Applied Mechanics and Materials Vols. 99-100

Abstract: There is a close relationship between the gas permeability of modern high strength concrete and the concrete durability. Through the Cembureau method, gas permeability coefficients of ordinary concrete and concrete with admixtures under different maintenance periods were tested. We studied the influence of fly ash and slag on high performance concrete gas permeability, and analysed the rules of gas permeability changing with mineral admixtures and the water-binder ratio, and gave the reasonable range of mineral admixtures and the water-binder ratio. The results from the paper may have the certain reference value to practical application.

Abstract: Combining with a large number of concrete test and the moving reconstruction project of Qingyang petrochemical about three million tons, by adjusting “advance maintenance time”, monitor and research on the construction quality of mixed composite pumping antifreeze ordinary concrete in winter. Then provide reference and theoretical basis for construction of this winter antifreeze mixed composite pumping concrete.

Abstract: Because of its poor pozzolan property in tests, the pumice was unsuitable to be used as the cement admixture, which could reduce the compressive strength greatly. In the experiment, the cement，replaced with several ratios of pumice，was stimulated by the different content of mixed solution with sodium silicate and KF. The compressive strength results and the SEM morphologies showed that mixed solutions can display excellent alkali-activated effects on pumice.

Abstract: The addition of fiber into concrete can not only suppress the interior shrinkage strain and decrease the thermal dilation coefficient (TDC) of concrete, but also it can lessen the width of shrinkage crack, especially reduce the appearance of interconnected pore, thus the reduction of the water content of capillary pore will make the TDC of paste matrix lessen. In this paper, an experiment was designed to study the TDC from the 5th day to the 29th day after the concrete was poured. The results show that the addition of fiber can effectively reduce the TDC of concrete. When the addition is the same, high-modulus carbon fiber reinforced concrete has a lower TDC than low-modulus polyester fiber concrete.

Abstract: Based on the test by the split Hopkinson Pressure Bar (SHPB), in this papaer the research on the dynamic mechanical properties of concrete under high temperture has been conducted, the influence law of temperature and strain rate on the mechanical peoperties has been analyzed, and the dynamic stress-strain curves of concrete under high temperature have been obtained. Analysis indicate that the concrete strain rate hardening effect is coupled with the high temperature weakening effect. Therefore, on the basis of classical damage theoretical model, in accordance with the concrete high-temperature dynamic mechanical characteristics, a unified equation is established to describe the whole process of concrete dynamic stress-strain relationship under high temperature, which is well coincided with the test results.

Abstract: This paper adopted combined admixture of limestone powder and substandard fly ash to prepare the machine-made sand concrete, and studied its performance, compressive strength and micro-properties. The results showed that this kind of machine-made sand concrete owned a good performance, for its 60min slump loss within the range of 15mm to 85mm; the changes in the ratio of limestone powder to low-quality fly ash had little effect on the its compressive strength; with the increase of the ratio between limestone powder and low-quality fly ash, the Ca(OH)2 diffraction peak also increased; when hydration was up to 120d, the limestone powder was not involved in the hydration reaction.

Abstract: Tunnel mechanics mainly depend on joints properties in layered and jointed rock mass, and most of the present methods adopted in numerical analysis are distinct element method. Combining to the Gaixiaba tunnel, considering the jointed properties such as dip angles, distances and lateral pressure coefficient, the finite element models are made in this paper. Results show that the plastic zone and total displacement presented a symmetric distribution with the axial of joints dip, and the plastic zone is very similar to the results suggested by Goodman. The dip angles, distances of joints and lateral pressure coefficient have significant effect on the tunnel mechanics.

Abstract: Part of Xiping railway south cave temple bridge segments are on easement curve. considering the project time limit and construction difficulties of large span curved bridge, the construction team adopted 64m soffit scaffolding composite column structure to assemble the precasted box girder segments ,this method can better solve the technical problems of nonuniform stress distribution in transverse beam and upright tubes of the bracket. Therefore, this paper introduces in details the bracket structure as well as the key construction technologies of segmental beam rand bracket. the experience can provide good reference for similar engineering.

Abstract: The work of energy saving in the Institution of higher learning was analyzed in the research, and the problems facing higher education on energy consumption were analysed. These measures were proposed that establishing lead agency, strengthening energy conservation regulation, conforming resources efficiently, optimizing resources and facilities, strengthening the publicity of saving, establishing energy-saving habits, detailing day to day management, reducing energy consumption effectively. Through the above measures, speeding up the process of energy saving higher education.

Abstract: Through experiments, in concrete reasonable use efficient jianshuiji, fly ash and slag powders and adding mixed materials thereof after the concrete can be greatly increased the anti-permeability and improve the durability of concrete.