Microporous low-shrinkage concrete and preparation method thereof

Abstract

The invention provides microporous low-shrinkage concrete and a preparation method thereof, and belongs to the field of concrete.The microporous low-shrinkage concrete is prepared from, by weight, 300-380 parts of cement, 30-70 parts of fly ash, 250-350 parts of medium sand, 1200-1550 parts of guar stone, 5-10 parts of silica fume, 2-4 parts of dihydrate gypsum, 0.5-2 parts of water glass, 2-5 parts of a water reducing agent, 0.1-0.3 part of a retarder, 4-8 parts of rubber powder, 0.02-0.08 part of a thickening agent and 2-6 parts of water absorption fibers. 110 to 150 parts of water; and the porosity of the microporous low-shrinkage concrete is 8-10%. Through innovative material design and a synergistic effect, comprehensive improvement of waterproofness, crack resistance, construction performance and economical efficiency is achieved, seepage water can be changed from blocking to dredging through a unique micropore structure, and the efficient and durable anti-seepage effect is achieved; meanwhile, the stability of a base layer is guaranteed through high strength, strong bonding force is formed with a surface layer, and hollowing and cracking are effectively eradicated; in addition, the water-absorbing fiber internal curing component and the expansion component cooperate, so that the cracking risk is avoided, and the long-term stability and safety of the floor system are guaranteed.

Description

Technical Field

[0001] This invention relates to the field of concrete technology, specifically to a microporous low-shrinkage concrete and its preparation method. Background Technology

[0002] Water seepage risk in basements is a critical control point in the entire basement construction process. The common practice is to apply a flexible waterproofing layer to the structural slab, followed by a 100-150mm thick layer of fiber-reinforced C30 / P8 waterproof concrete as the base layer. In a basement environment prone to seepage, the effectiveness of this waterproofing system rests entirely on the flexible waterproofing layer. If the waterproofing layer is damaged during construction, water will bypass the point of failure and flow between the waterproofing layer and the base concrete, seeping out through weak points (such as construction joints and cracks), turning a "point leak" into a "surface leak," making repairs extremely difficult. Simultaneously, the inherent drying and temperature shrinkage of concrete can cause cracking. Even with the addition of fibers, cracking can only be inhibited, not completely eliminated. These cracks become rapid channels for water, causing the waterproofing effect of the base concrete to fail. Once seepage occurs, water flows across the waterproofing layer beneath the base concrete, making it difficult to accurately locate the leak point, and traditional repair methods (such as grouting) are often ineffective in completely eliminating the problem.

[0003] In view of this, it is necessary to design a microporous low-shrinkage concrete and its preparation method to solve the above problems. Summary of the Invention

[0004] In view of the technical problems existing in the background art, this application provides a microporous low-shrinkage concrete and its preparation method, aiming to solve the technical problems in the existing basement waterproofing system, which are difficult to locate leakage points, difficult to repair, and have low reliability due to the easy damage of the flexible waterproofing layer and the easy cracking of the base concrete.

[0005] In a first aspect, this application provides a microporous low-shrinkage concrete, wherein, by weight, the raw material proportions are: 300-380 parts cement, 30-70 parts fly ash, 250-350 parts medium sand, 1200-1550 parts gravel, 5-10 parts silica fume, 2-4 parts dihydrate gypsum, 0.5-2 parts water glass, 2-5 parts water-reducing agent, 0.1-0.3 parts retarder, 4-8 parts adhesive powder, 0.02-0.08 parts thickener, 2-6 parts water-absorbing fiber, and 110-150 parts water; the porosity of the microporous low-shrinkage concrete is 8-10%.

[0006] As a further improvement of this application, the particle size of the medium sand is 0~2.36mm and the fineness modulus is 2.7~2.9.

[0007] As a further improvement to this application, the grain size of the melon grains is 6~9mm.

[0008] As a further improvement to this application, the modulus of the water glass is 1 to 2.

[0009] As a further improvement of this application, the water-reducing agent is a polycarboxylate water-reducing agent with a solid content of 5-15%.

