Cement-based interface enhancer for brick-concrete recycled aggregate and preparation method thereof

Abstract

The present invention discloses a cement-based interface enhancer for brick-concrete recycled aggregate and a preparation method thereof. The interface enhancer comprises the following substances: 22-26wt% of fast-hardening Portland cement, 60-64wt% of quartz sand, 3-4wt% of silica fume, 0.2-0.3wt% of water reducer, 0.2-0.3wt% of hardener, 0.05-0.1wt% of accelerator, 0.05-0.1wt% of hydroxypropyl methylcellulose, 0.3-0.5wt% of silane, 0.1-0.2wt% of shrinkage reducer, 0.05-0.1wt% of polypropylene fiber, and 8-10wt% of water. The preparation method comprises the following steps: placing the fast-hardening Portland cement and silica fume in a blender and stirring; sequentially adding the water reducer, hardener, accelerator, hydroxypropyl methylcellulose, shrinkage reducer, and silane into water and stirring to form a solution; and dividing the solution into three parts, adding each part into a blender together with quartz sand of different particle sizes and polypropylene fibers of different lengths and stirring to fully mix the substances. The interface enhancer of the present invention can improve the interface bonding strength between old binder and old aggregate particles in brick-concrete recycled aggregate, thereby fundamentally improving the performance of the brick-concrete recycled aggregate.

Description

Technical Field

[0001] The invention belongs to the technical field of road engineering materials, and particularly relates to a cement-based interface enhancer for brick-concrete recycled aggregate and a preparation method thereof. Background Art

[0002] In recent years, with the rapid development of infrastructure and urbanization, the generation of large amounts of construction waste has led to a sharp increase in demand for recycled aggregate resources. Construction waste is generally divided into concrete and brick-concrete waste. Processing of these two types of waste yields recycled concrete aggregate and brick-concrete aggregate, respectively. Recycled concrete aggregate is derived from waste concrete, while recycled brick-concrete aggregate is derived from waste bricks and tiles. Concrete and bricks and tiles (i.e., red bricks, red brick fragments, tiles, etc.) are two different types of solid waste. Concrete waste has a higher content of concrete and a very low (almost zero) content of bricks and tiles. Its chemical composition is primarily CaO and CaCO₃, which are alkaline substances. Its surface morphology is relatively regular, and its internal pores are relatively few and small. Brick-concrete waste, on the other hand, has a higher content of bricks and tiles and a very low (almost zero) content of concrete. Its chemical composition is primarily SiO₂, which is acidic. Its surface morphology is more irregular, and its internal pores are numerous and large.

[0003] In the prior art, unless specifically mentioned as high-quality brick-concrete, bricks and tiles, or red brick fragments, the selected construction waste is concrete-based. Brick-concrete construction waste primarily results from the demolition of existing brick-concrete structures. This type of construction waste, containing a large amount of brick and tile materials, suffers from disadvantages such as high water absorption, low strength, and unstable performance.

[0004] Compared to natural aggregates and recycled aggregates used in concrete, recycled aggregates used in brick-concrete mixes contain a large number of brick and tile particles, resulting in high surface porosity, high water absorption, and low strength. This severely restricts their application and promotion in road construction materials (such as cement concrete, asphalt mixtures, and mortars). Research shows that the water absorption rate of recycled aggregates used in brick-concrete mixes can reach 10-25%, compared to only 1-5% for natural aggregates and 3-8% for recycled aggregates used in concrete. This high water absorption rate can lead to the need for additional water during mixing or bleeding, which can affect slump and road construction quality.

[0005] In addition, in brick-concrete recycled aggregates, the microstructure of the interface transition zone (ITZ) between the old binder and the old aggregate particles is loose, and cracks can easily expand here, which significantly reduces the compressive strength and impermeability of brick-concrete recycled aggregates. In order to improve this weak interface, a variety of surface treatment methods have been proposed in academia and engineering practice, including mechanical friction, acid leaching, heat treatment and chemical coating. However, these methods have limitations: (1) Mechanical friction can remove some old binders, but it increases energy consumption and cost, and it is difficult to eliminate fine residues attached to the deep pores; (2) Acid leaching can deeply peel off the bonding mortar, but it has an adverse effect on the chemical stability of the recycled aggregate and produces acidic waste liquid, which requires subsequent treatment and is not environmentally friendly; (3) Heat treatment can volatilize some organic impurities and improve the strength of the recycled aggregate through high-temperature roasting, but it consumes a lot of power, has a complex process, and is prone to secondary cracks, making it unsuitable for large-scale field applications; (4) Chemical coating methods such as silane, siloxane or nano-silica slurry coatings can form a hydrophobic film on the surface to improve the anti-seepage effect, but the coating thickness is difficult to control uniformly and the early strength growth is limited.

[0006] Traditional cement-based reinforcement materials, such as pure cement slurry, are unable to simultaneously improve the early strength of recycled aggregates in brick-concrete structures and inhibit cracks. Plastic shrinkage cracks are prone to occur, and the improvement in crack resistance toughness is limited. Rapid-hardening cement mortar has mature applications in bridge repair and prefabricated parts industries, but it is mainly targeted at natural aggregate systems and has poor adaptability to recycled aggregates in brick-concrete structures with high water absorption and weak interfaces.

[0007] Existing research, both domestically and internationally, has focused on the early-stage strength and crack resistance of fast-setting cement mortars, but systematic research on how to effectively coat and enhance the interfacial bonding of recycled aggregate surfaces is lacking. Furthermore, most fast-setting systems fail to balance waterproofing and water retention, making it difficult to address the issues of construction bleeding and subsequent shrinkage cracking caused by the high water absorption of recycled aggregates. Admixtures such as water-reducing agents, water-retaining agents, and waterproofing agents exhibit excellent dispersion, water-retention, and anti-seepage properties in conventional mortars, but research on the synergistic effects of these admixtures in fast-drying and fast-hardening systems is limited. Fibers and other fiber-reinforced materials have been shown to effectively bridge cracks and enhance the toughness of recycled aggregates, but their compatibility with fast-drying and fast-hardening mortars and optimization of the interfacial properties of recycled aggregates remain technical bottlenecks. Therefore, developing a cement-based interfacial enhancer that combines fast drying and hardening, high early strength, excellent water retention, anti-seepage, and crack resistance, while also forming a dense, reinforced coating on the surface of recycled aggregates in brick-concrete applications, is of great practical significance and application value.

[0008] The invention patent with application publication number CN118684473A discloses a recycled concrete aggregate interface enhancer and a preparation method thereof, which includes the following components by mass: 5-10 parts of water, 10-20 parts of cement, 5-10 parts of sodium silicate, 5-10 parts of calcium carbonate, 5-10 parts of silicon dioxide, 1-3 parts of defoaming agent, and 1-3 parts of water reducer. The recycled concrete aggregate interface enhancer is prepared by mixing the components. This technical solution has the following technical defects: (1) The prepared interface enhancer is only applicable to concrete-type recycled aggregates, but not to brick-concrete-type recycled aggregates; (2) The prepared interface enhancer only improves the adhesion between the new and old slurry interfaces of recycled concrete aggregates, but cannot improve the bonding between the old slurry interfaces and aggregate particles, so it cannot fundamentally improve the performance of the recycled aggregate itself; (3) The prepared interface enhancer improves the mechanical properties, impermeability, etc. of recycled concrete (i.e., a mixture of recycled aggregates and other materials), but cannot improve the performance of the recycled aggregate; (4) Compared with brick-concrete-type recycled aggregates, the water absorption rate of concrete-type recycled aggregates is lower, so this technical solution does not mention any technical features related to improving the water absorption rate of recycled aggregates. Summary of the Invention

[0009] In order to solve the problems existing in the prior art, the present invention provides a cement-based interface enhancer for brick-concrete recycled aggregate, wherein the interface enhancer is used to wrap the outer surface of the brick-concrete recycled aggregate, and the brick-concrete content of the brick-concrete recycled aggregate is not less than 10wt%; the addition amount of each substance in the interface enhancer accounts for the following mass percentages of the interface enhancer: fast-hardening silicate cement 22-26wt%, quartz sand 60-64wt%, silica fume 3-4wt%, water reducer 0.2-0.3wt%, hardener 0.2-0.3wt%, accelerator 0.05-0.1wt%, hydroxypropyl methylcellulose 0.05-0.1wt%, silane 0.3-0.5wt%, shrinkage reducer 0.1-0.2wt%, polypropylene fiber 0.05-0.1wt%, water 8-10wt%, and the sum of the contents of each substance is 100wt%, wherein the ratio of the mass of the water to the sum of the mass of the fast-hardening silicate cement and the silica fume is controlled within the range of 0.2-0.4.

