Sulphoaluminate cement-based super-early-strength UHPC (Ultra High Performance Concrete) composite water reducing agent and preparation method thereof

Abstract

The invention discloses a sulphoaluminate cement-based super-early-strength UHPC (Ultra High Performance Concrete) composite water reducing agent and a preparation method thereof. The sulphoaluminate cement-based super-early-strength UHPC composite water reducing agent is prepared from the following components in parts by weight: 100 parts of a modified polycarboxylic acid water reducing agent; 10 to 20 parts of nano graphene oxide (GO) dispersion liquid; 15 to 20 parts of an internal curing anti-cracking agent; 0.3 to 0.5 part of a stabilizing agent; and 200 to 230 parts of water. The preparation method comprises the following steps: synthesizing the modified polycarboxylate superplasticizer; preparation of a nano graphene oxide GO dispersion liquid; the step of internal curing comprises preparation of an anti-cracking agent; the stabilizer is compounded; the materials are uniformly mixed in proportion and then are subjected to high-speed shearing treatment to obtain a homogeneous liquid product. According to the invention, the setting time of the UHPC can be accurately controlled, the tensile strength and toughness of the UHPC are improved, and the problems of insufficient construction time, early cracking and the like are avoided.

Description

Technical Field

[0001] The present application belongs to the field of building materials technology, and specifically relates to a sulphoaluminate cement-based ultra-early strength UHPC composite water reducer and a preparation method, which is particularly suitable for engineering scenarios requiring rapid setting, high early strength and crack resistance. Background Art

[0002] Ultra-high performance concrete (UHPC), as a new building material with excellent mechanical properties and durability, has shown great application potential in many fields. Sulphoaluminate cement (SAC) is widely used in the preparation of ultra-early-strength UHPC because of its rapid early hydration and rapid strength development, making it particularly suitable for scenarios such as emergency repairs and winter construction. However, its rapid setting characteristics lead to a short construction window, and the concentrated hydration heat release and large volume changes can easily cause cracking, affecting durability. Traditional polycarboxylate water reducers have problems such as poor adaptability and insufficient retarding effect in SAC systems. In addition, the existing technology mostly focuses on silicate cement systems and lacks special water reducers for SAC. In addition, the high amount of adhesive and low water-to-binder ratio in UHPC can easily lead to high viscosity and poor fluidity. At the same time, the early cement heat release is concentrated and the volume deformation is significant. Existing patents (such as CN117209688B) improve shrinkage reduction by introducing hydrophobic groups, but do not solve the contradiction between rapid setting and cracking in the SAC system.

[0003] Therefore, there is an urgent need to develop a composite water reducer that can be well adapted to sulphoaluminate cement and has the advantages of high efficiency water reduction, precise retarding of setting, and anti-cracking enhancement. Summary of the Invention

[0004] In view of the shortcomings or deficiencies of the above-mentioned prior art, the technical problem to be solved by this application is to provide a sulphoaluminate cement-based ultra-early strength UHPC composite water reducer and a preparation method, which can accurately control the setting time of UHPC, improve the tensile strength and toughness of UHPC itself, and avoid problems such as insufficient construction time and early cracking.

[0005] To solve the above technical problems, this application is implemented through the following technical solutions:

[0006] On the one hand, the present application proposes a sulphoaluminate cement-based ultra-early strength UHPC composite water reducer, which is composed of the following components in parts by weight:

[0007] 100 parts of modified polycarboxylate water reducer;

[0008] 10-20 parts of nanographene oxide (GO) dispersion;

[0009] Internal curing - anti-cracking agent 15 to 20 parts;

[0010] 0.3-0.5 parts of stabilizer;

[0011] 200-230 parts of water.

[0012] Further optionally, the modified polycarboxylic acid water reducer is copolymerized by isopentenyl polyoxyethylene ether (IPEG, molecular weight 2400), acrylic acid (AA), 2-acrylamide-2-methylpropanesulfonic acid (AMPS), and borate monomer (BEM, prepared by reacting hydroxyethyl acrylate and phenylboric acid in a molar ratio of 1:1).

[0013] Further optionally, the molar ratio of isopentenyl polyoxyethylene ether (IPEG): acrylic acid (AA): 2-acrylamide-2-methylpropanesulfonic acid (AMPS): borate ester monomer (BEM) is 1: (2.8-3): (0.5-0.7): (0.2-0.3).

[0014] Further optionally, the borate ester monomer (BEM) is prepared by reacting hydroxyethyl acrylate and phenylboric acid in a molar ratio of 1:1.

