Feras Al Adday, International Journal of Emerging Trends in Engineering Research, 8(5), May 2020, 1804– 1808 1804 ABSTRACT The need to provide commercial ideas to get rid of the rubber of car tires has become an urgent issue, especially adding to the various construction processes. Adding used tires (UT) to the concrete helps reduce landfill areas and declines the depletion of raw aggregate used in made the concrete mixtures. This research focuses on the study of the effectiveness of the use of UT in concrete mixtures according to the specifications of Jordan Construction, Where a fine aggregates retained on a sieve No. 16 have been replaced with UT. Considering keeping the same volume. It has been adapted replacement ratios of 50 and 100% of the fine aggregate. Hardened properties was studied to measure the value of compressive strength (VCS) after 7, 14 and 28 curing days. In addition to determine fresh property (Slump test) to study the efficiency of adding UT on workability. A 18 cubes of (10 x 10 x 10 cm) for compressive strength test and a 9 molds (50 x 10 x10 cm) for flexural strength test, in addition to a 9 cylinders (15 cm Dia. X 30 cm height) for tensile strength test, all samples were made at a different percentages of UT (0%, 50% and 100%), at water/cement ratio of 0.60. This study concluded that there is no inverse relationship with the increase in the percentage of UT, where the compressive strength at the 100 replacement ratio of UT was greater than 50%, the increase rate was around 19% at 100% of UT related to 50%. The results indicated that the workability value was not considerably affected, where the slump value was nearly equal to the various replacement ratios 0, 50, and 100%. 90, 100, and 100 mm respectively. Furthermore, a unit weight of used tires concrete mixes (UTCM) was reduced about 20% for 100% replacement and 10% for 50% replacement of UT related to normal concrete mixtures (0% UT). Key words: Crumb Rubber, Raw Aggregate, compressive strength, Rubberized concrete. 1. INTRODUCTION Currently, there is a huge amount of used tires (UT) deserted every year in landfills. The amount of used tires is estimated at about 275 billion in the United States and 180 billion annually in the European Union countries. The UT produce an actual ecological hazard, where prohibited disposal of UT is also a great fear [1]. UT can be added as a replaceable portion of coarse or fine aggregate substitutes, and as well as a modifier to Portland cement [2] Concrete is considered one of the most used materials in the field of civil engineering, but sometimes it suffers from some weakness, such as brittleness and tensile strength. High Concrete strength and an innovative concrete mixes, may be capable to overcome these distresses [3]. Structural work of all types consumes large quantities of raw aggregates in addition to large quantities of destroyed infrastructure materials. Despite this use in construction work, these applications did not bring adequate environmental and economic sustainability [4]. In general, concrete consists of Portland cement, aggregates and water, and some admixture is added to it, is sometimes used to modify concrete properties [5][6][7]. Water is required so as to increase speed a cement hydration and reach to a definite workability when built-up concrete [8]. However, the using of UT with the concrete mixes is capable to increase the impact resistance of concrete and ductility as well may be suggested to be used in conditions where large vibrations should be damped, for example in bridge structures [9][10]. It is used in several road projects [11]. Modified concrete with UT also has the role in the protection of the environment in two ways. First is the conservation of raw aggregates consumption and the second is to reduce the environmental pollution resulting from the breaking of rocks, this is when cutting the UT only and adding it as an alternative to the stone materials [12]. Therefore, Environmental protection is a prerequisite for protecting the human race from the dangers posed to it [13]. In the United States, depletion of raw aggregates is projected to increase to 2.5 billion tons per year in 2020 [14]. UT can be called Crumb Rubber (CR), can be added to the concrete as an alternative to the fine aggregates or coarse aggregates, this Investigational Assessment of Modified Performance of Used Tire Concrete Mixtures Feras Al Adday Middle East University, Amman, Jordan, falkhalil@meu.edu.jo ISSN 2347 - 3983 Volume 8. No. 5, May 2020 International Journal of Emerging Trends in Engineering Research Available Online at http://www.warse.org/IJETER/static/pdf/file/ijeter52852020.pdf https://doi.org/10.30534/ijeter/2020/52852020