[0010] Preferably, the model of the rapid hardening Portland cement is 42.5R; the specific surface area of ​​the silica fume is 300-350m 2 / kg.

[0011] In any of the above schemes, it is preferred that the quartz sand includes three particle sizes, namely 150-300 μm, 90-150 μm, and 75-90 μm; the mass percentage of each particle size in the quartz sand is: particle size 150-300 μm accounts for 18-25wt%, particle size 90-150 μm accounts for 47-52wt%, and particle size 75-90 μm accounts for 25-33wt%.

[0012] In any of the above solutions, preferably, the water reducer is a polycarboxylate water reducer with a solid content of 30%.

[0013] In any of the above schemes, it is preferred that the hardener consists of calcium formate and calcium acetate, and the mass percentages of the two substances in the hardener are 35-45wt% of calcium formate and 55-65wt% of calcium acetate, respectively.

[0014] In any of the above schemes, it is preferred that the accelerating setting agent is composed of calcium sulfate and aluminum sulfate, and the mass percentages of the two substances in the accelerating setting agent are 45-55wt% of calcium sulfate and 45-55wt% of aluminum sulfate, respectively.

[0015] In any of the above solutions, preferably, the shrinkage reducing agent is Sika Control-75 shrinkage reducing agent, the chemical components of which are mainly hydroxyl compounds.

[0016] In any of the above schemes, it is preferred that the polypropylene fiber includes three lengths, namely 1-3mm, 3-6mm, and 6-9mm; the mass percentage of each length in the polypropylene fiber is 20-24wt% for the length 1-3mm, 42-50wt% for the length 3-6mm, and 28-35wt% for the length 6-9mm; the diameter of the polypropylene fiber with a length of 1-3mm is 18-28μm, and the diameters of the polypropylene fibers with a length of 3-6mm and a length of 6-9mm are both 28-38μm.

[0017] The present invention also provides a method for preparing a cement-based interface enhancer for brick-concrete recycled aggregate, which is used to prepare any of the above-mentioned cement-based interface enhancers for brick-concrete recycled aggregates, and comprises the following steps in order:

[0018] Step 1: Weigh each material according to the designed material ratio;

[0019] Step 2: Mix calcium formate and calcium acetate evenly according to the designed material ratio to obtain a hardener for standby use; mix calcium sulfate and aluminum sulfate evenly according to the designed material ratio to obtain an accelerator for standby use;

[0020] Step 3: Put all the rapid hardening Portland cement and silica fume into a mixer and stir them to mix the two substances evenly to obtain dry material;

[0021] Step 4: Add the water reducer, hardener, accelerator, hydroxypropyl methylcellulose, shrinkage reducer and silane to the water in sequence and stir until all six substances are dissolved in the water to form a solution;

[0022] Step 5: Add part of the solution into the blender and mix it with the dry ingredients;

[0023] Step 6: Add quartz sand with a particle size of 75-90 μm and polypropylene fiber with a length of 1-3 mm into the blender and continue stirring to mix the materials;

[0024] Step 7: Add part of the solution, quartz sand with a particle size of 90-150 μm, and polypropylene fiber with a length of 3-6 mm into a blender and continue stirring to mix the substances;

[0025] Step 8: Add the remaining solution, quartz sand with a particle size of 150-300 μm, and polypropylene fiber with a length of 6-9 mm into the blender and continue stirring to mix the substances;

[0026] Step 9: Increase the stirring speed and continue stirring to fully mix the substances to obtain a cement-based interface enhancer for brick-concrete recycled aggregate.

[0027] Preferably, in step 3, the rapid hardening Portland cement and silica fume are all put into a mixer and stirred at room temperature, a stirring speed of 140-200 r / min, and a stirring time of 1-2 min.

[0028] In any of the above schemes, preferably, in step 4, the water reducer, hardener, accelerator, hydroxypropyl methylcellulose, shrinkage reducing agent and silane are sequentially added to water and stirred, the stirring method is manual mixing, and the stirring temperature is room temperature; the mixing time after adding the water reducer is 1-2 min, the mixing time after adding the hardener is 2-3 min, the mixing time after adding the accelerator is 2-3 min, the mixing time after adding the hydroxypropyl methylcellulose is 2-3 min, the mixing time after adding the shrinkage reducing agent is 2-3 min, and the mixing time after adding the silane is 1-2 min.

[0029] In any of the above schemes, preferably, in step five, the amount of solution added is 25-35wt% of the total solution, the stirring temperature is room temperature, the stirring speed is 140-200 r / min, and the stirring time is 1-2 min.

[0030] In any of the above schemes, preferably, in step six, quartz sand with a particle size of 75-90 μm and polypropylene fiber with a length of 1-3 mm are added to the mixer and continued stirring at room temperature, a stirring speed of 140-200 r / min, and a stirring time of 1-2 min.

[0031] In any of the above schemes, preferably, in step seven, part of the solution, quartz sand with a particle size of 90-150 μm, and polypropylene fiber with a length of 3-6 mm are added to the mixer and continued stirring, the amount of solution added is 35-45 wt% of the total solution, the stirring temperature is room temperature, the stirring speed is 140-200 r / min, and the stirring time is 2-3 min.

[0032] In any of the above schemes, preferably, in step eight, the remaining solution, quartz sand with a particle size of 150-300 μm, and polypropylene fiber with a length of 6-9 mm are added to the mixer and continued stirring, the amount of solution added is 25-35 wt% of the total solution, the stirring temperature is room temperature, the stirring speed is 140-200 r / min, and the stirring time is 2-3 min.

[0033] In any of the above solutions, preferably, in step nine, the stirring speed is increased to 280-350 r / min, and the stirring time is 3-5 min.

[0034] Among any of the above schemes, it is preferred that an interface enhancer is used to carry out surface coating and strengthening of brick-concrete recycled aggregates, and the method is: the brick-concrete recycled aggregates are placed in a granulator containing an interface enhancer for rotational coating, the initial mass of the brick-concrete recycled aggregates and the mass ratio of the corresponding interface enhancer is 3:1.5-2, the rotational coating temperature is room temperature, the rotational coating speed is 150-180r / min, and the rotational coating time is 3-5min. After rotational coating, the outer surface of the brick-concrete recycled aggregates is coated with a layer of slurry thin shell, and the thickness of the slurry thin shell is 1-2mm; after the rotational coating is completed, the brick-concrete recycled aggregates coated with the slurry thin shell are spread out and naturally cured for 1-1.5h, and then transferred to a closed moisturizing box for further curing, the curing temperature is 20±2℃, the curing humidity is 60±5%, and the curing time is 20-24h, thus completing the surface coating and strengthening of the brick-concrete recycled aggregates by the interface enhancer. After curing, brick-concrete recycled aggregates can be immediately used in the preparation of road engineering materials such as cement concrete, asphalt mixture or mortar.

