Reduction of the Cement Content by Incorporation of Fine Recycled Aggregates from Construction and Demolition Waste in Rendering Mortars

Sara Jesus,Cinthia Maia Pederneiras,Catarina Brazão Farinha,Jorge De Brito,Rosário Veiga

doi:10.3390/infrastructures6010011

Sara Jesus, Cinthia Maia Pederneiras + Show 3 more

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https://doi.org/10.3390/infrastructures6010011

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Abstract

The construction sector is responsible for one third of the total wastes produced in the EU. Finding solutions for the reuse or recycling of these wastes is one of the major environmental concerns of modern times. The replacement of sand or cement in specific construction materials, such as concrete or mortars, is a possible solution for these wastes’ management. By using construction and demolition wastes in construction materials, namely on buildings, the cycle of circular economy is closed, increasing the life cycle of the wastes in the same sector. In this research, a reduction of cement content in rendering mortars is analysed. This reduction is achieved by a decrease of the cement/aggregate ratio simultaneously with the incorporation of very fine recycled aggregate from construction and demolition waste. Two recycled aggregates were studied: recycled concrete aggregate (RCA) and mixed recycled aggregate (MRA). The fresh and hardened state properties of the mortars were analysed. Several tests were carried out to evaluate the mortars’ performance, such as mechanical strength tests, water absorption tests, drying tests and shrinkage. It was noticed that the incorporation of RCA led to a better behaviour than in the reference mortar, in terms of mechanical strengths and protection against water.

Highlights

These mortars exhibited improvements in most of the properties compared to the reference mortar, regarding mechanical strength and water absorption by capillarity
These enhancements are attributed to a filler effect and the presence of non-hydrated cement in the waste particles, which could prevail over the downside of cement content reduction
At 90 days, recycled concrete aggregate (RCA) 1:5 showed an increase of 17% and 34% in terms of the compressive and flexural strength, respectively, relative to the reference mortar at 1:4 volumetric ratio

Summary

Introduction

Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Cement is the most used binder in the production of mortars and concrete. Cement manufacture produces over 5–7% of the world’s total CO2 emissions [1]. Clinker production is responsible for half of these emissions. In order to search for strategies to reduce the energy consumption of the cement industry, studies have been developed to minimize the volume of cement. Replacing clinker with other supplementary cementitious materials, such as fly ash, slag, silica fume and pozzolans, has been applied. Several studies investigated other approaches to reduce cement-related emissions

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