MgO和CaO对碱矿渣混凝土抗碳化性能的影响

摘要/Abstract

摘要： 与普通硅酸盐水泥(OPC)混凝土相比,碱矿渣混凝土(AASC)的抗碳化性能较差。为了提高AASC的抗碳化性能,本文采用MgO和CaO代替部分矿渣制备AASC,研究了加速碳化环境下掺MgO和CaO的AASC在不同碳化龄期的抗压强度和碳化深度,并结合 X 射线衍射(XRD)、同步热分析(TG-DTG)和扫描电镜-能谱(SEM-EDS)等技术分析了MgO和CaO对AASC抗碳化性能的改性机理。结果表明,MgO和CaO分别促进了AASC中Mg-Al水滑石和Ca-Al层状结构的生成,这两种水化产物在碳化过程中会吸收和消耗CO₂,缓解C-S-H的碳化分解。此外,加速碳化后,掺入MgO的AASC中有碳酸钙镁和碳酸镁生成,掺入CaO的AASC中碳酸钙的量明显增多,这些碳化产物可有效填充孔隙,阻碍CO₂向内部进一步的扩散。因此,在碳化环境下,掺MgO和CaO的AASC抗压强度保留率更高,碳化深度更低,表现出更好的抗碳化性能。

关键词: 碱矿渣混凝土, 氧化镁, 氧化钙, 碳化, 微观结构

Abstract: Compared with ordinary Portland cement (OPC) concrete, alkali-activated slag concrete (AASC) has poor carbonization resistance. In this paper, part of slag was replaced by MgO and CaO to prepare AASC to improve its carbonization resistance. The compressive strength and carbonization depth of AASC seeded with MgO and CaO under accelerated carbonization environment at different carbonization ages were studied. The modification mechanism of MgO and CaO on the carbonization resistance of AASC was analyzed by X-ray diffraction (XRD), simultaneous thermal analysis (TG-DTG) and scanning electron microscopy-energy dispersive spectrometer (SEM-EDS). The results show that MgO and CaO promotes the formation of Mg-Al hydrotalcite and Ca-Al layered structure in AASC, respectively. These two hydration products absorb and consume CO₂ during the carbonization process, then alleviate the decomposition of C-S-H caused by carbonization. In addition, after accelerated carbonization, calcium magnesium carbonate and magnesium carbonate are formed in the AASC blended with MgO, and the amount of calcium carbonate in the AASC blended with CaO increase significantly. These carbonized products effectively fill the pores and hinder the further diffusion of CO₂ into the interior of AASC. Therefore, under the carbonization environment, the AASC blended with MgO and CaO has a higher compressive strength retention rate, a lower carbonization depth, and a better carbonization resistance than pure AASC.

Key words: alkali-activated slag concrete, magnesium oxide, calcium oxide, carbonization, microstructure

中图分类号:

TU528

郑昊, 梁咏宁, 詹建伟, 季韬. MgO和CaO对碱矿渣混凝土抗碳化性能的影响[J]. 硅酸盐通报, 2021, 40(8): 2564-2573.

ZHENG Hao, LIANG Yongning, ZHAN Jianwei, JI Tao. Effects of MgO and CaO on the Carbonization Resistance of Alkali-Activated Slag Concrete[J]. BULLETIN OF THE CHINESE CERAMIC SOCIETY, 2021, 40(8): 2564-2573.

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