[0015] Further optionally, the solid content of the nano-graphene oxide (GO) dispersion is 2%, and the GO sheet diameter is less than 500 nm.

[0016] Further optionally, the internal curing and anti-cracking agent is compounded by cross-linked sodium polyacrylate (SAP) and nano-MgO in a ratio of 3:1; wherein the SAP particle size is 80-100 μm, and the MgO particle size is 40-50 nm.

[0017] Further optionally, the stabilizer is a silicone water-soluble powder stabilizer, the effective substance content of which is not less than 99%, and the retention amount on a 22-mesh sieve is not more than 5%.

[0018] The present application also proposes a method for preparing a sulphoaluminate cement-based ultra-early strength UHPC composite water reducer, the preparation method comprising:

[0019] Synthesis of the modified polycarboxylate water-reducing agent;

[0020] Preparation of the nano graphene oxide GO dispersion;

[0021] Preparation of the internal curing-anti-cracking agent;

[0022] Compounding of the stabilizer;

[0023] The above materials are mixed evenly according to the proportions and then subjected to high-speed shearing treatment to obtain a homogeneous liquid product.

[0024] Further optionally, in the synthesis of the above-mentioned modified polycarboxylate water reducer, the process includes: mixing isopentenyl polyoxyethylene ether (IPEG): acrylic acid (AA): 2-acrylamide-2-methylpropanesulfonic acid (AMPS): borate monomer (BEM) in proportion, adding a chain transfer agent thioglycolic acid and an initiator ammonium persulfate, and conducting a free radical copolymerization reaction in a 60°C aqueous solution for 4 hours to obtain a modified polycarboxylate water reducer containing borate groups; wherein, the modified polycarboxylate main chain is grafted with a retarding group: introducing a retarding functional monomer containing borate into the polycarboxylic acid molecule can effectively delay the early hydration of sulphoaluminate cement (SAC).

[0025] And / or, in the preparation of the above-mentioned nano-graphene oxide (GO) dispersion, the method includes: ultrasonically dispersing graphene oxide in water, adding polydopamine (PDA) for surface modification, and obtaining a stably dispersed nano-graphene oxide (GO) dispersion; the dispersion effect of the nano-graphene oxide (GO) is utilized to promote the densification of the hydration product, while serving as an early strength agent to improve the early strength.

[0026] Further optionally, in the preparation of the above-mentioned internal curing-anti-cracking agent, the process includes: dry-mixing cross-linked sodium polyacrylate (SAP) and nano-MgO evenly, adding a silane coupling agent (KH560) for surface modification, and obtaining the internal curing-anti-cracking agent; the internal curing-anti-cracking agent is compounded with super absorbent polymer (SAP) and nano-magnesium oxide (MgO) to achieve dual anti-cracking effects of internal curing and micro-expansion.

[0027] Compared with the existing technology, this application has the following technical effects:

[0028] The present invention introduces a borate-containing retarding functional monomer into the polycarboxylic acid molecule, and the boric acid group reacts with the Ca in SAC to form a retarding monomer. 2+ Complexation accurately inhibits the rapid formation of ettringite, achieving a retarding effect without affecting the later strength development. Compared with traditional retarders such as sodium gluconate, the retarder of this application has better adaptability and retarding effect in sulphoaluminate cement (SAC) system;

[0029] At the same time, the present application utilizes the dispersion effect and two-dimensional layer structure of nanographene oxide (GO) to promote the densification of hydration products and improve the mechanical properties and durability of concrete;

[0030] The nano-graphene oxide (GO) dispersion in this application is used as an early strength agent to improve the early strength of concrete, and the surface modification with polydopamine (PDA) further improves the dispersibility and stability of nano-graphene oxide (GO) in the cement matrix;

[0031] This application uses a combination of superabsorbent polymer (SAP) and nanomagnesium oxide (MgO) as an anti-cracking agent, achieving both internal curing and micro-expansion anti-cracking effects. The superabsorbent polymer (SAP) absorbs and stores water, slowly releasing it during the concrete hardening process, promoting later hydration reactions and reducing shrinkage stress. Furthermore, the nano-MgO hydration produces delayed micro-expansion, further offsetting shrinkage stress and improving the concrete's crack resistance. DETAILED DESCRIPTION

[0032] The following is a clear and complete description of the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of them. Based on the embodiments of this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0033] The raw materials and specifications are subject to those described in the specific embodiments.

