Abstract: Mortar is a bonding material used for building bricks, divided into various types and strength grades. When choosing, it is necessary to consider the actual environment and construction needs. When preparing mortar, attention should be paid to additives and mixing methods. There are differences in composition, water retention, and strength between cement mortar and mixed mortar, each with its own applicable scenarios.


Mortar is a bonding material used for building bricks, made by adding a certain proportion of sand and bonding materials (cement, lime paste, clay, etc.) with water, also known as mortar. Common types of mortar include cement mortar, mixed mortar (or cement lime mortar), lime mortar, and clay mortar.
1、 The strength grades of mortar are divided into several levels

If it is pre mixed masonry mortar or cement mortar, it is generally divided into 7 grades, namely M30 M25、M20、M15、M10、M7.5、M5， If it is cement mixed mortar, it is generally divided into four grades, namely M15, M10, M7.5, and M5. There are many types and strength grades of mortar on the market, and their performance, scope of use, price, and construction methods will also vary depending on the type and strength grade. When choosing, it is important to consider the actual usage environment, construction needs, and other factors.

The strength of masonry mortar is expressed by its strength grade.

The strength grade of mortar is determined by measuring the compressive strength value (in MPa) of a 28 day old cube with a side length of 70.7mm under standard curing conditions (temperature (20 ± 2) ℃, relative humidity above 90%) using standard testing methods.

In general, M2.5-M15 masonry mortar is used for the walls of multi story buildings; The strength grade of mortar is not fixed and is generally affected by factors such as construction technology, material quality, and mixing ratio. When there are many impurities or mud content in the mortar, the strength of the mortar will decrease, affecting its performance and service life.

2、 What aspects to pay attention to when mixing mortar

1. During the mixing process, an appropriate amount of waterproof powder and other additives should be added to the mortar to improve its viscosity and stickiness. If you want to mix mortar into concrete, you should also pour an appropriate amount of stones into the mortar.

2. When mixing, it is necessary to master the mixing time and mixing method, and the mixing time cannot be too long or too short. If the mixing time is too long or left for too long, it will cause the lime in the mortar to evaporate, resulting in a decrease in strength or causing problems in the mixing process of the mortar.

3、 The difference between cement mortar and mixed mortar
Performance characteristics of mixed mortar

1. High foaming speed can produce a large amount of foam in an instant, and foam can be evenly distributed in three dimensions.

2. Very high foaming ability, with high-energy instant foaming, rapid foaming, and three-dimensional foaming ability.

3. Very high foam stabilizing effect. The foam lasts for a long time. The foam is very durable and stable.

4. It won't be hard in winter and won't melt in summer. It's stable and can quickly and evenly mix with base powder.
Differences in the definition of mortar

1. Cement mortar=cement+sand+water. Cement mortar is made by mixing cement and sand in a certain proportion, and it can be used to prepare mortar with higher strength. Cement mortar is generally used for foundations, basements that have been soaked in water for a long time, and masonry that withstand significant external forces.

2. Lime mortar=lime+sand+water. Adding lime (paste) is called "lime mortar" or "lime mortar". Lime mortar is a mortar made by mixing lime paste and sand in a certain proportion, and its strength is obtained entirely by the air hardening of lime.

3. Mixed mortar=cement+sand+gypsum+water. Adding cement and lime is called "mixed mortar". Mixed mortar is generally made by mixing cement, lime paste, and sand, and is generally used for masonry above ground level. Due to the addition of lime paste, mixed mortar improves the workability of factory mortar, making it more convenient to operate and beneficial for improving the compactness and efficiency of masonry.

Simple discrimination of mortar

1. Looking at the color, lime mortar is white, mixed mortar is medium gray, and cement mortar has a darker color due to the absence of white ash.
2.Although the early strength of lime mortar is low, its strength is not low after air hardening, and it cannot be scratched by nails.
3.It can be determined based on where it is used.

Mixed mortar is generally made by mixing cement, lime paste, and sand, and is generally used for masonry above ground level.

The purpose of cement mortar in construction engineering is to use it as an adhesive for block masonry materials in foundation and wall masonry. For example, cement mortar is used for building rubble and red bricks; The second is for indoor and outdoor plastering. It can be used alone for masonry and decorative plastering, or can be made into mixed mortar (such as cement lime mortar, cement clay mortar) to be suitable for different requirements of masonry and plastering engineering.

The difference between cement mortar and mixed mortar

1. Different compositions:

Mixed mortar is generally made by mixing cement, lime paste, and sand, and is generally used for masonry above the ground. Mixed mortar improves the workability of mortar by adding lime paste, making it more convenient to operate and beneficial for improving the compactness and efficiency of masonry. Cement mortar is composed of cement, medium sand, and water mixed together, and its price is related to the proportion of materials.

2. Different water retention properties:

Cement mortar is prone to cracking, which is one of the reasons why mixed mortar is used instead of cement mortar for interior wall plastering. In addition, from the appearance, it should be noted that the water retention of cement mortar during transportation is not as good as that of mixed mortar. During the bumpy transportation process, the cement mortar with a layer of water on the surface (the sand with a low grade can also be seen as unmixed sand), and the workability and water retention of the mixed mortar are better than those of the cement mortar.

3. Different intensities:

Cement mortar is mainly used in damp areas such as basements, foundations, hydraulic engineering, etc. Compared with mixed mortar, cement mortar with the same grade has a higher strength, so the specifications stipulate that cement mortar should be used as corner protectors for door and window openings. Mixed cement mortar is made by adding lime, clay and other additives on the basis of cement mortar. Mixed cement mortar has strong plasticity and is easy to operate. Cement mortar has one less lime paste than mixed water mortar, and its strength is not high.

Article source: Building safety inspection and appraisal