A thiocyanate regulated micro-expanding cement-based self-leveling mortar and a preparation method thereof

Abstract

The application discloses a thiocyanate-regulated micro-expansion cement-based self-leveling mortar and a preparation method thereof, and belongs to the technical field of cement-based materials. The thiocyanate-regulated micro-expansion cement-based self-leveling mortar comprises the following raw materials in mass fractions: cementitious material 20-40 parts, fine aggregate 60-80 parts, ettringite growth control agent containing thiocyanate 1-3.04 parts, water-retaining agent 0.005-0.015 parts, water-reducing agent 0.4-0.8 parts and redispersible latex powder 0.4-0.6 parts; the cementitious material is a material with a sulfur-aluminum molar ratio of (1.45-1.65):1 and a total molar ratio of sulfur and aluminum iron of (1.05-1.35):1. The micro-expansion cement-based self-leveling mortar is a mortar with a setting time adjusted by the ettringite growth control agent, has the advantages of early high strength, controllable setting, good volume stability and the like, and can meet the requirements of rapid construction, accelerated production efficiency and the like.

Description

Technical Field

[0001] This invention relates to the field of cement-based materials technology, and in particular to a thiocyanate-regulated micro-expansion cement-based self-leveling mortar and its preparation method. Background Technology

[0002] Cement-based self-leveling mortar (SLM) is a powdered product made primarily of inorganic binders, with added fine aggregates, and modified with redispersible latex powder and various chemical additives, uniformly mixed through a specific production process. It is a highly developed, ready-to-use dry mixture that only needs to be mixed with a certain amount of water on-site. SLM is mainly used for renovating uneven substrates in old buildings or creating a smooth, flat surface for the final floor of new buildings. To meet construction requirements, SLM should possess excellent flowability in its fluid state and exhibit rapid hardening, high early strength, and volume stability in its hardened state.

[0003] In recent years, cement-based self-leveling mortars composed of silicate cement (PC), sulfoaluminate cement (SAC), and gypsum (CS) have attracted widespread attention due to their rapid setting and high early strength. However, these mortars require a large amount of chemical admixtures and a large volume of cement, resulting in high costs and poor compatibility. The evaporation and hydration reactions of cement can lead to volume shrinkage and surface cracking, affecting the durability of the mortar. Furthermore, there are problems such as difficulty in controlling the setting time and poor workability. Summary of the Invention

[0004] The purpose of this invention is to provide a thiocyanate-regulated micro-expansion cement-based self-leveling mortar and its preparation method, thereby solving the problems existing in the prior art. The micro-expansion cement-based self-leveling mortar of this invention possesses characteristics such as early strength, high strength, controllable setting, and good volume stability. It also exhibits excellent workability and mechanical properties, meeting the requirements for rapid construction and accelerating production efficiency.

[0005] To achieve the above objectives, the present invention provides the following solution:

[0006] One of the technical solutions of the present invention is a thiocyanate-regulated micro-expansion cement-based self-leveling mortar, comprising the following raw materials in parts by weight: 20-40 parts of cementitious material, 60-80 parts of fine aggregate, 1-3.04 parts of thiocyanate-containing ettringite growth control agent, 0.005-0.015 parts of water-retaining agent, 0.4-0.8 parts of water-reducing agent, and 0.4-0.6 parts of redispersible latex powder;

[0007] The cementing material is a material with a sulfur-aluminum (S / Al) molar ratio of (1.45-1.65):1 and a total sulfur-aluminum-iron (S / (Al+Fe)) molar ratio of (1.05-1.35):1.

[0008] The raw materials for the cementitious material include silicate cement, sulfoaluminate cement clinker, and gypsum.

[0009] Furthermore, the ettringite growth control agent containing thiocyanate comprises 0.01 to 0.04 parts by weight of ettringite growth retardant and 1 to 3 parts by weight of ettringite growth promoter; the ettringite growth promoter comprises thiocyanate.

[0010] Furthermore, the ettringite growth retardant includes organophosphates.

[0011] More preferably, the thiocyanate is sodium thiocyanate and / or calcium thiocyanate.

[0012] Furthermore, the fine aggregate includes standard sand; the water-retaining agent includes hydroxypropyl methylcellulose ether (HPMC); and the water-reducing agent includes polycarboxylate superplasticizer.

[0013] The second technical solution of the present invention: a method for preparing the above-mentioned thiocyanate-regulated micro-expansion cement-based self-leveling mortar, comprising the following steps:

[0014] The raw materials and water are stirred and mixed evenly to obtain the thiocyanate-regulated micro-expansion cement-based self-leveling mortar.

[0015] The third technical solution of the present invention: the application of the above-mentioned thiocyanate-regulated micro-expansion cement-based self-leveling mortar in the construction field.

