【摘要】：大流動度混凝土指拌合物坍落度值在160mm以上的混凝土,它是混凝土研究發(fā)展的一個新方向。近年來隨著外加劑和礦物摻合料應(yīng)用研究的發(fā)展,大流動度混凝土在國內(nèi)外的研究取得了很大進展。將大流動度混凝土用于路面工程,可以減輕鋪筑混凝土的勞動強度和工作量、節(jié)省能源、減少噪聲、保護環(huán)境、提高施工進度、增加路面板內(nèi)混凝土的均質(zhì)性。但它的流動性也產(chǎn)生了一些負面作用,如早期收縮開裂現(xiàn)象比較嚴重,導(dǎo)致大流動度混凝土路面實際使用年限達不到設(shè)計年限的要求。因此,研究大流動度混凝土路面的早期開裂機理非常重要。本文首先初步探討了大流動度混凝土路面的裂縫成因及控制措施,然后通過正交試驗,以坍落度、7d、28d抗折、抗壓強度為評價指標,進行配合比設(shè)計,優(yōu)選大流動度路面混凝土配合比設(shè)計參數(shù),試驗表明水膠比是影響大流動度混凝土工作性與抗折強度的關(guān)鍵因素。再根據(jù)所得的配合比以水膠比、砂率以及粉煤灰摻量為影響因素進行了混凝土的早期開裂試驗,試驗數(shù)據(jù)表明隨著粉煤灰摻量的增加,大流動度混凝土單位面積的總開裂面積先減小后增加,在混凝土中摻入一定量粉煤灰能有效減少開裂,隨著砂率的增加,大流動度混凝土的早期開裂逐漸增加,隨著水膠比的增加,大流動度混凝土的早期開裂急劇增加。然后針對引起混凝土早期開裂的本質(zhì)因素即混凝土內(nèi)部的溫度梯度和濕度梯度,系統(tǒng)地分析了混凝土溫度場與濕度場的變化規(guī)律及溫度應(yīng)力和干縮應(yīng)力的數(shù)值計算方法。最后通過有限元分析軟件MIDAS對大流動度混凝土路面板的溫度應(yīng)力與干縮應(yīng)力進行數(shù)值計算,分析其對混凝土早期開裂的影響規(guī)律,并將計算所得的溫度應(yīng)力與干縮應(yīng)力疊加后對大流動度混凝土路面的早期開裂進行風(fēng)險判斷。
[Abstract]:Large fluidity concrete refers to concrete whose slump value is above 160mm, which is a new direction in the research and development of concrete. In recent years, with the development of admixture and mineral admixture, great progress has been made in the research of high fluidity concrete at home and abroad. Using large fluidity concrete in pavement engineering can reduce the labor intensity and workload of paving concrete, save energy, reduce noise, protect environment, improve construction progress and increase the homogeneity of concrete in pavement slab. However, its fluidity also has some negative effects, such as serious early shrinkage and cracking phenomenon, which leads to the fact that the actual service life of high flow concrete pavement is not up to the requirement of design life. Therefore, it is very important to study the early cracking mechanism of high flow concrete pavement. In this paper, the causes and control measures of cracks in high flow concrete pavement are discussed, and then through orthogonal test, the mix ratio is designed with slump, 7d ~ 28d bending resistance and compressive strength as evaluation index. The optimum design parameters of concrete mixture ratio for high fluidity pavement are selected. The test results show that the water-binder ratio is the key factor affecting the workability and flexural strength of high flow concrete. According to the mixture ratio of water and binder, sand ratio and the content of fly ash as the influencing factors, the early cracking test of concrete is carried out. The experimental data show that with the increase of the content of fly ash, The total cracking area of high fluidity concrete decreases first and then increases. Adding a certain amount of fly ash into concrete can effectively reduce the cracking. With the increase of sand ratio, the early cracking of high flow concrete increases gradually. With the increase of water / binder ratio, the early cracking of high fluidity concrete increases sharply. Then the variation law of temperature field and humidity field of concrete and the numerical calculation method of temperature stress and dry shrinkage stress are analyzed systematically in view of the essential factors that cause the early cracking of concrete namely the temperature gradient and humidity gradient inside the concrete. Finally, the temperature stress and dry shrinkage stress of high flow concrete pavement slab are numerically calculated by finite element analysis software MIDAS, and its influence on early cracking of concrete is analyzed. The calculated temperature stress and dry shrinkage stress are superimposed to judge the risk of early cracking of high flow concrete pavement.
【學(xué)位授予單位】：重慶交通大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：U416.216;U418.6

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本文編號：2392822