本文選題：活性粉末混凝土　切入點：早期收縮　出處：《北京交通大學》2017年碩士論文　論文類型：學位論文

【摘要】：活性粉末混凝土由于采用較低的水膠比、剔除粗骨料、摻加大量的超細活性摻合料及高摻量復合外加劑等原因,早期收縮遠大于普通混凝土材料,存在較高的早期開裂風險。為探究活性粉末混凝土的收縮發(fā)展規(guī)律并明確其收縮機理,準確的對活性粉末混凝土的收縮進行預測和計算,本文針對分別對常溫(25℃)浸泡、密封、干燥三種條件下材料的早期收縮進行了測量,并結合內部相對濕度、水化程度、孔結構分布和力學性能,對收縮機理進行分析并建立收縮預測模型。在此基礎上研究了不同養(yǎng)護溫度(25℃、40℃、75℃)對浸泡、密封、干燥三種養(yǎng)護條件下活性粉末混凝土材料早期收縮的影響,探討了不同養(yǎng)護條件下的收縮發(fā)展規(guī)律與變化機理。論文主要工作和結論如下:(1)測量了常溫條件下活性粉末混凝土在干燥、密封、浸泡條件下的收縮,結合內部相對濕度、水化程度和孔結構變化對其機理進行分析。結果表明:活性粉末混凝土的早期收縮受養(yǎng)護條件的影響較大,不同養(yǎng)護條件下,收縮的發(fā)展均呈前期增長較快,后期逐漸變緩趨勢,但收縮發(fā)展速率、時間及收縮值的大小均不相同。(2)密封條件與干燥條件下的收縮發(fā)展規(guī)律呈現(xiàn)出較大的差異,密封條件下,28d內收縮持續(xù)發(fā)展,而干燥條件下,前6d收縮發(fā)展較快,6d到28d內發(fā)展緩慢;從水化角度分析,密封條件下在28d內水化反應是持續(xù)進行的,自收縮也持續(xù)發(fā)展,而干燥條件下由于水分散失導致7d后水化反應發(fā)展緩慢,自收縮的發(fā)展也受到限制;從數(shù)值上看,到28d時密封條件下的收縮值比干燥條件還要高出90.5με,與普通混凝土中規(guī)律恰好相反;結合水化進程、孔結構及內部水分遷移等微觀試驗結果,進一步探討了早期收縮規(guī)律的微觀機理。(3)基于膠凝材料水化程度、內部相對濕度、彈性模量、孔隙結構分布等參數(shù),分別建立了化學收縮、自收縮及干燥收縮預測模型。以實測浸泡組的收縮應變?yōu)榛鶞?標定了密封與干燥條件下的化學收縮值;以實測密封組的收縮應變?yōu)榛鶞?標定了干燥條件下的自收縮值,實現(xiàn)了三種收縮的分離。(4)測量了三種不同的養(yǎng)護溫度(25℃、40℃、75℃)下,長期置于干燥、密封、浸泡三種條件中活性粉末混凝土的收縮,結合水化程度分析了養(yǎng)護溫度對活性粉末混凝土化學收縮、自收縮、干燥收縮的影響。不同養(yǎng)護溫度對化學收縮、自收縮和干燥收縮的影響均不相同;隨著溫度的升高,化學收縮逐漸增大,但增長的幅度不大;在浸泡條件下,較高的溫度會引起較高的早期自收縮;高溫對自收縮存在抑制作用,且溫度越高,抑制作用越明顯;在前期,干燥收縮隨著養(yǎng)護溫度的升高而增加,但高溫導致結構更加致密,抑制了后期收縮的發(fā)展。(5)結合養(yǎng)護溫度對三種收縮的影響,對高溫蒸養(yǎng)條件下的收縮規(guī)律進行分析。隨著養(yǎng)護溫度的升高,早期收縮也會隨之提高,且在濕度較高的環(huán)境中養(yǎng)護后,養(yǎng)護結束時短期內會造成較大的收縮,溫度越高,該階段的收縮值越大,成為造成開裂風險的主要原因;后期的材料收縮發(fā)展規(guī)律顯示,養(yǎng)護溫度越高,后期的體積穩(wěn)定性越好,收縮值的變化值越小。
[Abstract]:Reactive powder concrete due to the low water cement ratio, excluding coarse aggregate, because adding a large number of Co doped superfine active material and high content of composite admixture, early shrinkage is far greater than ordinary concrete materials, there is a higher risk of early cracking. In order to explore the development regularity of shrinkage of reactive powder concrete and clear its shrinkage the mechanism of shrinkage of reactive powder concrete accurate prediction and calculation, this paper respectively at room temperature (25 DEG C) soaking, sealing, early shrinkage drying under the three conditions of the material are measured, and combined with the internal relative humidity, water level, pore distribution and mechanical properties, analyze the mechanism of shrinkage and the establishment of shrinkage prediction model. On the basis of different curing temperature (25 DEG, 40 DEG, 75 DEG C) to soak, sealing material, influence of shrinkage of reactive powder concrete early drying three kinds of curing conditions, exploration To discuss the development and change rule of the shrinkage mechanism under different curing conditions. The main work and conclusions are as follows: (1) measuring the ambient temperature conditions of reactive powder concrete in drying, sealing, soaking condition contraction, combined with the internal relative humidity, degree of hydration and pore structure of the mechanism was analyzed. The results show that effect of reactive powder concrete early shrinkage by curing conditions greatly under different curing conditions, the development of shrinkage was increased faster in early and later gradually slowed the trend, but the shrinkage rate, time and shrinkage of big and