REHABLITATION OF DAMAGED CONCRETE USING ECO-FRIENDLY BACILLUS SUSPENDED GROUT

Abstract

Construction pattern in Pakistan throughout the decades has expanded suddenly which calls for expanded construction to meet the demands of ever-growing population. Construction sector is one of the significant contributors of CO2 emissions that has led to world facing green-house gases, global warming, and health issues. Since concrete is a popular construction material principally due to its strength, it has the tendency to develop micro structural cracks because of low tensile strength, that gradually deteriorates its properties owing to embedded reinforcement exposed to chloride ions that leads to corrosion. Various commercially available techniques are currently a potential remedy to this problem. Numerous researches have been conducted to investigate the performance of these commercial techniques and it has been concluded that these are expensive and have failed to provide a long-term solution. A bacillus suspended grout can be a solution to rehabilitate concrete. Various researches have been conducted to investigate self-healing concrete and bio-influenced self-healing has been concluded to be the best approach in terms of crack healing and strength recovery. Same technique can be used to prepare a grout that ensures long term crack repair, whose performance will depend on using an effective micro/nano immobilizer. In this research study, 5 different formulations were made using nano/micro zeolite and Super Absorbent Polymer (SAP) as immobilizer and were used to examine crack repairing at various ages, quantifying CO2 sequestration ability, investigating the corrosion potential and analyzing autonomous healing at various cracking cycle. Optical Microscopy, X-ray Diffraction (XRD), Thermogravimetric Analysis (TGA), Strength Recovery Index (SRI) and Ultrasonic Pulse Velocity (UPV) were conducted to verify crack repair. CO2 sequestration ability was quantified by developing a climate control chamber and modelling a room. Corrosion was examined through Weight Loss Measurement. Visual evidence was obtained to analyze autonomous healing at various cracking cycles. Experimental results reveal that zeolite and SAP both are an effective carrier to immobilize bacteria, but the Bacterial Zeolite (BZ) grout gave the optimum results by recovering compressive and tensile strength up to 96.73% and 92.51% respectively, CO2 sequestration ability of bacterial zeolite grout is 32 times that of non-bacterial grout, corrosion potential was found to be only 1.13% loss in rebar weight and maximum autonomous healing was reported to be 3.3 mm for the second cracking cycle.