Research Journal of Applied Sciences, Engineering and Technology 2(3): 262-267, 2010 ISSN: 2040-7467 © Maxwell Scientific Organization, 2010 Submitted Date: March 17, 2010 Accepted Date: April 01, 2010 Published Date: May 10, 2010 Corresponding Author: Dr. Robert M. Brooks, Department of Civil and Environmental Engineering, Temple University, 1947 N. 12 Street, Philadelphia, PA 19122, USA 262 Residual Compressive Strength of Laterized Concrete Subjected to Elevated Temperatures Felix F. Udoeyo, Robert Brooks, Philip Udo-Inyang and Canice Iwuji Department of Civil and Environmental Engineering, Temple University, 1947 N. 12 Street, Philadelphia, PA 19122, USA Abstract: This research presents the results of an experimental program to investigate the strength performance of laterized concrete (LATCON) when subjected to elevated temperatures of 200, 400 and 600ºC. Six concrete mixes incorporating 0, 10, 20, 30, 40 and 50% Laterite as a replacement by weight of sand was prepared. After heat pretreatment specimens were cooled using either rapid cooling (water-cooling) or natural cooling (air-cooling). An analysis of variance test shows that exposure temperature, cooling regime, and their interaction have a significant influence on the compressive strength of the samples. When subjected to the investigated temperatures specimens experienced strength losses that increased with temperature. This study further reveals that air-cooled concrete specimens maintained higher residual strength values than water-cooled specimens. A comparison of the residual compressive strength data obtained in this study with code provisions in Eurocode and CEB design curve shows that these codes could be applied to LATCON subjected to temperature below 400ºC. Key words: Compressive strength, elevated temperatures, influence, laterized concrete INTRODUCTION Concrete, a leading construction material in civil engineering is sometimes exposed to elevated temperatures due to natural hazard (Vodak et al., 2004). Subjecting concrete to high temperatures leads to transformations and reactions that cause the progressive breakdown of cement gel structure and consequent loss in load-bearing capacity (Khoury, 1992; Anonymous, 1972; Erline et al., 1972; Hanson, 1990; Handoo et al., 2002). High temperatures also cause chemical and micro- structural changes, such as water migration (diffusion, drying), increased dehydration, interfacial thermal incompatibility, and chemical decomposition of hardened cement paste and aggregates. These changes decrease the strength and stiffness of concrete and increase irrecoverable deformation (Zhang et al., 2000). The effect of elevated temperatures at varied heating scenarios on the strength of plain concrete has been investigated by many researchers (Mohamedbhai, 1983; Khalaf and DeVenny, 2004; Chan et al., 1999; Min et al., 2004; Poon et al., 2001; Phan et al., 2001; Xiao and Falkner, 2006; Mahdy et al., 2002; Abramowicz and Kowalski, 2005; Jianzhuang and Konig, 2004; Phan and Carino, 2000). However, there is dearth in research data concerning the behavior of LATCON under high temperatures. For structural safety in service, and possible rehabilitation, strengthening and reconstruction of laterized concrete in the event of fire, it is very essential that the strength properties of this concrete subjected to elevated temperature be understood, and that is the focus of for this experimental program. MATERIALS AND METHODS The study was performed during 2005 at the Federal University of Technology in Owerri, Imo State, Nigeria. The cement used was a Type I ordinary Portland cement, a product of the Eastern Bulkcem Company Limited, Port Harcourt, River State of Nigeria. It had a specific gravity of 3.15, a soundness value of 0.53 mm, and initial and final setting times of 50 and 120 min, respectively. Two types of fine aggregate were used for this study- sand and laterite. The sand having a specific gravity of 2.60 was obtained from the Otamiri River near the Federal University of Technology, Owerri, Imo State of Nigeria. The laterite was obtained from a borrow pit within the same region. The Scanning Electro-micrograph (SEM) showed a mixture of large and smaller particles of lateritic soil (Fig. 1). The bulk chemical composition of the lateritic soil measured using XRF are shown in Table 1. Tests for the SEM, physical and chemical properties of the Lateritic soil were conducted at EMSL Analytical in Westmont, New Jersey, U.S.A. The grain size distribution of the aggregates is shown in Fig. 2. The coarse aggregate used was a crushed granite rock with a maximum size