Gypsum self-leveling mortar with low shrinkage and low flow loss
By using sulfate cement and flow retainer β-cyclodextrin in gypsum self-leveling mortar, the shrinkage cracking and flow loss problems of gypsum self-leveling mortar during construction on insulation boards and floor heating pipe bases are solved, and the effects of low shrinkage and low flow loss are achieved, improving construction quality and later maintenance costs.
Patent Information
- Application Number
- CN202311869626.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2023-12-29
- Publication Date
- 2025-07-01
AI Technical Summary
When gypsum self-leveling mortar is constructed on the insulation board base layer and the floor heating pipe base layer, there are serious shrinkage and cracking problems, resulting in high maintenance costs in the later stage and difficulty in project acceptance.
Sulfur aluminate cement is used as the only source of cement, and the amount of sulfur aluminate cement and the amount of flow retaining agent are controlled by adding the flow retaining agent β-cyclodextrin to achieve the effects of water reduction enhancement, low shrinkage rate and low flow loss.
The shrinkage and flow loss rate of gypsum self-leveling mortar is significantly reduced, and the absolute dry compressive strength is improved by 28 days, ensuring the flatness of the ground and construction quality.
Smart Images
Figure CN120229929A_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of building materials, and in particular relates to a gypsum self-leveling mortar with low shrinkage and low flow loss. Background Art
[0002] Gypsum self-leveling mortar is a gypsum-based dry mortar used for indoor floor leveling. As a floor leveling material, it has advantages that other materials cannot match, such as high construction floor leveling accuracy, small later shrinkage (compared with cement leveling mortar and cement self-leveling mortar), and not easy to hollow and crack. In recent years, more and more gypsum self-leveling mortar has been used to replace traditional cement mortar in floor leveling construction.
[0003] With the increasing application of gypsum self-leveling mortar, people have found that low-shrinkage gypsum self-leveling mortar on concrete and cement mortar bases has greatly reduced hollowing and cracking compared to cement leveling mortar and cement self-leveling products. However, ordinary gypsum self-leveling mortar on insulation board bases and floor heating pipe bases will still have serious shrinkage and cracking problems, which not only significantly increases the cost of later maintenance, but also has a great adverse impact on the project acceptance.
[0004] Although there are many studies on improving the shrinkage cracking problem of gypsum self-leveling mortar, such as by reasonably controlling the amount of hard filler, silicate cement, and sulphoaluminate cement, these improvement methods have more or less certain disadvantages, such as complex formula and high cost, uneven color of the molding surface, and uneven surface.
[0005] Therefore, the development of a low-shrinkage gypsum self-leveling product with simpler and more conventional components and good molding effect is of great significance for solving the leveling shrinkage and cracking problems of the insulation board base and the floor heating pipe base in actual construction. Summary of the invention
[0006] The inventors of the present invention have found in their long-term research on gypsum self-leveling materials that the type of cement selected has the greatest impact on the shrinkage cracking problem of gypsum self-leveling mortar. Avoiding the use of silicate cement, ordinary silicate cement, etc. and using sulfoaluminate cement alone can greatly improve the above-mentioned shrinkage cracking problem.
[0007] However, the inventors also found that the use of sulphoaluminate cement in gypsum self-leveling mortar will inevitably bring about the problem of large flow loss; that is, the 30-minute fluidity loss of gypsum self-leveling mortar containing sulphoaluminate cement will be greatly increased, which in turn brings about the problem of unqualified ground flatness after construction.
[0008] To this end, the inventors of the present invention continued to improve and studied a new gypsum self-leveling mortar, which uses sulphoaluminate cement as the entire source of cement, ensuring that the obtained gypsum self-leveling mortar has the effects of water reduction, enhancement, and low shrinkage; at the same time, by adding a flow retaining agent, the problem of large flow loss caused by sulphoaluminate cement is also solved, ultimately ensuring that the gypsum self-leveling mortar has the effects of low shrinkage and low flow loss.
[0009] The present invention specifically adopts the following technical solutions:
[0010] A low-shrinkage and low-flow-loss gypsum self-leveling mortar, comprising the following components uniformly mixed in parts by mass:
[0011]
[0012] Specifically, the cement is sulphoaluminate cement; further selected from any one of low-alkalinity sulphoaluminate cement, sulphoaluminate micro-expansive cement, and fast-hardening sulphoaluminate cement, or a mixture of two or three thereof.
[0013] Specifically, the flow retaining agent is β-cyclodextrin.
[0014] Generally, the gypsum is β-type semi-hydrated desulfurized gypsum powder.
[0015] Typically, the hard filler is stone powder and / or sand.
