Applied Mechanics and Materials Vols. 253-255

Abstract: Redispersible polymer powder of vinyl acetate and versatate copolymer (VA/Voeva) used as admixture additive, is introduced to modify lightweight cement mortar with ground granulated blast furnace slag, quartz sand and expanded perlite as aggregates. The effect of the dosage of redispersible polymer powder of vinyl acetate and versatate on the compressive and flexural strengths was investigated in details. The ratio of compressive strength to flexural strength (σc/σf ) of cement mortars varied with the variation of the dosage of redispersible polymer powder. Scanning electronic microscopy was used to investigate the internal structure of the polymer-modified lightweight cement mortar. The result showed that the toughness of the polymer-modified lightweight cement mortar was improved with the increase in the dosage of redispersible polymer powder, and the network membranous structure formed by the polymer attribute to the improvement of the toughness and flexural strengths.

Abstract: Investigation to the source of aggregates used in engineering in Kaifeng area was carried on. The aggregates used in experiment came from main places supplying concrete aggregates for projects in Kaifeng. By the Autoclaved Method, the ASTM C1260 Method, Accelerating Mortar-bar Method (10mm×10mm×40mm in dimension) to determine whether the concrete aggregates has alkali-reactivity. The results show that 14 days expansion rate of each sample is less than 0.1% and the aggregates have no activity.

Abstract: A new protective material-steel mesh reinforced concrete was developed under the condition of modern high-tech weapon development. The comparative tests were conducted with steel fiber reinforced and steel reinforced concrete. The enhancement characteristics of three composites were analyzed in the respects of base material, the distribution of reinforced material and its bonding. The results indicate that steel mesh reinforced concrete is the most effective composite resisting penetration.

Abstract: Fine aggregate can be extracted from waste concrete by series of processing. The recycled fine aggregate can then be utilized to manufacture recycled fine aggregate mortar (RFAM) or recycled fine aggregate concrete (RFAC). Air entraining agent was added in RFAM to improve its mechanical performance. The influence of the dosage of the air entraining agent on both the compressive and flexural strength of the RFAM was explored after 7 days and 28 days curing. The optimum dosage of the air entraining agent was determined.

Abstract: A new type of lightweight cement mortar was developed by using ground granulated blast furnace slag, quartz sand and expanded perlite as aggregates which were mixed with cement homogeneously. Consistence was used to characterize the workability of lightweight cement mortar. The effect of the components, including the proportions of granulated blast furnace slag and the addition of fly ash, on the properties was investigated in details. The results showed that the values of compressive and flexural strength increased with the ratio of slag to sand. Additionally, the introduction of fly ash improved the consistency and strength properties of lightweight cement mortar.

Abstract: The sealing concrete of arch bridge will be constructed after swivel construction of it finished. The concrete has such characteristics like huge size, smaller heat radiating area and more complex boundary constraint. According to the cracking situation of this type bridges in recent years, the paper established hydration heat simulation model of it using MIDAS2010 program and numerical analyzed for the model. The hydration heat constant coefficients and placing temperature of the concrete hydration heat effect have been analyzed by simulation parameters base on that. And the results showed that it is an important reason causing the cracking of the concrete.

Abstract: Scattering electromagnetic function mortar composites was prepared by use of addition graphite into cement. The influence of graphite to mechanical properties and absorbing electromagnetic wave properties of cement mortar were researched. Electromagnetic characteristics of mortar composite was measured using the naval research laboratory(NRL) testing system. The results showed that graphite content had obvious effect on mechanical properties of mortar composite. Descended velocity of strengthen of compressive and flexural-tensile was farer when graphite content were bigger. In 2-18GHz frequency, reflectivity of composite was fluctuation at between -1.5 and -6.2dB when graphite content added from 15% to 22%. The matching ability of surface impedance and free space impedance could be improved and reflection loss of electromagnetic wave could be decreased by increasing graphite addition.

Abstract: The development of competitive Dragon and Lion Dance movement promotes the innovation of its equipment materials in return, so applicable and practical equipment is the basis for the development of competitive Dragon and Lion Dance sport. However, with the rapid development of sports Dragon and Lion Dance movement, its used equipment has seriously lagged behind in technological development. Some equipment is not easy to handle, some can’t be reused and even lead to injury in athletes or other problems. Therefore, based on the research into the development and innovation of new materials with the method of the expert interview、questionnaire and visit investigation, a set of perfect ideas on selecting competitive Dragon and Lion Dance sports equipment are formed preliminarily. The writer hopes for providing a theoretical reference for the Dragon Lion Dance Competition Organizing Committee, the Dragon and Lion Dance teams and coaches, which promotes the further development of Dragon and Lion Dance movement.

Abstract: Frost resistance research is one of the important subject of concrete durability, however strength criteria is an important part of the study of mechanical behavior of concrete. So far, about concrete failure criteria are almost for normal concrete, which the domestic and overseas scholars have comparative detailed research in every respect to it, and to freeze-thaw damage of concrete but few research. Based on the summary of the existing ordinary concrete strength and failure criteria in normal state and after freeze-thaw damage，this paper have a brief comment of failure criteria on concrete after freeze-thaw damage. For later research about concrete strength and failure criteria under freezing and thawing cycle provide the reference.

Abstract: In this paper, the high-volume limestone powder and low-quality fly ash are mixed to replace the cement to prepare green concrete, and then its work performance, mechanical properties and microstructure are studied. The test results show that the green concrete prepared by 50% cement and 50% of the mixture of limestone powder and low-quality fly ash has good performance, for its slump loss in 60min is relatively small. The mixture of limestone powder and low-quality fly ash has good composite effect, which endows the concrete the required compressive strength. The scanning electron microscope reflects the good combination of cement paste and the aggregate interface in the concrete, as well as the dense concrete structure.