High quality recycled aggregate concrete

Abukersh, Salem Ahmed

Abstract

Sustainable development is gaining popularity around the globe nowadays. Governments are under pressure, on many fronts, to embed sustainable development in policies, practice, and operations to secure the planet’s future. Adding to this, increased populations, and the need for more infrastructures, have unfortunately led to the unacceptable depletion of raw materials, increasing amounts of construction and demolition waste (C&DW) and accelerated deterioration of the natural environment in many places worldwide.

For the conservation of natural resources, reuse and recycling of C&DW is the most obvious way to achieve sustainability in the construction sector. Currently, recycled aggregate (RA) is produced from C&DW in modern recycling facilities, under good quality control provisions which could lead to improve its performance compared with the earlier days of recycling. In addition to C&DW, large amounts of industrial and mining by-products such as fly ash, slag, limestone powders, aggregate dust, etc. are dumped in landfills. Fly ash has been used successfully in concrete for a long time due to its numerous advantages across a wide range of properties, including aspects of durability. A concrete produced with the combination of PFA and RA i.e. recycled aggregate concrete (RAC) is obviously more sustainable and economical than conventional natural aggregate concrete (NAC).

To date, statistics show that a considerable proportion of the world’s RA is used for low-utility applications due to perceived risks and uncertainty over their performance formed as a result of previous history of use when RA was produced manually and low strength cement and higher water to cement ratios were used. Despite the advances in recycling, materials and concreting technologies, this impression prevails. However, to increase the use of RA, it is believed that the quality of RAC should be improved by chemical and mineral additives. For cost effectiveness, quality-improving additives should be abundant, safe, and inexpensive; PFA and new generation polymer-based superplasticizer (SP) are deemed to be a good option.

The aims of this study are to investigate the possibility of producing good quality RAC that could be used as a substitute for NAC in normal strength concrete members, and to study its fundamental properties. An attempt has been made to create superplasticized RAC concretes, in which new generation polymer-based SP and PFA produced to the latest European standards were used. PFA was used to partially replace fine aggregate and cement in ordinary and self-compacting concretes. The thesis also includes an investigation into the potential of utilising an aggregate by-product (red granite dust (RGD) in producing environmentally beneficial RAC.

The findings show that good performance RAC can be produced with the help of SP and PFA. The study also revealed that it is possible to utilise RGD to substitute up to 30% of cement without substantially influencing the performance of concrete, while also providing cost savings. Strengths and stifnesses of the ensuing RAC either with SP, PFA, or RGD were comparable, or better than, a wide range of counterpart NACs. The author’s produced RAC concretes can replace NAC concrete used unnecessarily for many applications including structural concrete.

Thesis Type	Thesis
Deposit Date	Oct 21, 2009
Peer Reviewed	Not Peer Reviewed
Keywords	Concrete; Recycled aggregate; Pulverised fuel ash; Superplasticizer; Structural properties; Chemical properties; Applications; Benefits;
Public URL	http://researchrepository.napier.ac.uk/id/eprint/2963
Award Date	2009-10

High quality recycled aggregate concrete

Abukersh, Salem Ahmed

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