Self-Healing Properties of Bioinspired Amorphous CaCO3/Polyphosphate-Supplemented Cement

Abstract

There is a strong interest in cement additives that are able to prevent or mitigate the adverse effects of cracks in concrete that cause corrosion of the reinforcement. Inorganic polyphosphate (polyP), a natural polymer that is synthesized by bacteria, even those on cement/concrete, can increase the resistance of concrete to progressive damage from micro-cracking. Here we use a novel bioinspired strategy based on polyP-stabilized amorphous calcium carbonate (ACC) to give this material self-healing properties. Portland cement was supplemented with ACC nanoparticles which were stabilized with 10% (w/w) Na–polyP. Embedding these particles in the hydrated cement resulted in the formation of calcite crystals after a hardening time of 10 days, which were not seen in controls, indicating that the particles dissolve and then transform into calcite. While there was no significant repair in the controls without ACC, almost complete closure of the cracks was observed after a 10 days healing period in the ACC-supplemented samples. Nanoindentation measurements on the self-healed crack surfaces showed a similar or slightly higher elasticity at a lower hardness compared to non-cracked surfaces. Our results demonstrate that bioinspired approaches, like the use of polyP-stabilized ACC shown here, can significantly improve the repair capacity of Portland cement.

Amorphous Polyphosphate and Ca‐Carbonate Nanoparticles Improve the Self‐Healing Properties of both Technical and Medical Cements

“…Preparation of the Nanoparticles: Amorphous Calcium Carbonate Nanoparticles: The particles were prepared as outlined before. [13] The particles were collected, washed with acetone, and dried at room temperature; "Ca-polyP/ACC-NP. "…”

“…As documented before, the particles are largely amorphous by analyzing with X-ray diffraction (XRD). [13] These particles were used for the improvement of the selfhealing potency of the cement. Two methods for application were tested: brush application and blow spinning.…”

“…The latter enzyme is involved in the metabolism (degradation) of inorganic polyphosphate (polyP) which acts as a source of orthophosphate for bone mineral deposition and as a generator for metabolic energy in the form of ATP. [13,14] PolyP is a natural polymer that is formed in every living cell. [15,16] A breakthrough toward the biomedical application was the discovery of how polyP can be fabricated as amorphous nanoparticles (NP) together with a corresponding divalent cation, like Ca 2+ or Mg 2+ .…”

“…A solution has been sketched already previously and applied for biological systems both in vitro and in vivo. [13,24] The basic concept of this technology was the successful stabilization ("freezing") of the amorphous phase of Ca-carbonate by inclusion of polyP during NP formation. In the present study, we prepared amorphous Ca-polyP/calcium carbonate NP ("Ca-polyP/ACC-NP") in a ratio of 20:80 (Ca-polyP:Ca-carbonate).…”

3D Printing of Bioinspired Biomaterials for Tissue Regeneration

“…The inorganic phase plays a key role in the bioactivity improvement of biomaterial matrices. [ 66,67 ] Recently bioinspired mineralization has been applied in multiple biomaterials to enhance the bioactivity of materials system. [ 68–71 ] For example, graphene, as a 2D material has been considered as a potential biomaterial in tissue regeneration due to its large surface area, brilliant mechanical properties, and potential to modulate the biological performance.…”