Key Engineering Materials Vols. 302-303

Abstract: To improve the anticorrosivity of concrete, an analysis was made to the corrosivity/anticorrosivity mechanism of concrete followed by some relevant technical measures proposed to take. In the experiments, anticorrosive agent was used to prepare the high-anticorrosivity concrete with different proportioning. Both the experimental and application results showed that the concrete we developed had high physical/mechanical properties and durability especially the high anticorrosivity feature.

Abstract: In this paper, the study and application of an entirely new energy-saving residential building structure, whose wall is constructed with multi-ribbed composite wall and latent frame. Based on experimental research and theoretical analysis, it was found that the structure system had good seismic behaviors, strong structure adaptability and good energy-saving effect. At the same time, notable social and economic benefits have been shown in several examples.

Abstract: A new kind of low-strength concrete is suggested to fill big caves to protect environment and ecosystem. The low-strength concrete have been studied regarding strength, wave propagation, water content, porosity, composition and cemented material by press experiments and sound wave analysis and shear tests. Those results show that: (1) the mechanical characteristics of low-strength concrete is complex; (2) strength of the low-strength concrete comes from interlocking of large-size crushed stones and bond of cement particle; (3) water content has significant effect (more than 30 percent) on velocity of longitudinal wave of the low-strength concrete and has little effect on strength; while effect of porosity of concrete on strength are more than 30 percent; (4) strength of low-strength concrete are controlled by both the content of crust stones and content of cement and a relationship of strength and velocity of longitudinal wave is proposed.

Abstract: In recent years, with the extensive application of deep mixing method in reinforcing the soft clay, study on the basic properties of cement-soil has been conducted deeply. In order to improve economic benefits and social benefit of the deep mixing method, this paper focuses on strength and permeability of cement-soil incorporating both lime and fly ash through laboratory experiments. According to the experimental data, the properties of cement lime-fly-ash soil are compared with those of ordinary cement-soil. The results show that cement lime-fly-ash soil is better than ordinary cement-soil. And some valuable conclusions are drawn based on experimental data. Firstly, the fly ash and lime mixed can raise strength remarkably. Secondly, the fly ash and lime mixed can improve impermeability of cement-soil effectually, especially when cement mixing ratio is very low. Thirdly, adding only fly ash into cement-soil can have adverse effects on the impermeability of cement-soil. In addition, the equivalent cement mixing amount of cement lime-fly-ash soil is identified through experimental data. These conclusions are valuable to engineering design and construction.

Abstract: This paper presents mix proportion design and the construction of the barite concrete structure, mixing, transportation and construction characteristic of the barite concrete. Technical solutions were proposed to problems in construction.

Abstract: The emphasis of this paper is how to increase the 3-day and 28-day strength of high volume fly ash concrete. By some technical measures, such as improving the initial pozzolanic activity (3 day) of fly ash and decreasing the ratio of water to binding material and increasing the total dosage of binding materials, a concrete with the ratio of fly ash to binding materials between 50 %-70 % can be made. The fluidity of the concrete mix with large dosage of fly ash is very good and the strength at 3 day and 28 day are more than 42.5 MPa and 85 MPa respectively. By determining the pH value and the calcium hydrate content of the paste with large dosage of fly ash and accelerated carbonation test, it is shown that the resistance of the concrete to carbonization has been improved. The concrete with large dosage fly ash has good volume stability.

Abstract: In this paper, a mathematic morphology measurement with the name of opening operation was applied to section images for the assessment of pore size distribution in cement pastes. This method is compared with other methods for characterising pore size distribution, including the experimental technique of mercury intrusion porosimetry, the conventional image analysis by area histogram and a direct approach by a simulation model. The comparison study reveals that the so-called opening distribution technique yields realistic structural information of pore size distribution in cement pastes. The proper characterisation of pore size distribution is of significant importance to permeability prediction of cementitious materials and thereby to durability studies of the materials.

Abstract: Fresh model cement mixtures, with the same w/c ratio and particle size distribution, were simulated by the SPACE system that is based on a dynamic mixing algorithm. Thereupon, they were hydrated by the HYMOSTRUC 3D system. Boundary conditions were varied, rendering possible assessment of their influence on percolation of capillary porosity by serial sectioning and using the overlap of slices. Simulation results revealed increases in total porosity and in connected fraction of capillary pores due to the existence of aggregate. The de-percolation threshold of capillary porosity was found not only related to total porosity and image resolution, but also governed by the spatial distribution of capillary pores.

Abstract: This report presents a research on vibration absorption properties of coated cement concrete, by discussing the logarithmic decrement and dynamic modulus obtained from bending vibration test at various temperatures. The effect of temperature and bitumen content on the vibration properties of materials was evaluated. As temperature and/or coating asphalt content increased, coated cement concrete increased logarithmic decrement and resulted in increasing vibration absorption than the conventional cement concrete. The vibration properties of coated cement concrete were similar to those of conventional cement concrete in the low temperature range. The dynamic modulus of coated cement concrete decreased at higher temperatures. The rate of decrease of dynamic modulus at higher temperatures was comparatively small in comparison with the rate of increase of logarithmic decrement.