Cracks in cement concrete composites, whether autogenous or loading-initiated, are almost inevitable and often difficult to detect and repair, posing a threat to safety and durability of concrete infrastructures, especially for those with strict sealing requirements. The sustainable development of infrastructures calls for the birth of self-healing concrete composites, which has the built-in ability to autonomously repair narrow cracks. This paper reviews the fabrication, characterization, mechanisms and performances of autogenous and autonomous healing concretes. Autogenous healing materials such as mineral admixtures, fibers, nanofillers and curing agents, as well as autonomous healing methods such as electrodeposition, shape memory alloys, capsules, vascular and microbial technologies, have been proven to be effective to partially or even fully repair small cracks. As a result, the mechanical properties and durability of concrete infrastructure can be restored to some extent. However, autonomous healing techniques have shown a better performance in healing cracks than most of autogenous healing methods that are limited to healing of cracks having a width narrower than 150 μm. Self-healing concrete with biomimetic features, such as self-healing concrete based on shape memory alloys, capsules, vascular networks or bacteria, is a frontier subject in the field of material science. Self-healing technology provides concrete infrastructures with the ability to adapt and respond to the environment, exhibiting a great potential to facilitate the creation of a wide variety of resilient materials and infrastructures.

Self-healing cement concrete composites for resilient infrastructures: A review

Properties of bacterial rice husk ash concrete

The beneficial effect of microbially induced carbonate precipitation on building materials has been gradually disclosed in the last decade. After the first applications of on historical stones, promising results were obtained with the respect of improved durability. An extensive study then followed on the application of this environmentally friendly and compatible material on a currently widely used construction material, concrete. This review is focused on the discussion of the impact of the two main applications, bacterial surface treatment and bacteria based crack repair, on concrete durability. Special attention was paid to the choice of suitable bacteria and the metabolic pathway aiming at their functionality in concrete environment. Interactions between bacterial cells and cementitious matrix were also elaborated. Furthermore, recommendations to improve the effectiveness of bacterial treatment are provided. Limitations of current studies, updated applications and future application perspectives are shortly outlined.

Application of microorganisms in concrete: a promising sustainable strategy to improve concrete durability

Bacterial self-healing is an innovative technology allowing repairing open micro-cracks in concrete by CaCO3 precipitation. This bio-technology improves the durability of the structure. In this paper, peptone, yeast extract and Bacillus Subtilis were added as microbial adjuvant in concrete mix design. This led to a decrease in porosity resulting in an increase of strength, dynamic modulus as well as a reduction of water uptake, gas permeability and chloride permeation. Scanning electron microscopy, energy dispersive spectroscopy and raman spectroscopy showed that the microbial precipitations in the crack were CaCO3. Moreover, the morphology of calcite crystals was a needle-like, bouquet-like and rhombohedral-shaped. At 44 days, 400 μm crack surface width was completely filled. Hence, peptone, yeast extract and Bacillus Subtilis could be considered as a promising concrete admixture in enhancing durability and mechanical properties of concrete. Furthermore it is established that Eurocode 2 could be applied with confidence for predicting properties of bacterial concrete.

Bacterial self-healing of concrete and durability assessment

Effects of bacterial remediation on compressive strength, water absorption, and chloride permeability of lightweight aggregate concrete

Isolation and identification of bacteria to improve the strength of concrete.

Infilled frame construction represents a common type of construction in urban areas. The frames carry gravity loads and earthquake loads while the infills provide a building envelope and or internal partitioning. In several moderate earthquakes, buildings with infills have shown excellent performance even though many such buildings were not designed and detailed for earthquake forces. It is seen that the masonry infills contribute significant lateral stiffness, strength, overall ductility and energy dissipation capacity during moderate earthquakes. By providing fibres in the critical zones, it is possible to improve the performance of the frames against lateral loading. Hence, an attempt is made by using hybrid fibres (a combination of Polyolefin and Steel fibres) in the joints of the frames in various proportions and to determine the behaviour of the hybrid fibre-reinforced concrete (HFRC) frames under lateral reversed load. The percentages of fibres used are 0, 0.75, 1.5 and 2%. This research work presents the experimental results of RC frames and HFRC frames and also the comparison of the same using ANSYS.

D. L. Venkatesh Babu

Papers

Isolation and identification of bacteria to improve the strength of concrete.

Behaviour of Hybrid Fibre-Reinforced Concrete Frames with Infills Against Lateral Reversed Loads