本文選題：堿礦渣混凝土　切入點：高溫　出處：《重慶大學》2014年博士論文

【摘要】：堿礦渣水泥生產工藝簡單，生產能耗低，用其配制的堿礦渣混凝土具有優(yōu)良的力學性能和耐久性能。對于該混凝土的耐高溫性能，，不同學者有不盡一致的認識。一種觀點認為，堿礦渣水泥水化產物中幾乎不含在高溫下易發(fā)生分解的Aft和Ca(OH)2，因此，堿礦渣混凝土具有較好的耐高溫性能；另一種觀點認為，堿礦渣水泥石高溫下的收縮更大，漿體與集料間的熱變形差異導致其耐高溫性能較差。開展堿礦渣混凝土耐高溫性能研究，揭示高溫作用對其力學行為及微觀結構的影響規(guī)律，并建立數值化模型，對豐富和發(fā)展堿礦渣混凝土理論研究，指導堿礦渣混凝土結構設計和應用具有重要意義。 論文試驗研究了升溫制度、靜置時間、強度等級、集料以及纖維對高溫后堿礦渣混凝土試件外觀、質量和強度的影響；采用綜合熱分析（TG-DSC）、X射線衍射(XRD)、傅立葉轉換紅外光譜(FTIR)、掃描電子顯微鏡（SEM）、氮吸附等測試手段分析了堿礦渣水泥石高溫后產物和微觀結構的變化。建立了高溫下堿礦渣混凝土多物理場傳輸模型，推導了全耦合數值解法，并進行了算例分析。研究揭示的主要規(guī)律與取得的主要成果如下： 堿礦渣混凝土強度及結構變化與受熱溫度有關。室溫～200℃范圍內，溫度升高促進了堿礦渣水泥石水化反應，水泥石結構更加致密，混凝土抗壓強度較常溫有所增長；受熱溫度超過200℃后，水泥石與集料界面粘結強度下降，混凝土強度呈降低趨勢；600℃～700℃，堿礦渣水泥石失去非蒸發(fā)水，混凝土強度大幅度降低；受熱溫度達到800℃后，水泥石發(fā)生固相反應，生成鈣黃長石，混凝土中石灰石集料部分分解，質量損失率急劇增大，結構嚴重劣化。 堿礦渣混凝土高溫性能受強度等級的影響。低強度等級混凝土受高溫影響較小。強度等級越高，結構越密實，高溫條件下蒸汽壓力和熱應力對結構的損傷越大。堿礦渣水泥石具有比普通水泥石更大的熱收縮，高溫下水泥石與集料界面結構劣化產生的微裂紋不僅不會顯著降低混凝土強度，而且可以有效緩解蒸汽壓力對混凝土結構的破壞，避免爆裂現象的發(fā)生。與同強度等級普通混凝土相比，堿礦渣混凝土強度劣化溫度提高100～200℃。 堿礦渣混凝土高溫性能受升溫制度的影響。受熱溫度在400℃及以上溫度條件下，升溫速度越快，混凝土的損傷越嚴重；1h～6h范圍內，持溫時間越長，混凝土強度損失越大�？諝饫鋮s與水冷兩種冷卻方式作用下堿礦渣混凝土高溫后性能相近。受熱溫度低于400℃，高溫后再經標準條件養(yǎng)護，混凝土強度能夠增長。經600℃及以上溫度作用后的堿礦渣混凝土即使經標準條件養(yǎng)護，水泥石水化過程難以發(fā)展，強度損失無法恢復。 堿礦渣混凝土高溫性能受集料熱物理性能的影響。玄武巖高溫下體積變形小，與漿體界面結構穩(wěn)定，蒸氣難以散逸，導致蒸汽壓力對混凝土損傷較大。石灰石在800℃左右發(fā)生分解，對以石灰石為集料的堿礦渣混凝土結構影響顯著。頁巖陶�？紫堵蚀�，高溫作用下可以緩解蒸汽壓力對混凝土結構的破壞，降低混凝土高溫后的強度損失。比較而言，頁巖陶粒配制的堿礦渣混凝土高溫性能較好。 堿礦渣混凝土高溫性能受纖維影響較小。常溫至600℃范圍內，鋼纖維對堿礦渣混凝土增強作用明顯，受熱溫度達800℃時，鍍銅鋼纖維鍍層嚴重氧化，纖維與漿體粘結強度降低，增強作用減小。堿礦渣混凝土界面結構劣化產生的微裂紋可有效降低孔壓，聚丙烯纖維在堿礦渣混凝土高溫性能中所起的作用不明顯。 堿礦渣混凝土高溫條件下的結構變化符合多孔介質傳熱傳質規(guī)律。將堿礦渣混凝土模型化為由固體骨架與孔隙組成的多孔介質，以多孔介質理論為基礎，建立了堿礦渣混凝土高溫過程中的濕熱傳輸機制。在Bazant模型基礎上考慮了固體骨架體積應變率和孔隙壓力的全耦合效應以及全耦合效應下的彈性形變對濕熱傳輸機制的影響，發(fā)展建立了堿礦渣混凝土高溫條件下的熱-孔隙-彈塑性全耦合數學模型。 采用徑向回歸解法和Newton-Raphson向后歐拉法求解介質傳輸過程的應力增量。同時，為了保證求解過程二階收斂，提出了用于熱-孔隙-彈塑性全耦合過程求解的一致性切線模量剛度矩陣，建立非穩(wěn)態(tài)有限元格式。結合對堿礦渣混凝土熱物參數的研究，通過二次開發(fā)，采用ABAQUS軟件進行了算例分析。算例分析表明模型計算結果與實測結果偏差較小，能夠真實有效模擬高溫環(huán)境下堿礦渣混凝土結構變化過程。
[Abstract]:Alkali slag cement has the advantages of simple production process, low production energy consumption, has excellent mechanical performance and durable performance for the preparation of alkali slag concrete. The concrete for high temperature performance, different scholars have different understanding. A view that the alkali slag cement hydration products almost does not contain easily decomposed Aft at high temperature and Ca (OH) 2, therefore, alkali slag concrete has good high-temperature performance; another view, alkali slag cement stone under high temperature shrinkage is larger, resulting in poor performance of high temperature slurry and aggregate the thermal deformation difference. To carry out high temperature performance of alkali slag concrete effect of high temperature, revealing the effect on microstructure and its mechanical behavior, and to establish a numerical model for the enrichment and development of alkali slag concrete theory, it has very important significance of alkali slag concrete structure design and application.
The experimental study of heating system, setting time, strength, and fiber on aggregate after high temperature alkali slag concrete appearance, affecting the quality and strength; the comprehensive thermal analysis (TG-DSC), X ray diffraction (XRD), Fu Liye (FTIR), infrared spectrum and scanning electron microscope (SEM). The nitrogen adsorption test method of alkali slag cement stone changes after high temperature products and microstructure analysis. A high temperature alkali slag concrete multi field transmission model, deduced numerical solution of coupling, and the example is analyzed. The main results of research and reveal the main rules are as follows:
The change of slag concrete strength and structural base related to heating temperature. At room temperature to 200 DEG C, elevated temperature promoted the alkali slag cement hydration reaction of cement stone, stone structure is more compact, the compressive strength of concrete is increased at room temperature; heating temperature more than 200 DEG C, cement and Aggregate Bond strength decreased, the strength of concrete decreased; 600 to 700 DEG C, alkali slag cement stone out of non evaporable water, the concrete strength is greatly reduced; the heating temperature reaches 800 degrees Celsius, cement solid state reaction, generating gehlenite material, partial decomposition of limestone set in concrete, the mass loss rate increases rapidly, the deterioration of the structure.
