本文選題：活性粉末混凝土 + 碳納米管��； 參考：《浙江大學(xué)》2016年博士論文

【摘要】：活性粉末混凝土(Reactive Powder Concrete,簡稱RPC)是根據(jù)最緊密堆積原理,采用高致密水泥基均勻體系模型,將直徑為400～600微米的石英砂作為骨料,同時(shí)摻入適量短纖維和活性礦物制備出的具有超高強(qiáng)度、高耐久性、高韌性的水泥基材料。RPC材料以其優(yōu)異的力學(xué)性能在土木建筑、水利、礦山、橋梁以及軍事工程等領(lǐng)域有著廣闊的應(yīng)用前景。本文首先對國內(nèi)外RPC材料基本力學(xué)研究進(jìn)行綜述,發(fā)現(xiàn)工程中常用的RPC材料的強(qiáng)度仍然較低且韌性不足,不能充分發(fā)揮RPC材料的優(yōu)勢。因此,探索一種兼具高強(qiáng)度和高韌性的RPC對有效減輕混凝土結(jié)構(gòu)物的自重、提高結(jié)構(gòu)物的耐久性、降低工程造價(jià)以及推廣RPC材料應(yīng)用具有重要的工程意義。首先,本研究采用表面活性劑、超聲波和離心機(jī)處理可以得到穩(wěn)定達(dá)到1個(gè)月以上的納米材料預(yù)分散液,并將其分散至水泥凈漿中。試驗(yàn)結(jié)果表明水泥基復(fù)合材料的抗壓強(qiáng)度、抗彎強(qiáng)度與納米材料摻量(0.025 wt%～0.2wP/%)有關(guān),0.1 wt%摻量的碳納米管可將水泥基材料的7天和28天抗壓強(qiáng)度提升22%和15%。納米材料摻量較低時(shí),水泥基復(fù)合材料的強(qiáng)度隨著其摻量的提高而提升,且對水泥基材料早期強(qiáng)度提升明顯,而高摻量的納米材料會(huì)降低水泥基材料的性能。斷裂實(shí)驗(yàn)表明石墨烯和碳納米管的加入可以大幅度提高水泥基材料的斷裂能和斷裂韌度。微觀分析表明碳納米管、石墨烯/氧化石墨烯材料可以將水化產(chǎn)物連接在一起,有效減少有害孔隙的數(shù)量,其增強(qiáng)與增韌的機(jī)理主要是晶核效應(yīng)、橋聯(lián)、拔出與填充效應(yīng)。其次,由于RPC材料是由多種膠凝材料組成,本研究根據(jù)國內(nèi)常用普通水泥及其輔助膠凝材料,同時(shí)配合以不同的投料順序和高、低速攪拌方法,得到具有高流動(dòng)度的RPC漿料。本研究同時(shí)探索出高溫干熱養(yǎng)護(hù)增強(qiáng)RPC材料的合理工藝方法,并對比分析了常溫養(yǎng)護(hù)、濕熱養(yǎng)護(hù)和高溫干熱養(yǎng)護(hù)條件下RPC力學(xué)性能發(fā)展規(guī)律的影響,并對RPC水泥水化產(chǎn)物的種類和形態(tài)、材料收縮進(jìn)行了分析,得到了高溫養(yǎng)護(hù)下的增強(qiáng)機(jī)理。再次,以往研究大多通過提高纖維的用量來提升RPC的韌性,但是相比于超高的抗壓強(qiáng)度,RPC材料直接拉伸強(qiáng)度仍然不足10 MPa。過多的增加鋼纖維的用量并不會(huì)提高基體開裂強(qiáng)度和峰值強(qiáng)度,還會(huì)造成RPC材料流動(dòng)性變差等問題。本研究在鋼纖維增強(qiáng)RPC材料的基礎(chǔ)上,利用碳納米管對RPC基體進(jìn)行改性,研究不同種類、摻量的鋼纖維和碳納米管對RPC抗壓、抗折、直接拉伸和四點(diǎn)彎曲等力學(xué)性能的影響,探索二者對水泥基復(fù)合材料的增強(qiáng)增韌機(jī)理。結(jié)果表明碳納米管的加入可以有效提高RPC材料的強(qiáng)度指標(biāo),摻有0.025wPt%碳納米管的RPC材料的抗壓強(qiáng)度和彎曲開裂強(qiáng)度較對照組分別提高了 7.2%和36%,直接拉伸試件的開裂強(qiáng)度和極限強(qiáng)度均提高8%以上。微觀分析表明碳納米管可以有效的在微觀尺度上延緩初始裂紋的產(chǎn)生和發(fā)展,多壁碳納米管在裂縫擴(kuò)張為宏觀裂縫時(shí)逐漸失去作用,轉(zhuǎn)而由橫跨于裂縫之間的鋼纖維來承擔(dān)荷載作用,這兩種纖維可以在材料破壞的不同階段發(fā)揮各自的作用,起到優(yōu)勢互補(bǔ)的阻裂效果。通過合理的配合比和攪拌工藝,RPC材料的抗壓強(qiáng)度和抗折強(qiáng)度可以達(dá)到208 MPa和45 MPa,單軸直接抗拉強(qiáng)度達(dá)到10 MPa以上,采用異形鋼纖維RPC材料的峰值拉伸應(yīng)變可以達(dá)到0.4%以上。最后,研究通過采用SHPB(Split Hopkinson Pressure Bar,霍普金森壓桿)試驗(yàn)裝置對RPC材料進(jìn)行了沖擊動(dòng)力學(xué)試驗(yàn),利用高速相機(jī)與數(shù)據(jù)同步采集系統(tǒng)得到了試樣動(dòng)態(tài)劈裂應(yīng)力時(shí)程曲線和破壞形貌,并分析了碳納米管的摻量和不同種類的鋼纖維對RPC基體的增強(qiáng)增韌效果。試驗(yàn)表明碳納米管的加入可以提升RPC試件的動(dòng)態(tài)劈裂強(qiáng)度和耗能效果,在較低打擊氣壓下碳納米管的增強(qiáng)效果顯著。隨著碳納米管摻量的增多,其增強(qiáng)效果逐漸減弱。RPC中的鋼纖維在沖擊劈裂荷載作用下存在明顯的橋聯(lián)阻裂作用,可有效提高基體高速變形下的抗拉伸損傷能力。長直鋼纖維RPC動(dòng)態(tài)劈拉強(qiáng)度可以達(dá)到35 MPa以上,較基體提高了 26.1%,且試件沖擊荷載作用下基本能夠保持完整�；w與鋼纖維之間的粘結(jié)性狀和剪切強(qiáng)度是控制劈裂破壞的主要因素,而非鋼纖維本身抗拉強(qiáng)度。試驗(yàn)并采用DIC方法計(jì)算得到了動(dòng)態(tài)變形場并驗(yàn)證了巴西圓盤試驗(yàn)的有效性,結(jié)果表明裂縫的開裂時(shí)間約為峰值荷載前40μs,動(dòng)態(tài)加載下Y方向峰值應(yīng)變達(dá)到1%以上,碳納米管的加入可以提高材料的強(qiáng)度和耗能能力。
