第18卷第1期建筑材料學(xué)報(bào)Vol. 18. No. 12015年2月JOURNAL OF BUILDING MATERIALSFeb.,2015文章編號(hào):1007-9629(2015)01-0007粗聚烯烴纖維混凝土圓板彎曲韌性和表征方法鄧宗才1,曲玖齡1,劉國(guó)平2,施慧聰2(1.北京工業(yè)大學(xué)城市與重大工程安全減災(zāi)省部共建重點(diǎn)實(shí)驗(yàn)室,北京100124;2.上海羅洋新材料科技有限公司,上海200120)摘要:通過(guò)圓板試件研究了新型粗聚烯烴纖維混凝土的彎曲韌性,探討了纖維摻量、纖維長(zhǎng)度和基體強(qiáng)度等對(duì)圓板能量吸收值的影響規(guī)律.試驗(yàn)發(fā)現(xiàn):纖維摻量與圓板能量吸收值成正比;纖維長(zhǎng)度介于38~60mm時(shí),圓板能量吸收值隨纖維長(zhǎng)度增加而增大,當(dāng)纖維長(zhǎng)度≥48mm時(shí),其荷載-撓度曲線(xiàn)下降段出現(xiàn)應(yīng)變強(qiáng)化特征,荷載有2次峰值.分析了美國(guó) ASTM O1550在評(píng)價(jià)韌性方面存在的問(wèn)題,提出了以圓板初裂撓度為初始參考撓度,基于能量比值法的韌性指標(biāo)評(píng)定方法,該方法可表征粗纖維對(duì)混凝土板初裂后韌性的貢獻(xiàn),并可直接與理想彈塑性材料的韌性指標(biāo)進(jìn)行比較關(guān)鍵詞:粗聚烯烴纖維;彎曲韌性;圓板;韌性指標(biāo);能量吸收中圖分類(lèi)號(hào):TU528.572文獻(xiàn)標(biāo)志碼:Adoi:10.3969/j.isn.1007-9629.2015.01.002Flexural Toughness and Its Characterization of a New Kind ofMacror-polyolefin Fiber Reinforced Concrete PlateDENG Zongcai, QU Jiuling, LIU GuopiSHI Huicon(1. Key Laboratory of Urban Security and Disaster Engineering, Ministry of Education, Beijing University of TechnologyBeijing 100124, China; 2. Shanghai Royang Innovative Material Technologies Co, Ltd, Shanghai 200120, ChinaAbstract: In order to examine the toughness of concrete circular plates reinforced with a new type of macro- polyolefin fiber, a circular plate test was performed and the effects of fiber use level, fiber length and the matrixstrength on the flexural toughness, energy absorption value were investigated. The test results show that the absorption energy value is proportional to fiber use level; when fiber length is between 38 to 60 mm, the absorptionenergy value increases with increasing fiber length. When the fiber length is greater than or equal to 48 mm, in thedescending stages on the load-deflection curve strain hardening behavior appears with two peak loads. The prollems with evaluating the flexural toughness using ASTM C1550 were analyzed based on the energy ratio methodand a new toughness evaluating method was proposed. This new method, taking the first-crack deflection as theinitial reference deflection, can be used to characterize the contribution