چكيده به لاتين
Concrete, as one of the most widely used building materials, in addition to its positive properties, has significant weaknesses such as low tensile strengh and high permeability. This has led researchers to seek to eliminating or reducing weaknesses and improving the desired properties of concrete. The main component of concrete is cement, and cementitious composites derive most of their properties from cement. If the nano-structure of the cement could be changed, many of the cement composite weaknesses would be eliminated. Graphene oxide nanosheets – a nanomaterial that have two unique properties: reinforcement effect and very high specific surface area- play a useful role in improving the tensile strength of cementitious composite and modifying its nanostructure, which leads to greater durability. The most important challenge in using graphene oxide is clumping. The use of pozzolans is one way to reduce clumping. To achive this goal, pumice has been used to reduce clumping and take advantage of its positive side effects such as reducing cement consumption. In order to determine how the cementitious composite incorporating graphene oxide and pumice works, a number of mortar mix designs containing different percentages of pumice and a constant amount of graphene oxide were selected and then, their workability, compressive strength, flexural strength, length change in sulfate solution, rapid chloride migration test, capillary water absorption and porosity by gas porosimetery were measured. The results show that the mortar containing graphene oxide and pumice has higher compressive and flexural strength, more resistance to the penetration of sulfate and chlorine ions, as well as less psychological, porosity and permeability than the control mortar. The results show that the mortar containing graphene oxide and pumice has higher compressive and flexural strength, more resistance to the sulfate and chloride attack, as well as less workability, porosity and permeability than the control mortar. Mortars containing 0.05% graphene oxide and 20% pumice can increase compressive and flexural strength by 51.2% and 6%, respectively, and also can decrease expansion in sulfate solution, chloride migration coefficient, capillary water absorption and effective porosity by 51.9% and 38%, 48.4% and 79.7%, respectively. Despite the mechanical properties and durability improvement, the rate of improvement is expected to be higher due to the positive properties of graphene oxide. This means that although pumice has contributed to the dispersion of graphene oxide, the presence of pumice alone cannot improve the dispersibility. However, the role of pumice in reducing cement consumption and increasing the mechanical strength and durability of cement mortar is undeniable; especially that pumice is one of the natural and available pozzolans in the country of Iran and can be a step towards sustainable development.
