Size Effects On Mechanical Properties And Stress-strain Relationships Of Thermal Insulation Concrete With Glazed Hollow Beads

Thermal insulation concrete with glazed hollow beads(TIC) is a new concrete that combines the advantages of thermal insulation, energy-saving and lightweight. Besides, the performances of TIC in energy-saving, durability and seismic are superior than those of normal concrete(NC) as well as those of high strength concrete(HSC). In addition, the development of TIC meets the requirements of building energy efficiency standards and green building subsidies policies. Thus, the application of TIC in many areas is promising in the future.In such new material, glazed hollow beads having the properties of lightweight and thermal insulation are added into NC and HSC, therefore, the stress and deformation characteristics of TIC are different from those of NC and HSC. The cability of applying codes of NC and HSC is considered when they are applied to TIC. When referring to different codes, specimen sizes of mechanical properties are various, which may results in the changes of the mechanical properties of TIC. This is so-called size effect.In order to study the mechanical properties of TIC in-depth, comparing the results with foreign findings for conveniences, providing technical support for the specification revisions of TIC, this study refers to test methods of ordinary concrete(GB/T 50081-2002), ASTM standards of mechanical properties and relevant literatures of stress-strain relationships. Size effects of mechanical properties and stress-strain relationships of TIC are studied in the paper. The main work is as follows:(1) Five different strength levels(C30,C40,C50,C60,C70) were designed, and thermal conductivities of TIC were studied. The results show that thermal conductivities are 0.332~0.589W/(m·K) when the strength levels are C30~C70. Thermal conductivities increase with the increase of strength levels, thus the thermal insulation properties decrease.(2) Different strength levels and sizes were designed, and conversion factors were used to reflect size effects. Size effects on compressive strength, splitting tensile strength and elastic modulus were studied. The results indicate that size effects are reflected on compressive strength and splitting tensile strength test. Compressive strength and splitting tensile strength decreases with the increase of the sizes of specimen. However, the sizes of specimens have little influences on the elastic modulus of TIC.(3) The failure behaviors of compressive test, splitting tensile test and flexural test were also analyzed. The result shows that the failure behaviors of compressive test, splitting tensile test and flexural test are similar to those of NC and HSC suggested by Zhenhai Guo. The fractures are severer with the increase of strength level.(4) Five different strength levels and two sizes(prism and cylinder) were designed to prepare stress-strain relationships of TIC under uniaxial loading conditions, and the cability of applying codes of NC and HSC are considered when they were used to analyze stress-strain relationships. The study indicates that size effects exsit on stress-strain relationships, and the curve fittings of prisms and cylinders are different.(5) The ratio of ultimate strain to peak strain was used to analyze the influences of strength level and size on ductility of TIC, and compared with those of NC and HSC. The result shows that when strength level are C30, C40 and C50, ductility of TIC decreases with the increase of strength level, and ductility of TIC is better than that of NC with the same strength level. In addition, ductility of prism of TIC is better than that of cylinder.