Study on the influence of attached mortar content on the properties of recycled concrete aggregate

Abstract

Recycled concrete aggregates mainly differ from natural aggregates in that they are composed of two different materials: natural aggregate and cement mortar attached. There is no general study about the quantitative influence of mortar content on other properties of the recycled aggregate. The objective of this study has been to obtain experimental relationships between the attached mortar content and other recycled aggregate properties. The present research program, in which concrete has been produced with different ratios of admixtures (25%, 50% and 75%) of mortar with fine recycled concrete aggregates, has been divided in five parts: particle size analysis, slump, compressive strength, density and absorption carried out and also from literature review. From particle size distribution obtained a fraction suitable for FRC should be smaller than 4 mm and the percentage of particles smaller than 0.063 mm. Besides that, slump for substitution concrete mix shows decreases (75% attached mortar value slump 30 mm). The results obtained for the 28 days compressive strength of that substitution concrete mix possesses higher (38.5 MPa) compare than NC (36 MPa). All test cubes results are acceptable according concrete Grade 20 which means all specimens should have compressive strength higher than 20 MPa. This increase was due the greater water absorption of the substitution ratio (4.4% vs. 2.7%). Then, absorption and density results are related. The lower density 2069.52 kg/m³ for 75% mortar content compare Average value for density of normal aggregate, set on 2236.70 kg/m³ respectively. The higher amount of attached mortar, the lower the density is.