Abstract
Microbially induced calcite precipitation can cement sand and is an environment-friendly alternative to ordinary Portland cement. In this study, clean Ottawa sand was microbially treated to induce calcite contents (CCs) of 0%, 2%, and 4%. Polyvinyl alcohol fiber was also mixed with the sand at four different contents (0%, 0.2%, 0.4%, and 0.6%) with a constant CC of 4%. A series of undrained triaxial tests was conducted on the treated sands to evaluate the effects of the calcite treatment and fiber inclusion. Their hydraulic conductivity was also determined using a constant head test. As the CC increased from 0% to 4%, the friction angle and cohesion increased from 35.3° to 39.6° and from 0 to 93 kPa, respectively. For specimens with a CC of 4%, as the fiber content increased from 0% to 0.6%, the friction angle and cohesion increased from 39.6° to 42.8° and from 93 to 139 kPa, respectively. The hydraulic conductivity of clean Ottawa sand decreased by a factor of more than 100 as the CC increased from 0% to 4%. The fiber inclusion had less effect on the hydraulic conductivity of the specimen with 4% CC.
Highlights
Induced calcite precipitation (MICP) has received considerable attention in recent years because it has the potential to replace ordinary Portland cement in geotechnical stabilization practices
For specimens with a calcite contents (CCs) of 4%, as the fiber content increased from 0% to 0.6%, the friction angle and cohesion increased from 39.6◦ to 42.8◦ and from 93 to 139 kPa, respectively
The hydraulic conductivity of clean Ottawa sand decreased by a factor of more than 100 as the CC increased from 0% to 4%
Summary
Induced calcite precipitation (MICP) has received considerable attention in recent years because it has the potential to replace ordinary Portland cement in geotechnical stabilization practices. MICP processing with ureolytic bacteria is a process based on the use of enzyme ureases and complementary chemicals (typically urea and calcium chloride). This is illustrated by the following reactions [1]: Reaction 1: CO(NH2 )2 + 2H2 O → 2NH4 + + CO3 2−. Reaction 3: Ca2+ + CO3 2− → CaCO3. The engineering properties of MICP biocementation have been investigated on multiple levels. Several investigations [6,7,8] have confirmed that
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