In recent years, with the continuous development of external wall thermal insulation technology, the continuous progress of cellulose production technology, and the excellent characteristics of HPMC itself, HPMC has been widely used in the construction industry. In the setting time test, the setting time of concrete is mainly related to the setting time of cement, and the aggregate has little influence. Therefore, the setting time of mortar can be used to replace the influence of HPMC on the setting time of underwater non dispersive concrete mixture. Since the setting time of mortar is affected by the water cement ratio and cement sand ratio
For the influence of HPMC on the setting time of mortar, it is necessary to fix the water cement ratio and cement sand ratio of mortar.It can be seen from the experiment that the addition of HPMC has an obvious retarding effect on the mortar mixture, and the setting time of the mortar increases with the increase of the amount of HPMC. With the same amount of HPMC, the setting time of the mortar formed under water is longer than that formed in air.

This study was conducted using a CEM I 52.5N sample (“Milke®” from HeidelbergCement AG, Heidelberg, Germany). Its properties are presented in Table 1. Composition of the cement was obtained by Q-XRD using a Bruker axs D8 Advance instrument (Bruker, Karlsruhe, Germany) with Bragg–Brentano geometry. Topas 4.0 software was employed to quantify the amounts of individual phases present in the sample by following Rietveld's method of refinement. The amounts of gypsum (CaSO₄·2H₂O) and hemi-hydrate