[Abstract]:Reactive Powder Concrete (RPC) is a cement-based material with high strength, high durability and high toughness by adding a high compact cementitious homogeneous system model and using quartz sand with a diameter of 400~600 microns as aggregate, and adding a proper amount of short fiber and active minerals to the aggregate, according to the most compact packing principle. With its excellent mechanical properties, C has a broad application prospect in the fields of civil engineering, water conservancy, mine, bridge and military engineering. This paper first summarizes the basic mechanics research of RPC materials at home and abroad, and finds that the strength of the commonly used RPC materials in the engineering is still low and the toughness is insufficient, and the advantages of the RPC materials can not be fully exploited. Therefore, it is important to explore a kind of RPC with high strength and high toughness, which can effectively reduce the weight of the concrete structure, improve the durability of the structure, reduce the cost of the project and popularize the application of RPC material. First, this study can achieve more than 1 months by using surfactants, ultrasonic and centrifuge treatment. The experimental results show that the compressive strength of the cement-based composites is related to the nano material content (0.025 wt% ~ 0.2wP/%), and the 0.1 wt% content of carbon nanotubes can increase the compressive strength of the cement based materials at 7 and 28 days by 22% and lower the content of the 15%. nanomaterials. The strength of the clay based composites is enhanced with the increase of its content, and the early strength of the cement-based material is enhanced obviously. The nano materials with high content will reduce the properties of the cement-based materials. The fracture experiments show that the addition of graphene and carbon nanotubes can greatly improve the fracture energy and fracture toughness of the cement-based materials. Carbon nanotubes, graphene / graphene oxide materials can connect the hydrated products together and effectively reduce the number of harmful pores. The mechanism of strengthening and toughening is mainly the effect of nucleation, bridging, pulling and filling. Secondly, the RPC material is made up of a variety of cementitious materials. This study is based on common cement and its auxiliary in common use in China. At the same time, the RPC slurry with high fluidity was obtained with different feeding order and high low speed stirring method. The reasonable process method of strengthening RPC material was explored at the same time, and the development law of mechanical properties of RPC under the condition of normal temperature curing, wet and hot curing and high temperature dry and hot curing was compared and analyzed. In addition, the types and forms of RPC cement hydration products and the shrinkage of the material are analyzed, and the strengthening mechanism under high temperature curing is obtained. Again, most of the previous studies have improved the toughness of RPC by increasing the amount of fiber, but the direct tensile strength of the RPC material is still less than 10 MPa. to increase the steel fiber by comparing with the ultra high compressive strength. The amount of vitamin D does not increase the crack strength and peak strength of the matrix, but also causes the poor fluidity of the RPC material. On the basis of the steel fiber reinforced RPC material, the carbon nanotube is used to modify