Using Microbial Induced Calcite Precipitation to Mitigate Salt-Induced Damage in Concrete Exposed to CaCl2
Presented By: Yaghoob Farnam
Affiliation: Drexel University
Description: This presentation will highlight recent research on microbial-induced calcium carbonate precipitation as a mechanism to mitigate salt-scaling damage in pavement applications.
Role of Microbially Induced Calcite Precipitation on Corrosion Prevention
Presented By: Raissa Ferron
Affiliation: University of Texas at Austin
Description: Microbially induced calcite precipitation (MICP) embodies the innovative approach to inoculate bacterial cells, for carbonate production, in cement and soil matrix. Bio-mineralization in the context of cement-based-materials, is a series of biochemical reaction, followed by accumulation of calcium carbonate. The major issue that needs to be dealt, for microbial precipitation in concrete, is the integration of the microbial cells in the cementitious mix. There are several ways to accomplish such bacterial incorporation. Two well-known methods are direct suspension of bacterial cells and encapsulation. It has been observed that MICP can continue internally for extended periods of time in cement paste and mortar when the bacterial solution, along with nutrients, replace the mixing water. The application of such bio-mineralization can be leveraged to improve corrosion resistance of bioinspired cementitious materials. The calcite precipitate is expected to seal up cracks internally, thus improving the concrete corrosion resistance. Being self-healing in nature, this mechanism of crack sealing doesn’t require detection and intense repair on concrete structures. It is expected that once concrete corrosion has initiated the concrete and the rebars will experience a reduced rate of corrosion in the long run, thus extending service life.
Materials Inspired From Nature: Bio-Derived Admixtures For Cement-Based Materials
Presented By: Zeynep Bundur
Affiliation: Ozyegin University
Description: Interaction of microorganisms and building materials, particularly with concrete and stone, were a main topic of interest for many researchers. Initially, studies focused on degradation of concrete by organic acids, produced by microbial acidification such as microbial induced corrosion. However, the interaction of microorganisms with materials is not necessarily negative. Recent research in the field shows that microorganisms can have positive effects on cement-based materials, which could actually result with stronger materials through biocalcification. Our studies revealed that it was possible to develop smart-cement based materials that could self-heal microcracks by leveraging metabolic activity of microorganisms. Through the development of this so-called self-healing bio-based mortar, it was also possible to improve the fresh state performance of the mix. It was found that the viscosity and yield strength of cement paste could be increased by simply suspending the bacterial cells in mixing water. Depending on the application and mixing ingredient these bacterial cells could act as both self-healing agents and viscosity modifying agents. Thus, it is possible to design more sustainable cement-based materials by using bio-derived additives.
Biomimetic Antifreeze Polymers: Can they Mitigate Freeze-Thaw Damage?
Presented By: Shane Frazier
Affiliation: University of Colorado Boulder
Description: Ice is one of the few substances on Earth that expands when it freezes. Consequently, this expansion causes damage to porous cementitious materials that absorb water and undergo freeze-thaw cycling. Inspired by nature, the objective of this work is to design, synthesize, and characterize biodegradable, biomimetic antifreeze polymers (BAPs) that explicitly mimic the behavior of antifreeze proteins (AFPs) naturally found in plants, fish, insects, and bacteria. The ultimate goal of this work is to enhance the freeze-thaw durability of ordinary portland cement (OPC) paste without the use of air entraining agents (AEAs), thereby increasing the strength and improving the long-term durability of cementitious materials. This presentation will highlight recent research that has shown that small additions of functional bio based polymeric materials that exhibit antifreeze activity can mitigate freeze-thaw damage in OPC paste without direct addition of commercial AEAs. The chemical functionalities of these BAPs mimic the amino acids that are found in natural AFPs, which have also demonstrated ice crystal growth inhibition in alkaline environments. This presentation will discuss the advantages of synthetic BAPs, which, in contrast to natural AFPs, offer a more robust, cost-effective material that can maintain activity in the harsh environments of OPC pore solution.
Influence of Biopolymers on Calcium-Silicate-Hydrate
Presented By: Ali Ghahremaninezhad
Affiliation: University of Miami
Description: Mother nature has produced several examples of inorganic-organic nanocomposites, including abalone shells, bones, see urchins, with properties unmatched by engineering materials. Such enhanced properties in these nanocomposites are due to the role of certain biopolymers with specific functionalities and structures that govern the formation, growth and microstructure of these materials. Calcium-silicate-hydrate entails a nanostructure and comprises the main binding phase of cementitious materials, and as such, determines the physical and mechanical properties of cementitious materials. This presentation aims to provide insights into the interactions between biopolymers and calcium-silicate-hydrate. Analytical techniques including x-ray diffraction and Fourier transform infrared spectroscopy were used to probe atomic structure; scanning electron microscopy and atomic force microcopy were utilized to study microstructure, and nanoindentation was adopted to assess the nanomechanical characteristics of calcium-silicate-hydrate modified with biopolymers. The influence of functional groups including charged, hydrogen bond forming, and hydrophobic groups, on the properties of calcium-silicate-hydrate is discussed.
Genetically Engineered Bio Cementitious Composites
Presented By: Wil Srubar
Affiliation: University of Colorado Boulder
Description: Over the past 20 years, considerable research efforts have been aimed at improving properties of cement-based materials using microbial-induced calcium carbonate precipitation (MICCP). Generally, it has been shown that MICCP can reduce permeability and increase compressive strength in these systems by filling pores and sealing microcracks. Previous studies have also interrogated the potential for embedded microorganisms to survive long-term and promote crack-sealing in situ during the material’s service life with some success; however, it is known that the long-term viability of microorganisms in cement-based systems is threatened by harsh environmental conditions that are intrinsic to ordinary portland cement (OPC) concrete, including high pH, elevated temperature, and nutrient depletion. In this study, Synechococcus PCC 7002, a common cyanobacterium capable of MICCP, was used to create a cement-free, hydrogel-based “living” mortar. A bio-based hydrogel was chosen to act as both the primary binding agent and as a scaffold for microbial activity. This presentation will discuss a suite of hydrogel-based microbial mortars that were examined for their mechanical and mineralogical properties, cell viability, and propensity to regenerate when subjected to damage and temperature gradients. Results of this research suggest that these hydrogel-based microbial mortars generally exhibited acceptable mechanical properties, greater property tunability, and more favorable environmental conditions for beneficial microbial activity than has been observed in cement-based mortars.