Applied Mechanics and Materials Vols. 368-370

Abstract: The aim of the study is to improve the understanding of the influence of reinforcing fiber types on the mechanical properties of high performance concretes (HPC) subjected to high temperature. The mechanical properties measured include residual compressive strength, weight reduction ratio, outward appearance property, and failure mode. Nylon, polypropylene, and steel fiber were added to enhance mechanical property of the concretes. After exposure to high temperatures ranged from 100 to 800°C, mechanical properties of fiber-toughened HPC were investigated. For HPC, although residual compressive strength was decreased by exposure to high temperature over 500°C, weight reduction ratio was significantly higher than that before heating temperature.

Abstract: Pavement surface characteristics play an important role in accident occurring, especially in wet conditions: the optimization of surface performance starting from hot mix asphalt (HMA) design phases is a fundamental requirement in road construction techniques. Although such relevance, the prediction of surface properties based on HMA composition and construction still calls for further research. Indeed, there is not a clear framework for a mix design oriented to surface properties. In the light of the abovementioned facts authors efforts were focused into the analysis of the most significant factors influencing pavement surface macrotexture, by analyzing the main variables of existing macrotexture prediction models. Many experimental mixes were designed and produced. Some statistical correlations between macrotexture data and mixes grading and volumetric properties were also carried out. Outcomes of this study are expected to benefit both practitioners and researchers.

Abstract: This paper evaluates the effect of Ultrafine Fly Ash (UFFA) and nanoSilica (NS) on compressive strength of high volume fly ash (HVFA) mortar at 7 days and 28 days. Three series of mortar mixes are considered in the first part of this study. In the first series the effect of high content of class F fly ash as partial replacement of cement at 40, 50 and 60% (by wt.) are considered. While in the second and third series, the UFFA and NS are used as partial replacement of cement at 5%, 8%, 10%, 12% and 15% and 1%, 2%, 4%, 6% and 8% (by wt.) of cement, respectively. The UFFA and the NS content which exhibited highest compressive strength in the above series are used in the second part where their effects on the compressive strength of HVFA mortars are evaluated. Results show that the mortar containing 10% UFFA as partial replacement of cement exhibited the highest compressive strength at both 7 and 28 days among all UFFA contents. Similarly, the mortar containing 2% NS as partial replacement of cement exhibited the best performance. Interestingly, the use of UFFA in HVFA mortars did not improve the compressive strength. However, the use of 2% and 4% NS showed improvement in the compressive strength of HVFA mortar containing 40% and 50% fly ash at both ages. The effects of NS and UFFA on the hydration and strength development of HVFA mortar is also evaluated through X-Ray Diffraction (XRD) test. Results also show that the UFFA and NS can significantly reduce the calcium hydroxide (CH) in HVFA mortars.

Abstract: In this paper the anticorrosion properties of steel bars coated with polymer modified cement-based coatings in chloride solution were evaluated. Then the pullout tests were conducted using coated and uncoated steel bars embedded in concrete specimens and the bond properties between concrete and bars were tested. The results show the steel bars coated with epoxy emulsion modified cement-based coating (HY) and elastic copolymer emulsion modified cement-based coating (GT) have satisfactory anticorrosion properties in 3.5% NaCl solution for 96h. But the pullout tests display that the bond strength between the concrete and the steel bars coated with GT coating is much lower than that of the bars coated with HY coating and the uncoated specimens. The bond stress between the concrete and the bars coated with pure acrylate emulsion modified cement-based (CB) coating is the highest among the three coatings, but the resistance to chloride permeability of CB coating is poor. The results indicate the special epoxy-cement-based coating (HY) is more suitable for applying to the anticorrosion coating for steel bars in chloride condition.

Abstract: The material moisture affects directly the appearance of the building construction and the performance of interior micro climate environment. In this study, it was discussed the damp and efflorescence disease mechanism of masonry construction through Lab experiments. It was taken the results of the difference with the mortar between lime and cement, which will cause the different damp diseases.

Abstract: Using the same water to binder ratio and the same ratio of reinforcement, the three recycled aggregate concrete are made in different replacement ratio of recycled coarse aggregate which is 0%, 30%, 75% and 100%. Through experimental the beams flexural performance is researched, the right sections bearing deformation performance and damage distinction. The result shows that the damage model and the damage process are basically the same; the right sections mean strain is uniform to plane section assumption. With the increase in the replacement ratio of recycled coarse aggregate, the value of recycled concrete beams cracking moment, yielding bend moment and ultimate moment are all decreasing, the deflection and the maximum crack depth is increasing and the maximum crack depth is decreasing. The experimental and theoretical analysis shows that the existing norms formula is accurately applied in calculating the recycled concrete beams ultimate moment, and the formula is need to be amendment when calculating the cracking moment.

Abstract: Recycled aggregate performance vary with different native concrete strength and use environment. Recycled fine aggregate was obtained after the primary concrete was broken and screened. According to Recycled coarse aggregate for concrete and mortar (GB/T 25176-2010), the physical properties of the different types of recycled fine aggregate were analyzed, in addition, determine the classification. The results shows that the properties of recycled fine aggregate all meet the level and they are vary by strengths of its maternal primary concrete and using environments. The overall performance of fine aggregate of high strength primary concrete is the best, followed by the low strength concrete and the moderate strength concrete.

Abstract: In this study, the building roof heat insulation structure was experiment and analysis. The simple approximation of a theory of thermal resistance network of the heat insulating structure was analyzed. The finite element method is proposed to evaluate the thermal characteristics of building components. The comparison between the finite element method and the thermal resistance network method was conducted by testing the thermal resistance of a concrete hollow block. Through the analysis of finite element method, the thermal resistance network and experimental validated, it is concluded the finite element analysis not only to calculated accuracy requirements but also has application in the form of the type of hole, material composition, intuitive analysis results. In the absence of test conditions or thermal performance test is not required, it is recommended to use finite element method to analyze problems.

Abstract: Study four factors - water consumption , water-cement ratio , recycled fine aggregate replacement ratio of recycled coarse aggregate replacement rate - affect the regularity of the load-bearing hollow block compressive strength of recycled concrete by orthogonal test method , the test showed that , water consumption factors affect the compressive strength of recycled concrete block design with than the emphasis on the control of water consumption . Under the test conditions , the optimum mixture ratio of recycled concrete load-bearing block : water consumption of 160 kg / m 3 , the water cement ratio 0.45 , recycled fine aggregate replacement ratio of 30% recycled coarse aggregate replacement ratio of 30% .

Abstract: Artificial neural network (ANN) is applied to predict load-strain relationship of concrete filled steel tube (CFT) structural parts. An ANN prediction model, which is able to predict load-strain relationship of CFT structural parts with different dimensions and parameters, is made through training the ANN prediction model with the experimental test data. Furthermore, the prediction data and experimental test data are compared. The result shows that the combination of several characteristic parameters of CFT structural parts and ANN prediction model to predict load-strain relationship of CFT structural parts are reliable and feasible. The ANN prediction model has simple, convenience and time-saving merits.