【摘要】：輕骨料混凝土(lightweight concrete,LWC)具有輕質(zhì)高強(qiáng)、保溫隔熱、耐火抗凍等特點,能夠顯著改善結(jié)構(gòu)的抗震性能和耐久性。但破壞發(fā)生在骨料處,導(dǎo)致彈性模量低,延性問題突出,且施工過程中存在骨料上浮,引起粗細(xì)骨料分層現(xiàn)象嚴(yán)重。采用纖維增韌的自密實輕骨料混凝土(self-compacting lightweight concrete,SCLC)兼具輕骨料混凝土和自密實混凝土的優(yōu)勢,能夠顯著提高延性和改善輕骨料混凝土的施工工藝,但國內(nèi)外在該方面開展研究較少。因此,本文結(jié)合現(xiàn)有研究進(jìn)展,對自密實高性能輕骨料混凝土的配合比設(shè)計、工作性能、破壞機(jī)理、微觀結(jié)構(gòu)特征、粘結(jié)滑移等進(jìn)行了系統(tǒng)的研究,主要包括以下幾方面:(1)配合比設(shè)計與工作性能。以固定砂石體積法和全計算法為理論依據(jù),選用合適的原材料,通過調(diào)整水膠比、外加劑含量,經(jīng)過多次試配,設(shè)計了強(qiáng)度等級為LC40、LC50的SCLC及四種纖維改性自密實高性能輕骨料混凝土;開展了流動擴(kuò)展度試驗、V型漏斗試驗、L型槽試驗及U型槽試驗并通過混凝土斷面圖觀察骨料的分布情況。研究表明:設(shè)計的六組SCLC的工作性能良好,能夠滿足實際工作要求;(2)基本力學(xué)性能。通過試驗,系統(tǒng)的對立方體抗壓強(qiáng)度、劈裂抗拉強(qiáng)、抗折強(qiáng)度等力學(xué)性能進(jìn)行了研究,深入分析了纖維對其力學(xué)性能的影響。研究表明:SCLC中粗骨料的剪切破壞是導(dǎo)致其呈現(xiàn)明顯脆性破壞的重要原因,纖維的加入能夠顯著提高SCLC的劈裂抗拉強(qiáng)度、抗折強(qiáng)度,提高其韌性,改善脆性破壞特征,提高延性;(3)微觀結(jié)構(gòu)特征。采用電鏡掃描技術(shù)對微觀試驗試樣中不同齡期、不同外摻礦物的粗骨料—漿體界面、纖維—漿體界面等進(jìn)行了多倍數(shù)的觀察分析。結(jié)果顯示:SCLC的界面過渡區(qū)非常致密,粘結(jié)性能優(yōu)于普通自密實混凝土,纖維的摻入增加了漿體與骨料界面處的連接,提高了延性;(4)與變形鋼筋的粘結(jié)錨固性能。設(shè)計了10組中心拉拔試驗試件,分析了混凝土強(qiáng)度等級、鋼筋直徑、鋼筋錨固長度、不同纖維摻量對SCLC與鋼筋粘結(jié)錨固的影響規(guī)律及原因,提出了SCLC粘結(jié)強(qiáng)度的計算模型,建立了自密實高性能輕骨料混凝土與鋼筋的應(yīng)力-滑移本構(gòu)關(guān)系模型。研究表明:SCLC中漿體強(qiáng)度和骨料強(qiáng)度共同決定黏結(jié)強(qiáng)度,且漿體強(qiáng)度影響大于粗骨料,建議的滑移本構(gòu)關(guān)系模型與試驗結(jié)果吻合較好。論文研究成果可為輕骨料混凝土的工程實際應(yīng)用提供理論基礎(chǔ),能夠為改善LWC的延性提供思路,具有重要理論意義和實際價值。
[Abstract]:Lightweight aggregate concrete (lightweight concrete,LWC) has the characteristics of light weight and high strength, heat insulation, fire resistance and freezing resistance, which can improve the seismic performance and durability of the structure. However, the failure occurs at the aggregate, which leads to the low elastic modulus, prominent ductility problem, and the floatation of aggregate in the construction process, which results in serious stratification of coarse aggregate. Fiber toughened lightweight aggregate concrete (self-compacting lightweight concrete,SCLC) has the advantages of both lightweight aggregate concrete and self-compacting concrete, which can significantly improve ductility and construction technology of lightweight aggregate concrete. But there are few researches in this field at home and abroad. Therefore, combined with the existing research progress, this paper systematically studies the mix ratio design, working performance, failure mechanism, microstructure characteristics, bond-slip and so on of self-compacting high performance lightweight aggregate concrete. Mainly include the following aspects: (1) mix ratio design and performance. Based on the theory of fixed sand volume method and total calculation method, choosing suitable raw materials, through adjusting water / binder ratio, admixture content, after many tests, the strength grade is designed as LC40,. SCLC of LC50 and four kinds of fiber modified self-compacting high performance lightweight aggregate concrete; The flow expansion test, V-shaped funnel test, L-groove test and U-groove test were carried out, and the distribution of aggregate was observed through the concrete sectional diagram. The results show that the six groups of SCLC have good performance and can meet the practical requirements. (2) basic mechanical properties. The mechanical properties such as cube compressive strength splitting tensile strength and flexural strength were systematically studied and the effect of fiber on mechanical properties was analyzed. The results show that the shear failure of coarse aggregate in SCLC is an important reason for its obvious brittle failure. The addition of fiber can significantly improve the splitting tensile strength, flexural strength, toughness and brittle failure characteristics of SCLC. Improving ductility; (3) microstructure characteristics. The scanning electron microscopy (SEM) technique was used to observe and analyze the coarse aggregate / slurry interface and fiber / slurry interface of different ages and different mineral admixtures in the microcosmic test samples. The results show that the interfacial transition zone of SCLC is very compact, and the bond property is better than that of ordinary self-compacting concrete. The addition of fiber increases the connection between the slurry and aggregate interface, and improves the ductility. (4) the bond and anchoring properties of SCLC with deformed steel bar are improved. Ten groups of central drawing test specimens were designed. The influence of concrete strength grade, steel bar diameter, reinforcement Anchorage length and different fiber content on bond anchoring between SCLC and steel bar was analyzed. The calculation model of SCLC bond strength was put forward. The stress-slip constitutive model of self-compacting high performance lightweight aggregate concrete and steel bar is established. The results show that the bond strength is determined by the strength of paste and aggregate in SCLC, and the influence of the strength of slurry is greater than that of coarse aggregate. The suggested slip constitutive model is in good agreement with the experimental results. The research results can provide a theoretical basis for the practical application of lightweight aggregate concrete and provide ideas for improving the ductility of LWC. It has important theoretical significance and practical value.
【學(xué)位授予單位】：長安大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TU528

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