[0035] In the present invention, quartz sand has three particle sizes: 150-300μm, 90-150μm, and 75-90μm, i.e., 150μm ≤ particle size < 300μm, 90μm ≤ particle size < 150μm, and 75μm ≤ particle size < 90μm. For each particle size range, the material, after sequentially passing through the upper and lower sieves, has a particle size between the upper and lower sieves. For example, the particle size range of 90-150μm (90μm ≤ particle size < 150μm) is 90-150μm, i.e., the material, after sequentially passing through a 150μm sieve and a 90μm sieve, has a particle size between 150μm and 150μm.

[0036] Polypropylene fibers come in three lengths: 6-9mm, 3-6mm, and 1-3mm, meaning 6mm ≤ length ≤ 9mm, 3mm ≤ length < 6mm, and 1mm ≤ length < 3mm. Polypropylene fibers with a length of 1-3mm have a diameter of 18-28μm, meaning 18μm ≤ diameter < 28μm, and any diameter within this range is acceptable. Polypropylene fibers with a length of 3-6mm and 6-9mm have a diameter of 28-38μm, meaning 28μm ≤ diameter ≤ 38μm, and any diameter within this range is acceptable.

[0037] The interface enhancer of this invention utilizes the synergistic effect of rapid-hardening Portland cement and multiple components to enhance the interfacial bond strength (i.e., the interfacial bond strength between the old binder and the old aggregate particles) and overall performance of recycled aggregate for brick-concrete applications. Rapid-hardening Portland cement (42.5R) serves as the core cementitious material, combined with the micro-filling effect of high-surface-area silica fume, rapidly forms a dense calcium silicate hydrate gel, laying the foundation for the early strength of recycled aggregate for brick-concrete applications. Quartz sand of three particle sizes (75-300μm) is added layer by layer to optimize grading, with coarse sand forming the skeleton and medium and fine sand filling the pores. Multi-scale polypropylene fibers are then added to bridge cracks in stages, forming a multi-stage reinforcement system characterized by "micro-filling, nano-reinforcement, and macro-crack resistance." Furthermore, the calcium salt hardener releases Ca²⁺ to accelerate cement hydration and shorten setting time, while the gypsum-based accelerator achieves initial setting within 10 minutes through rapid nucleation of ettringite. The synergistic effect of these two components addresses the construction delays often associated with high water absorption of recycled aggregate for brick-concrete applications. At the same time, the polycarboxylate superplasticizer reduces the water-binder ratio and improves density. The hydrophobic film formed by the silane inhibits secondary water absorption. Hydroxypropyl methylcellulose and the shrinkage reducer balance water retention and crack resistance, ultimately forming a dense 1-2mm coating on the surface of the recycled aggregate for brick-concrete applications. This coating reconstructs the transition zone between the old binder and the old aggregate through physical pore filling, chemical bonding interfaces, and fiber crack resistance, significantly improving interfacial bonding strength. The recycled aggregate's compressive strength, impermeability, and frost resistance reach the level of natural aggregate, allowing it to be used directly in road construction materials without pre-drying.

[0038] In the present invention, the addition amount of polypropylene fiber is controlled within the range of 0.05-0.1wt%. Although the addition amount of polypropylene fiber seems to be relatively small, its mass is relatively light and its volume share is relatively large. Similar to cotton, after it is placed in other substances and stirred, it actually occupies a relatively large volume. In actual experiments, adding 0.05-0.1wt% of polypropylene fiber is sufficient.

[0039] In the process of preparing the interface enhancer of the present invention, the selection of each substance, the addition amount of each substance, the addition order of each substance, the process parameters of each step, etc. are all very important. In particular, the layer-by-layer progressive addition method of three types of quartz sand with different particle sizes and three types of polypropylene fibers with different lengths plays a key role. The timing of adding the three types of quartz sand with different particle sizes and three types of polypropylene fibers with different lengths is limited. They are added at three time points. The synergistic effect of each formula parameter and each process parameter is combined to achieve the expected technical effect of the present invention.

[0040] The interface enhancer prepared by the present invention is used to coat the outer surface of brick-concrete recycled aggregate to improve the interface strength between the old binder and the old aggregate particles in the brick-concrete recycled aggregate, thereby improving the performance of the brick-concrete recycled aggregate. The brick-concrete recycled aggregate is obtained by crushing the construction waste generated by the demolition of brick-concrete buildings, and the brick-concrete content of the brick-concrete recycled aggregate is not less than 10wt%. There are multiple interface transition zones inside recycled cement concrete and recycled asphalt mixtures, including between new binder and old aggregate, between old binder and old aggregate, and between new binder and old binder. Only by improving the interface between old binder and old aggregate can the performance of the recycled aggregate be fundamentally improved, and then the road performance of the recycled cement concrete and recycled asphalt mixture can be fundamentally improved.

[0041] The cement-based interface enhancer for brick-concrete recycled aggregate and the preparation method thereof of the present invention have the following beneficial effects:

[0042] (1) The interface enhancer of the present invention combines quick drying and hardening, high early strength, excellent water retention, anti-seepage and anti-cracking, and can form a dense reinforcement coating on the surface of brick-concrete recycled aggregate.

[0043] (2) The interface enhancer of the present invention sets initially within 10 minutes at room temperature, reaches a compressive strength of more than 5 MPa within 8 hours, and reaches a compressive strength of more than 20 MPa within 24 hours. It can form a uniform and dense reinforcing coating on the surface of brick-concrete recycled aggregate, effectively reduce the water absorption rate of the recycled aggregate, and improve the interface bonding strength and crack resistance between the old binder and the old aggregate particles; at the same time, it can meet the needs of rapid on-site construction and secondary mixing, and provide a reliable interface reinforcement solution for recycled aggregate concrete, recycled asphalt mixture and mortar.

[0044] (3) The interface enhancer of the present invention is designed for brick-concrete recycled aggregates with high water absorption (10-25%) and high porosity. Through the synergistic effect of the proportions of each component, each process step and process parameters, the rapid hardening, water absorption control (secondary water absorption rate is less than 5%) and crack resistance improvement of brick-concrete recycled aggregates are achieved.

[0045] (4) The present invention can accurately solve the defects of brick-concrete recycled aggregates, has strong process adaptability (brick-concrete recycled aggregates can be used directly after being coated with interface enhancers, without the need for pre-drying, and can be used immediately), has good environmental protection and economic efficiency (promotes the resource utilization of construction waste and shortens the construction period), and fills the technical gap in this field.

[0046] (5) After being coated and strengthened with the interface enhancer of the present invention, the brick-concrete recycled aggregate can directly replace the natural aggregate without drying and be used for secondary mixing and pouring of recycled aggregate concrete, recycled asphalt mixture or mortar. This not only simplifies the construction process, but also effectively promotes the sustainable application of brick-concrete recycled aggregate in road engineering.

