Applied Mechanics and Materials Vols. 584-586

Abstract: The influence of recycled aggregates on the frost resistance of concrete was studied by rapid freezing-thawing test. Results showed that there was an important effect of aggregate gradation on frost resistance of recycled coarse aggregate concrete. Frost resistance of recycled fine aggregate concrete was deteriorated with increasing the content of recycled fine aggregate, and recycled fine aggregate had a greater influence on the frost resistance of recycled aggregate concrete than recycled coarse aggregate when adding both together. Test showed that the mass loss rate and the relative dynamic elastic modulus loss are not consistent as evaluation indexes of the frost resistance for recycled concrete, and whether the mass loss rate is suitable as an indicator of frost resistance durability needs to be further studied.

Abstract: The particle types and resin content influence on properties of bamboo particleboard were studied in this paer. The purpose was to find a better manufacturing technology of bamboo particleboard for preparing bambooceramics. The results showed: bamboo particleboard manufacturing using precise shaving bamboo particles were more suitable for preparing bambooceramics than rough shaving bamboo particles; resin content had considerably influence on properties of bamboo particleboard, its mechanical properties can greatly improve with increasing the resin content of bamboo particles.

Abstract: The early hydration of alkali-activator slag(AAS) cementing material is studied by changing the environment temperature, the proportion of slag and fly ash, water glass module, and dosage of sodium silicate. The results show that as the temperature raise, the hydration rate and hydration heat of the AAS cementing materials will remarkably accelerate. Joining coal ash in the pure slag cementing material can effectively slowdown its hydration reaction, and the hydration heat is also reduced.

Abstract: In this paper, through the test to determine the blast furnace slag lightweight aggregate, cement as cementitious material, with various additives for the performance adjustment material, high strength lightweight material made of best fit of porous concrete material ratio, studied influence of raw materials on the performance of each group and production technology of its building load-bearing products .

Abstract: Polyvinyl alcohol fiber reinforced cement-based composites are a new kind of material based on micro mechanics design. It is produced by adding polyvinyl alcohol fiber in the cement-based composites. In efforts to study the mechanical properties of polyvinyl alcohol fiber reinforced cement-based composites, some specimens were tested to examine performances. According to experimental investigation on mechanical properties, the stress-strain relationship curves and failure patterns are obtained. The test indicates that polyvinyl alcohol fiber reinforced cement-based composites have better toughness and fracture energy, and it has superior physical mechanical performance.

Abstract: Silica fume is a by-product in the production of ferrosilicon and industrial silicon material. With the ultrafine physical structure of and high volcanic ash activity, silica fume is more important admixture in concrete improving the strength and durability of concrete, and it is widely used in high performance concrete engineering. Influence of silica fume on mechanical property of high performance concrete is investigated in this paper. Experimental results show that the strength of concrete increases significantly when suitable dosages of admixtures is applied.

Abstract: Foam concrete has the potential to be one of the most development prospect thermal insulation materials because of green environmental, fire resistance, low cost, energy conservation and other advantages. Its defect is low strength, poor durability, especially for the low dry density. Different density level brick powder foam concrete performance was studied. The experimental results show that: as the design dry density increases, the 28 d compressive strength is increasing; bibulous rate is gradually reduced; carbonation coefficient is above 90%; the strength loss after freezing and thawing is less than 20%;when the design dry density is greater than 500 kg/m³, mass loss rate is increasing which is close to the internal bubble state; when the dry density is 500 kg/m³, the thermal conductivity coefficient of brick powder foam concrete is 0.106 w/(m • k).

Abstract: High dropping non vibration concrete is widely used in high-rise steel tube concrete construction. In this paper, a high dropping non vibration self-compacting concrete with high mobility, low slump loss, and good anti-segregation ability is developed by mixing addition of PCA superplasticizer and SCC composite expansive admixture. The test results showed that the admixture and cement used in the test possess sound compatibility. The slump flow of self-compacting concrete prepared are more than 660mm, T₅₀₀ of 2.8~7.5s, 1h slump flow loss of less than 10%, and the segregation rate of less than 7.5%. Through strictly control production and dropping construction, supplemented by field ultrasonic detection measures, the high dropping self-compacting concrete in steel tube achieved successful application for a high-rise building.

Abstract: A novel super hard coating system of (Ti,Cr,Al)N was synthesized by multi arc ion plating technology. The Metallic ratio of Cr, Ti, and Al was varied by adjusting the currents of different TiAl target. The CrTiAlN composite coatings with different chemical composition were deposited on the surface of 65Mn steels by multi-ion plating technology in a gas mixture of Ar+N2. The coatings were characterized by means of energy dispersive X-ray(EDX) analysis, X-ray diffractmetry(XRD), scanning electronic microscopy(SEM), microhardness tester respectively. The experimental results show that the deposition velocity of CrTiAlN coatings reached maximum value, about 72nm/min. And the surface morphology of CrAlTiN films are compact and dense. The main composition of CrTiAlN composite films is Cr、Ti、Al、N, with the mass percent of Cr 29.61%,Ti 21.42%,Al 14.88%,N 34.10%. And the cross-section morphology appears as fibrous columnar crystals structure. Compared with CrN coatings, the preferential growth orientation of CrAlTiN films was changed from CrN (111) to CrN (200) after the addition of Ti, Al element. When the TiAl target arc current was 50A, the hardness reached the maximum value, 35GPa.

Abstract: Laser cladding has received significant attention in recent years due to its unique features and capabilities in various industries involved in metallic coating, high-value components repair, prototyping, and low-volume manufacturing. The laser cladding technology research status was reviewed. The characteristics of laser cladding technology, process methods, materials systems and current problems were summarized. The prospects and future research priorities were forecasted.