Advanced Materials Research Vols. 250-253

Abstract: This paper presents an experimental investigation on tensile basic creep behavior of HPC at early ages by using a uniaxial tensile creep testing apparatus. Concrete specimens of 100×100×400mm with compressive strength class 60MPa was used, sealed and loaded at different curing temperature. The effects of the curing temperature and the age at loading on creep behavior are discussed. The results show that tensile specific creep and creep rate of HPC at early ages were governed by the age at loading. The specific creep, creep coefficient and creep rate were larger at earlier loading ages, and decreased exponentially with age at loading. The tensile specific creep decreased with curing temperature, but the difference in creep due to different curing temperatures decreased with the age at loading, and could be ignored while concrete specimen being loaded after the age of 7 days.

Abstract: The slab filled with Disused Expanded Polystyrene Plastic(DEPP) has many advantages. It is able to save concretes, decrease self weight and improve its functions of heat preservation, heat insulation and sound insulation. It is possible to transform DEPP into treasures and reduce environmental pollutions. So it can be widely used. In this paper, the mechanical properties of the slab filled with DEPP is explored through the experiments. Results show that the structure of the slab filled with DEPP is reasonable and satifies the correlative codes. References to the design of the slab filled with DEPP is also offered in this paper.

Abstract: The hydration degree of binders and cement is investigated by measuring the adiabatic- temperature rise of concrete at low water-binder ratio with different fly-ash content. The results denote that, with a constant water-binder ratio, both of the hydration degree of binders and that of cement decrease with the increasing fly-ash content in the early stage. In a later stage, however, the hydration degree of cement increases with the increasing fly-ash content and the hydration degree of binders peaks when the fly-ash content is 35%. Fly ash is one of the mineral admixture of which high-performance concrete is made up. It brings down the rise of concrete temperature significantly and helps solve the problems of shrinkage and crack of concrete structure. Because the hydration mechanism in common concrete is different from that in concrete with low water-binder ratio, and the hydration environment is different between concrete and cement pastes, to determine the adiabatic-temperature rise of concrete directly conforms to the actual situation. The adiabatic-temperature rise, adiabatic-temperature-rise rate, hydration degree of both binders and cement are investigated by measuring adiabatic-temperature rise of concrete with different fly-ash content.

Abstract: The phenolic(PF) foams were prepared used low-temperature foaming and curing method. The optimum low-temperature foaming processing technology conditions and material proportioning were described below. The curing temperature was 40 °C, the amount of foaming agent iso-pentane was 8-10wt.%, tween-80 dosage was 6-7wt.%, the amount of composite curing agent was 15-18wt.%.The effects of low-temperature foaming on mechanical properties, heat insulation, fire-retardant, foam hole form and micro-structure were discussed. 40°C and 70°C curing PF foam performance comparison results showed that low-temperature curing technology slightly affect the fire-retardant properties of PF foam. And excellent overall performance PF foam were prepared with 40°C foaming technology, the foam hole morphology structure, toughness and strength of PF foam were better. In addition, the low-temperature curing PF foam had more even foam hole distribution, more regular foam hole structure, more clean foam hole arrangement.

Abstract: Fiber-reinforced plasterboard is patent product which was developed by Rapid Build Structure Ltd. of Australia. Fiber reinforced plasterboard can be used as baseboard , and after casting, it integrate with reinforced concrete to make up fiber reinforced plasterboard-reinforced concrete composite floor slabs. In this paper, numerical analysis method is accepted to analyze the process of bearing the loads of fiber reinforced plasterboard-reinforced concrete composite floor slabs. The calculated results, such as load- section strain curve and bearing capacity are compared with experimental data. Based on the results analysis, a mechanical analysis model is built, which provides some reference basis for computer simulation experiment of this type of structure.

Abstract: Orthogonal test method is used to study the effect of the mineral admixtures on the performance of FGD gypsum-fly ash complex cementing material. On the basic experiment, the effect of the traditional alkali and salt admixtures added to the complex cementitious system is discussed, the factors effecting on performance of the FGD gypsum were analyzed. Based on the experimental results, the best mix proportion was determined. Finally, the basic performance of complex cementitious material was tested. The experimental results show that the performance of FGD gypsum which is activated through adding the compound admixtures was similar with the ordinary interior wall materials. The strength and water resistance of FGD gypsum complex cementing material can be greatly enhanced by adding cement, quicklime and slag powder, and effect of cement is largest, and slag smallest. The performance of the gypsum complex cementing material also can be improved after incorporation of a few of chemical admixture on the basis of adding mineral activators.

Abstract: The influence of water binder ratio, content of borax and fly ash on the fluidity and strength of phosphate concrete were investigated. Results showed that the slump and slump flow of phosphate concrete improved with content of water and borax increasing. But the strength decreased, especially early strength. While the mixing amount of borax was less than 1.5% of the magnesium phosphate cement, the influence on later strength was relatively less. The fluidity decreased significantly and the cohesiveness and water retention improved while the content of fly ash was between 10% and 30%.The compressive strength increased while the content of fly ash was 10%.The better curing methods was curing in the natural conditions, the compressive increased with the age prolonged.

Abstract: A kind of FGD gypsum from Ningbo Beilun Power Plant of China and fly ash were used as the raw materials with which a complex cementing material was made. Effect of the related factors such as paste material, water proportion, mineral admixtures (Cement, CaO) and chemical activators (NaOH, CaCl₂, Na₂SiO₃, K₂SO₄) on characteristics of FGD gypsum-fly ash complex cementing material (noted as FGD-GFCM) is studied through a large number of single factor experiments. The additives with significant effect were chosen and the optimal mix proportion was determined. The experimental results show that an appropriate amount of admixtures can effectively improve the strength of the FGD gypsum–fly ash complex cementing material presented here. It is concluded that the strength of FGD-GFCB for 28d is best as the ratio of gypsum and fly ash is between 2:3 and 1:1 and water aggregate proportion is inversely proportional to the cementing material strength and apparent density of it.

Abstract: Foam concrete is used in building energy-saving insulation works, to study its fire performance is very important for further enhancing the fire performance of buildings. Under simulated fire conditions, by determining the compressive strength of foam concrete at different densities, different calcination time and different water content, this experiment studies the effect of these conditions on the fire performance of foam concrete. The results show that in case of fire, the compressive strength loss rate of foam concrete increases with the decreasing of density; to calcine the foam concrete standard specimens whose density are 300kg/m³ and 800kg/m³, their strength loss rates are 66.3% and 25.5%, the compressive strength of foam concrete in the same density increases with the calcination time decreasing, water content has different effects on different densities of foam concrete in the fire security. The foam concrete is non-flammable, but its compressive strength decreases due to the fire of combustible materials and high-temperature calcination.

Abstract: The flow ability, mechanical properties and microstructure of concrete with different strength grades affected by nano-SiO₂ and nano-CaCO₃ was studied. The experiment results showed that the strength of concrete at early age was increased by adding the nano-materials if the strength grade of concrete was not high. But the strength at the age of 28 days was not affected a lot by adding these nano-materials. On the other hand, it was not useful to the strength if the strength grade of concrete was high.