冻融时引气剂对新老混凝土黏结面劈裂抗拉性能

采用新老混凝土黏结复合立方体试件，通过快速冻融试验，对在界面剂和新混凝土中掺加引气剂的新老混凝土黏结面的冻融劈裂抗拉性能进行了试验研究，探讨了冻融循环次数、引气剂、黏结面粗糙度和界面剂类型等对黏结面劈裂抗拉强度的影响。界面的粗糙度为0.23～6.90mm，界面剂选用掺加1％引气剂的水泥净浆、水泥砂浆和同时掺加10％UEA膨胀剂的水泥净浆。试验结果表明，在界面剂和新混凝土中掺加引气剂可显著提高新老混凝土黏结面的抗冻融性能，在同样条件下，黏结面的抗冻融性能可提高一倍以上，与未掺加引气剂的新老混凝土黏结面相比，黏结面的劈裂抗拉强度随冻融循环次数的增加而降低趋势变缓。根据试验，适当的粗糙度和掺加引气剂的水泥砂浆界面剂对新老混凝土黏结面的抗冻融性能有较好的改善作用。

Experimental study on influence of cyclic freeze-thaw on tensile strength of bonding interface between fresh and old concrete mixed with air-entraining agent

The tensile strength of bonding interface between saturated fresh and old concrete after accelerated cyclic freeze-thaw is experimentally studied by splitting test. The fresh concrete and adhesive agent are mixed with air-entraining agent. The effects of freeze-thaw cycles, air-entraining agent, roughness of bonding surfaces and adhesive agent, including cement paste, cement mortar and cement paste mixed with 10% UEA expansive agent, on tensile strength are investigated. The experimental results show that the strength of bonding interface will be remarkably improved if adhesive agent and fresh concrete are mixed with air-entraining agent. Furthermore, the reduction of splitting strength of bonding interface due to the increase of freeze-thaw cycles will decrease if the air-entraining agent is adopted. It is concluded that appropriate roughness in improving the split tensile strength of bonding surfaces and adoption of air-entraining agent are effective of bonding interface.