Biochar-mortar composite: manufacturing, evaluation of physical properties and economic viability

Singapore generates about half a million ton of wood waste annually, which constitutes a major fraction of disposed waste. Pyrolysis of wood waste to produce biochar, which can be used as additive in cement mortar, is a viable alternative to increase recycling rate of woody residues. This study explores the influence of biochar, prepared from mixed wood saw dust, on strength, elastic modulus, drying shrinkage and permeability of cement mortar. Biochar prepared by pyrolysis at 300 oC (BC 300) and 500 oC (BC 500) was added to mortar at 1–8% by weight of cement. Results show that addition of 1–2 wt% BC 300 and BC 500 improve early age (7-day) compressive strength of mortar, which is related to high water retention of 7.50 g/g and 8.78 g/g by dry BC 300 and BC500 respectively. However, addition of biochar did not significantly influence flexural strength, drying shrinkage and modulus of elasticity. Mortar with 1% addition of BC 300 and BC 500 showed about 58% and 66% reduction in water absorption and depth of water penetration respectively compared to control. Based on the experimental findings, it is concluded that 1–2 wt% addition of biochar may be recommended to improve strength and reduce permeability of cement mortar. Added at these proportions, we showed that the price of biochar mortar is still reasonably close to that of conventional mortar. Therefore, this study suggests that biochar from wood waste has the potential to be deployed as carbon sequestering admixture to improve performance of cementitious mortar at a price that is likely to be acceptable to the building industry

Robustness of Prefabricated Prefinished Volumetric Construction (PPVC) High-rise Building

[EN] Due to the safety awareness arisen from natural and human-caused disasters, robustness design of building is increasingly important to ensure the stability of the building and to prevent progressive collapse. For this reason, the robustness design of innovative construction technologies such as modular construction may be essential due to its relative novel structural form and numerous joints among modules. Particularly in Singapore, Prefabricated Prefinished Volumetric Construction (PPVC) has been highly promoted in residential and commercial buildings, hostels and hospitals to boost the construction productivity and quality as well as to reduce the reliance on foreign workforce. PPVC offers high quality and efficiency because most of the finishes and mechanical and electrical services are manufactured and installed together with the modules in factory, before sending for on-site assembly. To maximize the productivity of PPVC, modular design standardization and repetition can be improved by going for high-rise. Nonetheless, there are limited studies on the robustness of PPVC high-rise building and its behavior under progressive collapse remains uncertain. Therefore, this paper investigates the robustness of steel PPVC high-rise building under column removal scenarios by conducting non-linear numerical analysis. The effects of joint design and diaphragm action between modules are studied to ensure continuity of horizontal and vertical tying. This paper provides insight on the behaviour and alternative path for load transfer under column removal scenario for future design guideline of robustness PPVC building.The authors would like to acknowledge the financial support by the National Research Foundation (NRF) and SembCorp-NUS Corp Lab under project grant R-261-513-009-281Chua, YS.; Liew, JYR.; Pang, SD. (2018). Robustness of Prefabricated Prefinished Volumetric Construction (PPVC) High-rise Building. En Proceedings of the 12th International Conference on Advances in Steel-Concrete Composite Structures. ASCCS 2018. Editorial Universitat Politècnica de València. 913-919. https://doi.org/10.4995/ASCCS2018.2018.6955OCS91391

Robust estimation of bacterial cell count from optical density

Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals <1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data

Enhancement of barrier properties of cement mortar with graphene nanoplatelet

10.1016/j.cemconres.2015.05.007Cement and Concrete Research7610-1

Axial load resistance of grouted sleeve connection for modular construction

10.1016/j.tws.2020.106883Thin-Walled Structures154TWAS

Experimental Study of Grouted Sleeve Connections under Bending for Steel Modular Buildings

24311261

Steel Concrete Composite Systems for Modular Construction of High-rise Buildings

10.1016/j.istruc.2019.02.010Structures21135-14