【摘要】：活性粉末混凝土具有超高的力學(xué)性能和良好的耐久性能,尤其適用于對(duì)耐久性要求高的結(jié)構(gòu),因此研究活性粉末混凝土多因素耦合作用下的耐久性具有重要的意義。本文對(duì)預(yù)加載活性粉末混凝土在硫酸鹽干濕和凍融循環(huán)耦合作用下的耐久性進(jìn)行了研究,以水泥種類、粉煤灰和礦粉摻量為主要變量,以不同耦合作用次數(shù)下的相對(duì)動(dòng)彈性模量、質(zhì)量損失率、抗壓強(qiáng)度和抗壓強(qiáng)度耐蝕系數(shù)為主要評(píng)價(jià)指標(biāo),結(jié)合掃描電子顯微鏡(SEM)分析活性粉末混凝土微觀形貌的變化,探究活性粉末混凝土在硫酸鹽干濕和凍融循環(huán)耦合作用下的損傷機(jī)理。主要結(jié)論如下： (1)在硫酸鹽干濕和凍融循環(huán)耦合作用下,活性粉末混凝土的耐久性良好。宜優(yōu)先選用抗壓強(qiáng)度和抗壓強(qiáng)度耐蝕系數(shù)作為其耐久性的評(píng)價(jià)指標(biāo),其次是相對(duì)動(dòng)彈性模量,不宜選用質(zhì)量損失率作為其耐久性的評(píng)價(jià),耦合作用過程中質(zhì)量損失率變化很小。 (2)在硫酸鹽干濕和凍融循環(huán)耦合作用下,預(yù)加載活性粉末混凝土的抗侵蝕能力明顯高于高性能混凝土的抗侵蝕能力；粉煤灰替代硅粉能夠提高活性粉末混凝土的抗硫酸鹽干濕和凍融循環(huán)耦合作用的能力；礦粉的摻入能夠改善活性粉末混凝土的耐久性；高抗硫酸鹽水泥活性粉末混凝土的抗硫酸鹽干濕和凍融循環(huán)耦合作用的能力優(yōu)于普通硅酸鹽水泥活性粉末混凝土。 (3)硫酸鹽干濕和凍融循環(huán)耦合作用對(duì)混凝土微觀形貌產(chǎn)生的影響很大。通過SEM-EDS觀察發(fā)現(xiàn)：C50高性能混凝土耦合循環(huán)作用后,Ca(OH)2含量減少,粉煤灰顆粒的火山灰反應(yīng)程度較低,耦合作用后生成了大量AFm晶體及二水石膏晶體等腐蝕產(chǎn)物�；钚苑勰┗炷榴詈献饔煤�,生成了少量AFm晶體、二水石膏晶體,但由于活性粉末混凝土基體本身結(jié)構(gòu)致密未觀察到Ca(OH)2的存在；高抗硫酸鹽活性粉末混凝土耦合循環(huán)后,水化石榴石的生成,提高了混凝土的密實(shí)度,降低了SO42-和Ca2+反應(yīng)的可能性,抑制了膨脹性石膏晶體的生成,從而提高了活性粉末混凝土的耐久性。
[Abstract]:Reactive powder concrete (RPC) has super high mechanical properties and good durability, especially for structures with high durability requirements. Therefore, it is of great significance to study the durability of reactive powder concrete (RPC) under multi-factor coupling. In this paper, the durability of pre-loaded reactive powder concrete under the coupling of sulphate drying and wet and freeze-thaw cycle is studied. The main variables are the type of cement, the amount of fly ash and mineral powder. Taking the relative dynamic modulus of elasticity, mass loss rate, compressive strength and corrosion resistance coefficient of compressive strength and compressive strength as the main evaluation indexes under different coupling action times, the microstructure of reactive powder concrete (RPC) was analyzed by scanning electron microscope (SEM) (SEM). The damage mechanism of reactive powder concrete (RPC) under the coupling of sulphate drying and wet freezing and thawing was investigated. The main conclusions are as follows: (1) under the coupling of sulphate drying and wet freezing and thawing the durability of reactive powder concrete is good. The compressive strength and the corrosion resistance coefficient of compressive strength should be selected as the evaluation index of its durability, and the relative dynamic modulus of elasticity should be followed, and the loss rate of mass should not be chosen as the evaluation of its durability. The mass loss rate changes little during the coupling process. (2) under the coupling of sulphate drying and wet freezing and thawing the corrosion resistance of pre-loaded reactive powder concrete is obviously higher than that of high performance concrete. The substitution of fly ash for silica powder can improve the coupling ability of reactive powder concrete against sulfate dry-wet and freeze-thaw circulation, and the addition of mineral powder can improve the durability of reactive powder concrete. The coupling ability of high resistance cement reactive powder concrete to sulfate drying and freeze-thawing cycles is better than that of ordinary Portland cement reactive powder concrete. (3) the coupling effect of sulfate dry wet and freeze-thaw cycle is better than that of ordinary Portland cement reactive powder concrete. The microstructure of concrete has great influence. By SEM-EDS observation, it was found that the content of Ca (OH) _ 2 decreased and the reaction degree of pozzolanic ash of fly ash particles was lower after the coupling cycling of C _ (50). A large number of corrosion products such as AFm crystals and gypsum dihydrate crystals were formed after coupling action. A small amount of AFm crystal and gypsum dihydrate crystal were formed after the interaction of reactive powder concrete, but the existence of Ca (OH) 2 was not observed due to the dense structure of reactive powder concrete matrix. The formation of hydrated garnet improves the compactness of concrete, reduces the possibility of reaction between so _ 42- and Ca2, inhibits the formation of expansive gypsum crystal, and improves the durability of reactive powder concrete.
【學(xué)位授予單位】：北京交通大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2014
【分類號(hào)】：TU528

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