Crack Healing In Concrete Using Various Bio Influenced Self-Healing Techniques

Abstract

Concrete is most widely used engineering material in construction industry due to its strength, durability and low cost as compared to other construction materials. However, crack formation and progression under tensile stress is a major weakness of concrete. These cracks can make concrete vulnerable to deleterious environment due to ingress of harmful compounds, hence compromising its durability resulting in deterioration of concrete. For a durable and good structural concrete control over microcracks development and propagation of these cracks is necessary and crack healing can be helpful in mitigation of development and propagation of cracks in concrete. Self-healing concrete involves the crack repairing in concrete by use of compounds, bacteria and resins, added in concrete during the mixing stage. Bio concrete or bio influenced self-healing concrete is a product which has the ability to fill the cracks by producing chemical products from intentionally incorporated micro-organism in the concrete. In this kind of concrete micro-organisms along with a precursor compound are introduced in the concrete during mixing phase. When cracks are produced, water seeps in the cracks and activates the already present dormant micro-organisms. These micro-organisms later produce minerals to fill the cracks hence inhibiting strength loss and increasing durability of concrete. An experimental program was conducted to study the self-healing mechanism in concrete under various conditions. Bacteria were introduced in concrete by different techniques such as directly incorporating in mix, by immobilizing it in light weight aggregate and in combination with graphite nano platelets. In all the techniques, calcium lactate was used as an organic precursor and replaced 5% of cement. Specimens were made for each mix to compare the change in compressive strength of each mix. In addition to that, concrete specimens were also subjected to pre cracking at 3,7,14 and 28 days to determine the crack healing efficiency of each mix. Results show that bacteria immobilized in graphite nano platelets were more effective in samples pre cracked at 3 and 7 days while bacteria immobilized in light weight aggregates were more efficient in samples pre cracked on 14 and 28 days. In addition, results of compressive strength depict that self-healing concrete made with light weight aggregate incorporating immobilized bacteria had significant enhancement in compressive strength of concrete.