高寒地區(qū)大摻量粉煤灰混凝土的抗凍性能研究
發(fā)布時間：2018-10-08 17:34
【摘要】：粉煤灰作為摻合料加到混凝土中,可減少工業(yè)廢渣,同時能起到降低混凝土拌合物水化熱、減少早期開裂、提高混凝土后期強度等作用,但關于粉煤灰混凝土的抗凍性能優(yōu)劣一直存在著許多不同的觀點。高寒地區(qū)晝夜溫差大,冬季長時間處于負溫,大體積混凝土工程早期易開裂,而工程有時又必須在冬季施工。本文針對高寒地區(qū)大摻量粉煤灰混凝土的抗凍性能進行研究。首先,本文針對C30混凝土配合比設計參數(shù)進行四因素三水平L9(34)正交試驗設計,通過分析混凝土拌合物的施工和易性和抗壓強度的試驗結果來優(yōu)選配合比設計參數(shù),獲得高寒地區(qū)C30粉煤灰混凝土的較佳砂率為38%、減水劑摻量1.3%、單位用水量165 kg/m3、水膠比為0.41。然后再對不同水膠比、不同粉煤灰摻量、不同引氣劑摻量的粉煤灰混凝土抗壓強度進行分析,得出如下結論:粉煤灰摻量越大,早期強度降幅越大,而其28d~90d強度增幅越大;養(yǎng)護齡期大于28d,粉煤灰混凝土的含氣量每增加1%,其抗壓強度約降低4%~6%。其次,針對高寒地區(qū)混凝土長期經受凍融循環(huán)作用而不斷發(fā)生破壞的問題,從分析凍融破壞機理入手,通過快速凍融試驗,研究了粉煤灰摻量、引氣劑摻量對抗凍性能的影響規(guī)律,然后通過亞微觀的氣泡特征參數(shù)分析不同粉煤灰摻量與不同引氣劑摻量的粉煤灰混凝土的抗凍性能,得出如下結論:粉煤灰混凝土28d的抗凍等級明顯低于未摻粉煤灰的基準混凝土,隨著齡期的增長,粉煤灰混凝土的抗凍性能顯著增強;粉煤灰摻量為35%的60d齡期混凝土的氣泡間距系數(shù)最小,其耐久性系數(shù)最大,抗凍性能最佳;加入引氣劑能有效改善粉煤灰混凝土的抗凍性能,當含氣量在5.2%左右時,混凝土的氣泡間距系數(shù)最小,抗凍性能最佳。最后,通過電通量試驗研究不同粉煤灰摻量、不同引氣劑摻量的粉煤灰混凝土的抗氯離子滲透性能,研究結果表明:延長混凝土的養(yǎng)護齡期,有利于提高其抗氯離子滲透性能;隨著粉煤灰摻量的增加,其抗氯離子滲透性能先增加再降低,在摻量為45%左右時達到最佳;隨著含氣量增加,粉煤灰混凝土的抗氯離子滲透性能先增加再降低。在含氣量為5.2%左右時,其抗氯離子滲透性能最佳。
[Abstract]:The addition of fly ash as admixture to concrete can reduce industrial waste slag, reduce hydration heat of concrete mixture, reduce early cracking, and improve the later strength of concrete, etc. However, there are many different views on the frost resistance of fly ash concrete. The temperature difference between day and night in the high cold area is large and the temperature is negative for a long time in winter. Mass concrete works are easy to crack in the early stage, and sometimes the construction must be carried out in winter. In this paper, the frost resistance of high-volume fly ash concrete in high cold area is studied. First of all, according to the design parameters of C30 concrete mix ratio, four factors and three levels L9 (34) orthogonal experimental design are carried out. By analyzing the construction of concrete mixture and the test results of ease and compressive strength, the design parameters of mix ratio are optimized. The best sand ratio of C30 fly ash concrete in high cold area is 38, the water reducing agent content is 1.3 and the water-binder ratio of 165 kg/m3, per unit water consumption is 0.41. Then the compressive strength of fly ash concrete with different water binder ratio, different fly ash content and different air entraining agent is analyzed. The conclusion is as follows: the greater the fly ash content, the greater the early strength decrease, and the greater the 28d~90d strength increase; When the curing age is more than 28 days, the compressive strength of fly ash concrete decreases by about 4% for every increase in the air content of fly ash concrete. Secondly, in view of the problem that the concrete in the alpine region is destroyed by freeze-thaw cycle for a long time, starting with the analysis of the mechanism of freeze-thaw failure, through the rapid freeze-thaw test, the content of fly ash is studied. The effect of air entraining agent content on freezing resistance is studied. Then the frost resistance of fly ash concrete with different content of fly ash and different air entraining agent is analyzed by sub-micro bubble characteristic parameters. The conclusions are as follows: the frost resistance of fly ash concrete for 28 days is obviously lower than that of standard concrete without fly ash, and the frost resistance of fly ash concrete increases with the increase of age. The air-entraining agent can effectively improve the frost resistance of fly ash concrete when the air content is about 5.2%, and the air-entraining agent can improve the frost resistance of fly ash concrete with 35% air entrainer, and the coefficient of bubble spacing is the smallest, the durability coefficient is the largest, and the frost resistance is the best when the air content is about 5.2%. The bubble spacing coefficient of concrete is the smallest and the frost resistance is the best. Finally, the chloride ion permeability of fly ash concrete with different content of fly ash and different air entraining agent is studied by electric flux test. The results show that prolonging the curing age of concrete is beneficial to the improvement of chloride ion permeability of concrete. With the increase of the content of fly ash, the penetration resistance of fly ash first increases and then decreases, and reaches the best when the content of fly ash is about 45%, and with the increase of air content, the permeability of fly ash concrete increases first and then decreases. When the gas content is about 5.2%, the resistance to chloride ion penetration is the best.
