預(yù)制混凝土早期強度試驗研究
發(fā)布時間：2018-11-24 16:51
【摘要】：隨著我國不斷推廣建筑工業(yè)化和號召資源節(jié)約型、環(huán)境友好型社會的建設(shè)。預(yù)制混凝土行業(yè)逐步成為主導(dǎo)今后混凝土發(fā)展的潮流。在很多工程領(lǐng)域應(yīng)用越來越廣泛(如：市政工程和建筑工程)。但目前人們關(guān)注的主要問題是：生產(chǎn)效益和生產(chǎn)周期,預(yù)制混凝土的早期強度成為當(dāng)前必須解決的關(guān)鍵問題。根據(jù)對國內(nèi)很多預(yù)制混凝土生產(chǎn)廠進(jìn)行的調(diào)查來看,為了提高早期強度、縮短周期、加速模板周轉(zhuǎn),很多廠家在混凝土預(yù)制構(gòu)件生產(chǎn)中普遍采用蒸汽養(yǎng)護(hù)工藝,消耗了大量的煤炭資源,同時產(chǎn)生了大量的溫室氣體。因此免蒸養(yǎng)技術(shù)提高預(yù)制混凝土早期強度勢在必行。本課題針對上述問題從兩方面入手：一是從外加劑入手,試驗研究合成了一種早強型聚羧酸減水劑：二是從石膏入手,研究了四家石膏廠生產(chǎn)的三種無水石膏和四種半水石膏,得到了其對砂漿早后期強度的影響規(guī)律。進(jìn)而確定了一種有利于提高預(yù)制混凝土早期強度的石膏。然后通過逐一試驗和正交試驗驗證兩種方法確定了該石膏在砂漿中的最佳摻量及部分復(fù)配摻合料的摻量。將此石膏及對應(yīng)的最佳摻量用于混凝土正交試驗中,優(yōu)化配制了C40預(yù)制混凝土,發(fā)現(xiàn)早期1-3d強度可提高50%以上,完全試現(xiàn)了早拆模的標(biāo)準(zhǔn)。最后在原理上分析了石膏對預(yù)制混凝土早期強度提高的原因和機理。混凝土中加入適量的石膏可以大大降低熟料中鋁酸三鈣和含鐵相礦物水化速度,從而使水泥水化時間變長,保證其在足夠時間內(nèi)具有可塑性,有利于早期強度的發(fā)展。適量的石膏可以跟水泥中化學(xué)成分反應(yīng)形成適量的鈣礬石,對水泥內(nèi)部孔隙進(jìn)行填充,增加密試程度,形成較強的結(jié)構(gòu)骨架,從而使早期強度得到增強；但在水泥中如果加入過多的石膏,會形成很多具有膨脹性的物質(zhì),使強度降低,因此石膏的摻量有一個最佳比例。對于使用普通硅酸鹽水泥的混凝土,通過本文的研究確定了半水石膏的最佳摻量。在多次試驗的基礎(chǔ)上我們可以斷定當(dāng)水泥換了生產(chǎn)廠家或水泥種類,導(dǎo)致各個組分的含量發(fā)生了變化時,該摻量也就不適用了,所以半水石膏的摻量與水泥的化學(xué)成分及比例有關(guān)。本文的研究還發(fā)現(xiàn),無水石膏的摻量和水泥的組分含量達(dá)到最佳比例時,其早期、后期強度可能會超過半水石膏,這個最佳比例的確定還有待后續(xù)研究。
[Abstract]:Along with our country unceasingly popularizes the construction industrialization and calls for the construction of resource-saving and environment-friendly society. Precast concrete industry has gradually become the leading trend of concrete development in the future. It is more and more widely used in many engineering fields (e.g. municipal engineering and building engineering). But at present, the main problem that people pay attention to is: production benefit and production cycle, the early strength of precast concrete becomes the key problem that must be solved at present. According to the investigation conducted by many prefabricated concrete production plants in China, in order to increase early strength, shorten the period and speed up the turnover of formwork, many manufacturers generally adopt steam curing technology in the production of concrete prefabricated components. It consumes a lot of coal resources and produces a lot of greenhouse gases. Therefore, it is imperative to improve the early strength of precast concrete by steaming-free technique. This subject aims at the above problems from two aspects: first, starting with admixture, a kind of early-strength polycarboxylic acid water-reducing agent is studied; second, starting with gypsum, three kinds of anhydrous gypsum and four kinds of hemihydrate gypsum produced by four gypsum plants are studied. The effect of mortar strength on the early and late stage of mortar strength was obtained. Furthermore, a kind of gypsum which is propitious to improve the early strength of precast concrete is determined. Then the optimum content of gypsum in mortar and the content of partial admixture were determined by one experiment and by orthogonal test. By applying the gypsum and the corresponding optimum amount to the orthogonal test of concrete, the C40 precast concrete was optimized and it was found that the strength of the early stage 1 to 3 d could be increased by more than 50%, and the standard of early demoulding was completely tested. Finally, the reason and mechanism of early strength improvement of prefabricated concrete by gypsum are analyzed in principle. The hydration rate of tricalcium aluminate and iron-bearing minerals in clinker can be greatly reduced by adding proper amount of gypsum in concrete, thus the hydration time of cement becomes longer, and the cement has plasticity in sufficient time, which is beneficial to the development of early strength. Proper amount of gypsum can react with the chemical composition of cement to form appropriate amount of ettringite, which can fill the internal pores of cement, increase the degree of density test, and form a strong structural skeleton, so that the early strength is enhanced. However, if too much gypsum is added to cement, a lot of expansive substances will be formed, and the strength will be reduced, so there is an optimum proportion of gypsum content. For concrete with ordinary Portland cement, the optimum content of gypsum is determined by the research in this paper. On the basis of many experiments, we can conclude that when the cement is changed by the manufacturer or the type of cement, the content of each component changes, and the content of the cement is not suitable. So the content of gypsum hemihydrate is related to the chemical composition and proportion of cement. It is also found that the strength of anhydrous gypsum may exceed that of hemihydrate gypsum in the early stage when the content of anhydrous gypsum and cement content reaches the optimum ratio.
