A critical criterion for the extrusion of cementitious materials is that the mix used must remain stable and homogeneous without undergoing phase separation. Therefore, it is important to have an assessment of water retention capacity of mortars to be used for such purposes. Although there are empirical methods like bleed test (ASTM C1741 – 18 [1]), these methods are single-point measurements, i.e., conducted at a single pressure value for a fixed amount of time. In the current approach, desorptivity is used as a fundamental material parameter to evaluate the water retaining capability of different cement mortars. Desorptivity values were obtained at different constant pressures to obtain a desorptivity-pressure relationship. The influence of various factors on desorptivity such as the addition of superplasticizer, the addition of water retaining admixtures like hydroxypropyl methylcellulose (HPMC), particle packing density, and water content were examined. Finally, the different mixes were examined for phase separation by using a piston-pump-based system. Based on the maximum pressure applied in the piston pump, an index was proposed that distinguishes the mortars with the required water retention capability for the extrusion process.

挤出胶结材料的关键标准是所使用的混合物必须保持稳定和均匀，且不经历相分离。因此，重要的是要评估用于这种目的的砂浆的保水能力。尽管有诸如排气试验（ASTM C1741 – 18 [1]）之类的经验方法，但这些方法是单点测量，即在单个压力值下进行固定时间的测量。在目前的方法中，吸水率被用作评估不同水泥砂浆保水能力的基本材料参数。在不同的恒定压力下获得解吸度值以获得解吸度-压力关系。各种因素对吸附性的影响，例如添加高效减水剂，检查了保水剂如羟丙基甲基纤维素（HPMC）的添加，颗粒堆积密度和水含量。最后，使用基于活塞泵的系统检查不同混合物的相分离。根据在活塞泵中施加的最大压力，提出了一种指标，该指标可将灰浆与挤出过程所需的保水能力区分开。