The high temperature performance of alkali slag concrete is affected by the strength of low strength concrete. The effect of high temperature low. Higher intensity, more dense structure, steam pressure and heat under the condition of high temperature stress on the structural damage is greater. Alkali slag cement has shrink more than ordinary cement, cement stone under high temperature with aggregate interface structure deterioration of micro cracks will not only reduce the strength of concrete, and can effectively alleviate the damage of steam pressure on the concrete structure, avoid bursting phenomenon. Compared with the same strength grade of concrete, alkali slag concrete strength degradation temperature increased by 100~200 degrees.
Effect of high temperature performance of alkali activated slag concrete heating system. The heating temperature at 400 degrees and over temperature, warming faster, more serious damage to the concrete; 1H ~ 6h range, holding time is long, the greater the loss of concrete strength. Effects of air cooling and water cooling mode of two kinds of alkali slag concrete high temperature performance is very similar. The heating temperature is lower than 400 DEG C high temperature after standard curing condition, the strength of concrete to increase. The alkali slag concrete temperature above 600 DEG C and after the action even after standard curing condition, the cement hydration process difficult to develop, strength loss cannot be recovered.
The high temperature performance of alkali slag concrete by the effect of aggregate thermal physical properties of basalt under high temperature. The volume deformation is small, and the interface structure of slurry stability, steam to escape of steam pressure caused great damage to the concrete. The limestone at about 800 DEG to decompose, the alkali slag concrete structure of limestone aggregate shale ceramsite significantly affected. The high porosity, under the action of high temperature steam pressure can reduce the damage of concrete structure, reduce the loss of strength of concrete after high temperature. In comparison, alkali slag concrete high temperature properties of shale ceramsite prepared better.
The high temperature performance of alkali slag concrete by the fiber is less affected. Room temperature to 600 DEG C, steel fiber on alkali slag concrete reinforcing effect, heating temperature up to 800 DEG, copper plated steel fiber coating serious oxidation, reduce the bond strength of fiber and paste, enhancement of micro cracks decreases. Alkali slag concrete deterioration of interface structure can effectively reduce the pore pressure, polypropylene fiber on performance of alkali activated slag concrete in high temperature is not obvious.
Changes in the structure of alkali slag concrete under high temperature with heat and mass transfer in porous media. The regularity of alkali slag concrete model of porous medium is composed of solid skeleton and pore, based on porous medium theory, established hot alkali slag concrete during high temperature transmission mechanism. Based on the Bazant model considering the influence of the elastic deformation of the whole the coupling effect of solid skeleton volumetric strain rate and pore pressure and the coupling effect on the heat transfer mechanism, developed conditions of alkali slag concrete under high temperature heat - pore elastic-plastic coupling mathematical model.
The incremental stress radial return method and Newton-Raphson medium transmission process solving backward Euler method. At the same time, in order to ensure the two order convergence of the solution process, for the consistent tangent modulus of thermal elastic-plastic coupled pore solving stiffness matrix is proposed, the establishment of non steady state finite element scheme. The combination of hot alkali slag concrete physical parameters, through the development of two times, is analyzed by ABAQUS software. The example analysis shows that the calculated results and test results of small deviation, can effectively simulate the real environment of high temperature alkali slag concrete structure change process.

【學位授予單位】：重慶大學
【學位級別】：博士
【學位授予年份】：2014
【分類號】：TU528

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