Primary Study On Nano-materials Reinforced Cementitious Composite

Nano-materials which structural unit sizes range from1nm to100nm is the most potential material in the21st century. Nano-materials have excellent mechanical, magnetic, optical, and thermoelectric properties that differ from the macroscopic material. Portland cement particle size is usually between7and200micrometers, and70%of hydration products of calcium silicate hydrate gel particles are nano-materials. It is possible to enhance the strength and toughness of cement-based materials using nano-materials. This paper studies the influence of multi-walled carbon nanotubes (MWCNTs), nano-SiO2, nano-TiO2, nano-Al2O3and nano-ZnO on the performance of cement-based materials. The microstructure and chemical composition of the composites also studied.This experiment reports the results of the effect of different nano-particles on the cement-based matirial’s fluidity, microstructure and mechanical properties. The results show that the fluidity of mortar reduced significantly with increased content of nano-Al2O3and SiO2, while the nano TiO2and ZnO had no effect on mortar fluidity. Nano-SiO2can improve the3,7and28days compressive and flexural strength by19%and10%, the addition of nano-ZnO prolonged the setting time of mortar and flexural and compressive strength decreased when compared with plain specimens. XRD and SEM analysis demonstrated that nano-SiO2can reduce the content of Ca(OH)2. The hydration reaction is accelerated and the microscopic structure of the hydration products has higher density.2、Carbon nanotubes which have excellent mechanical properties as micro fiber have enormous potential to improve the strength and toughness of the traditional cement-based building materials. The multi-walled carbon nanotubes (MWCNTs) were effectively dispersed in the water with surfactant and then separated by centrifuge, which can keep stable for over3months. This research studied microstructure and compressive strength of portland cement with MWCNTs which were used as an additive material at0%,0.025%,0.05%and0.1%by weight of cement. Results showed that the compressive strength was improved significantly with the increasing amount of the MWCNTs. MWCNTs can improve the7-days,28-days compressive strength by22%and15%respectively. SEM microscopic analysis showed the carbon nanotubes were dispersed well in the cement hydration products, debonding, bridging and mesh fill was observed as well. EDS analysis indicates that good compatibility between MWCNTs and the cement hydration products is obtained.