Mechanical capabilities and fire endurance of natural rubber latex modified concrete Mohammad Ismail, Bala Muhammad, Abdirahman Ali Yussuf, Zaiton Majid, and Mohamed ElGelany Ismail Abstract: Compressive, indirect tensile, and flexural strengths characteristics of natural rubber latex modified concrete (NRLMC) were studied and reported — Part I. In addition, a comparative investigation between normal concrete (NC) and NRLMC, conducted on fire endurance was also presented — Part II. Normal and modified elements containing latex–water ratios within 0–10% were prepared and cured in accordance with the Japan Industrial Standard. Fire endurance capacity was assessed at five temperature levels; ambient temperature (27 °C), 150, 300, 500, and 800 °C. However, elevated heating (800–1300 °C) was further applied for the purpose of monitoring behavior at the verge of disintegration. Specimens were al- lowed to cool in the oven prior to compressive strength tests until room temperature is attained. Test results indicate that significant mechanical capabilities could be achieved by the inclusion of an appropriate quantity of latex concentrate and proper selection of befitting curing regime. Interestingly, the superiority of NRLMC over NC is maintained even under fire, up to the critical limit of latex-film capability performance. Key words: latex-modified concrete, natural rubber latex, mechanical properties, workability, latex-film, fire endurance. Résumé : Les résistances en compression, à la traction indirecte et à la flexion du béton modifié par du latex de caoutchouc naturel sont étudiées et rapportées dans la Partie I. De plus, un examen comparatif de la résistance au feu entre le béton nor- mal et le béton modifié par du latex de caoutchouc naturel est également présenté dans la Partie II. Les éléments normaux et modifiés contenant des rapports latex/eau entre 0 et 10 % ont été préparés et durcis selon la norme industrielle japonaise. La capacité de résistance au feu a été évaluée à cinq niveaux de température : température ambiante (27 °C) et à 150, 300, 500 et 800 °C. Toutefois, une température élevée (800–1300 °C) a été utilisée pour suivre le comportement au bord de la désintégration. Des spécimens ont été refroidis jusqu’à la température ambiante dans le four avant d’effectuer les essais de résistance à la compression. Les résultats des essais indiquent que des capacités mécaniques importantes pourraient être at- teintes par l’inclusion de la quantité appropriée de concentré de latex et par la bonne sélection du régime de cure approprié. Il est intéressant de noter que la supériorité du béton modifié par du latex de caoutchouc naturel par rapport au béton nor- mal est maintenue sous le feu, jusqu’à la limite critique de comportement du film de latex. Mots‐clés : béton modifié par du latex, latex de caoutchouc naturel, propriétés mécaniques, maniabilité, film de latex, résis- tance au feu. [Traduit par la Rédaction] 1. Introduction The prevailing increase in the use of elastomeric substan- ces towards improving physical, mechanical, and chemical properties of the normal concrete (NC) may pose a serious threat, especially in the event of accidents involving fire and nuclear reactor pressure vessels. In practice, what is normally required of structural concrete during a fire outbreak is that it preserves structural action over a desired length of time — known as fire rating (Neville 1981). Comparative studies be- tween NC and concrete containing fly ash or natural pozzo- lans on degradation of mechanical properties due to exposure to elevated temperatures have been conducted (Neville 1981; Khoury 1992; Li et al. 2004; Savva et al. 2005). Meanwhile, the fire resistance capacity of concrete alone is very compli- cated because not only is concrete a composite material with components having different thermal characteristics, it also has properties that depend on moisture and porosity (Li et al. 2004). Therefore, the inclusion of a rubber based sub- stance may further complicate issues, thereby demanding rel- evant investigations. In fact, the high degree of combustibility coupled with very low melting point normally associated with most elastomeric materials are likely to cause greater loss of strength in concrete through development of early cracks along the paths of the existing latex-films. Received 9 February 2009. Revision accepted 7 March 2011. Published at www.nrcresearchpress.com/cjce on 4 July 2011. M. Ismail, B. Muhammad, and M.E. Ismail. Faculty of Civil Engineering, Universiti Teknologi Malaysia, 81310 UTM Johor Bahru, Johor, Malaysia. A.A. Yussuf. Faculty of Chemical Engineering, Universiti Teknologi Malaysia, 81310 UTM Johor Bahru, Johor, Malaysia. Z. Majid. Faculty of Science, Universiti Teknologi Malaysia, 81310 UTM Johor Bahru, Johor, Malaysia. Corresponding author: Mohammad Ismail (e-mail: mohammad@utm.my). Written discussion of this article is welcomed and will be received by the Editor until 31 October 2011. 661 Can. J. Civ. Eng. 38: 661–668 (2011) doi:10.1139/L11-035 Published by NRC Research Press Can. J. Civ. Eng. Downloaded from www.nrcresearchpress.com by RYERSON UNIVERSITY LIBRARY on 12/13/11 For personal use only.