Several problems often encountered in dry-mix mortar in engineering applications

Dry-mixed mortar is usually called hydraulic cement mixed mortar. It refers to the physical mixing of aggregates (such as quartz sand). inorganic cementitious materials (such as cement) and additives (such as polymers) which are dried and sieved. It is a kind of granule or powder, which is transported to the construction site in the form of bag or bulk. After adding water and mixing, it can be directly used to analyze the major problems often encountered in engineering applications.

1. The mortar feels thicker when used.

The dry mortar produced by artificial sand, the maximum particle size of the sand is generally less than 3.5mm, far less than the standard 4.75mm. The worker feels that the mortar is still thicker during construction. In fact, the coarser feeling is mainly due to the poor workability of the mortar.

Sexuality is not good, it seems that there are more large particles. The primary reason is that the particle gradation of artificial sand is not good. It is often the phenomenon that the sand has more ends and less center. It needs to supplement the sand in the central area.

2. Plastering mortar cracking hollow drum

Mortar cracking is divide into plastic cracking and dry shrinkage cracking. Plastic cracking refers to the cracking of the mortar before or during hardening. It generally occurs in the early stage of mortar hardening. The cracks are generally coarse and the crack length is short.

The dry shrinkage cracking refers to the cracking of the mortar after hardening. It generally occurs in the mortar. In the late stage of hardening, the crack is characterizing by a thin and long length.

Plastic cracking is mainly due to the shortening of stress in the plastic state shortly after mortar plastering due to water dispersion. When the shortening stress is greater than the bond strength of the mortar itself, cracks occur on the surface. It is often associate with the properties of the mortar and the ambient temperature, temperature and appearance.

The larger the amount of cement, the smaller the modulus of sand fineness, the higher the mud content, the greater the water consumption, the poor water retention of the mortar, and the more likely the mortar is plastically crack.

Dry shrinkage cracking is mainly due to the large amount of mortar cement, the high strength leads to the shortening of the volume, the maintenance of the mortar is not in place, the mortar admixture or additive is dry and shorten, the wall itself is cracked, the interface is not properly treated, the mortar label is used indiscriminately or misplaced. The difference between the substrate and the mortar elastic modulus is too large.

3. Agglomeration, agglomeration

The moisture content of the sand in the raw materials of the dry-mixed mortar production enterprise did not reach the standard requirement. The mortar mixing time was too short and the mixing was uneven. The construction company failed to finish the dry-mixed mortar silo and mixer in time according to the requirements of dry-mix mortar construction.

4. The mortar will soon show bubbles

(1) The adaptability of the additive to the cement is not good, resulting in bubbles in the reaction.
(2) If the sand fineness modulus is too small or the particle gradation is poor, the porosity is too high.