Two-Part Bio-Based Self-Healing Repair Agent for Cement-Based Mortar

Abstract

Factors affecting durability of concrete structures are generally associated with each other. Due to its brittle nature, concrete can crack under stress and these cracks are one of the main reasons for a decrease in service life in concrete structures. Therefore, it is crucial to detect and recover microcracks, then to repair them as they were developed to wider cracks. Recent research in the field of concrete materials suggested that it might be possible to develop a smart cement-based material that is capable of remediate cracks by triggering biogenic calcium carbonate (CaCO3) precipitaton. This paper summarizes a study undertaken to investigate the self-healing efficiency of Sporosarcina pasteurii (S. pasteurii) cells immobilized on both diatomaceous earth and pumice, to remediate flexural cracks on mortar in early ages (28 days after mixing). To obtain a two-phase bio additive, half of the minerals were saturated with a nutrient medium consisting of urea, corn-steep liqueur(CSL) and calcium acetate and the cells with immobilized to the other half without nutrients. Screening of the healing process was done with ultrasonic pulse velocity (UPV) testing and stereomicroscopy. With this approach, the cracks on mortar surface were sealed and the water absorption capacity of the so-called self-healed mortar decreased compared to its counterpart cracked mortar samples.

The performance evaluation of protection barriers in bacterial self-healing mortar

“…Therefore, they interact with water [29][30][31]. The higher water absorption capacities of bentonite, diatomaceous earth, sepiolite, and pumice used in this study were determined as 300%, 110%, 80%, and 45%, respectively [13]. The impact of incorporating bacteria on shrinkage showed different results regarding mineral type.…”

“…Previously, our studies showed that natural minerals such as sepiolite, diatomaceous earth, bentonite, and pumice could be used to immobilize bacterial cells to trigger self-healing in mortars [12,13]. Herein, the biological self-healing additive effectively remediates flexural cracks in less than 21 days.…”

Immobilization of Bacterial Cells on Natural Minerals for Self-Healing Cement-Based Materials

“…Even though there were CaCO 3 precipitates in the form of calcite, there were few distinct indications of bacterial cells found in samples prepared with bacterial cells immobilized in sepiolite. Previously, our studies revealed that sepiolite might actually create a suitable bedding environment for the bacterial cells due to its relatively larger pores compared to other minerals like diatomaceous earth, which might actually hinder visual indication of cells on the precipitates (Tezer, 2020). The cells might actually be locating in-between an interface between sepiolite minerals and CaCO 3 precipitates.…”

“…It should also be noted that there is not a direct correlation between the initial cell content used in the mix and final cell concentration obtained after crack healing. The initial 2 g of bacterial cells correspond to almost 10 9 CFU/mL grown in 300 mL nutrient medium for 24 h for B series of mixes (Tezer, 2020). Similarly, for 1 g it is 10 9 CFU/mL grown in 150 mL nutrient medium for 24 h for BN series samples.…”

Çimento-esaslı harçlarda kendiliğinden iyileşmenin sağlanması için 2 bileşenli biyolojik katkı maddesinin geliştirilmesi

“…Bu durumda, aktif S. pasturii hücrelerinin DE üzerine sabitlenmesi hücrelerde benzer bir pasif uyku hali (spor benzeri) sağlayabilir ve numunelerde çatlama meydana geldikten sonra, sağlanan besi yeri ile CaCO3'ü çökeltmek için tekrardan aktif hale gelmiş olabilecekleri düşünülmektedir. Besi yeri kısıtlı ile karışıma eklenen ve çatlak oluşumundan sonra sadece su sağlanan 2P numunelerinde diyatom kullanılması bakterilerin daha uzun süre uyku halinde korunmasını sağladığı düşünülmektedir [24]. Kontrol numunelerinden elde edilen veriler sonucunda (DE-C ve PUM-C), minerallerin çatlaklardaki kapanmaya olan etkisi %15'in altındadır (Bkz.…”