Effect of proteins on biocementation in construction materials

Area of Science:

• Materials Science
• Biochemistry
• Civil Engineering

Background:

• Enzymatic-induced calcium carbonate precipitation (EICP) is a promising method for material modification.
• Understanding protein interactions is crucial for optimizing EICP in complex environments like cementitious systems.
• High pH in cementitious environments can negatively impact enzyme activity and precipitation.

Purpose of the Study:

• To investigate the influence of proteins on the binding properties and microstructure of EICP in a cementitious environment.
• To evaluate the protective effect of proteins on urease enzyme activity under high pH conditions.
• To characterize the crystalline phases formed during protein-modified EICP.

Main Methods:

• Protein modification of EICP precipitates.
• Assessment of precipitate binding to glass and cement paste surfaces.
• Enzyme activity assays in cementitious conditions.
• Fourier-transform infrared spectroscopy (FTIR), Scanning Electron Microscopy (SEM), Thermogravimetric Analysis (TGA), and X-ray Diffraction (XRD) for material characterization.

Main Results:

• Protein-modified precipitates showed improved binding to surfaces compared to controls.
• Proteins partially shielded urease from high pH, mitigating activity reduction.
• Protein-Ca2+ complexation facilitated CaCO3 nucleation and crystallization.
• Vaterite was the dominant CaCO3 polymorph in cementitious environments, unlike calcite in deionized water.

Conclusions:

• Proteins significantly enhance the binding capabilities of EICP in cementitious settings.
• Protein shielding of urease is key to maintaining precipitation efficiency in high-pH environments.
• Protein-induced gel networks act as effective nucleation sites, influencing CaCO3 polymorph formation (vaterite).