Advanced Materials Research Vols. 250-253

Abstract: Based on the MFPA^2D software system and test method of the wedge splitting fracture in the Lab., a numerical model was established. The numerical experiments on wedge splitting fracture with plain concrete and SFRC (steel fiber reinforced concrete) were carried on. The calculation results about plain concrete with different dimensions and ligament length proved the numerical model is effectively on numerical calculation, and have a good agreement with the results of the test results. Then, the process of crack initiation, propagation of SFRC specimens with different dimensions and fitting formula about size effect were given. The results indicated that the size effect existed in the splitting fracture energy of SFRC.

Abstract: The coating of having the capability of reflecting solar heat is the requirements of the world of saving energy. This kind of coating can reduce the need of electronic and water power besides protecting and decorating the covered objects. The gray color coating with insulating heat and lowering temperature is one of the most difficult topics. In this research, on the basis of choosing reasonably resin,pigments and fillers and assistant agents , a kind of special gray coating is obtained. It can obviously lower the temperature of coated objects in comparision to the common gray coating. Its refletivity can be up to above 50% to solar light.

Abstract: This paper presents results of a study to assess the Government Contractor Classification System in Saudi Arabia. Contract award procedures in public projects of Saudi Arabia are accomplished in two steps. The first one involves qualifying contractors to insure that their technical, financial, and managerial capabilities are suitable for the project to be awarded. This qualification is accomplished by the Contractor Classification Agency- Ministry of Municipal and Rural Affairs- in which the contractor is classified according to his specialty and capabilities. In the second step, bids of the contractors who satisfy the required classification are evaluated to select the best bid. Since the contractor classification is the only screening method to disqualify incompetent contractors and the difficulty of dismissing a qualified contractor who submits the lowest bid, the contractor classification must be an actual measure for the contractor's capabilities. To assess the contractor classification system a questionnaire has been prepared and distributed to the project mangers in different public ministries and agencies. The number of distributed questionnaire was 250 and 198 were collected and used in this study. In order to conduct an objective evaluation, a comparison has been conducted between performance of contractors who are awarded projects based on the contractor classification only with performance of contractors who are awarded projects based on the contractor classification and an additional prequalification by the project owner. Also, Chi-squared test was used to verify the cause of the difference in results of using these two types of prequalification. Results of the study reveal that the contractor classification system does not properly reflect the contractors’ capabilities.

Abstract: This paper taked hollow glass window as the model, and heat transfer coefficient, sunshading coefficient and energy consumption of the window glass were obtained in the situations of window glass with and without low-E film by doing experiment and theoretical calculation. The results show that both heat transfer coefficient and sunshading coefficient decrease comparing the hollow glass window film with no film. For the fixed and push-pull window of the whole window, the heat transfer coefficient decrease by 24.2% and 28.9% respectively and sunshade coefficient decreases by 31.37%. And the low-E film by this study adopting reduces energy consumption of the summer greatly by 32.96%, and has no too large effect on winter heating, so the annual energy consumption reduces and the window film saves annual energy consumption 14.62% .

Abstract: This paper studied the mechanical properties of concrete with cement partially replaced by recycled clay-brick-powder. Four variables (water/cement ratio, sand ratio, replacement level and average particle size of clay-brick-powder) were considered. Each variable had four levels. By using the orthogonal experimental design method, total 17 mixes, including one normal cement concrete as reference, were tested. Experiment results showed that recycled clay-brick-powder could be used as partial replacement of cement in concrete without reducing its properties. The strength was not significantly reduced with cement replacement level up to 25%. The elastic modulus was lower compared with cement concrete.

Abstract: Sulfur extended asphalt technique is an effective technical means as it uses SEAM as an additives of asphalt mixture. According to the analysis of SEAM modified asphalt mixture mechanism and the functions of SEAM in asphalt mixture, SEAM has a well modification. The application of SEAM in severely frigid area researchs the major parameters of mix design for AC–25 SEAM.

Abstract: In this study, 9 short rectangular concrete columns with cross-section 150mm×300mm and height 600mm are prepared, they are 6 confined concrete columns encased in CFRP tubes and three concrete columns as control specimens. The tubes with fibers oriented at hoop direction are manufactured to have 3 or 5 plies of CFRP sheet with 10mm, 20mm, or 40mm rounding corner radius. To ensure proper bond, a 100mm overlap is provided in the direction of fibers. Axial compression tests are conducted to investigate the axial strengths, compression behaviors, stress-strain relationships, and ductility until the CFRP tubes rupture. It is evident that the CFRP tube confinement can improve the behaviors of concrete core, in terms of axial compressive strength or axial deformability. Experimental results also show that the stress-strain behaviors of confined specimens vary with different the layers of CFRP sheets and corner radius at vertical edges.

Abstract: Four-point bending test was employed to investigate the effects of gradation of sand on the mechanical properties of Engineered Cementitious Composites (ECC). The characteristics of ECC such as mid-span deflection, first cracking load, peak load and fracture toughness were obtained from the load-deflection curve. Effects of gradation of sand on fresh properties, compressive strength, flexural strength and drying shrinkage of ECC were also discussed in this paper. Test results shown that when the fineness modulus of sand in ECC was 1.0, the mid-span deflection and fracture toughness of ECC increased nearly 1.5 times and 2 times that of ECC with the sand fineness modulus of 2.97, respectively. With the sand getting finer, the more superplascitizer is needed and the crack width of ECC becomes smaller. The drying shrinkage of ECC with 2.97 and 1.0 fineness modulus of sand at 24 days was 8×10^-4 and 15.6×10^-4, respectively.

Abstract: In order to study the flexural behavior of coarse recycled aggregate-filled plain concrete beams, two beams were made. The experiment of simply supported beam under concentrated loads is performed, which makes us get the ultimate flexural capacity, midspan deflection and the development of cracks of each beam, and the numerical simulation of the damage process of beams is also carried out using finite element software. The results indicated that the tension property of coarse recycled aggregate-filled plain concrete beam is better than ordinary concrete beam, and some failure forms of bending is similar; the strength of recycled aggregates greatly influences flexural behavior of coarse recycled aggregate-filled plain concrete beam.

Abstract: Based on the project requirement of a nuclear power plant, using the method of free shrinkage test and ring cracking test, shrinkage cracking resistance property of grade C35 and C50 self-compacting concrete (SCC) with the optimized mix proportion was studied. The test results between SCC and ordinary vibrated concrete afforded by nuclear power plant project with the same grade were compared. The results indicated that the shrinkage cracking resistance property of SCC is prior to the ordinary vibrated concrete with the same strength grade. This kind of SCC can satisfy the nuclear power plant project, also the test results can be a reference of SCC design theory.