Caracterização de agregados de resíduos de construção e demolição reciclados e a influência de suas características no comportamento de concretos. / Characterisation of recycled aggregates from construction and demolition waste and the influence of their characteristics on concrete mechanical performance.




Construction and demolition waste (CDW) recycled aggregates are not largely used in concrete due to CDW composition heterogeneity and CDW recycled aggregate physical property variability from visual classification and hand sorting of proposed standards that provide insufficient relation between the aggregate characteristics and concrete performance. This thesis aims to identify CDW recycled aggregate characteristics that influence the concrete mechanical performance. The experimental design was divided in three stages: a) detailed chemical and mineralogical characterization of three representative CDW recycled aggregate samples, b) characterization of the physical properties of the coarse CDW recycled aggregates separated by heavy media as well as the composition in terms of chemical, mineralogical, and visual phases, and c) the influence of the coarse CDW recycled aggregate separated by heavy media on concrete mechanical performance. The following methods were used: particle size distribution, chemical analysis by XRF, mineralogical analysis by XRD, soluble fraction in chloride acid leaching assay, thermal analysis, sequential heavy media and gravity separation, hand sorting, bulk specific gravity and water absorption, concrete mix design and its compressive strength and elastic modulus using the CDW recycled aggregates. In conclusion, CDW recycled aggregate porosity controls concrete mechanical performance formulated with constant cement and water relation. The concrete mechanical performance is related to bulk specific gravity of CDW recycled aggregates separated by density, including to the sum of binder and red ceramic content. Heavy media and gravity separation is efficient to separate CDW recycled aggregates in bulk specific gravity groups, producing concrete with similar concrete mechanical behavior and water absorption. Cutting density in 2.2-2.3 g/cm³ seems to be efficient since the aggregates with the upper density have high rock content resulting concrete mechanical performance similar to that produced using natural aggregates. Mass distribution in density separation could be a simple and fast method to classify CDW recycled aggregate and to control concrete mechanical performance. The coarse and sand fraction of CDW recycled aggregates had more than 50% in mass of rocks and ceramics, with quite similar main oxide contents in chemical composition. However, the contents changed in fine fraction (lower than 0.15 mm) whose binder content and clay minerals are in majority (upper to 77% in mass). The origin of CDW recycled aggregate and comminution influenced in mass distribution of sequential density separation. In Itaquera (São Paulo), the mass distribution upper to 2,2 g/cm³ was around 70%.


caracterização tecnológica de minérios resíduos de construção quality control concreto construction and demolition waste controle da qualidade recycled aggregates applied mineralogy recycling plants agregados usinas de reciclagem de resíduos urbanos concrete

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