关键词: 弱碱;硫酸盐侵蚀;二水石膏;K值法;线扫描

Abstract: Hardened cement paste immersed in sodium sulfate and weak alkaline solution for 210 d had been investigated.The as-prepared samples were characterized by X -ray diffraction (XRD), scanning electron microscopy(SEM) and energy dispersive spectrometer(EDS).The contents of dihydrate gypsum which cement paste samples immersed in 0％, 5％ and 10％ Na2 SO4 solution were calculated by using K value in X-ray diffraction ( XRD), the contents of free and total sulfate ion in the samples were determined by spectrophotometry .The results showed that the contents of dihydrate gypsum in the samples increased significantly with the increase of Na 2 SO4 concentration in the attack solution, the contents of dihydrate gypsum that samples immersed in the 5％ and 10％ Na2 SO4 solution were 3.291％and 3.957％, respectively.It was found that there was obvious dihydrate gypsum in the sample which soaked in 10％ Na2 SO4 solution.We found that samples had a "high sulfur distribution"on the near surface by Line scan mode in EDS.It was found by spectrophotometry that the free sulfate ion content of the samples immersed in 5％ and 10％ Na2 SO4 solution was 81 times and 85 times of that of the sample immersed in water, respectively.

Key words: weak alkaline;sulfate attack;dihydrate gypsum;K value;line scan