Biomimetic Self-Healing Cementitious Construction Materials for Smart Buildings

Retrofitting of concrete for rigid pavement using bacterial: A meta-analysis

Cracking in tension causes damage to regular concrete. When the surface of the concrete cracks, liquids can enter and damage the structure. Remediating concrete in rigid pavements is time-consuming, costly, and challenging. Concrete cracking can be reduced using sustainable solutions, such as concrete bacteria. Using concrete bacteria is an innovative method for continuously retrofitting concrete, improving its durability, and reducing maintenance costs. Several studies have explored the possibilities of a wide range of bacteria and demonstrated concrete retrofitting. However, in these extensive studies of sustainable solutions, the role of concrete bacteria in retrofitting concrete for rigid pavement has not been clarified. This meta-analysis aims to compare and contrast the performance of various microorganisms in concrete restoration, considering the bacteria concentration, total concrete components, and water/cement ratio. Data from 371 articles were entered into the initial database and 37 articles into the final database for meta-analysis. Low concentrations (10 CFU/mL) of Bacillus subtilis increased the compressive strength after 28 days at 46.8 MPa, and the optimum concentration of Bacillus subtilis was 105 CFU/mL, resulting in an optimum compressive strength of 58.2 MPa after 28 days, an optimum water/cement ratio of 0.3, and the optimum total ingredients (cement, fine and coarse aggregates) ranging from 2000 to 2400 kg/m3. This meta-analysis study supports a new approach to selecting concrete bacteria and developing sustainable advances in concrete technology.

A forgotten element of the blue economy: marine biomimetics and inspiration from the deep sea

The morphology, physiology, and behavior of marine organisms have been a valuable source of inspiration for solving conceptual and design problems. Here, we introduce this rich and rapidly expanding field of marine biomimetics, and identify it as a poorly articulated and often overlooked element of the ocean economy associated with substantial monetary benefits. We showcase innovations across seven broad categories of marine biomimetic design (adhesion, antifouling, armor, buoyancy, movement, sensory, stealth), and use this framing as context for a closer consideration of the increasingly frequent focus on deep-sea life as an inspiration for biomimetic design. We contend that marine biomimetics is not only a "forgotten" sector of the ocean economy, but has the potential to drive appreciation of nonmonetary values, conservation, and stewardship, making it well-aligned with notions of a sustainable blue economy. We note, however, that the highest ambitions for a blue economy are that it not only drives sustainability, but also greater equity and inclusivity, and conclude by articulating challenges and considerations for bringing marine biomimetics onto this trajectory.

Smart Bio-Agents-Activated Sustainable Self-Healing Cementitious Materials: An All-Inclusive Overview on Progress, Benefits and Challenges

Cementitious materials deteriorate progressively with the formation of cracks that occur due to diverse physical, chemical, thermal, and biological processes. Numerous strategies have been adopted to obtain cement-based self-healing materials and determine the novel self-healing mechanisms. The uses of microbes have been established to improve the thickness of the healed crack and mechanical properties of the concrete, a phenomenon seldom addressed in the literature. Based on these factors, this article comprehensively appraises the smart bio-agents-based autonomous healing performance of concrete to demonstrate the recent progress, expected benefits, and ongoing challenges. The fundamentals, design strategies, and efficacy of the smart bio-agents-activated self-healing cementitious materials are the recurring themes of this overview. Furthermore, the effects of various processing parameters on the performance of cementitious self-healing smart bio-agents are discussed in-depth. The achievements, knowledge gaps, and needs for future research in this ever-evolving area for the sustainability and resilience of the built environment are highlighted.

