The Synergistic Effect Of Nano-material With Silica Fume On Impermeability Of Concrete

The durability of concrete is very important for the reliability of concrete in service,especially under harsh conditions.And the impermeability property of concrete is an important factor for its durability.Recent research shows that nano-modification is an effective way to improve the durability of concrete.That's because nano-materials have many special properties,such as higher specific surface areas and higher activities.Nano-materials can improve the interfacial transition zones and the pore structures through filling effect,nucleation effect and pozzolanic effect in cement-based materials.Recently there are many researches on the synergism of nano-materials and fly ash.However,there is a large gap between the grain composition and the activity levels of the nano-materials and fly ash.Therefore,the silica fume may be mixed into concrete to enrich the grain composition and activity level,so as to improve the impermeability performance of concrete.The paper studies the effect of nano-materials with the silica fume for the electric flux and rapid chloride ion permeability coefficient of concrete.The experiment measured the effect of nano-materials for the hydration heat,the content of non-evaporation water,hydration products,pore structure and interfacial transition zone,which illustrates the mechanism of the synergy effect for the properties of concrete impermeability performance.The main results are as follows:?1?After the nano-materials and silica fume is into the addition of cement,the rheological property of cement paste gets worse,the plastic viscosity and yield stress increases.Adding 30%of the fly ash and effective naphthalene series reducing water in the mixing of concrete can make the performance of concrete meet the experimental requirements.?2?The silica fume can improve the compressive strength of concrete,the optimum content of silica fume is 9%,and the compressive strength of 28d can reach 66.31Mpa,which improves 85.69%with respect to blank sample,but it is smaller in 3d.When 1.2%of nano-silica and silica fume is in the synergy,if the amount of silica fume was 9%,the compressive strength can get the maximum,and the compressive strength of 28d was70.98MPa.In the presence of silica fume,the strength of nano-silica in 3d was significantly higher than that in 28d.Nano-silica with silica fume can effectively improve the compressive strength of concrete.Mixed with 1.8%of nano titanium dioxide can make similar effects with the nano silicon dioxide for the compressive strength of concrete,but because nano titanium dioxide can't have ash activity,the increasing strength is lower than the nano silicon dioxide?3?Nano-silica with silica fume can effectively improve the chloride ion penetration of concrete.Nano-silica and silica fume respectively adds into concrete can reduce the electric flux of concrete and fast chloride permeability coefficient.When they are respectively mixed,the optimal dosage was 2%of nano-silica and 9%of silica fume respectively.Nanometer silicon dioxide has an advantage in the decrease of the early electric flux,while the silica fume decreases greatly in 28d.When the 1.2%of nano-silica and 12%of the silica fume were synergized,the chloride penetration coefficient of the concrete and the electric flux reached the lowest,which reached 0.80×10^-12m²/s and 154.49C at the time of curing to 28d.The experimental data show that nano silicon dioxide with silicon ash can accelerate the cement hydration and reduce the content of calcium hydroxide and increase the content of the non-evaporation water.The nano-silica cooperating with silica fume on the active effect and crystal nucleus effect can make the hydration products in 3 d and 28 d significantly increase and get more dense.At the same time,the synergistic effect of nano-silica and silica fume on grain composition can decrease the total porosity by 5.3%,and the pore structure gets optimized.The synergistic effect of nano-silica and silica fume on the activity and size can effectively improve the bonding strength and porosity of the interfacial transition zone,which can optimize the interface transition zone.?4?The synergistic effect of nano-TiO₂ with silica fume can improve the chloride ion permeability of concrete.When the content of nano-TiO₂ was 1.8%and the content of silica fume was 12%,the electric flux of concrete and the rapid chloride ion permeability coefficient were the lowest,and which is 180.83 C and 0.98×10^-12m²/s respectively at 28d.In the presence of 9%silica fume,nano-TiO₂ can be used as the crystalline nucleus to promote the hydration of cement.The total hydration heat in 71h is increased by 5.09%compared with the addition of silica fume.At the same time,nano-TiO₂ ordinates with silica fume can increase the content of the calcium hydroxide compared with S9 after 3d,which shows that the nano-TiO₂ cooperates with silica fume can promote the hydration of cement.So,the hydration products gets more dense on the microstructure.At the same time,nano-TiO₂ and silica fume are synergistic on the scale can reduce the porosity and optimize the pore structure,which can make the proportion of harmful pore reduce from 16.84%to3.84%.The synergistic influence of nano-TiO₂ with silica fume on the effect of nucleation and size can effectively improve the chloride ion permeability of concrete.