本文關(guān)鍵詞： 水泥基材料 聚乙烯醇纖維 碳納米管 強度 變形　出處：《重慶大學(xué)》2014年碩士論文　論文類型：學(xué)位論文

【摘要】：眾所周知，纖維增強技術(shù)是提高混凝土韌性，減少開裂風(fēng)險的重要技術(shù)手段。在此基礎(chǔ)上，美國學(xué)者Victor Li通過微觀力學(xué)的優(yōu)化，形成一種水泥石基體對纖維的握裹力承擔(dān)的纖維拉力略大于尖端擴展力的理想狀態(tài)，從而研制出具有應(yīng)變硬化性能特征的水泥基材料-ECC（Engineered Cementitious Composite），這一材料及其制備方法在近年來日益引起了國內(nèi)學(xué)者的研究興趣。目前，國內(nèi)研制的ECC的強度和極限變形能力整體較低，還有較大的提升空間。 為了獲得整體強度較高，極限變形能力較好的纖維增強水泥基材料，本論文在原有ECC配制技術(shù)基礎(chǔ)上，進一步采用碳納米管從納米尺度增強水泥石基體的強度和變形能力，制備碳納米管與PVA纖維復(fù)合增強的水泥基材料。通過改變加料方式、改變減水劑種類、改變水灰比、改變纖維摻量、碳納米管增強基體等方式，以抗折、抗壓與抗彎性能為主要考察指標(biāo)，研究了水灰比、纖維摻量等對碳納米管與PVA纖維復(fù)合增強水泥基材料性能的影響規(guī)律。 通過研究碳納米管的摻量對其增強效果的影響，發(fā)現(xiàn)摻量越高，增強效果越顯著。與不摻碳納米管的基準(zhǔn)組相比，摻1.5‰碳納米管的水泥基材料的28天抗折強度增加15%。碳納米管的增強效果受其分散程度的影響。在通過研究碳納米管的分散后發(fā)現(xiàn)，采用超聲波分散對于碳納米管的分散要好于其他類型的機械分散，外加劑對于碳納米管在溶液中分散起到穩(wěn)定作用。 通過改變聚乙烯醇纖維摻量和碳納米管摻量、進行了雙因素正交試驗，經(jīng)過實驗發(fā)現(xiàn)，對于同等纖維摻量下，碳納米管摻量的增加對于抗折強度具有一定的提高作用，抗壓強度變化較小。兩種因素相比，聚乙烯醇纖維摻量對于抗折強度與抗壓強度的極限增強效果要大于碳納米管。 通過研究加料順序的影響，發(fā)現(xiàn)纖維的加入時間對于拌合物的工作性能參數(shù)Γ2影響大，宜采用先摻法，盡管此種方法易產(chǎn)生揚塵。而外加劑的加入時間對于拌合物的工作性能參數(shù)Γ2影響較小，建議采用同摻法或后摻法，因為同摻法或后摻法更加方便。 通過研究外加劑種類的影響，發(fā)現(xiàn)采用不同減水劑其最佳摻量不盡相同，聚羧酸高效減水劑為1%，，萘系高效減水劑為1.5%。聚羧酸高效減水劑比萘系高效減水劑更易產(chǎn)生引氣現(xiàn)象，導(dǎo)致試件內(nèi)部產(chǎn)生較多氣孔，因此，萘系高效減水劑達到的最佳性能優(yōu)于聚羧酸高效減水劑，水泥基材料性能也更穩(wěn)定。 通過研究水灰比的影響發(fā)現(xiàn)，水灰比對拌合物工作性能和強度影響顯著。水灰比較低時，拌合物過干稠，工作性能不良，成型不密實，強度低；水灰比較高時，拌合物則輕微泌水，成型后孔隙多，強度也低。只有一定范圍的水灰比才能獲得拌合物工作性能良好，強度較高的水泥基材料。結(jié)合水灰比對拌合物工作性能和3d、7d、28d抗折強度與抗壓強度的影響的試驗結(jié)果，確定水灰比宜控制在0.3-0.4之間。 通過研究各組成成分摻量的影響，發(fā)現(xiàn)聚乙烯醇纖維摻量較低時，隨著摻量的增加，水泥基材料的強度不斷提高，而工作性能變化不明顯。但纖維摻量大于2.5%后，拌合物工作性能和硬化體力學(xué)性能明顯降低，將硬化體橫斷面折斷后發(fā)現(xiàn)此時纖維產(chǎn)生了明顯的團聚現(xiàn)象，纖維增強效率明顯降低。 試驗測定，在水灰比為0.4，萘系高效減水劑摻量為2%，聚乙烯醇纖維先摻，摻量為2%，碳納米管采用超聲波分散，摻量為1.5‰時，其28天抗壓強度為52MPa，三點抗彎強度（抗折強度）為14MPa，四點抗彎強度為8.2MPa，四點抗彎對應(yīng)的最大位移為20mm。
[Abstract]:As everyone knows, the fiber reinforced technology is to improve the toughness of concrete, an important technical means to reduce the cracking risk. On this basis, the American scholar Victor Li by optimizing the micro mechanics, the formation of the ideal state of a cement matrix of fiber fiber tensile grip wrapped force for slightly larger than the tip extension force, in order to develop cement based materials -ECC with the characteristics of strain hardening (Engineered Cementitious Composite), this material and its preparation method in recent years has caused the domestic scholar's research interest. At present, the domestic development of ultimate strength and deformation capacity of ECC is low, there is a large room for improvement.
In order to obtain high overall strength, good ability limit deformation of fiber reinforced cementitious composite, this paper based on the original ECC preparation technology, the carbon nanotube reinforced cement matrix strength and deformation ability from the nano scale preparation of carbon nanotubes and PVA composite reinforced fiber cement base material. By changing the feeding mode, change the effect of different water reducers, changing the water cement ratio, change the fiber content, the matrix mode of carbon nanotubes reinforced, flexural, compressive and flexural performance as the main indexes, the effects of water cement ratio, fiber content on carbon nanotubes and PVA composite reinforced influence the properties of cement-based materials.
