多年冻土基础混凝土早强防冻剂的选用和使用方法

青藏直流线路工程所经地段在青海境内大部分属多年冻土区,为减少对多年冻土的扰动,选择在冬期施工更能保证冻土基础的稳定性;为防止低温下使混凝土基础遭受冻害,一是要添加早强防冻剂,早强防冻剂的选择应按外界温度、钢筋防腐要求来选择;二是必须严格控制早强防冻剂的掺量;三是要保证混凝土在达到抗冻临界强度前的早期养护温度;四是必须保证早强防冻剂质量,要使用＂三证＂齐全的产品;青藏直流线路基础施工按外界温度的变化分别改变防冻剂掺量、控制水温、采用温棚养护等综合措施,使混凝土达到了设计强度。

Selection of Concrete Early Strengthen Freezing Proof Agent and Its Application Method in Permafrost Layer

Qinghai-Tibet DC transmission line engineering passing through permafrost area in Qinghai province,in order to reduce interference of permafrost area,the construction should be implemented in winter to ensure stability of permafrost foundation.In order to prevent the concrete foundation from frozen injury under low temperature,firstly,the early strengthen freezing proof agent should be added,and it should be selected according to outside temperature and concrete anticorrosion requirement;secondly,the adding quantity of early strengthen freezing proof agent should be strictly controlled;thirdly,the concrete early maintenance temperature before it reaching the antifreeze critical strengthen should be ensured;fourthly,the quality of the early strengthen freezing proof agent should be ensured,and the product with ＇three certificates＇ should be used.During the foundation construction of Qinghai-Tibet DC transmission line,the comprehensive measures of adding quantity of freezing proof agent,water temperature control,and green house maintenance has been changed according to outside temperature,and it achieves the purpose of improving concrete early strengthen,ensures concrete maintenance temperature before reaching the freezing proof critical strengthen,and finally it makes concrete strengthen continuous growth under the freezing proof stipulated negative temperature,thus achieves the designed strengthen.