For thousands of years, bricks have been made from clay. The water treatment plant sludge
is extremely close to brick clay in chemical composition. So, the sludge could be a potential substitute
for brick clay. The water treatment process generates a sludge that must be disposed of in an
environmentally sound manner. The sludge generated in most of the treatment systems around the
world is discharged into the nearest watercourse, which leads to accumulative rise of aluminum
concentrations in water and human bodies. This practice has been linked to occurrence of Alzheimer’s
disease. Among all disposal options, the use of sludge in producing constructional elements is
considered to be the most economic and environmentally sound option. One of the most common
agricultural wastes, which contain high silica content, and might be incorporated with sludge in brick
manufacturing, is rice husk ash (RHA). So, this trend also provides an environmentally sound manner
to reuse rice husk ash (RHA). The study investigated the complete substitution of brick clay by water
treatment sludge incorporated with rice husk ash (RHA). In this study, three different series of sludge
to rice husk ash (RHA) proportions were studied, which exclusively involved the addition of sludge
with ratios 25, 50, and 75% of the total weight of sludge-RHA mixture. Each brick series was fired at
900, 1000, 1100, and 1200
o
C. The physical and mechanical properties of the produced bricks were
then determined and evaluated according to Egyptian Standard Specifications (E.S.S.) and compared to
control brick made entirely from clay. From the obtained results, it was concluded that by operating at
the temperature commonly practiced in the brick kiln, 75 % was the optimum sludge addition to
produce brick from sludge-RHA mixture. The produced bricks properties were obviously superior to
the clay control-brick and to those available in the Egyptian market.
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