CN102432255B - Cement-based self-leveling mortar - Google Patents

Abstract

The cement-based self-leveling mortar is prepared from the following raw materials in percentage by weight: 35% -40% of ordinary portland cement with the reference number of 425; 10% -15% of fast hardening sulphoaluminate cement with the grade of 42.5; 15% -18% of heavy calcium; 0.45% -1% of high-molecular polymer; 0.15-0.3% of a water reducing agent; 0.15-0.3% of an early strength agent; 0.15-0.3% of retarder; 0.15-0.3% of a thickening agent; the rest is fine river sand with fineness modulus of 1.2-1.5. Compared with other traditional cement self-leveling mortar, the mortar has the characteristics of higher fluidity, better leveling property, high early strength and the like.

Description

A cement-based self-leveling mortar

technical field

The invention relates to the field of concrete additives, in particular to a cement-based self-leveling mortar.

Background technique

Cement-based self-leveling mortar has good fluidity and stability, high early strength, fast construction speed, and low labor intensity. It is an ideal material for ground paving of large supermarkets, parking lots and warehouses, and is also an ideal material for ground construction of modern buildings. The development direction has great market potential. Compared with developed countries, the research on cement-based self-leveling mortar in my country started relatively late, around the late 1980s and early 1990s, and the initial development speed and popularization were also slow. On the one hand, it is because this material is not very suitable for the national conditions at present. The second is that the current domestic economy and construction technology are relatively backward, and the cost of large-area use in construction projects is relatively high, which is difficult for users to accept. The cement self-leveling mortar currently on the market mainly has the following problems:

(1) The early strength is low. Since the cement-based self-leveling mortar generally uses ordinary Portland cement as the main cementing material, ultra-fine sand and high water-cement ratio are used, the early strength of the mortar is seriously insufficient, which directly affects the construction process. and the time when the project is put into use.

(2) The flatness of the mortar surface is not enough. Due to the imperfect mortar formula, it is easy to produce surface sanding, peeling, hollowing and other phenomena, which not only affects the appearance, but also directly endangers the quality of self-leveling mortar.

(3) Insufficient wear resistance. Self-leveling mortar is mainly suitable for large supermarkets, shopping malls, parking lots, factory workshops, warehouses and other floors, which require high wear resistance.

(4) After the mortar is hardened, it is easy to shrink and crack. Firstly, cement will shrink in volume during the hydration reaction; secondly, self-leveling mortars are constructed in thin layers, and the evaporation caused by high surface/volume ratio produces significant and rapid physical shrinkage. This caused cracking after the mortar hardened.

Contents of the invention

In order to overcome several defects of the above cement-based self-leveling mortar, the purpose of the present invention is to provide a new type of cement-based self-leveling mortar, which adds special cement with high early strength to ordinary Portland cement, and is compatible with various early strength agents. The coagulant is matched with each other, so that the mortar has a long working time, a short setting time and high early strength. High-molecular polymer is added to the mortar, which has a short film-forming time and good performance, which can greatly improve the smoothness and flatness of the self-leveling and condensed mortar surface, and improve the wear resistance of the mortar. In order to compensate the volume shrinkage caused by cement hydration, a shrinkage reducing agent and an expansion agent are added to the mortar, which greatly reduces the phenomenon of cracks and cracks after the mortar hardens.

In order to achieve the above object, the present invention adopts the following technical solutions: a cement-based self-leveling mortar, which is made of the following raw materials in terms of weight percentage: ordinary Portland cement 35%~40%; rapid hardening sulfoaluminic acid Salt cement 10%~15%; heavy calcium 15%~18%; polymer 0.45%~1%; water reducing agent 0.15~0.3%; early strength agent 0.15~0.3%; retarder 0.15~0.3%; Thickener 0.15~0.3%; the balance is fine river sand with a fineness modulus of 1.2-1.5.

The standard mortar strength grade of the above ordinary Portland cement is not less than 42.5.

The standard mortar strength grade of the above rapid hardening sulfoaluminate cement is not less than 42.5.

The above-mentioned cement mortar polymer is redispersible latex powder.

The above cement mortar water reducer is a polycarboxylate water reducer.

The above-mentioned early strength agent for cement mortar is selected from sodium sulfate or/and triethanolamine.

The above cement mortar retarder is selected from one or more of tartaric acid, citric acid and boric acid.

