Effects of Wood Ash on Properties of Concrete and Flowable Fill

This research investigated the use of wood ash to partially replace cement or sand in conventional concrete, roller compacted concrete (RCC), and flowable fill. The main focus was to determine how the wood ash addition affected the main fresh and hardened properties of these materials. It was found that the wood ash could be successfully incorporated into the conventional concrete. In particular, the wood ash addition not only accelerated the setting, but also improved the early and the 28-day compressive strength of concrete that contained the blast furnace slag. It was also observed that the wood ash could be positively added into RCC to facilitate the compaction and reduce the risk of segregation. In addition, the wood ash can be beneficially introduced into the flowable fill mixtures to facilitate flow, to alleviate bleeding and subsidence, as well as to achieve controlled strength especially when combined with the class C or the class F fly ash.

Determination of Fosthiazate Residue in Ginger by Gas Chromatography

[Objectives] An analytical method was established for determining fosthiazate residue in ginger by gas chromatography with flame photometric detector(GC-NPD) to evaluate the safety of fosthiazate in ginger. [Methods] The fosthiazate residue in ginger was extracted with dichloromethane, and subjected to sodium chloride salt-out and liquid-liquid extraction with hexane and dichloromethane(the plant and soil samples had no need for the later two steps). The analysis was performed on gas chromatograph equipped with a flame photometric detector(GC-FPD), and the fosthiazate residue was quantitatively determined by calculating the peak area. [Results] The results of degradation dynamics showed that the half-life of fosthiazate was 7.2-8.7 d in ginger plants, and was 9.9-19.8 d in the soil. The results of the final residue test showed that after applying the fosthiazate granules according to the recommended high dose(active component 58.2 g a.i/m^2,WK) and low dose(38.8 g a.i/m^2,WK) once, the final residual amounts of fosthiazate in the ginger and soil were estimated to be <0.02 mg/kg and <0.02-0.103 mg/kg, respectively, while no fosthiazate residue was detected in all control samples(<0.02 mg/kg). The maximum residue limit(MRL) of fosthiazate in ginger was not established in China, and was 0.2 mg/kg in Japan. [Conclusions] The method was proved to meet the basic requirements of pesticide residue analysis on sensitivity, accuracy and precision and have good linearity. It is recommended that when using fosthiazate granules to control root-knot nematode and root rot in ginger, it is applied at the highest dose of 38.8 g ai/m^2,WK once 30 d before ginger cultivation to treat the soil, and ginger is harvested in the ginger harvest period.