Single bacteria spore encapsulation through layer-by-layer self-assembly of poly(dimethyldiallyl ammonium chloride) and silica nanoparticles for self-healing concrete

Self-healing of cracks improves durability and reduces maintenance of concrete. Microbial induced calcite precipitation is a novel approach to engage self-healing in concrete, and bacteria spores are protected from direct contact with the surrounding cement matrix to maintain their viability. This study proposes a novel single bacteria spore capsule via layer-by-layer (LbL) self-assembly of poly(dimethyldiallyl ammonium chloride) and silica nanoparticles to enhance the consistency of healing as well as to minimize the negative impact on the mechanical properties of the resulting concrete. The resulting single bacteria spore capsule has a size of 1 μm and the inclusion of the capsules dose not compromise the compressive strength of the matrix. Cement paste incorporating the capsules shows complete closure of large crack of few hundred microns and complete recovery of transport property. Healing products are observed along the entire crack from the surface to the interior

Packing density of ternary cementitious particles based on wet packing method

The particle packing of cementitious materials is of essential importance to the performance of paste which constitutes the most uncertain part of mortar/concrete. Such importance is arising from the fact that the design of cementitious particle system inevitably involves the packing design, particularly for the emerging materials of 3D printable concrete and ultra-high performance concrete (UHPC). So far, scientific understanding of the particle packing in these emerging materials remains inadequate. In this regard, wet packing method (WPM) was used to measure the wet packing density (WPD) of ternary particle systems consisting of cement, pulverized fuel ash (PFA) and micro-silica (MS). The optimum ternary particle system in terms of WPD was determined. Comparison between the experimental results and Andreasen and Andersen (A&A) model revealed the limitations of A&A model. The design approach based on WPD contour shall advance particle packing-oriented cement and concrete science towards sustainable concrete design

Solid‐state Li–air batteries: Fundamentals, challenges, and strategies

Abstract The landmark Net Zero Emissions by 2050 Scenario requires the revolution of today's energy system for realizing nonenergy‐related global economy. Advanced batteries with high energy density and safety are expected to realize the shift of end‐use sectors toward renewable and clean sources of electricity. Present Li‐ion technologies have dominated the modern energy market but face with looming challenges of limited theoretical specific capacity and high cost. Li–air(O2) battery, characterized by energy‐rich redox chemistry of Li stripping/plating and oxygen conversion, emerges as a promising “beyond Li‐ion” strategy. In view of the superior stability and inherent safety, a solid‐state Li–air battery is regarded as a more practical choice compared to the liquid‐state counterpart. However, there remain many challenges that retard the development of solid‐state Li–air batteries. In this review, we provide an in‐depth understanding of fundamental science from both thermodynamics and kinetics of solid‐state Li–air batteries and give a comprehensive assessment of the main challenges. The discussion of effective strategies along with authoritative demonstrations for achieving high‐performance solid‐state Li–air batteries is presented, including the improvement of cathode kinetics and durability, solid electrolyte design, Li anode optimization and protection, as well as interfacial engineering

Single bacteria spore encapsulation through layer-by-layer self-assembly of poly(dimethyldiallyl ammonium chloride) and silica nanoparticles for self-healing concrete

Self-healing of cracks improves durability and reduces maintenance of concrete. Microbial induced calcite precipitation is a novel approach to engage self-healing in concrete, and bacteria spores are protected from direct contact with the surrounding cement matrix to maintain their viability. This study proposes a novel single bacteria spore capsule via layer-by-layer (LbL) self-assembly of poly(dimethyldiallyl ammonium chloride) and silica nanoparticles to enhance the consistency of healing as well as to minimize the negative impact on the mechanical properties of the resulting concrete. The resulting single bacteria spore capsule has a size of 1 μm and the inclusion of the capsules dose not compromise the compressive strength of the matrix. Cement paste incorporating the capsules shows complete closure of large crack of few hundred microns and complete recovery of transport property. Healing products are observed along the entire crack from the surface to the interior.<br/

Investigation and Improvement of Bond Performance of Synthetic Macro-Fibres in Concrete

Strength and stiffness are the key parameters characterising the bond performance of fibres in concrete. However, a straightforward procedure for estimating the bond parameters of a synthetic macro-fibre does not exist. This study employs pull-out tests to investigate the bond behaviour of synthetic macro-fibres. Two types of macro-fibres available in the market were investigated. A gripping system was developed to protect the fibres from local damage. The experimental campaign consisted of two stages. At the first stage, 32 concrete specimens were manufactured for performing 96 pull-out tests (three fibre samples were embedded in each cube perpendicular to the top surface and two sides). Two types of macro-fibres with either 10 or 20 mm embedment length were tested. The obtained load–displacement diagrams from pull-out tests demonstrate that the bond performance (characterised by the strength and deformation modulus) of the “top” fibres is almost 20% weaker than fibres positioned to the side surfaces. At the second stage, one type of macro-fibre was chosen for further experimentation of the feasibility of improving the bond performance through the use of colloidal silica or steel micro-fibres. This investigation stage employed an additional 36 concrete specimens. The use of steel micro-fibres was found to be an efficient alternative. The success of this solution requires a suitable proportioning of the concrete.This article belongs to the Special Issue Advanced Composites: From Materials Characterization to Structural Application (Second Volume)This project has received funding from the European Regional Development Fund (Project No. 01.2.2-LMT-K-718-03-0010) under grant agreement with the Research Council of Lithuania (LMTLT). The APC was funded by Vilnius Tech

Genomic Analysis of Bacillus megaterium NCT-2 Reveals Its Genetic Basis for the Bioremediation of Secondary Salinization Soil

Bacillus megaterium NCT-2 is a nitrate-uptake bacterial, which shows high bioremediation capacity in secondary salinization soil, including nitrate-reducing capacity, phosphate solubilization, and salinity adaptation. To gain insights into the bioremediation capacity at the genetic level, the complete genome sequence was obtained by using a multiplatform strategy involving HiSeq and PacBio sequencing. The NCT-2 genome consists of a circular chromosome of 5.19 Mbp and ten indigenous plasmids, totaling 5.88 Mbp with an average GC content of 37.87%. The chromosome encodes 5,606 genes, 142 tRNAs, and 53 rRNAs. Genes involved in the features of the bioremediation in secondary salinization soil and plant growth promotion were identified in the genome, such as nitrogen metabolism, phosphate uptake, the synthesis of organic acids and phosphatase for phosphate-solubilizing ability, and Trp-dependent IAA synthetic system. Furthermore, strain NCT-2 has great ability of adaption to environments due to the genes involved in cation transporters, osmotic stress, and oxidative stress. This study sheds light on understanding the molecular basis of using B. megaterium NCT-2 in bioremediation of the secondary salinization soils