The above-mentioned cement mortar thickener is hydroxypropyl methylcellulose ether or/and sodium alkylsulfonate.

In the present invention, the function of rapid hardening sulfoaluminate cement is to increase the early strength, heavy calcium is used as a filler, which is beneficial to increase the water demand ratio of mortar and improve leveling, and the redispersed latex powder for high molecular polymer can greatly strengthen the cement The modulus of elasticity of the mortar improves the toughness.

The present invention uses the composite cement of ordinary Portland cement and rapid-hardening sulfoaluminate cement as the cementing material, and adds a small amount of high molecular polymer. After the polymer is formed into a film, the flatness and wear resistance of the mortar surface are increased. At the same time of hydration, the polymer forms a film in the mortar, which makes the surface of the mortar smooth and smooth after setting, enhances the elastic modulus of the mortar, makes the surface of the mortar beautiful and does not produce cracks, and is equipped with various admixtures (water reducing agent, early Strengthening agent, retarder, thickener) and fine river sand are mechanically mixed, and can be used directly by adding water at a water-to-material ratio of 0.16-0.21 and stirring evenly. And early strength (1d strength) and other indicators are better than traditional cement self-leveling mortar. The mortar has good fluidity and leveling performance. When the mortar is flattened on the ground, it can form a mortar layer with a thickness of 2-3mm and an overall flat surface without external force and relying solely on gravity; the setting time of the mortar is short and the 1d strength is high. The earth speeds up the construction progress and enables the project to be put into use as soon as possible.

Compared with other traditional cement self-leveling mortars, the invention has the characteristics of higher fluidity, better leveling performance and high early strength. Engineering experiments show that the self-leveling mortar is superior to the traditional self-leveling mortar in terms of fluidity and strength. The fluidity of the machine reaches 175mm, and there is almost no loss of fluidity after 20 minutes; the final setting time is short, generally less than 3h; the early strength is high, and the next process can be carried out quickly without waiting for a long time, and the strength can reach 30Mpa in 1 day. The product meets the national standard of JC/T985-2005 "cement-based self-leveling mortar for ground" (see the experimental data table in Table 1 for details).

Table 1 is the experimental data table of the present invention.

The invention is suitable for large-scale floor projects, such as large supermarkets, shopping malls, parking lots, stadiums, factory workshops, warehouses and the like.

Detailed ways

Below we will further illustrate the present invention in conjunction with specific embodiments.

Example 1

formula:

350kg of ordinary Portland cement with a standard mortar strength grade of 42.5; 100kg of fast-hardening sulfoaluminate cement with a standard mortar strength grade of 42.5; heavy calcium 15kg; redispersible latex powder 4.5kg; polycarboxylate superplasticizer NT-200 (produced by Suzhou Fuke New Building Materials Co., Ltd.) 1.5kg; triethanolamine 1.5kg; tartaric acid 1.5kg; hydroxypropyl methylcellulose ether 1.5kg; fine river sand with a fineness modulus of 1.4 524.5kg.

During construction, add water to the above product and stir evenly to form a slurry that can be used (the weight ratio of water to dry powder mortar of this product is 0.16-0.20:1).

Example 2

formula:

380kg of ordinary Portland cement with a standard mortar strength grade of 42.5; 120kg of fast-hardening sulfoaluminate cement with a standard mortar strength grade of 42.5; heavy calcium 16kg; redispersible latex powder 7kg; polycarboxylate superplasticizer NT -201 (produced by Suzhou Fuke New Building Materials Co., Ltd.) 2kg; triethanolamine 2kg; tartaric acid 2kg; hydroxypropyl methylcellulose ether 2kg; fine river sand with a fineness modulus of 1.4 469kg.

During construction, the above product can be used by adding water and stirring it into a slurry (the weight ratio of water to dry powder mortar of this product is 0.16-0.21:1).

Example 3

formula:

400kg of ordinary Portland cement with a standard mortar strength grade of 42.5; 150kg of fast-hardening sulfoaluminate cement with a standard mortar strength grade of 42.5; heavy calcium 18kg; redispersible latex powder 1kg; polycarboxylate superplasticizer NT -300 (produced by Suzhou Fuke New Building Materials Co., Ltd.) 3kg; triethanolamine 3kg; tartaric acid 3kg; hydroxypropyl methylcellulose ether 3kg; fine river sand with a fineness modulus of 1.4 419kg.