[0016] Generally, the water retaining agent is a cellulose and / or cellulose ether water retaining agent.
[0017] Generally, the water reducing agent is a polycarboxylic acid water reducing agent.
[0018] Generally, the retarder is a protein and / or amino acid retarder.
[0019] Generally, the defoaming agent is a silicone and / or polyether defoaming agent.
[0020] The above-mentioned gypsum self-leveling mortar provided by the present invention firstly utilizes sulphoaluminate cement as the only source of cement, and by controlling its specific dosage, it can not only achieve the effect of water reduction and strengthening, but also greatly reduce the shrinkage rate of the gypsum self-leveling mortar. Specifically, when the sulphoaluminate cement dosage is 0.3% to 5% of the gypsum cementitious material, compared with the case where no sulphoaluminate cement is added, the water consumption of the gypsum self-leveling mortar can be reduced by 6% to 9%, the 28d absolute dry compressive strength can be increased by 20% to 34%, and the shrinkage rate can be reduced by 38% to 81%. At the same time, it also avoids the problem of more local premature setting before the setting, and uneven surface after final setting, with a sense of bumps and depressions, and poor sensory perception.
[0021] Secondly, by adding a specific fluidity retention agent, the self-leveling gypsum mortar significantly reduces the large fluid loss problem caused by the application of sulfoaluminate cement. Generally, when the dosage of sulfoaluminate cement in the self-leveling gypsum mortar reaches the above range of the present invention, without a fluidity retention agent, the fluidity loss within 30 minutes can reach 5 mm to 15 mm; while for normal construction of a room with self-leveling gypsum, depending on the room size and construction thickness, the construction time is about 20 minutes to 40 minutes. If the 30-minute fluidity loss of the self-leveling gypsum mortar is too large, it will cause the formed surface to be uneven and the floor flatness to be unqualified. However, for the above self-leveling gypsum mortar of the present invention, the dosage of the fluidity retention agent is controlled to be 0.05% to 1% of the gypsum cementitious material, so that the 30-minute fluidity loss of the self-leveling gypsum mortar is reduced to 0 mm to 3 mm, thereby still having good self-leveling performance at 30 minutes and ensuring the qualified floor flatness during application.
[0022] The above self-leveling gypsum mortar provided by the present invention has a simple composition and conventional components, and can actually solve the problems of leveling shrinkage cracking and aesthetic requirements of the insulation board base layer and the underfloor heating pipe base layer in the application scenario of self-leveling gypsum during construction. BRIEF DESCRIPTION OF THE DRAWINGS
[0023] Figure 1 is the on-site construction effect diagram of the self-leveling gypsum mortar provided by Comparative Example 6 of the present invention. DETAILED DESCRIPTION OF THE INVENTION
[0024] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. However, the present invention can be implemented in many different forms and should not be construed as limited to the specific embodiments set forth herein. On the contrary, these embodiments are provided to explain the principles of the present invention and its practical applications, so that other technicians in the art can understand various embodiments of the present invention and various modifications suitable for specific intended applications.
[0025] The following Table 1 shows the compositions of the self-leveling gypsum mortars provided in Embodiments 1 to 8.
[0026] Each self-leveling gypsum mortar can be prepared by the following method: Mix the components such as gypsum, cement (specifically sulfoaluminate cement), fluidity retention agent (specifically β-cyclodextrin), hard filler, water retention agent, water reducing agent, setting retarder, defoaming agent, etc. in predetermined mass fractions evenly.
[0027] In order to verify the necessity of each component in the self-leveling gypsum mortar provided by the present invention, several comparative experiments were carried out. The compositions of the comparative self-leveling gypsum mortars provided in Comparative Examples 1 to 8 are also listed in Table 1.
[0028] Table 1 Composition (parts by mass) of each gypsum self-leveling mortar provided in Examples 1-8 and Comparative Examples 1-8
[0029]
[0030]
[0031] The performance test results of each gypsum self-leveling mortar provided in the above Examples 1-8 and Comparative Examples 1-8 are shown in Table 2.
[0032] Table 2 Performance test of each gypsum self-leveling mortar provided in Examples 1-8 and Comparative Examples 1-8
[0033]
[0034]
[0035] Note: When the dimensional change rate at 28d is negative, it means the actual dimensional change of the sample is shrinkage; when it is positive, it means the actual dimensional change of the sample is expansion.
