本文選題：預濕　切入點：輕骨料混凝土　出處：《內(nèi)蒙古科技大學》2015年碩士論文　論文類型：學位論文

【摘要】：輕骨料混凝土作為一種新型建筑材料，具有輕質(zhì)、高耐久性、經(jīng)濟性突出等諸多優(yōu)點，然而它存在的一些缺陷：彈性模量小、易產(chǎn)生脆性破壞、工作性與可泵送性難于控制等，嚴重制約著輕骨料混凝土在土木工程中廣泛應用�，F(xiàn)有研究表明摻入適量塑鋼纖維對輕骨料混凝土的抗折、抗裂及韌性等性能均有不同程度的改善作用。目前工程中普遍通過對陶粒預濕處理1h的方式來改善輕骨料混凝土工作性能，而陶粒飽水狀態(tài)還會對輕骨料混凝土的強度以及耐久性等產(chǎn)生一定影響。因此需要在綜合考慮輕骨料混凝土各方面宏觀性能的基礎上，來確定陶粒的合理預濕時間。 本文選用兩種高強陶粒：粉煤灰陶粒和頁巖陶粒，分別在四種不同預濕時間下研究陶粒飽水狀態(tài)對輕骨料混凝土宏觀上工作性、強度、抗凍性以及微觀上輕骨料－漿體界面過渡區(qū)等影響規(guī)律，據(jù)此來確定陶粒最佳預濕時間，研究結果表明： 隨著輕骨料吸水率增加，混凝土坍落度經(jīng)時損失呈減小趨勢，尤其在加壓預濕處理情況下?lián)p失數(shù)值最小，表現(xiàn)出較好工作性。塑鋼纖維的摻入使輕骨料混凝土受壓破壞形態(tài)具有一定塑性。7d、14d時，混凝土強度隨著陶粒吸水率增加而減小，并且各組試件強度相差較大。但28d、56d時，混凝土強度與陶粒飽水狀態(tài)關系不大，而主要與輕骨料自身強度有關。輕骨料混凝土的抗凍性隨著陶粒吸水率提高而降低，常壓預濕處理的陶粒其混凝土抗凍等級大于F300，而加壓預濕處理的陶粒其混凝土抗凍等級則沒能達到F300，即陶粒加壓預濕時混凝土抗凍性嚴重被削弱。 粉煤灰陶粒使用前常壓預濕1h即可。而頁巖陶粒預濕時間可以根據(jù)需求而改變：當注重抗凍性時，常壓預濕0.25h～3h；當對工作性要求較高時，，常壓預濕3h～6h。 加壓預濕處理的陶粒其混凝土3d時界面過渡區(qū)中存在大量Ca(OH)2晶體，而常壓預濕處理情況下很少發(fā)現(xiàn)。7d時輕骨料－水泥漿體界面過渡區(qū)成為了一個較為密實的整體。28d時常壓預濕處理的陶粒其混凝土界面過渡區(qū)較為平整、密實，整體性強；而加壓預處理的陶粒其混凝土界面區(qū)結構相對多孔、疏松、整體性較差。
[Abstract]:As a new type of building material, lightweight aggregate concrete has many advantages, such as light weight, high durability, outstanding economy and so on. However, it has some defects, such as small elastic modulus, easy to produce brittle failure, difficult to control workability and pump ability, etc. The extensive application of lightweight aggregate concrete in civil engineering is seriously restricted. Existing studies show that appropriate amount of plasticized steel fiber can resist the bending of lightweight aggregate concrete. The properties of crack resistance and toughness have been improved to some extent. At present, the work performance of lightweight aggregate concrete is generally improved by pre-wetting ceramsite for 1 hour. The saturated state of ceramsite will also have a certain effect on the strength and durability of lightweight aggregate concrete. Therefore, it is necessary to determine the reasonable prewetting time of ceramic particle on the basis of considering all aspects of macroscopic properties of lightweight aggregate concrete. In this paper, two kinds of high strength ceramsite, fly ash ceramsite and shale ceramsite, were used to study the macroscopic workability and strength of lightweight aggregate concrete under four different prewetting times. According to the influence of freezing resistance and transition zone between lightweight aggregate and slurry on microstructure, the optimum prewetting time of ceramsite is determined. The results show that:. With the increase of water absorption of lightweight aggregate, the slump loss of concrete decreases, especially in the case of pressure-pre-wetting treatment. The strength of the concrete decreases with the increase of the water absorption rate of ceramsite, and the strength of the specimens varies greatly with the increase of the water absorption rate of ceramsite, but at 28 days or 56 days, the strength of the concrete decreases with the increase of the water absorption rate of ceramsite, but at 28 days or 56 days, the strength of the concrete decreases with the increase of the water absorption rate of ceramsite. The strength of concrete is not related to the saturated state of ceramsite, but mainly to the strength of lightweight aggregate. The frost resistance grade of concrete treated by atmospheric prewetting treatment is greater than that of F300, but the frost resistance grade of concrete treated by pressurized prewetting treatment does not reach F300, that is to say, the frost resistance of concrete is seriously weakened when ceramsite is prewetted under pressure. The prehumidification time of shale ceramsite can be changed according to the demand: when it pays attention to frost resistance, it is 0.25h / h for 3 h, and 3h / h when the requirement of workability is higher, while the prewetting time of shale pellet can be changed according to the demand before using fly ash ceramsite at atmospheric pressure for 1h. The prehumidification time of shale ceramsite can be changed according to the demand. There are a large number of Ca(OH)2 crystals in the transition zone of concrete interface after 3 days of pressure-pre-wetting treatment. However, under the condition of atmospheric prewetting treatment, it is seldom found that the transition zone between lightweight aggregate and cement paste becomes a relatively dense interfacial transition zone between lightweight aggregate and cement paste under normal pressure prewetting treatment at 0.28 d. The transition zone of concrete interface is relatively smooth, dense and strong integrity. However, the structure of concrete interface is relatively porous, loose and poor integrity.
【學位授予單位】：內(nèi)蒙古科技大學
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：TU528

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