【摘要】：多因素耦合作用下混凝土結構耐久性失效問題越來越嚴重,活性粉末混凝土作為一種水泥基復合材料,具有超高的力學性能和優(yōu)異的耐久性能,適用于惡劣環(huán)境下混凝土結構的主體或防護材料。本文針對氯鹽凍融循環(huán)與侵蝕耦合作用下活性粉末混凝土的耐久性展開了研究,分別通過氯離子侵蝕單因素作用試驗、氯鹽凍融循環(huán)與侵蝕耦合作用(以下簡稱耦合作用)試驗、毛細吸入試驗、氯離子含量測定試驗、水中再水化試驗等,測定了耦合作用下活性粉末混凝土性能指標變化規(guī)律,進行了耦合作用下壽命預測,分析了耦合作用下活性粉末混凝土劣化機理。論文首先研究了活性粉末混凝土在氯離子侵蝕以及耦合作用下物理和力學性能的變化規(guī)律。耦合循環(huán)過程中,質量損失率隨著耦合循環(huán)次數(shù)的增加略微增大,相對動彈性模量幾乎不變,抗壓強度的變化分為三個階段:初始快速下降段-穩(wěn)定段-加速下降段;自然浸泡過程中,抗壓強度隨著自然浸泡時間的增加呈現(xiàn)降低的趨勢,可能是再水化的影響。采用質量損失率來評價耦合作用下活性粉末混凝土的耐久性是不科學的,且相對動彈性模量不宜單獨用作評價活性粉末混凝土耐久性的指標�；谧匀唤菀约榜詈涎h(huán)后試樣內氯離子含量測定結果,提出考慮凍融損傷影響的氯離子擴散系數(shù)計算方法,氯離子擴散系數(shù)隨著耦合循環(huán)次數(shù)的增加先減小后增大;分別考慮凍融損傷破壞、氯離子侵蝕破壞、耦合作用破壞三種情況建立壽命預測模型。在此基礎上,基于元胞自動機模型對自然浸泡、凍融循環(huán)條件下氯離子擴散進行模擬,可為復雜環(huán)境下侵蝕介質擴散模擬提供參考。通過活性粉末混凝土毛細吸入試驗,考慮鋼纖維摻量、溶液濃度等因素對溶液吸入量和毛細吸液系數(shù)的影響,分析了自然浸泡和耦合作用后活性粉末混凝土的毛細吸入特性變化。結果表明:活性粉末混凝土的溶液吸入量隨著時間的增加前期增長較快,后期增長緩慢,溶液吸入量在15～180 min和180-540 min兩階段均與t1/2成正比;浸泡720d溶液吸入量略大于未浸泡試件,耦合作用后溶液吸入量顯著降低,可能是再水化的影響。通過水中再水化試驗,分析再水化作用對活性粉末混凝土性能的影響,自然浸泡以及耦合作用過程中發(fā)生了再水化反應,有絮狀、片狀、針棒狀、無定型產(chǎn)物以及鈣礬石類侵蝕產(chǎn)物生成;再水化作用可以對致密的混凝土結構造成損傷,也會在一定程度上修復損傷。在水泥基水化模型的基礎上提出新的再水化模型,模型模擬值與試驗值吻合良好,可以為后續(xù)再水化模型的研究提供參考。在此基礎上,根據(jù)Gibbs-Thomson方程,分析孔徑以及NaCl濃度對孔隙結冰溫度的影響;測定NaCl濃度和溫度對體積結冰膨脹率的影響。根據(jù)上述結果,分析耦合作用下活性粉末混凝土性能變化的原因�；钚苑勰┗炷羶炔拷Y構致密是其在氯鹽凍融循環(huán)與侵蝕耦合作用下具有良好耐久性的主要原因。
[Abstract]:Durability failure of concrete structures under multi-factor coupling is becoming more and more serious. Reactive powder concrete (RPC), as a kind of cement-based composite material, has super-high mechanical properties and excellent durability. It is suitable for the main body or protective materials of concrete structures in harsh environments. The durability of reactive powder concrete (RPC) was studied. The performance index of RPC was determined by chloride ion corrosion single factor test, chloride salt freeze-thaw cycle and corrosion coupling test, capillary inhalation test, chloride ion content determination test and water rehydration test. The degradation mechanism of RPC under coupling action is analyzed. Firstly, the physical and mechanical properties of RPC under chloride ion erosion and coupling action are studied. With a slight increase in the relative dynamic elastic modulus, the change of compressive strength can be divided into three stages: the initial rapid descent stage - stable stage - Accelerated descent stage; the compressive strength decreases with the increase of natural soaking time, which may be the effect of rehydration. The durability of RPC is unscientific and the relative dynamic modulus of elasticity is not suitable to be used solely as an index to evaluate the durability of RPC.Based on the results of chloride ion content in samples after natural immersion and coupling cycling, a calculation method of chloride ion diffusion coefficient considering the effect of freeze-thaw damage and chloride ion diffusion system is proposed. The number decreases first and then increases with the increase of coupling cycles; life prediction models are established for three cases: freeze-thaw damage, chloride ion erosion and coupling damage. On this basis, chloride diffusion under natural immersion and freeze-thaw cycles is simulated based on cellular automata model, which can be used for erosion in complex environments. Based on the capillary inhalation test of reactive powder concrete (RPC), considering the influence of steel fiber content and solution concentration on the capillary inhalation capacity and capillary absorption coefficient, the capillary inhalation characteristics of RPC after natural immersion and coupling action were analyzed. The amount of liquid inhalation increased rapidly in the early stage and slowly in the later stage with the increase of time. The amount of liquid inhalation was proportional to t1/2 in the 15-180 min and 180-540 min stages. The amount of liquid inhalation in 720 days was slightly larger than that in the unsoaked sample, and the amount of liquid inhalation decreased significantly after coupling action, which may be the effect of rehydration. The influence of rehydration on the properties of RPC is that rehydration reactions occur during natural immersion and coupling, such as flocculent, flaky, needle-bar, amorphous products and Ettringite corrosion products; rehydration can damage the compact concrete structure and repair the damage to a certain extent. Based on the cement-based hydration model, a new rehydration model is proposed. The simulated values are in good agreement with the experimental values, which can be used as a reference for the subsequent study of the rehydration model. Based on the above results, the reason for the performance change of RPC under the coupling action is analyzed. The internal structure of RPC is dense, which is the main reason for its good durability under the coupling action of chloride freeze-thaw cycle and erosion.
【學位授予單位】：北京交通大學
【學位級別】：博士
【學位授予年份】：2016
【分類號】：TU528

【參考文獻】

相關期刊論文 前10條

1 姜作杰;;凍融循環(huán)作用下混凝土毛細孔結構的劣化機制[J];華僑大學學報(自然科學版);2015年06期

2 王立成;鮑玖文;李淑紅;;損傷混凝土毛細吸水性能試驗研究和水分分布預測分析[J];大連理工大學學報;2015年06期

3 趙軍;李洪杰;高丹盈;;銹蝕后鋼纖維和鋼纖維混凝土的力學性能[J];建筑材料學報;2015年03期

4 韓松;涂亞秋;安明U，

本文編號：2199713