膨胀剂对混凝土早期基本徐变的影响

Effect of Expansive Additives on Basic Creep of Early-Age Concrete

研究了自制CaO和MgO膨胀剂的掺加对C60自密实混凝土力学、变形性能及基本徐变的影响,并将徐变测试结果与fib 2010模型计算结果进行了对比.结果表明:6%CaO膨胀剂、6%(CaO+MgO)膨胀剂和10%(CaO+MgO)膨胀剂的掺加对C60自密实混凝土的抗压强度和弹性模量影响较小,但会显著降低混凝土自收缩,并增大其基本徐变变形;混凝土的徐变度和徐变系数基本随着膨胀剂总掺量或CaO膨胀组分掺量的提高而增大;当CaO膨胀剂掺量较低时,混凝土徐变度实测结果与fib 2010模型计算结果吻合度较好,CaO膨胀剂掺量较高时,混凝土徐变发展趋势明显高于模型计算结果,复合掺加MgO膨胀剂后,随着持荷时间的延长,混凝土徐变进一步增加.对于CaO膨胀剂掺量较高以及复合掺加MgO膨胀剂的混凝土,有必要研究膨胀对徐变随时间发展系数的影响,进而对模型进行修正.

The effects of CaO-based and MgO-based expansive additives on the mechanical,deformation properties and basic creep of C60 self-compacting concrete were studied,and the test results of creep were compared with the calculation results of the fib 2010 model. The results show that the incorporation of 6% CaO-based expansive additive and 6%,10% CaO/MgO composite expansive additives has little effect on the compressive strength and elastic modulus of C60 self-compacting concrete,but significantly reduces the autogenous shrinkage and increases the basic creep. The concrete creep compliance and creep coefficient basically increase with the increase of the total amount of expansive additives and the increase of CaO-based expansive additive. Under the low content of CaO-based expansive additive,the test results of creep compliance of concrete are in good agreement with the calculation results of fib 2010 model,but under the condition of high content of CaO-based expansive additive,the development trend of concrete creep is significantly higher than that of the calculation results. When mixing with MgO,the creep further increases with the increase of load holding duration. For the concrete incorporating high content of CaO-based and MgO-based expansive additive,it is necessary to study the influence of expansion on the development of creep with time,and then to modify the model.