Enhancement effect to the content of carbon nanotubes, found that the content is higher, the enhancement effect is more significant. Compared with the reference group with carbon nanotubes, cement-based materials doped with 1.5 carbon nanotubes% of the 28 day flexural strength increased 15%. carbon nanotubes by the dispersion degree of influence in through the study on the dispersion of carbon nanotubes found by ultrasonic dispersion in dispersion of carbon nanotubes is better than other types of mechanical dispersion, stable to additive effects on carbon nanotubes dispersed in solution.
By changing the content of PVA fiber and carbon nanotubes content, the double factor orthogonal experiment, it is found that for the same fiber dosage, increase the carbon nanotube content has a certain improving effect on the flexural strength, compressive strength changes little. Two factors than PVA fiber dosage for the ultimate the flexural strength and compressive strength of the reinforcing effect than carbon nanotubes.
By studying the effects of feeding order, found that fiber adding time performance parameters for the gamma mixture of 2 high impact, should adopt the first mixing method, although this method is easy to produce dust. The performance parameters for the gamma mixture adding time while agent 2 has little effect, suggestions by or after mixing with mixing method because, after mixing with mixing method or method is more convenient.
By studying the effects of different types of additives, find the optimal dosage of water reducer is not the same, polycarboxylate superplasticizer is 1%, naphthalene superplasticizer 1.5%. polycarboxylate superplasticizer than naphthalene superplasticizer are more susceptible to air entraining phenomenon, resulting in thespecimens produced more holes, so the best performance is better than naphthalene reducing agent of polycarboxylate superplasticizer and cement base material performance is more stable.
By studying the influence of water cement ratio, affect the performance and strength of mixture working water cement ratio significantly. The water cement ratio is low, the mixture is too dry and thick, bad performance, forming dense, low strength; water cement ratio is high, the mixture is slight bleeding, after forming porous, low strength. Only a certain range of the ratio of water to cement mixture can obtain good work performance, high strength cement-based materials. Combined with the performance and 3D mixture operating water cement ratio of 7D, the effect of test results of 28d flexural strength and compressive strength, determine the water cement ratio should be controlled between 0.3-0.4.
By studying the effects of each component content, found the content of PVA fiber is low, with the increase in volume, the strength of the cement base material continues to improve, and work performance does not change significantly. But the fiber content is greater than 2.5%, the mixture performance and strength of hardening can significantly reduce the broken, hardening after the time found that the body cross section fibers produced obvious agglomeration and fiber reinforced efficiency is significantly reduced.
In the experiment, the water cement ratio is 0.4, naphthalene superplasticizer is 2%, polyvinyl alcohol fiber first doped, doped with 2% carbon nanotubes by ultrasonic dispersion, adding amount of 1.5 per thousand, the 28 days compressive strength of 52MPa, three point bending strength (bending strength) is 14MPa. Four point bending strength is 8.2MPa, the maximum displacement of four point bending corresponding to 20mm.

【學(xué)位授予單位】：重慶大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2014
【分類號】：TU528

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