[0034] In one embodiment of the present application, the benchmark mix ratio of sulphoaluminate cement-based ultra-early strength UHPC is as follows:

[0035] Table 1: Sulphoaluminate cement-based ultra-early strength UHPC benchmark mix proportions

[0036]

[0037] The preparation methods of the water reducer and UHPC in the following examples are as follows:

[0038] Step 1: Synthesis of a modified polycarboxylate superplasticizer: IPEG, AA, AMPS, and BEM were mixed in appropriate proportions. Thioglycolic acid (4% of the total monomer weight) and ammonium persulfate (1.3% of the total monomer weight) were added as a chain transfer agent. Free radical copolymerization was carried out in aqueous solution at 60°C for 4 hours to obtain a polycarboxylate superplasticizer containing borate groups.

[0039] Step 2: Preparation of nano-graphene oxide (GO) dispersion: Graphene oxide is ultrasonically dispersed in water, and polydopamine (PDA) is added for surface modification to obtain a stably dispersed nano-graphene oxide (GO) dispersion.

[0040] Step 3: Preparation of internal curing and anti-cracking agent: After dry-mixing polydopamine (PDA) and nano-MgO, silane coupling agent (KH560) was added for surface modification to enhance the interfacial bonding with the cement matrix.

[0041] Step 4: Compounding of water reducer: Modified polycarboxylate water reducer, nanographene oxide (GO) dispersion, internal curing-anti-cracking agent, stabilizer, and water are mixed uniformly in proportion and then treated with high-speed shear (8000 rpm, 30 min) to obtain a homogeneous liquid product.

[0042] Step 5: Add the compounded water reducer mentioned above into a laboratory concrete forced mixer according to the ratio of cement: silica fume: quartz sand: steel fiber: water reducer: water = 900:150:1050:150:10:185 in Table 1 and stir for 5 minutes to obtain ultra-early strength UHPC.

[0043] The performance testing methods in the following embodiments are as follows:

[0044] Determination of mechanical properties: carried out in accordance with the relevant provisions of GB / T 31387 "Reactive Powder Concrete" and T / CBMF 37 "Basic Properties and Test Methods of Ultra-High Performance Concrete".

[0045] Determination of fluidity: carried out in accordance with the relevant provisions of GB / T 50080 "Standard for test methods of properties of ordinary concrete mixtures".

[0046] Volume stability and durability: Conduct according to the relevant provisions of GB / T 50082 "Standard for Test Methods of Long-term Properties and Durability of Ordinary Concrete".

[0047] Example 1

[0048] This embodiment provides a sulphoaluminate cement-based composite water reducer specifically for ultra-early strength UHPC, comprising the following components in parts by weight: 100 parts of a modified polycarboxylate water reducer; 10 parts of a nano-graphene oxide dispersion; 15 parts of an internal curing and anti-cracking agent; 0.3 parts of a stabilizer; and 200 parts of water.

[0049] The modified polycarboxylic acid water reducer is copolymerized by isopentenyl polyoxyethylene ether (IPEG, molecular weight 2400), acrylic acid (AA), 2-acrylamide-2-methylpropanesulfonic acid (AMPS), and borate monomer (BEM, prepared by the reaction of hydroxyethyl acrylate and phenylboric acid in a molar ratio of 1:1), wherein the molar ratio of IPEG:AA:AMPS:BEM is 1:2.8:0.5:0.2; the nanographene oxide (GO) dispersion has a solid content of 2% and a GO flake diameter of 400 nm; the internal curing-anti-cracking agent is a compound of cross-linked sodium polyacrylate (SAP) and nano-MgO in a ratio of 3:1, wherein the SAP particle size is 80 μm and the MgO particle size is 40 nm; the stabilizer is a water-soluble silicone powder stabilizer with an effective substance content of 99.0% and a retention capacity of 5.0% on a 22-mesh sieve; and tap water is used.

[0050] Example 2

[0051] This embodiment provides a sulphoaluminate cement-based composite water reducer specifically for ultra-early strength UHPC, comprising the following components in parts by weight: 100 parts of a modified polycarboxylate water reducer; 20 parts of a nano-graphene oxide dispersion; 20 parts of an internal curing / anti-cracking agent; 0.5 parts of a stabilizer; and 230 parts of water.