[0016] The main technical concept of this invention lies in: adjusting the sulfur-aluminum molar ratio (S / Al) and sulfur-aluminum-iron molar ratio (S / (Al+Fe)) when using silicate cement, sulfoaluminate, and gypsum in combination, thereby determining that the S / Al molar ratio is between 1.45 and 1.65 and the S / (Al+Fe) molar ratio is between 1.05 and 1.35, resulting in the best overall performance of the micro-expansion cement-based self-leveling mortar; by adding an ettringite growth control agent, the problem of poor compatibility between chemical admixtures and the silicate cement-sulfoaluminate cement composite system is solved, allowing the setting time of the micro-expansion cement-based self-leveling mortar to meet the construction time requirements. Furthermore, ettringite growth control agents can alter the dissolution process of cement, thereby regulating the formation time and growth rate of ettringite (AFt) during hydration. The main hydration product of silicate cement, CSH gel, has significant shrinkage, while AFt has volume expansion. If the two are in an appropriate ratio during hydration, the cement stone will have good volume stability. Moreover, due to the denser structure of the cement stone, it also possesses early strength and high strength mechanical properties.

[0017] The present invention discloses the following technical effects:

[0018] (1) The dimensional change rate of the micro-expansion cement-based self-leveling mortar of the present invention is between 0.02 and 0.05, the initial setting time is 50 to 90 min, the 1-day compressive strength is ≥10 MPa, the 28-day compressive strength is ≥50 MPa, and all physical performance indicators are better than most self-leveling mortar products on the market.

[0019] (2) The micro-expansion cement-based self-leveling mortar of the present invention is a mortar whose setting time is adjusted by calcite growth control agent. It has the advantages of early strength, high strength, controllable setting and good volume stability, and can meet the requirements of rapid construction and accelerated production efficiency. Detailed Implementation

[0020] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0021] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0022] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0023] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0024] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0025] In the following examples, "parts" refers to "parts by weight".

[0026] The chemical composition of the materials used in this invention is as follows:

[0027] Table 1. XRF component analysis (wt.%)

[0028]

[0029] Example 1

[0030] A method for preparing thiocyanate-regulated micro-expansion cement-based self-leveling mortar:

[0031] The thiocyanate-regulated micro-expansion cement-based self-leveling mortar is composed of the following raw materials in parts by weight: 25 parts cementitious material, 75 parts standard sand, 1.01 parts ettringite growth control agent, 0.01 parts water-retaining agent (hydroxypropyl methylcellulose ether), 0.4 parts water-reducing agent (polycarboxylate superplasticizer), and 0.6 parts redispersible latex powder.

[0032] The cementitious material is a ternary cementitious material system consisting of 22.5 parts silicate cement, 1.5 parts sulfoaluminate cement clinker, and 1 part natural anhydrite, with an S / Al molar ratio of 1.45:1 and an S / (Al+Fe) molar ratio of 1.05:1.

[0033] The ettringite growth control agent consists of 0.01 parts of ettringite growth retardant (phosphonic acid) and 1 part of ettringite growth promoter (calcium thiocyanate).

[0034] Preparation method:

[0035] (1) Dry mix all raw materials except standard sand thoroughly, then add water (water-cement ratio of 0.5) and mix in a mortar mixer. The mixing procedure is as follows: slow mix at low speed for 30s, add standard sand and mix quickly for 30s, stop for 90s and scrape the powder adhering to the wall into the slurry, then mix quickly for 60s to obtain micro-expansion cement-based self-leveling mortar (PC-SAC composite cement-based self-leveling mortar).

[0036] The initial and 20-minute flowability and setting time of the micro-expansion cement-based self-leveling mortar prepared in this embodiment were tested according to the building materials standard JC / T985-2017. The results are shown in Table 2.

[0037] (2) The micro-expansion cement-based self-leveling mortar was poured into the mold and molded to a size of 40mm×40mm×160mm. It was immediately placed in a standard curing box for curing. After 8 hours, it was demolded and placed in water. It was cured at 20±1℃ for 1d, 3d, 7d and 28d. The strength test was carried out under a pressure machine with a rated load of 300kN and a loading rate of 2400N / s. The results are shown in Table 2.

[0038] The expansion performance of the micro-expansion cement-based self-leveling mortar in this embodiment was determined according to the building materials standard JC / T985-2017, and the results are shown in Table 2.

[0039] Example 2

[0040] A method for preparing thiocyanate-regulated micro-expansion cement-based self-leveling mortar:

[0041] The thiocyanate-regulated micro-expansion cement-based self-leveling mortar is composed of the following raw materials in parts by weight: 25 parts cementitious material, 75 parts standard sand, 1.02 parts ettringite growth control agent, 0.01 parts water-retaining agent (hydroxypropyl methylcellulose ether), 0.8 parts water-reducing agent (polycarboxylate superplasticizer), and 0.4 parts redispersible latex powder.