[0047] (6) The interface enhancer of the present invention is coated on the outer surface of the brick-concrete recycled aggregate to improve the interface bonding strength between the old binder and the old aggregate particles in the brick-concrete recycled aggregate, thereby fundamentally improving the performance of the brick-concrete recycled aggregate. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 1. It is a process flow chart of a preferred embodiment of a cement-based interface enhancer for brick-concrete recycled aggregate and a preparation method thereof according to the present invention;

[0049] Figure 2 for Figure 1 Actual photos of the rapid-hardening Portland cement in the illustrated embodiment;

[0050] Figure 3 for Figure 1 Photos of the quartz sand in the illustrated embodiments, including: (a) quartz sand with a particle size of 75-90 μm, (b) quartz sand with a particle size of 90-150 μm, and (c) quartz sand with a particle size of 150-300 μm;

[0051] Figure 4 for Figure 1 Actual photographs of polypropylene fibers in the illustrated embodiments, wherein: (a) polypropylene fibers with a length of 1-3 mm, (b) polypropylene fibers with a length of 3-6 mm, and (c) polypropylene fibers with a length of 6-9 mm;

[0052] Figure 5 for Figure 1 A photograph of the solution obtained by dissolving six additives in water in step 4 of the interface enhancer preparation process of the illustrated embodiment;

[0053] Figure 6 for Figure 1 A photograph of the process of adding part of the solution to the blender in step 5 of the interface enhancer preparation process of the embodiment shown;

[0054] Figure 7 for Figure 1A photograph showing step 6 of the interface enhancer preparation process of the illustrated embodiment, wherein quartz sand with a particle size of 75-90 μm and polypropylene fibers with a length of 1-3 mm are added to a blender to mix the substances;

[0055] Figure 8 for Figure 1 A photograph showing step 7 of the interface enhancer preparation process in the illustrated embodiment, wherein a portion of the solution, quartz sand with a particle size of 90-150 μm, and polypropylene fibers with a length of 3-6 mm are added to a blender to mix the substances;

[0056] Figure 9 for Figure 1 A photograph of step eight in the interface enhancer preparation process of the illustrated embodiment, wherein the remaining solution, quartz sand with a particle size of 150-300 μm, and polypropylene fibers with a length of 6-9 mm are added to a blender to mix the substances;

[0057] Figure 10 for Figure 1 Photos of cement-based interface enhancers for brick-concrete recycled aggregates prepared in the examples shown;

[0058] Figure 11 for Figure 1 The microscopic morphology of the recycled aggregate of the brick-concrete type before coating with the interface enhancer in the embodiment shown, wherein: (a) the interface morphology between the old binder and the old aggregate particles, (b) the internal morphology of the recycled aggregate;

[0059] Figure 12 for Figure 1 The microscopic morphology of the recycled aggregate of the brick-concrete type after coating with the interface enhancer in the embodiment shown, wherein: (a) the interface morphology between the old binder and the old aggregate particles, (b) the internal morphology of the recycled aggregate;

[0060] Figure 13 for Figure 1 Electron probe microscopic analysis photos of brick-concrete recycled aggregate before coating with interface reinforcing agent in the embodiment shown, including: (a) silicon element distribution, (b) calcium element distribution, (c) sulfur element distribution;

[0061] Figure 14 for Figure 1 The electron probe microscopic analysis photos of the brick-concrete recycled aggregate after coating with the interface enhancer in the embodiment shown, including: (a) silicon element distribution, (b) calcium element distribution, and (c) sulfur element distribution. DETAILED DESCRIPTION

[0062] In order to further understand the content of the present invention, the present invention will be described in detail below with reference to specific embodiments.

[0063] Example 1:

[0064] According to a preferred embodiment of the cement-based interface enhancer for brick-concrete recycled aggregate of the present invention, the interface enhancer is used to wrap the outer surface of the brick-concrete recycled aggregate, and the brick-concrete content of the brick-concrete recycled aggregate is not less than 10wt%; the addition amount of each substance in the interface enhancer accounts for the mass percentage of the interface enhancer, which is 24wt% of fast-hardening Portland cement, 62wt% of quartz sand, 3.6wt% of silica fume, 0.2wt% of water reducer, 0.3wt% of hardener, 0.1wt% of accelerator, 0.1wt% of hydroxypropyl methylcellulose, 0.4wt% of silane, 0.2wt% of shrinkage reducer, 0.1wt% of polypropylene fiber, and 9wt% of water, and the sum of the contents of each substance is 100wt%, wherein the ratio of the mass of the water to the sum of the mass of the fast-hardening Portland cement and the silica fume is 0.326, which is controlled within the range of 0.2-0.4.

[0065] The model of the rapid hardening Portland cement is 42.5R; the specific surface area of ​​the silica fume is 320m 2 / kg; the water reducer is a polycarboxylic acid water reducer with a solid content of 30%; the shrinkage reducing agent is Sika Control-75 shrinkage reducing agent, the chemical component of which is mainly hydroxyl compounds.

[0066] The hardener is composed of calcium formate and calcium acetate, with the mass percentages of the two substances respectively accounting for 40wt% of the hardener and 60wt% of the calcium acetate. The accelerator is composed of calcium sulfate and aluminum sulfate, with the mass percentages of the two substances respectively accounting for 50wt% of the calcium sulfate and 50wt% of the aluminum sulfate.

[0067] The quartz sand includes three particle sizes, namely 150-300 μm, 90-150 μm, and 75-90 μm; the mass percentage of each particle size in the quartz sand is: particle size 150-300 μm accounts for 21 wt%, particle size 90-150 μm accounts for 50 wt%, and particle size 75-90 μm accounts for 29 wt%.

[0068] The polypropylene fibers include three length grades, namely 1-3 mm, 3-6 mm, and 6-9 mm; the mass percentage of each length grade in the polypropylene fibers is: 1-3 mm length accounts for 22 wt%, 3-6 mm length accounts for 46 wt%, and 6-9 mm length accounts for 32 wt%; the diameter of the polypropylene fibers with a length of 1-3 mm is 18-28 μm, and the diameters of the polypropylene fibers with a length of 3-6 mm and a length of 6-9 mm are both 28-38 μm.

[0069] like Figure 1 As shown, this embodiment also provides a method for preparing a cement-based interface enhancer for brick-concrete recycled aggregate, which is used to prepare the above-mentioned cement-based interface enhancer for brick-concrete recycled aggregate, and includes the following steps in order:

[0070] Step 1: Weigh each material according to the designed material ratio;

[0071] Step 2: Mix calcium formate and calcium acetate evenly according to the designed material ratio to obtain a hardener for standby use; mix calcium sulfate and aluminum sulfate evenly according to the designed material ratio to obtain an accelerator for standby use;

[0072] Step 3: Put all the rapid hardening Portland cement and silica fume into a mixer and stir them to mix the two substances evenly to obtain dry material;

[0073] Step 4: Add the water reducer, hardener, accelerator, hydroxypropyl methylcellulose, shrinkage reducer and silane to the water in sequence and stir until all six substances are dissolved in the water to form a solution;

[0074] Step 5: Add part of the solution into the blender and mix it with the dry ingredients;

[0075] Step 6: Add quartz sand with a particle size of 75-90 μm and polypropylene fiber with a length of 1-3 mm into the blender and continue stirring to mix the materials;

[0076] Step 7: Add part of the solution, quartz sand with a particle size of 90-150 μm, and polypropylene fiber with a length of 3-6 mm into a blender and continue stirring to mix the substances;

[0077] Step 8: Add the remaining solution, quartz sand with a particle size of 150-300 μm, and polypropylene fiber with a length of 6-9 mm into the blender and continue stirring to mix the substances;

[0078] Step 9: Increase the stirring speed and continue stirring to fully mix the substances to obtain a cement-based interface enhancer for brick-concrete recycled aggregate.

[0079] In step 1, among the materials weighed, the physical photo of rapid hardening Portland cement is as follows Figure 2 As shown; the actual photo of quartz sand is as follows Figure 3 As shown, among them: (a) is quartz sand with a particle size of 75-90μm, (b) is quartz sand with a particle size of 90-150μm, and (c) is quartz sand with a particle size of 150-300μm; the actual photo of polypropylene fiber is shown in Figure 4 As shown, among them: (a) is a polypropylene fiber with a length of 1-3 mm, (b) is a polypropylene fiber with a length of 3-6 mm, and (c) is a polypropylene fiber with a length of 6-9 mm.

