Effects of pozzolanic and non-pozzolanic nanomaterials on cement-based materials

Although it has been verified that nanomaterials can improve the properties of cement-based materials, the research on the characteristics and mechanism of different types of nanomaterials is still inadequate. Two typical types of nanomaterials, nano-SiO2 (pozzolanic material) and nano-TiO2 (non-pozzolanic material), are utilized in this paper to investigate the combined effects of reactivity, size, and content on the efficiency of nanomaterials in cement-based materials. The experimental results indicate that the size and content effect of nano-SiO2 is obvious. Small size and large content of nano-SiO2 can significantly improve the compressive strength of cement paste. However, the size effect of nano-TiO2 is much weaker than that of nano-SiO2, and the content effect of nano-TiO2 is only obvious at the early age. For the late age compressive strength, the small content of nano-TiO2 shows a similar obviously improving effect as the big content of nano-TiO2. The pore structure analysis shows that both nano-SiO2 and nano-TiO2 can reduce the total porosity of cement paste, but nano-TiO2 is more effective than nano-SiO2 at reducing the harmful pores. Therefore, the small content of nano-TiO2 is more effective to enhance the impermeability of cement-based materials. The results of this paper show that nano-SiO2 and nano-TiO2 have different effects and they should be selected based on the properties requirement of cement-based materials.