Strength and durability performance of modified cement-based concrete incorporated immobilized bacteria.

Owing to the load bearing and the other external environmental factors, the defects in the concrete occur in the form of cracks and flaws which leads to the reduction in the durability characteristics. Generally, the bacteria-based autogenous healing is adopted to restore those cracks. The ureolytic bacteria used urea as a source of nitrogen and convert it to carbonate ions, and then carbonate ions react with calcium ions to induce calcium carbonate in the presence of water. In the present study, binary cement-based concrete containing different concentration of immobilized bacteria is investigated, and its performance is evaluated based on the strength and durability characteristics. The experimentation includes bagasse ash (< 45µ) and fly ash (Class C) in proportions partially blended with cement. External loads are stimulated to assess the mechanical properties of concrete. Rapid chloride penetration test of the concrete before the induction of cracks is also performed. By comparing the compression test results, the microbial concrete of 105cells/mg shows greater compressive strength when compared with the microbial concrete of 107cells/mg and also with the conventional concrete. SEM analysis and compression test results reveal 15% fly ash additives have accomplished microbial concrete. And also the test results indicate the potential of encapsulation using clay pellets and silica gel.

Investigating the Efficacy of Adhesive Tape for Drilling Carbon Fibre Reinforced Polymers.

In the present research work, an effort has been made to explore the potential of using the adhesive tapes while drilling CFRPs. The input parameters, such as drill bit diameter, point angle, Scotch tape layers, spindle speed, and feed rate have been studied in response to thrust force, torque, circularity, diameter error, surface roughness, and delamination occurring during drilling. It has been found that the increase in point angle increased the delamination, while increase in Scotch tape layers reduced delamination. The surface roughness decreased with the increase in drill diameter and point angle, while it increased with the speed, feed rate, and tape layer. The best low roughness was obtained at 6 mm diameter, 130° point angle, 0.11 mm/rev feed rate, and 2250 rpm speed at three layers of Scotch tape. The circularity error initially increased with drill bit diameter and point angle, but then decreased sharply with further increase in the drill bit diameter. Further, the circularity error has non-linear behavior with the speed, feed rate, and tape layer. Low circularity error has been obtained at 4 mm diameter, 118° point angle, 0.1 mm/rev feed rate, and 2500 RPM speed at three layers of Scotch tape. The low diameter error has been obtained at 6 mm diameter, 130° point angle, 0.12 mm/rev feed rate, and 2500 rpm speed at three layer Scotch tape. From the optical micro-graphs of drilled holes, it has been found that the point angle is one of the most effective process parameters that significantly affects the delamination mechanism, followed by Scotch tape layers as compared to other parameters such as drill bit diameter, spindle speed, and feed rate.