摘要
研究了掺加木质素磺酸钙(calciumlignosulfonate,CLS)后水泥净浆体系的水化速度、水化产物生成量,以及硬化水泥石的微观结构及孔隙结构的变化.CLS大幅度延缓了水泥水化放热,降低了水化速度,使3～10 h内水泥的水化程度减少,但对1 d后的水化程度影响不大且能促进水泥的后期水化.X射线衍射分析表明高掺量CLS促进硬化水泥中生成钙矾石,抑制水化硅酸钙(CSH)的早期生成,但对CSH的后期生成无影响.扫描电镜观察发现:CLS的掺加抑制了水化产物晶体的生长,使CSH凝胶难以形成空间网架,钙矾石晶体变得纤细.随CLS掺量的增加,硬化水泥中总孔隙容积增加,30 nm以上的孔隙显著减少,10 nm以下的微孔数量大幅度增加,平均孔径减小.掺加CLS的水泥浆体水化产物晶体发育不完全,硬化水泥的孔隙容积明显增加,是硬化水泥28d龄期内抗压强度显著下降的主要原因.
Hydration rates and hydration products of cement paste, microstructures and pore structures of hydrated cement blended with calcium lignosulfonate (CLS) were studied. The heat-release of cement hydration is delayed remarkably by CLS and the hydration rate is retarded, resulting in reducing the hydration degree during the first 3-10 h. However, CLS has little effect on hydration degree of cement paste after 1 d and can promote the long-term hydration. X-ray diffraction analysis shows that CLS can promote the growth of ettringite and restrain the growth of CSH at early-age, while the long-term growth of CSH is not be affected. According to the scanning electron microscope observation, the crystal-growth of hydration products is restrained by CLS with the result that CSH cannot form grid structure and the ettringite crystals become finer. Nevertheless, the composition of ettringite is not changed. The total pore volume of hydrated cement increases with the increasing of CLS dosage, the proportion of pore with a diameter over 30 nm decreases obviously and the proportion of pore with a diameter less than 10 nm increases sharply. The average pore diameter of hydrated cement blended with CLS decreases. The incomplete growth of hydrate crystals and the remarkable increase of pore volume in hydrated cement caused by air-entraining properly of CLS are the main reasons that lead to the strength decreasing of cement paste blended with CLS within 28 d.
出处
《硅酸盐学报》
EI
CAS
CSCD
北大核心
2005年第4期477-483,共7页
Journal of The Chinese Ceramic Society
基金
广东科技计划(2004B10301012)资助项目。
关键词
木质素磺酸钙
水泥水化
水化产物
微观结构
孔隙结构
Calcium compounds
Crystal growth
Hydration
Microstructure
Pore size
Scanning electron microscopy
X ray diffraction analysis
