【摘要】：采用優(yōu)質(zhì)細(xì)石英砂、極低的水膠比和高性能的硅灰等活性混合材制得的活性粉末混凝土具有很高的抗壓抗折強(qiáng)度,極低的孔隙率和超高耐久性。但同時(shí)RPC也表現(xiàn)的更加硬脆,這在工程應(yīng)用中的危害很大。為了提高RPC的抗折強(qiáng)度、斷裂韌性等性能,改善RPC的硬脆特性,通常在RPC中加入鍍銅細(xì)鋼纖維。同時(shí)聚乙烯醇纖維能夠顯著改善普通混凝土彎曲韌性、拉伸變形等性能。本文擬將二者混摻以改善RPC的抗折強(qiáng)度、變形及韌性等性能。本課題主要研究了不同鍍銅細(xì)鋼纖維/PVA纖維混摻方案下RPC試件的抗壓抗折強(qiáng)度、小梁彎曲性能、沖擊韌性、鹽凍性以及微觀形貌分析、顯微硬度等微觀性能,結(jié)果表明:隨著鍍銅細(xì)鋼纖維摻量由0%增加到2.0%的過程中,RPC試件的抗壓抗折強(qiáng)度與彎曲性能均顯著提高。沖擊韌性和抗鹽凍性能隨著鋼纖維摻量的增加表現(xiàn)出先提高后降低的趨勢(shì),在1.5%時(shí)最佳。鋼纖維摻量對(duì)RPC的初裂次數(shù)影響較小,而終裂次數(shù)影響較大,在摻量為1.5%時(shí)終裂次數(shù)最高。鍍銅細(xì)鋼纖維周圍水泥石的微觀結(jié)構(gòu)分布較均勻,鋼纖維的顯微硬度約為水泥石的3.5倍,其與水泥石的界面過渡區(qū)結(jié)構(gòu)致密,在0~30μm內(nèi)存在一個(gè)明顯的強(qiáng)化區(qū),其顯微硬度高于水泥石。當(dāng)鍍銅細(xì)鋼纖維摻量一定時(shí),摻入三種不同規(guī)格的PVA纖維,在PVA纖維摻量由0.5%、1.0%到1.25%增加的過程中,抗折強(qiáng)度均隨摻量的增加而增大,抗壓強(qiáng)度均與單摻鋼纖維組保持一致,小梁彎曲試驗(yàn)峰值均隨摻量的增加而增大。荷載-撓度曲線的下降段也由陡變緩;當(dāng)PVA纖維摻量增加到2.0%時(shí),抗壓抗折強(qiáng)度都有著明顯的降低,小梁彎曲試驗(yàn)峰值荷載、峰值變形明顯下降,下降段較緩。摻入三種PVA纖維均能延緩RPC的初裂,但較細(xì)的PVA-HT-12纖維組與PVA-HT-6纖維組的終裂次數(shù)均明顯降低。較粗的PVA-ECC-12纖維組僅在摻量為1.25%時(shí),初裂、終裂次數(shù)均明顯優(yōu)于單摻鍍銅細(xì)鋼纖維組。隨著鍍銅細(xì)鋼纖維的摻量由0%增加到2.0%的過程中,PVA-HT-12纖維組早期的抗鹽凍性高于單摻鋼纖維組,但后期性能較差。短纖維組的鹽凍性優(yōu)于長纖維組。PVA-ECC-12纖維內(nèi)部的顯微硬度約為水泥石的1/4,其與水泥石的界面過渡區(qū)結(jié)構(gòu)疏松,在0~30μm內(nèi)存在一個(gè)明顯的薄弱區(qū),其顯微硬度約為水泥石的1/2,這與超景深顯微儀所觀測(cè)到在PVA-ECC纖維與水泥石結(jié)合的界面處存在一個(gè)厚度約為30μm的界面過渡區(qū)一致。從綜合性能角度考慮,本文最終給出的最佳混摻方案為:鍍銅細(xì)鋼纖維最佳摻量為1.5%,PVA纖維的最佳摻量為1.25%,其中較粗的PVA-ECC-12纖維的綜合效果最佳。
[Abstract]:The active powder concrete made of high quality fine quartz sand, very low water-binder ratio and high performance silica fume has very high compressive flexural strength, extremely low porosity and ultra-high durability. But at the same time, RPC also shows more hard and brittle, which is a great harm in engineering applications. In order to improve the flexural strength and fracture toughness of RPC and improve the hard and brittle properties of RPC, copper-plated fine steel fibers are usually added to RPC. At the same time, polyvinyl alcohol fiber can significantly improve the flexural toughness, tensile deformation and other properties of ordinary concrete. In this paper, we propose to improve the flexural strength, deformation and toughness of RPC by mixing them. In this paper, the compressive flexural strength, beam bending property, impact toughness, salt freezing property, micro-morphology analysis, microhardness and other micro-properties of RPC specimens under different copper-plated fine steel fiber / PVA fiber mixing schemes were studied. The results show that the compressive flexural strength and bending properties of RPC specimens increase significantly with the increase of the content of copper-plated fine steel fibers from 0% to 2.0%. The impact toughness and salt-freezing resistance of the steel fiber increased first and then decreased with the increase of the content of steel fiber, which was the best when 1.5% of the steel fiber was added. The effect of steel fiber content on the initial crack number of RPC is small, but the final crack number is greater, and the final crack number