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  本文選題：持續(xù)荷載　切入點(diǎn)：粉煤灰混凝土　出處：《北京交通大學(xué)》2017年碩士論文

【摘要】：實(shí)際結(jié)構(gòu)中的混凝土均處于受力狀態(tài)下,結(jié)構(gòu)受載的齡期不斷提前,加載時混凝土強(qiáng)度可能仍未發(fā)展成熟,將在荷載下繼續(xù)發(fā)展,同時,荷載下混凝土力學(xué)性能發(fā)展將與無荷載狀態(tài)下有所不同。大量試驗(yàn)數(shù)據(jù)表明,低應(yīng)力下混凝土力學(xué)性能有增強(qiáng)作用,而目前對混凝土力學(xué)性能的研究幾乎沒有考慮荷載對混凝土性能的作用,故需要對荷載下粉煤灰混凝土力學(xué)性能進(jìn)行研究。隨著工程技術(shù)不斷進(jìn)步,混凝土的配合比也越來越復(fù)雜,新的摻合料和添加劑的加入使混凝土性能有很大的變化,例如粉煤灰。粉煤灰的摻入使混凝土內(nèi)部水化機(jī)理發(fā)生了變化,也使混凝土后期力學(xué)性能與普通混凝土有很大區(qū)別,在荷載作用下這一問題變得更加復(fù)雜。本文研究了荷載作用下粉煤灰混凝土力學(xué)性能發(fā)展,主要工作如下:1.對粉煤灰混凝土荷載作用下的抗壓強(qiáng)度、彈性模量隨齡期的發(fā)展進(jìn)行了試驗(yàn)研究,試驗(yàn)設(shè)計了 40%、60%兩種中高摻量的粉煤灰混凝土,自制了三角形試驗(yàn)加載設(shè)備,對加載試件在第28天施加,荷載等級為未加載試件28天棱柱體抗壓強(qiáng)度的20%,在指定齡期測試加載與非加載試件抗壓強(qiáng)度與彈性模量;2.分析了應(yīng)力下粉煤灰混凝土力學(xué)性能增強(qiáng)的機(jī)理,考慮應(yīng)力下額外的水泥水化、火山灰反應(yīng)以及額外反應(yīng)下骨料密度的改變,在漿體、漿體-骨料兩個尺度上建立適用粉煤灰混凝土的代表體積單元(REV),通過縮核水化模型得到水化及粉煤灰反應(yīng)程度發(fā)展情況,得出RVE內(nèi)各相材料體積分?jǐn)?shù);3.考慮骨料體積分?jǐn)?shù)及類型,建立了荷載作用下粉煤灰混凝土抗壓強(qiáng)度發(fā)展模型,分析加載時間和荷載等級對荷載下粉煤灰混凝土抗壓強(qiáng)度發(fā)展的影響;4.在細(xì)觀力學(xué)框架下,依次計算兩代表體積單元有效剛度,建立了荷載作用下粉煤灰混凝土彈性模量發(fā)展模型,分析加載時間和荷載等級對荷載下粉煤灰混凝土彈性模量發(fā)展的影響。
[Abstract]:The concrete in the actual structure is in the state of stress, and the age of the structural load is advancing continuously. The strength of the concrete under loading may not be mature, and it will continue to develop under the load, at the same time,The development of mechanical properties of concrete under load will be different from that under load.A large number of experimental data show that the mechanical properties of concrete can be enhanced under low stress, but the present research on the mechanical properties of concrete hardly considers the effect of load on the performance of concrete.Therefore, it is necessary to study the mechanical properties of fly ash concrete under load.With the development of engineering technology, the mix ratio of concrete is becoming more and more complicated. The addition of new admixtures and additives has greatly changed the performance of concrete, such as fly ash.The hydration mechanism of concrete is changed by the addition of fly ash, and the mechanical properties of concrete in the later stage are different from that of ordinary concrete, and the problem becomes more complicated under the action of load.The development of mechanical properties of fly ash concrete under load is studied in this paper. The main work is as follows: 1.The compressive strength and elastic modulus of fly ash concrete under loading are studied experimentally with the development of age. Two kinds of fly ash concrete with 40% and 60% content of fly ash concrete with high content are designed, and the triangular test loading equipment is made.On the 28th day, the loading grade is 20 days of the prismatic compressive strength of the unloaded specimens, and the compressive strength and elastic modulus of the loaded and unloaded specimens are 2.The mechanism of strengthening mechanical properties of fly ash concrete under stress is analyzed. Considering the additional cement hydration under stress, the pozzolanic reaction and the change of aggregate density under extra reaction,The representative volume unit of fly ash concrete was established on the two scales of slurry and aggregate. The hydration and reaction degree of fly ash were obtained by the hydration model of shrinkage nucleus, and the volume fraction of each phase material in RVE was obtained.Considering the volume fraction and type of aggregate, the development model of compressive strength of fly ash concrete under load is established, and the influence of loading time and load grade on the development of compressive strength of fly ash concrete under load is analyzed.Under the meso-mechanical framework, the effective stiffness of two volumetric elements is calculated in turn, and the elastic modulus development model of fly ash concrete under load is established.The influence of loading time and load grade on elastic modulus development of fly ash concrete under load is analyzed.
【學(xué)位授予單位】：北京交通大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TU528

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本文編號：1711586