[0080] In step 3, the rapid-hardening silicate cement and silica fume are all put into a mixer and stirred at room temperature, a stirring speed of 170 r / min, and a stirring time of 1.5 min.

[0081] In step 4, water reducer, hardener, accelerator, hydroxypropyl methylcellulose, shrinkage reducing agent and silane are added to water in sequence and stirred. The stirring method is manual stirring and the stirring temperature is room temperature. The mixing time after adding the water reducer is 1.5 minutes, the mixing time after adding the hardener is 2.5 minutes, the mixing time after adding the accelerator is 2.5 minutes, the mixing time after adding the hydroxypropyl methylcellulose is 2.5 minutes, the mixing time after adding the shrinkage reducing agent is 2.5 minutes, and the mixing time after adding the silane is 1.5 minutes. The actual photo of the solution obtained in this step is as follows Figure 5 shown.

[0082] In step 5, the amount of solution added is 30wt% of the total solution, the stirring temperature is room temperature, the stirring speed is 170r / min, and the stirring time is 1.5min. The operation process of this step is as follows Figure 6 shown.

[0083] In step 6, quartz sand with a particle size of 75-90 μm and polypropylene fiber with a length of 1-3 mm are added to the mixer and stirred at room temperature, a stirring speed of 170 r / min, and a stirring time of 1.5 min. Figure 7 shown.

[0084] In step 7, part of the solution, quartz sand with a particle size of 90-150 μm, and polypropylene fiber with a length of 3-6 mm are added to the blender and stirred. The amount of solution added is 40 wt% of the total solution. The stirring temperature is room temperature, the stirring speed is 170 rpm, and the stirring time is 2.5 minutes. The photo of the mixing of the various substances in this step is shown in the figure. Figure 8 shown.

[0085] In step eight, the remaining solution, quartz sand with a particle size of 150-300 μm, and polypropylene fiber with a length of 6-9 mm are added to the blender and stirred continuously. The amount of solution added is 30 wt% of the total solution. The stirring temperature is room temperature, the stirring speed is 170 rpm, and the stirring time is 2.5 min. The photo of the mixing of the various substances in this step is shown in FIG. Figure 9 shown.

[0086] In step nine, the stirring speed is increased to 320r / min and the stirring time is 4min. The cement-based interface enhancer for brick-concrete recycled aggregate obtained after stirring in this step is as follows: Figure 10 shown.

[0087] The interface enhancer is used to strengthen the surface of brick-concrete recycled aggregate. The method is as follows: the brick-concrete recycled aggregate is placed in a granulator containing the interface enhancer for rotational coating. The initial mass of the brick-concrete recycled aggregate and its corresponding interface enhancer have a mass ratio of 3:1.8. The rotational coating temperature is room temperature, the rotational coating speed is 170r / min, and the rotational coating time is 4min. After rotational coating, the outer surface of the brick-concrete recycled aggregate is coated with a thin layer of slurry shell with a thickness of 1.5mm. After the rotational coating is completed, the brick-concrete recycled aggregate coated with the slurry shell is spread out and naturally cured for 1.2h, and then transferred to a closed moisturizing box for further curing. The curing temperature is 20±2℃, the curing humidity is 60±5%, and the curing time is 22h. This completes the surface coating and strengthening of the brick-concrete recycled aggregate by the interface enhancer. After curing, brick-concrete recycled aggregates can be immediately used in the preparation of road engineering materials such as cement concrete, asphalt mixture or mortar.

[0088] In this embodiment, the quartz sand has three particle size ranges: 150-300μm, 90-150μm, and 75-90μm. This means that 150μm ≤ particle size < 300μm, 90μm ≤ particle size < 150μm, and 75μm ≤ particle size < 90μm. For each particle size range, the material, after passing through the upper and lower sieves, has a particle size between the upper and lower sieves. For example, a particle size of 90-150μm (90μm ≤ particle size < 150μm) means that the material, after passing through a 150μm sieve and a 90μm sieve, has a particle size between 90-150μm.

[0089] Polypropylene fibers come in three lengths: 6-9mm, 3-6mm, and 1-3mm, meaning 6mm ≤ length ≤ 9mm, 3mm ≤ length < 6mm, and 1mm ≤ length < 3mm. Polypropylene fibers with a length of 1-3mm have a diameter of 18-28μm, meaning 18μm ≤ diameter < 28μm, and any diameter within this range is acceptable. Polypropylene fibers with a length of 3-6mm and 6-9mm have a diameter of 28-38μm, meaning 28μm ≤ diameter ≤ 38μm, and any diameter within this range is acceptable.

[0090] In the process of preparing the interface enhancer in this embodiment, the selection of each substance, the dosage of each substance, the order of addition of each substance, and the process parameters of each step are all very important. In particular, the layer-by-layer progressive addition of three types of quartz sand with different particle sizes and three types of polypropylene fibers with different lengths plays a key role. The timing of adding the three types of quartz sand with different particle sizes and three types of polypropylene fibers with different lengths is limited. They are added at three time points. The synergistic effect of the various formula parameters and the various process parameters is combined to achieve the expected technical effects of this embodiment.

[0091] The cement-based interface enhancer for brick-concrete recycled aggregate and its preparation method in this embodiment have the following beneficial effects: (1) The interface enhancer combines fast drying and hardening, high early strength, excellent water retention, anti-seepage and anti-cracking, and can form a dense reinforcement coating on the surface of brick-concrete recycled aggregate. (2) The interface enhancer is designed for brick-concrete recycled aggregate with high water absorption and high porosity. Through the synergistic effect of the proportions of each component, each process step and process parameters, it achieves rapid hardening, water absorption control and improved crack resistance. (3) After the brick-concrete recycled aggregate is coated and strengthened with the interface enhancer, it can directly replace natural aggregate without drying and can be used immediately. (4) The interface enhancer is coated on the outer surface of the brick-concrete recycled aggregate to improve the interface bonding strength between the old binder and the old aggregate particles in the brick-concrete recycled aggregate, thereby fundamentally improving the performance of the brick-concrete recycled aggregate.

[0092] Example 2:

[0093] According to another preferred embodiment of the cement-based interface enhancer for brick-concrete recycled aggregate of the present invention, the proportion of each component, process steps, technical principles, usage method, beneficial effects, etc. are basically the same as those of the first embodiment, except that:

[0094] The addition amount of each substance in the interface enhancer accounts for the following mass percentages of the interface enhancer: fast-hardening Portland cement 22wt%, quartz sand 64wt%, silica fume 3wt%, water reducer 0.2wt%, hardener 0.2wt%, accelerator 0.05wt%, hydroxypropyl methylcellulose 0.05wt%, silane 0.3wt%, shrinkage reducer 0.1wt%, polypropylene fiber 0.1wt%, and water 10wt%, and the sum of the contents of each substance is 100wt%, wherein the ratio of the mass of the water to the sum of the mass of the fast-hardening Portland cement and the silica fume is 0.4, which is controlled within the range of 0.2-0.4.

[0095] The model of the rapid hardening Portland cement is 42.5R; the specific surface area of ​​the silica fume is 300m 2 / kg; the water reducer is a polycarboxylic acid water reducer with a solid content of 30%; the shrinkage reducing agent is Sika Control-75 shrinkage reducing agent, the chemical component of which is mainly hydroxyl compounds.