[0010] As a further improvement to this application, the retarder is one or more of sodium gluconate, sucrose, tartaric acid, and citric acid.

[0011] As a further improvement to this application, the adhesive powder is one or more of vinyl acetate-ethylene copolymer adhesive powder and acrylate adhesive powder.

[0012] As a further improvement of this application, the thickener is one or more of cellulose ether thickeners and polyacrylamide thickeners, with a viscosity of 100,000 to 200,000 Pa·s.

[0013] As a further improvement to this application, the absorbent fiber is one or more of polyacrylate fibers, polyurethane fibers, polyvinyl alcohol fibers, and cellulose ether fibers.

[0014] Secondly, this application provides a method for preparing microporous low-shrinkage concrete as described in the first aspect, comprising the following steps: S1. Cement, fly ash, medium sand, gravel, silica fume, and dihydrate gypsum are mixed and stirred to obtain the first mixture; S2. Add retarder, adhesive powder and thickener to the first mixture, and stir to obtain a second mixture; S3. Add water, water glass and water-reducing agent to the second mixture, and stir to form a uniform slurry; S4. Add water-absorbing fibers to the slurry and stir to obtain microporous low-shrinkage concrete.

[0015] The beneficial effects of this application are as follows: This application provides a microporous low-shrinkage concrete and its preparation method. The raw material proportions of the microporous low-shrinkage concrete, by weight, are: 300-380 parts cement, 30-70 parts fly ash, 250-350 parts medium sand, 1200-1550 parts gravel, 5-10 parts silica fume, 2-4 parts dihydrate gypsum, 0.5-2 parts water glass, 2-5 parts water-reducing agent, 0.1-0.3 parts retarder, 4-8 parts adhesive powder, 0.02-0.08 parts thickener, 2-6 parts water-absorbing fiber, and 110-150 parts water. The porosity of the microporous low-shrinkage concrete is 8-10%. The microporous low-shrinkage concrete provided in this application achieves a comprehensive improvement in waterproofing, crack resistance, construction performance, and economy through innovative material design and synergistic effects. Its unique microporous structure transforms water seepage from "blocking" to "dredging," achieving efficient and durable anti-seepage effects without the need for traditional waterproof membranes, and simplifying construction. At the same time, its high strength ensures the stability of the base layer and forms a strong bond with the surface layer, effectively preventing hollow cracking. In addition, the internal curing effect of water-absorbing fibers, combined with the expansion characteristics of dihydrate gypsum and water glass, eliminates the risk of cracking from the source, ensuring the long-term stability and safety of the flooring system.

[0016] This application achieves precise control of aggregate gradation, adjusting the porosity of concrete to 8-10%. This allows for effective release of osmotic pressure in the basement, preventing moisture from migrating upwards to the surface layer. Simultaneously, the microporous, low-shrinkage concrete exhibits greater surface roughness, resulting in stronger adhesion between it and the upper concrete layer compared to ordinary concrete. This significantly reduces the risk of voids between the surface and base concrete layers.

[0017] The microporous low-shrinkage concrete prepared in this application has a compressive strength of over 35 MPa. Even under heavy loads, it can ensure the structural stability of the base concrete while maintaining permeability.

[0018] This application achieves shrinkage reduction and strengthening effects by incorporating a composite of silica fume, gypsum dihydrate, and water glass. On the one hand, the incorporation of silica fume, under the alkaline conditions provided by gypsum and water glass, can significantly increase the compressive strength of concrete and the adhesion between the concrete and the surface concrete. On the other hand, the incorporation of gypsum dihydrate can generate a large amount of ettringite in the early stage, thereby significantly reducing the early shrinkage of concrete. At the same time, the incorporation of water glass can provide a high alkaline environment, thereby ensuring the stability of the early-formed ettringite and preventing shrinkage caused by the transformation of ettringite in the later stage of concrete hydration.

