Studies On Ammonia Emission Behavior Of Concrete Admixtures In New Blank Houses

OBJECTIVE①Ammonia emission in 3 kinds of concrete admixtures sold in Lanzhou, totally 33 samples including 15 anti-freezing admixture, 10 water-reducing admixture and super plasticizer, and 8 hardening accelerator, was measured respectively. The effect of pH on ammonia emission was further observed.②Indoor ammonia concentration was measured in new blank houses in Lanzhou and indoor ammonia pollution status was thus assessed. The source of indoor ammonia was then explored. Furthermore, the effects of indoor temperature, relative humidity and the built time of the houses on indoor ammonia concentration were investigated respectively.METHODS 1 Spot investigation:①Ammonia emission quantity was detected according to titration method recommended by Chinese national standard of GB 18588-2001.②40 new blank houses in Lanzhou with the built time of 6 and 12 months were recruited. Indoor ammonia was detected by RT-3 type ammonia monitor. 2 Spot simulation: One new blank house with aera of 18 m~2 was chosen to continuously determine indoor ammonia concentration for 30 days.RESULTS 1 Spot investigation:①Out of the 33 tested samples, 12 samples (36.4%) exceeded the control standard of 0.10% (wt/wt), the others (63.6%) qualified . Ammonia emission quantity of water-reducing admixture, anti-freezing admixture, hardening accelerator was 0.071%, 0.070% and 0.069%, respectively. No statistical difference was found in 3 kinds of the tasted concrete admixtures. (2) Ammonia emission quantity was 0.012%, 0.024% and 0.081% at pH=9, pH=11, pH=13, respectively. Ammonia emission increased with increasing pH, especially for those admixtures containing carboxylate.③The arithmetic mean of indoor ammonia was 0.147 mg/m~3. Out of 40 new blank houses, 8 (20%) exceeded the national control standard of 0.20 mg/m~3. The fraction of new blank houses with an ammonia concentration in the reference levels of≤0.10, 0.10～0.20 and >0.20 mg/m~3 was 37.5%, 42.5% and 20.0% respectively. Statistical difference in indoor ammonia concentration was found between 6-month blank houses and 12-month houses (P<0.05). 2 Spot simulation: Ammonia concentration increased with increasing temperature and decreasing relative humidity. Indoor ammonia concentration change is not evident after short ventilation.CONCLUSIONS①The quality of concrete admixtures tested was far from satisfactory. Meanwhile, potential health risk arising from poor quality concrete admixtures should cause more attention.②The concrete admixtures such as antifreezer in wall body are probably the chief source of indoor ammonia. Temperature and relative humidity affect indoor ammonia level. Regular ventilation is the most effective approach to eliminate indoor ammonia.