The water retention property of mortar refers to the ability of mortar to retain water. Mortar with poor water retention property is easy to bleed and segregate during transportation and storage, that is, water floats above and sand and cement sink below. It must be remixed before use.
All kinds of base courses that need mortar for construction have certain water absorption. If the water retention of mortar is poor, as long as the premixed mortar contacts with the block or base course, it will absorb water from the premixed mortar during the mortar coating process. At the same time, the mortar surface will evaporate water towards the atmosphere, resulting in insufficient water for mortar due to water loss, affecting the further hydration of cement, and affecting the normal development of mortar strength, resulting in strength In particular, the interface strength between the hardened mortar and the base course becomes lower, resulting in mortar cracking and falling off. The mortar with good water retention has sufficient cement hydration, and its strength can be developed normally, and it can bond well with the base course.
The ready mixed mortar is usually laid between the water absorbing blocks or coated on the base course to form a whole with the base. The impact of poor water retention of mortar on project quality is as follows:
1. Due to excessive water loss of mortar, the normal setting and hardening of mortar are affected, and the bonding force between mortar and object surface is reduced, which is not only inconvenient for construction operation, but also reduces the strength of masonry, thus greatly reducing the project quality.
2. If the mortar bond is not good, the water is easily absorbed by the bricks, which makes the mortar too dry and thick and uneven. During the implementation of the project, it not only affects the progress, but also makes the wall easy to crack due to drying shrinkage;
Therefore, increasing the water retention of mortar is not only beneficial to construction, but also can increase the strength.

The molecular weight of HPMC can be expressed by its solution viscosity in the solvent used.
Unless otherwise stated, the molecular weight of HPMC is measured here with UBBELOHDE viscometer at 20 ℃ using an aqueous solution containing 2% (weight) of HPMC.
Its withering degree is generally about 5 to 200000 mpa. Sd uses hydroxypropyl methyl cellulose ether as a suspension agent for suspension polymerization of ethylene unsaturated monomers. The selected firmness is about 5 mpa. s, from about lOmpa. S. to about 400 mpa. s, which is about I00mPa. s.
S, 10100, and 400mpa S is respectively equivalent to the number average molecular weight of 1000013000,26000, and 410000 HPMC ether aqueous solution used as thickener according to the invention and viscosity at 20 ℃, at least about l, o ∞ mpa s. It is better to be about 15000 mpa. s, so the viscosity of the solution is usually up to about 200000 to iso, and it is better to be 120000 to 100000 m pa. s, and it is better to be 75000 mpa So number average molecular weight (M).
The average molecular weight (M) of the number a can be determined by osmometry from about 20000, better from about 55000, better from about 120000; About 280000, 250000 is better, and 2200000 is better.