| 复合盐侵蚀再生混凝土耐久性能退化试验研究 |
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| 引用本文： | 侯泽宇,王家滨,郭庆军,李恒,张凯峰.复合盐侵蚀再生混凝土耐久性能退化试验研究[J].硅酸盐通报,2021,40(11):3617-3626. |
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| 作者姓名： | 侯泽宇 王家滨 郭庆军 李恒 张凯峰 |
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| 作者单位： | 1.西安工业大学建筑工程学院,西安 710021; 2.西安工业大学,西安市军民两用土木工程测试技术与毁损分析重点实验室,西安 710021; 3.中建西部建设北方有限公司,西安 710065 |
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| 基金项目： | 国家自然科学基金(51908440) |
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| 摘 要： | 我国西北地区土壤及其地下水中含有大量侵蚀性离子,造成了再生混凝土结构耐久性能快速退化,严重制约着再生混凝土在主体结构中的应用。基于西北地区耐久性环境中侵蚀离子组成及区域气候环境特征,以7.5%(质量分数)MgSO4-7.5%(质量分数)Na2SO4-5%(质量分数)NaCl为侵蚀介质,采用干湿交替方式,开展复合盐侵蚀再生混凝土耐久性能退化试验研究。以粉煤灰、矿渣、硅灰、偏高岭土等活性矿物掺合料取代水泥,研究矿物掺合料搭配方式对再生混凝土耐久性能影响。采用XRD、FTIR、TG-DSC及SEM、EDS等表征手段,分析侵蚀产物矿物组成、含量及微结构变化,研究复合盐侵蚀再生混凝土损伤过程。随着干湿交替次数增加,再生混凝土相对动弹性模量、质量变化率、相对抗压强度、相对劈裂抗拉强度及损伤层厚度的变化规律与矿物掺合料搭配方式有着显著的相关性。随着侵蚀离子的不断扩散,混凝土碱度降低,在表面依次形成了以水镁石、石膏及钙钒石为主要产物的致密侵蚀产物层,短暂阻碍了侵蚀离子进一步扩散。随着侵蚀产物不断堆积及无胶凝性水化硅酸镁的形成,在膨胀应力及盐结晶压力共同作用下,再生混凝土表面大量剥蚀并开裂,耐久性能快速退化。
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| 关 键 词： | 再生混凝土 耐久性能 复合盐侵蚀 干湿交替 矿物掺合料 退化机理 |
| 收稿时间： | 2021-06-09 |
Experimental Study on Durability Degradation of Recycled Aggregate Concrete by Compound Salt Corrosion |
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| HOU Zeyu,WANG Jiabin,GUO Qingjun,LI Heng,ZHANG Kaifeng.Experimental Study on Durability Degradation of Recycled Aggregate Concrete by Compound Salt Corrosion[J].Bulletin of the Chinese Ceramic Society,2021,40(11):3617-3626. |
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| Authors: | HOU Zeyu WANG Jiabin GUO Qingjun LI Heng ZHANG Kaifeng |
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| Affiliation: | 1. School of Civil & Architectural Engineering, Xi'an Technology University, Xi'an 710021, China; 2. Xi'an Key Laboratory of Civil Engineering Testing and Destruction Analysis on Military-Civil Dual Use Technology (XATU), Xi'an Technology University, Xi'an 710021, China; 3. China Construction West Construction North Co., Ltd, Xi'an 710065, China |
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| Abstract: | There are a great number of corrosion ions in the soil and groundwater of Northwest China, which causing rapid degradation of durability of recycled aggregate concrete structures severely limit the application of recycled aggregate concrete in modern concrete structures. Based on the composition of corrosive ions and the characteristics of regional climate and environment in the durability environment of Northwest China, the experiment of durability degradation of recycled aggregate concrete subjected to compound salts was carried out by dry-wet cycles method with 7.5% (mass fraction) MgSO4-7.5% (mass fraction) Na2SO4-5% (mass fraction) NaCl as the corrosive medium. The effects of mineral admixtures on durability of recycled aggregate concrete were studied by using active mineral admixtures such as fly ash, slag, silica fume and metakaolin instead of cement. And then, the mineral composition and relative content of mineral phases, and microstructures of corrosion products were characterized by XRD, FTIR, TG-DSC, SEM and EDS, respectively. In addition, the durability degradation process of recycled aggregate concrete was suggested. As the dry-wet cycles increase, the relative dynamic elastic modulus, mass change rate, relative compressive strength, relative splitting tensile strength, and damage depth are significantly related to the collocation of mineral admixtures. With the corrosion ions diffusing into concrete, the alkalinity of concrete decreases and the dense corrosion layers with brucite, gypsum and ettringite as the mainly corrosion products are successively formed on the surface of concrete, which temporarily hinders the further diffusion of corrosion ions. With the continuous accumulation of corrosion products and the formation of non-gelling products, the surface of recycled aggregate concrete is spalled and cracked under the combined action of expansion stress and salt crystallization pressure. The durability of recycled aggregate concrete is rapidly degraded. |
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| Keywords: | recycled aggregate concrete durability compound salt corrosion dry-wet cycle mineral admixture degradation mechanism |
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