[0019] This application incorporates a certain amount of water-absorbing fibers, which can improve the toughness of microporous low-shrinkage concrete, thereby reducing its cracking risk. On the other hand, during the concrete hydration process, the free water inside the water-absorbing fibers plays an internal curing role, working together with the expansion agent to significantly reduce the shrinkage of the concrete. Furthermore, the water-absorbing fibers can also serve as a water-conducting channel for seepage in the base layer, thereby reducing the osmotic pressure of groundwater and achieving an anti-seepage effect.

[0020] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, the following are specific embodiments of this application. Detailed Implementation

[0021] The embodiments of the technical solution of this application are described in detail below. The following embodiments are only used to illustrate the technical solution of this application more clearly, and are therefore only examples, and should not be used to limit the scope of protection of this application.

[0022] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification and claims of this application are intended to cover non-exclusive inclusion.

[0023] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined.

[0024] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0025] In the description of the embodiments of this application, the term "multiple" refers to two or more (including two), similarly, "multiple sets" refers to two or more (including two sets), and "multiple pieces" refers to two or more (including two pieces).

[0026] In permeable underground spaces, permeable concrete is often used as the base layer. However, the low strength of permeable concrete can affect the overall stability of the concrete floor structure, especially in spaces with certain loads. Instability of the permeable base layer can lead to the destruction of the entire floor. Using dry-hard concrete for the base layer can result in excessively high density and excessively high osmotic pressure of groundwater. Once cracks appear, moisture will quickly rise along the cracks to the surface layer.

[0027] To address the technical problems in permeable underground spaces where existing permeable concrete has insufficient strength to bear loads, while dry-hard concrete has excessive density leading to osmotic pressure accumulation and rapid leakage once cracked, this application provides a microporous low-shrinkage concrete and its preparation method. By constructing a uniform closed microporous structure of 8-10% within the concrete, combined with the internal curing of water-absorbing fibers and the shrinkage compensation effect of expansion components, its strength can reach the standard of C35 concrete (28-day compressive strength not less than 35 MPa), ensuring the stability of the base concrete under load conditions. Furthermore, the low-shrinkage characteristics of the microporous low-shrinkage concrete significantly reduce the risk of cracking in the base concrete. Moreover, its internal microporous structure effectively channels the seepage water pressure in the basement, preventing its diffusion to the surface concrete under high osmotic pressure conditions.

[0028] In a first aspect, embodiments of this application provide a microporous low-shrinkage concrete, the raw material proportions by weight being: 300-380 parts cement, 30-70 parts fly ash, 250-350 parts medium sand, 1200-1550 parts gravel, 5-10 parts silica fume, 2-4 parts dihydrate gypsum, 0.5-2 parts water glass, 2-5 parts water-reducing agent, 0.1-0.3 parts retarder, 4-8 parts adhesive powder, 0.02-0.08 parts thickener, 2-6 parts water-absorbing fiber, and 110-150 parts water; the porosity of the microporous low-shrinkage concrete is 8-10%.

[0029] In the technical solution of this application embodiment, a uniform microporous network with a porosity precisely controlled at 8-10% is constructed in the cement matrix through the synergistic effect between raw materials. Because ordinary waterproof membranes have poor durability, once aging and damage occur, or the base concrete cracks, the overall anti-seepage effect of the floor will suffer irreparable damage. The microporous characteristics of microporous low-shrinkage concrete prevent water leakage from the bottom layer of basement areas at risk of seepage from penetrating to the floor surface, transforming basement seepage from blockage to drainage. This achieves good anti-seepage effects without the need for waterproof membranes or other waterproofing layers, making construction simpler, more efficient, and more durable. The compressive strength of microporous low-shrinkage concrete reaches C35 or higher, ensuring the stability of the base layer. Under certain load conditions, the entire floor system will not be damaged. Simultaneously, the microporous characteristics result in a strong bond between the surface concrete and the base microporous low-shrinkage concrete (reaching over 1.5 MPa), significantly reducing the risk of hollow cracking caused by the separation of the surface decorative concrete from the base concrete. Furthermore, the internal curing and crack-resistant properties of water-absorbing fibers, combined with the expansion properties of dihydrate gypsum and water glass, reduce the drying shrinkage of microporous low-shrinkage concrete to 0.01%, resulting in an extremely low risk of cracking. Preferably, the raw material ratio of microporous low-shrinkage concrete, by weight, is: 320-360 parts cement, 35-50 parts fly ash, 275-325 parts medium sand, 1300-1400 parts gravel, 5-10 parts silica fume, 2-4 parts dihydrate gypsum, 0.75-1.25 parts water glass, 3-4 parts water-reducing agent, 0.1-0.3 parts retarder, 4-8 parts adhesive powder, 0.02-0.08 parts thickener, 3-6 parts water-absorbing fibers, and 125-140 parts water, which can be adjusted according to construction requirements.

