冻融循环与硫酸盐侵蚀共同作用下再生混凝土的微观结构研究

摘要/Abstract

摘要： 采用快冻法,将再生骨料取代率为30%的混凝土分别置于3%Na₂SO₄、5%Na₂SO₄、10%Na₂SO₄(均为质量分数)溶液以及水中进行冻融循环试验,测试再生混凝土质量损失率、相对动弹性模量变化、抗压强度损失率,并利用电子显微镜、能谱仪和X射线衍射等方法分析再生混凝土损伤层的微观结构,以超声波平测法确定损伤层厚度,引入侵蚀系数对以损伤层厚度为评价指标的损伤度进行优化。结果表明,当冻融循环为0~200次、Na₂SO₄溶液浓度大于5%时,抗压强度侵蚀系数始终小于1,即Na₂SO₄溶液对再生混凝土宏观力学性能损伤的促进作用明显,而对微观结构损伤的抑制作用明显。在再生混凝土冻融循环初期,以冻融侵蚀为主;冻融循环后期,以硫酸盐化学侵蚀为主,再生混凝土经化学侵蚀后生成钙矾石和石膏等膨胀产物,并出现膨胀裂缝,在冻融循环作用下裂缝迅速扩展,损伤层厚度增加。以损伤层厚度为评价指标的损伤度经优化后准确性至少提高了26.33%。

关键词: 再生混凝土, 冻融循环, 硫酸盐侵蚀, 微观结构, 损伤度

Abstract: The concretes with recycled aggregate mass replacement rate of 30% were placed in 3%Na₂SO₄, 5%Na₂SO₄, 10%Na₂SO₄ (3%, 5%, 10%, mass fraction) solution and water for freeze-thaw cycles test by quick freezing method. The mass loss rate, relative dynamic elastic modulus change and compressive strength loss rate of recycled aggregate concrete were tested. The microstructure of the damaged layer of recycled aggregate concrete was analyzed by electron microscope, energy spectrometer and X-ray diffraction. The thickness of the damaged layer was determined by ultrasonic flat measurement method, and the erosion coefficient was introduced to optimize the damage degree with the thickness of the damaged layer as the evaluation index. The results show that: when freeze-thaw cycles is 0~200 times and the concentration of Na₂SO₄ solution is greater than 5%, the erosion coefficient of compressive strength is always less than 1, in other ways, Na₂SO₄ solution has obvious promoting effect on the macroscopic mechanical performance damage of recycled aggregate concrete, but has obvious inhibitory effect on the microstructure damage. In the early stage of freeze-thaw cycles of recycled aggregate concrete, freeze-thaw erosion is the main factor. In the later stage of freeze-thaw cycles, sulfate chemical erosion is the main factor. After chemical erosion, expansion products such as ettringite and gypsum are formed in recycled aggregate concrete, and they lead to expansion cracks. The cracks expand rapidly under the action of freeze-thaw cycles, and the thickness of the damaged layer increases. The accuracy of the damage degree based on the thickness of the damage layer as the evaluation index is improved by at least 26.33% after optimization.

Key words: recycled aggregate concrete, freeze-thaw cycle, sulfate attack, microstructure, damage degree

中图分类号:

TU528.1

齐晓, 肖前慧, 邱继生, 刘书林. 冻融循环与硫酸盐侵蚀共同作用下再生混凝土的微观结构研究[J]. 硅酸盐通报, 2023, 42(4): 1194-1204.

QI Xiao, XIAO Qianhui, QIU Jisheng, LIU Shulin. Microstructure of Recycled Aggregate Concrete under Combined Action of Freeze-Thaw Cycles and Sulfate Attack[J]. BULLETIN OF THE CHINESE CERAMIC SOCIETY, 2023, 42(4): 1194-1204.

