Crack filling in concrete by addition of Bacillus subtilis spores – Preliminary study

Abstract

This study aimed to analyze the performance of two concrete mixtures with the addition of B. subtilis spores regarding their capacity of filling cracks during the curing time, evaluating whether the addition can influence the compressive strength of the concrete. For so, six concrete mixtures were studied divided in two mix compositions: 1:1:2 and 1:2:3 (cement: sand: gravel) with w/c of 0.33 and 0.45, respectively. For each composition were added concentrations of 0, 0.3x10 8 or 1.2x10 8 of B. subtilis spores/mL. The results showed that all the samples with spores addition presented crystals precipitation, possibly calcium carbonate, that visually filled the cracks. However, more studies of microstructural analysis should be conducted to prove that the cracks were closed. The compressive strength presented satisfactory results, because the addition of 1.2x10 8 spores/mL did not present significant differences in compressive strength at probability level of 5%, when compared to the reference concrete.Keywords: bioconcrete; concrete with addition of spores; Bacillus subtilis; crack filling; cracks.Relleno de fisuras en concreto por la adición de esporas de Bacilos subtilis -Estudio preliminar ResumenEste estudio tiene como objetivo analizar el desempeño de dos composiciones de hormigón con adición de esporas de B. sutilis con relación a su capacidad de relleno de fisuras durante el periodo de cura, evaluando la influencia de la adición en la resistencia a compresión. Para ello han sido estudiadas seis composiciones de hormigón, divididas en dos dosificaciones: 1:1:2 y 1:2:3 (cemento: árido fino: grava) en peso, con relación a/c de 0,33 y 0,45. Para cada una de las mezclas se utilizaran concentraciones de 0, 0.3x10 8 or 1.2x10 8 de esporas de B. sutilis/mL. Los resultados obtenidos han demostrado que todas las muestras con adición de esporas presentaron precipitación de cristales, posiblemente carbonato de calcio, que fue visualizado en las fisuras. Más estudios microestructurales deberán ser realizados para comprobar que de hecho ocurrió el relleno de las fisuras. La resistencia a compresión presentó resultados satisfactorios, pues no hubo diferencias significativas en relación al hormigón de referencia, a nivel de 5% de probabilidad.Palabras clave: biohormigón; hormigón con adición de esporas; Bacilos subtilis; relleno de fisuras; fisuras.

Investigation in manufacturing self-healing cementitious materials using microbial technology

“…The selected microorganisms are in accordance with the standard conditions of Vietnam. In this study, the author used the most widely used and popular family of bacillus microorganisms to make self-healing cementitious material by microorganisms [21]. Through the study, the source of bacillus subtilis in water can be divided into 3 types as illustrated in Figure 3 [22].…”

“…For type 1 nurturing environments, several studies from around the world are summarized in the following tables [23], [24], [25], [26]: For type 2 nutrient medium, several mixtures are used: nutrient broth (beef broth + peptone + NaCl) [27], Mueller Hinton (MH) or Trypton Soy Broth broth. [28], yeast extract medium [29], or type 3 contains only calcium lactate C6H10CaO6 [22], [30]. Among these materials, calcium lactate C6H10CaO6 has the cheapest price and is easy to find in Vietnam market.…”

Self-healing mortar using different types, content, and concentrations of bacteria to repair cracks.

“…These findings support the hypothesis that there is a relation between the increase in bacterial concentration and the increase in compressive strength. This improvement was owing to bacteria producing more CaCO3 as a filler material for mortar pores and micro-cavities as a result of their biological activity [11,15].…”

“…The porosity and connectivity of the pores affect the permeability of the mortar [7,8]. The more open the pore structure of mortar is, the more exposed the material is to penetrating substances' degradation mechanisms [2,9] This fact has motivated researchers to search for ways to produce smart, sustainable, and environmentally friendly concrete materials [10][11][12]. Different repairing techniques are available to repair the cracks, but they're expensive and time-consuming operations.…”

Avaliação da influência da adição de nutrientes no processo de autocicatrização de fissuras em materiais a base de cimento a partir do emprego da bactéria Bacillus subtilis (AP 91)

“…O procedimento foi repetido duas vezes (n = 2). Em seguida, a solução salina contendo bactérias foi armazenada por dois dias à temperatura de 8 ºC para induzir a formação de esporos (Schwantes-Cezario et al, 2018). A quantificação dos esporos bacterianos cultivados em meio de cultura MH foi realizada com o auxílio do espectrofotômetro com leitura a 600 nm.…”