During construction, add water to the above product and stir it into a slurry (the weight ratio of water to dry powder mortar of this product is 0.16-0.21:1).

The method of use of the present invention:

The construction technology of cement self-leveling mortar has a crucial influence on the quality of the mortar. The specific construction technology is as follows:

1. Requirements for the basic ground

The basic cement floor is required to be clean, dry and smooth. details as follows:

1. There should be no empty shell between the foundation ground and the lower ground;

2. There should be no sand grains on the foundation ground, and the surface should be kept clean;

3. The foundation ground must be flat, and the height difference within two meters is required to be less than 4mm. ;

4. The foundation ground must be dry, and the moisture content should not exceed 17 degrees when measured with a special testing instrument;

5. The compressive strength of the foundation ground shall not be less than 10Mpa.

2. Preparation before construction

Before the cement self-leveling construction, the base ground must be ground with a grinder to remove impurities, floating dust and sand on the ground. Grind the ground level with more local elevations. After sanding, sweep away the dust and vacuum it up. After the ground is cleaned, it must be treated with a surface treatment agent before cement self-leveling. Dilute the treatment agent according to the manufacturer's requirements, and use a non-hair-removing wool roller to spread the surface treatment agent evenly on the ground in the direction of first horizontal and then vertical. Make sure to apply evenly without leaving gaps. After applying the treatment agent, according to the performance of different manufacturers' products, wait for a certain period of time to start the construction of the self-leveling cement above. The cement surface treatment agent can increase the bonding force between the self-leveling cement and the ground, and prevent the shelling and cracking of the self-leveling cement. It is recommended to apply the ground treatment agent twice.

3. Construction environment

Some ventilation is allowed in the work area, but doors and windows should be closed to avoid drafts during and after construction. The indoor and ground temperature should be higher than 10°C during construction and within one week after construction. The relative humidity of the ground concrete should be less than 95%.

4. Construction of cement-based self-leveling mortar

Prepare a large enough bucket, add water strictly according to the given water-to-material ratio (0.16-0.21) , and use an electric mixer to mix the self-leveling cement thoroughly. Stirring is carried out twice, usually the first stirring is about 5-7 minutes, and the middle needs to stop for 2 minutes to allow it to react, and then stir for about 3 minutes. Stir thoroughly, and no lumps or dry powder should appear. The self-leveling cement that has been stirred must be fluid. The self-leveling cement that has been stirred should be used within half an hour as much as possible. Pour the cement self-leveling on the ground, use a toothed target to open the self-leveling target, and target different sizes of areas according to the required thickness. After it is naturally leveled, roll it vertically and horizontally with a toothed roller to release the gas and prevent foaming.

Five, fine grinding treatment

The perfect cement self-leveling construction is inseparable from the grinder. After the cement self-leveling construction is completed, there may be small pores, particles and floating dust on the self-leveling surface, and there may also be height differences between the door and the corridor. These situations require a grinder for further refinement. Vacuum the dust after sanding.

Claims (5)

1. A cement-based self-leveling mortar, characterized in that the self-leveling mortar is made of the following raw materials by weight percentage: 35%-40% of ordinary Portland cement with a standard mortar strength grade of not less than 42.5; Rapid hardening sulfoaluminate cement with sand strength grade not less than 42.5 10%-15%; heavy calcium 15%-18%; redispersible latex powder 0.45%-1%; water reducing agent 0.15-0.3%; early strength 0.15-0.3% additive; 0.15-0.3% retarder; 0.15-0.3% thickener; the balance is fine river sand with a fineness modulus of 1.2-1.5. 2. The cement-based self-leveling mortar according to claim 1, characterized in that the cement mortar water reducer is a polycarboxylate water reducer. 3. The cement-based self-leveling mortar according to claim 1, characterized in that said early strength agent for cement mortar is selected from sodium sulfate or/and triethanolamine. 4. The cement-based self-leveling mortar according to claim 1, characterized in that the cement mortar retarder is selected from one or more of tartaric acid, citric acid and boric acid. 5. The cement-based self-leveling mortar according to claim 1, characterized in that the cement mortar thickener is hydroxypropyl methylcellulose ether or/and sodium alkylsulfonate.