Effect of Molasses and Water-Cement Ratio on Properties of Recycled Aggregate Concrete

Despite recycled aggregate concrete (RAC) presenting economic and environmental benefits, it has inferior fresh and hardened state properties. Recycled coarse aggregates (RCA) obtained from demolished concrete demand more water to satisfy their absorption capacity than natural aggregates; therefore, concrete incorporating the higher volume of RCA leads to inferior properties. Using a suitable plasticizer, water demand of RAC can be reduced as noted by many researchers; hence, properties of RAC are improved. Moreover, sugarcane molasses is a by-product of sugar mills and has water-reducing properties; therefore, it can be used as a cheap substitute of conventional plasticizers. In this study, the influence of four different concentrations of molasses (0%, 0.25%, 0.50% and 1% by weight of cement) on the properties of RAC is investigated using three different water-cement (W/C) ratios (0.45, 0.50 and 0.55). Workability, fresh density, compressive strength, water absorption, sorptivity coefficient and chloride penetrations are investigated. The results encouraged the use of 0.25-0.50% molasses in RAC for maximum strength and durability. Blank and molasses-added mixes showed maximum strength and durability at 0.55 and 0.50 W/C ratios, respectively.