University of Birmingham
Carbonation behaviour of recycled aggregate
concrete
Silva, R.v.; Neves, R.; De Brito, J.; Dhir, Ravindra
DOI:
10.1016/j.cemconcomp.2015.04.017
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Silva, RV, Neves, R, De Brito, J & Dhir, R 2015, 'Carbonation behaviour of recycled aggregate concrete',
Cement and Concrete Composites, vol. 62, pp. 22-32. https://doi.org/10.1016/j.cemconcomp.2015.04.017
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Accepted Manuscript
Carbonation behaviour of recycled aggregate concrete
R.V. Silva, R. Neves, J. de Brito, R.K. Dhir
PII: S0958-9465(15)00089-X
DOI: http://dx.doi.org/10.1016/j.cemconcomp.2015.04.017
Reference: CECO 2511
To appear in:
Cement & Concrete Composites
Received Date: 4 October 2014
Revised Date: 24 April 2015
Accepted Date: 29 April 2015
Please cite this article as: Silva, R.V., Neves, R., de Brito, J., Dhir, R.K., Carbonation behaviour of recycled aggregate
concrete, Cement & Concrete Composites (2015), doi: http://dx.doi.org/10.1016/j.cemconcomp.2015.04.017
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1
Carbonation behaviour of recycled aggregate concrete
R. V. Silva
1
, R. Neves
2
, J. de Brito
3
and R. K. Dhir
4
1
PhD student in Civil Engineering, CERis-ICIST, Instituto Superior Técnico, Universidade de Lisboa, Av.
Rovisco Pais, 1049-001 Lisbon, Portugal; e-mail: rvpssilva@gmail.com
2
Professor, CERis-ICIST, Barreiro Technology School, Polytechnic Institute of Setúbal, R. Américo da Silva
Marinho, 2939-001, Barreiro, Portugal; e-mail: rui.neves@estbarreiro.ips.pt
3
Full Professor, CERis-ICIST, DECivil, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais,
1049-001 Lisbon, Portugal; Phone: (351) 218 419 709; e-mail: jb@civil.ist.utl.pt, Corresponding author
4
Professor of Concrete Technology, School of Civil Engineering, University of Birmingham, Edgbaston, Bir-
mingham B15 2TT UK; email: r.k.dhir@bham.ac.uk
ABSTRACT
This paper reviews the effect of incorporating recycled aggregates, sourced from construction
and demolition waste, on the carbonation behaviour of concrete. It identifies various influenc-
ing aspects related to the use of recycled aggregates, such as replacement level, size and ori-
gin, as well as the influence of curing conditions, use of chemical admixtures and additions,
on carbonation over a long period of time. A statistical analysis on the effect of introducing
increasing amounts of recycled aggregates on the carbonation depth and coefficient of accel-
erated carbonation is presented. This paper also presents the use of existing methodologies to
estimate the required accelerated carbonation resistance of a reinforced recycled aggregate
concrete exposed to natural carbonation conditions with the use of accelerated carbonation
tests. Results show clear increasing carbonation depths with increasing replacement levels
when recycled aggregate concrete mixes are made with a similar mix design to that of the
control natural aggregate concrete. The relationship between the compressive strength and
coefficients of accelerated carbonation is similar between the control concrete and the recy-
cled aggregate concrete mixes.
Keywords: Recycled aggregates, construction and demolition waste, carbonation, concrete,
durability, service life design.
2
1 INTRODUCTION
The rapid development of the construction industry and consumption of natural resources and
deterioration of the environment in several emerging economies have caused an unsustainable
development of the construction industry. For this reason, recycling construction and demoli-
tion wastes (CDW) is a vital step in environmental sustainability. However, for this to hap-
pen, changes in the management of construction and demolition activities would have to be
made in order to implement selective demolition as a replacement for conventional demoli-
tion. Selective demolition, also known as deconstruction in some sources, is the systematic
disassembly of buildings in order to maximize recovered materials reuse and recycling. While
the process of conventional demolition often leads to the mixing of potentially valuable mate-
rials and contamination of non-hazardous components, selective demolition allows the use of
these separated and uncontaminated materials in future applications.
The concept of selective demolition is still often seen by the construction and demolition indus-
tries as being of debateable economic benefit and little practical value. However, a detailed eco-
nomic analysis of conventional versus selective demolition [1] showed that in spite of the eco-
nomic viability of selective demolition depending largely on labour costs, tipping fees, and
market prices for recovered materials, it may ultimately be more profitable than the conven-
tional demolition approach. Furthermore, there are clear benefits from an environmental point
of view from using selective demolition, namely in a direct reduction in the material sent to
landfill [2, 3] as well as other environmental impacts specifically caused by climatic change,
acidification, summer smog, nitrification and amount of heavy metals [4]. These result from the
emission of a wide array of substances, all of which are known to be important pollutants.
The use of recycled aggregates (RA), as replacement for natural aggregates (NA), in construc-
tion applications has been considered as one of the most effective approaches for recycling
given materials from CDW, thus contributing to a greater sustainability in construction. In-
3
deed, extensive scientific research and development work on this subject has been carried out
over the last 40 years, which has been becoming increasingly complex, introducing several
new variables, in which the durability-related performance has also been considered.
The scope of this investigation was to bring together, analyse and evaluate the published in-
formation on the effect of several factors related to the use of RA on the carbonation behav-
iour of concrete. The data, collated from several studies, was subjected to a statistical analysis
in order to assess the relationship between carbonation resistance and compressive strength of
RAC and also utilized as input information on reinforced concrete degradation models to
evaluate RAC suitability as material for reinforced concrete.
2 RECYCLED AGGREGATES SOURCED FROM CONSTRUCTION
AND DEMOLITION WASTES
According to existing specifications [5-20], there are three main types of RA arising from
CDW, which, after being subjected to proper beneficiation processes in certified recycling
plants, are suitable for the production of structural concrete; these materials are crushed con-
crete, crushed masonry, and mixed demolition debris.
Some of these specifications [9, 14, 15, 17] have reached a consensus that, in order to be con-
sidered as recycled concrete aggregate (RCA), they must comprise a minimum of 90%, by
mass, of Portland cement-based fragments and NA.
RA sourced from crushed masonry, or recycled masonry aggregates (RMA), may include:
aerated and lightweight concrete blocks; ceramic bricks; blast-furnace slag bricks and blocks;
ceramic roofing tiles and shingles; and sand-lime bricks [21]. RMA are composed of a mini-
mum of 90%, by mass, of the summation of the aforementioned materials.
Aggregates acquired from mixed demolition debris, or mixed recycled aggregates (MRA), are a
mixture of the two main components obtained from the beneficiation process of CDW: crushed