A Review on Alkali-Silica Reaction Evolution in Recycled Aggregate Concrete.

Miguel Barreto Santos,António Santos Silva,Jorge De Brito

doi:10.3390/ma13112625

Abstract

Alkali-silica reaction (ASR) is one of the major degradation causes of concrete. This highly deleterious reaction has aroused the attention of researchers, in order to develop methodologies for its prevention and mitigation, but despite the efforts made, there is still no efficient cure to control its expansive consequences. The incorporation of recycled aggregates in concrete raises several ASR issues, mainly due to the difficult control of the source concrete reactivity level and the lack of knowledge on ASR’s evolution in new recycled aggregate concrete. This paper reviews several research works on ASR in concrete with recycled aggregates, and the main findings are presented in order to contribute to the knowledge and discussion of ASR in recycled aggregate concrete. It has been observed that age, exposure conditions, crushing and the heterogeneity source can influence the alkalis and reactive silica contents in the recycled aggregates. The use of low contents of highly reactive recycled aggregates as a replacement for natural aggregates can be done without an increase in expansion of concrete. ASR expansion tests and ASR mitigation measures need to be further researched to incorporate a higher content of recycled aggregates.

Highlights

Concrete is produced with materials extracted from nature and, the use of non-renewable natural resources for its manufacture has, over the years, become a sustainability problem
Methodology that currently exists on natural aggregate concrete (NAC) can be pursued on recycled aggregate concrete (RAC)
In the accelerated mortar-bar test method (AMBT), the aggregate is considered potentially deleterious if the average expansion of the mortar bar after 14 days of immersion in NaOH at 80 ◦ C is higher than 0.20%

Summary

Introduction

Concrete is produced with materials extracted from nature and, the use of non-renewable natural resources for its manufacture has, over the years, become a sustainability problem. The construction and rehabilitation of structures produces waste as well as the demolition of some older structures. This cycle will continue over the years due to the finite useful life of the structures; it is necessary to ensure an effective and sustainable destination for the construction and demolition waste. The use of recycled aggregates (RA) from concrete structures on a new concrete mix is pointed out as a contribution to sustainable construction criteria. More emphasis will be given to coarse RA

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