Experimental Study of Naoh Pretreated Crumb Rubber Concrete as Substitute of Fine Aggregate

Accession of discarded scrap tires can cause serious environment and health dangers through air, water, and soil pollution. Crumb rubber could be used in concrete to replace fine aggregate partially. Unlike fine aggregate, the surface of crumb rubber is smooth and non-porous due to the presence of oil stains and the chemical nature of rubber. Therefore, pretreatment with sodium hydroxide has been introduced to eliminate substances from the surface of crumb rubber, causing voids on the rubber outer surface, resulting in a surface that is coarse and more porous than untreated rubber. However, the effect of NaOH concentration, along with the duration of time, has not been discussed. Therefore, in this study crumb rubber has been treated with different concentrated solutions of NaOH (0.1mol, 0.5mol, and 1M) for different durations of time (2 hours and 24 hours). Then mechanical performance of hardened concrete (compressive strength and split tensile strength) was used to study this impact. The results reveal that pretreatment affects strength negatively for low dosages of crumb rubber. Meanwhile, pretreatment for a high dosage of crumb rubber shows recovery of lost strength compared to untreated crumb rubber. A numerical relation in-between both mechanical characteristics has also been developed for crumb rubber concrete (CRC).