[0030] Furthermore, in some embodiments, the particle size of the medium sand is 0~2.36mm and the fineness modulus is 2.7~2.9.

[0031] In the technical solution of this application embodiment, by controlling the particle size of medium sand within a suitable range, the size of the aggregate is ensured to be moderate, which can effectively fill the gaps between larger aggregates (such as gravel). The fineness modulus is precisely set in the range of 2.7 to 2.9, which helps to obtain the optimal particle size distribution. This optimized distribution enables the sand and stone aggregates to form the densest packing skeleton, thereby maximizing the density and strength of concrete with the same amount of cement, while reducing the filling requirement of cement paste.

[0032] Furthermore, in some embodiments, the particle size of the pebbles is 6-9 mm.

[0033] In the technical solution of this application embodiment, in the aggregate gradation system of concrete, gravel of suitable particle size and medium sand form a denser and more stable packing structure. This optimized gradation not only significantly improves the density and overall strength of concrete, providing a solid foundation for strengths above C35, but also the uniformly distributed fine aggregate provides an ideal physical framework for the uniform formation of microporous structures, ensuring that microporous low-shrinkage concrete achieves high load-bearing capacity while also possessing excellent impermeability.

[0034] Furthermore, in some embodiments, the modulus of the water glass is 1 to 2.

[0035] In the technical solution of this application embodiment, the low-modulus water glass indicates a low silica to sodium oxide ratio, which helps it to rapidly hydrolyze in an alkaline environment, generating highly reactive silicate ions. These active silicate ions can react rapidly with calcium hydroxide produced during cement hydration to generate stable hydrated calcium silicate gel (CSH gel), significantly promoting the early setting and hardening of concrete and improving early strength. At the same time, the newly generated gel can effectively fill and refine capillary pores, providing key support for constructing a uniform closed microporous structure of 8-10%.

[0036] Furthermore, in some embodiments, the water-reducing agent is a polycarboxylate water-reducing agent with a solid content of 5-15%.

[0037] In the technical solution of this application embodiment, a polycarboxylate-based high-performance water-reducing agent is selected. Utilizing its unique steric hindrance effect, it can efficiently disperse cement particles with extremely low dosage, releasing a large amount of encapsulated mixing water, thereby achieving excellent fluidity at a low water-cement ratio. Controlling the solid content within a suitable range ensures both the concentration of the effectively dispersed components and avoids problems such as excessive viscosity and uneven dispersion caused by excessive solid content.

[0038] Furthermore, in some embodiments, the retarder is one or more of sodium gluconate, sucrose, tartaric acid, and citric acid.

[0039] In the technical solution of this application embodiment, organic retarder molecules can be adsorbed onto the surface of cement particles to form an inhibitory film, effectively slowing down the initial hydration rate of cement, thereby extending the setting time of concrete. This regulatory effect provides a crucial time window for the formation and stabilization of the microporous structure, ensuring that the microporous reaction initiated by components such as water glass can proceed fully and uniformly before the initial setting of concrete; at the same time, it also optimizes the workability of concrete, facilitates construction operations, and helps reduce temperature stress caused by the concentrated release of hydration heat, further enhancing the crack resistance and volume stability of concrete.

[0040] Furthermore, in some embodiments, the adhesive powder is one or more of vinyl acetate-ethylene copolymer (VAE) adhesive powder and acrylate adhesive powder.