【學位授予單位】：重慶交通大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TU528
本文編號：2257665
[Abstract]:The addition of fly ash as admixture to concrete can reduce industrial waste slag, reduce hydration heat of concrete mixture, reduce early cracking, and improve the later strength of concrete, etc. However, there are many different views on the frost resistance of fly ash concrete. The temperature difference between day and night in the high cold area is large and the temperature is negative for a long time in winter. Mass concrete works are easy to crack in the early stage, and sometimes the construction must be carried out in winter. In this paper, the frost resistance of high-volume fly ash concrete in high cold area is studied. First of all, according to the design parameters of C30 concrete mix ratio, four factors and three levels L9 (34) orthogonal experimental design are carried out. By analyzing the construction of concrete mixture and the test results of ease and compressive strength, the design parameters of mix ratio are optimized. The best sand ratio of C30 fly ash concrete in high cold area is 38, the water reducing agent content is 1.3 and the water-binder ratio of 165 kg/m3, per unit water consumption is 0.41. Then the compressive strength of fly ash concrete with different water binder ratio, different fly ash content and different air entraining agent is analyzed. The conclusion is as follows: the greater the fly ash content, the greater the early strength decrease, and the greater the 28d~90d strength increase; When the curing age is more than 28 days, the compressive strength of fly ash concrete decreases by about 4% for every increase in the air content of fly ash concrete. Secondly, in view of the problem that the concrete in the alpine region is destroyed by freeze-thaw cycle for a long time, starting with the analysis of the mechanism of freeze-thaw failure, through the rapid freeze-thaw test, the content of fly ash is studied. The effect of air entraining agent content on freezing resistance is studied. Then the frost resistance of fly ash concrete with different content of fly ash and different air entraining agent is analyzed by sub-micro bubble characteristic parameters. The conclusions are as follows: the frost resistance of fly ash concrete for 28 days is obviously lower than that of standard concrete without fly ash, and the frost resistance of fly ash concrete increases with the increase of age. The air-entraining agent can effectively improve the frost resistance of fly ash concrete when the air content is about 5.2%, and the air-entraining agent can improve the frost resistance of fly ash concrete with 35% air entrainer, and the coefficient of bubble spacing is the smallest, the durability coefficient is the largest, and the frost resistance is the best when the air content is about 5.2%. The bubble spacing coefficient of concrete is the smallest and the frost resistance is the best. Finally, the chloride ion permeability of fly ash concrete with different content of fly ash and different air entraining agent is studied by electric flux test. The results show that prolonging the curing age of concrete is beneficial to the improvement of chloride ion permeability of concrete. With the increase of the content of fly ash, the penetration resistance of fly ash first increases and then decreases, and reaches the best when the content of fly ash is about 45%, and with the increase of air content, the permeability of fly ash concrete increases first and then decreases. When the gas content is about 5.2%, the resistance to chloride ion penetration is the best.
【學位授予單位】：重慶交通大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TU528
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