Advanced Materials Research Vols. 450-451

Abstract: To make nano calcium carbonate as the modifier, firstly the best proportion of nano calcium carbonate is determined as 6% by comparing the influences of different proportions of nano calcium carbonate to the indexes of asphalt. Then the influence of mixing with nano calcium carbonate to the performance of asphalt concrete AC-13 has been studied. Tests show that, the mixing of 6% nano calcium carbonate has improved the dynamic stability of asphalt concrete AC-13 from 991 times/mm to 1269 times/mm; the residual stability from 0.87 to 0.94. This indicates that after mixing with nano calcium carbonate, both the high temperature performance and water stability of asphalt concrete have been improved.

Abstract: During the process of Vacuum Assisted Resin Transfer Molding（VARTM）making flame retardant wind turbines nacelle, the viscosity of unsaturated polyester resin（UPR）with reactive flame retardant groups is too large to be used in VARTM process. In this paper, a large amount of tests were conducted by the way of adding flame retardant of Dimethyl methyl phosphate(DMMP) so as to make the resin fit for VARTM processing properties requirements as well as increase its flame retardant properties to a higher level. The results showed that, when the content of DMMP was 12%, the resin could be provided with lower viscosity with a reduction of 50.3%, making it possible for the resin to be used in vacuum import process. When the content of DMMP reached 12%, LOI of the casting body reached 31.6, with LOI of glass fiber reinforced plastic of 37.0%, the vertical burning classification of which reached V-0 level without significant drop on mechanical properties of fiberglass reinforced plastics(GFRP). Meet the requirements and provide a good material for flame-retardant wind turbines nacelle.

Abstract: In this study, Through the research of the porous concrete which have special structure,without sand and added PVA fibers form a fiber cement-based materials as the bonding materials of porous concrete. The results show that after mixed with quantitative PVA fibers, the bonding performance of the porous concrete aggregates can be enhanced, the flexural strength obviously improved, obtained the effective porosity and the best PVA fiber contents.

Abstract: Though fracture test on the fifteen specimens with notch of hybrid fiber reinforced concrete with the size of 100mm×100mm×400mm, this paper explores the hybrid effect between steel fiber and polypropylene fiber and impact on the fracture properties, such as critical effective crack length, critical crack tip opening displacement, effective stress intensity factors and fracture energy. The test results indicate that the addition of fiber is helpful to improve the fracture properties of concrete. Synergistic effect of two kinds of fibers is good, the steel fiber with high elastic module can restrain the cracking of concrete when the crack displacement is small, polypropylene macro-fiber with high ductility is more beneficial to increase the fracture properties of concrete than steel fiber when the crack displacement is big. The best fiber compounding can be gotten when the volume fractions of steel fiber and polypropylene fiber is respectively 0.5％and 1.0％in this experiment.

Abstract: The dynamic compression tests of reinforced concrete with different reinforcement ratios are carried out by split Hopkinson pressure bar (SHPB). Reinforced steel bar is placed along longitudinal and transverse direction. Experimental results show that reinforced concrete is non-linear and rate-dependent. With the enhancement of strain rate, the peak stress of reinforced concrete increases correspondingly

Abstract: This paper focus on the high temperture performance of asphalt mastic based on repeated creep and recovery test.Asphalt mastic with four mineral filler(limestone,fly ash,hydrated lime and cement)was studied.According to the research result,it showed that asphalt mastic with different mineral filler has different rheology properties,coincide with test result of mixture.

Abstract: For well application in north of China, the optimal properties of phase change materials was screened out by comparing with the same adsorbing material – perlite in Lab conditions. Three main influence factors including adsorption time, experiment temperature and particles of expanded perlite were investigated for all sample of phase change materials. The results showed that capric acid is the optimal one of all samples due to its suitable transformation temperature at 30.1 oC and relative high adsorption proportion of 140% on the vacuum condition at 60 oC in 45 min. All experiments could provide useful data for the building energy saving of Tangshan district.

Abstract: Pumpkin（Cucubita pepo L.）seedlings were exposed under different low temperature-light regimes to investigate the responses of photosynthesis and chlorophyll fluorescence to the stress. The results indicated that the contents of chlorophyll increased at first day after treatment and then decreased under special temperature(15/5、20/10、25/15°C )and poor light(50、150、250μmol•m-2•s-1).The net photosynthetic rate, evaporation rate, stomata conductance and intercellular CO2 concentration increased one day after treatment and then decreased, stomata limitation increased above15/5°C special temperature and special poor light. However, under 15/5°C temperature and special poor light, the net photosynthetic rate, evaporation rate and stomata conductance decreased, and intercellular CO2 concentration increased stomata limitation increased in 4 days after treatment then decreased. Ft、Yield(F/Fm’)、qP decreased under special temperature and poor light.The change of these parameters were less under the light density of 50μmol•m-2•s-2 than other light densities, which means that poorer light reduced the sensitivity of pumpkin to low temperature and increased the photochemical activity of PS, but the photochemical quenching (qP) decreased and the non-photochemical quenching(qN) increased at the same time.

Abstract: In order to study the compatibility between polycarboxyIn order to study the compatibility between polycarboxylates superplasticizer (PC) and different kinds of retarders, sodium citrate (SC), sodium gluconate (SG), sodium hexametaphosphate (SH) and sucrose (SU) were compounded with PC respectively in the same proportion. The liquid degree and its loss of cement paste, the setting time of cement, the blending strength and compressive strength of mortar that admixed with different kinds of retarders were measured, and the influence mechanism of the compatibility between different kinds of retarders and PC were analyzed. The experiment results showed that it was benefit to the liquid degree of cement paste after SG or SH or SU was compounded with PC; The setting time of cement could prolonged more by SH or SU; Blending and compressive strength of mortar in different ages were enhanced in large extent after SG were adopted; The strength of mortar was reduced in early age and enhanced in small extent in mid-later age after SU was compounded. Comprehensively considering to the influence of liquid degree, setting time and strength, the compatibility of SG with PC is higher than other kinds of retarders.

Abstract: Xylitol residue from corn cob was modified by alkaline sulfonation to produce lignosulfonate with good properties for concrete water reducing agent. Results showed that the optimum condition for lignin sulfonation was: total alkaline charge (calculated by Na2O) 16%, cooking temperature 170°C, holding time 3h, degree of sulfitation 80%. The yield of lignosulfonate at this condition was 68.1%. The fluidity of cement paste could reach 124mm when lignosulfonate dosage was 0.35% (on the base of solids). The surface tension of 1% lignosulfonate solution was 46.1 mN/m, and the content of sulfonic group was 2.16 mmol/g.