The biomineralization technique of crack remediation in construction mortar can be achieved through the incorporation of calcifying bacteria within the mortar matrix. However, the thermal and autogenous shrinkage associated with the hydration of cement can be detrimental to the survival of the bacterial spores. Encapsulation of the spores in a matrix such as superabsorbent hydrogels, specifically sodium alginate, can provide protection from such detrimental conditions while also serving as a water reservoir for the metabolic activity of the bacterial cells. This paper investigated the addition of sodium alginate capsules prepared through spherification in construction mortars, aiming to preserve and optimize rheological, physical and mechanical properties, and to release bacteria when cracks occur. Mortar formulations with capsules containing Lysinibacillus sphaericus were calculated in order to maintain the granulometric distribution of standard formulation, thus obtaining products with excellent rheological, physical and mechanical properties, and allowing the addition of up to 1% capsules. Multivariate analysis of variance was applied at each age, showing that formulations with capsules kept the same properties as the original formula. After cracking, it was possible to observe the action of the released bacteria, through the formation of crystalline structures at the cracks. The capsules were prepared through a simple and cheap process, and it was proved that not only they do not affect concrete properties, but also are effective in both protecting the bacteria during mixing and hardening and releasing it after cracking.

This work presents an economical, technical, and environmentally correct solution for the disposal of long neck bottles (which cannot be bottled more than once), by replacing fine aggregates (sand) with residue of ground glass from long neck bottles in the production of reactive powder concrete (RCP). Using a reference formulation for RCP containing natural sand, this raw material was replaced in 12.5, 25, 50, 75 and 100 wt.% by glass residues, evaluating the physical and mechanical properties in the specimens at the ages of 7, 14, and 28 days. The ground glass was characterized by X-ray Fluorescence and DSC tests, indicating that it is a typical sodo-calcium glass, with a glass transition temperature equals to 560C. Grain size distribution and optical microscopy assays of natural sand and ground glass indicated that the comminution let to the acquisition of glass with granulometry similar to that of natural sand, but with very different geometries and roughness. The replacement of natural sand by 100% of ground glass presented the best results of mechanical properties, reaching 85% of the mechanical strength value of the reference composition, with about 96MPa; this composition also presented the lowest water absorption value (3.94%) and the lowest void index (9.33%) among all compositions. The results indicated that the replacement of sand by powder from long neck bottles is potentially feasible, promoting an environmentally correct destination for this residue in the construction sector, bringing a reduction in environmental impact, and generating concrete within the technical standards required by the norm.

The use of calcium carbonate for closing cracks in concrete by the action of biomineralizing bacteria has been investigated. However, these bacteria are fragile and susceptible to the reaction medium, and they must be protected by encapsulation, until the moment they must carry out the biomineralization process. This research covered the study and optimization of the production of sodium alginate capsules for subsequent encapsulation of biomineralizing bacteria. The research also investigated the effect of these capsules (added in different percentages) in concrete masses using a CP II – E Portland cement (ABNT NBR Standard), formulated from the Andreassen equation. The samples were characterized in their fresh and hardened state. The swelling tests indicated that the sodium alginate capsules provided good conditions to receive the bacteria, to keep them alive and to be mixed in the concrete, presenting enough mechanical strength. Among the investigated conditions, the composition formulated using the Andreassen coefficient equal to q=0.37 and with the addition of 1.5% of sodium alginate capsules was the one that presented the most promising results; and after 28 days of curing, the mechanical strength to compression was 45.4 MPa, with the value within ABNT NBR 11578, since it establishes a minimum of 32 MPa.