Advanced Materials Research Vols. 250-253

Abstract: In order to shorten time-periodic of mix design and verification of cement concrete in the period of construction, and can realize the node control of key procedure of cement concrete structure. The paper obtained and established relationship between super-early-stage strength and compressive strength of 7d, 14d and 28d of cement concrete on based of microwave promoting curdle. The method can realize predication of cement concrete through microwave promoting curdle.

Abstract: This paper firstly introduces the concept of project controlling management and the application status in China, then analyzes the problems of project controlling management mode in application – the owner’s mistrust, explains the necessity of research on trust level evaluating indexes of the owner to the controlling, discusses the trust level evaluation indexes of the owner to the controlling, points out the next research direction..

Abstract: The objective of this study is to develop a numerical model based on microstructural images of concrete and fundamental material properties of each constituent of concrete subjected to alkali-silica reaction (ASR). A microstructure-based finite element approach is employed directly to analyze the mechanical response of concrete to ASR. The modeling work involves acquiring and processing of microstructural images of specimens suffering from ASR using scanning electron microscopy, and implementing finite element program to analyze the microstructural images. The formulation of this model is based on pressure caused by the ASR product and on properties such as Young’s modulus and Poisson’s ratio. The finite element analysis program used to simulate structural behavior of structures attacked by ASR is object-oriented finite element developed at National Institute of Standards and Technology. The numerical results from this model are compared with experimental data, which have been measured using ASTM standard test C1260. The results show that the development and widening of cracks by formation and swelling of ASR gel cause the majority of expansion of mortar specimens rather than elastic elongation due to gel swelling.

Abstract: According to the desulphurization reaction temperature and the content of calcium sulfite, FGD ash is simulated, that is the ordinary fly ash mixed with different weight percentage of CaSO₃·1/2H₂O is followed by drying at 100°C. And then by the experiment of workability, strength, sulfate resistance and rebar corrosion, the effect of the fly ash with different of CaSO₃·1/2H₂O on material properties are studied. The results show that: compared with ordinary fly ash, the desulphurization ash contained 4~12% CaSO₃·1/2H₂O can improve workability, but it has a 4% threshold, over critical value, the improving ability declined; secondly increasing the content of CaSO₃·1/2H₂O in desulphurization ash can decrease strength, and while the effect of 7 day strength is higher than 28 days’; Thirdly, with the increase of calcium sulfite, the desulphurization can decrease resistance to sulfate attack , especially for more than content of 8% CaSO₃·1/2H₂O , but it is harmless for steel rebar.

Abstract: On the premise of using the five dosage levels of recycled coarse aggregate, the paper primary study on the drying shrinkage and water absorption rate of recycled concrete hollow block in order to determine the maximum dosage of recycled coarse aggregate, then find out the relationship between the drying shrinkage and the water absorption rate of recycled concrete hollow block. The results showed that: the maximum dosage of recycled coarse aggregate can reach 100%; there is a quadratic relationship between the drying shrinkage and the water absorption rate of the block.

Abstract: This paper describes the preparation of the high-strength concrete with stone chips and the application of the stone chips in PHC pipe piles production. The results show that when the stone chips substitutes for the natural sand, the strength of the concrete increases and the workability of the fresh concrete is improved.

Abstract: Night ventilation is one kind of passive cooling ways which is very effective in certain climate type. The main work of this paper is to determine the cooling potential of office buildings that use night ventilation in the city of Xi'an. Xi'an is located in the Continental Climate zone of China. For this purpose, a typical office building simulation model has been built for the numerical analysis. Cooling and energy-saving potential of night ventilation in office buildings is determined through the simulation in different ventilation and air-conditioning cases by the energy simulation software DeST.

Abstract: That griping and predicting concrete strength is crucial importance for shorten design cycle of cement concrete proportion and control efficiently key construction node in time. The paper exposited systematically experimental method of strength estimation of cement concrete and corresponding research progress at present, and the prospect was also analyzed. It is very necessary to promote research work of experiment and analysis method because strength estimation of cement concrete is paramount. It has important meaning for delving into the aspect through above discussion in the future.

Abstract: One of the methods of retrofitting reinforced concrete structures is use of FRP sheets to increase the flexural and shear strength of concrete elements. Use of FRP materials is in rapid progress because of their high strength, light weight and easy installation of FRP composites. Poisson’s ratio mismatch between FRP sheets and concrete is resulted premature debonding of FRP strips. Hence, the use of ultimate strength of FRP sheets is difficult if EB (External bonded) is applied in installation of FRP. Therefore, debonding has been repeatedly reported in most experimental studies. Recent studies in Isfahan University of Technology (IUT) show that use of grooving method (GM) to attach the FRP sheet to concrete surface for flexural strengthening is much more effective compared to conventional methods. In present experimental study, small scale reinforced concrete beams were strengthened with FRP strips for shear. Comparison between the ultimate load and deflection of the test beams demonstrates that grooving method was effective and led to elimination of debonding of FRP strips used for shear strengthening.

Abstract: The microwave interferometer was used for monitoring the behavior of a simply supported bridge under various loading cases. The instrument has a 1-D imaging capability for remotely measuring the displacements of multiple positions simultaneously. The loading cases include truck placed at the middle of the span, driven with variant speeds to generate ambient vibration of the span, driven through with a constant speed, and abruptly stopped at the middle to obtain the damping characteristics of the span. As the bridge has been in operation for 50 years, weak bearing stiffness for the support at abutment and possible fatigue fracture of a roller support above a pier was found from this investigation.