Unfired clay masonry bricks incorporating slate waste

This paper discusses the potential of using slate waste generated from roofing slate production in the UK in the manufacture of unfired clay masonry bricks. Ground granulated blast-furnace slag activated by lime and Portland cement were used to stabilise Lower Oxford Clay incorporating slate waste in the preparation of laboratory cylindrical test specimens. The specimens were moist cured at room temperature (20 +/- 2 degrees C) for between 3 and 90 days before testing for compressive strength. The drying and linear expansion behaviours of the test samples were assessed by means of moisture content measurement (at the age of testing) and linear expansion measurement after soaking the samples in deionised water. The strength of the cement-activated blended mixture was lower than that of the lime-activated mixtures. An environmental comparison of the unfired clay masonry bricks with mainstream construction (fired) bricks shows that the unfired clay bricks have good environmental characteristics over a range of important criteria. These results suggest that there is potential for using activated slag mixtures in the manufacture of bricks for low-cost environmentally friendly housing and energy-efficient masonry wall construction within the UK.