of macro- polyolefin fiber to the flexuraltoughness after initial crack, and can directly used to compare the toughness index with perfect elastoplastic material.Key words: macro-polyolefin fiber; flexural toughness; circular plate; flexural toughness index; absorp-tionf energy分布于混凝土中的高性能纖維對(duì)裂縫擴(kuò)展具有良好力能量吸收能力或結(jié)構(gòu)整體變形能力事?部普通混凝土容易開(kāi)裂并發(fā)生脆性破壞,而亂向結(jié)構(gòu)在出現(xiàn)裂縫后的帶裂縫工作能力纖維阻裂能的抑制作用,可顯著改善混凝土的裂后性能和韌本文試驗(yàn)研究了新型粗聚烯烴纖維混凝土圓板性1.韌性指標(biāo)定量表征了纖維混凝土材料、構(gòu)件或試件的彎曲韌性,測(cè)定了其荷載-撓度全曲線(xiàn),分析收稿日期:2013-07-26;修訂日期:2013-10-23中國(guó)煤化工基金項(xiàng)目:國(guó)家自然科學(xué)基金資助項(xiàng)目(51378032);北京自然科學(xué)基金資助項(xiàng)目(81420HCNMHG第一作者:鄧宗才(1961-),男陜西扶風(fēng)人,北京工業(yè)大學(xué)教授博士生導(dǎo)師博士E-mail:dengzc@biut.edu.cn建筑材料學(xué)報(bào)第18卷了纖維摻量、纖維長(zhǎng)度、基體強(qiáng)度等對(duì)圓板試件彎曲韌性的影響規(guī)律,并與理想彈塑性材料進(jìn)行比較.根據(jù)美國(guó) ASTM C1550標(biāo)準(zhǔn),計(jì)算了圓板試件的能量吸收值,結(jié)合粗聚烯烴纖維混凝土圓板變形大的特點(diǎn),提出了新的裂后韌性指標(biāo)計(jì)算方法該方法以纖維混凝土圓板的初裂撓度作為荷載-撓度全曲線(xiàn)上的初始參考變形,以衡量纖維對(duì)圓板裂后耗能能力的貢獻(xiàn),可直觀(guān)地與理想彈塑性材料的韌性指圖1圓板試驗(yàn)裝置標(biāo)進(jìn)行比較Fig. 1 Apparatus for circular plate test1圓板試驗(yàn)概況的纖維逐漸從基體中拔出或拉斷,呈延性破壞.纖維長(zhǎng)度為38mm的試件中纖維基本上發(fā)生拔出破壞;1.1纖維特性及混凝土配合比纖維長(zhǎng)度為48,60mm的試件中,纖維被拉斷的平新型粗聚烯烴纖維(簡(jiǎn)稱(chēng)聚烯烴纖維)由上海羅均比例分別為56%和76%洋科技公司提供,纖維表面壓痕、沿長(zhǎng)度方向呈波浪2.2圓板的荷載-撓度全曲線(xiàn)狀,長(zhǎng)度分別為38,48,60mm,直徑均為1.0mm,圖2為素混凝土和部分纖維混凝土圓板試件的抗拉強(qiáng)度為600MPa,彈性模量為10GPa,斷裂延彎曲荷載撓度(F8)全曲線(xiàn)伸率為17%.2種基準(zhǔn)混凝土的設(shè)計(jì)強(qiáng)度分別為由圖2可見(jiàn):當(dāng)纖維長(zhǎng)度≥48mm時(shí),試件的荷30,40MPa,配合比見(jiàn)表1載-撓度全曲線(xiàn)下降段出現(xiàn)二次上升現(xiàn)象,即有應(yīng)變表1混凝土配合比Table 1 Mix proportion of concretek強(qiáng)化特征;隨著纖維摻量的增加,二次強(qiáng)化現(xiàn)象更加明顯,荷載-撓度全曲線(xiàn)下降過(guò)程趨緩,且纖維長(zhǎng)度Strength Cement Sand Gravel Water Water reducinggradegent為60mm試件的下降段比48mm試件的下降段更3337981149168為平緩40078711001642.3美國(guó) ASTM O1550評(píng)價(jià)方法1.2試件制作及編號(hào)據(jù)美國(guó) ASTM C1550標(biāo)準(zhǔn),按式(1)計(jì)算了各按照美國(guó) ASTM O1550標(biāo)準(zhǔn),圓板試件直徑為圓板試件的能量吸收值v,并列于表2.