Comparison of compressive and splitting tensile strength of autoclaved aerated concrete (AAC) containing water hyacinth and polypropylene fibre subjected to elevated temperatures

This paper described the results of an extensive experimental study on the comparative between compressive and splitting tensile behavior of autoclaved aerated concrete (AAC) containing water hyacinth fibre (WHF) with AAC mixed with polypropylene (PP) fibre. The specimens of AAC-WHF and the AAC-PP were subjected to elevated temperatures (100, 200, 400, 800 and 1000 °C). Test results indicated that an optimum water hyacinth and PP fibre dosage was at 0.5 and 0.75 % by volume respectively. The maximum residual in compressive strength and the splitting tensile strength of AAC-WHF and AAC-PP were 0.43 and 0.16 N/mm² and 0.51 and 0.18 N/mm² respectively. In addition, the loss in residual strength of AAC mixed PP fibre was slower than AAC mixed WHF. The splitting tensile strength of AACs was more sensitive to high temperatures than the compressive strength. A severe strength loss was observed for all of the AAC after exposure to 800 °C. Based on the test results, it can be concluded that the addition of PP fibers can significantly promote the residue mechanical properties of AAC during heating.     

Hydraulic Characteristics of Gabion-Stepped Weirs

Experimental studies on the hydraulics of flow through and over gabion-stepped weirs are presented. Two flow components were observed, i.e., base flow through the void between filled stones and overflow on the gabions. The energy loss ratios in the gabion-stepped weirs are greater than those in the corresponding horizontal stepped weirs by approximately 7, 10, and 14% for weir slopes of 30, 45, and 60°, respectively. As a result, the velocity at the outlet is lower. Stone size and shape have little influence on the energy loss and flow velocity as compared to the increasing effect of the weir slope. The pressure acting on the step face for the gabion-stepped weirs is less than that of the horizontal steps owing to the cushioning effect generated by filled stones. To reduce pressure on a step face at a fixed discharge for different weir slopes, the void ratio of the filled stones should be low to allow a small amount of base flow. The pressure distribution pattern on the horizontal face of a step is provided.     

Dyeing of cotton yarn with the aqueous extract of the leaves of Eupatorium odoratum L. in Thailand and associated extract toxicity studies

Flavonoid constituents from the aqueous extract of the leaves of Eupatorium odoratum, an invasive weed in Thailand, have potential use as dyestuffs for cotton dyeing. It was found that cotton yarn, which was pretreated with a chitosan solution (with and without a crosslinking glyoxal solution), followed by dyeing with E. odoratum extract in the presence of the inorganic mordant, alum, provided better depth of shade (K/S) and also gave better fastness to light and washing than the untreated cotton yarn. Pretreated cotton yarn with the biomordant solution from Memecylon scutellatum leaves gave relatively poor light and wash fastness of the resultant dyed cotton in the presence of alum. From the toxicity studies, the aqueous extract of the leaves of E. odoratum before and after dyeing showed a high toxicity level to the earthworm (Diplocardia communis) and the guppy fish (Poecilia reticulate). Therefore, it is strongly suggested that E. odoratum aqueous extract after dyeing should be significantly diluted before discharged into the environment.     

Firmness Properties of Mangoes

The purpose of this research was to determine the firmness of mango fruit at different stages of maturity. Immature, mature, and over mature fruit from two Thai mango cultivars (Nam Dokmai and Chok Anan) were subjected to two firmness measuring techniques: a slow compression technique using the Universal Testing Machine and a high-speed impact sensing technique using the low-mass impact tester. The firmness of a mango as determined by the compression test was expressed by the slope of the force-deformation graph, while firmness values derived from the impact test were defined by the ratio between maximum acceleration and the corresponding time (the firmness index). A very good correlation between the two indicators was obtained. Each firmness indicator of the two cultivars remained relatively unchanged from the immature through to the fully mature stage, although firmness rapidly decreased as the fruit ripened. The Chok Anan cultivar was firmer than the Nam Dokmai type throughout the development period. The impact method was able to determine mango firmness rapidly, accurately, and non-destructively.