[0042] The cementing material is a ternary cementing material system consisting of 20 parts silicate cement, 3 parts sulfoaluminate cement clinker, and 2 parts natural anhydrite, with an S / Al molar ratio of 1.5:1 and an S / (Al+Fe) molar ratio of 1.15:1.

[0043] The ettringite growth control agent consists of 0.02 parts of ettringite growth retardant (ethylphosphonic acid) and 1 part of ettringite growth promoter (calcium thiocyanate).

[0044] Preparation method:

[0045] (1) Dry mix all raw materials except standard sand thoroughly, then add water (water-cement ratio of 0.5) and mix in a mortar mixer. The mixing procedure is as follows: slow mix at low speed for 30s, add standard sand and mix quickly for 30s, stop for 90s and scrape the powder adhering to the wall into the slurry, then mix quickly for 60s to obtain micro-expansion cement-based self-leveling mortar (PC-SAC composite cement-based self-leveling mortar).

[0046] The initial and 20-minute flowability and setting time of the micro-expansion cement-based self-leveling mortar prepared in this embodiment were tested according to the building materials standard JC / T985-2017. The results are shown in Table 2.

[0047] (2) The micro-expansion cement-based self-leveling mortar was poured into the mold and molded to a size of 40mm×40mm×160mm. It was immediately placed in a standard curing box for curing. After 8 hours, it was demolded and placed in water. It was cured at 20±1℃ for 1d, 3d, 7d and 28d. The strength test was carried out under a pressure machine with a rated load of 300kN and a loading rate of 2400N / s. The results are shown in Table 2.

[0048] The expansion performance of the micro-expansion cement-based self-leveling mortar in this embodiment was determined according to the building materials standard JC / T985-2017, and the results are shown in Table 2.

[0049] Example 3

[0050] A method for preparing thiocyanate-regulated micro-expansion cement-based self-leveling mortar:

[0051] The thiocyanate-regulated micro-expansion cement-based self-leveling mortar is composed of the following raw materials in parts by weight: 25 parts cementitious material, 75 parts standard sand, 1.03 parts ettringite growth control agent, 0.01 parts water-retaining agent (hydroxypropyl methylcellulose ether), 0.6 parts water-reducing agent (polycarboxylate superplasticizer), and 0.5 parts redispersible latex powder.

[0052] The cementing material is a ternary cementing material system consisting of 18.75 parts of silicate cement, 3.75 parts of sulfoaluminate cement clinker, and 2.5 parts of natural anhydrite, with an S / Al molar ratio of 1.6:1 and an S / (Al+Fe) molar ratio of 1.25:1.

[0053] The ettringite growth control agent consists of 0.03 parts of ettringite growth retardant (ethosonic acid) and 1 part of ettringite growth promoter (sodium thiocyanate).

[0054] Preparation method:

[0055] (1) Dry mix all raw materials except standard sand thoroughly, then add water (water-cement ratio of 0.5) and mix in a mortar mixer. The mixing procedure is as follows: slow mix at low speed for 30s, add standard sand and mix quickly for 30s, stop for 90s and scrape the powder adhering to the wall into the slurry, then mix quickly for 60s to obtain micro-expansion cement-based self-leveling mortar (PC-SAC composite cement-based self-leveling mortar).

[0056] The initial and 20-minute flowability and setting time of the micro-expansion cement-based self-leveling mortar prepared in this embodiment were tested according to the building materials standard JC / T985-2017. The results are shown in Table 2.

[0057] (2) The micro-expansion cement-based self-leveling mortar was poured into the mold and molded to a size of 40mm×40mm×160mm. It was immediately placed in a standard curing box for curing. After 8 hours, it was demolded and placed in water. It was cured at 20±1℃ for 1d, 3d, 7d and 28d. The strength test was carried out under a pressure machine with a rated load of 300kN and a loading rate of 2400N / s. The results are shown in Table 2.

[0058] The expansion performance of the micro-expansion cement-based self-leveling mortar in this embodiment was determined according to the building materials standard JC / T985-2017, and the results are shown in Table 2.

[0059] Example 4

[0060] A method for preparing thiocyanate-regulated micro-expansion cement-based self-leveling mortar:

[0061] Thiocyanate-regulated micro-expansion cement-based self-leveling mortar is composed of the following raw materials in parts by weight: 25 parts cementitious material, 75 parts standard sand, 1.04 parts ettringite growth control agent, 0.01 parts water-retaining agent (hydroxypropyl methylcellulose ether), 0.6 parts water-reducing agent (polycarboxylate superplasticizer), and 0.5 parts redispersible latex powder.