表中數(shù)值為800mm,厚度為75m,試件澆注24h后脫模,在每組試驗(yàn)3個(gè)試件平均值標(biāo)準(zhǔn)養(yǎng)護(hù)室內(nèi)養(yǎng)護(hù)28d,試驗(yàn)前3h從養(yǎng)護(hù)室取出do(1)個(gè)圓板試件試件編號(hào)中FC后數(shù)字為基體強(qiáng)度,其式中:2=2-(2805),為荷載撓度曲線(xiàn)下面后數(shù)據(jù)分別為纖維長(zhǎng)度及其摻量,如FC30-48-6即積;t,d分別為圓板實(shí)測(cè)平均厚度和直徑;to和da表示基體強(qiáng)度為C30,纖維長(zhǎng)度為48mm,纖維摻量分別為圓板標(biāo)準(zhǔn)厚度和直徑,取75mm和800mm為6kg/m3的圓板試件δ為修正后的板中心處撓度1.3加載2.3.1纖維長(zhǎng)度對(duì)板彎曲韌性的影響按美國(guó) ASTM C1550方法對(duì)圓板試件加載,試由表2可見(jiàn),纖維摻量為3,6,9kg/m3的FC30驗(yàn)裝置如圖1所示試件中心處受力,恒位移控制加60系列試件在撓度為40mm時(shí)其能量吸收值比載,加載速度為(4.0±1.0)mm/min,測(cè)定試件中心FC30-48系列試件分別提高約64%,37%和60%點(diǎn)撓度值;荷載及撓度值由計(jì)算機(jī)自動(dòng)采集纖維摻量為3,6,9kg/m3的FC40-60系列試件在撓2圓板試驗(yàn)結(jié)果度為40mm時(shí)其能量吸收值比FC40-48系列試件分別提高約32%,50%和44%.這說(shuō)明纖維長(zhǎng)度是2.1試件破壞過(guò)程影響圓板試件彎曲韌性的主要因素之一,當(dāng)纖維長(zhǎng)加載過(guò)程中,素混凝土圓板在達(dá)到最大彎曲荷度為38~60mm時(shí),試件吸收的總能量幾乎與纖維載后瞬間斷裂,為脆性破壞摻聚烯烴纖維的圓板當(dāng)長(zhǎng)度成正比中國(guó)煤化工拔出過(guò)程中消荷載達(dá)到一定值后,其下表面通常萌生3條裂縫,且耗的能量CNMHG裂后變形能力隨荷載増加而不斷擴(kuò)展,至峰值荷載后,裂縫截面處提髙.第1期鄧宗才,等:粗聚烯烴纖維混凝土圓板彎曲韌性和表征方法305C30FC30-48-3FC30-48-6c30FC30.603Fc30.60-6z20FC30-48-9FC30-60-905101520253035404505101520253035404o/mm(a) Load-deflection curves of FC30-48b) Load-deflection curves of FC30-6050305050C40FC40-48-3FC4048-6C40FC40-60-3FC40-48305050FC40-60-6FC40-60-905101520253035404505101520253035404o/mm(c) Load-deflection curves of FC40-48(d) Load-deflection curves of FC40-60圖2混凝土圓板試件的荷載-撓度全曲線(xiàn)Fig 2 Load-deflection curves of specimens表2聚烯烴纖維混凝土圓板試件的能量吸收值分別提高約35%,17%和36%;對(duì)于纖維長(zhǎng)度38,Table 2 Absorption value of energy for specimens with polyolefin fiber48,60mm的FC40系列試件,纖維摻量為9kg/m3Specimen Peak/J時(shí)的能量吸收值比纖維摻量為6kg/m3時(shí)分別提高eleA=5mm8-10mb=20mmb=4mm約62%,58%和52%可見(jiàn)纖維摻量會(huì)顯著影響圓28.637.140.341.041,0板的彎曲韌性,圓板吸收的總能量與纖維摻量基本FC30-38-328.038.047.759.872.4成正比纖維摻量≤9kg/m°時(shí),隨纖維摻量增加,FC30-38-630.449.870.9101.0135.8圓板試件吸收能量值增大,變形能力增強(qiáng)FC30-38-928.459.792.4136.8184.02.3.3基體強(qiáng)度對(duì)板彎曲韌性的影響FC30-48-326.745.869.1107.0143.4從表2可見(jiàn),當(dāng)纖維摻量和長(zhǎng)度相同時(shí),FC4FC30-48-628.055.9104.1系列試件的總能量吸收值高于FC30系列試件,撓FC30-48-927.662.9122.3222.7322.9度為40mm時(shí),FC40-38系列試件比基體強(qiáng)度為Fc306329.157.398.1161.62344C30的FC30-38系列試件能量吸收值提高3%FC30-60-627.173.7146.3255.2379.715%;FC40-48系列試件能量吸收值比FC30-48系列FC30-60-929.484.4180.5336.9517.5試件提升1%~31%,FC40-60系列試件的能量吸37.340.741.842.042.0收值比FC30-60系列試件提升3%~18%.