The importance of mortar water retention!

Why do people have such high requirements for water retention in mortar? What are the outstanding points of mortar with good water retention? Let me introduce to you the importance of mortar water retention:

1、 Necessity of water conservation

Water retention of mortar refers to the ability of mortar to preserve water. Mortar with poor water retention is easy to bleed and separate during transportation and storage, that is, water floats on the top and sand and cement sink below. It must be re mixed before use.

All kinds of base courses requiring mortar construction have certain water absorption. If the water retention of mortar is poor, in the process of mortar application, as long as the ready mixed mortar contacts with the block or base course, the water will be absorbed by the ready mixed mortar. At the same time, the water will evaporate from the surface of the mortar facing the atmosphere, resulting in insufficient water in the mortar due to water loss, affecting the further hydration of cement, At the same time, it will affect the normal development of mortar strength, resulting in lower strength, especially the interface strength between mortar hardened body and base course, resulting in mortar cracking and falling off. For the mortar with good water retention, the cement hydration is relatively sufficient, the strength can develop normally, and can bond well with the base course.

Ready mixed mortar is usually built between absorbent 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:

Due to excessive water loss of mortar, it affects the normal setting and hardening of mortar and reduces the bonding force between mortar and material surface, which is not only inconvenient for construction operation, but also reduces the strength of masonry, thus greatly reducing the project quality;

If the mortar is poorly bonded, the water is easy to be absorbed by the brick, which makes the mortar too dry 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 conducive to construction, but also increase the strength.

2、 Traditional water retention method

The traditional solution is to water the base course, but it is impossible to ensure that the base course is evenly and properly wetted. The ideal hydration goal of cement mortar on the base course is that the cement hydration products penetrate into the base course with the process of water absorption by the base course, forming an effective "key connection" with the base course, so as to achieve the required bonding strength.

Watering directly on the surface of the base course will seriously disperse the water absorption of the base course due to different air temperature, watering time and watering uniformity. The base course has little water absorption and will continue to absorb the water in the mortar. Before the cement hydration, the water will be absorbed, affecting the cement hydration and the penetration of hydration products into the matrix; The water absorption of the base course is large, the migration speed of water in the mortar to the base course is slow, and even a rich water layer is formed between the mortar and the matrix, which also affects the bond strength. Therefore, the common base watering method can not effectively solve the problem of high water absorption of wall base, but will affect the bond strength between mortar and base, resulting in hollowing and dry crack.

3、 High efficiency water retention

The high water retention performance of mortar has many points:

The different water retention performance makes the opening time of mortar longer, with points such as large-area construction, long service time in the barrel, batch mixing and batch use;

Good water holding performance can make the cement in the mortar hydration fully and effectively improve the bonding performance of the mortar;

The mortar has different water retention performance, so that the mortar is not easy to produce segregation and bleeding. Now, the workability and constructability of the mortar are improved.

4、 Improvement of water retention of mortar

Hydroxypropyl methylcellulose (HPMC) and water retaining agent are more common water retaining products of mortar. Increasing water retaining property is conducive to construction. Like the current thermal insulation mortar and some ordinary mortar, putty powder and coating, cellulose will be used as auxiliary materials to improve the water retention, thickening and constructability of mortar!

Wechat pictures_ twenty trillion and two hundred and one billion twenty million one hundred and one thousand and thirty-eight Jpg "chuangyao" brand hydroxypropyl methylcellulose is a odorless and tasteless white powder, which swells into a clear or slightly turbid colloidal solution in cold water. It has the characteristics of thickening, adhesion, dispersion, emulsification, film formation, suspension, adsorption, gel, surface activity, moisture retention and protective colloid. It is mainly used in building materials and coating industry.

Different products use different cellulose. Hydroxypropyl methylcellulose HPMC is generally added to mortar (the main role of MC in mortar is thickening and water retention). Add a small amount of MC. If it is caused by segregation, it is estimated to add a small amount of water reducing agent (pumping agent) and adjust the water. The specific amount depends on the mortar.

The main factors affecting the water retention of mortar are:

① Cementitious materials, mainly cement varieties and cement dosage;

② The variety of sand, river sand, machine-made sand and the thickness and gradation of sand;

③ Water consumption when mixing mortar.

If you want to improve the water retention of mortar, you can add some powdery mixed materials such as lime paste and fly ash when producing mortar.