[0041] In the technical solution of this application embodiment, the polymer powder can redisperse into a flexible polymer emulsion upon contact with water, uniformly distributed within the cement matrix. As cement hydration progresses, these polymer particles cross-link and bond with hydration products (such as CSH gel), forming a dense and elastic polymer network within the cement paste. This network not only fills and bridges microcracks, significantly improving the toughness, impact resistance, and fatigue resistance of concrete, but also enhances adhesion to surface materials, effectively preventing hollow areas and cracking. Simultaneously, this flexible network absorbs and disperses shrinkage stress, working synergistically with water-absorbing fibers and expansion components to ensure low cracking risk and high durability of the microporous, low-shrinkage concrete.

[0042] Furthermore, in some embodiments, the thickener is one or more of cellulose ether thickeners and polyacrylamide thickeners, with a viscosity of 100,000 to 200,000 Pa·s.

[0043] In the technical solution of this application embodiment, high-viscosity cellulose ethers or polyacrylamides are selected. Their long-chain molecular structures form a three-dimensional network in water, which can significantly improve the viscosity of the mixture. This high-viscosity state can effectively inhibit the segregation and bleeding of heavy aggregates (such as gravel) and light components (such as adhesive powder and fibers), ensuring that all components are uniformly suspended, providing a stable slurry environment for the formation of a uniform microporous structure of 8-10%. At the same time, the appropriate viscosity can encapsulate the mixing water, reduce the evaporation of free water, thereby further reducing drying shrinkage and optimizing the overall rheological properties of concrete, ensuring the uniformity and stability of the internal structure while meeting construction requirements. Specifically, the cellulose ether thickener can be one or more of hydroxypropyl methylcellulose ether (HPMC), methylcellulose ether (MC), and hydroxyethyl methylcellulose ether (HEMC); the polyacrylamide thickener can be one or more of anionic polyacrylamide, cationic polyacrylamide, and nonionic polyacrylamide.

[0044] Furthermore, in some embodiments, the absorbent fiber is one or more of polyacrylate fibers, polyurethane fibers, polyvinyl alcohol fibers, and cellulose ether fibers.

[0045] In the technical solution of this application embodiment, the unique molecular structure or physical morphology of the superabsorbent polymer gives it a strong water absorption and retention capacity. During the mixing process, it absorbs the mixing water, forming an internal curing water source, which is slowly released in the later stages of cement hydration. This effectively compensates for shrinkage caused by water evaporation and self-drying, thereby significantly reducing the risk of cracking. Simultaneously, these randomly distributed fibers form a dense network structure in the matrix, inhibiting the initiation and propagation of microcracks through bridging, significantly improving the toughness and impact resistance of concrete. Specifically, the superabsorbent fiber material can be selected from, but is not limited to, cellulose derivatives such as polyacrylates (e.g., sodium polyacrylate), polyurethane, polyvinyl alcohol (PVA), and carboxymethyl cellulose (CMC).

[0046] Secondly, embodiments of this application provide a method for preparing microporous low-shrinkage concrete, comprising the following steps: S1. Cement, fly ash, medium sand, gravel, silica fume, and dihydrate gypsum are mixed and stirred to obtain the first mixture; S2. Add retarder, adhesive powder and thickener to the first mixture, and stir to obtain the second mixture; S3. Add water, water glass and water-reducing agent to the second mixture, and stir to form a uniform slurry; S4. Add water-absorbing fibers to the slurry and stir to obtain microporous low-shrinkage concrete.

[0047] Because ordinary microporous concrete has a high porosity and low water consumption, the cementitious materials are difficult to disperse completely during mixing, resulting in poor paste density and low strength. The mixing method described in this application, by adding excess water in the early stage, allows for thorough dispersion of the cementitious materials. Then, water-absorbing fibers are added to absorb the excess water, reducing the actual water-cement ratio of the paste and improving the uniformity of cementitious material particle dispersion. This significantly improves the overall strength of the resulting microporous low-shrinkage concrete.

[0048] The following are some specific embodiments. It should be noted that the embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they shall be performed in accordance with the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained commercially.

