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機制砂再生混凝土微觀結構及二軸應力狀態(tài)下受壓力學性能研究

發(fā)布時間:2018-05-09 20:49

  本文選題:機制砂 + 再生混凝土; 參考:《廣西大學》2017年碩士論文


【摘要】:由于天然砂具有短期內(nèi)不可再生的性質(zhì),混凝土用砂尋求可替代資源是不可避免的趨勢,機制砂也就成為最佳的選擇。另一方面,日益增多的廢棄混凝土也將成為城市的一大公害。將機制砂與再生粗骨料有機結合在一起配制成機制砂再生混凝土不僅能解決天然資源的匱乏問題,對環(huán)境保護也起到積極的作用,符合可持續(xù)發(fā)展的科學理念。本文總共制作了 190個不同石粉含量(0%5%、10%、15%)和不同再生粗骨料取代率(0%、33%、66%、100%)的C35標準立方體混凝土試塊,分別對其微觀結構、劈裂抗拉強度、單軸及二軸受壓應力狀態(tài)下的力學性能進行研究。主要研究工作如下:一、對不同石粉含量以及不同再生粗骨料取代率的機制砂再生混凝土進行劈裂抗拉試驗。結果表明機制砂再生混凝土最優(yōu)石粉含量為10%;低石粉含量(0%、5%)的情況下,再生粗骨料取代率為100%時,機制砂混凝土劈裂抗拉強度最低,而高石粉含量(10%、15%)的機制砂再生混凝土及天然砂再生混凝土劈裂抗拉強度在再生粗骨料取代率為66%時最低。二、通過掃描電鏡對機制砂再生混凝土微觀結構進行研究。分析結果表明石粉可以促進水泥水化反應,而且石粉含量的多少影響水化產(chǎn)物的數(shù)量以及晶體形態(tài)。當石粉含量為10%時,混凝土達到最佳堆積密實狀態(tài),水化產(chǎn)物能很好的填充混凝土內(nèi)部孔洞,骨料砂漿緊密粘結,因此力學性能最好。同時石粉具有填充的作用,使砂漿更加密實。對界面過渡區(qū)進行對比分析,機制砂再生混凝土三個界面過渡區(qū)強度大小排序為舊骨料與舊砂漿界面過渡區(qū)新舊砂漿界面過渡區(qū)新骨料新砂漿界面過渡區(qū)。三、對機制砂再生混凝土進行單軸及雙軸受壓力學性能試驗,觀測分析了其破壞過程以及破壞形態(tài)。單軸壓狀態(tài)下的混凝土破壞形態(tài)為柱狀破壞,雙軸壓狀態(tài)下的破壞形態(tài)基本為層片狀劈裂破壞,只是由于應變比的不同及采用的骨料不同導致破壞時裂縫的傾斜角度以及層片狀破壞的細密程度有所差異。四、二軸受壓應力狀態(tài)下的機制砂再生混凝土強度整體上比單軸應力狀態(tài)下抗壓強度高,但是提高倍數(shù)略有差別,提高值在1.051~2.142倍之間。二軸壓應力狀態(tài)下最大強度與采用的骨料類型與應變比有關,采用天然砂作為細骨料的混凝土,其最大值均出現(xiàn)在應變比為0.5,而對于機制砂普通混凝土與不含石粉機制砂再生混凝土二軸壓應力狀態(tài)下的最大強度出現(xiàn)在應變比為0.25,含石粉機制砂再生混凝土二軸壓應力狀態(tài)下在應變比1.0時出現(xiàn)最大強度。石粉對機制砂再生混凝土二軸壓強度也有提高作用,但是提高效應不是很明顯。機制砂再生混凝土主軸峰值應變隨著應變比的增大整體呈先增大后減小的趨勢,水平軸峰值應變整體上隨著應變比的增大而增大。五、二軸壓應力狀態(tài)下各混凝土的應力-應變?nèi)都包含四部分,分別為:混凝土內(nèi)部被壓實階段、線性上升段、裂縫開展階段、下降段。各階段所占比例以及破壞劇烈程度與石粉含量、骨料類型有關。在最佳石粉含量范圍內(nèi)石粉含量越少,再生粗骨料取代率越多,機制砂再生混凝土呈脆性破壞越嚴重。六、根據(jù)實測應力-應變曲線特點建立了機制砂再生混凝土二軸受壓應力狀態(tài)下主軸受壓應力-應變?nèi)表達,其結果與試驗數(shù)據(jù)吻合良好;同時參考過鎮(zhèn)海破壞準則公式,建立了機制砂再生混凝土實用的破壞準則。
[Abstract]:As natural sand is not renewable in the short term, it is inevitable that it is an inevitable trend to seek alternative resources for concrete sand, and the mechanism sand will be the best choice. On the other hand, the increasing number of waste concrete will also become a major public hazard in the city. The organic sand is organically combined with recycled coarse aggregate to form a mechanism sand. The raw concrete can not only solve the shortage of natural resources, but also play a positive role in environmental protection. It is in line with the scientific concept of sustainable development. In this paper, 190 C35 standard cubic concrete blocks with different content of stone powder (0%5%, 10%, 15%) and different recycled coarse aggregate (0%, 33%, 66%, 100%) are made in this paper. The structure, splitting tensile strength, the mechanical properties of the uniaxial and two axial compression stress states are studied. The main research work is as follows: first, the splitting tensile test of the mechanism sand recycled concrete with different stone powder content and the replacement rate of recycled coarse aggregate shows that the optimum stone powder content of the machined sand recycled concrete is 10%; the low stone powder is low. Under the condition of content (0%, 5%), when the replacement rate of recycled coarse aggregate is 100%, the splitting tensile strength of mechanism sand concrete is the lowest, while the splitting tensile strength of the mechanism sand recycled concrete and natural sand recycled concrete with high stone powder content (10%, 15%) is the lowest when the replacement rate of recycled coarse aggregate is 66%. Two, through scanning electron microscope, the mechanism sand recycled concrete micro The results show that the stone powder can promote the hydration of cement, and the amount of the stone powder