| Green,high performance,sustainable development,super compounding,high strength and performance,and high functional intelligence etc are the main directions of the concrete development.One of the major problems of high-performance concrete is the long durability. With the resource and energy problem more and more conspicuous,the relation between the life process of the high-performance concrete and the resource environment deserves the deep research.Therefore,it is of great practical significance that to research the method and means for improvement of high-performance concrete and to research the mutual action between the high-performance concrete and the environment.Furthermore,the nano technology has permeated to the fields of mechanics, pharmacology,biology,physics,chemistry,material science,mechanology and etc.Its application has been widely developed in the fields of national defense,electronics,chemical industry,light industry,spaceflight & aviation,biology and medicine etc,and it is regarded as the most promising material in the 21st century.The main purpose of this paper covers three aspects:explore and make use of nano silicon dioxide to improve the durability of high-performance concrete and research its mechanism;research the fast prediction method of the anti-freezing durability of high-performance concrete,so as to reduce the experimental period and improve the experimental efficiency;research the environmental harmony and its evaluation method of high-performance concrete,and provide the theoretical foundation and research method for the "green" and sustainable development of high-performance concrete.It mainly researches the influence of nano SiO2 on the physical and mechanical property,resistance against permeation of chlor ion,self-shrinkage property and anti-freezing durability etc of the high-performance concrete,establishes the predictive model for anti-freezing durability of high-performance concrete based upon the BP neural network,and at last researches the evaluation model for environment harmony of the high-performance concrete based upon Fuzzy-AHP.The research result shows that nano SiO2 has no bad influence on the concrete stability; the water consumption for standard consistency of cement paste increases with the increasing of nano SiO2 dosage,and the gradient is large.When the dosage reaches 8%,the water consumption is one time more than the reference one.Because of the unique "surface effect" of the nano SiO2,the initial and final setting time of the cement paste with SiO2 both reduce with the increasing of dosage,and the speed of nano SiO2 hydration is obviously faster than that of the ordinary Portland cement.For the cement with different water-binder ratios (W/B=0.24,W/B=0.29,W/B=0.34),with the increasing of nano SiO2 dosage,to reach the same slump and spreading,more super plasticizer is required;keeping the same dosage of super plasticizer,the concrete working ability will rapidly reduce with the dosage increase of nano SiO2,and the spreading of concrete mixture reduces faster than the slump reducing.When the dosage proportion is less than 3%-6%,with the increasing of dosage,the strength of the paste test pieces in each period are all improved,compared with that of the reference one,much in the early period and little in the late period.For the high-performance concrete with three water-binder ratios(W/B=0.24,W/B=0.29 and W/B=0.34),adding different dosages of nano SiO2 can improve the compression strength of concrete in the early and late periods,and the effect in the early period is more obvious than that in the late period. In the early period,the effect in the 7d period is the most obvious.The concrete with different water-binder ratios,the effect is the most obvious when the dosage of SiO2 is 3%-5%,not obvious at 5%.Adding NS will increas the self-shrinkage stain value of high-performance concrete; when W/B=0.34,the self-shrinkage value of concrete with the NS dosage of 5%in the late period is always higher than that of the reference concrete.The self-shrinkage increment in 28 days is 20×10-6(increasing by 6%-8%) or so.When W/B=0.25,the self-shrinkage values of concrete with NS all increase by 6%-8%in 28 days,compared with that without NS.Adding AEA can also effectively reduce the self-shrinkage of concrete in the early and late periods; when W/B=0.34,after the AEA is added,the self-shrinkage values of concrete with NS dosage of 0%,3%and 5%are reduced by 8%,12%and 15%respectively.For the concrete without NS,the reduction effect of SR on