The effect of Bacillus bacteria and nano clay on the properties of roller pavement concrete and self-healing of its cracks due to calcium carbonate deposition

Abstract

ABSTRACT One of the best methods to enhance the strength and durability of concrete and repair the cracks is to use a self-healing mechanism, based on bacterial-induced calcite precipitation. In this study the effect of this mechanism was investigated on untreated roller concrete pavement containing nanoclay. The bacteria used in this study was Bacillus sphaericus. The specimens were characterized using permeability, compressive strength, tensile strength, and ultrasonic tests. At first, one face of the specimens was subjected to bacterial self-healing to permeability test and all faces to compressive and tensile strength test. Also, using a copper sheet, a standard crack was created on one side of the specimens, and then the repair rate of these cracks due to bacterial self-repair was investigated by ultrasonic testing. The results showed that permeability, compressive and tensile strengths improved by 2.2%, 7.1% and 14.4%, respectively in the treated specimens without nanoclay. Meanwhile, in concrete specimens containing nanoclay, the improvement rate increased. Also, the results of the ultrasonic test showed that repair occurs by this coating and its rate is 12% in nanoclay-treated specimens and 7% in treated specimens without nanoclay, which shows the positive effect of nanoclay in improving the bacterial repair of standard cracks.