Production of concrete compatible biogranules for self-healing concrete applications

Abstract

Recently, cost-efficient nitrate reducing biogranules were suggested as an alternative to axenic microbial cultures for development of microbial self-healing concrete. In a marine environment, biogranule containing microbial self-healing concrete showed simultaneous self-healing of cracks and immunisation against rebar corrosion. Yet, information about the production strategy of these biogranules and their compatibility with a mortar matrix is limited. This study presents the production of biogranules and their compatibility with mortar specimens when incorporated at dosages between 0.36% to 4.30% w/w cement (0.25% to 3% of bacteria w/w cement). In-house produced biogranules composed of 70% bacteria and 30% of minerals w/w of biogranule were used for the compatibility tests. In test mortars, calcium formate (CF) and calcium nitrate (CN) were used as regular nutrient admixtures, and nutrient content was set identical in every batch. Up to 2.9% incorporation, biogranules had no significant influence on the fresh properties of mortar. More than 2.9% incorporation caused poor workability and a 26% decrease in 3-Day compressive strength of biomortar specimens. Overall, the biogranules produced are compatible with a cementitious matrix up to 2.9% w/w cement, and even up to 3.6% if early age strength is not essential, which makes biogranules one of the most compatible microbial healing agents among the suggested agents in the literature.

Self-Healing Performance of Biogranule Containing Microbial Self-Healing Concrete Under Intermittent Wet/Dry Cycles

“…ACDC biogranules were obtained successfully and quality assessment revealed that the properties were similar to those produced in previous studies (data not shown, can be found in [13]). Obtained granules are visually represented in Figure 1.…”

“…After 60 days of operation, the first batch of biogranules were harvested and dried in a ventilated electric oven at 60ºC for 48 hours. These granules were fresh new ACDC granules cultivated from old dry ACDC granules and revealed similar properties [13]. Upon drying, granules were further allocated into three portions based on their particle sizes (0.45 to 2 mm) and stored in closed containers at room temperature.…”

“…As a cost-efficient alternative to axenic cultures, non-axenic biogranules, so called Activated Compact Denitrifying Core (ACDC) were proposed as a new generation microbial healing agent [2]. Apart from their 10 to 20 times lower production cost [2], these microbial granules are composed of selfimmobilized bacteria and mineral layers, thus they do not require any additional protective carrier for concrete incorporation [13]. These biogranules are incorporated into concrete as a dry powder which makes them more practical for applications in situ when compared to bacterial solutions.…”

The Versatility of Polymeric Materials as Self-Healing Agents for Various Types of Applications: A Review

“…Furthermore, the studies on the cultivation of self-protected bio granules by Sonmez and Ersan (2019) proved that the activated compact denitrifying core, ACDC bio granules do not have any impact on the strength development and are compatible with hardened mortar [ 106 ]. In their experiment, bio granules with activated denitrifying core were used in tested bio-mortar mixtures as a microbial agent.…”

Biological Self-Healing of Cement Paste and Mortar by Non-Ureolytic Bacteria Encapsulated in Alginate Hydrogel Capsules

“…In addition, accurate and exact survival determination can provide insight into the protective abilities of the capsule material and possibly the self-healing behavior the capsule offers (i.e., if healing agents are retained in the capsule or leached into the cement environment). While metabolic measurements such as the urea consumption (the TAN method) for ureolytic bacterial [ 28 , 45 ] and NO 3 − /NO 2 − consumption measurements for non-ureolytic NO 3 − /NO 2 − metabolizing bacteria [ 4 , 29 , 46 , 47 , 48 , 49 , 50 ] can be considered reliable measurements for bacterial survival and activity, while direct and accurate bacteria survival measurements are limited for non-ureolytic bacteria that do not metabolize NO 3 − /NO 2 − , e.g., those who oxidize organic salts. Since this class of non-ureolytic bacteria are the most prevalent in non-ureolytic concrete self-healing research, there is a need for better quantitative survival measurement strategies for such systems.…”