[0049] Example 1 This embodiment provides a microporous low-shrinkage concrete, whose raw material proportions by weight are: 340 parts cement (P·O42.5 cement), 40 parts fly ash, 300 parts medium sand, 1350 parts gravel, 8 parts silica fume, 3 parts dihydrate gypsum, 1 part water glass, 3.5 parts polycarboxylate superplasticizer (solid content 10%), 0.2 parts sodium gluconate retarder, 6 parts VAE adhesive powder, 0.05 parts hydroxypropyl methylcellulose ether thickener, 4 parts polyurethane water-absorbing fiber, and 130 parts water; its preparation method includes the following steps: S1. Add cement, fly ash, medium sand, gravel, silica fume and dihydrate gypsum into a mixer and mix at 30 rpm for 1 min to obtain the first mixture; S2. Add retarder, adhesive powder and thickener to the first mixture and continue stirring for 1 minute to obtain the second mixture; S3. Add water, water glass and water-reducing agent to the second mixture, and stir at 60 rpm to form a uniform slurry; S4. Add polyurethane water-absorbing fibers to the slurry, and stir rapidly at 120 rpm for 3 minutes. The water-absorbing fibers will absorb the excess water to obtain microporous low-shrinkage concrete suitable for paving construction.

[0050] The microporous low-shrinkage concrete produced according to this formula has a porosity of 8.8%, a 28-day compressive strength of 37.2 MPa, a flexural strength of 5.3 MPa, a 28-day drying shrinkage rate of 0.01%, and a bond strength of 1.62 MPa with ordinary C30 concrete.

[0051] Example 2 This embodiment provides a microporous low-shrinkage concrete. Compared with Embodiment 1, the only difference is the raw material ratio by weight, which is as follows: 340 parts cement, 40 parts fly ash, 300 parts medium sand, 1350 parts gravel, 8 parts silica fume, 2 parts dihydrate gypsum, 0.5 parts water glass, 2 parts polycarboxylate superplasticizer (solid content of 10%), 0.1 parts sodium gluconate retarder, 4 parts VAE adhesive powder, 0.02 parts hydroxypropyl methylcellulose ether thickener, 2 parts polyurethane fiber, and 110 parts water. Other experimental parameters and conditions are basically the same as those in Embodiment 1, and will not be repeated here.

[0052] Example 3 This embodiment provides a microporous low-shrinkage concrete. Compared with Embodiment 1, the only difference is the raw material ratio by weight, which is as follows: 340 parts cement, 40 parts fly ash, 300 parts medium sand, 1350 parts gravel, 8 parts silica fume, 4 parts dihydrate gypsum, 2 parts water glass, 5 parts polycarboxylate superplasticizer (solid content of 10%), 0.3 parts sodium gluconate retarder, 8 parts VAE adhesive powder, 0.08 parts hydroxypropyl methylcellulose ether thickener, 6 parts polyurethane fiber, and 150 parts water. Other experimental parameters and conditions are basically the same as those in Embodiment 1, and will not be repeated here.

[0053] Example 4 This embodiment provides a microporous low-shrinkage concrete. Compared with Embodiment 1, the only difference is that the proportions of cement, fly ash, and silica fume in each raw material are different by weight. Specifically, the proportions of cement, fly ash, and silica fume are changed to: 300 parts cement, 70 parts fly ash, and 10 parts silica fume. Other experimental parameters and conditions are basically the same as in Embodiment 1, and will not be repeated here.

[0054] Example 5 This embodiment provides a microporous low-shrinkage concrete. The only difference from Embodiment 1 is that the proportions of cement, fly ash, and silica fume in each raw material are different by weight. Specifically, the proportions of cement, fly ash, and silica fume are changed to: 320 parts cement, 50 parts fly ash, and 10 parts silica fume. Other experimental parameters and conditions are basically the same as in Embodiment 1 and will not be repeated here.

