Self healing in concrete materials
Concrete is one of the most important construction materials, used to make buildings, bridges, roads and other structures. Thus it is important to maintain the strength and durability of the concrete over time and in harsh environmental conditions. In an effort to increase concrete lifetime we have developed a concrete material which shows self healing characteristics. This system involves an aqueous sodium silicate solution enclosed within a polyurethane microcapsule. These microcapsules are then incorporated into the concrete samples, cured and tested. When a stress causes a crack in the concrete, if the crack breaks open a capsule it releases the sodium silicate inside the capsule, this sodium silicate reacts with the calcium hydroxide of the concrete and forms a calcium-silica-hydrate gel, which seals the crack and does not allow the crack to propagate within the sample, thus healing the crack. ^ Samples have been stressed to a point of maximum failure in a three point bend system and then retested again after a week and the healing efficiency calculated. Healing efficiency is compared by testing samples containing different loadings of capsules and samples with varying capsule diameters. The efficiency increases as the volume of capsules increase and also when smaller capsules are present in the specimen. Compressive tests and dynamic tests do not show varied results with capsules, proving capsules do not have any adverse effect on the samples. Finally experiments showed that presence of the C-S-H gel hinder the rate of water that gets absorbed in concrete. The increased strength helps it to become a better construction material.^
Chemistry, Polymer|Engineering, Mechanical
"Self healing in concrete materials"
Dissertations and Master's Theses (Campus Access).