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Concrete is one of the most used materials. It is resistant and cheap, but its use assumes a great problem: with time it deteriorates and cracks appear which can become very dangerous. To repair these damages is expensive.

The durability of concrete is compromised by the ingress of harmful chemicals such as saline water, CO2 and acid rain into cracks created during early age shrinkage and/or mechanical loading. The current practice is to overdesign the structure in order to achieve a maximum crack width between 0.1 and 0.4mm under long term serviceability loading[1].

A commonly used solution is to make use of pre-stress by pre or post-tensioning. These pre-stressed structures are designed to be uncracked during serviceability loading. The major problem with the pre-stressed system is that steel tendons are relatively expensive and require expensive anchors and jacking operations, which themselves also pose a health and safety issue[2].

The man-made self healing ability of concrete, known as autonomic healing was first introduced by Dry in 1994[3].

The system proposed by Dry was similar to that used in polymers in which a healing agent is encapsulated inside a microcapsule and when a crack forms it breaks the microcapsule, releasing the healing agent and healing the crack.

Research scientist Dr, Henk Jonkers from Delft University of Technology in Holland has invented a biological concrete that can seal its own cracks, preventing water ingress and corrosion of reinforcement.

The new concrete would be perfect for structures which are difficult to maintain, like underground buildings, motorways or oil rigs.

The principle of material self healing was developed in analogy to self-healing capacity of living (biological) tissues and materials and thus represents an example of bio-mimicry[4].

BioConcrete, is produced by adding a two-component biochemical self-healing agent to the concrete mixture.

Specially selected types of the bacteria genus Bacillus, along with a calcium-based nutrient known as calcium lactate, and nitrogen and phosphorus, are added to the ingredients of the concrete when it is being mixed.

The introduction of such material will extend the lifespan of buildings and reduce repair costs

By having self-healing agents in a concrete mix, it will drastically reduce the amount of CO2 emissions that result from concrete production, which includes mining, transportation and those that come from concrete plans.

Source: New Civil Engineer, Newcastle University, Polytechnic University of Catalonia, US Infrastructure, Ingenia – Issue 46, March 2011 and Global Talent News

(this article written for 1BINA.my)

[1] Eurocode 2: Design of concrete structures – Part 1-1: General rules and rules for buildings. EN1992-1-1. 2004.

[2] Dunn, S., Self Healing Concrete – A Sustainable Future, Cardiff University

[3] Dry, C M. 1994, Smart Materials and Structures, 3(2), pp. 118-123.

[4] Jonkers, Henk M., BioConcrete – A Novel Bio-based Material, Department of Materials and Environment, Faculty of Civil Engineering and Geosciences, Delft University of Technology