Investigating the Effect of the Filamentous Fungus Trichoderma Reesei on the Strength of Cracked Concrete

Small cracks in concrete form due to a variety of reasons. These non-structural cracks can be amplified, however, by freeze-thaw forces, turning what were once small, harmless cracks into a safety concern. The use of a filamentous fungus, Trichoderma reesei (T. reesei), was explored in the self-healing of concrete cracks and its effect on concrete's strength. Concrete samples with model cracks of varying widths between 1mm and 2.5mm were created by placing triangular polyvinyl alcohol (PVA) wedges in the concrete mold and pouring concrete around the wedges. Potato dextrose agar (PDA) growth medium and a fourteen-day culture of T. reesei fungus were inoculated into the cracks of 14-day old concrete samples, which were then incubated for 14 days. The compressive strength of the concrete samples was measured after this 28-day period. These measures of strength were compared with the measures of strength for control groups, which were concrete samples lacking a crack, fungal inoculation, or both. Based on the data collected and the Mann Whitney U statistical tests performed, it was found that the median compressive strength of cracked concrete samples inoculated with T. reesei were statistically higher than the median compressive strength of cracked concrete samples that were not inoculated with T. reesei for all of the crack widths between 1mm and 2mm except for the 2.5mm crack width. This supports the hypothesis and demonstrates how the inoculation of T. reesei fungus is particularly effective for increasing the strength of cracked concrete with smaller crack widths, especially in the range of 1 – 2mm.