Applied Mechanics and Materials Vols. 357-360

Abstract: Through semidry process, the wood fiber as reinforced materials and the industrial flue gas desulfurization waste calcinated calcium sulfate hemihydrate as an inorganic adhesive produced the environmental gypsum fiber board. This process is effective on utilization of desulfurization gypsum, which reduced the pollution of the environment and the demand of the natural gypsum, further to protect the natural environment. As green building decoration materials, gypsum fiber board has good prospects for development. The research results show that it is remarkable that the amount of the composite retarder is effective on the static bending strength, internal bond strength, grip screws to impact; the ratio of the wood and plaster is effective on the absorbent thickness expansion rate.

Abstract: In this paper, the Rapid Chloride Permeability Test (RCPT)-ASTM C1202-91 and Conductance test were employed to measure the effect of curing time on the chloride penetration resistance of concrete. The results indicate that the concrete specimens with longer curing time have higher chloride penetration resistance no matter the concrete with or without mineral admixtures, the concrete conductance has the similar variation trend and similar mathematical descriptions as the chloride diffusion coefficient D with the passage of curing time, and it is a very useful method to measure concrete conductance to estimate the chloride permeability variation at different curing or exposure time.

Abstract: Non-destructive techniques (NDT) have been used to assess the condition of existing concrete structures, to predict future performance, and to monitor the conditions of repaired systems and so on. One of the widely known NDT is the ultrasonic pulse velocity (USPV) method, which determines the travel time of the ultrasonic pulse through the tested material. Most studies were focused on the results expressed in time domain. However, the signal of ultrasonic pulse in time domain can be transformed into frequency domain, through Fast Fourier Transform (FFT). This paper shows a comparison of changes in the pulse velocity and frequency domain signals of concrete for various load histories using lightweight fine aggregates. The results demonstrate that the signals in frequency domain of ultrasonic pulse of lightweight fine aggregate concrete does not show any significant difference comparing with those of normal concrete. The reduction trend of peak frequency was found to be more influenced by the stress levels rather than the ultrasonic pulse velocity.

Abstract: In light of the requirement of mass concrete for the bearing platform of the main tower of the Beicha Main Bridge of the Xiamen-Zhangzhou Sea-spanning Bridge, and in view of the hostile environmental conditions for the project, a study was conducted on the technology of preparing high-performance marine concrete for the bearing platform of the sea-spanning bridge in order to control concrete temperatures and achieve the desired durability for the bridge. With an optimal design which features the binary admixture of fly ash and slag and an optimal concrete mix ratio, high-performance concrete with lower hydration heat and strong resistance to chloride diffusion and cracking was successfully developed for the bearing platform of the sea-spanning bridge.

Abstract: Depended on Qingdao Bay Bridge construction, large amount mineral admixture replacing cement has been conducted systematical research aiming at marine concrete, main control index is chloride ion permeability resistance. The main research contents concrete working, mechanical properties and chloride ion permeability resistance at low water binder ratio and large amounts mineral admixture. Measures and adjustment are proposed for marine concrete construction control and cementitious material system that using amount mineral admixtures and low water binder ratio.

Abstract: In this paper the molding mechanisms of mibration compaction for concrete bricks is explained. A lot of concrete bricks with different ash content were by a vibration compaction machines produced. The characteristics of the concrete bricks are investigated. The experiments showed that the starting hardness of the concrete bricks at the separation from molding tools is sufficient for brick stacking.

Abstract: Electricity accelerated corrosion is a common method to obtain corroded reinforced concrete specimens in current experimental research, and it has some relevance and differences with natural corrosion. The paper undertakes a detailed comparative research on the relevance and differences of the two corrosion conditions from the corrosion mechanism, the corrosion process, the corrosion rate, the electric flux and corrosion features, and this provide a better understanding of the research achievements based on accelerated corrosion.

Abstract: Self-healing materials offer tremendous potential for providing long-lived structural materials. In this study, isophorone diisocyanate (IPDI) microcapsules as self-healing materials were synthesized via in situ polymerization. Thermogravimetric analysis characterized the thermal ability of IPDI, microcapsules and microcapsule shells. The morphology of microcapsules and microcapsule shells were characterized by FE-SEM. Scanning micro-reference electrode technique demonstrated that epoxy resin coatings with IPDI microcapsules on the surface of reinforcing steel Q235 could cure the scratched crevice by immersion in 0.01 M NaCl solution after the coating was scratched. The self-healing epoxy resin coating could protect Q235 from corrosion.

Abstract: This paper presents the development of formulas to estimate the creep strain of the reinforced concrete specimens. The experimental part of the work focused on the dispersion of shrinkage strain between reinforced concrete and plain concrete specimens, as well as the equilibrium condition between concrete tension and reinforcement compression. Based upon the experimental data and development formula, the creep strain and concrete age curves of the reinforced concrete specimens are drawn. Moreover, the characteristics of the creep strain are analyzed in detail. The creep strain formula can provide the important data and theoretic basis to “the code for design of concrete structures”（GB50010－2010）.

Abstract: The effects of the different content of cement-sand ratio,fineness modulus of sand, heavy calcium carbonate and high alumina cement on the self-leveling mortar was studied according to orthogonal experiment.The results show that when cement-sand ratio is 1.33,fineness modulus of sand is 2.2,heavy alumina is 20%,alumina cement is 10%,the mix amount of mortar is optimum.It can get a good performance of self-leveling mortar.