Bacteria-based self-healing concrete : effect of bio-agents on the cementitious matrix

In this paper, the influence of the specific bacterial nutriënt (yeast extract) and the precitation precursors (urea and Ca-nitrate) on cement hydration and mechanical proper were first investigated. Meanwhile, the availability of the nutriënt after being mixed into cementitious matrix was examined. Due to the harsh conditions of concrete (high alkaline and small pore size), bacteria need to be immobilized beforehand. Therefore the property of the carrier candidates used for immobilization were also evaluated on the aspects of pore properties and the compatibility with the cementitious matri. Experimental result show that yeast extract greatly retarded cement hydration and had a remarkable negative effect on the strength of the mortar. The strength was greatly decreased when the addition was higher than 0.34%. The precipitation precursors had moderate effect on the strength and the optimal dosage was 4% for urea and 8% for Ca-nitrate by the mass of cement Argex had a much higher porosity (50%) than that of Lava (16%) and ha a more suitable pore size distribution for immobilizatin of bacteria. Both of them had a good compatibility with the cementitious matrix