海水海砂制备活性粉末混凝土的碳化机理  

Carbonization Mechanism of Reactive Powder Concrete with Sea-water and Sea Sand

作　　者：李田雨[1] 刘小艳[1] 张玉梅[1] 熊传胜 曹文凯 李伟华 LI Tianyu;LIU Xiaoyan;ZHANG Yumei;XIONG Chuansheng;CAO Wenkai;LI Weihua(College of Mechanics and Materials,Hohai University,Nanjing 210098,China;College of Civil Engineering,Qingdao University of Technology,Qingdao 266033,China;School of Chemical Engineering and Technology,Sun Yat-Sen University,Zhuhai 519000,China)

机构地区：[1]河海大学力学与材料学院,南京210098 [2]青岛理工大学土木工程学院,青岛266033 [3]中山大学化学工程与技术学院,珠海519000

出　　处：《材料导报》2020年第8期42-50,共9页Materials Reports

基　　金：河海大学中央高校基本科研业务费项目(2017B05614);国家自然科学基金(51709253,51879093)。

摘　　要：采用丰富的海砂资源制备海水海砂活性粉末混凝土并研究其抗碳化性。通过硬度计研究碳化不同阶段混凝土的表面硬度,用酸度计测试其pH变化规律,用XRD和SEM研究其微观成分和形貌变化。研究发现:(1)采用指示剂法测得所有混凝土28 d碳化深度为0,通过SEM扫描电镜测试发现实际碳化发生在混凝土表面(50~100μm)。(2)碳化28 d后混凝土孔隙液pH明显降低,沿CO 2侵蚀方向混凝土孔隙液pH降低幅度呈下降趋势。在距混凝土表面3 mm内,pH变化幅度较大,最终pH均大于10.5,大于钝化膜完全破坏的临界值(9.88);标准养护的混凝土孔隙液的pH均大于11.50,大于钝化膜开始不稳定的临界值;使用海水海砂制备的混凝土孔隙液pH变化小于淡水河砂制备的混凝土。(3)碳化对混凝土的力学性能影响不大,但碳化腐蚀产物沉积在混凝土表面可以增加混凝土表面硬度;(4)海水海砂活性粉末海工混凝土的碳化实际上是CO 2与混凝土表层的Ca(OH)2、C-S-H凝胶、C3S、C2S以及Friedel’s盐反应,生成CaCO 3和无定型的水化SiO 2覆盖于原始混凝土表面,增加混凝土的抗碳化性。In this paper,the carbonation resistance of brine marine sand high performance concrete made from abundant sea sand resources was stu-died.The surface hardness of brine marine sand high performance concrete at different stages of carbonization was studied by means of the durometer,its microscopic composition and morphology were studied by XRD and SEM,and its pH variation was tested by a acidity meter.The results showed that:(1)The carbonation depth of brine marine sand high performance concrete was measured as 0 by using the indicator met-hod,and the actual carbonation depth was found to be within 50—100μm on the concrete surface by scanning electron microscope test.(2)After 28 days of carbonation,the pH of concrete pore solution decreased significantly,and the pH of concrete pore solution decreased along the direction of CO2 erosion.The larger pH variation is mainly concentrated within 3 mm from the surface,and the final pH is all above 10.5,greater than the critical value of passivation film disappearance(9.88).The pH of the standard curing specimens is all above 11.50,greater than the critical value of passivation film destruction.(3)Carbonization has little effect on the mechanical properties of brine marine sand high performance concrete,but the deposition of corrosion products on the surface of concrete can increase the surface hardness.(4)The carbonation of brine marine sand high performance concrete is actually the reaction of CO2 with Ca(OH)2,C-S-H gel,C3S,C2S and Friedel’s salt to generate CaCO3 and amorphous hydrated SiO2 covering the original concrete surface,increasing the carbonation resistance of concrete.

关 键 词：活性粉末混凝土 海砂 碳化 洛氏硬度 PH 

分 类 号：TV331[水利工程—水工结构工程]