What is going on with the cracks in the cement mortar

Plastering the surface with low cement grade, and then calendering the surface with plain cement paste, the shrinkage ratio is inconsistent and leads to dry cracking. The best construction method is the original pulp calendering.

The conventional is dry cracking, which is cracking caused by shrinkage.

The cracking of anti-cracking mortar is the reason why the density of the insulation board is too low

The density of the insulation board used for external wall insulation of anti-cracking mortar is mainly 18 22kg m3, but in the construction process, the construction unit is often shoddy, and the insulation board below 18kg m3 is used, which is easy to cause cracking of the plastering mortar layer due to low density, easy deformation and poor impact resistance.

When pasting the insulation board, the full adhesive method should be used, that is, the back of the insulation board should be fully coated with adhesive and then scraped with a toothed trowel before being glued to the wall. The polystyrene board should be pasted in a smooth way, and the vertical direction should be staggered line by row, and the vertical joint should not appear in the vertical direction when the adjacent polystyrene board is pasted.

The insulation board joints at the corners of the wall should be staggered and interlocked, and the insulation boards at the four corners of the door and window openings should not be spliced, and the whole polystyrene board should be cut and formed, and the joints of the insulation board should be at least 200mm away from the corners.

Grassroots treatment:

Before construction, the previous process is strictly accepted, and the flatness and verticality of the surface of the plastering base on the outside of the wall must meet the requirements of the specification to ensure the construction quality of the insulation board paste.

The surface of the base layer should be clean, free of oil, dust and other attachments that hinder bonding, protrusions, hollow drums and loose parts should be removed, and the leveling layer must be firmly bonded with the wall, and there should be no delamination, hollowing and cracks. The use of interface agent for interface treatment can effectively enhance the bond strength between the adhesive and the base layer.

There are many reasons for this. Such as: the uneven settlement of the main structure, the shrinkage of the masonry mortar, and the quality of the exterior wall plastering.

The biggest possibility is that the quality of anti-crack mortar and anti-crack putty powder is not up to standard. It's said that it's a flexible amount, and it's too much fraud. If the inner layer of plastering mortar is more flexible than the putty, it may also cause the outermost layer to crack due to deformation.

The most important thing is that the amount of mortar glued to the outer layer is greater than that of the inner layer. Because the exterior wall is from the inside to the outside, the flexibility of the product is also required to be better and better from the inside to the outside, and the outer layer must meet the deformation of the inner layer.

Anti-cracking mortar. At present, the density of insulation boards used for external wall insulation is mainly 18 22kg m3. However, in the construction process, the construction unit is often shoddy, using insulation boards below 18kg m3, due to low density, easy deformation, poor impact resistance, easy to cause cracking of the plastering mortar layer.

2. The aging time of the insulation board is not enough: the self-shrinkage and deformation time of the insulation board in the natural environment is as long as 60 days, but due to the factors such as capital turnover and cost control of the production enterprise, it is usually based on sales, and the natural aging of the insulation board used in a large number of projects has been on the wall in less than 7 days, and the polymer mortar results in the continuous shrinkage of the insulation board after the wall, and the shrinkage stress of this reinforcement mortar is concentrated in the joint of the board, which produces tensile stress on the plastering mortar layer adhered to the insulation board and causes the plastering mortar layer to crack.

Anti-crack mortar is actually a mortar mixed with polymer (glue).

Or a mortar with added fibers.

Although called anti-crack mortars, they can also crack.

It depends on whether the construction, maintenance and other links are done well.

If you do not add water in proportion, if the base surface is not well treated, such as the construction quality of the country is too poor or completely ignored after construction.

Left to dry shrinkage, exposure to the sun, dry hot air, etc., the anti-cracking mortar will still crack.

Of course, there are also so-called anti-cracking mortars that are simply fake and shoddy, cutting corners.

Hello dear! 1. The quality of the plastering mortar material The reasons for the cracking of the plastering mortar caused by the quality of the plastering mortar material itself are: 1. There is too much plastering mortar cement, resulting in excessive self-shrinkage, and the lack of relatively flexible anti-cracking materials may cause the cracking of the plastering mortar.

2. The sand grading in the plastering mortar material is unreasonable, and the large mud content of the sand can cause the plastering mortar to crack. 3. The anti-cracking material of the plastering mortar itself is insufficient, if the construction environment is harsh, coupled with the addition of latex powder, the addition of anti-cracking fibers may cause the cracking of the plastering mortar. 4. The plastering mortar will also cause the plastering mortar to crack if it is not really constructed during construction.

2. There are two main reasons why the external wall insulation wall base may lead to the cracking of the plastering mortar: 1. The reason for the temperature change, the temperature change will cause the building materials to expand or contract, but different materials have different temperature coefficients and deformation stresses. Thermal expansion produces temperature stress at the interface, and once the temperature stress is greater than the tensile strength of the plastering mortar, the material will be displaced, resulting in cracks in the plastering mortar.

