Abstract: In the present study, mechanical properties of self compacting concrete containing fly ash and silica fume as cement replacements are investigated at different ages of curing. Mechanical properties of specimens were examined at 7, 28 and 120 days for compressive strength and 28 days of curing for tensile strength. So as to reach self compatibility, different tests were carried out on fresh concrete such as slump flow test, T50, J-Ring, V-funnel and L-Box test. Self compacting mixtures had a cement replacement of 20, 30 and 40% with class F fly ash and 5, 10 and 15% with silica fume. The results show that normal strength self compacting concrete could be successfully produced using fly ash and silica fume.
Abstract: The basic mechanical properties of fly ash fiber concrete were tested. The influences to the compressive strength, splitting tensile strength and compressive modulus of elasticity of fiber concrete by water-cement ratio, dosage of fly ash and other factors were analyzed. The influence mechanism of fly ash to concrete is discussed. The results indicate that with the increase of the dosage of fly ash, the early strength of double-doped concrete is reduced, while the later strength of concrete was obviously increased.
Abstract: Aimed at improving the waterproofing property of foamed concrete, a heat-insulating and waterproofing composite applied in underground engineering was prepared by using cementitious capillary crystalline waterproofing material and foamed concrete. The properties of foamed concrete and composite such as compressive strength, water absorption and thermal conductivity were tested and contrasted, and the compounding reaction mechanism was analyzed. The results show that, compared with foamed concrete, the water absorption of composite has been significantly reduced while the heat-insulating property of foamed concrete is maintained and the overall waterproofing and heat-insulation performance has been significantly improved. A new approach solving underground heat-harm such as high temperature and high humidity is provided.
Abstract: Recently reutilization of waste concrete becomes one of the hottest issues in civil engineering field throughout the world. However, most of the concerned research focuses on the RCA (recycled coarse aggregate) by simply crushing waste concrete. In this paper shucking technique is developed to secondary process the simply crushing waste concrete for improving the performance of RCA concrete. Test has been done to demonstrate that performances such as strength, elastic modulus et al. of shucking RCA concrete is better than those of common recycled concrete. Simultaneously, beam specimens are made to test the flexural behavior of shucking RCA concrete. Results showed that the deflection of shucking RCA concrete beam is approximately same with that of natural coarse aggregate concrete beam, which solves current problem that recycled aggregate concrete beam has bigger deflection than common concrete beam. The new shucking technique developed in this paper has many advantages to be applied in practical engineering and it has obvious economic benefits and social effect.
Abstract: Through the experiments of recycling bricks from building waste, the paper studies the mechanical properties and the influence factors of recycled concrete which is based on waste brick aggregates. Using the method of gravels substituted by brick aggregates with the same volume, the optimal mechanical properties can be obtained through adjusting the aggregate contents of different recycled brick sizes, the mix proportion and water consumption of recycled materials. The results of experiments show that there are some key indexes including the bibulous rate of brick aggregates, particle gradations and water consumption, and the optimal size of the brick aggregates ranges from 9.5 mm to 19 mm, and the mechanical properties of recycled concrete are slightly below the referenced concrete by lots of experiments. Therefore, building waste bricks recycled concrete are a kind of very good, sustainable and energy-saving building materials.
Abstract: Boron mud has problems of disposal and health hazards when discharged directly to the environment, so the problem of boron mud needs to be resolved as soon as possible. Although many kinds of treatments about boron mud's problems had been tried, the pollution of boron mud also exists. While magnesia phosphate cement has many excellent characters, so it has a fine future in engineering projects, yet its application scope is limited greatly by the rapid rate of hydration reaction. This work based on the systemic researches of hydration mechanism of magnesia phosphate cement, then proposed a new method of using boron mud to produce magnesia phosphate cement, and the produced cement has an enough setting time. So this way can not only improve the setting property of magnesia phosphate cement but also help to the reclamation of boron mud.
Abstract: Peats are geotechnically problematic soil due to their high compressibility and low shear strength. Cement is widely used for the stabilization of peat by deep mixing method (DMM). This paper presents the results of the model study of compressibility property of peats stabilized with cement columns formed by DMM. The results of consolidation test, scanning electron micrographs (SEM) and energy dispersive x-ray spectrometer (EDX) showed that the compressibility of peats can be improved significantly by the installation of cement stabilized columns. The amount of cement used to form the column was observed to influence the engineering behaviour of treated tropical peats and it had more influence on sapric peat than on hemic and fibrous peats.
Abstract: Based on an extensive experimental program under uniaxial and triaxial compression, this paper studies the mechanical behavior of two types of concrete with the same raw materials and the same curing conditions of the construction site. Stress-strain relations and strengths are obtained under triaxial compression with confining pressures from 10MPa to 120MPa. Material constants of different types of failure criterion are determined by the statistical method with the data from this study and public literature, including linear Mohr-Coulomb model, parabolic Willam-Warnke failure criterion and power functional Johnson-Holmquist model. The results indicate that the modulus of both types of concrete decrease as an exponential decay law with the increase of confining pressures in triaxial compression.