既有混凝土及構(gòu)件的氯鹽腐蝕模擬試驗(yàn)研究

1、既有混凝土及構(gòu)件的氯鹽腐蝕模擬試驗(yàn)研究        【中文摘要】氯離子腐蝕是影響混凝土結(jié)構(gòu)耐久性不足的重要因素之一。氯離子侵進(jìn)混凝土內(nèi)將引起鋼筋銹蝕,縮短結(jié)構(gòu)工作壽命,并可能在短時(shí)間內(nèi)危害結(jié)構(gòu)的使用安全。本論文以自然氯鹽環(huán)境下的既有混凝土結(jié)構(gòu)為研究背景。取得既有水閘的閘門混凝土芯樣,并測(cè)試分析了閘門混凝土中的氯離子濃度;進(jìn)行了相應(yīng)的室內(nèi)模擬試驗(yàn),研究了模擬混凝土試件的抗氯離子腐蝕的性能及影響因素,并對(duì)比分析了與既有混凝土構(gòu)件中的氯離子擴(kuò)散性能的區(qū)別;設(shè)計(jì)了模擬自然腐蝕環(huán)境因素,進(jìn)行了混凝土構(gòu)件(梁)的室內(nèi)模擬腐蝕

2、試驗(yàn),并測(cè)試了不同腐蝕齡期構(gòu)件的混凝土中的氯離子濃度,分析了荷載作用下混凝土構(gòu)件的氯離子擴(kuò)散性能及特征;初步研究了砂漿保護(hù)層對(duì)氯鹽環(huán)境下混凝土結(jié)構(gòu)抗氯離子腐蝕的效果?；谧匀宦塞}環(huán)境條件下混凝土芯樣中氯離子濃度的測(cè)試分析及室內(nèi)模擬試驗(yàn)研究,本文研究得到的主要結(jié)論如下:1.在干濕循環(huán)感潮環(huán)境條件下,受雙向腐蝕的既有混凝土中的氯離子腐蝕區(qū)域由對(duì)流區(qū)與擴(kuò)散區(qū)組成,雙向均顯現(xiàn)該特點(diǎn)。受雙向腐蝕的既有混凝土擴(kuò)散區(qū)的氯離子腐蝕規(guī)律與Fick第二定律基本吻合。氯離子擴(kuò)散系數(shù)值隨氯離子腐蝕深度的增加而增加,但增加趨勢(shì)逐漸平緩。2.在室內(nèi)試驗(yàn)條件下,模擬的混凝土的水灰比、孔隙率及抗壓強(qiáng)度等與交流電橋法測(cè)定的氯離

3、子擴(kuò)散系數(shù)有較好的線性關(guān)系;結(jié)合既有混凝土芯樣的氯離子濃度測(cè)試數(shù)據(jù),可初步建立考慮暴露時(shí)間、溫度等影響的既有混凝土的氯離子擴(kuò)散系數(shù)的計(jì)算模型。3.在設(shè)計(jì)的試驗(yàn)條件下,受荷鋼筋混凝土構(gòu)件同一滲透深度處的氯離子濃度總體上隨拉應(yīng)力的增加而增加,隨壓應(yīng)力的增加而減小。腐蝕80d的鋼筋混凝土梁純彎段受拉區(qū)的氯離子擴(kuò)散系數(shù)為純剪處的1.5倍左右;純彎段受壓區(qū)的氯離子擴(kuò)散系數(shù)為純剪處的0.5倍左右,為無荷載作用混凝土試塊的0.6倍左右。相同養(yǎng)護(hù)齡期的鋼筋混凝土梁受壓區(qū)混凝土的氯離子擴(kuò)散系數(shù)隨腐蝕時(shí)間的增加而減小。4.混凝土外側(cè)的砂漿保護(hù)層厚度至少達(dá)到5mm以上才能有效的降低混凝土本體中的氯離子濃度。相同腐蝕

4、時(shí)間內(nèi),涂抹的砂漿保護(hù)層的水灰比越小,厚度越大,混凝土本體中侵進(jìn)的氯離子濃度越低。');【Abstract】 Chloride ions erosion is a main influence factor on insufficient durability of concrete structures. Under chloride environment, chloride irons penetrated in concrete will make reinforcement corrosion to shorted structural life, and may endan

5、ger the working safety of structures in shorter time.The background engineering in this * is the existing concrete structures under the natural chloride environment. The core specimen of concrete lock gates are taken, and the chlorine ions concentration in the different depth of concrete cores have

6、been tested and analyzed; some corresponding indoor experiments have been simulated, and the influencing factors on the anti-chlorine erosion performance of the simulating concrete specimen are researched, and chloride ions diffusion performance in the existing concrete and simulated concrete are al

7、so analyzed contrastively. Influence factors of the natural corrosion environment are designed and simulated, and the indoor experiments for erosion simulation of concrete beams have been made, and the chlorine ions concentration in concrete at different erosion time has been measured, the diffusibi

8、lity and characteristic of chloride ions in the concrete beams under load have been analyzed. The protective effect of mortar protective course for anti-chlorine erosion of concrete structures under chloride environment is studied preliminarily.Based on the datum of the chlorine ions concentration o

9、f specimen in the natural environment and indoor simulated experiment, the main studies conclusions in this * are in the following:1. In the condition of dry-wet circulation, the chlorine ions erosion district in the existing concrete under two-way erosion is made up of convection district and diffu

10、sion district, and so is the two-way appearance. The law of chlorine ions erosion in the diffusion district of the existing concrete above fits with the Fick's second law, basically. Diffusion coefficients of chloride ions in the existing concrete are increase with the increase of the chloride i

11、ons erosion depth, but the increasing trend is flat gradually.2. Under the indoor test conditions, there are better linearity relationships between tested chloride diffusion coefficients using the bridge method and the water-cement ratios and porosity and compression strength of tested concrete. Acc

12、ording to the measured datum of chloride ions concentration in the existing specimen and tested chloride diffusion coefficients, the analytical model for diffusion coefficient of chloride ions in the existing specimen can be built preliminarily to consider the influence of the exposed time and tempe

13、rature and so on.3. Under the designed experimental conditions, the chloride ions concentration in concrete of RC beams in loading adds along with increase of the stretching stress, and reduces along with increase of the compressive stress at the same erosion depth, generally. The chloride ions diff

14、usion coefficient in the stretched district of pure bending section is about 1.5 times more than it in the pure shearing district of RC beams after 80d erosion. The chloride ions diffusion coefficient in the compressive district of pure bending section is about 0.5 times less than it in the shearing

15、 point and 0.6 times less than it in the unloading specimen. The chloride ions diffusion coefficients in the compressive district of RC beams decreases with the increase of erosion time in the same curing age.4. The thickness of outer mortar protective course should be not less than 5mm in order to decrease th