COMPACTION CHARACTERISTICS AND CBR OF SLUDGE BLENDED WITH RECYCLED CLAY BRICKS FOR ROAD SUBGRADE APPLICATION

Abstract

Reuse and recycling of non-hazardous construction and demolition waste and industrial byproducts
in the construction industry is vital to promote environmentally sound waste management. In particular, the
effective utilization of sludge and waste clay bricks is greatly required in developing countries. This paper studied
compaction characteristics and the California bearing ratio (CBR) of water treatment sludge (WTS) blended with
clay brick aggregates for the road subgrade application. Raw and waste clay bricks from Vietnam were used for
preparing clay brick (CB) and recycled clay brick (RCB) aggregates of three different particle sizes, Coarse 10–
30 mm, Graded 2–30 mm, and Fine 2–10 mm. In addition, fine residues of clay bricks with a size of < 2 mm were
tested. WTS sieved under 2.0 mm blended with CB/RCB aggregates with different mixing proportions (f) were
used for compaction and CBR tests in the laboratory. Results showed that the measured maximum dry densities
(MDD) were dependent solely on mixing proportion f and increased linearly with f irrespective of blended fractions
of CB/RCB aggregates. Unlike MDD, the measured CBR was dependent on both f and blended fractions.
Especially, the WTS blended with coarse and graded fractions with a range of 60  f  80% showed a significant
improvement in CBR (>100%). Due to its limited particle breakage and high CBR, the WTS blended with graded
CB/RCB aggregates was preferable for the road subgrade application.