Microbial Induced Calcium Carbonate Precipitation (MICCP) for road construction

Abstract

The growing concern over climate change has led the drive for the development of alternative building materials in several industries, including road construction. Bio-based construction, using Microbial Induced Calcium Carbonate Precipitation (MICCP) has been investigated in recent years as a potential cost-effective and environmentally friendly alternative engineering approach. The Council for Scientific and Industrial Research (CSIR) developed a research program looking at MICCP. Several barriers to using MICCP in road construction was found, a potential biohazard using exotic bacteria and the current technique used for treatment. In this paper, in situ cultivation of indigenous urease positive bacteria was investigated and compared to a CSIR designed biological prototype. The objective of this paper is to present the results of Unconfined Compressive Strength (UCS) tests performed on a marginal G5 (COLTO, 1985) material treated with the prototype and in situ cultivated bacteria. The work showed that it was possible to cultivate urease positive bacteria present within the G5 material. It was found that the cementation solution could act as a stimulation and cementation media when the pH is reduced to give the bacteria time to cultivate and buffer the pH upward for Calcium Carbonate Precipitation to take place. Lastly, the CSIR prototype performed better in terms of UCS and treatment technique. The treatment consists of only one application of the prototype, which is more consistent with current road construction practice, as compared with the multiple application needed for in situ cultivation.