發(fā)布時間：2018-05-10 17:12

  本文選題：砂漿 + 混凝土��； 參考：《東南大學(xué)》2017年碩士論文

【摘要】：在海洋或者鹽湖中服役的水泥基材料由于內(nèi)外部諸多因素的作用而發(fā)生損傷劣化,材料逐漸喪失服役性能達不到預(yù)定的使用壽命。外部因素主要包括材料所受到的應(yīng)力作用、鹽湖海水中高濃度的侵蝕性離子、浪濺沖刷以及潮汐區(qū)造成的特殊浸泡制度以及一些溫濕度變化等。而內(nèi)部因素主要有水泥基材料的組成、結(jié)構(gòu)以及輔助膠凝材料品種及摻量等。水泥基材料在不同服役環(huán)境中的耐久性一直是工程和學(xué)術(shù)界關(guān)注的熱點。本文主要針對處于海洋潮汐浪濺沖刷區(qū)中服役的水泥基材料,以砂漿和混凝土試件為研究對象,研究彎曲荷載-干濕循環(huán)-復(fù)合鹽溶液耦合作用下水泥基材料的損傷劣化過程。重點研究了水泥基材料在多因素耦合作用下,微結(jié)構(gòu)損傷累積規(guī)律,為多因素耦合作用下混凝土結(jié)構(gòu)使用壽命的預(yù)測提供理論依據(jù)。本文以相對動彈性模量為測試指標,研究了彎曲荷載-干濕循環(huán)-復(fù)合鹽溶液耦合作用下砂漿以及混凝土試件損傷劣化過程。實驗結(jié)果表明:彎曲荷載-干濕循環(huán)-復(fù)合鹽溶液耦合作用下砂漿試件的損傷劣化過程可以分為三段:初始劣化段、性能改善段和性能劣化段。增大彎曲荷載應(yīng)力比、提高硫酸鹽濃度以及加速干濕循環(huán)頻率都會縮短性能改善段并且提前性能劣化段,從而加速了砂漿試件的損傷劣化。提高氯鹽濃度在一定程度上緩解了硫酸鹽侵蝕。長期浸泡下的試件性能不降反升,相對動彈性模量一直保持在1以上。而水膠比的降低以及礦渣粉和粉煤灰等礦物摻合料的摻入提高了砂漿試件的抗侵蝕性能。此外,本文利用X-CT和壓汞法(MIP)測試彎曲荷載-干濕循環(huán)-復(fù)合鹽溶液耦合作用下砂漿試件孔結(jié)構(gòu)變化規(guī)律。利用XRD測試了鹽類侵蝕前后水化產(chǎn)物與腐蝕產(chǎn)物含量變化。利用環(huán)境掃面電鏡(ESEM)觀察了固相形貌及界面過渡區(qū)在侵蝕前后變化。試驗結(jié)果顯示:侵蝕后砂漿試件的受拉區(qū)孔隙率、有害孔、腐蝕產(chǎn)物以及形貌損傷程度明顯高于受壓區(qū)。而且應(yīng)力比的提高、硫酸鹽濃度的提高和干濕循環(huán)頻率的加快都會加塊砂漿試件損傷劣化。氯鹽濃度提高減緩了硫酸鹽對砂漿試件的侵蝕。長期浸泡下砂漿試件的孔隙率不升反降,水化產(chǎn)物和腐蝕產(chǎn)物的填充作用提高了抗侵蝕性能。低水膠比和礦物摻合料的加入降低了孔隙率改善了孔結(jié)構(gòu),很大程度上減緩了鹽溶液對砂漿試件的侵蝕。
[Abstract]:Cement based materials serving in sea or salt lakes are damaged and degraded due to many internal and external factors, and the service performance of the materials is gradually lost to the intended service life. The external factors mainly include the stress of the material, the high concentration of erosive ions in salt lake seawater, the special immersion system caused by the wave splash and the tidal zone, and some changes of temperature and humidity, etc. The internal factors include the composition, structure of cement-based materials and the variety and content of auxiliary cementing materials. The durability of cement-based materials in different service environments has been a hot topic in engineering and academic circles. In this paper, the damage and deterioration process of cement-based materials under the coupling of bending load-dry-wet cycle and composite salt solution is studied by taking mortar and concrete specimen as the research object, aiming at the cement-based materials in the marine tidal wave and splash scouring area. In this paper, the damage accumulation law of cement based materials under multi-factor coupling is studied, which provides a theoretical basis for predicting the service life of concrete structures under multi-factor coupling. Taking the relative dynamic modulus of elasticity as the test index, the damage deterioration process of mortar and concrete specimens under the coupled action of bending load-dry-wet cycle and composite salt solution is studied in this paper. The experimental results show that the damage degradation process of mortar specimens under the coupling of bending load-dry-wet cycle and composite salt solution can be divided into three stages: initial degradation section, performance improvement section and performance degradation section. Increasing the bending load-stress ratio, increasing the sulfate concentration and accelerating the drying and wet cycle frequency can shorten the performance improvement section and advance the performance deterioration section, thus accelerating the damage deterioration of mortar specimens. Increasing chloride concentration alleviates sulfate erosion to some extent. The properties of the specimens soaked for a long period of time have not decreased but increased, and the relative dynamic modulus of elasticity has been kept above 1. The decrease of water-binder ratio and the addition of mineral admixtures such as slag powder and fly ash improve the corrosion resistance of mortar. In addition, the pore structure of mortar specimens under the coupling of bending load-dry-wet cycle and composite salt solution was tested by X-CT and mercury injection method. The content changes of hydration products and corrosion products before and after salt erosion were measured by XRD. ESEM was used to observe the morphology of solid phase and the change of interfacial transition zone before and after erosion. The results show that the tensile porosity, harmful pores, corrosion products and the damage degree of morphology of corroded mortar specimen are obviously higher than those of compressive zone. Moreover, the increase of stress ratio, the increase of sulfate concentration and the acceleration of dry-wet cycle frequency will result in the damage deterioration of mortar specimens. The increase of chloride concentration alleviates the erosion of mortar specimen caused by sulfate. After a long period of immersion, the porosity of mortar samples does not rise or decrease, and the filling of hydration products and corrosion products improves the corrosion resistance. The low water / binder ratio and mineral admixture decrease the porosity and improve the pore structure, and to a great extent reduce the erosion of mortar specimens caused by salt solution.
【學(xué)位授予單位】：東南大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TU528

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