本文選題：大流動性混凝土 + 抗裂輔料　； 參考：《東南大學》2017年碩士論文

【摘要】：隨著中國經(jīng)濟的快速發(fā)展,政府在基建類項目上大力投資,因此對混凝土需求量逐年增大�，F(xiàn)代高性能混凝土提高流動性以便于泵送施工,但大流動性混凝土的開裂問題一直困擾著工程技術(shù)人員。人們試圖通過增加配筋和降低混凝土收縮來減小混凝土開裂傾向,但收效甚微,大流動性混凝土均勻性差和易開裂的問題仍沒有得到很好的解決。均勻性主要是骨料在混凝土中均勻分布的程度,它是影響混凝土抗裂性能的重要因素,本文研究了大流動性混凝土均勻性的檢測和表征方法,提出采用混凝土離析率、內(nèi)外混凝土密度差和內(nèi)外混凝土粗骨料質(zhì)量差來表征新拌混凝土均勻性,采用超聲波聲速表征硬化混凝土均勻性,還可以采用圖像處理法精確描述和研究混凝土內(nèi)部結(jié)構(gòu)的均勻性。影響混凝土均勻性的因素包括原材料質(zhì)量,如砂石級配;混凝土配比參數(shù),如水膠比、砂率和減水劑摻量;混凝土和易性,如流動性、保水性和粘聚性;還有施工控制和振動時間。而關(guān)鍵因素則是混凝土流動性和振動時間。均勻性差的混凝土局部表現(xiàn)出砂漿或凈漿的特點,其抗壓強度降低、收縮增大,抗裂性能明顯下降。本文提出用混凝土超聲波聲速的不均勻度大小來判斷混凝土的不均勻性,不均勻度越小,混凝土的均勻性越好,混凝土干燥收縮率越低,抗裂性能和抗氯離子滲透性能增強�；炷辆鶆蛐杂绊懸蛩剌^多,流動性、砂率、水膠比、振動時間對混凝土均勻性的影響各不相同;在不改變其它條件的前提下,根據(jù)混凝土均勻性表征結(jié)果,研究混凝土均勻性對其強度和耐久性能的影響。通過改善混凝土和易性來提升混凝土均勻性,改善混凝土和易性主要從兩個方面實施,一方面控制原材料質(zhì)量與優(yōu)化混凝土配合比參數(shù);另一方面,在混凝土施工過程中,要嚴格控制配料的準確性、攪拌均勻性和成型的密實性,特別是控制好混凝土的流動性和振搗時間。本文分析了大面積混凝土易開裂的原因,使用研制的抗裂輔料摻入混凝土表層,通過改善混凝土表層均勻性可以顯著提高混凝土表層抗裂性能,針對不同強度等級的混凝土選用相應的抗裂輔料,可使其抗塑性開裂性能提升95%。對低水膠比高自收縮的高強混凝土,采用摻輕質(zhì)粒內(nèi)養(yǎng)護技術(shù),內(nèi)養(yǎng)護效果明顯,提高了混凝土的強度,降低了混凝土的收縮,提高了混凝土抗裂性能和抗硫酸鹽侵蝕能力。
[Abstract]:With the rapid development of China's economy, the government has invested heavily in infrastructure projects, so the demand for concrete is increasing year by year. Modern high performance concrete (HPC) improves fluidity in order to facilitate pumping construction, but the cracking problem of high fluidity concrete has been puzzling engineers and technicians. People try to reduce the cracking tendency of concrete by increasing reinforcement and reducing concrete shrinkage, but there is little effect. The problems of poor uniformity and easy cracking of large fluidity concrete have not been solved well. Homogeneity is mainly the degree of uniform distribution of aggregate in concrete. It is an important factor that affects the crack resistance of concrete. In this paper, the detection and characterization method of homogeneity of high fluidity concrete is studied, and the segregation rate of concrete is proposed. The uniformity of freshly mixed concrete is characterized by the density difference of inner and outer concrete and the quality difference of coarse aggregate of inner and outer concrete, and the uniformity of hardened concrete is characterized by ultrasonic sound velocity. Image processing method can also be used to accurately describe and study the homogeneity of concrete internal structure. Factors affecting the homogeneity of concrete include raw material quality, such as gradation of sand and stone; concrete proportioning parameters, such as water-binder ratio, sand ratio and water reducer content; concrete and easiness, such as fluidity, water retention and agglomeration; There is also construction control and vibration time. The key factors are concrete fluidity and vibration time. The concrete with poor homogeneity shows the characteristics of mortar or mortar, its compressive strength decreases, its shrinkage increases, and its crack resistance decreases obviously. In this paper, it is proposed that the unevenness of ultrasonic velocity of concrete be used to judge the inhomogeneity of concrete. The smaller the unevenness of concrete is, the better the uniformity of concrete is, the lower the drying shrinkage of concrete is, the stronger the crack resistance and chloride ion permeability are. There are many factors affecting the homogeneity of concrete, such as fluidity, sand ratio, water / binder ratio, vibration time and so on. The influence of the uniformity of concrete on its strength and durability was studied. To improve the uniformity of concrete through improving concrete and easiness, the improvement of concrete and ease is mainly carried out from two aspects: on the one hand, controlling the quality of raw materials and optimizing the parameters of concrete mix ratio; on the other hand, in the process of concrete construction, It is necessary to strictly control the accuracy of ingredients, mixing uniformity and compactness, especially the fluidity and vibrational time of concrete. In this paper, the causes of cracking in large area concrete are analyzed. The crack resistance of concrete surface can be improved by adding the crack resistant adjuncts to the surface layer of concrete by improving the uniformity of the surface layer of concrete. The crack resistance of concrete with different strength grades can be improved by 95% by selecting corresponding crack resistant adjuncts. For high strength concrete with low water-binder ratio and high autogenous shrinkage, the effect of internal curing is obvious, the strength of concrete is improved, the shrinkage of concrete is reduced, and the crack resistance and sulfate corrosion resistance of concrete are improved.
【學位授予單位】：東南大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TU528

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