Effect of carbon nanotubes/clay hybrid composite on mechanical properties, hydration heat and thermal analysis of cement-based materials

Carbon nanotubes (CNTs) are known for their superior mechanical properties and have been found to increase the strength of cement-based materials. CNTs can also be synthesized on clay mineral by chemical vapour deposition (CVD). In this work, CNTs/Clay hybrid composite were added at 0.02 wt% up to 0.20 wt% in mortars and the effect on cement-based materials properties were investigated. Cumulative heat release and heat flow of cement paste were measured using isothermal calorimetry technique. Phase identification was carried out on samples at 28 days by X-ray diffraction and thermogravimetric analysis. Compressive strength, flexural strength and density of the mixes were determined at 28 days. Compressive strength was found to increase with increase CNTs/Clay hybrid composite and the optimal was found at 0.10 wt%. This is due to their ability to both reinforce and fill the pores in the cement matrix. Thermogravimertric results showed that at 0.10 wt% of CNTs/Clay hybrid composite and at approximate to 120-125 degrees C a slight increase in the mass loss can be observed. Moreover, isothermal calorimetry results showed that CNTs/Clay hybrid composite was found to accelerate early cement hydration.