On the interaction between proteins and cracked cementitious surface

Abstract

• Proteins increased strength recovery and crack filling of cement paste. • Proteins can effectively induce hydrophobization on cementitious surface. • Morphology of ettringite was different in the protein treated samples. While there has been an increasing interest in the area of biocementation for crack healing in cementitious materials, the role of biomolecules as an important constituent in biocementation has not received attention. This paper examines the interaction between proteins, with different molecular structures, and a cementitious surface that can represent a crack surface. The chemical characteristics and microstructure of the product formed on the cementitious surface were studied using Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), X-ray diffraction (XRD), and scanning electron microscopy (SEM). The optical and X-ray micro-computed tomography (micro-CT) imaging were employed to evaluate the crack filling ability of the proteins. The crack healing property of the proteins was investigated using the three-point bend test. The samples treated with proteins demonstrated marked increase in strength recovery as well as crack filling, compared to the control sample. The molecular changes occurring in proteins when exposed to cement chemistry were shown to improve the interfacial strength between the proteins and cementitious surface. It was also found that the proteins can effectively induce hydrophobization on cementitious surface. It was shown that the surface product consisted mainly of calcium carbonate (CaCO 3 ), ettringite, and calcium-silicate-hydrate (C S H). The morphology of ettringite in the samples treated with proteins showed distinct differences compared to that in the control samples.