不同有效碱含量下纳米氧化铝对水泥石固、液相组成的影响

Influence of Alumina Nano-Particles on Pore Solution and Solid Phase of Cement Paste at Different Equivalent Alkali Contents

研究了水泥中有效碱含量为0.58%、1.25%条件下纳米氧化铝（取代3%的水泥）对水泥石固相、液相组成的影响。有效碱含量为0.58%条件下,纳米氧化铝溶解所释放的Al进入孔溶液,参与形成单硫型水化硫铝酸钙,同时降低孔溶液中S（硫）元素浓度。形成的单硫型水化硫铝酸钙可以向水化碳铝酸钙和半碳型水化碳铝酸钙等更加稳定的AFm相转化。AFm相溶解度是孔溶液Al浓度的控制因素,3%的纳米氧化铝并不能提高Al浓度。部分溶解的Al进入C-S-H中,也限制了孔溶液Al浓度的提高和AFm相数量的增加。有效碱含量为1.25%时,液相碱度的提高导致AFm相溶解度增大,使水化后期孔溶液中Al、S浓度同时提高,但Al浓度不超过0.3 mmol/L,AFm相仍然是孔溶液Al浓度的控制因素。

This paper reports the influence of alumina nano-particles on the compositions of pore solution and solid phases of cement paste at different alkali contents（Na_2O_（eq）： 0.58% and Na_2O_（eq）： 1.25% by mass of cement）. At a low alkali content（i.e., Na_2O_（eq）： 0.58%）, alumina nano-particles dissolve and release Al species into the pore solution due to the formation of the more monosulfate, leading to a decreased S concentration in the pore solution. The formed monosulfate can transform into more stable AFm（calcium silicate hydrate） phases, such as monocarbonate and hemicarbonate. The concentration of Al in pore solution is controlled by the solubility of AFm phases, and the presence of 3% alumina nano-particles（by mass of cement） only causes a slightly increase in Al concentration in pore solution. At a high alkali content in cement（i.e., Na_2O_（eq）： 1.25%）, the increase of alkalinity increases the solubility of ettringite and AFm phases, and reduces the saturation degree of these phases. The increased solubility of ettringite and AFm phases leads to increases in Al and S concentrations simultaneously in pore solution, especially at latter ages. In this case, the solubility of AFm phases is still a factor controlling Al species concentration in pore solution.