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.