2. When the shrinkage stress is greater than the tensile strength of the plastering mortar, the plastering mortar will produce cracks. Therefore, in the construction of external wall insulation plastering mortar, it is necessary to pay attention to the quality of the plastering mortar itself and the wall base of external wall insulation, and prevent cracks in the plastering mortar.

There are many reasons for the cracking of cement mortar leveling on the concrete floor, such as the base is not clean, there is no sprinkling before the mortar is wet, the mortar mix ratio is not suitable, the stability of the cement is unqualified, the sand mud content is too large, the cement mortar loses water too quickly after wiping, and the maintenance is not good.

Ordinary concrete refers to the artificial stone made of cement as the main cementitious material, mixed with water, sand and gravel, mixed with chemical admixtures and mineral admixtures if necessary, matched in appropriate proportions, and hardened by uniform mixing, dense molding and curing.

Concrete is mainly divided into two phases and states:

The plastic state before setting and hardening, i.e. fresh concrete or concrete mixture; The hard state after hardening, i.e., hardened concrete or concrete. The concrete strength grade is divided by the standard value of cubic compressive strength, and the strength grade of ordinary concrete in China is divided into 14 grades: C15, C20, C25, C30, C35, C40, C45, C50, C55, C60, C65, C70, C75 and C80.

In the case of cracks after ground leveling, first determine whether the cement mortar is used for leveling, and the main reason for the cracks after the use of cement mortar is that there is too much cement in the cement mortar and the cushion area is too large.

Hello, the reason why there are cracks in the concrete floor slab with cement sand beam leveling is that the sand award is too Pu.

The reasons for the cracking of cement mortar are too much cement in the cement mortar, too large cushion area, no layered and segmented pouring, and no timely sprinkling of water during maintenance, and the cement dries too quickly. At the same time, another reason is that the ratio is unreasonable, resulting in non-solidification of water and sand.

It is also normal to use cement mortar to level and crack, because the cement will shrink when it dries, and the best thing is to let the foam particles add cement mortar.

Cracks are found on the mixed floor with mortar leveling, which should belong to your cement mortar, and its moisture is lost or dispersed relatively quickly, resulting in such a situation.

Types of cracks in house cast-in-place concrete floor slabs 1Longitudinal cracks: that is, cracks along the longitudinal direction of the building, mostly appearing under the slab, and some penetrate up and down. 2.Transverse cracks: i.e. in the span.

What are the causes of cracking of anti-cracking mortar: Analysis of the causes of cracks: 1

The density of the insulation board is too low: due to the low density, easy deformation and poor impact resistance, it is easy to cause cracking of the plastering mortar layer. 2.

Insulation board aging time is not enough: a large number of engineering use of insulation board natural aging less than 7 days on the wall, the polymer mortar result is that the insulation board continues to shrink after the wall, and the shrinkage stress of this reinforcement mortar is concentrated in the joint of the board, the plastering mortar layer adhered to the insulation board produces tensile stress and causes the plastering mortar layer to crack. 3.

Pulverization of insulation board materials: due to factors such as long construction period or construction in alternate years, the surface of the insulation board is pulverized, and the pulverization interface seriously affects the bonding of the plastering mortar and the insulation board, which can easily lead to the instability of the insulation board or the plastering mortar, causing the insulation layer to fall off or the plastering mortar layer to crack. 4.

The thermal conductivity difference between the plastering mortar and the insulation board is too large: due to the temperature difference and the influence of the outdoor temperature of day and night and the season, the amount of deformation of the plastering mortar layer is very large, and the plastering mortar is easy to produce cracks. 5.

The adhesive material is incompatible and mismatched with the bonded material, resulting in the poor bonding of the insulation board and the cracking of the plastering mortar layer.

Summary. Hello, the cracking of anti-cracking mortar may be caused by the deformation of the wall structure: the uneven settlement of the foundation, the spacing of the transverse wall is too large, the corner stress concentration of the brick wall is not reinforced, the door and window openings are too large, and the deformation joints are improperly set, etc., so that the wall produces structural deformation cracks due to insufficient strength, stiffness and stability, resulting in the cracking of the mortar layer.

Hello, the cracking of anti-cracking mortar may be caused by the deformation of the wall structure: the uneven settlement of the foundation, the spacing of the transverse wall is too large, the corner stress concentration of the brick wall is not reinforced, the door and window openings are too large, and the deformation joints are not set properly, etc., so that the wall is not strong enough to produce structural deformation cracks due to insufficient strength, stiffness and stability of the tremor, resulting in the cracking of the mortar layer.

It is also possible that the selection of raw materials and ingredients is improper, or the construction process is improper or the construction is not in accordance with the requirements of the specification.