可見(jiàn),基FC4038334.239.950.062.979.2體強(qiáng)度也是影響粗聚烯烴纖維混凝土板韌性的因素FC40-38-635.748.166,9140.1之一,原因是隨著基體強(qiáng)度增加,纖維與基體之間的FC40-38-936.061.2100.2159.7211,9黏結(jié)強(qiáng)度提高,從而使得纖維從基體中拔出時(shí)耗散FC40-48-337.853.681.2123.3156.9的能量增大FC4048640.264.8124190.7280.62.4改進(jìn)的韌性指標(biāo)評(píng)價(jià)方法FC40-48-941.373.18.8305.8425.7ASTM O1550評(píng)價(jià)方法僅計(jì)算了荷載一撓度曲FC40-60-337.961.399.7154.線(xiàn)下的總面積,即對(duì)耗能值做了評(píng)價(jià),不能直觀(guān)地與FC40-60-636.879.21540272.8404.8FC40-60-940.1105.2219.7405.8614.5理想彈塑性材料耗能能力進(jìn)行比較,不便于設(shè)計(jì)者采用.因此,需要提出新的韌性評(píng)價(jià)方法,以直觀(guān)表2.3.2纖維摻量對(duì)板彎曲韌性的影響征纖維對(duì)基體裂后韌性的改善程度.韌性實(shí)質(zhì)上是從表2看出,在撓度為40mm時(shí),對(duì)于纖維長(zhǎng)衡量纖維對(duì)混rV凵中國(guó)煤化工能力的貢獻(xiàn)度38,48,60mm的FC30系列試件,纖維摻量為表3統(tǒng)計(jì)了CNMHG初裂撓度、初9kg/m3時(shí)的能量吸收值比纖維摻量為6kg/m3時(shí)裂荷載、峰值撓度及其能量吸收值等韌性指標(biāo)建筑材料學(xué)報(bào)第18卷mabk3Dn3國(guó)板試件的初裂撓度蛐儻攙度及對(duì)應(yīng)的荷、能量吸收值load, absorption of energy at first crack and peak for specimens with polyolefin fiberDeflectionLoad at first Energy absorptionPeakPeakEnergy absorptionat firstat firstcrack/kNdeflection/mmload/kNat peakelectionC301.3927.916.11.49FC30-38-315.61.51FC30-38-628.616.21.44FC30-38-91.3726.716.128.417.1FC30-483FC30-48-616.3FC30-48-91.4716.01.5718.228.229.1FC30-60-61.591.67FC3060-91.6027.020.21.9629.425.4C4021.11.5837.324.2FC40-38-31.4233.0L.5022.0FC40-38-61.4723.6FC4038-91.4922.71.58FC4048-3FC40-48-638.124.340.228.6FC4048-91.5826.21.7241.3FC40-60-31.5924.2FC40-60-625.01.7628.8FC40-60-91.6138.226.41.7140.129.2由圖2可見(jiàn),每條荷載-撓度全曲線(xiàn)在峰值撓度基于能量吸收的韌性指標(biāo)定義為:(1)給定撓度前基本重合,且初裂撓度與峰值撓度很接近由表3n6下纖維的韌性貢獻(xiàn)△En,=En,-E4,其中E并結(jié)合表2可知:(1)基體強(qiáng)度一定時(shí),纖維摻量、纖為該撓度變形所對(duì)應(yīng)的荷載-撓度全曲線(xiàn)下面積維長(zhǎng)度對(duì)試件初裂撓度、初裂荷載和初裂時(shí)的能量E為初裂撓度對(duì)應(yīng)的面積;(2)給定撓度n0。下的吸收值影響很小,FC0系列試件初裂時(shí)的能量吸收韌性指標(biāo)Tx-1(n)為:均值為16.7J,標(biāo)準(zhǔn)差為1.31J;FC40系列試件初裂△EnEE時(shí)的能量吸收均值為23.88J,標(biāo)準(zhǔn)差為2.1J.(2)板開(kāi)裂后纖維摻量和纖維長(zhǎng)度對(duì)能量吸收值的式中:n為計(jì)算韌性指標(biāo)時(shí)所取的纖維混凝土初裂影響程度隨著撓度增加而逐漸增大,在撓度為40mm撓度8的倍數(shù).