7TH INTERNATIONAL CONFERENCE ON COMPOSITE SCIENCE AND TECHNOLOGY Clonal Classification Impact on Physical and Mechanical Properties of Natural Rubber Latex - Modified Concrete MOHAMMAD ISMAIL 1 , BALA MUHAMMAD 1 , M. E. ISMAIL 1 , A.A. YUSSUF 2 1 Faculty of Civil Engineering, 2 Faculty of Chemical Engineering, Universiti Teknologi Malaysia, 81310 UTM Skudai, Johor Bahru, Johor, MALAYSIA. e-mail: mohammadutm@gmail.com Abstract The impact of clonal classifications - as described by the International Rubber Research and Development Board (IRRDB) planting recommendations - on physical and mechanical properties of Natural Rubber Latex-Modified Concrete (NRL-MC) was investigated. Silent qualities of field latices on compressive and tensile strengths as well as water exclusion were studied under various latex/mixing water percentages and curing conditions. Field latices; LTC- G1 PB 260, LC-G1 RRIM 937, LTC-G2 RRIM 2015 and LC-G2 RRIM 926 were employed for the strengths assessments. Four different types of curing regimes in accordance with Japan Industrial Standard (JIS) were opted. Latex-mixing water percentage was varied from 2 - 20%. LTCs excelled in both strengths and water exclusion qualities. The regimes, which included various durations of moist (M), water (W) and air (A), yielded different strengths values, with 2M/7W/19A proving to be the most effective method. NRL-MC depicted higher water exclusion qualities than NC. Generally, the role of NRL in both physical and mechanical properties of concrete is influenced by the clonal specie, amount of latex and curing system adopted. Key words natural rubber latex, clonal classifications, polymer modified concrete, physical and mechanical properties. 1. Introduction The use of elastomeric latexes as concrete modifiers has been in practice within the last few decades. Although there appeared quite a number of synthetic latexes, such as; styrene-butadiene rubber (SBR), acrylonitrile-butadien (NBR) and ethylene-propylene rubber (EPR), which are in common use [1-3], the situation is not well reflected in the areas of NRL clones. Meanwhile,