Experimental Study On Durability Of Concrete With Nano-particles Under The Influence Of Both Cl~- Permeation And Alkali Aggregate Reaction

With the rapid development of the national economy and the progress of engineering technology,in order to ease the traffic pressure in coastal areas and facilitate people to travel,more and more undersea tunnels and cross-Sea bridge construction plans have been put on the agenda.Due to the harsh service environment,the durability of marine concrete is tested by multiple factors,among which the combination of chloride ion(Cl")penetration and alkali aggregate reaction(AAR)is an important combinatorial factor affecting the durability of marine concrete.Cl-penetration can lead to corrosion of marine concrete steel bars,which in turn affects their strength and durability.The internal concrete will produce a large number of cracks with the occurrence of alkali aggregate reaction,thus reducing the strength of concrete and leading to the intrusion of erosive salts such as Cl-.Therefore,it is necessary to study the durability of marine concrete under the combined action of Cl" penetration and alkali aggregate reaction.Unlike other materials,nanomaterials with smaller particle sizes,larger specific surface area and many unique physical and chemical properties,are known as the "Most promising materials of the 21st century".At present,using the special properties of nanomaterials to improve the strength and durability of concrete has become a research hotspot,and achieved a series of results.Nano-materials have many unique physical and chemical properties and are known as "the most promising materials of the 21st century."At present,the special properties of nanomaterials are used to mix the appropriate amount of nanomaterials into concrete to improve their strength and durability,which has become a hot research topic,and a series of results have been obtained.In this paper,the appropriate amount of nano-SiO2 and Nano-Al2O3 are mixed into marine concrete in order to improve the durability of concrete under the combined action of Cl-penetration and alkali aggregate reaction.The main research contents of this paper are as follows:(1)Comparing the compressive strength test results of nano-concrete and ordinary concrete,the influence law of nanomaterials on the compressive strength of concrete is revealed.(2)Through the verification test of the interaction between plain concrete Cl-penetration and AAR,the interaction between the two factors in affecting the durability of concrete is studied,and the interaction mechanism is revealed.The test results show that these two factors have mutual promotion effect on the durability of concrete.(3)The nano-concrete was placed in fresh water and artificial seawater(0.5 times times,1 times times,twice times),the Cl" permeation test and alkali aggregate reaction test were carried out at various ages,the influence law of the dosage and type of nanomaterials on concrete Cl-penetration and alkali aggregate reaction was analyzed,and the mechanism of its action was revealed.The test results show that the durability of nano-concrete has been improved in different degrees under the action of Cl-penetration and alkali aggregate reaction.