Analysis of cementitious matrices self-healing with <i>bacillus</i> bacteria

Muller, Vinicius; Pacheco, Fernanda; Carvalho, Caroline Macedo; Fernandes, Franciele; Valiati, Victor Hugo; Modolo, Regina Celia Espinosa; Ehrenbring, Hinoel Zamis; Tutikian, Bernardo Fonseca

doi:10.1590/S1983-41952022000400004

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ORIGINAL ARTICLE • Rev. IBRACON Estrut. Mater. 15 (4) • 2022 • https://doi.org/10.1590/S1983-41952022000400004 copy

Analysis of cementitious matrices self-healing with bacillus bacteria

Análise de matrizes cimentícias autocicatrizantes com bactéria Bacillus

Authorship SCIMAGO INSTITUTIONS RANKINGS

Abstract

Bacterial solutions have been studied to promote self-healing of cementitious matrices, however, the concentration of this solutions varied between studies. Consequently, the objective of this study was to evaluate the self-healing potential of different concentrations of Bacillus subtilis AP91 encapsulated in expanded perlite (EP). Visual examination and capillary absorption of water was measured over time. Test samples were also subjected to strength resistance tests. The physiochemical properties of EP and his distribution on the matrix was evaluated. There was no observable trend in the effect of solution concentration on the width of crack healed. However, concentration affected the quantity and length of the fissures healed. Capillary absorption decreased as fissures were healed while no significant changes were measured in strength resistance regardless of the concentration. Results indicated that EP provided suitable encapsulation to the bacterial solution and there is an adequate distribution of the capsules in the cementitious matrix.

Keywords:
bacteria; concrete; durability; cracking; mortar; self-healing

Sample	Cement, kg	Sand, kg	EP, kg	B. subtilis AP91 concentration, UFC/ml	Water/cement ratio
BAC.6	1	0.7	0.084	$3$ x $10^{6}$	0.37
BAC.7	1	0.7	0.084	$3$ x $10^{7}$	0.37
BAC.8	1	0.7	0.084	$3$ x $10^{8}$	0.37

Aggregate		Apparent Density kg/m³	Density kg/m³	Maximum characteristic dimension, mm	Fineness modulus
Sand		1,734.33	2,700	3.26	3.01
EP	Natural	94.36	-	4.75	4.14
EP	Treated	475.50	-	4.75	4.14

SiO₂		Al₂O₃		Fe₂O₃		TiO₂		CaO		MgO
Min	Max	Min	Max	Min	Max	Min	Max	Min	Max	Min	Max
71	78	8.5	15	0.3	1.2	0.01	0.01	0.3	1.2	0.1	0.3
Na₂O		K₂O		SO₃		P₂O₅		MnO		Loss of Ignition
Min	Max	Min	Max	Min	Max	Min	Max	Min	Max	Min	Max
2.5	4.2	3.00	7.00	0.01	0.01	0.01	0.03	0.01	0.04	0.10	2.00

Sample	Fissure	Maximum healed width, mm	Type of healing
BAC.6	1	0.15	Spotted
	2	0.22	Spotted
	3	0.46	Spotted
BAC.7	4	0.07	Partially continuous
	5	0.22	Spotted
	6	0.22	Spotted
	7	0.00	Starting healing on the walls
BAC.8	8	0.19	Partially continuous
	9	0.20	Continuous
	10	0.11	Spotted
	11	0.11	Spotted^* * There was no total closure of the fissure width. The reported value is the difference between the initial and final widths.

Element	EP with calcium lactate, %		EP without bacterial solution or coating, %
Element	Weight	Atomic	Weight	Atomic
O	41.91	57.85	43.05	57.65
Na	1.96	1.88	2.27	2.12
Al	5.79	4.74	7.18	5.70
Si	33.41	26.27	40.70	31.04
K	8.57	4.84	4.76	2.61
Ca	7.09	3.91	0.62	0.33
Fe	1.26	0.50	1.41	0.54
Total	100.00		100.00

IBRACON - Instituto Brasileiro do Concreto Instituto Brasileiro do Concreto (IBRACON), Av. Queiroz Filho, nº 1700 sala 407/408 Torre D, Villa Lobos Office Park, CEP 05319-000, São Paulo, SP - Brasil, Tel. (55 11) 3735-0202, Fax: (55 11) 3733-2190 - São Paulo - SP - Brazil
E-mail: arlene@ibracon.org.br

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[1] Corresponding author: Regina Célia Espinosa Modolo. E-mail: reginaem@unisinos.br