Condensation time test
Concrete condensation time is mainly related to the condensation time of cement, little impact of aggregate. So you can use mortar condensation time instead of the study of HPMC on underwater concrete mix condensation time. Because the mortar condensation time by water cement ratio, cement ratio. So in order to evaluate the influence of HPMC on mortar condensation time. Need to fix the mortar water cement ratio and cement sand ratio.
Is a polymer polymer, is a macromolecular linear structure, the functional group with hydroxyl group. Can form hydrogen bonds with the mixing water molecules, so that the mixing water viscosity increases. The long molecular chains of HPMC will attract each other. Causing the HPMC molecules to form a network structure, wrapping up the cement and mixed water. Because HPMC forms a film-like mesh structure and its wrapping effect on cement. It will effectively prevent the volatilization of water in mortar and hinder or slow down the hydration speed of cement.
Mortar and concrete drainage phenomenon is similar, will make the aggregate settlement is serious. Resulting in the water-ash ratio of the top slurry increased, so that the top slurry in the early stage of great plastic shrinkage. Or even cracking, and the strength of the slurry surface is relatively weak. It can from the experiment that when the admixture is above 0.5%. There is basically no longer urology phenomenon. This is because when HPMC is incorporate into the mortar.
HPMC has a film-forming and mesh structure, as well as the adsorption of the hydroxyl group on the macromolecular long chain. So that the cement in the mortar and the mixed water form a flocculation shape. After HPMC is add to the mortar, many independent tiny air bubbles will form. These bubbles will be evenly distribute in the mortar, hindering the deposition of the aggregate. The technical performance of HPMC has a great impact on cement based materials. Which is often use to prepare new cement base composite materials such as dry mortar and polymer mortar, so that it has good water and plastic retention.