兰州市室内建筑用混凝土外加剂的氨释放水平

Ammonia Emission from Concrete Admixtures Sold in Lanzhou

目的调查兰州市建筑业普遍使用的3类混凝土外加剂氨释放量状况,考察碱性条件下外加剂氨释放量的变化规律。方法于2005年12月—2006年3月采用GB18588—2001《混凝土外加剂中释放氨的限量》标准推荐方法测定兰州市场上销售的防冻剂、减水剂、早强剂共33种外加剂氨释放量。结果在测定的33种外加剂样品中,有12种超过国家规定的氨释放量≤0.10%的质量标准,占样本总数的36.4%,最大氨释放量为0.136%,其余为合格产品,占63.6%。减水剂、防冻剂、早强剂氨释放量均值分别为0.071%,0.070%,0.069%,差异无统计学意义(P>0.05)。pH=9、pH=11、pH=13时混凝土外加剂氨释放量均值分别为0.012%,0.024%,0.081%,随着pH值的增大,氨释放量也随之增加,且pH值对羧酸类外加剂影响较磺酸类显著。结论兰州市室内建筑用混凝土外加剂氨释放量存在超标现象。较高的pH值会造成外加剂氨的快速释放,使得室内氨浓度迅速升高。

Objective To explore ammonia emission from concrete admixtures sold in Lanzhou. Methods Ammonia emission of 3 kinds of concrete admixtures, totally 33 samples including lS anti-freezing admixture, 10 water-redueing admixture and 8 early strength admixture, sold in Lanzhou were measured respectively. The effect of various pH values on ammonia emission was further observed. The amount of ammonia emission was detected according to titration method recommended by Chinese national standard of GB 18588-2001. Results Among 33 tested samples, ammonia emission of 12 samples （36.4%） exceeded the standard （0.10%）, the others（63.6% ）was qualified. The average amount of ammonia emission was 0.071%, 0.070%, 0.069% for water-reducing, admixture anti-freezing admixture, early strength admixture respectively,which showed no statistical difference （P〉 0.05）. The average amount of ammonia emission was 0.012%, 0.024% and 0.081% at pH values of 9, 11 and 13 respectively. Ammonia emission increased with the increasing pH values, especially for those admixtures containing carboxylatc. Conclusion Ammonia emission from concrete admixtures sold in Lanzhou exceed the standard in different degree.Higher pH value may accelerate the ammonia emission from concrete admixtures and cause higher concentration of ammonia in indoor air.