Utilization of Construction Concrete Waste as Aggregate Substitutes in Normal Concrete Production

Abstract

The construction process frequently necessitates the demolition of existing structures, resulting in substantial
construction waste. A significant portion of this waste comprises demolition debris, particularly from concrete building
materials. This research aims to develop standard concrete by partially substituting conventional coarse and fine
aggregates with concrete waste materials. The substitutions involved replacing 25% and 50% of sand and gravel,
respectively, by weight, using a K300 concrete mix design. Adopting the SNI 03-2834-2000 method, the mix design for 1
cubic meter of concrete comprised cement (528 kg), sand (776.16 kg), gravel (807.04 kg), and water (205 kg). The
results indicated an average sample weight reduction, with the first sample at 12.91 kg, the second at 12.79 kg, and the
third at 12.77 kg. This weight decrease suggests that using waste as a partial aggregate substitute impacts concrete
density. Compressive strength tests revealed a reduction of 5.98% in the concrete containing a 25% waste mixture, with
average compressive strength declining from 307.22 kg/cm² to 288.94 kg/cm². A more pronounced reduction occurred in
the 50% waste mixture, where compressive strength decreased by 15.70% (from 307.22 kg/cm² to 259.06 kg/cm²). This
trend aligns with the understanding that higher waste content correlates with greater mechanical strength reduction, likely
due to the differing physical properties of waste materials, such as lower density, which impact overall concrete
performance, particularly in compressive strength.