*Article* **Experimental Evaluation of Untreated and Pretreated Crumb Rubber Used in Concrete**

**Hamad Hassan Awan <sup>1</sup> , Muhammad Faisal Javed 2,\*, Adnan Yousaf <sup>2</sup> , Fahid Aslam <sup>3</sup> , Hisham Alabduljabbar <sup>3</sup> and Amir Mosavi 4,5,6,\***


**Abstract:** The present research aims at evaluating the mechanical performance of untreated and treated crumb rubber concrete (CRC). The study was also conducted to reduce the loss in mechanical properties of CRC. In this study, sand was replaced with crumb rubber (CR) with 0%, 5%, 10%, 15%, and 20% by volume. CR was treated with NaOH, lime, and common detergent for 24 h. Furthermore, water treatment was also carried out. All these treatments were done to enhance the mechanical properties of concrete that are affected by adding CR. The properties that were evaluated are compressive strength, indirect tensile strength, unit weight, ultrasonic pulse velocity, and water absorption. Compressive strength was assessed after 7 and 28 days of curing. The mechanical properties were decreased by increasing the percentage of the CR. The properties were improved after the treatment of CR. Lime treatment was found to be the best treatment of all four treatments followed by NaOH treatment and water treatment. Detergent treatment was found to be the worse treatment of all four methods of treatment. Despite increasing the strength it contributed to strength loss.

**Keywords:** crumb rubber concrete; crumb rubber; NaOH treatment; lime treatment; water treatment; detergent treatment; concrete; compressive strength; materials; mechanical properties
