No abstract

No abstract

Concrete is a human-made construction material which is assembled by cement, coarse aggregate, fine aggregate and water. Concrete is susceptible to cracking, as small cracks have no effect but large cracks cause disintegration of concrete structures. These cracks will allow chemicals and gases to enter disturbing the lifespan of structures. Reconstruction and maintenance of concrete structures are most difficult and expensive because of labour cost, energy and cost required to produce cement are high. Self healing materials are used to heal the cracks of concrete structures. These materials are eco-friendly can heal the cracks by producing precipitated crystals like calcium carbonate. The inner portion of cracks can also be sealed by these self healing materials. The main aim of this paper is to represent the mechanisms of various materials, i.e. biological agent, chemical agent, supplementary cementitious materials, crystalline admixtures and super absorbent polymers used for self healing are detailed. The way of application of self healing material to concrete is briefed. Through this study the rate of self healing, mechanical properties and durability properties of concrete are computed. The micro structural behaviour of hydrated products is analyzed.

No abstract

Conventional concrete is prone to cracking under tensile load, despite its good compressive strength. Recently, biological agents have been applied to heal the cracks in concrete, making concrete structures more serviceable. This paper mainly attempts to evaluate the mechanical properties of bacteria-based self-healing concrete. Two bacteria were selected as the bioagents in concrete, namely, Bacillus subtilis and Bacillus halodurans. The concentration of the bioagents were set to 10 5~1 0 7 cell/mL in water. Then, the two bacteria were applied to cracked concrete to cure the cracks. After curing for several days, the bacteria-based self-healing concrete was subjected to compressive and flexural tests to estimate its mechanical parameters. The results show that the self-healing concretes cured for 14d and 28d had a 7% and 18% higher compressive strength than conventional concrete, respectively; the self-healing concretes cured for 14d and 28d had a 11% and 28% higher flexural strength than the conventional concrete, respectively. Thus, the bioagents could effectively heal the surface cracks on concrete, and make the concrete imperviable.