Advanced Materials Research Vols. 168-170

Abstract: A DEM-FDM coupling model was established in this paper to study flow and failure mechanism of cushions with different thickness in rigid pile composite foundation (RPCF). Via analyzing displacement and stress fields in simulation results, the flow of cushion and its mechanical reason was discussed, the results showed that the flow of cushion was mainly caused by the penetration of pile and sand wedge above the pile head; and the shearing of particles along the outlines of pile shaft and the wedge was the main mechanical reason for the flow of cushion. In addition, theoretical discussion of potential failure of cushion in RPCF showed that the bearing capacity of cushion was large enough to keep cushion safe in normal cases.

Abstract: Solidified sludge as backfill material exists serious phenomenon of shrinkage and cracking, and the project's strength, permeability and stability will be adversely affected. The material used in this study is sludge with high water content from the Metro construction sites in Hangzhou. In this paper, our main research is the influences of the initial water content of sludge, curing period and cement content on the curing shrinkage of silt. The results show that the shrinkage increases with initial moisture content, decreases with the increase of the cement content, and increases with curing period. Strength decreases with the increase of initial water content, increases with cement content, and increases with curing period. The test has a certain reference value to the engineering practice.

Abstract: According to dry-mixed materials of shotcrete which composed of raw materials in mix proportion the concrete quality as field mixing were included. Through the experimental research on the storage period of using dry-mixed materials in shotcrete, variations of compressive strength were obtained. In according with the studies on the storage period of dry-mixed materials in 7d, 11d, 15d, 20d and 28d, compared with 0d, the loss of compressive strength were obtained under different sand water content (0%, 0.5% and 1.0%). The results shown that strength loss rate of C30 concrete was 6.7% when the sand water content was 0.5% in the 28d and while strength loss rate was 12.0% when the sand water content was 1.0%. The studies on storage period provide supports to the using of dry-mixed shotcrete in engineering application.

Abstract: The ultra high performance concrete is a new cement-based composite material with ultra-high mechanical properties, excellent durability and excellent volume stability. In this paper, research and application of the ultra high performance concrete at home and abroad at present was introduced, existing problems of the ultra high performance concrete applied to much practical engineering were pointed out. Finally, the prospects of ultra high performance concrete were analyzed and the ultra high performance concrete is inevitable result of the sustainable development of modern concrete technology.

Abstract: This paper related to the recycling of banknote printing wastewater, using which as raw materials, a low cost interior latex coatings has been developed. This coatings is formulated based on styrene-acrylic emulsion and silicon sol as main film former. It has been shown that the performance of of this product meets the state standard of GB/T 9756-2009.

Abstract: Based on surveys of buildings passing through ground fissures, failure and deformation characteristics of buildings are analyzed. Failure models of buildings under the influence of Xi’an ground fissures are proposed. By means of the simulations on PLASIX, taking for the f6 of ground fissures in Xi’an city, the variations of stress field and displacement field of the overlying soil layer which the normal fault qualitative ground fissures lead to are studied. It separately calculated out of the variation of the features of deformation, when brick masonry, block masonry and stone masonry act as solely material of the building. The total, vertical and horizontal deformation of buildings built of stone masonry are the largest and brick masonry’s deformations are the smallest. It is suggested that materials with small gravity density should be used for building materials.

Abstract: In order to investigate the flexural behavior of concrete beam reinforced with 500MPa fine grain high steel bars, four rectangle cross-section concrete beam subjected to static bending test were made. Mechanics characteristic, flexural capacity of normal section, crack and deflection were analyzed according to current related China code. The results show that the flexural behavior of concrete beam reinforced with 500MPa fine grain high steel bars is similar to normal concrete beam, the average strain of concrete section keep plane; flexural capacity and average crack spacing could still calculated by current code for their values coincide well with tested value; however, deflection values of the specimens calculated by current related China code are smaller than corresponding tested value; under the state of serviceability, crack width and deflection of the specimens were found not to meet the requirement of current China code while the design value of yield strength of 500MPa fine grain steel bar was taken more than 360MPa.

Abstract: The phenomena of Damage localization, which characterized as the rock mass suddenly enter into the deformation localization stage after a period of uniform deformation, is the beginning of rock failure. Damage localization is also the precursor of rock failure. Utilizing the image enhancement and segmentation technology, the rule of damage evolution of limestone under triaxial compression is analyzed. Moreover, The computerized tomography images are analyzed by the method of digital image processing, which includes threshold partition and edge detection, and then the relationship between computerized tomography image and damage evolution is discussed. Meanwhile, the dependence of fractal dimensions of rock section on the axial stress is determined by the method of box-counting dimension. It is concluded that the fractal dimension may reach a minimum value at the point of damage localization, and after that damage become more severe.

Abstract: Temperature and elastic modulus of mass steel fiber concrete change as time in casting process. If not well handled, it is easy to crack in the process of construction. In order to hold the temperature distribution of mass high strength concrete in pouring process, we set up the model that meets with engineering characteristics. It is based on the partial differential equation of heat conduction and elastic modulus value from test and cement hydration heat of concrete on site. By contrast, the simulation results are in good agreement with the experimental results.

Abstract: In precast concrete elements manufacturing, steam-cured concrete incorprating 30% mineral admixtures encountered the problem of too low demoulding compressive strength. To resolve it, this paper mainly studied the influence of mineral admixtures on the compressive strength, the tensile-splitting strength and the flexural strength of the steam-cured concrete. The experimental results indicated that, compared with steam-cured concrete incorprating mineral admixtures, the later strength of steam-cured concrete incorprating 0% mineral admixtures has lower increment degree and its increment of tensile-splitting strength and flexural strength inverted to some extent. The demoulding compressive strength is too low for the high volume fly ash concrete mixtures. The problem of too low demoulding compressive strength is solved by incorprating composites of ground blast furnace slag(GBFS) and fly ash. Different varieties of mineral admixture used in the concretes can produce a certain degree of potentiation.