In recent years, with the continuous development of external wall insulation technology, the continuous progress of cellulose production technology, and the excellent characteristics of HP cellulose itself, HP cellulose has been widely used in the construction industry. In order to deeply understand the mechanism of HP cellulose and cement-based materials, this paper introduces the improvement effect of HPMC cellulose on the cohesion of cement-based materials.
The setting time of concrete is mainly related to the setting time of cement, and the aggregate has little effect, so the setting time of mortar can be used instead of studying the effect of HPMC cellulose on the setting time of underwater non dispersible concrete mixture. Since the setting time of mortar is affected by water cement ratio and cement sand ratio, in order to evaluate the effect of HPMC cellulose on the setting time of mortar, it is necessary to fix the water cement ratio and cement sand ratio of mortar.
The experimental results show that the addition of HPMC cellulose has an obvious retarding effect on the mortar mixture, and the setting time of mortar is prolonged with the increase of HPMC cellulose content. Under the same hp cellulose content, the setting time of mortar formed under water is longer than that formed in air. When measured in water, the setting time of mortar mixed with HPMC cellulose is 6~18 h delayed in initial setting and 6~22 h delayed in final setting compared with the blank sample. Therefore, HPMC cellulose should be combined with early strength agent.
HPMC cellulose is a high molecular polymer with a macromolecular linear structure and hydroxyl groups on the functional groups, which can form hydrogen bonds with the mixing water molecules to increase the viscosity of the mixing water. The long molecular chains of HPMC cellulose attract each other, making HPMC cellulose molecules intertwine to form a network structure, which wraps the cement and mixing water. Due to the network structure similar to the film formed by HPMC cellulose and its wrapping effect on cement, it can effectively prevent the evaporation of water in mortar and hinder or slow down the hydration speed of cement