Experimental Study on Property of Polymer Cement Based Composite Modified by Nano-SiO2

The utilization of Nano-SiO2(NS) in polymer cement based composite can promote its hydration rate, enhance its mechanical property, change its microstructure of hydration products and improve its performance of interface transition zone (ITZ). Hence, mechanical properties, drying shrinkage property, microstructure and composition of hydration products and ITZ related performance of polymer cement based composite modified by various dosages of NS were studied by adopting the combination of macro and micro methods, including electro-hydraulic pressure testing machine, cement mortar comparator, X-ray diffraction (XRD), scanning electron microscope (SEM) and X-ray energy spectrometer (EDS). The test results reveal that NS can enhance the strength of the polymer cement mortar (PCM), especially at the early age. With the incorporation of NS, the dry shrinkage rate of PCM increases, which is also more significantly pronounced at the early age. It can be seen from XRD and SEM results that the degree of polymer cement based composite hydration is accelerated because of mixing NS. Pozzolanic reaction of NS can alter the number, microstructure and composition of hydration products of polymer cement based composite, and reduce the Ca/Si atomic fraction ratio of C-S-H gel. ITZ between polymer cement hardened paste and aggregate is improved due to the reaction of NS with Ca(OH)2 rapidly, resulting in a more compact structure without obvious cracks and holes. It tends to be an increased micro-hardness in ITZ as a result of the dense hydration products and the generation of more C-S-H gel. © 2021, Editorial Department of Journal of Hunan University. All right reserved.