Viscoelastic Measurements of Clay Suspensions and their Relationship to Strength of Unfired Clay Bricks with Almond Husk Additive

Engineered unfired clay bricks are an ecological alternative to overcome conventional construction materials’ inconvenience. This work investigates the rheological behavior of organo-silica suspensions, made from almond husk waste and illite clay, in relation to the compressive strength of unfired clay bricks incorporating the same waste. Selected proportions by weight of almond husk are 2, 5, 10, and 20 wt.%. Results from the compressive strength test show an improvement, of 8.98% in bricks with 2 wt.% waste content compared to the control sample, thanks to an increase in friction and the fiber bridging mechanism. Then, a progressively decrease in strength is recorded with the addition of waste. The decrease in strength is reported to be the creation of pores in the matrix, and loss of cohesion. It is found that the storage modulus, on a logarithmic scale, follows inversely the same trend of the compressive strength in previously prepared bricks. The results from the strength test and rheological test are linearly correlated. Strong coefficients of determination are found; R2=0.9809 (with 40 wt.% water content) and R2=0.9206 (with 50 wt.% water content). The findings from this study demonstrate the possibility of assessment and prediction of unfired bricks’ strength using rheometry.