混凝土破损结构的补偿收缩修补砂浆

补偿收缩砂浆通常为预拌水泥基材料。在众多粉状组成成分中便含有膨胀剂,以死烧氧化钙(CaO)或硫铝酸钙(CSA)为代表的膨胀剂,在钢筋或粗糙混凝土基层摩擦力的限制作用下,在修补砂浆中产生压应力。由于CaO或CSA膨胀剂只有在有水的情况下才能水化,因此为保证使用效果,砂浆必须仔细养护,如不进行仔细的潮湿养护,修补工作很可能由于没有产生有效的压应力而失败,预压应力由限制膨胀产生。本工作致力于研究含CaO或CSA膨胀剂、减缩剂(SRA)砂浆在有无潮湿养护下的性能。由于有减缩剂SRA与膨胀剂的配合,即使在没有任何潮湿养护措施下,也会产生限制膨胀。但是,当CaO与减缩剂SRA复合使用时,这种效应比CSA膨胀剂更明显。

Shrinkage-Free Mortars For Repairing Damaged Concrete Structures

Shrinkage-compensating mortars are in general pre-mixed cementations materials which contain expansive agents among the various powder ingredients. The role of the expansive agent, in the form of dead burnt calcium oxide (CaO) or calcium sulfo-aluminate (CSA), is to produce a compressive stress in the repairing mortar due to the restraint exerted by the metallic reinforcements or the friction of the rough concrete substrate. To be successful, the mortar must be carefully wet cured because the expansion can occur only in the presence of water due the hydration of the CaO or CSA based expansive agent. In the absence of careful wet curing, the repairing work can be unsuccessful because there would not be any useful precompression from restrained expansion. The present work is devoted to study the behavior of mortars containing CaO or CSA as expansive agents combined with a Shrinkage-Reducing Admixture (SRA) in the presence and in the absence of wet curing. Due to the synergistic action of the SRA with the expansive agent, the restrained expansion can occur even in the absence of any wet curing. However, this action in much more effective when SRA is combined with CaO rather than with CSA.