参考文献

[1] GUPTA C K. Strength characteristics of concrete made with demolition waste as coarse aggregate[J]. Proceedings of the International Conference on Recent Development in Structural Engineering, 2011: 364-378.
[2] SHI D D, SHI Q X. Study on mechanical properties and mesoscopic numerical simulation of recycled concrete[J]. Sustainability, 2022, 14(19): 12125.
[3] 陈守开, 白卫峰, 郑永杰, 等. 再生骨料替代率对混凝土单轴压缩力学性能的影响[J]. 应用基础与工程科学学报, 2022, 30(3): 764-775.
CHEN S K, BAI W F, ZHENG Y J, et al. Effect of replacement rate of recycled aggregate on mechanical properties of concrete under uniaxial compression[J]. Journal of Basic Science and Engineering, 2022, 30(3): 764-775 (in Chinese).
[4] BIAN J W, ZHANG W B, SHEN Z Z, et al. Analysis and optimization of mechanical properties of recycled concrete based on aggregate characteristics[J]. Science and Engineering of Composite Materials, 2021, 28(1): 516-527.
[5] DE OLIVEIRA M B, VAZQUEZ E. The influence of retained moisture in aggregates from recycling on the properties of new hardened concrete[J]. Waste Management, 1996, 16(1/2/3): 113-117.
[6] 戴俊, 翟惠慧, 黄斌斌, 等. 冻融循环下再生混凝土力学性能研究[J]. 混凝土, 2022(5): 61-64+68.
DAI J, ZHAI H H, HUANG B B, et al. Study on mechanical properties of recycled concrete after freeze-thaw cycles[J]. Concrete, 2022(5): 61-64+68 (in Chinese).
[7] 邓祥辉, 高晓悦, 王睿, 等. 再生混凝土抗冻性能试验研究及孔隙分布变化分析[J]. 材料导报, 2021, 35(16): 16028-16034.
DENG X H, GAO X Y, WANG R, et al. Study on frost resistance and pore distribution change of recycled concrete[J]. Materials Reports, 2021, 35(16): 16028-16034 (in Chinese).
[8] 江洲. 再生粗骨料旧砂浆附着率对混凝土硫酸盐侵蚀性能影响[J]. 交通科技, 2018(5): 125-129.
JIANG Z. Effect of adhesion rate of recycled coarse aggregate mortar on the sulfate attack performance of concrete[J]. Transportation Science & Technology, 2018(5): 125-129 (in Chinese).
[9] 顾彦, 耿欧, 李大贺. 再生粗骨料混凝土硫酸盐侵蚀的损伤模型研究[J]. 混凝土, 2022(2): 34-37.
GU Y, GENG O, LI D H. Study on sulfate damage model of recycled coarse aggregate concrete[J]. Concrete, 2022(2): 34-37 (in Chinese).
[10] 陶喆, 王瑞骏, 李阳, 等. 受硫酸盐侵蚀的再生混凝土耐久性研究[J]. 长江科学院院报, 2019, 36(9): 136-141.
TAO Z, WANG R J, LI Y, et al. Durability of recycled concrete subjected to sulphate erosion[J]. Journal of Yangtze River Scientific Research Institute, 2019, 36(9): 136-141 (in Chinese).
[11] 李大贺. 再生粗骨料混凝土抗硫酸盐侵蚀性能研究[D]. 徐州: 中国矿业大学, 2019.
LI D H. Study on sulfate corrosion resistance of recycled coarse aggregate concrete[D]. Xuzhou: China University of Mining and Technology, 2019 (in Chinese).
[12] 刘金龙, 韩建德, 王曙光, 等. 硫酸盐侵蚀与环境多因素耦合作用下混凝土耐久性研究进展[J]. 混凝土, 2014(9): 33-40.
LIU J L, HAN J D, WANG S G, et al. Overview of concrete durability under sulfate attack and multi-factor coupling effects[J]. Concrete, 2014(9): 33-40 (in Chinese).
[13] 刘辉. 硫酸盐侵蚀与冻融循环双重因素对混凝土耐久性的影响[D]. 成都: 西南交通大学, 2013.
LIU H. On sulfate attack and freeze-thaw cycles double factors influence on durability of concrete[D]. Chengdu: Southwest Jiaotong University, 2013 (in Chinese).
[14] 赵高升, 何真, 杨华美. 冻融循环和碳化交替作用下的混凝土耐久性[J]. 武汉大学学报(工学版), 2013, 46(5): 604-609.
ZHAO G S, HE Z, YANG H M. Study of concrete durability under alternative effect of carbonation and freeze-thaw cycles[J]. Engineering Journal of Wuhan University, 2013, 46(5): 604-609 (in Chinese).
[15] 宿晓萍, 张利, 郭金辉. 单盐侵蚀与冻融循环作用下混凝土耐久性能试验研究[J]. 工业建筑, 2014, 44(9): 110-113+6.
SU X P, ZHANG L, GUO J H. Experimental study of concrete durability under the action of single salt corrosion and freezing-thawing cycles[J]. Industrial Construction, 2014, 44(9): 110-113+6 (in Chinese).
[16] 中华人民共和国住房和城乡建设部. 普通混凝土长期性能和耐久性能试验方法标准: GB/T 50082—2009[S]. 北京: 中国建筑工业出版社, 2009.
Ministry of Housing and Urban-Rural Development of the People's Republic of China. Standard of test methods for long-term performance and durability of ordinary concrete: GB/T 50082—2009[S]. Beijing: China Construction Industry Press, 2009 (in Chinese).
[17] 中国工程建设标准化协会. 超声法检测混凝土缺陷技术规程: CECS 21—2000[S]. 北京: 中国城市出版社, 2000.
China Association for Standardization of Engineering Construction. Technical specification for ultrasonic detection of concrete defects: CECS 21—2000[S]. Beijing: China City Press, 2000 (in Chinese).
[18] 李星星, 王思敬, 肖锐铧, 等. 硫酸钠溶液在降温结晶过程中的盐胀与冻胀[J]. 岩土工程学报, 2016, 38(11): 2069-2077.
LI X X, WANG S J, XIAO R H, et al. Saline expansion and frost heave of sodium sulfate solution during cooling crystallization process[J]. Chinese Journal of Geotechnical Engineering, 2016, 38(11): 2069-2077 (in Chinese).
[19] 崔正龙, 大芳賀義喜, 北迁政文, 等. 再生混凝土的冻融循环试验研究[J]. 建筑材料学报, 2007, 10(5): 534-537.
CUI Z L, OHAGA Y K, KITATSUJI M H, et al. Experimental research on freezing-thawing cycle of recycled aggregate concrete[J]. Journal of Building Materials, 2007, 10(5): 534-537 (in Chinese).
[20] 贾文亮, 李昊, 张琴. 硫酸盐环境下再生骨料混凝土的抗冻性能[J]. 硅酸盐通报, 2016, 35(6): 1816-1820.
JIA W L, LI H, ZHANG Q. Frost resistance property of recycled aggregate concrete under sulfate environment[J]. Bulletin of the Chinese Ceramic Society, 2016, 35(6): 1816-1820 (in Chinese).