Self-cleaning performance of nano-TiO₂ modified metakaolin-based geopolymers

Geopolymer is an alternative binder to Portland cement. In this paper, nano-TiO₂ was incorporated into a metakaolin-based geopolymer matrix to impart photocatalytic properties into the binder. The self-cleaning performance of the resulting binders was revealed under UV and direct sunlight irradiation. The effects of nano-TiO₂ inclusion on compressive strength, microstructure, solar reflectivity, wettability, and decomposition of Rhodamine B (RhB) of the resulting binder were reported. Results showed the compressive strength, total solar reflectance (TSR), and photoinduced hydrophilicity and contaminate decomposition of geopolymer increases with TiO2 dosage. TiO2 particles mainly act as fillers to densify the binder. The resulting TiO2 metakaolin geopolymer has a compressive strength of 61 MPa and a surface TSR of 72%. The addition of TiO₂ imparts photocatalysis properties into the geopolymer, which activates super-hydrophilicity of the surface and assist in the complete decomposition of RhB dye after direct sunlight exposure.Ministry of National Development (MND)The authors would like to thank the funding support for this project from Land and Livability National Innovation Challenge, Ministry of National Development, Singapore (L2NICCFP2-2015-4)

Efficient utilization of municipal solid waste incinerator bottom ash for autoclaved aerated concrete formulation

Contrary to the previous research on the general utilization of municipal solid waste (MSW) incineration bottom ash (IBA) in autoclaved aerated concrete (AAC), the given study strategically utilizes IBA for AAC formulation to improve IBA utilization efficiency and to enhance the hardened properties of the resulting IBA-AACs. A systematic classification and characterization approach was used to determine the suitable IBA fractions for each ingredient. The classified IBA with particle size less than 0.3 mm (IBA fines), IBA glass fraction (IBA-G), and coarse non-ferrous IBA with particle size greater than 1.18 mm (coarse IBA-ONF) were used as calcium, silica, and metallic aluminum (as an aerating agent) resource, respectively. The resulting IBA-AACs showed much higher specific strengths (about 40% enhancement) than the Control AAC due to the formation of relatively pure tobermorite gel. The leaching test results confirmed the safe utilization of AAC during and after the service life. The utilization of classified IBA optimized the amount of IBA that can be incorporated in AAC.National Environmental Agency (NEA)The authors would like to acknowledge financial support from the Environment Technology Research Program (ETRP), National Environment Agency (NEA), Singapore (ETRP 1301 104)