obtained through these different crushing processes presented different size distribution and shapes. In spite of that, it was possible to produce the two recycled lightweight concretes using both aggregate types. The compressive strength at 28 days was between 9.0 and 13.0 MPa, pointing to their use in elements without any structural function, but applicable in building components of moderate strength (e.g. panels and blocks).

通过使用低密度集料替代传统集料，可制备轻质混凝土；膨胀黏土便是这类低密度集料的典型代表，其自身具备高孔隙率与高吸水率特性。该特性与建筑垃圾再生集料的特性相近，因此可用于制备轻质混凝土。然而再生集料也存在诸多差异化特性：成分波动较大、抗磨性能较差、形貌更为不规则。本文针对再生粗集料的多项性能及其对轻质混凝土新拌与硬化状态下性能的影响展开分析。本研究采用两类再生粗集料：一类源自掺有聚苯乙烯泡沫（EPS）的混凝土砌块（ARBCE），另一类来自陶瓷砌块（ARBC）；研究旨在明确构成此类集料的物料特性的波动规律，以验证将其应用于轻质混凝土的可行性。上述集料分别通过两种不同设备进行破碎：砂浆混合磨粉机与锤式破碎机。经不同破碎工艺制备得到的再生集料，其粒径分布与形貌均存在差异。尽管存在上述差异，仍可利用这两类集料分别制备出再生轻质混凝土。该类混凝土28天抗压强度介于9.0~13.0 MPa之间，表明其适用于非结构性构件，亦可应用于中等强度要求的建筑构配件（如板材与砌块）。