Advanced Materials Research Vols. 168-170

Abstract: According to the principle that fiber resist crack and cement-based capillary crystalline impermeability, the paper chose the mortar added with polypropylene fiber and SJ capillary crystalline material as the research object. Experiments on mechanical properties, crack resistance and impermeability of mortar were conducted with one material being added to the mortar as well as both materials being added to. The test results indicate that the ratio of compressive strength to flexural strength of mortar could be reduced, the time of cracks occurrence in mortar matrix would be delayed, and the minimum cracking coefficient can amount to 5% on the condition that the two materials are both added to the mortar, moreover, the mortar’s first and second impermeability is significant. Furthermore, the paper also discusses the mechanism of mortar’s crack resistance and impermeability which is mixed with polypropylene fiber and capillary crystalline material.

Abstract: Uniaxial compression and acoustic emission experiments of calcareous mudstone with different water content were carried out by using microcomputer controlled electro-hydraulic servo compression testing machine control system of YAW series equipped by coal-rock acoustic and electric data acquisition system of CTA-1-type. Mchanical properties and acoustic emission law of calcareous mudstone were studied. It is concluded from experiment result that rock’s elastic modulus and compressive strength both decrease with increase water content but peak stress shows the opposite trend. It is also found that calcareous mudstone is brittleness with low water content but when water content reaches saturation, calcareous mudstone presents plastic features. Acoustic emission curve fits well with stress-strain curve: acoustic emission activity begins intensifying when stress reaches 70% of peak stress, correspondingly, acoustic emission is up to maximum at peak stress. Based on Weibull hypothesis and acoustic emission experiment, damage law of water bearing calcareous mudstone is researched and damage evolution equation with time variable is advanced.

Abstract: Steel Fiber Reinforced Self-stressing Concrete (SFRSSC for short) is a new type of high performance cementitious composite with self-expansive performance and high crack resistance. SFRSSC is actually a kind of expansive concrete which self-stresses, namely pre-compressive stresses, are induced by dint of some restrictions generally provided by steel bars and steel fibers to concrete expansion after hydration of expansive cement. As a result of chemical reaction, concrete achieved pre-stresses by itself different from mechanical pre-stressed concrete, so called steel fiber reinforced self-stressing concrete. In this paper the material experiments of 40 SFRSSC prisms are carried out to determine the rule of the self-expansive behavior. According to the theoretical model, a procedure how to determine the self-stress is supplied in order to supply references to the structural applications of steel fiber reinforced self-stressing concrete.

Abstract: After the reform in China, our new building materials industry has developed rapidly. After 30 years of development, China's new building materials industry occurred and is developing from small to large. It has formed a new industry, become an important product of industrial materials and promoted China's economic growth. On the contrary, the rapid development of economic construction and the rising living standards provide the development of new building materials with a broad market and good opportunities. Driven by market demand, new building materials in China has formed a circulation network; Most of the foreign products can be produced in China, for example, China's production of different varieties of the color and different grades of decorative materials to improve the living conditions of urban and rural residents and make great contribution of changing the appearance of the city. China has formed a professional team for new building materials’ research, production and circulation. In this paper, we analyzed the current situation of the development of new building materials and put forward some countermeasures and suggestions to promote the development of new building materials.

Abstract: The study presented herein has been carried out in order to investigate the chloride diffusivity of recycled aggregate concrete (RAC). Meanwhile, the effect of the binder type, involving cement replacement materials such as, fly ash, slag and silica fume on the chloride diffusivity has also been investigated. For this purpose, RAC and concrete containing the different type of binders with w/b ratios of 0.35, 0.40, 0.45, 0.50, 0.55, and 0.60 were used. As a result, the chloride diffusion coefficient of RAC is higher than that of natural concrete and the partial replacement of cement with fly ash, slag and silica fume is effective in decrease in the chloride diffusion coefficient, measured by a rapid chloride conductivity test.

Abstract: The resistivity characters of concrete with fly ash and slag are studied by four-pole method. The results indicate that concrete resistivity gradually increases with the content of fly ash or slag increasing within a given content scope. Fly ash can promote the concrete resistivity after long-term curing (＞28 days) and slag will increase the concrete resistivity during the early curing time (≤28d). When two mixed fly ash and slag, the effects of the ratio of them on concrete resistivity are similar to that of single mixed fly ash or slag. Otherwise, the change tendency of concrete resistivity are presented first increase and then drop with the content of mineral admixtures increasing, and concrete resistivity reaches the maximum when the total content is 30%.

Abstract: This paper addresses mainly workability of dry-mixed self-compacting concrete (DSCC) based on the experimental study. Ten mix proportions for DSCC are designed by the orthogonal test method with fixed fine and additive content when coarse aggregate content and water content are used as variables. The workability (including filling ability, passing ability and segregation resistance) of fresh DSCC is quantitatively evaluated by slump flow, L-box, U-box and circular steel column of stability tests. It is found that DSCC of 13% water content has better fluidity, deformability and filling ability than DSCC of 12% water content and better uniform aggregate distribution and segregation resistance than DSCC of 14% water content based on the experimental results. It can be concluded that DSCC of 13% water content presented in this paper satisfy various requirements for workability and can be used for the design of practical concrete structures.

Abstract: Using the electrostatic spraying method to spray the epoxy coating on the surface of prestressing wire or strand. By this method, the mechanical properties can reach the same level of original prestressed steel, the anti-corrosion ability is superior to that of galvanized steel, and the epoxy coating not only does not have a negative impact on anchorage performance, but also improve the bond strength between wire and cold-cast filler. The LZM cable system using epoxy-coated wire and the OVM250 and GJ cable system using epoxy-coated strand have been developed and widely applied in China since the year of 2001.

Abstract: According to the typical loess in Shuozhou in Shanxi province, tests involved in compaction characteristics, shearing strength characteristics and disintegration are carried out by using loess and three kinds of improved loess, namely lime and fly-ash, lime and cement, cement and fly-ash. The best improved soil method is selected. The test results indicate that the compact hybrid structure is formed by fly ash and loess. The activity of fly ash is activated as a result of the lime mixing. A series of hydration reaction prompt the intensity of modified loess. And the physical and mechanical properties of improved loess are improved noticeably.

Abstract: The Low-Carbon economy enhances the use of renewable energy for indoor environmental control. River water could be a nice renewable energy as it can be used as a lowstand heat/cold source to control the indoor environment through Water Source Heat Pump (WSHP) units. However traditional WSHP units are not applicable because the high cost of water treatment to improve the present water property, and the advantages of the WSHP are badly restricted. To overcome the limits of the present WSHP units, we develop an integrated heat exchanger for which the river water or waste water can be effectively used as a cooling medium while heat exchange is keeping and the exchanger is being cleaning. The newly-developed heat exchanger can keep effective operation and well realize the energy saving.