Influence of Pozzolan, Slag and Recycled Aggregates on the Mechanical and Durability Properties of Low Cement Concrete.

Eliana Soldado,Hugo Costa,Eduardo Júlio,Ricardo Do Carmo,Ana Antunes

doi:10.3390/ma14154173

Abstract

The sustainability of the construction sector demands the reduction of CO2 emissions. The optimization of the amount of cement in concrete can be achieved either by partially replacing it by additions or by reducing the binder content. The present work aims at optimizing the properties of concrete used in the production of reinforced concrete poles for electrical distribution lines, combining the maximization of compactness with the partial replacement of cement by fly ash, natural pozzolans, and electric furnace slags. Natural aggregates were also partially replaced by recycled ones in mixtures with fly ash. Two types of concrete were studied: a fresh molded one with a dry consistency and a formwork molded one with a plastic consistency. The following properties were characterized: mechanical properties (flexural, tensile splitting, and compressive strengths, as well as Young’s modulus) and durability properties (capillary water absorption, water penetration depth under pressure, resistance to carbonation, chloride migration, and concrete surface resistivity). The service life of structures was estimated, taking the deterioration of reinforcement induced by concrete carbonation or chloride attack into account. Results revealed that mixtures with fly ash exhibit higher mechanical performance and mixtures with fly ash or pozzolans reveal much higher durability results than the full Portland cement-based mixtures.

Highlights

In recent years, there has been growing concern about environmental sustainability and global warming causes and effects
The following aggregates were used in the mixtures: fine siliceous sand 0/1 mm; medium siliceous sand 0/4 mm; crushed limestone gravels with two size fractions, 2/5 mm and 6/12 mm; recycled concrete aggregates (RA), from the concrete poles production waste, with two different size fractions (RA1/8 mm, for BT mixtures; RA4/16 mm, for MT mixtures), which were incorporated in 20% of volume replacement
As the results show, the flexural strength was not affected by the incorporation ration of 20 % of RA, presenting similar values to those of mixtures with fly ash and natof 20 % of RA, presenting similar values to those of mixtures with fly ash and natural ural aggregates, showing the same trend of results as those described in other studies aggregates, showing the same trend of results as those described in other studies [67,68]

Summary

Introduction

There has been growing concern about environmental sustainability and global warming causes and effects. The same association proposes measures that will lead to a reduction in CO2 emissions of the production process of up to 3.5%, in 2030, and 8%, in 2050. The replacement of natural aggregates with recycled aggregates is a measure that promotes the sustainability and the circular economy, minimizing the environmental impact and excessive extraction of non-renewable resources [3]. This replacement is an urgent measure, as the construction sector is a major consumer of natural resources and the global aggregate production went from 21 billion tons in 2007 to 40 billion tons in 2014 [4]

Methods

Discussion

Conclusion