Advanced Materials Research Vols. 671-674

Abstract: Steel fiber concrete is a new-type composite material of excellent property with broad application formed by common concrete mixed with disorderly oriented short steel fiber. Main action of steel fiber is to prevent broadening of interior micro crack in concrete and restrict occurrence and growth of macro crack. Based on basic theory of concrete fracture mechanics, this treatise adopts four-point shearing sampling material to conduct experimental research, having obtained critical fracture curve of crack of composite mode I, II of steel fiber concrete, setting up experimental formula of fracture criterion, probing into difference between fracture toughness of steel fiber concrete and that of common concrete, and discussing application of maximum tension stress theory in steel fiber concrete.

Abstract: Going towards sustainable pavement construction, asphalt industries constantly give their effort to implement Warm Mix Asphalt (WMA) by adding the chemical warm asphalt additive (CWAA). This can lower its energy consumption and pollution by reducing the mixing and compaction temperatures of the asphalt mixture without affecting its properties. Several studies have been conducted evaluating the properties of the WMA, however, little documented research on the rheology of the binders containing CWAA is available especially when dealing the sources of binders. In this paper, the tests for rheology characteristics of the Malaysian asphalt binder containing CWAA were conducted with rotational viscosity and for dynamic mechanical analysis with dynamic shear rheometer (DSR). The results of the investigation indicated that the CWAA had a significant reduction of required heat for mixing and compaction effort and also shows lower permanent deformation when compared to the control binder.

Abstract: By means of testing expansion rate of different cementitious material under the sulfate corrosion experimental conditions, sulfate resistance of cementitious material and assessment method are studied. The results show that expansion rate of cementitious material increased with corroded age, and the assessment method is put forwarded. Sulfate resistance of cementitious material can be divided into five classes according to expansion rate assessment method as follows: "very low", "low", "moderate", "high" and "very high". The sulfate resistance of Portland cement is better than ordinary Portland cement, and both of them are very low. Mineral admixture with proper content can improve sulfate resistance of cementitious materia largely. Sulfate corrosion mechanism of different kinds of cementitious material is analyzed.

Abstract: In the process of the optimization of concrete mixed proportions in the gravity-type dam of the upper reservoir in Yixing Pumped Storage Power station, potential problems of initial mixed proportions are analyzed and a set of nonlinear optimized multi-objective is drawn up. A stepwise regression analysis and duplex optimized method are used to solve optimized multi-objective model. By increasing the order of regression equation and softening the variables, objectives and constraints system, the shortcoming of linear optimization such as narrow variation span, severe formal limitations of objective and constraint function can be overcome and the flexibility of the choice for optimized objective is easily to be achieved. Combined with the traditional linear regression method, the results of optimization have been corrected further. The practical effect shows that the work achieves very good technical and economic benefits with a smaller amount of test work to reduce the project cost.

Abstract: Destructive process of ceramsite concrete is nominally that at the earliest stage, microcracks appear in ceramsite aggregate and spreading to boundary surface. Once they develop to mortar, if no other factors to restrain crack propagation, ceramsite concrete will be destroyed quickly. After including of steel fiber, toughness of ceramsite concrete will be greatly increased. In the treatise, influences on different amount included of steel fiber in above CL40 ceramsite concrete on compression, pulling, bending strength and bending resistant toughness and compression toughness are tested and researched.

Abstract: Test the alkali-silica reactivity of slate aggregate in Guizhou using mortar-bar method in JTG E42-2005of China and accelerated mortar-bar method in TB/T2922.5-2002 of China. The results show that the six months expansion is 0.11% with mortar-bar method, the aggregate has low alkali activity. The 14-days expansion exceeds 0.30% with accelerated mortar-bar method, according to the TB10005-2010, the aggregate has high alkali reactivity. Obviously, the accelerated mortar-bar method is safer than the mortar-bar method, but the test parameters and test conditions of accelerated mortar-bar method have some differences with the aggregate physical environments. According to the accelerated mortar bar method, the thesis proposes an improved test method for evaluating the alkali-silica reactivity of slate aggregate.

Abstract: A displacement sensor was designed and made for the deformation modulus test of plastic concrete according to the method of full gauge measurement. Such parameters as sensitivity, linearity and repeatability, etc. were obtained after the calibration of the sensor. The results show that the indicators have met the requirements on the class-1 precision. The results from the practical application of engineering test indicate that the designed displacement sensor which is easy to use and high in the degree of precision can meet the needs of practical application of engineering.

Abstract: In China, the soaring red mud needs outdoor place for stockpiling. The traditional building method of tailing dam is often construction dam only once, which needs the biggish piling up yard or quantities of dam. The construction-dam technology of “three-dimensional seepage drainage stack” was proposed, combining stereoscopic drainage discharging separated water and rainwater, geogrid reinforcement minishing fissured development and enhancing dam stability, and air dry in turn. Using bayer red mud to build dam quickly comes true. The experiment of the method was carried on and makes some conclusions through testing strength indexes: after depositing bayer red mud 4~5m heights continuously, and the ten-days air-curing drying, red-mud strength indices have been improved greatly and it can be used to damming. The way of “three-dimensional seepage drainage stack” makes good use of waste materials，reduces the yard space, saves the red mud rolling or compaction equipment, economizes the constructed cost of the dam. The process provides some references in the field of the bayer red mud as quick damming material in the practice.

Abstract: In construction of medium span, small span and commonly long span bridges, the prestressed concrete continuous beams are playing an important role and the vistas of development of the bridges is vast. The design , construction and new material application remain to be further improved, through great achievements has been made in China in the construction of the PC continuous beam bridges, the global techniques of the bridges in the country in the recent several decades. Through the study of prestressed concrete continuous beam bridge construction technology development trend and research, understand the international bridge of advanced design concepts and construction technology of foreign engineering project bidding, formulates the reasonable construction plan, strengthen the domestic enterprises to expand overseas bridge construction market competitive force, and provide useful reference.

Abstract: Alkalinity of the surroundings is the basis to study the MICP technology. Alkalinity of pore solution and strength of cement paste made of various cementitious materials were studied. Results show that the alkalinity of pore solution of cement paste decreased with the increase of sulpho-aluminate cement content. pH value of cement paste was about less than 10 when sulpho-aluminate cement content exceeded 75%. Incorporation of sulpho-aluminate cement decreased compressive strength of paste obviously; however, compressive strength of paste was improved when the addition of sulpho-aluminate cement was more than 75%. Addition of mineral admixtures reduced the alkalinity of pore solution of cement paste and increased its compressive strength. Compressive strength of specimens was decreased when the content of mineral admixtures increased.