concrete self-shrinkage is not obvious,no matter in the early or late period.For the concrete with NS,adding of SR can effectively reduce the concrete self-shrinkage.When W/B=0.25 and NS dosage=5%,the concrete self-shrinkage value will reduce by 6%or so if adding a proper amount of super retarder;when W/B=0.34 and NS dosage=5%,the concrete self-shrinkage value will reduce by 12%or so if adding a proper amount of super retarder.At each cycle time point before the max.of freezing thaw cycle,the coefficients of anti-freezing durability of concrete with NS are all higher than that without NS.When W/B=0.25,after 1200 freezing thaw cycles,the relative dynamic elastic moduli of the concrete with NS dosage of 0%,3%and 5%are 92.3%,94.3%and 95.6%respectively;When W/B=0.29,after 1200 freezing thaw cycles,the relative dynamic elastic moduli of the concrete with NS dosage of 0%,3%and 5%are 90.3%,91.3%and 92.6%respectively;when W/B=0.34,after 500 freezing thaw cycles,the relative dynamic elastic moduli of the concrete with NS dosage of 0%,3%and 5%are 53.2%,74.3%and 91.3%respectively.Adding AEA has obvious effect on the improving of anti-freezing durability of high-performance concrete with W/B equal to 0.34.For 500 cycles,the relative dynamic elastic moduli of the concrete with NS dosage of 0%,3%and 5%are 53.2%(95.4%),74.3%(96.5%) and 91.3%(98.2%) before(after) adding AEA,increasing by 79%,30%and 8%respectively.Adding NS after adding AEA also improves the anti-freezing property.After 1200 cycles,the relative dynamic elastic moduli of the concrete with NS dosage of 0%,3%and 5%are 90.4%,91.2%and 93.4%respectively.Establish the predictive model for anti-freezing durability of high-performance concrete based upon the BP neural network.The input variables are the percentage of effective paste volume F,average air bubble spacing coefficient s,air content A, paste-air ratio P/A,and air bubble specific surfaceα;the output is DF value.The established 5-10-1 network structure is the optimal model.Adding NS can effectively improve the anti-permeability performance of the high-performance concrete.The electric flux obviously decreases with the increasing of NS dosage.When the water-binder ratios are 0.25,0.29 and 0.34,the electric fluxes of the concrete with 3%NS in the 28 days' period reduce by 9.3%,21.8%and 5.3%%respectively, compared with the reference concrete;and with 5%in the 28 days' period reduce by 11.0%, 23.2%and 15.8%respectively,compared with the reference concrete.When the water-binder ratios are 0.25,0.29 and 0.34,the electric fluxes of the concrete with 3%NS in the 60 days' period reduce by 26.6%,24.0%ad 4.4%respectively,compared with the reference concrete; and with 5%in the 60 days' period reduce by 28.8%,38.3%and 30.0%respectively, compared with the reference concreteBy means of XRD,SEM and mercury penetration test etc,this paper analyzes the action mechanism of NS on concrete from the micro aspect.The microstructure of paste with NS is compacter than that without NS.Adding NS can reduce the content of C-H in the paste,and refine the C-H crystal in large size.Adding NS can obviously reduce the quantity of C-H crystal on the transition interface,and refine the C-H crystal size.As for the concrete without NS,the C-S-H gel at the interface is mainly in the needle-shaped and loose cluster structure. As for the concrete with NS,the C-S-H gel at the interface is mainly in the compact cluster and dense net structure.Adding NS can improve the effect and the physical filling effect through the interface,thus generally improving the micro characteristics of paste or concrete, and enhancing and improving the macro performance of concrete. Based upon the relation between concrete and environment,this paper brings forward the concepts of "life process of concrete" and the "environment compatibility",and systematically discusses the harmony between each phase(concrete material composition, production,moulding process,use and breakage failure) and the environment,starting from the concept of life process of concrete,and puts forward the feasible measures to improve the life process of concrete and environmental friendliness.This paper is the first to bring forward the Fuzzy-AHP method based upon the AHP(analytic hierarchy process) and fuzzy mathematics,and the evaluation model for life process of concrete and environment compatibility,and introduces the application of Fuzzy-AHP in the evaluation of life process of concrete and environment compatibility.
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