Applied Mechanics and Materials Vols. 193-194

Abstract: The emission of volatile organic compounds (VOC) from single-component polyurethane varnish applied to beech plywood at two temperatures (33°C, 43°C) has been investigated in a small environmental chamber. The experimental results indicated that the concentration of each compound, as well as the total volatile organic compounds (TVOC), increased rapidly after the start of experiment, and attained their maximum values at 0.5 h. The concentrations decreased rapidly after 0.5 h, and then decreased more slowly in the period 2 – 24 h. The concentrations of isopropylbenzene, n-decane and TVOC were higher in the 43°C test than in the 33°C test within the first 1.5 h. The influences of temperature on the concentrations of these pollutants were different during the period 1.5 – 24 h.

Abstract: This paper studies the effects of high-volume composite mineral admixture made of limestone powder and low-quality fly ash on the properties of concrete. Through experiments, this paper makes clear the workability of fresh concrete and analyzes the law of strength development of concrete. The experimental results indicate that the concrete with high-volume limestone powder as composite mineral admixture has good fresh properties; due to low water consumption per unit volume, medium-and-high-strength concrete can be prepared. As new type concrete mineral admixture, the composite mineral admixture made of limestone powder and low-quality fly ash will play an active role in the sustainable development of concrete industry.

Abstract: This article put forward several suggestions for the design of new type of fire insulation materials, and cited several new types of fire protection materials; advocate the use of fire insulation materials to prevent fires from the material roots.

Abstract: Multi-walled carbon nano-tubes and carbon fiber reinforced epoxy resin (MWCNTs/CF/EP) composite patch was prepared by the route of hot-melt impregnation. The results of the mechanical properties shown that adding MWCNTs had made the tensile strength and interlaminar shear strength increased by 9.79% and 3.1%, separatively. It was detected using the ultrasonic non-destructive technique that the composite patch had a good interlaminar combination with no defects as obvious resin enrichment or insufficient gel content except for some slight stratification phenomenon in few parts. The high heat-resistance obtained by TG.

Abstract: A large amount of research has been published in Taiwan on the reduction of the urban temperature for different strategies. The most important strategy for reducing ambient temperature is increasing green space in city. For analyzing the effect of the vegetation on the thermal environment, this paper collects temperature data from one green roof and one normal roof which are belong to a same office building to analyze the thermal influence of vegetation. The result of this research shows that in summer the maximum cool effect of green roof was -1.60 oC and -0.26 oC in average. Therefore, it can also provide useful data to governments for calculating the environmental benefit if they carry out a green roof policy in mitigating heat island effect in the future.

Abstract: In order to analyze the residual mechanical properties of concrete frame structures after fire, a novel numerical model considering the distribution of non-uniform temperature in the cross-sections of structural members and the changing of mechanical properties of materials damaged by fire is developed in this paper by dividing the cross-sections of structural members into a lot of concrete fibers and steel fibers based on the concept of fiber model. Besides, the Analytical System of Fire-damaged Concrete Frame (ASFCF) is established through the secondary development of ABAQUS Software that is completed by the programming language of Python. This system is used to analyze the temperature fields and the nonlinear mechanical performances of a multi-story, multi-span, three-dimensional concrete frame after fire. The results indicate that ASFCF can properly analyze the mechanical properties of concrete frames after fire, and it provides valuable references for assessing the residual mechanical properties of concrete frames after fire.

Abstract: In the laboratory synthesis a colorless superplasticizer , through to the mixed quantity of it, whiteness value, decrease water rate and the strength of the performance test, get: this colorless superplasticizer excellent performance, accord with concrete superplasticizer performance index, and applied to the decoration of concrete flip chart, and good results have been achieved.

Abstract: Based on orthogonal test with steel slag and desulfurization gypsum as main raw material, mixed appropriate amount slag and compound addition a little of activator, we explored the slag dosage, the proportion of the combined admixture activator and the desulfurization gypsum dosage impact on the performance of clinker-free cementing material, such as strength, stability, standard consistency water quantity and setting time. The results showed that the best mix proportion of cementing material with slag content 40% and activator A:activator B is equal to 2.78:2.22. We explored the structure and composition of hydration products further more by micro-analysis, such as SEM, EDS and so on. We can found that the cementing material hydration products similar with hydration products of silicate cement. The cementitious material hydration with Afm crystal content increased significantly. The Aft crystal generated in early hydration(3d) gradually transformed into Afm crystal in late hydration(28d) ,and the structure becomes more dense.

Abstract: Low field NMR, as a nondestructure and noninvasive method was employed to study the evolution of various states of water in blended cementious materials added with fly ash during hydration from 1 day to 100 days. The relative content of water held in series of pores in cement matrix, e.g. capillary pore, mesopore and gel pore, was determined based on the quantitative relationship between transverse relaxation time, T₂, and pore dimension. The results indicated that the relative content of chemically bound water was higher at long-term cure of 100 days compared with the neat cement paste. The water distributed in various pores was also influenced by the pozzolanic reactions between fly ash and calcium hydroxide. The gel water and mesopore water increased dramatically during the short-term age of 1 to 7 days in blended matrix, but then decreased gradually after 28 days, unlike that in pure cement paste. Due to the lower hydration degree in blended matrix, there was still amount of capillary water residual in paste to supply for the further hydration of fly ash.

Abstract: The influence of combination of low density polyethylene (LDPE) and petroleum resin on asphalt was investigated by analyzing the change of its penetration, ductility, softening point and viscosity. The results show that petroleum resin can significantly increase the viscosity of PE modified asphalt, which results in the improvement of the asphalt’s waterproof ability and anti-rutting performance in a certain degree. However, the ductility and softening point were negatively affected due to the addition of the petroleum resin. Through analyzing the penetration indexes, an optimal dosage of 8% PE and 5% petroleum resin can be determined, respectively.