[0055] Example 6 This embodiment provides a microporous low-shrinkage concrete. Compared with Embodiment 1, the only difference is that the proportions of cement, fly ash, and silica fume in each raw material are different by weight. Specifically, the proportions of cement, fly ash, and silica fume are changed to: 360 parts cement, 35 parts fly ash, and 8 parts silica fume. Other experimental parameters and conditions are basically the same as in Embodiment 1, and will not be repeated here.

[0056] Example 7 This embodiment provides a microporous low-shrinkage concrete. Compared with Embodiment 1, the only difference is that the proportions of cement, fly ash, and silica fume in each raw material are different by weight. Specifically, the proportions of cement, fly ash, and silica fume are changed to: 380 parts cement, 30 parts fly ash, and 5 parts silica fume. Other experimental parameters and conditions are basically the same as in Embodiment 1, and will not be repeated here.

[0057] Example 8 This embodiment provides a microporous low-shrinkage concrete. Compared with Embodiment 1, the only difference is that the proportion of medium sand and gravel in each raw material is different by weight. Specifically, the ratio of medium sand to gravel is changed to 250 parts medium sand and 1550 parts gravel. Other experimental parameters and conditions are basically the same as those in Embodiment 1, and will not be repeated here.

[0058] Example 9 This embodiment provides a microporous low-shrinkage concrete. Compared with Embodiment 1, the only difference is that the proportion of medium sand and gravel in each raw material is different by weight. Specifically, the ratio of medium sand to gravel is changed to 275 parts medium sand and 1400 parts gravel. Other experimental parameters and conditions are basically the same as those in Embodiment 1, and will not be repeated here.

[0059] Example 10 This embodiment provides a microporous low-shrinkage concrete. Compared with Embodiment 1, the only difference is that the proportion of medium sand and gravel in each raw material is different by weight. Specifically, the ratio of medium sand to gravel is changed to 325 parts medium sand and 1300 parts gravel. Other experimental parameters and conditions are basically the same as those in Embodiment 1, and will not be repeated here.

[0060] Example 11 This embodiment provides a microporous low-shrinkage concrete. Compared with Embodiment 1, the only difference is that the proportion of medium sand and gravel in each raw material is different by weight. Specifically, the ratio of medium sand to gravel is changed to 350 parts medium sand and 1200 parts gravel. Other experimental parameters and conditions are basically the same as those in Embodiment 1, and will not be repeated here.

[0061] Comparative Example 1 Comparative Example 1 provides a microporous low-shrinkage concrete. The only difference from Example 1 is that the cement content is 400 parts. Other experimental parameters and conditions are basically the same as those in Example 1, and will not be repeated here.

[0062] Comparative Example 2 Comparative Example 2 provides a microporous low-shrinkage concrete. The only difference from Example 1 is that the silica fume content is 15 parts. Other experimental parameters and conditions are basically the same as those in Example 1, and will not be repeated here.

[0063] Comparative Example 3 Comparative Example 3 provides a microporous low-shrinkage concrete. The only difference from Example 1 is that the medium sand is 400 parts and the gravel is 1150 parts. Other experimental parameters and conditions are basically the same as those in Example 1, and will not be repeated here.

[0064] Comparative Example 4 Comparative Example 4 provides a microporous low-shrinkage concrete. The only difference from Example 1 is that no dihydrate gypsum was added. Other experimental parameters and conditions are basically the same as those in Example 1, and will not be repeated here.

[0065] Comparative Example 5 Comparative Example 5 provides a microporous low-shrinkage concrete. The only difference from Example 1 is that no water-absorbing fibers were added. Other experimental parameters and conditions are basically the same as those in Example 1, and will not be repeated here.

[0066] Comparative Example 6 Comparative Example 6 is ordinary C35 concrete. By weight, its raw material ratio is: 250 parts cement, 65 parts mineral powder, 35 parts fly ash, 900 parts medium sand, 950 parts crushed stone, 4.5 parts water-reducing agent, and 165 parts water.

[0067] The concrete provided in the examples and comparative examples was subjected to performance tests, and the results are shown in Table 1.

