Effect of Supplementary Cementitious Material and Fine Recycled Aggregates on Shrinkage Properties of Self-Compacting Microconcrete

Abstract

An increase in the population has led to the progressive construction of infrastructures and buildings. This causes severe environmental problems, firstly high emissions of CO2 are caused in cement production; secondly, a high volume of construction and demolition waste is landfilled and thirdly, it is necessary to look for new, no natural resources for the production of construction materials. The objective of this work is to analyse the influence of fine recycled aggregates and high volumes of fly ash in the properties of high-performance self-compacting (SC) microconcrete. The experimental work presented in this paper was carried out in two phases. In phase 1, SC- microconcrete were produced with 100% of Portland cement, and natural sand was replaced by both mixed and ceramics recycled aggregates in 30% and 50%. In phase 2, SC- microconcretes were produced with the replacement of 50% of Portland cement by fly ash, and natural sand was replaced by both mixed and ceramics recycled aggregates in 30% and 50%. In each phase, the drying and autogenous shrinkage of all mortars was measured via their storage in a climate chamber after 24 hours of casting and the determining of properties during 90 days. In order to assess the influence of the shrinkage effect on the mechanical properties, the prismatic samples were also stored in a climatic chamber, and the compressive strength at several ages was determined in all of the SC mixtures. The results showed that the microconcretes produced employing mixed and ceramic fine aggregates achieved higher compressive strength and lower autogenous shrinkage. Although the C-N achieved the lowest drying shrinkage, the mixtures with 30% of CRA and MRA were found to have similar values. The employment of the CRA aggregates improved the drying shrinkage and compressive strength of the C-FA-N mixture.