顯然,當(dāng)n=1時(shí)Tx-1(n)=0,表時(shí)FC30系列試件比素混凝土試件C30的能量吸收示素混凝土開(kāi)裂后的韌性指標(biāo)為零值增加31.4~476.5J,提高76.6%~1162.2%;對(duì)于理想彈塑性材料7,韌性指標(biāo)T2(n-1(n)FC40系列試件比素混凝土試件C40的能量吸收滿(mǎn)足:值增加37.2~572.5J,提高88.6%~1363.1%.T2m1)(n)=2(n-1),n=5,6,7,…(3)可見(jiàn),纖維混凝土板開(kāi)裂后,主要通過(guò)裂縫處纖維本文定義的韌性指標(biāo)T2(m-1(n)直觀(guān)和定量地拉拔做功而消耗能量,纖維長(zhǎng)度、纖維摻量是影響表征了粗纖維混凝土相比理想彈塑性材料韌性的其裂后耗能能力的主要因素改善程度繪定墟度n(n=5,10,15,因此,本文采用粗聚烯烴纖維混凝土初裂撓20,25)時(shí)按中國(guó)煤化工性指標(biāo)值,并與度a作為圓板試件荷載-撓度全曲線(xiàn)上的初始參按式(3)計(jì)CNMH韌性指標(biāo)進(jìn)行考變形,以衡量纖維對(duì)試件裂后耗能能力的貢獻(xiàn).了對(duì)比第1期鄧宗才,等:粗聚烯烴纖維混凝土圓板彎曲韌性和表征方法表4粗聚煬烴纖維混凝土圓板試件的裂后韌性指標(biāo)T(n)韌性指標(biāo)比摻量為6kg/m3時(shí)分別提高約85%,Table 4 Toughness index Tue-n(n)for concrete specimensith polyolefin fiber26%和47%,比摻量為3kg/m3時(shí)分別提高約T2(-1)(n)237%,119%和178%.這說(shuō)明當(dāng)纖維摻量增加時(shí),T(5)Ts(10)T2(15)Tw(20)T4(25在裂縫界面處會(huì)有更多的纖維拉拔滑移做功,從而耗散更多的能量,提升了板的裂后韌性.另外,在撓Perfect elastoplasticmaterial8.0018.0028.0038004800度為58和108,處的纖維混凝土裂后韌性指標(biāo)與理想彈塑性材料的韌性指標(biāo)比較接近;隨著撓度增FC30-38-31.942.673.213.623.87加,纖維混凝土韌性指標(biāo)與理想彈塑性材料的韌性FC3038-62.764.375.596.517.283.796.268.109.3710.43指標(biāo)差距變大FC3038-9FC30-48-32714796347.417.913結(jié)論FC30-48-64.299.0212.6215.0416.705,4711.3714.9318.4519.88(1)纖維摻量是影響混凝土圓板彎曲韌性的重FC30-60-33.947.389.941.8413.27要因素之一,隨著纖維摻量增加,圓板試件的荷載FC306066.29124116.5219952243撓度全曲線(xiàn)下面積增大,纖維從基體拔出時(shí)耗散的FC30-60-96.35135818.792217257能量更多,抗彎韌性明顯改善FC40-3831.492.112.522.913.11(2)當(dāng)纖維摻量為6~9kg/m3,纖維長(zhǎng)度≥FC4038-61.923.023.964.695.6648mm時(shí),荷載-撓度曲線(xiàn)下降段出現(xiàn)二次上升現(xiàn)FC40-3892.885.247.098.5510.49象,即呈現(xiàn)變形強(qiáng)化特征FC40-48-32.033.814.85(3)隨著纖維長(zhǎng)度增大,圓板試件的荷載-撓度288687.789.3410.43全曲線(xiàn)下降段變得平緩,其抗彎韌性明顯改善FC40-48-93.827.7810.2411.9513.18(4)隨著基體強(qiáng)度增大,圓板試件的彎曲韌性指FC40-60-33,74標(biāo)略有提升,但基體強(qiáng)度對(duì)其彎曲韌性的影響程度FC40-60-65.379.9613.1815.5417.27FC40-60-97.0913.8819.1822.7225.37小于纖維摻量和纖維長(zhǎng)度(5)根據(jù)粗纖維混凝土板變形能力大的特點(diǎn),提2.4.1纖維長(zhǎng)度對(duì)裂后韌性指標(biāo)的影響出了基于能量比值的裂后韌性指標(biāo)評(píng)價(jià)方法,取由表4可見(jiàn),隨著纖維長(zhǎng)度增加混凝土板的裂(5~25)δ撓度時(shí)纖維的韌性貢獻(xiàn)與初裂時(shí)的能量后韌性指標(biāo)T21(n)顯著提升,FC30-60系列試件吸收值之比作為裂后韌性指標(biāo),更能科學(xué)地表征粗在撓度為256。處的裂后韌性指標(biāo)比FC3048系列纖維對(duì)圓板試件韌性的提升程度.圓板試件的韌性試件分別提高約68%,34%和30%,比FC3038系指標(biāo)隨纖維長(zhǎng)度、纖維摻量的增加而明顯提高.