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Split Hopkinson pressure bar (SHPB) technique is used to determine the dynamic strength of reactive powder concretes (RPCs) with different steel-fiber contents. Two types of pulse shapers with different thicknesses are considered to reduce the high-frequency-oscillation effect and achieve a nearly constant strain rate over a certain deformation range. It is known that the compressive strength of concrete-like materials is hydrostatic-stress-dependent, and the apparent dynamic strength enhancement comes from both the effects of the hydrostatic stress and strain rate. In order to differentiate them, numerical method is used to calculate the contribution of the hydrostatic stress, and then the genuine strain-rate effect on dynamic compressive strength of RPCs is determined. In addition, the effect of steel-fibers on dynamic strength and failure mode of RPCs is discussed.KEY WORDS reactive powder concrete, split Hopkinson pressure bar, hydrostatic-stress effect, strain rate

Distillation wastewater from a continuous ethanol fermentation process using the acid hydrolysate of wood biomass was fed into a methane fermentation reactor and treated anaerobically. The maximum TOC volumetric loading rate was only 1.0 g/l/d without aeration, but improved to 3.0 g/l/d with micro-aeration to suppress H2S buildup. By supplying air equivalent to 9.0 vol% of the evolved biogas into the top of the fixed-bed reactor, H2S concentration decreased to less than 50 ppmv (ml/m 3 ) and the efficiency of SO4 2-removal was more than 99.5%. The methane concentration in the biogas was maintained around 45% when micro-aeration was used. The effluent from the simultaneous methane fermentation and sulfur removal process was then subjected to biological denitrification-nitrification treatment by recirculating the effluent from the nitrification reactor. As a result, NH4 + -N was reduced to less than 5.0 mg/l without the addition of electron donors such as methanol.