【學(xué)位授予單位】：山東建筑大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：TU528
本文編號：2354399
[Abstract]:Along with our country unceasingly popularizes the construction industrialization and calls for the construction of resource-saving and environment-friendly society. Precast concrete industry has gradually become the leading trend of concrete development in the future. It is more and more widely used in many engineering fields (e.g. municipal engineering and building engineering). But at present, the main problem that people pay attention to is: production benefit and production cycle, the early strength of precast concrete becomes the key problem that must be solved at present. According to the investigation conducted by many prefabricated concrete production plants in China, in order to increase early strength, shorten the period and speed up the turnover of formwork, many manufacturers generally adopt steam curing technology in the production of concrete prefabricated components. It consumes a lot of coal resources and produces a lot of greenhouse gases. Therefore, it is imperative to improve the early strength of precast concrete by steaming-free technique. This subject aims at the above problems from two aspects: first, starting with admixture, a kind of early-strength polycarboxylic acid water-reducing agent is studied; second, starting with gypsum, three kinds of anhydrous gypsum and four kinds of hemihydrate gypsum produced by four gypsum plants are studied. The effect of mortar strength on the early and late stage of mortar strength was obtained. Furthermore, a kind of gypsum which is propitious to improve the early strength of precast concrete is determined. Then the optimum content of gypsum in mortar and the content of partial admixture were determined by one experiment and by orthogonal test. By applying the gypsum and the corresponding optimum amount to the orthogonal test of concrete, the C40 precast concrete was optimized and it was found that the strength of the early stage 1 to 3 d could be increased by more than 50%, and the standard of early demoulding was completely tested. Finally, the reason and mechanism of early strength improvement of prefabricated concrete by gypsum are analyzed in principle. The hydration rate of tricalcium aluminate and iron-bearing minerals in clinker can be greatly reduced by adding proper amount of gypsum in concrete, thus the hydration time of cement becomes longer, and the cement has plasticity in sufficient time, which is beneficial to the development of early strength. Proper amount of gypsum can react with the chemical composition of cement to form appropriate amount of ettringite, which can fill the internal pores of cement, increase the degree of density test, and form a strong structural skeleton, so that the early strength is enhanced. However, if too much gypsum is added to cement, a lot of expansive substances will be formed, and the strength will be reduced, so there is an optimum proportion of gypsum content. For concrete with ordinary Portland cement, the optimum content of gypsum is determined by the research in this paper. On the basis of many experiments, we can conclude that when the cement is changed by the manufacturer or the type of cement, the content of each component changes, and the content of the cement is not suitable. So the content of gypsum hemihydrate is related to the chemical composition and proportion of cement. It is also found that the strength of anhydrous gypsum may exceed that of hemihydrate gypsum in the early stage when the content of anhydrous gypsum and cement content reaches the optimum ratio.
【學(xué)位授予單位】：山東建筑大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：TU528
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相關(guān)期刊論文 前4條
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，本文編號：2354399
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