Advanced Materials Research Vols. 168-170

Abstract: Surface-adhering-sand screw-thread-form FRP bar was produced. By symmetrical pull-out test research to a certain depth in FRP (Fiber Reinforced Polymer) bar concrete, the bond mechanism, the failure mechanism, the bond strength and the slip of FRP bar to concrete were studied systematically. Studies show that the failure mode is not the damage of the ribs or the shearing off of the ribs, but is shear failure between the screw thread and the core of the FRP bar, and the sands on the surface of the bar were grinded into powder. The descending branch of load-slip curve for the FRP bars is gentler than that for the steel bars. The bond strength of FRP bars is a little lower than that of steel bars, but higher than smooth FRP bar greatly. At last the FRP bar concrete specimen were modeled in ANSYS program and the simulation result is satisfactory, which proves the feasibility to model the behavior of bond-slip relationship between FRP bar and concrete accurately.

Abstract: This study adds nanopowder, such as ZnO and TiO₂, in different concentrations to water-based woodenware coating, and explores the properties of the coating on the woodenwares. After the coating has been applied to the testing materials, the thickness and lightness are measured. These values are compared to the properties of the water-based woodenware coating with nanopowder of specific concentration, such as hardness, lightness and adhesion. According to the results of the experiments, adding TiO₂ nanopowder to the AE-418 water-soluble polyurethane coating helps to increase the hardness of the coating. The amount added is positively related to the hardness of the coating; the result is the opposite with the WP-1715 water-soluble acrylic resin coating. After adding powder such as TiO₂ or ZnO to the AE-418 water-soluble polyurethane coating, the lightness of the coating becomes lower. However, powder with higher concentration leads to higher lightness. In addition, the adhesion of the coating is stronger when nanopowder of higher concentration is added.

Abstract: The flexural fatigue performance of polyacrylonitrile (PAN) fiber reinforced concrete (PANFRC）was investigated by third-point loading tests. Based on the previous research work, optimum mixture proportions of PANFRC for highway overlays and bridge decks that satisfied both the minimum compressive and bending strengths, and showed excellent mechanical properties, were selected for fatigue testing. The experimental program included a total of 69 flexural specimens, 15 of which were plain concrete specimens, and the remaining 54 specimens were PANFRC specimens. Three mixes containing 0.0%, 0.1 %, and 0.15% of PAN fiber volume fractions were selected. For each mix, 4 different target load ranges were applied: 10–75%, 10–80%, 10–85%, and 10–90% of the ultimate flexural capacity, as obtained from the corresponding control static test. The bending fatigue life of PANFRC specimens under various stress ratios are proved to follow two-parameter Weibull distribution. Both a semi-logarithm and a double-logarithm P-S-N equations with various failure probabilities are derived from the experimental measurements. The denifition of the fatigue damage variable and damage evolution equation for PANFRC are furtherly proposed based on theory of continuum damage mechanics.

Abstract: In the process of pull out testing polypropylene fiber, the performance of bonding of tested and untested objects has been microscopically analyzed; both the interface of polypropylene fiber-cement-based material, the hole morphology of cement-based material after the polypropylene fiber being pulled out by force and the condition after the polypropylene fiber being pulled out of concrete-based material are observed. Attachment phase analyses of the surface of the polypropylene fiber and cement-based transverse cracks after the polypropylene fiber being pulled out have both confirmed the fact that the performance of bonding of the polypropylene fiber-cement-based material can effectively transmit the outer force borne by the polypropylene fiber and that the performance of bonding of the polypropylene fiber-cement-based material is better.

Abstract: The use of steel tube confined concrete columns has been the interests of many structural engineers. For investigation of the axially loading capacity of short concrete filled double skin tubes (CFDST) columns, axial compression loading experiments were carried on 9 short CFDST column samples. According to experimental results and with numerical analysis, an ultimate load estimation equation of CFDST column with one correction parameter is presented, the linear relation between the parameter and the inner-to-outer diameters ratio Di/Do is given out. The ultimate load estimation equation is validated by the test results of short CFDST column samples.

Abstract: By the application of esterification-polymerization two-step synthesis method, comb-shaped polycarboxylate slump-loss resistance agent XBT for small slump concrete is prepared by controlling ester ratio. The experimental results of concrete and fresh cement paste indicate that XBT has excellent function of plasticity retention in small slump concrete. The experiment of gel permeation liquid chromatogram shows that XBT has wide range of molecular weight distribution, which may be the source of fine plasticity retention performance in the small slump concrete. The combined experiment between ultraviolet and conductivity indicates that there is strong adsorptive action between XBT and Ca2+, and their adsorptive characteristics may be closely related to the plasticity retention properties.

Abstract: The construction reject is in the building construction, the service, the demolition process produces, mainly is the solid reject, including the waste cement block, the asphalt cement block, in the construction process scatters the waste material, each kind of packing material and other rejects which the mortar and the concrete, the broken brick dregs, the metal, the bamboo lumber, the decoration repair produces and so on. In view of the fact that the construction trash composition characteristic and it produces in the construction project scene actual situation, its recycling took the building material, is constructs the waste disposal use the effective method. This article has carried on the comprehensive investigation and the summary to the domestic and foreign construction trash government present situation and the comprehensive utilization technology, has analyzed the construction reject ingredient and the characteristic, has conducted the system analysis research to our country construction reject comprehensive utilization and the construction energy conservation question, and proposed suits our country national condition the construction reject circulation in the construction energy conservation comprehensive utilization.

Abstract: This paper reports the results of an investigation of chloride ion penetration and diffusion for high performance concrete. Concrete was prepared incorporating pulverised fuel ash (PFA) and silica fume (SF) with various water-binder ratios. Chloride ion penetration was measured at various ages using rapid chloride permeability test in accordance with ASTM C1202-91. Based on experimentally obtained results, isoresponse contours for chloride permeability were developed showing the interactive and optimized effect between the various parameters investigated. Diffusion coefficient of concrete was determined applying Fick’s law of diffusion. The results show that the inclusion of PFA and SF reduced both chloride permeability and chloride concentration of concrete. It was found that rapid chloride permeability values were consistent with diffusion coefficient of concrete.

Abstract: The mechanical properties of concrete mixed with composite coarse-aggregate were studied by the orthogonal test method, in which the four factors such as the cement content, the percent of cement replaced by fly ash, the percent of crushed limestone with grain size of 16-25 mm replaced by lightweight aggregate with the same grain size and the water to binder (cement + fly ash) ratio were considered. The results show that the water to binder ratio is the most effective factor influencing all of the mechanical properties, the mechanical properties except the splitting tensile strength are less influenced by the cement content, the elastic modulus and axial compressive strength as well as flexural tensile strength is largely affected by the replacement of cement by fly ash. The effect of the replacement of crushed limestone by lightweight aggregate is much more obvious on the cubic compressive strength than on the axial compressive strength, and larger on the flexural tensile strength than the splitting tensile strength.

Abstract: Concrete beams reinforced with fiber reinforced polymer(FRP)bars exhibit large deflections and crack widths as compared to concrete beams reinforced with steel due to the low modulus of elasticity of FRP. Consequently,in many cases,serviceability requirements may govern the design of such members. This paper describes six partial bonded concrete beams prestressed with CFRP tendons are tested under monotonic loads. deformation and crack width of this kind of beams with varying unbonded length are systematically investigated. The predictions of the 《Code for Design of Concrete Structures》（GB50010－2002）equations are compared with the experimental results obtained by testing six partial bonded concrete beams prestressed with CFRP tendons. Good agreement was shown between the theoretical and the experimental results.