the RPC matrix, and the different kinds of steel fiber and carbon nanometers are used to study the compression, bending, direct stretching and four point bending of RPC. The strengthening and toughening mechanism of the two kinds of cement based composites is explored by the influence of the mechanical properties. The results show that the addition of carbon nanotubes can effectively improve the strength of the RPC materials. The compressive strength and the bending cracking strength of the RPC materials with 0.025wPt% carbon nanotubes are improved by 7.2% and 36% compared with the control components. The fracture strength and ultimate strength are increased by more than 8%. Microanalysis shows that the carbon nanotubes can effectively delay the formation and development of the initial cracks at the micro scale. The multi wall carbon nanotubes gradually lose their function when the cracks expand into macro cracks, and then take the loading action of the steel fibers that cross the cracks. These two fibers can be used. The compressive strength and flexural strength of RPC material can reach 208 MPa and 45 MPa through reasonable mix ratio and stirring process, and the tensile strength of the uniaxial direct tensile strength reaches more than 10 MPa, and the peak tensile strain of the hetero steel fiber RPC material can reach to the peak tensile strain. To more than 0.4%. Finally, the impact dynamic test of RPC material was carried out by using SHPB (Split Hopkinson Pressure Bar, Hopkinson pressure bar) test device. The dynamic splitting stress time history curve and broken morphology were obtained by the high-speed camera and the data synchronous acquisition system, and the content and difference of the carbon nanotube were analyzed. The strengthening and toughening effect of the steel fiber on the RPC matrix shows that the addition of carbon nanotubes can enhance the dynamic splitting strength and energy dissipation effect of the RPC specimen. The enhancement effect of the carbon nanotubes is remarkable under the lower barometric pressure. With the increase of the amount of carbon nanotubes, the enhancement effect gradually reduces the impact splitting load of the steel fiber in the.RPC. The tensile strength of the long straight steel fiber RPC can reach more than 35 MPa and 26.1% more than that of the matrix. The bond property and shear strength between the base and the steel fiber can be maintained completely under the impact load of the specimen. It is the main factor controlling splitting failure, not the tensile strength of the steel fiber itself. The dynamic deformation field is calculated by the DIC method and the validity of the Brazil disc test is verified. The results show that the cracking time of the crack is about 40 s before the peak load, the peak strain of Y is over 1% under dynamic loading, and the addition of carbon nanotubes is added. It can improve the strength and energy dissipation of the material.
【學(xué)位授予單位】：浙江大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2016
【分類號】：TU528

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本文編號：1990504