چكيده به لاتين
By increasing the application of nanoparticles in different sciences, the use of nano-scale additives in the cementitious environment has been considered by researchers. The remarkable thing about these nanoparticles is that they can not improve the properties of cement composites if they are not applied with proper spreading. One of the nanoparticles most recently considered by researchers is graphene oxide. Among the properties of graphene oxide, it can be noted that the high specific surface area, tensile strength and high elasticity modulus, high electrical and thermal properties, have resulted in its application in cement composites. But the use of a suitable method for uniform dispersion of graphene oxide in the cement environment is very important, despite of the graphene oxide hydrophobility and its high ability to spread in water, this nanomaterial has a strong tendency to agglomaration because hydrated cement solution that basically contains alkaline ions such as potassium, sodium and calcium and has a high alkalinity.
Due to the process of graphene oxide dispersion which in addition to being time consuming and costly,even could damage the graphene grid, it is important to solve the problem of the grinding of this nanoparticle, while using the inappropriate dispersion of these nanoparticles can even create Weaknesses in the composite result and consequently reduce the resistance. Considering the importance of this issue, in the present study, the combination of nanoparticles of graphene oxide and pumice pozzolan has been used to improve the dispersion of graphene oxide nanoparticles in cementitious environments and as a result of improving the properties of composite composites.
In this study, firstly, the effect of free ions and new alkaline levels as factors that can cause agglomaration is studied, and then mechanical properties and permeability tests on cement composites containing these two additives were performed. Cement composite specimens with percentage of 0.02 and 0.04 graphene oxide with 10, 15 and 20% pumice pozzolan have been prepared with standard mixing design and the flow table, initial setting test, mini slump, compressive strength, tensile strength, flexural strength,Sorptivity , electrical resistance and Water absorbtion.
The results showed that composites containing 0.04% graphene oxide and 15% pumice pozzolan increased compressive strength by 27% and 22%, flexural strength by 39% and 44%, and resistance to tensile strength by 21.8% and 25%, and resistance to mechanical strength of 27% and 18% respectively at the age of 28 and 90 days, respectively. 20% decrease in sample porosity at 90 days of age, and decrease of 24.3 and 17% in capillary absorption, 18.1% and 16% in water absorption at the age of 28 and 90 years.
