Research On Influences Of Nanomaterials On Calcium Silicate Hydrates And Cement-Based Materials

The use of nanomaterials has become an important method to enhance properties of cement-based materials,and this approach has been applied frequently.To have a further realization of the mechanisms about influences of nanomaterials on cement-based materials,researches are required to study on interactions between these materials.In this research,there experiments are designed to research on effects of nanomaterials on cement-based material and calcium silicate hydrates.Because of their high specific surface area,nanomaterials could enhance properties of cement-based material by its interfacial effects.Since calcium silicate hydrates are the main products of cement hydration,which have major contributions to strength and durability of concrete,studies on influences of nanomaterials on calcium silicate hydrates are required.In this research,graphene oxide is combined with calcium silicate hydrates manufactured by double decomposition.X-ray diffraction,scanning electron microscopy,transmission electron microscopy,²⁹Si solid state nuclear magnetic resonance and X-ray photoelectron spectroscopy are applied to characterize synthesized compound calcium silicate hydrates.The result shows that graphene oxide could increase polymerization of calcium silicate hydrates,especially on the interface between graphene oxide and calcium silicate hydrates.Meanwhile,graphene oxide also has effects on crystallinity and structure of calcium silicate hydrates.Using modifications on nanomaterials to enhance cement-based materials has become important in recent researches.This research has synthesized calcium silicate hydrates coated carbon nanotubes and applied these modified carbon nanotubes to cement pastes.With these modified carbon nanotubes,the strength of cement pastes is higher than samples mixed with normal carbon nanotubes.And for cement pastes with 0.24wt.%modified carbon nanotubes,the flexural and compressive strength at 28 days have increased by 6.8%and 6.6%separately.Using thermal analysis and other characterization methods,it has been found that the introduction of calcium silicate hydrates coated carbon nanotubes has resulted in the increase of calcium hydroxide,which shows the promotion of cement hydration caused by modified carbon nanotubes.While using nanomaterials to modify concrete,exploring new nanomaterials to research on their possibility of application in cement-based materials is also important.Using acetylene and zeolite Y,this research has used chemical vapor deposition to synthesize zeolite-templated carbons.Because of their nanopore structure and high surface area,zeolite-templated carbons have high specific surface area,which enable them have potential to enhance cement-based materials.Calcium silicate hydrates are synthesized by double decomposition and combined with zeolite-templated carbons.The microstructure and composition of synthesized calcium silicate hydrates are characterized.The morphology has shown that calcium silicate hydrates have been well mixed with zeolite-template carbons.In addition,the application of zeolite-template carbons could also increase the polymerization of calcium silicate hydrates,which derives from surface effects of nanomaterials.