[0062] The cementing material is a ternary cementing material system consisting of 16.25 parts of silicate cement, 5.25 parts of sulfoaluminate cement clinker, and 3.5 parts of natural anhydrite, with an S / Al molar ratio of 1.65:1 and an S / (Al+Fe) molar ratio of 1.35:1.

[0063] The ettringite growth control agent consists of 0.04 parts of ettringite growth retardant (ethosonic acid) and 1 part of ettringite growth promoter (sodium thiocyanate).

[0064] Preparation method:

[0065] (1) Dry mix all raw materials except standard sand thoroughly, then add water (water-cement ratio of 0.5) and mix in a mortar mixer. The mixing procedure is as follows: slow mix at low speed for 30s, add standard sand and mix quickly for 30s, after 30s of quick mixing, stop for 90s and scrape the powder adhering to the wall into the slurry, then mix quickly for 60s to obtain micro-expansion cement-based self-leveling mortar (PC-SAC composite cement-based self-leveling mortar).

[0066] The initial and 20-minute flowability and setting time of the micro-expansion cement-based self-leveling mortar prepared in this embodiment were tested according to the building materials standard JC / T985-2017. The results are shown in Table 2.

[0067] (2) The micro-expansion cement-based self-leveling mortar was poured into the mold and molded to a size of 40mm×40mm×160mm. It was immediately placed in a standard curing box for curing. After 8 hours, it was demolded and placed in water. It was cured at 20±1℃ for 1d, 3d, 7d and 28d. The strength test was carried out under a pressure machine with a rated load of 300kN and a loading rate of 2400N / s. The results are shown in Table 2.

[0068] The expansion performance of the micro-expansion cement-based self-leveling mortar in this embodiment was determined according to the building materials standard JC / T985-2017, and the results are shown in Table 2.

[0069] Comparative Example 1

[0070] Same as Example 1, except that the cementing material is a ternary cementing material system consisting of 23.75 parts of silicate cement, 0.75 parts of sulfoaluminate cement clinker, and 0.5 parts of natural anhydrite, with an S / Al molar ratio of 1.35:1 and an S / (Al+Fe) molar ratio of 0.95:1.

[0071] Comparative Example 2

[0072] Same as Example 1, except that the cementing material is a ternary cementing material system consisting of 15 parts silicate cement, 6 parts sulfoaluminate cement clinker, and 4 parts natural anhydrite, with an S / Al molar ratio of 1.75:1 and an S / (Al+Fe) molar ratio of 1.45:1.

[0073] Table 2 Physical Properties of PC-SAC Composite Cement-Based Self-Leveling Mortar

[0074]

[0075] As shown in Table 2, the mechanical strength of all embodiments is higher than that of the comparative examples. Among them, the mortar of Example 2 has the best mechanical properties at 1 day, which is 13.12 MPa. The mortar of Example 4 has the best mechanical properties at 28 days, which is 56.10 MPa. The longer initial and final setting time interval of Example 4 makes it easier to operate and has the best workability. Furthermore, the mortar of Example 4 has the lowest free expansion rate and the best volume stability at 28 days.

[0076] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A micro-expansion cement-based self-leveling mortar with thiocyanate-regulated setting time, characterized in that, The raw materials include the following parts by weight: 20-40 parts of cementitious material, 60-80 parts of fine aggregate, 1.01-1.04 parts of ettringite growth control agent containing thiocyanate, 0.005-0.015 parts of water-retaining agent, 0.4-0.8 parts of water-reducing agent, and 0.4-0.6 parts of redispersible latex powder; The cementing material is a material with a sulfur-aluminum molar ratio of (1.45~1.65):1 and a total sulfur-aluminum-iron molar ratio of (1.05~1.35):1; The raw materials for the cementitious material include silicate cement, sulfoaluminate cement clinker, and gypsum. The ettringite growth control agent containing thiocyanate comprises 0.01-0.04 parts by weight of ettringite growth retardant and 1 part by weight of ettringite growth promoter; the ettringite growth promoter comprises thiocyanate. The ettringite growth retardant includes organophosphates.

2. The micro-expansion cement-based self-leveling mortar with thiocyanate-regulated setting time according to claim 1, characterized in that, The fine aggregate includes standard sand; the water-retaining agent includes hydroxypropyl methylcellulose ether; and the water-reducing agent includes polycarboxylate superplasticizer.

3. A method for preparing a micro-expansion cement-based self-leveling mortar with thiocyanate-regulated setting time as described in any one of claims 1 to 2, characterized in that, Includes the following steps: The raw materials and water are stirred and mixed evenly to obtain the micro-expansion cement-based self-leveling mortar with thiocyanate-controlled setting time.

4. The application of the micro-expansion cement-based self-leveling mortar with thiocyanate-controlled setting time as described in any one of claims 1 to 2 in the construction field.

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