small are not the same. (2) the contraction law of the development of sealing conditions and drying conditions under the present a large difference between the sealing conditions, contraction of sustainable development in 28d, and the drying conditions, before the contraction of 6D development, 6D to 28d in the slow development of hydration; from the angle of analysis, under the conditions of sealing in 28d in response to Continued the self shrinkage of sustainable development, and dry conditions caused by 7d after hydration reaction of the slow development of the loss of water, since the contraction of the development is limited; from the point of view, to 28d under the conditions of sealing shrinkage than drying conditions also higher than 90.5 Mu epsilon, contrary to common concrete rules in combination; hydration process, pore structure and internal moisture migration microscopic test results, to further explore the mechanism of early shrinkage rules. (3) based on the degree of hydration of cementitious material, internal relative humidity, elastic modulus, distribution of pore structure parameters, chemical shrinkage prediction model are established respectively, the autogenous shrinkage and drying in order to shrink. The shrinkage strain measured immersion group for the benchmark calibration of chemical shrinkage and dry sealing conditions; shrinkage strain measured with the seal group as a benchmark, calibration of the autogenous shrinkage and drying conditions, three kinds of realization Contraction of the separation. (4) three different curing temperature was measured (25 C, 40 C, 75 C), long-term in a dry, sealed, reactive powder concrete for three conditions of contraction, with the degree of hydration of curing temperature on reactive powder concrete chemical shrinkage, autogenous shrinkage, drying effect shrinkage. Different curing temperature on chemical shrinkage, self shrinkage and dry shrinkage are not the same; with the increase of temperature, the chemical shrinkage increases gradually, but little growth; in the soaking condition, the autogenous shrinkage of early high temperature causes higher temperature; on the autogenous shrinkage has inhibitory effect, and temperature the higher, the more obvious inhibition effect; in the early stage of drying shrinkage increased with increasing curing temperature, but high temperature leads to more compact structure, suppressed the late shrinkage. (5) combined with the effect of curing temperature on three kinds of shrinkage, high temperature steam curing. Under the rule of shrinkage were analyzed. With the increase of curing temperature, shrinkage will increase, and maintenance in high humidity environment, resulting in a greater contraction of the short term maintenance at the end, the higher the temperature, the phase of the contract value is bigger, become the main cause of the cracking risk; display material the law of the development of shrinkage, curing temperature is higher, the better volume stability of the late change shrinkage value is smaller.

【學位授予單位】：北京交通大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TU528

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相關期刊論文 前10條

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本文編號：1591920