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.

Abstract

Poly(lactic acid) (PLA) is the most widely used bio-based and biodegradable polymer in the food packaging sector, due to its market availability, competitive cost and ease of processing. However, PLA has some limitations in terms of its mechanical, thermal and barrier properties, which can be improved by adding inorganic particles to the polymer matrix to obtain hybrid organic-inorganic composites with improved properties. Among all the inorganic particles, Halloysite Nanotubes (HTH) and Diatomaceous Earth (DT) are of special interest because their hollow structure offers the possibility of incorporating active agents inside them to be released in a sustained way to the food, extending their shelf life. In the present work, rosemary (Rosmarinus Officinalis) essential oil was encapsulated in the cavities of NTH and TD, the active particles were incorporated into a PLA polymeric matrix and processed by extrusion followed by cast-film process to simulate industrial conditions. The presence of NTH and TD improved the Young's modulus of PLA, while rosemary oil acted plasticising the system increasing the elongation at break allowing flexible films to be obtained. The obtained materials showed antioxidant capacity, demonstrating the potential to produce biodegradable active materials of interest in the food packaging sector.