[0096] The hardener is composed of calcium formate and calcium acetate, with the mass percentage of the two substances respectively accounting for 35wt% of the hardener and 65wt% of the calcium acetate. The accelerator is composed of calcium sulfate and aluminum sulfate, with the mass percentage of the two substances respectively accounting for 45wt% of the calcium sulfate and 55wt% of the aluminum sulfate.

[0097] The quartz sand includes three particle sizes, namely 150-300 μm, 90-150 μm, and 75-90 μm; the mass percentage of each particle size in the quartz sand is: particle size 150-300 μm accounts for 18 wt%, particle size 90-150 μm accounts for 52 wt%, and particle size 75-90 μm accounts for 30 wt%.

[0098] The polypropylene fibers include three length grades, namely 1-3 mm, 3-6 mm, and 6-9 mm; the mass percentage of each length grade in the polypropylene fibers is: 1-3 mm length accounts for 20 wt%, 3-6 mm length accounts for 50 wt%, and 6-9 mm length accounts for 30 wt%; the diameter of the polypropylene fibers with a length of 1-3 mm is 18-28 μm, and the diameters of the polypropylene fibers with a length of 3-6 mm and a length of 6-9 mm are both 28-38 μm.

[0099] In step 3, the rapid-hardening silicate cement and silica fume are all put into a mixer and stirred at room temperature, a stirring speed of 140 r / min, and a stirring time of 2 min.

[0100] In step 4, the water reducer, hardener, accelerator, hydroxypropyl methylcellulose, shrinkage reducing agent and silane are added to the water in turn and stirred. The stirring method is manual mixing and the stirring temperature is room temperature. The mixing time after adding the water reducer is 1 min, the mixing time after adding the hardener is 2 min, the mixing time after adding the accelerator is 2 min, the mixing time after adding the hydroxypropyl methylcellulose is 2 min, the mixing time after adding the shrinkage reducing agent is 2 min, and the mixing time after adding the silane is 1 min.

[0101] In step 5, the amount of solution added is 25 wt % of the total solution, the stirring temperature is room temperature, the stirring speed is 140 r / min, and the stirring time is 2 min.

[0102] In step six, quartz sand with a particle size of 75-90 μm and polypropylene fiber with a length of 1-3 mm are added into the mixer and stirred continuously at room temperature, a stirring speed of 140 r / min, and a stirring time of 2 min.

[0103] In step seven, part of the solution, quartz sand with a particle size of 90-150 μm, and polypropylene fiber with a length of 3-6 mm are added to the mixer and continued stirring. The amount of solution added is 45 wt% of the total solution. The stirring temperature is room temperature, the stirring speed is 140 r / min, and the stirring time is 3 min.

[0104] In step eight, the remaining solution, quartz sand with a particle size of 150-300 μm, and polypropylene fiber with a length of 6-9 mm are added to the mixer and continued stirring. The amount of solution added is 30 wt % of the total solution. The stirring temperature is room temperature, the stirring speed is 140 r / min, and the stirring time is 3 min.

[0105] In step nine, the stirring speed is increased to 280 r / min and the stirring time is 5 min.

[0106] The surface of brick-concrete recycled aggregate is reinforced with an interface enhancer by coating it with the following: The brick-concrete recycled aggregate is placed in a granulator containing the interface enhancer and subjected to rotational coating. The initial mass of the brick-concrete recycled aggregate is 3:1.5, and the rotational coating is carried out at room temperature, a speed of 150 r / min, and a duration of 5 minutes. After the rotational coating, the outer surface of the brick-concrete recycled aggregate is coated with a 1mm thick layer of slurry. The slurry-coated brick-concrete recycled aggregate is spread out and naturally cured for 1 hour, then transferred to a sealed moisturizing chamber for further curing at a temperature of 20±2°C, a humidity of 60±5%, and a duration of 20 hours. This completes the surface coating and reinforcement of the brick-concrete recycled aggregate with the interface enhancer. After curing, the brick-concrete recycled aggregate can be immediately used in the preparation of road engineering materials such as cement concrete, asphalt mixture, or mortar.

[0107] Example 3:

[0108] According to another preferred embodiment of the cement-based interface enhancer for brick-concrete recycled aggregate of the present invention, the proportion of each component, process steps, technical principles, usage method, beneficial effects, etc. are basically the same as those of the first embodiment, except that:

[0109] The addition amount of each substance in the interface enhancer accounts for the following mass percentages of the interface enhancer: fast-hardening Portland cement 26wt%, quartz sand 60wt%, silica fume 4wt%, water reducer 0.3wt%, hardener 0.3wt%, accelerator 0.1wt%, hydroxypropyl methylcellulose 0.1wt%, silane 0.5wt%, shrinkage reducer 0.2wt%, polypropylene fiber 0.1wt%, and water 8.4wt%. The sum of the contents of each substance is 100wt%, wherein the ratio of the mass of the water to the sum of the mass of the fast-hardening Portland cement and the silica fume is 0.28, which is controlled within the range of 0.2-0.4.

[0110] The model of the rapid hardening Portland cement is 42.5R; the specific surface area of ​​the silica fume is 350m 2 / kg; the water reducer is a polycarboxylic acid water reducer with a solid content of 30%; the shrinkage reducing agent is Sika Control-75 shrinkage reducing agent, the chemical component of which is mainly hydroxyl compounds.

[0111] The hardener is composed of calcium formate and calcium acetate, with the mass percentages of the two substances respectively accounting for 45wt% of the hardener and 55wt% of the calcium acetate. The accelerator is composed of calcium sulfate and aluminum sulfate, with the mass percentages of the two substances respectively accounting for 55wt% of the accelerator.

[0112] The quartz sand includes three particle sizes, namely 150-300 μm, 90-150 μm, and 75-90 μm; the mass percentage of each particle size in the quartz sand is: particle size 150-300 μm accounts for 25wt%, particle size 90-150 μm accounts for 47wt%, and particle size 75-90 μm accounts for 28wt%.

[0113] The polypropylene fibers include three length grades, namely 1-3 mm, 3-6 mm, and 6-9 mm; the mass percentage of each length grade in the polypropylene fibers is: 1-3 mm length accounts for 24 wt%, 3-6 mm length accounts for 42 wt%, and 6-9 mm length accounts for 34 wt%; the diameter of the polypropylene fibers with a length of 1-3 mm is 18-28 μm, and the diameters of the polypropylene fibers with a length of 3-6 mm and a length of 6-9 mm are both 28-38 μm.

[0114] In step 3, the rapid hardening silicate cement and silica fume are all put into a mixer and stirred at room temperature, a stirring speed of 200 r / min, and a stirring time of 1 min.

[0115] In step 4, the water reducer, hardener, accelerator, hydroxypropyl methylcellulose, shrinkage reducing agent and silane are added to the water in turn and stirred. The stirring method is manual mixing and the stirring temperature is room temperature. The mixing time after adding the water reducer is 2 minutes, the mixing time after adding the hardener is 3 minutes, the mixing time after adding the accelerator is 3 minutes, the mixing time after adding the hydroxypropyl methylcellulose is 3 minutes, the mixing time after adding the shrinkage reducing agent is 3 minutes, and the mixing time after adding the silane is 2 minutes.

[0116] In step 5, the amount of solution added is 35 wt % of the total solution, the stirring temperature is room temperature, the stirring speed is 200 r / min, and the stirring time is 1 min.

[0117] In step six, quartz sand with a particle size of 75-90 μm and polypropylene fiber with a length of 1-3 mm are added into the mixer and stirred continuously at room temperature, a stirring speed of 200 r / min, and a stirring time of 1 min.

