Achievement of Early Compressive Strength in Concrete Using Sporosarcina pasteurii Bacteria as an Admixture

Often it is observed, attainment of early compressive strength in concrete is a challenge. Researchers have tried various admixtures to achieve the objective. This work addresses the issue of achieving early compressive strength in concrete using a bacterium called Sporosarcina pasteurii. The bacterium is characterised with the ability to precipitate calcium carbonate in the presence of any carbonate source and is known for its resistive capacity in extreme temperature and pressure zones. To establish the objective of gain in early strength around 192 concrete cubes were tested at 3, 7, 14, and 28 days and the results compared with controlled concrete. The bacterium was used in combination of chemicals and the dosage proportions were altered to achieve the desired M20 compressive strength at 28 days. 1. Introduction The compressive strength achieved in concrete is one of the most important and desirable properties of concrete. Many admixtures have been tried by experts to achieve the desired compressive strength. This paper aims at achieving compressive strength in concrete; however, the authors of the paper have tried to use a nutrition medium containing a bacterium named Sporosarcina pasteurii as an admixture in concrete. The focus of the work has been to decrease the time taken by the cement to hydrate and achieve maximum strength at early ages. Early strength gain in normal concrete is mainly associated to the water/cement ratio. Mixes with low water cement ratio gain strength more rapidly than those with higher water cement ratio. This is because the cement grains are closer to one another and a continuous system of gel is established more rapidly. There are actually many different types of accelerators present in the market but the common problems posed by the accelerators are low slump, low initial setting time, and thus reduced workability. These adverse properties of accelerators refrain most of the experts from using the same in concrete. The use of blended cements presently has also been on rise in construction industry; blended cements with a defined amount of cement replaced with flyash are commonly being used. The addition of flyash to cement, however, has little disadvantage; that is, for flyash to hydrolyse and form into a strong component like cement it needs Ca(OH)2. The Ca(OH)2 is a biproduct of cement hydration process; hence for the flyash to form the C-S-H gel it requires calcium hydroxide in adequate quantity and this can occur only if adequate cement hydrolisation takes place. If calcium carbonate is present in cement, the