affects the quantity of the hydration products and the crystal form. When the stone powder content is 10%, the concrete can reach the best packing state. The hydration products can fill the inner hole of the coagulant soil well, and the aggregate mortar is tightly bonded. Therefore, the aggregate mortar is tightly bonded. The mechanical properties are the best. At the same time, the stone powder has the effect of filling, making the mortar more dense. Comparison and analysis of the interface transition zone, the strength of the three interface transition zones of the mechanism sand recycled concrete is sorted as the transition zone of the new mortar interface in the transition zone of the old mortar interface and the old mortar interface. Three, the regeneration of the mechanism sand The failure process and failure form of concrete were observed and analyzed by uniaxial and biaxial compression behavior tests. The failure form of concrete under single axial compression was columnar failure. The failure form under double axial pressure was basically lamellar split fracture, only due to the difference of strain ratio and the difference of the aggregate used to cause breakage crack. Four, the compressive strength of the machined sand recycled concrete under the stress state of the two axis is higher than that under the state of uniaxial stress, but the increase is slightly different, and the increase value is between 1.051 and 2.142 times. The maximum strength and the bone used under the two axis stress state. The material type is related to the strain ratio. The maximum value of the concrete with natural sand as fine aggregate appears at the strain ratio of 0.5, while the maximum strength for the two axis compressive stress state of the mechanism sand ordinary concrete and the non stone powder mechanism sand recycled concrete appears at the strain ratio of 0.25 and the two axis compressive stress of the sand regenerated concrete containing the stone powder mechanism. The maximum strength of the strain ratio is 1 at the strain ratio. The stone powder also improves the two axial compressive strength of the machined sand recycled concrete, but the effect is not obvious. The peak strain of the main shaft of the mechanism sand recycled concrete increases first and then decreases with the increase of the strain ratio, and the peak strain of the horizontal axis increases with the strain ratio as a whole. The stress strain curve of each concrete under the condition of five, two axis compressive stress contains four parts, which are the internal compaction stage, the linear rising stage, the crack development stage, the descending section. The proportion of each stage and the severity of the damage are related to the stone powder content and the aggregate type. The less the content is, the more the replacement rate of the recycled coarse aggregate is, the more brittle fracture of the machine-made sand recycled concrete is more serious. Six, according to the characteristics of the measured stress strain curve, the full curve of the compressive stress strain of the spindle under compressive stress state of the mechanism sand recycled concrete under the stress state of the two axis is established, and the result is in good agreement with the experimental data, and at the same time it has been referred to the destruction of the sea. A practical failure criterion for recycled aggregate concrete is established.

【學位授予單位】:廣西大學
【學位級別】:碩士
【學位授予年份】:2017
【分類號】:TU528

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