[0118] In step seven, part of the solution, quartz sand with a particle size of 90-150 μm, and polypropylene fiber with a length of 3-6 mm are added to the mixer and continued stirring. The amount of solution added is 40 wt % of the total solution. The stirring temperature is room temperature, the stirring speed is 200 r / min, and the stirring time is 2 min.

[0119] In step eight, the remaining solution, quartz sand with a particle size of 150-300 μm, and polypropylene fiber with a length of 6-9 mm are added to the mixer and continued stirring. The amount of solution added is 25 wt% of the total solution. The stirring temperature is room temperature, the stirring speed is 200 r / min, and the stirring time is 2 min.

[0120] In step nine, the stirring speed is increased to 350 r / min and the stirring time is 3 min.

[0121] The surface of brick-concrete recycled aggregate is reinforced with an interface enhancer: the brick-concrete recycled aggregate is placed in a granulator filled with an interface enhancer and subjected to rotational coating. The initial mass of the brick-concrete recycled aggregate is 3:2 with the corresponding interface enhancer. The rotational coating is carried out at room temperature, a speed of 180 r / min, and a duration of 3 minutes. After the rotational coating, the outer surface of the brick-concrete recycled aggregate is coated with a 2mm thick layer of slurry. The slurry-coated brick-concrete recycled aggregate is spread out and naturally cured for 2 hours. It is then transferred to a sealed moisturizing chamber for further curing at a temperature of 20±2°C, a humidity of 60±5%, and a curing time of 24 hours. This completes the surface reinforcement of the brick-concrete recycled aggregate with the interface enhancer. After curing, the brick-concrete recycled aggregate can be immediately used in the preparation of road engineering materials such as cement concrete, asphalt mixture, or mortar.

[0122] Comparative Example 1:

[0123] In the three examples above, when preparing the interface enhancer, three different quartz sand particle sizes and three different polypropylene fiber lengths were added layer by layer. The six admixtures (water reducer, hardener, accelerator, hydroxypropyl methylcellulose, shrinkage reducer, and silane) dissolved in water were also added layer by layer. The timing for adding the three different quartz sand particle sizes and three different polypropylene fiber lengths was specified, with each addition occurring at three different time points. Furthermore, the solution was divided into three portions and added at different time points.

[0124] The selection and proportions of the various substances in the interface enhancer of Comparative Example 1 were the same as those in Example 1, as were the proportions of the three different particle sizes of quartz sand and the three different lengths of polypropylene fibers. However, the preparation method of the interface enhancer did not adopt a layer-by-layer approach. Instead, the three different particle sizes of quartz sand, the three different lengths of polypropylene fibers, and the solution were all added to the blender at a single point in time.

[0125] The preparation process of the interface enhancer in Comparative Example 1 includes the following steps: placing rapid-hardening Portland cement, silica fume, and third-grade quartz sand into a blender and stirring uniformly to obtain a dry material at a stirring speed of 140-200 r / min for 1-2 minutes; adding a water reducer, a hardener, a setting accelerator, hydroxypropyl methylcellulose, a shrinkage reducer, and silane into water and stirring to form a solution, stirring the liquid material for 1-2 minutes and the solid material for 2-3 minutes; adding the entire solution into the blender and stirring together with the dry material at a stirring speed of 140-200 r / min for 1-2 minutes; adding the third-grade length polypropylene fiber into the blender and stirring at a stirring speed of 140-200 r / min for 2-3 minutes; increasing the stirring speed to 280-350 r / min and continuing stirring for 3-5 minutes to fully mix the materials. The interface enhancer is used to coat and strengthen the surface of brick-concrete recycled aggregate, and the coating method and process parameters are the same as those in Example 1.

[0126] Comparative Example 2:

[0127] The interface enhancers of the above three embodiments contain fast-hardening Portland cement, quartz sand of three different particle sizes, and polypropylene fibers of three different lengths. In addition, the three quartz sands of three different particle sizes and the three polypropylene fibers of three different lengths are added layer by layer during the preparation process.

[0128] The interface enhancer of Comparative Example 2 does not contain quartz sand and polypropylene fiber, the cement used is only ordinary Portland cement, and the order of adding the various substances is not considered during the preparation process.

[0129] The weight percentages of the various substances in the interface enhancer of Comparative Example 2 are: 56 wt % of ordinary Portland cement, 24 wt % of silica fume, 2.2 wt % of a water reducer, 2.2 wt % of a hardener, 1.5 wt % of an accelerator, 1.4 wt % of hydroxypropyl methylcellulose, 1.5 wt % of a silane, 1.2 wt % of a shrinkage reducer, and 10 wt % of water. The specific substances of the various admixtures are the same as those in Example 1, and the specific substances and proportions of the hardener and accelerator are also the same as those in Example 1.

[0130] The preparation process of the interface enhancer in Comparative Example 2 includes the following steps: ordinary Portland cement and silica fume are placed in a blender and stirred uniformly to obtain a dry material at a stirring speed of 140-200 r / min for 1-2 minutes; a water reducer, a hardener, an accelerator, hydroxypropyl methylcellulose, a shrinkage reducer, and silane are sequentially added to water and stirred to form a solution, with the liquid material stirred for 1-2 minutes and the solid material stirred for 2-3 minutes; the solution is added to the blender and stirred together with the dry material at a stirring speed of 140-200 r / min for 1-2 minutes. The interface enhancer is used to coat and strengthen the surface of recycled aggregate for brick-concrete construction, using the same coating method and process parameters as in Example 1.

[0131] According to relevant testing standards and specifications, including "Test Procedure for Cement and Cement Concrete for Highway Engineering" (JTG3420-2020), "Pebbles and Crushed Stones for Construction" (GB / T 14685-2022), "Light Aggregate and Its Test Methods Part 2: Test Method for Light Aggregate" (GB / T 17431.2-2010), etc., the interface enhancers prepared in the above three embodiments and two comparative examples, and the brick-concrete recycled aggregates before and after coating with the interface enhancers were subjected to performance tests. The test equipment, test environment, test conditions, sample shape and size used were the same. The test results are shown in Tables 1-3.

[0132]

[0133] With respect to Example 1, the pores of the brick-concrete recycled aggregate before and after coating with the interface enhancer were microscopically tested by mercury intrusion porosimetry (MIP). The test results are shown in Table 4.

[0134]

[0135] The microscopic test results in Table 4 show that coating with an interfacial enhancer significantly improved the interfacial bond strength between the old binder and the old aggregate particles. The original brick-concrete recycled aggregate contained numerous macroscopic pores and a loose interfacial transition zone (ITZ). These pores originate from the honeycomb structure formed during the sintering of clay bricks, leading to increased water absorption and poorer mechanical properties. In contrast, the total porosity of the brick-concrete recycled aggregate significantly decreased after coating with an interfacial enhancer. This change is attributed to the micro-filling effect of the interfacial enhancer, which synergizes with cement hydration products to fill the microcracks and pores between the old binder and the old aggregate. Simultaneously, the accelerator and hardener promote silicate polymerization, forming ettringite (AFt) and calcium silicate hydrate (CSH) gels, further sealing the pores and strengthening the interfacial chemical bonding. The interfacial enhancer reconstructs the ITZ through multi-stage filling and chemical bonding, bringing the interfacial bond strength close to that of natural aggregate.

