Interfacial Bonding Properties And Microcosmic Mechanism Of Resin Light Conductive Cementitious Materials

Resin light conductive cementitious materials(RLCCM) is an advanced building material with function of light conductive, which was composited from light conductive component resin and traditional concrete components. At present, the mechanical properties and light transmission properties of RLCCM were studied, due to the weak bonding strength of cement matrix and resin, it’s easy to cracking off at the interface under stress and resulting in failure of the whole material. In this study, coupling agent was used to improve the interfacial bond strength of RLCCM, and revealed the mechanism from microscopic view.The effect of four coupling agents on interfacial tensile and shear bonding strength of RLCCM were tested by axial tension test and slant shear test. The results showed that: the bonding strength between ement matrix and resin is low, especially the early strength. Silane coupling agent A-151 and aluminate coupling agent have similar effect can significantly improve the interfacial bonding strength. However, silane coupling agent A-151 is relatively economical.The influence of coupling agent on interface transition zone of RLCCM was analysed by microhardness test. The results showed that: the thickness of ITZ reached 200μm and the hardness of resin decreased significantly. The interface after silane coupling agent A-151 and aluminate coupling agent treatment, not only the thickness of “performance weakened area” of resin in ITZ was reduced, but also the micro hardness improved. In addition, it also enhanced the surface micro hardness of cement matrix.The influence of coupling agent on interfacial micro-morphology of RLCCM was observed by environmental scanning electron microscope(ESEM) and atomic force microscopy(AFM). The results showed that: silane coupling agent A-151 has a strong affinity for cement matrix and formed tightly bound fine particles on the surface. The surface become compact and smooth as the particles fill in the tiny gap reduced the roughness. Silane coupling agent A-151 also has a good affinity for resin. Aluminate coupling agent has a good affinity for cement matrix and made the surface more smooth, but the affinity for resin is extremely strong. In a word, the cement matrix and resin combine closely and transform naturally after treated with coupling agent, thus increased the effective contact area of the interface and improved the interfacial bonding properties of RLCCM.The coupling agent chemical reaction with cement matrix and resin was investigated by means of fourier transform infrared spectroscopy(FTIR). The results showed that: silane coupling agent A-151 has chemical reaction with calcium silicate hydrate CSH, but none with resin. The aluminate coupling agent not only has a chemical reaction with the CSH, but also with the transparent resin. The chemical bond at the interface greatly improved the bonding force.Generally speaking, the hydrophilic moieties of coupling agent produce chemical reaction with cement hydration products and enhance the surface micro hardness of cement matrix, thus make the surface more smooth and increases the effective contact area with the transparent resin. The interaction between oleophilic moieties of coupling agent and resin reduce the thickness and improve the micro hardness of “performance weakened area” of resin in ITZ. Therefore, the silane coupling agent A-151 and aluminate coupling agent significantly improved the interfacial adhesion properties of RLCCM.