[0068] Table 1. Test results of the examples and comparative examples. As shown in Table 1, in Comparative Example 1, increasing the cement content increases the compressive and flexural strength of the concrete, but also increases the shrinkage rate. In Comparative Example 2, increasing the silica fume ratio significantly increases the compressive and flexural strength, as well as the bond strength, while slightly increasing the shrinkage rate. In Comparative Example 3, increasing the sand ratio and decreasing the gravel ratio results in lower concrete porosity, indicating that the ratio of medium sand to gravel affects the permeability of the concrete. In Comparative Example 4, the lack of dihydrate gypsum leads to a significant increase in shrinkage, slower early strength development, and decreased bond strength. In Comparative Example 5, the absence of absorbent fibers significantly increases shrinkage and drastically reduces compressive and flexural strength, demonstrating that absorbent fibers are crucial for achieving ultra-low shrinkage and internal curing enhancement.

[0069] The microporous low-shrinkage concrete provided in this application is an innovative material specifically designed for high-quality floor substrates, especially in harsh environments such as water-permeable basements. Through precise control, it forms a porosity of 8-10%, which not only actively guides moisture from the underlying substrate and mitigates minor defects but also endows the substrate with exceptional durability. Simultaneously, it incorporates a composite anti-shrinkage technology combining an expansion agent and water-absorbing fibers, compressing the shrinkage rate to a minimum of 0.01%, fundamentally eliminating the risk of cracking. This dual-core mechanism of guidance and internal conditioning makes it a flooring foundation with high stability, crack resistance, and long-lasting waterproofing, ensuring the durability and aesthetics of the surface finish.

[0070] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A microporous low-shrinkage concrete, characterized in that, The raw material proportions by weight are as follows: cement 300-380 parts, fly ash 30-70 parts, medium sand 250-350 parts, gravel 1200-1550 parts, silica fume 5-10 parts, gypsum dihydrate 2-4 parts, water glass 0.5-2 parts, water-reducing agent 2-5 parts, retarder 0.1-0.3 parts, adhesive powder 4-8 parts, thickener 0.02-0.08 parts, water-absorbing fiber 2-6 parts, and water 110-150 parts. The porosity of the microporous low-shrinkage concrete is 8-10%.

2. The microporous low-shrinkage concrete according to claim 1, characterized in that, The medium sand has a particle size of 0~2.36mm and a fineness modulus of 2.7~2.

9.

3. The microporous low-shrinkage concrete according to claim 1, characterized in that, The particle size of the melon grains is 6~9mm.

4. The microporous low-shrinkage concrete according to claim 1, characterized in that, The modulus of the water glass is 1 to 2.

5. The microporous low-shrinkage concrete according to claim 1, characterized in that, The water-reducing agent is a polycarboxylate water-reducing agent with a solid content of 5-15%.

6. The microporous low-shrinkage concrete according to claim 1, characterized in that, The retarder is one or more of sodium gluconate, sucrose, tartaric acid, and citric acid.

7. The microporous low-shrinkage concrete according to claim 1, characterized in that, The adhesive powder is one or more of vinyl acetate-ethylene copolymer adhesive powder and acrylate adhesive powder.

8. The microporous low-shrinkage concrete according to claim 1, characterized in that, The thickener is one or more of cellulose ether thickeners and polyacrylamide thickeners, with a viscosity of 100,000 to 200,000 Pa·s.

9. The microporous low-shrinkage concrete according to claim 1, characterized in that, The absorbent fiber is one or more of the following: polyacrylate fiber, polyurethane fiber, polyvinyl alcohol fiber, and cellulose ether fiber.

10. A method for preparing microporous low-shrinkage concrete as described in any one of claims 1-9, characterized in that, Includes the following steps: S1. Cement, fly ash, medium sand, gravel, silica fume, and dihydrate gypsum are mixed and stirred to obtain the first mixture; S2. Add retarder, adhesive powder and thickener to the first mixture, and stir to obtain a second mixture; S3. Add water, water glass and water-reducing agent to the second mixture, and stir to form a uniform slurry; S4. Add water-absorbing fibers to the slurry and stir to obtain microporous low-shrinkage concrete.

Images