Study On The Effect Of Bentonite On The Impermeability Of Concrete

The anti-permeability of concrete is the first line of defense for the durability of concrete.Improving the anti-permeability of concrete is not only conducive to improving the durability,but also to increasing the service life of concrete.It is necessary to conduct in-depth research on its anti-permeability and sulfate resistance.Compressive strength test,gas permeation test,chloride ion permeation test,sulfate wet-dry cycle test and other methods were used to study the mechanical properties,anti-permeability and sulfate erosion resistance of concrete with different bentonite content and water-binder ratio.And other microanalysis methods such as XRD analysis,scanning electron microscopy analysis,mercury intrusion porosimetry to analyze the microstructure and fractal characteristics of concrete.The research results show that:Adding an appropriate amount of water reducing agent can effectively improve the workability of concrete.On the basis of adding 20%fly ash and mineral powder,as the amount of bentonite increases,the compressive strength of the concrete decreases,and the compressive strength of the concrete further decreases when the water-binder ratio is increased.When the water-binder ratio is 0.4 and the amount of bentonite is 4%,the compressive strength of concrete is lower than that of other groups of concrete.Appropriate addition of bentonite and reduction of water-binder ratio can improve the concrete's resistance to gas penetration,chloride ion penetration and sulfate attack.When the water-binder ratio is 0.3 and the amount of bentonite is 4%,the concrete's anti-permeability and The resistance to sulfate attack is relatively good.Correlation analysis found that the gas permeability and chloride ion permeability of concrete were significantly positively correlated,the concrete permeability was negatively correlated with the resistance to sulfate attack,and the gas permeability was well correlated with the compressive strength and corrosion resistance coefficients.XRD analysis found that the Ca?Al Si O₄?₂diffraction peak height gradually decreased with the increase of the amount of bentonite,which may be the cause of the decrease in the strength of the concrete.Scanning electron microscope analysis revealed that the concrete structure with 4%bentonite had fewer pores.Moreover,the porosity of the concrete structure was further reduced when the sulfate was wet-dried 10 times,but when the number of wet-dry cycles reached 30 times,a lot of pores appeared in the concrete structure.Analysis by mercury intrusion pore method found that when the water-binder ratio is 0.3and the amount of bentonite is 4%,the average pore size and pore volume of the concrete are relatively small,the harmful pore size distribution is relatively small,and the fractal dimension is relatively high.The concrete has better anti-permeability and sulfate attack resistance.When the sulfate is wet and dry 10 times,the average pore size and pore volume of the concrete are relatively small,the harmful pore size distribution is relatively small,and the fractal dimension is relatively high.the reason.