[0052] The modified polycarboxylic acid water reducer is copolymerized by isopentenyl polyoxyethylene ether (IPEG, molecular weight 2400), acrylic acid (AA), 2-acrylamide-2-methylpropanesulfonic acid (AMPS), and borate monomer (BEM, prepared by the reaction of hydroxyethyl acrylate and phenylboric acid in a molar ratio of 1:1), with the molar ratio of IPEG:AA:AMPS:BEM being 1:3:0.7:0.3. The nanographene oxide (GO) dispersion has a solid content of 2% and a GO flake diameter of 450 nm. The internal curing and anti-cracking agent is a mixture of cross-linked sodium polyacrylate (SAP) and nano-MgO in a ratio of 3:1, with a SAP particle size of 100 μm and a MgO particle size of 50 nm. The stabilizer is a water-soluble silicone powder stabilizer with an effective substance content of 99.5% and a retention rate of 4.5% on a 22-mesh sieve. Tap water is used.

[0053] Example 3

[0054] A sulphoaluminate cement-based composite water reducer specifically for ultra-early strength UHPC is composed of the following components in parts by weight: 100 parts of a modified polycarboxylate water reducer; 15 parts of a nano-graphene oxide dispersion; 18 parts of an internal curing and anti-cracking agent; 0.4 parts of a stabilizer; and 220 parts of water.

[0055] The modified polycarboxylic acid water reducer is copolymerized by isopentenyl polyoxyethylene ether (IPEG, molecular weight 2400), acrylic acid (AA), 2-acrylamide-2-methylpropanesulfonic acid (AMPS), and borate monomer (BEM, prepared by the reaction of hydroxyethyl acrylate and phenylboric acid in a molar ratio of 1:1), with the molar ratio of IPEG:AA:AMPS:BEM being 1:2.9:0.6:0.25. The nanographene oxide (GO) dispersion has a solid content of 2% and a GO flake diameter of 400 nm. The internal curing and anti-cracking agent is a mixture of cross-linked sodium polyacrylate (SAP) and nano-MgO in a ratio of 3:1, with a SAP particle size of 90 μm and a MgO particle size of 45 nm. The stabilizer is a water-soluble silicone powder stabilizer with an active substance content of 99.8% and a retention rate of 4.0% on a 22-mesh sieve. Tap water is used.

[0056] The weight proportions of the raw materials of the sulphoaluminate cement-based ultra-early strength UHPC special composite water reducer described in Examples 1 to 3 are shown in Table 2.

[0057] Table 2: Weight ratio of each raw material

[0058]

[0059] Ultra-early strength UHPC was mixed according to the mix ratio in Table 2 above and the performance test was carried out, wherein the water reducer dosage of the control group was 0. The performance test results of Examples 1 to 3 are shown in Table 3.

[0060] Table 3: Performance test results of different embodiments

[0061]

[0062]

[0063] From the above data, it can be seen that the UHPC prepared with the sulphoaluminate cement-based ultra-early strength UHPC composite water-reducing agent described in this application has an initial expansion of more than 680mm, which is a significant improvement compared to the 300mm in the control group, indicating that its water-reducing effect is obvious. At the same time, the expansion after 30 minutes is still not less than 650mm, and it has self-leveling construction performance, while the control group has already begun to set, the expansion is zero, and it is difficult to apply in construction. Moreover, the ultimate tensile strength of the present application is more than 7MPa in 2h, and the compressive strength is more than 70MPa, which is significantly improved compared to the control group that has not yet been finally set in 2h. Moreover, the 28d drying shrinkage rate is less than 100×10 -6 , early crack resistance grade V, about 300×10 -6 The drying shrinkage rate and early crack resistance grade of Class III have better volume stability and early crack resistance, reducing the risk of cracking caused by rapid construction and improving the volume stability and reliability of the structure in UHPC construction applications. The sulphoaluminate cement-based ultra-early strength UHPC special composite water reducer described in this application is well compatible with sulphoaluminate cement, and has the functions of efficient water reduction, precise retarding, and crack resistance enhancement. The formulated UHPC has the characteristics of good workability, ultra-early strength, high early crack resistance, high volume stability and good durability, and has excellent comprehensive performance. It is suitable for fast repair and fast construction projects with requirements such as self-leveling construction, high tensile strength, and high reliability.

[0064] In the description of this application, unless otherwise expressly specified or limited, the terms "connected," "connect," and "fixed" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integration; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; and can refer to internal communication between two components or interaction between two components. Those skilled in the art will understand the specific meanings of the above terms in this application based on specific circumstances.

[0065] In this application, unless otherwise expressly specified or limited, a first feature being "above" or "below" a second feature may include the first and second features being in direct contact, or may include the first and second features being in contact not directly but through another feature between them. Moreover, a first feature being "above," "above," and "above" a second feature may include the first feature being directly above or obliquely above the second feature, or may simply mean that the first feature is higher in level than the second feature. A first feature being "below," "below," and "below" a second feature may include the first feature being directly below or obliquely below the second feature, or may simply mean that the first feature is lower in level than the second feature.

