Research paper The development of unfired clay building material using Brick Dust Waste and Mercia mudstone clay J.E. Oti ⁎, J.M. Kinuthia, R.B. Robinson School of Engineering, Faculty of Computing, Engineering and Science, University of South Wales, Pontypridd CF37 1DL, UK abstract article info Article history: Received 21 June 2013 Received in revised form 18 September 2014 Accepted 20 September 2014 Available online 11 October 2014 Keywords: Brick Dust Waste Unfired clay bricks Soil stabilisation Mercia mudstone clay Ground Granulated Blastfurnace Slag Freezing and thawing This work reports the potential of using Brick Dust Waste (BDW) as a partial substitute for clay in the develop- ment of unfired clay building materials (brick, block and mortar). BDW is a waste material from the cutting of fired clay bricks. There are various reasons necessitating the cutting of bricks — corner bricks, construction of chimneys, and other uses needing bricks of various shapes and sizes. This results in the disposal of BDW as an environmental prob- lem of concern. In order to investigate the clay replacement potential of BDW, four types of mixes were designed at varying BDW replacement levels — 5%, 10%, 15% and 20%. Ground Granulated Blastfurnace Slag, an industrial by-prod- uct from steel manufacture was activated using quick lime and the mixture was used to stabilise Mercia mudstone clay for unfired clay production. The 56 day compressive results using cylinder test specimens showed a significant strength gain (up to 2.1 N/mm 2 ). Overall, the results suggest that it is possible to develop unfired clay building material using up to 20% BDW as partial substitutes for primary clay. Crown Copyright © 2014 Published by Elsevier B.V. All rights reserved. 1. Introduction In order to boost environmental technologies while strengthening economic growth and competitiveness, the development of products using recycled and secondary raw materials as an alternative to primary raw materials should be encouraged worldwide. This will preserve natural resources while reducing waste to landfill. There has been a number of efforts to reduce the use of the virgin raw material (clay soil), and conventional binders for unfired clay building material devel- opment (Galán-Marín et al., 2010; Kinuthia and Nidzam, 2011; Oti, 2010; Oti and Kinuthia, 2012). The emphasis is therefore in the use of virgin materials only when the alternative of recycled materials for stabilised building product manufacture is not available. Previous work by Oti and Kinuthia (2012) used Lower Oxford Clay for unfired clay building material production. The study combined fired and unfired clay technologies and also combined energy use and carbon dioxide emission for the evaluation of unfired clay bricks relative to those bricks used in conventional construction; this is an attempt to come up with one parameter rating. Kinuthia and Nidzam (2011) reported on the potential of utilising Brick Dust Waste (BDW) in combi- nation with Pulverised Fuel Ash. The results showed that partial substi- tution of BDW with PFA resulted in a stronger material compared to using BDW on its own. Galán-Marín et al. (2010) reported on the possi- bility of producing building material using stabilised soils with natural polymers and fibres; the outcome of the work showed that the addition of fibre doubles the soil compression resistance. Regardless of the mate- rials, test methods and specimens used, the investigators conclude that the use of various waste and by-product materials for stabilised clay building material production has high environmental benefits and will facilitate best practice in waste management and waste reduction. This paper reports on investigative work aimed at developing stabilised clay building material using Brick Dust Waste (BDW) and Mercia mudstone clay. The overall aim is to capitalise on the already identified high cementitious potential BDW as a pozzolan, to enhance the strength of a blend by using up to 20% BDW as partial substitutes for Mercia mudstone clay (primary clay material). In order to explore further enhancement of the benefits, lime was only used as an activator to Ground Granulated Blastfurnace. The work reported on this paper will potentially offer a step-change in development of unfired clay building material beyond current knowledge and provide a means to enhance ‘green growth’ strategies. Brick Dust Waste and filter cake waste, glass waste, concrete wastes are largely inert waste and they make up a huge proportion of the 24.4 million tonnes of construction and demolition waste that went to the landfills in England and Wales in 2008 (DERA, 2012). The re-use of Brick Dust Waste within the building industry will help to conserve the dwindling landfill resources worldwide. This paper has significant valuable data for researchers in the field of sustainable construction material development and other related dis- ciplines. The commercial private sector will also benefit from this paper Applied Clay Science 102 (2014) 148–154 ⁎ Corresponding author. Tel.: +44 1443 483452; fax: +44 1443 48345. E-mail address: jonathan.oti@southwales.ac.uk (J.E. Oti). http://dx.doi.org/10.1016/j.clay.2014.09.031 0169-1317/Crown Copyright © 2014 Published by Elsevier B.V. All rights reserved. Contents lists available at ScienceDirect Applied Clay Science journal homepage: www.elsevier.com/locate/clay