Piezoresistive behaviour of alkali-activated aluminosilicate binder

Numerous studies have been conducted to prove the sensing application of self-sensing concrete, composite materials with conductive fillers incorporated into the matrix. Geopolymers are synthetic amorphous inorganic polymers which can offer comparable performance to cementitious materials, hypothetically exhibits the potential of self-sensing. The objective of the present study is to develop self-sensing geopolymer composite by proper tailoring of matrix, addition of fillers and modification of fiber-matrix interface respectively. The study enlightens the superior piezoresistive mechanism in geopolymer matrix through various experiments such as impedance analysis, hall effect measurements, and microstructural analysis. Additionally, the significance of current research resides in the strategic use of nanofillers. Better self-sensing performance was obtained by altering the fiber matrix interface and microstructure with nano fillers. The study establishes that the piezoresistive mechanism is determined by the material's mechanical, electrical, and structural properties. Following on from this newfound insight, it is possible to develop geopolymer composites with excellent self-sensing performance.Doctor of Philosoph

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)

A novel two-step method for screening shade tolerant mutant plants via dwarfism

When subjected to shade, plants undergo rapid shoot elongation, which often makes them more prone to disease and mechanical damage. Shade-tolerant plants can be difficult to breed; however, they offer a substantial benefit over other varieties in low-light areas. Although perennial ryegrass (Lolium perenne L.) is a popular species of turf grasses because of their good appearance and fast establishment, the plant normally does not perform well under shade conditions. It has been reported that, in turfgrass, induced dwarfism can enhance shade tolerance. Here we describe a two-step procedure for isolating shade tolerant mutants of perennial ryegrass by first screening for dominant dwarf mutants, and then screening dwarf plants for shade tolerance. The two-step screening process to isolate shade tolerant mutants can be done efficiently with limited space at early seedling stages, which enables quick and efficient isolation of shade tolerant mutants, and thus facilitates development of shade tolerant new cultivars of turfgrasses. Using the method, we isolated 136 dwarf mutants from 300,000 mutagenized seeds, with 65 being shade tolerant (0.022%). When screened directly for shade tolerance, we recovered only four mutants from a population of 150,000 (0.003%) mutagenized seeds. One shade tolerant mutant, shadow-1, was characterized in detail. In addition to dwarfism, shadow-1 and its sexual progeny displayed high degrees of tolerance to both natural and artificial shade. We showed that endogenous gibberellin (GA) content in shadow-1 was higher than wild-type controls, and shadow-1 was also partially GA insensitive. Our novel, simple and effective two-step screening method should be applicable to breeding shade tolerant cultivars of turfgrasses, ground covers, and other economically important crop plants that can be used under canopies of existing vegetation to increase productivity per unit area of land