Do You Know Why The Ready-Mix Mortar Cracked?

Do You Know Why The Ready-Mix Mortar Cracked?

What is Ready-mix mortar？
Ready-mix mortar is composed of cement, sand, performance additives and other ingredients, mixed in a certain proportion, and used for construction purposes.Ready-mix mortar is divided into two types: wet-mix mortar and dry-mix mortar and can be roughly divided into tile adhesive, waterproof mortar, self-leveling, grouting, external wall insulation, etc.

With the development of construction technology, the requirements for construction efficiency, environmental protection and construction quality continue to increase, Ready-mix mortar replaces more and more cement and mortar mixed on site. But we also found some problems in the construction process, mainly a cracking problem.

Causes of mortar cracking
1. UNREASONABLE MORTAR MIX RATIO
The total cementitious material of mortar or cement admixture cannot exceed 400 kg per cubic meter. Because there is too much powder, the mortar shrinks relatively greatly, which is easy to cause hollowing and cracking. The reasonable mixing ratio is generally controlled between 280-340kg per cubic mortar and the sand ratio is controlled at 80%±5. (The fineness modulus of sand is controlled within 2.4-2.7, and the mud content is within 3%).

2. MORTAR STRENGTH IS TOO HIGH
The strength of mortar is mainly derived from the cementitious material. If the cement content is too high according to the strength grade, it will hydrate too quickly. If not cured in time, it will cause shrinkage and hollowing and cracking.

3. NO LAYERED PLASTERING
If the one-time plaster is too thick or the degree of dryness is not well controlled, it is very prone to construction hollow cracking and shrinking hollow cracking.The plaster thickness should be appropriate and layered plastering.

4. DIFFERENCES IN CONSTRUCTION ENVIRONMENT
Ready-mix mortar may also crack under different construction environments. Construction in a poorly ventilated and damp basement, because the wall contains a lot of water, the water in the mortar is not easy to dissipate, and the initial setting time of the mortar is prolonged.

5. POOR QUALITY ADDITIVES
High-performance and high quality additives reduce and prevent cracking problems.Depending on the type of mortar, the parameters of the additives are different.

For example, cellulose ether is used as a key additive for drymix and ready-to-use applications such as tile adhesives, plasters, renders, and so on.

For these different applications, the cellulose ether grade used should also be different.