为了揭示水泥与粉煤灰对减水剂的竞争吸附规律,采用分光光度法研究了SMF、FDN和ASP三种减水剂在此两种颗粒表面的吸附行为.结果表明,三种减水剂在胶凝颗粒表面的吸附均符合Langmuir等温吸附方程,属单分子层吸附.吸附量顺序均为:SMF>FDN>ASP.20℃时,SMF、FDN、ASP减水剂在水泥表面的饱和吸附量分别为12.95、11.35、3.83 mg/g,而在粉煤灰表面的饱和吸附量则分别为3.15、2.86、1.10 mg/g,表明水泥对减水剂的吸附强于粉煤灰对减水剂的吸附.减水剂在胶凝颗粒表面的吸附动力学也遵循Lang-muir吸附速率方程,SMF、FDN在水泥表面的平均吸附速率大干在粉煤灰颗粒表面的平均吸附速率,而ASP在两种胶凝颗粒表面的吸附速率较为接近.研究表明SMF、FDN将优先吸附在水泥颗粒表面,而ASP在水泥和粉煤灰表面的吸附选择性不高.
In order to reveal the competitive adsorption of superplasticizers on the cement and fly ash, the adsorption of SMF, FDN and ASP superplasticizer on these two particles was studied with spectrophotometry. Results show that the adsorption behavior on cement particles can be described with Langmuir isothermal adsorption equation, and characterized as monolayer adsorption. The sequence of adsorptive amount is as follows; SMF > FDN >ASP. The saturated adsorption capacities of SMF, FDN and ASP on cement are 12.95, 11. 35 and 3. 83 mg/g at 20 ℃, while those on fly ash are 3. 15, 2. 86 and 1. 10 mg/g respectively, indicating the adsorption of superplasticizers on cement is stronger than that on fly ash. The adsorption kinetics can be also characterized by Langmuir adsorption rate equation. The average adsorption rate of SMF, FDN on cement particles is larger than that on fly ash particles, while that of ASP on the two cementitious particles is close to each other. It is indicated that SMF and FDN will be preferentially adsorbed on cement particles, while the adsorption of ASP has lower selectivity on the cement and fly ash particles.
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