Rubber tires present a serious disposal problem as millions of tires are discarded every year producing serious smoke pollution when burnt. The objectives of this research are to examine how recycled rubber from used tires affects properties of mixes of bituminous concrete, and to find optimum rubber content that will provide rubber-asphalt concrete mixtures with best properties. In current study, recycled rubber from used tires is used to modify characteristics of asphalt mixture (AM). Marshall mix design procedure was used to obtain optimum binder content (OBC) and to study impact of rubber on AM properties. Mixtures' moisture susceptibility was determined using Marshall immersion test and indirect tensile strength test. Scrap rubber at 0, 1, 2, and 3 % of total weight of mixture was mixed with crushed limestone or basalt aggregate. By total weight of mixture, asphalt binder (AB) was added at five different percentages (4.0, 4.5, 5.0, 5.5, and 6.0 %). Findings indicate that adding 1 % of rubber to a mixture of limestone and basalt yielded bituminous mixtures with best qualities overall. Increased air voids and flow and reduced unit weight, void in mineral aggregate, and stability has occurred by adding scrap rubber to mixes. Compared to limestone bituminous mixtures, basalt bituminous mixtures exhibit greater stability, unit weight, air voids, voids in mineral aggregate, smaller flow, and slightly smaller voids filled with bitumen. Dry specimens exhibit higher stability compared to wet specimens. Nevertheless, for both limestone and basalt bituminous mixtures at OBC, the flow of wet specimens is higher than that of dry specimens. For both limestone and basalt aggregate-bituminous mixtures, indirect tensile strength reduces as rubber concentration increases at OBC. Also, retained stability ratio (RST) and retained indirect tensile strength ratio (RTSR) in basalt mixtures at OBC is larger than those for limestone aggregate-bituminous mixtures at OBC.