Advanced Materials Research Vols. 335-336

Abstract: The fiber material generally has higher tensile strength and toughness, which make up for the lack of tensile strength of concrete and the defects of drying shrinkage easily. Fiber reinforced shotcrete has many engineering advantages such as the crack resistance, impermeability, corrosion resistance (except for steel fiber addition), anti-fatigue performance, wear resistance, impact resistance, toughness and so on. In the construction of tunnels and other underground tunnel, the fiber shotcrete has been more widely used. Fiber materials currently include steel fibers and polypropylene fibers, each with its advantages and adaptability. The mechanism and characteristics of fiber reinforced shotcrete are described to provide an important basis for design and construction of sprayed concrete for underground engineering.

Abstract: Two groups of buildings residues was studied in the paper as to unconfined compressive strength, soaked unconfined compressive strength, shrinkage values, porosity. It is show that Q2 soil stabilizer can improve the micro-structure of solidified blocks of buildings sediment for dispersed sphere-shaped particles can be generated by Q2 soil stabilizer mixed with buildings residues and cement. As a result, the solidified block of buildings sediments was improved in the properties in its increased unconfined compressive strength, decreased shrinkage values and higher durability.

Abstract: C25 self-compacting concrete which meets the requirement of workability and strength grade is maked up by selecting local raw materials, using reasonable compound admixtures, based on c25 self-compacting concrete preliminary mixing proportion. we try to pursue an economical mixing ratio of the Low-strength Self-compacting Concrete which can adapt to the characteristics of the region's raw materials. The purpose is to promote the application of self-compacting concrete in region.

Abstract: Rapid carbonation test and gas permeability radio method are used to study the durability of lightweight aggregate concrete. The concrete includes foam,lightweight aggregate，pre-wetting and air entraining. The test results show that The combined-effect of air entraining agent(AEA)and aggregate pre-wetting can increase permeability. The anti-carbonation capacity of pre-wetting and air entraining lightweight aggregate concrete is 40% greater than that of ordinary concrete.gas permeability radio of pre-wetting and air entraining lightweight aggregate concrete is half of that foam concrete and expanded pearlite concrete.

Abstract: The influence of mineral admixtures on chloride threshold value was investigated by EIS method, MIP test and TG test, respectively. The experimental results showed that the chloride threshold value decreased with increasing the fly ash and slag content in composite cementitious. The increasing of fly ash and slag replacement resulted in the decreasing of porosity, average pore size and Ca(OH)₂ content. The effect of mineral admixtures on the chloride threshold value was the comprehensive results of concrete pore structure and Ca(OH)₂ content. The chloride threshold value decreased with decreasing the Ca(OH)₂ content in concrete, and there was an approximate linear relationship between the logarithm of chloride threshold value and the logarithm of CCa(OH)₂ content when the specimens exposed in tidal zone. The specimen exposed in tidal zone has a higher chloride threshold value than that exposed in splash zone was due to the lower dissolved oxygen around steels in concrete.

Abstract: Formaldehyde (HCHO) which emitted from building materials, such as plywood and adhesive, is a carcinogenic substance in indoor air. Chitosan is produced from the structural element in the exoskeleton of crustaceans (such as crabs and shrimp), and has the ability to absorb HCHO. In this study, the HCHO removal efficiency by chitosan additives was evaluated for two building materials - adhesive and plywood. The experiments were performed in a small chamber based on the method of Japanese Industrial Standards (JIS) A1901 to evaluate the HCHO emission from adhesive and plywood before and after the application of chitosan additives. Both the HCHO concentration in the chamber and the HCHO emission factor of two adhesives, urea-formaldehyde (UF) resin and Poly Vinyl Acetate (PVAC) resin, were reduced from 0.02~0.21 ppm and 0.12~1.05 mg/m2h to 0~0.14 ppm and 0.12~0.63 mg/m2h after using chitosan additives. The best HCHO removal efficiency was adding 9% chitosan additives in the adhesives. The amount of absorbed HCHO is proportional to the amount of chitosan additives, and approximate 0.02 mg of HCHO can be absorbed by per mg of chitosan additive (i.e. absorption capacity 0.02 g HCHO/g Chitosan).

Abstract: The method recommended by ACI Committee 544 was used in this paper. Drop hammer impact tests based on mortar specimens with different contents of polypropylene fiber were carried out. The compressive strength test is done before and after impacting. Under different drop hammer impact time, polypropylene fiber mortar specimens’ damage degree was evaluate based on compressive strength. The results show that the hammering number corresponding to the impact fracture of polypropylene fiber mortar is more than ordinary mortar that without fiber. The axial compressive strength of all specimens decreased gradually during the process of hammering, but adding the right amount of polypropylene fibers can effectively slow down the rate of strength reduction.

Abstract: Fire-resistance performance experiments with static loading-fire are investigated about one carbon fiber sheet（CFS） shear strengthened and one without CFS strengthened reinforced concrete (RC) beams exposed to the ISO834 standard fire. Shear strengthened RC beams are wrapped with fire insulation material- thick painted fire retardant coatings. Relationship between measure points temperature, displacement and time are achieved. The results suggest that: the ratio of shear-span is the main factor to fire-resistance rating and failure modes of CFS shear strengthened RC beams in fire; shear-failure fire-resistance rating are increased by thickening fire insulation to shear strengthened RC beams; mid-span deflection of shear failure is approximate one half of bending failure when shear strengthened RC beams.

Abstract: Water transport is an important parameter that affects the long term performance and degradation of concrete greatly. Nowadays, adding fly ash is a promising solution to achieve high-performance, low-price and environment-friendly concrete. To characterize the effect of fly ash on water transport of concrete, especially in dry state, moisture variations and microstructure of concrete with different mix proportions were studied in this paper. Test results reveal that fly ash will increase the porosity of early curing concrete, the higher porosity leads to a faster evaporation, which accelerates the transport of water in cement based materials.

Abstract: Coupled steel bars have already more than 30 year historical development. But, it was made by HPB235, Plasticity and ductility were very poor, so, only use in planking component. Now, we made coupled steel bars by Low-alloy steels. According to tentative data, model building formula that’s rigidity and crack Opening. Provide the basis for the project construction.