Experimental study on enhancing the main characteristics of crumb rubber concrete

The use of rubber particles as partial fine aggregate replacement to produce crumb rubber concrete (CRC) can have an adverse effect on some of its mechanical properties, such as strength. Researchers have used a range of methods to overcome the material deficiencies, however the results have often been contradictory and highly variable. In this paper, the effects of many different rubber chemical pre-treatments on CRC workability, compressive strength, tensile strength, and flexural strength were measured. The rubber pretreatments utilized chemicals such as Sodium Hydroxide (NaOH), Hydrogen Peroxide (H2O2), Sulfuric acid (H2SO4), Calcium Chloride (CaCl2), Potassium Permanganate (KMnO4), Sodium Bisulfite (NaHsO3), and Silane Coupling Agent. Soaking rubber particles in tap water or running them through water before mixing were also tried as pre-treatment of rubber particles. X-ray photoelectron spectroscopy (XPS) analysis and scanning electron microscope (SEM) imaging of some of the pre-treated rubber particles were carried out. The results showed that mixing rubber with dry cement before adding to the mix increased the compressive strength by up to 3%. Pretreatment using water was more effective than other chemicals in enhancing the CRC workability. Regardless of the treatment material type, the longer the time of the treatment the more cleaning of rubber occurred.