Enhancement of the Mechanical, Self-Healing and Pollutant Adsorption Properties of Mortar Reinforced with Empty Fruit Bunches and Shell Chars of Oil Palm

This study aims to produce mortar through the addition of oil palm shells (OPS)-activated charcoal and oil palm empty fruit bunch (OPEFB) hydrochar, which has high mechanical properties, self-healing crack capabilities, and pollutant adsorption abilities. The cracking of mortar and other cementitious materials is essential in anticipating and reducing building damages and ages due to various reasons, such as chemical reactions, foundation movements, climatic changes, and environmental stresses. This leads to the creation of self-healing mortar, which is produced by adding reductive crack size materials to form calcium carbonate (CaCO₃) and silicate hydrate (3CaO.2SiO₂.2H₂O, CSH). One of these materials is known as activated charcoal, which is obtained from oil palm shells (OPS) and oil palm empty fruit bunches (OPEFB) fibres. This is because the OPS-activated charcoal minimizes crack sizes and functions as a gaseous pollutant absorber. In this study, activated charcoal was used as fine aggregate to substitute a part of the utilized sand. This indicated that the utilized content varied between 1–3 wt.% cement. Also, the mortar samples were tested after 28 days of cure, including the mechanical properties and gaseous pollutant adsorption abilities. Based on this study, the crack recovery test was also performed at specific forces and wet/dry cycles, respectively, indicating that the mortar with the addition of 3% activated charcoal showed the best characteristics. Using 3% of the cement weight, OPEFB hydrochar subsequently varied at 1, 2, and 3% of the mortar volume, respectively. Therefore, the mortar with 3 and 1% of OPS-activated charcoal and OPEFB hydrochar had the best properties, based on mechanical, self-healing, and pollutant adsorption abilities.

Potential Applications of 5G Network Technology for Climate Change Control: A Scoping Review of Singapore

Climate change is one of the most challenging problems that humanity has ever faced. With the rapid development in technology, a key feature of 5G networks is the increased level of connectivity between everyday objects, facilitated by faster internet speeds with smart facilities indicative of the forthcoming 5G-driven revolution in Internet of Things (IoT). This study revisited the benefits of 5G network technologies to enhance the efficiency of the smart city and minimize climate change impacts in Singapore, thus creating a clean environment for healthy living. Results revealed that the smart management of energy, wastes, water resources, agricultures, risk factors, and the economy adopted in Singapore can remarkably contribute to reducing climate change, thus attaining the sustainability goals. Hence, future studies on cost-effective design and implementation are essential to increase the focus on the smart city concept globally.

Ureolytic MICP-Based Self-Healing Mortar under Artificial Seawater Incubation

Ureolytic microbial-induced calcium carbonate precipitation (MICP) is a promising green technique for addressing sustainable building concerns by promoting self-healing mortar development. This paper deals with bacteria-based self-healing mortar under artificial seawater incubation for the sake of fast crack sealing with sufficient calcium resource supply. The ureolytic MICP mechanism was explored by morphology characterization and compositional analysis. With polyvinyl alcohol fiber reinforcement, self-healing mortar beams were produced and bent to generate 0.4 mm width cracks at the bottom. The crack-sealing capacity was evaluated at an age of 7 days, 14 days, and 28 days, suggesting a 1-week and 2-week healing time for 7-day- and 14-day-old samples. However, the 28-day-old ones failed to heal the cracks completely. The precipitation crystals filling the crack gap were identified as mainly vaterite with cell imprints. Moreover, fiber surface was found to be adhered by bacterial precipitates indicating fiber–matrix interfacial bond repair.

Performance of Epoxy Resin Polymer as Self-Healing Cementitious Materials Agent in Mortar

This research investigated the application of epoxy resin polymer as a self-healing strategy for improving the mechanical and durability properties of cement-based mortar. The epoxy resin was added to the concrete mix at various levels (5, 10, 15, and 20% of cement weight), and the effectiveness of healing was evaluated by microstructural analysis, compressive strength, and non-destructive (ultrasonic pulse velocity) tests. Dry and wet-dry conditions were considered for curing, and for generating artificial cracks, specimens at different curing ages (1 and 6 months) were subjected to compressive testing (50 and 80% of specimen’s ultimate compressive strength). The results indicated that the mechanical properties in the specimen prepared by 10% epoxy resin and cured under wet-dry conditions was higher compared to other specimens. The degree of damage and healing efficiency index of this particular mix design were significantly affected by the healing duration and cracking age. An optimized artificial neural network (ANN) combined with a firefly algorithm was developed to estimate these indexes over the self-healing process. Overall, it was concluded that the epoxy resin polymer has high potential as a mechanical properties self-healing agent in cement-based mortar.