【摘要】：通過(guò)試驗(yàn)研究含初始損傷混凝土在硫酸鹽腐蝕和干濕循環(huán)共同作用下的性能,分析了不同初始損傷程度混凝土隨腐蝕時(shí)間的增加,其質(zhì)量、超聲波傳播速度、強(qiáng)度、單軸壓縮應(yīng)力應(yīng)變曲線以及聲發(fā)射活動(dòng)的變化,運(yùn)用損傷力學(xué)對(duì)腐蝕損傷進(jìn)行定量評(píng)價(jià)和參數(shù)擬合,基于聲發(fā)射特性建立含初始損傷混凝土的腐蝕受荷損傷模型并進(jìn)一步分析其損傷演化過(guò)程,借助環(huán)境掃描電鏡與電子能譜技術(shù)觀測(cè)分析受硫酸鹽腐蝕作用初始損傷混凝土微結(jié)構(gòu)的變化,揭示其損傷機(jī)理.試驗(yàn)結(jié)果表明,隨著腐蝕時(shí)間的增加,不同初始損傷程度混凝土的質(zhì)量、超聲波傳播速度和強(qiáng)度均呈先增大后減小,初始損傷程度增加會(huì)加速混凝土在腐蝕作用下物理力學(xué)性能的劣化,其影響存在閾值,分別以抗壓強(qiáng)度、超聲波速為損傷變量可以建立混凝土的腐蝕損傷劣化方程,并進(jìn)一步得出不同損傷表達(dá)式間的函數(shù)關(guān)系;相同腐蝕時(shí)間下,初始損傷的增加使聲發(fā)射活動(dòng)減弱且產(chǎn)生明顯的聲發(fā)射的時(shí)間滯后;初始損傷下,基于聲發(fā)射特性的混凝土損傷演化過(guò)程可分為初期壓密階段、損傷穩(wěn)定演化階段和損傷加速發(fā)展階段3個(gè)階段;初始損傷的增加使混凝土內(nèi)部腐蝕反應(yīng)更為活躍,微裂紋網(wǎng)絡(luò)體系比無(wú)初始損傷狀態(tài)下更加發(fā)達(dá),呈現(xiàn)龜裂狀延伸和擴(kuò)展,進(jìn)而改變了混凝土的宏觀物理力學(xué)性質(zhì).
[Abstract]:The performance of concrete with initial damage under the combined action of sulphate corrosion and wet and dry cycle is studied by experiments. The mass, ultrasonic propagation speed and strength of concrete with different initial damage degree are analyzed with the increase of corrosion time. The stress and strain curves of uniaxial compression and the change of acoustic emission activity are used to quantitatively evaluate and fit the corrosion damage by damage mechanics. Based on the characteristics of acoustic emission, the damage model of concrete with initial damage is established and the damage evolution process is further analyzed. By means of environmental scanning electron microscopy (ESEM) and electron energy dispersive spectroscopy (EDS), the microstructures of initial damage concrete subjected to sulphate corrosion were observed and analyzed, and the damage mechanism was revealed. The experimental results show that with the increase of corrosion time, the mass, ultrasonic velocity and strength of concrete with different initial damage degree increase first and then decrease. The increase of initial damage degree will accelerate the deterioration of physical and mechanical properties of concrete under corrosion, and there are threshold values for its influence. The equation of corrosion damage deterioration of concrete can be established by using compressive strength and ultrasonic speed as damage variables respectively. Furthermore, the functional relationships among different damage expressions are obtained. At the same corrosion time, the increase of initial damage weakens the acoustic emission activity and lags the time of producing obvious acoustic emission. Under initial damage, the damage evolution process of concrete based on acoustic emission characteristics can be divided into three stages: initial compression stage, damage stable evolution stage and damage accelerated development stage. The increase of initial damage makes the internal corrosion reaction of concrete more active, and the micro-crack network system is more developed than that without initial damage state, which shows crack extension and propagation, and then changes the macroscopic physical and mechanical properties of concrete.
【作者單位】： 北京科技大學(xué)土木與資源工程學(xué)院;
【基金】：國(guó)家重點(diǎn)研發(fā)計(jì)劃資助項(xiàng)目(2016YFC0600800) 國(guó)家自然科學(xué)基金資助項(xiàng)目(51678049)
【分類號(hào)】：TU528
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本文編號(hào)：2411015