Bio-modification of sand or aggregates

• Main Author: Tan, Jia Yue
• Other Authors: Chu Jian
• Format: Final Year Project
• Language: English
• Published: 2017
• Subjects: DRNTU::Engineering::Civil engineering
• Online Access: http://hdl.handle.net/10356/71197
• Institution: Nanyang Technological University

Concrete is widely used in construction for supporting massive loads due to its characteristically high compressive strength. Many studies were conducted to find ways to further strengthen concrete. One such plausible way is the Microbially Induced Calcite Precipitation (MICP) method in which urease producing bacteria are used to induce the precipitation of calcium carbonate on aggregates. This method had been proven useful in healing cracks and consolidating soil in past researches. This project aims to investigate how the compressive strength of concrete made using aggregates treated with MICP will increase with varying concentration of calcite precipitate present in the aggregates. The early age compressive strength after 7 curing days and later age compressive strength after 28 curing days of the treated concrete were compared against that of the untreated ones. The concrete specimens also have different W/C ratio to compare the effectiveness of MICP on high-strength and low-strength concrete. The experimental results show that concrete made using MICP treated aggregates generally has higher compressive strength than the untreated ones. This can be explained by the fact that the calcite precipitates that adhered to the aggregates’ surface can provide greater interlocking bond between the cement and aggregates. The treated specimens were comparably less dense and more water absorbent than the untreated ones. The graphs of the percentage increase in compressive strength against CaCO3 concentration present in the treated specimens show different trend in strength increment for low-strength concrete and high-strength concrete.