[0036] From the performance test results of Examples 1-8, it can be seen that when the cement in the gypsum self-leveling mortar is only calcium sulfoaluminate cement and the content of calcium sulfoaluminate cement accounts for 0.3%-5% of the gypsum binder, the shrinkage rate of the gypsum self-leveling mortar of the present invention is 0.006%-0.020%; it is 38%-81% lower than the shrinkage rate of 0.032% of the ordinary gypsum self-leveling mortar in Comparative Example 2. The lower the shrinkage rate, the smaller the shrinkage stress, and the lower the risk of late cracking of the gypsum self-leveling mortar. It can be seen that replacing ordinary Portland cement with calcium sulfoaluminate cement in the gypsum self-leveling mortar can significantly reduce shrinkage cracking.
[0037] From the performance test results of Comparative Example 1, it can be seen that when no cement is added to the gypsum self-leveling mortar, its 28d absolute dry compressive strength is significantly lower than that of Examples 1-8; among them, the 28d absolute dry compressive strength of Example 3 is 34% higher than that of Comparative Example 1. However, when no cement is added to the gypsum self-leveling mortar, there are also disadvantages such as many bubbles, local early setting, uneven surface after final setting, and a sense of unevenness, which are difficult to be applied in actual construction.
[0038] Comparing the 30min fluidity loss performance of Examples 1 and 3 with those of Comparative Examples 3 and 4 respectively, when an appropriate fluidity retainer is added, the 30min fluidity loss of the gypsum self-leveling mortar of the present invention is 0mm-3mm; without adding a fluidity retainer, the 30min fluidity loss of the gypsum self-leveling mortar can reach 7mm-15mm.
[0039] By comparing Examples 1 and 3 with Comparative Examples 5 and 6 respectively, when the dosage of the fluidity retainer is too low, the 30-minute fluidity loss of the gypsum self-leveling material still reaches 5 mm to 10 mm. A large 30-minute fluidity loss will cause the surface of the on-site construction of the gypsum self-leveling material to be uneven and the flatness to be unqualified. As Figure 1 shown in the on-site construction surface condition of Comparative Example 6, due to its excessive 30-minute fluidity loss, the finally formed surface is uneven, with poor appearance and unqualified flatness.
[0040] By comparing the 28-day dimensional change rate performance of Example 3 with that of Comparative Example 7, it can be seen that when the dosage of the sulfoaluminate cement is 6% of the gypsum cementitious material, the shrinkage rate of the corresponding gypsum self-leveling mortar continues to increase, which is similar to the shrinkage rate of the ordinary gypsum self-leveling mortar in Comparative Example 2, and is not conducive to reducing the late shrinkage cracking. Therefore, although the sulfoaluminate cement can reduce the shrinkage rate, it is not that the larger the dosage, the better. Instead, the shrinkage problem of the gypsum self-leveling mortar can be reasonably solved only within a specific dosage range.
[0041] By comparing the 28-day dimensional change rate performance of Example 2 with that of Comparative Example 8, it can be seen that when, on the basis of the sulfoaluminate cement, an additional 42.5 ordinary Portland cement with a dosage of 0.5% of the gypsum cementitious material is added, the 28-day shrinkage rate of the gypsum self-leveling mortar increases from 0.01% to 0.03%. It can be seen that the method of compounding the sulfoaluminate cement and the Portland cement significantly increases the shrinkage rate of the gypsum mortar, and is also not conducive to reducing the late shrinkage cracking.
[0042] Although the present invention has been shown and described with reference to specific embodiments, those skilled in the art will understand that various changes in form and detail may be made herein without departing from the spirit and scope of the invention defined by the claims and their equivalents.
Claims
1. A self-leveling gypsum mortar with low shrinkage and low flow loss, characterized in that, Comprising the following components which are uniformly mixed according to parts by mass: Among them, the cement is sulfoaluminate cement, and the fluidity retention agent is β-cyclodextrin.
2. The self-leveling gypsum mortar according to claim 1, characterized in that, The cement is selected from at least one of low-alkalinity sulfoaluminate cement, sulfoaluminate slightly expanded cement, and rapid hardening sulfoaluminate cement.
3. The self-leveling gypsum mortar according to claim 1 or 2, characterized in that, The gypsum is β-type hemihydrate desulfurized gypsum powder.
4. The self-leveling gypsum mortar according to claim 3, characterized in that, The hard filler is selected from stone powder and / or sand.
5. The self-leveling gypsum mortar according to claim 3, wherein The water retention agent is selected from cellulose and / or cellulose ether water retention agents.
6. The self-leveling gypsum mortar according to claim 3, wherein, The water reducing agent is a polycarboxylic acid water reducing agent.
7. The self-leveling gypsum mortar according to claim 3, wherein The setting retarder is selected from protein-based and / or amino acid-based setting retarders.
8. The self-leveling gypsum mortar according to claim 3, characterized in that, The defoaming agent is selected from silicone-based and / or polyether-based defoaming agents.