J. Cent. South Univ. Technol. (2009) 16: 0914−0918 DOI: 10.1007/s11771−009−0152−x Preparation and properties of geopolymer-lightweight aggregate refractory concrete HU Shu-guang (胡曙光) 1 , WU Jing (吴 静) 1 , YANG Wen (杨 文) 2 , HE Yong-jia (何永佳) 1 , WANG Fa-zhou (王发洲) 1 , DING Qing-jun (丁庆军) 1 (1. Key Laboratory for Silicate Materials Science and Engineering, Ministry of Education, Wuhan University of Technology, Wuhan 430070, China; 2. China Construction Ready Mixed Concrete Co. Ltd., Wuhan 430074, China) Abstract: Geopolymer-lightweight aggregate refractory concrete (GLARC) was prepared with geopolymer and lightweight aggregate. The mechanical property and heat-resistance (950 ℃) of GLARC were investigated. The effects of size of aggregate and mass ratio of geopolymer to aggregate on mechanical and thermal properties were also studied. The results show that the highest compressive strength of the heated refractory concrete is 43.3 MPa, and the strength loss is only 42%. The mechanical property and heat-resistance are influenced by the thickness of geopolymer covered with aggregate, which can be expressed as the quantity of geopolymer on per surface area of aggregate. In order to show the relationship between the thickness of geopolymer covered with aggregate and the thermal property of concrete, equal thickness model is presented, which provides a reference for the mix design of GLARC. For the haydite sand with size of 1.18−4.75 mm, the best amount of geopolymer per surface area of aggregate should be in the range of 0.300−0.500 mg/mm 2 . Key words: refractory concrete; geopolymer; lightweight aggregate; thermal property; equal thickness model 1 Introduction Refractory concrete is suitable for using at high temperature (≥200 ℃) and is composed of refractory cementing material, heat-resistant aggregate and/or fillers, which can maintain the necessary physical and mechanical properties at high temperature for long term[1−2]. Refractory concretes, according to different cementing materials, can be divided into Portland refractory concrete, aluminate refractory concrete, phosphate refractory concrete, sulphate refractory concrete, bauxite refractory concrete, chloride refractory concrete, sols refractory concrete and organic refractory concrete[3]. Heat-resistant aggregate can be divided into broken fire-resistant clay brick, clay, clinker, broken high-alumina brick, natural light aggregate (pumice and tuff), industrial wastes (slag, lytag and gangue), and artificial light aggregate (shale haydite, clay haydite and expand perlite)[4−5]. Refractory concrete can be used for the building engineering with fire incipient fault or in high-temperature work environment. With the development of new building structure and new technology, much better properties of concrete are demanded. Some concretes of the building structure should be of high-strength and heat-resistant characteristics. Many experimental researches on the mechanical and thermal behavior of concrete at constant high temperatures have been reported[6−9]. NEVILLE[10] pointed out that at temperatures approximately above 430 ℃, concretes with siliceous aggregate show a significant strength loss compared to those with lightweight aggregate. At 600 ℃, concrete can lose half of its strength. Above 800 ℃, loss of the bound water in the hydrates may cause a strength loss of 80%, which may lead to the failure of a structure. In Ref.[11], fire resistance of lightweight concretes having a unit weight of 500−1 600 kg/m 3 was inves- tigated. It was found that an increase in unit weight resulted in a reduction in the fire resistance of the concretes. TURKER et al[4] investigated the micro-structure and strength of concretes exposed to fire. In their studies, mortars containing ordinary Portland cement and three types of aggregates were respectively subjected to 100, 250, 500, 700 and 850 ℃ for 4 h. Unlike the mortars with quartz and limestone, at high temperatures, crack was observed in the aggregate for the mortars with pumice instead of crack propagation at the interface. Therefore, it was concluded that the interface was strong when pumice was used[12]. Foundation item: Project(2009CB623201) supported by the National Basic Research Program of China; Project(G0510) supported by the Key Laboratory for Refractories and High-temperature Ceramics of Hubei Province, China Received date: 2009−01−06; Accepted date: 2009−06−09 Corresponding author: WU Jing, PhD; Tel: +86−13476233919; E-mail: wujing313@whut.edu.cn