列試件分別提高約243%,208%和147%FC40-60系列試件在撓度為258處的裂后韌參考文獻(xiàn):性指標(biāo)T2=1(n)比FC40-48系列試件分別提升約1]鄧宗才高性能合成纖維混凝土M,北京;科學(xué)出版社,20052%,66%和92%,比FC4038系列試件分別提升45-48.DENG Zongcai. The high performance synthesis fiber rein約193%,205%和142%.這說(shuō)明當(dāng)纖維長(zhǎng)度增加forced concrete[M]. Beijing: Science Press, 2003: 45-48.(in時(shí),裂縫處纖維與基體界面拉拔滑移做功也增加,更能有效地發(fā)揮纖維的阻裂增韌和耗能效用[2] RAMAKRISHNAN V Performance characteristics and appli4.2纖維摻量對(duì)裂后韌性指標(biāo)的影響cation of high-performance polyolefin fiber reinforced concretes由表4看出,隨著纖維摻量增加,板裂后韌性指[c]/Proceedings of the Third CANMET/ACL InternationalConference, SP-171. Detroit: American Concrete Institute標(biāo)To-1(n)明顯提高.對(duì)于纖維長(zhǎng)度38,48,60mm1997:671-692的FC30系列試件,纖維摻量為9kg/m3時(shí)在撓度3] GOPALRATNAM VS, SHAHSP, BATSON G B,etl.Frac為258。處的裂后韌性指標(biāo)T2-1(n)比摻量為ture toughness of fiber reinforced concrete[J]. ACI Materials6kg/m3時(shí)分別提高約43%,19%和15%比摻量為Journal,1991,88(4);339-353.3kg/m3時(shí)分別提高約170%,151%和94%[4 BANTHIA中國(guó)煤化工fexuralcharacterizat對(duì)于纖維長(zhǎng)度38,48,60mm的FC40系列試CNMHG1):48-57.件,纖維摻量為9kg/m2時(shí)在撓度為25δ處的裂后(下轉(zhuǎn)第16頁(yè))16建筑材料學(xué)報(bào)第18卷[5] JUST A, MIDDENDORF B Microstructure of high-strength2007,37(2):221-230.foam concrete [J]. Materials Characterization, 2009, 60(7): [7] RAMAMURTHY K, KUNHANANDAN NAMBIAR E K741-748.INDU SIVA RANJANI G. A classification of studies on prop-[6] NAMBIAR E KK, RAMAMURTHY K Air-void characteri-erties of foam concrete[J]. Cement and Concrete Compositessation of foam concrete [J]. Cement and Concrete Research2009,31(6):388-396.上接第11頁(yè))[5] American Society for Testing and Materials, Standard C1550Is World, 2007(9):42-49. (in Chinese)03a, standard test method for flexural toughness of fiber[7]鞠楊,劉紅彬陳健等超高強(qiáng)度活性粉末混凝土的韌性與表forced concrete( using centrally loaded round panel)[S].征方法[].中國(guó)科學(xué),2009,39(4):793-808Conshohocken: ASTM Committee, 2003.JU Yang, LIU Hongbin, CHEN Jian, et al.[6]沈榮熹聚烯烴粗纖維增強(qiáng)混凝土的性能及應(yīng)用[混凝土世test界,2007(9):42-49trength RPC[]. Science China, 2009, 39(4): 793-808( in ChiShen Rongxi. The performance and application of fiber rein-forced concrete with polyolefin[J. Building Decoration Materi中國(guó)煤化工CNMHG