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Purpose The purpose of this paper is to investigate the effect of an admixture, Swine-waste Bio-char (SB), on the water absorption characteristics of cement pastes. Design/methodology/approach The effect of SB percentages, heat treatment temperatures, water/binder ratios, and age on the water absorption percentages (WAPs) of SB modified cement pastes were investigated using scanning electron microscopy-energy dispersive spectra, FTIR, Brunauer-Emmett-Teller, and laboratory experiments. Findings The WAPs of cement pastes with SBs produced at the low treatment temperature (LTT) of 340°C and 400°C were significantly lower (p<0.01) than pastes with SBs produced at the high treatment temperature (HTT) of 600°C and 800°C. This was attributed primarily to the more dominant presence of hydrophobic alkyl surface groups from non-volatilized matter in LTT-SBs. This had also resulted in lower surface areas and pore volumes in LTT-SBs. As a result of the volatilization of these labile hydrophobic groups at HTT, HTT-SBs were more hydrophilic and had higher surface areas and pore volumes. Consequently, HTT-SB pastes had higher WAPs and no significant differences (p<0.05) existed between HTT-SB pastes and control pastes. Also, low water/binder ratios and aging reduced water absorption of SB modified cement pastes. Practical implications LTT-SBs reduce water absorption and could reduce concrete deterioration; and as such, associated building repair, maintenance, and adaptation costs. Notably, reductions in concrete water absorption will extend the service life of concrete buildings and infrastructures, particularly in unfavorable environmental conditions. The observed benefits are tempered by the current lack of information on the effects of SB on compression strength, workability, and other durability properties. Social implications SB utilization in concrete buildings will enhance swine-waste disposal and reduce negative environmental impacts on swine farming communities; consequently, improving their quality of life. Originality/value Current bio-char research is focused on plant-derived bio-char toward soil remediation and contaminant removal, with very limited applications in concrete. This research advances knowledge for developing livestock-derived bio-char, as a PCRM, toward more sustainable and durable concrete structures.

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Transition metal oxides can introduce high pseudocapacitance to an electric double layer capacitor for storing more electrical charges. Their role can be more than that since they possess high dielectric constant. Here, we propose a self-sustainable bi-functional configuration by eliminating traditional separator of a metal oxide film supercapacitor that is capable of providing good energy storage performance. We take advantage of super-aligned electrospun carbon nanofibers (SA-ECNFs) as an interconnected scaffold, coupling with electrochemical deposition of α-MnO2 layers at different currents to introduce pseudocapacitance while providing dielectric layer functioning as a separator to assemble a state-of-the-art supercapacitor. The good electrochemical performance of galvanic charge-discharge specific capacitance at 141 F g −1 and energy density at 12.5 Wh kg −1 offers the promising applications in the energy storage field.

Summary In recent years, carbon nanofibrous materials from electrospinning polyacrylonitrile (PAN) have been developed for freestanding electrode materials. However, there is still a large room to improve the electrochemical performance of this type of electrode material for supercapacitor purposes. In this research, an attempt is made to enhance the electrochemical performance of electrospun carbon nanofibrous material (ECNF) as an electrode for supercapacitor application by incorporating chlorella, a single‐celled green freshwater microalga that grows naturally worldwide, in combination with carbon activation. The chlorella was mixed with PAN up to an equal amount in spinning solution and electrospun to nanofibrous material followed by carbonization and further activation. The investigation of electrochemical performance of chlorella‐derived carbon nanofibrous electrode materials before and after activation (C‐ECNF and C‐ECNFa) indicated that chlorella is a superior natural resource as nitrogen (N) and phosphorus (P) dopant as well as mesopore promoter to develop practical high‐performance carbon nanofibrous electrode material for supercapacitor application.