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The volume of sludge is a growing problem worldwide due to the increase in the population and the growing in industry and agriculture. Therefore, sludge management and disposal are becoming problematic and required more intensive and creative efforts. The objective of this study was to produce activated carbon using sewage sludge as raw material. Preparation conditions of sewage sludge based activated carbon were optimized by applying Box-Behnken Design (BBD) in response surface methodology (RSM). Optimization process investigated the impact of interaction between chemical activation ratio, contact time and activation temperature on the surface area of activated carbon. A series of activated carbons were chemically activated using potassium hydroxide (KOH) and physically activated by pyrolysis process in tube furnace. The response of optimization process was the surface area of activated carbon which was depicted by the second-order polynomial regression model created by ANOVA. Optimum activated carbon characterizations were conducted by surface area (BET), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM) and Thermogravimetric analysis TGA. The maximum surface area of 377.7 m2/g was achieved at chemical activation ratio of 1, activation contact time of 3 hours and activation temperature of 500 ℃. According statistical analysis, the most significant parameter was the contact time, followed by chemical activation ratio and activation temperature.

The concrete-filled double skin steel tube (CFDST) is a more viable option compared to a concrete-filled steel tube (CFST) due to consisting a hollow section, while degradation is enhanced simply by using carbon fiber-reinforced polymer (CFRP). Hence, the stabilization of a concrete&rsquo, s ductile strength needs high- performance fiber-reinforced cementitious conmposite. This study investigates the behavior of high-performance fiber-reinforced cementitious composite-filled double-skin steel tube (HPCFDST) beams strengthened longitudinally with various layers, lengths, and configurtion of CFRP sheets. The findings showed that, with increased CFRP layers, the moment capacity and flexural stiffness values of the retrofitted HPCFDST beams have significantly improved. For an instant, the moment capacity of HPCFDST beams improved by approximately 28.5% and 32.6% when they were wrapped partially along 100% with two and three layers, respectively, compared to the control beam. Moreover, the moment capacity of the HPCFDST beam using two partial layers of CFRP along 75% of its sufficient length was closed to the findings of the beam with two full CFRP layers. For energy absorption, the results showed a vast disparity. Only the two layers with a 100% full length and partial wrapping showed increasing performance over the control. Furthermore, the typical failure mode of HPCFDST beams was observed to be local buckling at the top surface near the point of loading and CFRP rapture at the bottom of effect length.

In recent years, application of precast post-tensioned (PT) segmental columns consisting of a number of precast segments and footing foundation aligned and connected altogether by post tensioning strands, has shown increasing focus in seismic regions due to their advantages over traditional columns including self-centering capability with low residual displacement and permanent deformation under severe lateral seismic loading. Recently, there have been an emerge of interest to use ultra-high strength concrete (UHSC) due to their great tensile and compressive strengths. In this study, a three dimensional (3D) nonlinear finite element model for PT segmental columns are developed and the results are validated with the experimental test conducted. A parametric study is carried out to investigate the influence of UHCS with different compressive strengths of 126 MPa, 150 MPa and 193 MPa; and tensile strengths of 6.0, 8.9 and 12.3 MPa on lateral response of PT segmental columns. In this study, PT segmental columns with normal strength; High strength concrete fully replaced with normal strength concrete throughout the columns; and UHSC as jacketing around the first segment are investigated. The influence of compressive strength and tensile strength on stiffness, lateral load capacity and ductility of the segmental columns with different concrete strengths are discussed. Also, strengthening of PT segmental columns with UHSC jacketing were examined and the results are compared.