【摘要】：對高強混凝土早齡期拉伸徐變特性的研究,能夠為服役期高強混凝土的高精度應(yīng)力解析及開裂預(yù)測提供重要參數(shù)。本研究應(yīng)用團(tuán)隊自行設(shè)計的早齡期拉伸基本徐變實驗方法,首先評價了摻合料高強混凝土的基本力學(xué)性能及自收縮特性,然后系統(tǒng)性地研究了恒定應(yīng)力作用下加載齡期、應(yīng)力強度比及摻合料種類對高強混凝土早齡期拉伸徐變的影響,進(jìn)一步地研究了變應(yīng)力作用下高強混凝土的早齡期拉伸基本徐變特性。本研究的主要結(jié)論包括:(1)各摻合料高強混凝土的早齡期彈性模量發(fā)展速率明顯大于劈裂抗拉強度和抗壓強度的發(fā)展速率。(2)粉煤灰抑制混凝土自收縮作用明顯;而礦渣促進(jìn)自收縮作用則非常明顯;復(fù)摻組兼具了粉煤灰與礦渣的特點,自收縮的發(fā)展速率介于兩者之間,且與基準(zhǔn)組較為接近。(3)恒定應(yīng)力作用下,加載齡期對于摻合料高強混凝土拉伸徐變的影響主要集中在3 d前,尤其是1 d和2 d齡期加載的混凝土比徐變值特別大。隨著加載齡期的推移,各摻合料高強混凝土在不同應(yīng)力強度比下的非線性徐變特征逐漸變成線性徐變特征。粉煤灰組只在1 d加載齡期的各應(yīng)力強度比時表現(xiàn)對拉伸基本徐變明顯地促進(jìn)作用;礦渣組明顯的抑制作用也主要表現(xiàn)在1 d加載齡期的各應(yīng)力強度比時及2 d加載齡期0.2應(yīng)力強度比情況下;復(fù)摻組在2 d加載齡期前對拉伸徐變總體表現(xiàn)為微弱的促進(jìn)作用。(4)變應(yīng)力作用下,粉煤灰組對拉伸基本徐變表現(xiàn)出促進(jìn)作用;礦渣組明顯地抑制拉伸基本徐變;復(fù)摻組的拉伸基本徐變與基準(zhǔn)組較為接近。復(fù)摻組混凝土在變應(yīng)力與恒定應(yīng)力作用下的基本徐變差值最大,粉煤灰組次之,再其次是礦渣組,基準(zhǔn)組的基本徐變差值最小。(5)變應(yīng)力作用下的拉伸徐變實驗同樣可以用來判斷混凝土早齡期是否具有線性徐變特征,且與恒定應(yīng)力下的結(jié)論基本一致。
[Abstract]:The study of tensile creep characteristics of high strength concrete at early age can provide important parameters for high precision stress analysis and crack prediction of high strength concrete in service period. In this study, the basic mechanical properties and autogenous shrinkage properties of high strength concrete with admixtures were evaluated by using the basic creep test method of early age tension designed by the team, and then the loading age under constant stress was systematically studied. The effect of stress intensity ratio and admixtures on tensile creep of high strength concrete at early age is studied. The basic creep behavior of high strength concrete at early age is further studied. The main conclusions of this study are as follows: (1) the development rate of early age elastic modulus of high strength concrete with different admixtures is obviously higher than that of splitting tensile strength and compressive strength. (2) the effect of fly ash on self-shrinkage of concrete is obvious; The effect of slag on self-shrinkage is very obvious. The compound admixture group has the characteristics of fly ash and slag, and the development rate of autogenous shrinkage is between the two groups, and is close to that of the reference group. (3) under constant stress, The effect of loading age on tensile creep of high strength concrete with admixture is mainly before 3 days, especially the concrete loaded at 1 d and 2 d is more than creep value. With the development of loading age, the nonlinear creep characteristics of high strength concrete with various admixtures at different stress intensity ratios gradually become linear creep characteristics. In the fly ash group, the tensile creep was obviously promoted by the stress intensity ratio of 1 day loading period. The obvious inhibition effect of slag group was mainly under the stress intensity ratio of 1 day loading age and 0.2 stress intensity ratio of 2 days loading age. (4) under the action of changing stress, the fly ash group can promote the basic tensile creep, while the slag group obviously inhibits the tensile creep. The tensile creep of the compound group is close to that of the reference group. Under the action of variable stress and constant stress, the difference of basic creep of concrete with compound admixture is the largest, followed by fly ash group and slag group. (5) tensile creep test under variable stress can also be used to judge whether the early age of concrete has linear creep characteristics, and it is basically consistent with the conclusion under constant stress.
【學(xué)位授予單位】：浙江工業(yè)大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TU528.31

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