is the highest when the content of steel fiber is 1.5%. The microhardness of the steel fiber is about 3.5 times of that of the cement stone. The structure of the interface transition zone between the steel fiber and the cement stone is dense, and there is an obvious strengthening zone in the range of 0 ~ 30 渭 m, and the microhardness of the steel fiber is about 3.5 times that of the cement stone. Its microhardness is higher than that of cement paste. When the content of copper plated fine steel fiber is constant, three kinds of PVA fibers of different specifications are added, and the flexural strength increases with the increase of the content of PVA fiber from 0.5%, 1.0% to 1.25%, when the content of the fiber is increased from 0.5%, 1.0% to 1.25%. The compressive strength is consistent with that of single steel fiber group, and the peak value of beam bending test increases with the increase of the content of steel fiber. When the content of PVA fiber increased to 2.0%, the compressive and flexural strength decreased obviously, and the peak load and the peak deformation of the beam bending test decreased obviously, and the descending segment was slower than that of the control group, but the load-deflection curve also decreased steeply, and when the content of the fiber increased to 2.0%, the compressive and flexural strength of the beams decreased obviously. The first crack of RPC was delayed by adding three kinds of PVA fibers, but the final crack times of the finer PVA-HT-12 fiber group and the PVA-HT-6 fiber group decreased obviously. When the content of PVA-ECC-12 fiber was 1.25%, the number of initial crack and final crack was obviously better than that of single copper-coated fine steel fiber group. In the process of increasing the content of copper-coated fine steel fiber from 0% to 2.0%, the salt-freezing resistance of the PVA-HT-12 fiber group was higher than that of the single steel fiber group, but the later performance was poor. The microhardness of the short fiber group is about 1? 4 of that of the cement stone, the structure of the interface transition zone between the short fiber group and the cement stone is loose, and there is an obvious weak area within 0 ~ 30 渭 m of the short fiber group, which is better than the long fiber group. The microhardness of the ECC-12 fiber is about 1% of that of the cement stone. The microhardness is about 1? 2 of that of cement stone, which is consistent with that observed by ultra-depth-of-field microscopy at the interface between PVA-ECC fiber and cement paste with a thickness of about 30 渭 m. From the point of view of comprehensive properties, the optimum mixing scheme given in this paper is as follows: the optimum content of copper-coated fine steel fiber is 1.5%, and the optimum content of PVA-ECC-12 fiber is 1.25%, among which the coarser PVA fiber has the best comprehensive effect.
【學(xué)位授予單位】：哈爾濱工業(yè)大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2016
【分類號(hào)】：TU528
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本文編號(hào)：2457889