| Reactive powder Concrete (RPC as the shortened form) is a kind of high strength, high toughness, low porosity, ultra high strength Concrete,which has very broad application prospects. Developing new mineral admixture technology remains the RPC important research direction. At the same time, exploring the change law of RPC properties under the single factor of erosion environment and multi-factor coupling effect has very important theoretical significance and practical significance to expanding the application field of RPC, moreover, which can provide reference for the revision of national standard. First of all, this thesis focused on researching the influence on the flexural and compression strength, crack resistance of the green environmental protection RPC with the different curing system, varieties of rice husk ash instead of silica fume with different content; Secondly, this thesis Mainly compared the resistance to sulfate erosion and frost resistance of the green environmental protection RPC under single effect of sulfate erosion environment, freeze-thaw environment and the coupled action of freezing and thawing; Finally,based on SEM and EDS, the failure mechanism of RPC after erosion effect was researched in this thesis preliminarily.The main research conclusions are as follows:(1) The low temperature rice husk ash and silica fume ash have the same activity. Not only mixing with low temperature rice husk ash can improve the brittleness of RPC, but also can give full play to the filling effect and ash effect with the conditions of silica fume. The compression strength and flexural strength of RPC, compression ratio and flexural toughness properties improved of varying degrees:when the low temperature rice husk ash and silica fume double were both mixed at the ratio of 33%, compared with the single doped silicon ash group, the compression strength, bending strength of RPC was raised by 17 MPa and 3.5 MPa. respectively, replacing silica fume with the low temperature rice husk ash was verified to be feasible(2) With thermal curing equipment self-designed, the experimental results show that 100℃ hot water curing has a more positive effect,compared with steam curing, to helping the active mineral admixture filling capillary pores of RPC.Meanwhile, improving its microstructure.the growth effect to the concrete compression strength, bending strength is more apparent, and the effect of curing system to the folding strength is less than that to the compression strength.(3) when the specimens were soaked after freezing and thawing cycle time of up to 420 times In the single sulfate erosion environment, the two kinds of RPC have no big change in appearance shape. But,the mass increased both.The mass of environmental protection group was increased more than that of the reference group:the mass of group AS after a 420-cycle increased averagely by 0.022 kg, group BS increased by 0.045 kg; with the increasing of freeze-thaw cycle time, the relative dynamic elastic modulus of two groups increased in the same trend..(4) The black mark on the surface of the respective of group AF and BF almost disappeared, after 420 times of freeze-thaw damage under the action of single freeze-thaw cycle, and the mass loss rate is larger than that under single sulfate erosion environment. This thesis found that a single freeze-thaw damage effect on environmental protection of RPC is more significant than that of reference group:the mass of group BF peaked at 300 cycle times of freeze-thaw, which increased initially by 0.019 kg, and increased by 0.013 kg than that of group AF under the same condition;Due to the osmotic pressure and swelling pressure coexist in freezing and thawing environment, the relative dynamic elastic modulus of specimens were also higher than that of single specimen sulfate erosion environment.(5) Under the sulfate-coupling of freeze-thaw erosion environment, the RPC specimens were damaged by freezing and thawing, coupling with sulfate, the appearance after the damage in 420 times freeze-thaw is more serious than that under single factor environment, the surface of specimens have some losses. But, due to counteracting between the effect of filling of the salt crystals and freeze-thaw damage,which has a calming effect to crystallization damage of freeze-thaw, the relative dynamic elastic modulus increases with the increase of freeze-thaw cycles. Such as,the relative dynamic elastic modulus of group A-SF, group B-SF increased by the maximum of 107.7% and 107.7% respectively, after 420 times of freeze-thaw cycle. SEM, EDS microscopic test results show that the combination of low temperature rice husk ash and silica fume can effectively reduce the consumption of porosity of environmental protection RPC, degrade Ca(OH)2 and produce more C-S-H, which can effectively improve the compactness of matrix, and enhance the sulfate attack resistance and frost resistance. |
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