[0066] The above embodiments are intended only to illustrate the technical solutions of the present application and are not intended to limit the present application. The present application is described in detail with reference to the preferred embodiments. It should be understood by those skilled in the art that the technical solutions of the present application may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present application and should be included within the scope of the claims of the present application.

Claims

1. A sulphoaluminate cement-based ultra-early strength UHPC composite water reducer, characterized in that: It is composed of the following components in parts by weight: 100 parts of modified polycarboxylate water reducer; 10-20 parts of nanographene oxide (GO) dispersion; Internal curing - anti-cracking agent 15 to 20 parts; 0.3-0.5 parts of stabilizer; 200-230 parts of water.

2. The sulphoaluminate cement-based ultra-early strength UHPC composite water reducer according to claim 1, characterized in that: The modified polycarboxylic acid water reducer is copolymerized by isopentenyl polyoxyethylene ether (IPEG, molecular weight 2400), acrylic acid (AA), 2-acrylamide-2-methylpropanesulfonic acid (AMPS), and borate monomer (BEM, prepared by reacting hydroxyethyl acrylate and phenylboric acid in a molar ratio of 1:1).

3. The sulphoaluminate cement-based ultra-early strength UHPC composite water reducer according to claim 2, characterized in that: The molar ratio of the isopentenyl polyoxyethylene ether (IPEG): acrylic acid (AA): 2-acrylamide-2-methylpropanesulfonic acid (AMPS): borate ester monomer (BEM) is 1: (2.8-3): (0.5-0.7): (0.2-0.3).

4. The sulphoaluminate cement-based ultra-early strength UHPC composite water reducer according to claim 2, characterized in that: The borate ester monomer (BEM) is prepared by reacting hydroxyethyl acrylate and phenylboric acid in a molar ratio of 1:

1.

5. The sulphoaluminate cement-based ultra-early strength UHPC composite water reducer according to claim 1, characterized in that: The solid content of the nano-graphene oxide (GO) dispersion is 2%, and the GO sheet diameter is less than 500 nm.

6. The sulphoaluminate cement-based ultra-early strength UHPC composite water reducer according to claim 1, characterized in that: The internal curing and anti-cracking agent is compounded by cross-linked sodium polyacrylate (SAP) and nano-MgO in a ratio of 3:1; wherein the SAP particle size is 80-100 μm, and the MgO particle size is 40-50 nm.

7. The sulphoaluminate cement-based ultra-early strength UHPC composite water reducer according to claim 1, characterized in that: The stabilizer is a water-soluble organic silicon powder stabilizer, the effective substance content of which is not less than 99%, and the retention amount on a 22-mesh sieve is not more than 5%.

8. A method for preparing the sulphoaluminate cement-based ultra-early strength UHPC composite water reducer according to any one of claims 1 to 7, characterized in that: The preparation method comprises: Synthesis of the modified polycarboxylate water-reducing agent; Preparation of the nano graphene oxide GO dispersion; Preparation of the internal curing-anti-cracking agent; Compounding of the stabilizer; The above materials are mixed evenly according to the proportions and then subjected to high-speed shearing treatment to obtain a homogeneous liquid product.

9. The preparation method according to claim 8, characterized in that In the synthesis of the modified polycarboxylate water reducer, the process includes: mixing isopentenyl polyoxyethylene ether (IPEG), acrylic acid (AA), 2-acrylamide-2-methylpropanesulfonic acid (AMPS), and borate monomer (BEM) in a certain proportion, adding a chain transfer agent, thioglycolic acid, and an initiator, ammonium persulfate, and performing a free radical copolymerization reaction in a 60° C. aqueous solution for a certain hour to obtain a modified polycarboxylate water reducer containing a borate group; And / or, in the preparation of the above-mentioned nano-graphene oxide (GO) dispersion, the process includes: ultrasonically dispersing graphene oxide in water, adding polydopamine (PDA) for surface modification, and obtaining a stably dispersed nano-graphene oxide (GO) dispersion.

10. The preparation method according to claim 8, characterized in that The preparation of the above-mentioned internal curing and anti-cracking agent includes: dry-mixing cross-linked sodium polyacrylate (SAP) and nano-MgO uniformly, adding a silane coupling agent (KH560) for surface modification, and obtaining the internal curing and anti-cracking agent.

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