Comprehensive selection of the wood properties of Paulownia clones grown in the hilly region of southern China

The wood properties of Paulownia clones determine their ultimate price and uses. This study selected superior clones with good color and mechanical properties using selection indexes. Variation in 23 5-year-old Paulownia clones was analyzed using genetic parameters, correlation analysis, and a comprehensive assessment of two color characteristics [color difference (ΔE) and whiteness (WH)] and six mechanical properties [density (ρ), hardness of the tangential, radial, and end surfaces (Ht, Hr, and He), and cleavage strength of the tangential and radial surfaces (qt, qr)]. There were significant differences (p < 0.01) in each of the eight traits among the 23 clones. There were significant negative phenotypic and genetic correlations between ΔE and WH. The six mechanical properties were significantly positively correlated genetically, showing significant positive phenotypic correlations with each other, except for ρ, Ht, and qt. With a selection rate of 8.70%, clones MB04 and L01 were selected as superior using the comprehensive selection index. Compared with the control (9501), the genetic gains of clones MB04 and L01 in ΔE, WH, ρ, qr, qt, He, Hr, and Ht were 0.40, 0.21, 10.32, 12.57, 14.81, 26.05, 28.04, and 6.84%, respectively, and the actual gains were 0.59, 0.31, 17.21, 28.45, 28.09, 34.90, 40.08, and 11.12%.

Laboratory Study of Engineering Properties of Flowable Backfill Material

Aimed at the common problems of small backfill space, hard to backfill, difficult to guarantee compaction quality in engineering, development law of fluidity and mechanical properties (unconfined compressive strength and cleavage strength) is analyzed by changing mix ratio of cement, fly ash and water. Fluidity is mainly controlled by water content. Range of fluidity is significantly different when water content is around 60％.Considering the effect of economy and strength, 4% cement content will be recommended.

Effect of Fly Ash Content on Mechanical Properties of Cement-Fly Ash Stabilized Crushed Stones

To improve the impact of fly ash on the properties of cement-fly ash stabilized crushed stone, and promote it popularize and apply better. This paper investigated the effect of fly ash content on unconfined compressive strength, cleavage strength and resilient modulus of cement-fly ash stabilized crushed stones, and those relationships between mechanical parameters. The results showed that with increasing of the fly ash content, the unconfined compressive strength and cleavage strength increased at first, then decreased, the resilient modulus decreased, and The brittleness index increased. We can conclude that the optimal fly ash content is between 10% and 15%, and increment of fly ash content can improve its crack-resistance.

Research on the Mix Design of Cement Asphalt Concrete

Effect of material mix proportion on strength of cement asphalt concrete (CAC) was studied based on 7d cleavage strength. Results indicate that the cleavage strength of CAC increase sharply with the increase of the cement content (0-6%), and the optimum content of added water and emulsified asphalt were 2% and 6% respectively while the cement content was 5%.

Effect of Fast Freeze-Thaw Cycles on Mechanical Properties of Ordinary-Air-Entrained Concrete

Freezing-thawing resistance is a very significant characteristic for concrete in severe environment (such as cold region with the lowest temperature below 0°C). In this study, ordinary-air-entrained (O-A-E) concrete was produced in a laboratory environment; the compressive strength, cubic compressive strength of C50, C40, C30, C25, and C20 ordinary-air-entrained concrete, tensile strength, and cleavage strength of C30 ordinary-air-entrained concrete were measured after fast freeze-thaw cycles. The effects of fast freeze-thaw cycles on the mechanical properties (compressive strength and cleavage strength) of ordinary-air-entrained concrete materials are investigated on the basis of the experimental results. And the concise mathematical formula between mechanical behavior and number of fast freeze-thaw cycles was established. The experiment results can be used as a reference in design, maintenance, and life prediction of ordinary-air-entrained concrete structure (such as dam, offshore platform, etc.) in cold regions.

Performance of Nanomodified Asphalt Binder and Mixture

The nanopowdered VP108 was selected and applied into the base asphalt binder and mixture. The Marshall binder and mixture tests were conducted to evaluate the mechanical and pavement performance of base and VP108 modified asphalt binders and mixtures. The test results present that the penetration, softening point, penetration index and ductility of VP108 modified asphalt binder improved compared to the base asphalt binder. The mixture test results display that the compression strength, water susceptibility, resilient modulus and cleavage strength of VP108 modified asphalt mixture enhance compared to the base asphalt mixture. Therefore, the overall performance of VP108 modified asphalt binder and mixture improves compared to the base asphalt binder and mixture, such as the high temperature performance, resilient modulus and water resistance property.