Investigation of the mechanism on progress for strength and air permeability of concrete using C-S-H hardening accelerator

There are some researches which are progressing to apply C-S-H hardening accelerator in concrete. This admixture is an effective material for accelerating the gain in compressive strength at early ages, this can make possible to increase productivity of concrete structures and products due to the earlier framework removal. In this research, first it is focused on the progress of compressive strength at early age and its development as water cement ratio vary from low to high. Second, it is focused on the durability parameters such as air and water permeability as well as improvement in porosity at interfacial tradition zone. This study investigated using two analyses. One focusing in the examination of the adding method of C-S-H hardening accelerator and its proportions and the other analyzes the porosity area improvement contributed by the C-S-H hardening accelerator. As a result, the addition of C-S-H nanoparticles makes a more effective precipitation site when added over unit of water amount than compared with the conventional addition over to cement. This effect is recognized in the interfacial transition zone with low amount of C-S-H addition. It was also found that the mortar part of concrete was modified by high amount of hardening accelerator addition. Finally, we got the effect of densifying the pores in the interfacial transition zone area was observed in a small amount of CSH hardening accelerator. On the other hand, densification of the bulk portion is also recognized by the addition of a large amount of CSH hardening accelerator, so it is considered that the added amount influences the properties of the concrete.