Effects of pre-treated recycled tire rubber on fresh and mechanical properties of concrete

Abstract

This thesis, generally, aims to explore the potential utilization of waste crumb tires in various concrete mixes for the production of light weight and non-structural concrete to study the structural behavior of concrete, and to help partially solving environmental problem produced from disposing waste tires. As known that the strength of concrete mainly depends on properties of materials mainly coarse and fine aggregate used in mix, and depends on the adhesion between these materials and cement paste, so this thesis aims to investigate many methodologies to improve the bonding force between crumb rubber and cement baste, by making pre- treatment for rubber surface. The necessary laboratory tests were done on fine aggregate (sand), coarse aggregate and cement, and many methods of pre-treatment were investigated such as Na OH pre-treatment, mortar pre-treatment and pre-treatment with bonding agent to increase the bonding force between crumb rubber and cement baste, several tests were made on fresh and hardened concrete, like slump, compressive strength, splitting tensile strength, unit weight and impact strength. The results show that the last method give the best results. Fine aggregate (sand) and coarse aggregate (size3) were replaced using volumetric method by non-treated crumb rubber tires with 0, 10, 20, and 30% replacements for the various mixes. And then many tests were made on fresh and hardened concrete, like slump, compressive strength, splitting tensile strength, unit weight and impact strength, and then Fine aggregate (sand) and coarse aggregate (size3) were replaced using volumetric method by (mortar and bonding agent) pre-treated crumb rubber tires with 0, 10, 20, and 30% replacements for the various mixes, and then many tests were made on fresh and hardened concrete, like slump, compressive strength, splitting tensile strength, unit weight and impact strength. The study shows that the slump, compressive strength, splitting tensile strength, unit weight and impact strength decreased as the percent replacement by non-treated crumb tires increased, were when pre-treated crump rubber used the slump, compressive strength, splitting tensile strength and unit weight decreased as the percent replacement by pre-treated crumb tires increased but the decrease was less than in case of non-treated rubber, were it improvement in impact strength when the replacement ratio was 10% then it was decreased as the replacement ratio increased. Finally, it is recommended to use waste crumb tires rubber with replacement ratio not more than 20% to produce light weight concrete that can be used, for non-structural elements, such as floor ribs, partitions, back stone concrete, concrete blocks, and other non-structural uses.