[0136] In addition, in Example 1, the microscopic morphology of the brick-concrete recycled aggregate before coating the interface reinforcing agent is as follows: Figure 11 As shown in Figure 2, (a) is the interface morphology between the old binder and the old aggregate particles, and (b) is the internal morphology of the recycled aggregate. The microscopic morphology of the brick-concrete recycled aggregate after coating with the interface enhancer is shown in Figure 2. Figure 12 As shown in the figure, (a) is the interface morphology between the old binder and the old aggregate particles, and (b) is the internal morphology of the recycled aggregate. Figure 13 As shown in the figure, (a) is the distribution of silicon, (b) is the distribution of calcium, and (c) is the distribution of sulfur. The electron probe microscopic analysis of the recycled aggregate of brick-concrete after coating with interface enhancer is shown in the figure. Figure 14 As shown, (a) is the distribution of silicon elements, (b) is the distribution of calcium elements, and (c) is the distribution of sulfur elements.

[0137] Scanning electron microscope (SEM) images show that the surface of the original brick-concrete recycled aggregate exhibits a porous honeycomb structure, with numerous fibrous silicate phases and microcracks. The interface between the old binder and the old aggregate is loose, easily becoming a stress concentration point. After the brick-concrete recycled aggregate is coated with an interface reinforcing agent, a continuous, dense coating forms on its surface. At the microscopic scale, needle-shaped Ca(OH)2 crystals and amorphous CSH gel are evenly distributed in the interface transition zone. There is no significant debonding in the ITZ, and hydration products penetrate deeply into the aggregate's internal pores, forming a multi-stage reinforcement system of "physical filling, chemical bonding, and fiber bridging."

[0138] Electron probe microanalysis (EPMA) further revealed the strengthening mechanism of the interface enhancer: the interface enhancer penetrates the pores of the recycled aggregate for brick-concrete applications, enriching silicon and accelerating secondary hydration reactions. Subsequently, the surface is coated with calcium, introducing a large amount of calcium, forming a Ca-Si gradient distribution, promoting the formation of CSH gel and AFt. Ultimately, the silane in the interface enhancer forms a hydrophobic layer on the surface, reducing the surface free energy. This optimized interface structure significantly reduces the crushing value and water absorption of the recycled aggregate for brick-concrete applications after coating with the interface enhancer, significantly improving the mechanical interlocking and chemical bond strength between the old binder and the old aggregate, and laying the foundation for its application in cement concrete, asphalt mixtures, and mortar.

[0139] The raw materials used in the above examples and comparative examples, such as rapid-hardening Portland cement, ordinary Portland cement, quartz sand, silica fume, calcium formate, calcium acetate, calcium sulfate, aluminum sulfate, water reducer, hydroxypropyl methylcellulose, silane, and polypropylene fiber, were purchased from Beijing Municipal Road and Bridge Building Materials Group Co., Ltd., and Sika Control-75 shrinkage reducer was purchased from Nanjing Yaojie Energy Saving Technology Co., Ltd.

[0140] Special Note: The technical solution of this invention involves numerous parameters, and the synergistic effects between these parameters must be comprehensively considered to achieve the beneficial effects and significant improvements of this invention. Furthermore, the value ranges of each parameter in the technical solution were obtained through extensive testing. The inventors have recorded extensive experimental data for each parameter and their combinations. Due to space limitations, the specific experimental data will not be disclosed here.

Claims

1. A cement-based interface enhancer for brick-concrete recycled aggregate, characterized by: The interface enhancer is used to coat the outer surface of the brick-concrete recycled aggregate, and the brick-concrete content of the brick-concrete recycled aggregate is not less than 10wt%; the addition amount of each substance in the interface enhancer is as follows: 22-26wt% of fast-hardening Portland cement, 60-64wt% of quartz sand, 3-4wt% of silica fume, 0.2-0.3wt% of water reducer, 0.2-0.3wt% of hardener, 0.05-0.1wt% of accelerator, 0.05-0.1wt% of hydroxypropyl methylcellulose, 0.3-0.5wt% of silane, 0.1-0.2wt% of shrinkage reducer, 0.05-0.1wt% of polypropylene fiber, and 8-10wt% of water, and the sum of the contents of each substance is 100wt%, wherein the ratio of the mass of the water to the sum of the mass of the fast-hardening Portland cement and the silica fume is controlled within the range of 0.2-0.4; The quartz sand includes three particle sizes, namely 150-300 μm, 90-150 μm, and 75-90 μm; the mass percentage of each particle size in the quartz sand is: particle size 150-300 μm accounts for 18-25wt%, particle size 90-150 μm accounts for 47-52wt%, and particle size 75-90 μm accounts for 25-33wt%; The polypropylene fibers include three lengths: 1-3 mm, 3-6 mm, and 6-9 mm. The weight percentage of each length in the polypropylene fibers is: 1-3 mm in length accounts for 20-24 wt%, 3-6 mm in length accounts for 42-50 wt%, and 6-9 mm in length accounts for 28-35 wt%. The diameter of the polypropylene fibers with a length of 1-3 mm is 18-28 μm, and the diameters of the polypropylene fibers with a length of 3-6 mm and a length of 6-9 mm are both 28-38 μm. The hardening agent consists of calcium formate and calcium acetate.

2. The cement-based interface enhancer for brick-concrete recycled aggregate according to claim 1, characterized in that: The model of the rapid hardening silicate cement is 42.5R; the specific surface area of ​​the silica fume is 300-350m 2 / kg.

3. The cement-based interface enhancer for brick-concrete recycled aggregate according to claim 2, characterized in that: The water reducer is a polycarboxylic acid water reducer with a solid content of 30%.

4. The cement-based interface enhancer for brick-concrete recycled aggregate according to claim 3, characterized in that: The mass percentages of the two substances in the hardener are respectively 35-45 wt % of calcium formate and 55-65 wt % of calcium acetate.

5. The cement-based interface enhancer for brick-concrete recycled aggregate according to claim 4, characterized in that: The accelerating setting agent is composed of calcium sulfate and aluminum sulfate, and the mass percentages of the two substances in the accelerating setting agent are 45-55wt% of calcium sulfate and 45-55wt% of aluminum sulfate, respectively.

6. The cement-based interface enhancer for brick-concrete recycled aggregate according to claim 5, characterized in that: The shrinkage reducing agent is Sika Control-75 shrinkage reducing agent, and its chemical components are mainly hydroxyl compounds.

7. A method for preparing a cement-based interface enhancer for brick-concrete recycled aggregate, characterized in that: The cement-based interface enhancer for brick-concrete recycled aggregate according to any one of claims 1 to 6 comprises the following steps in order: Step 1: Weigh each material according to the designed material ratio; Step 2: Mix calcium formate and calcium acetate evenly according to the designed material ratio to obtain a hardener for standby use; mix calcium sulfate and aluminum sulfate evenly according to the designed material ratio to obtain an accelerator for standby use; Step 3: Put all the rapid hardening Portland cement and silica fume into a mixer and stir them to mix the two substances evenly to obtain dry material; Step 4: Add the water reducer, hardener, accelerator, hydroxypropyl methylcellulose, shrinkage reducer and silane to the water in sequence and stir until all six substances are dissolved in the water to form a solution; Step 5: Add part of the solution into the blender and mix it with the dry ingredients; Step 6: Add quartz sand with a particle size of 75-90 μm and polypropylene fiber with a length of 1-3 mm into the blender and continue stirring to mix the materials; Step 7: Add part of the solution, quartz sand with a particle size of 90-150 μm, and polypropylene fiber with a length of 3-6 mm into a blender and continue stirring to mix the substances; Step 8: Add the remaining solution, quartz sand with a particle size of 150-300 μm, and polypropylene fiber with a length of 6-9 mm into the blender and continue stirring to mix the substances; Step 9: Increase the stirring speed and continue stirring to fully mix the substances to obtain a cement-based interface enhancer for brick-concrete recycled aggregate.

8. The method for preparing a cement-based interface enhancer for brick-concrete recycled aggregate according to claim 7, characterized in that: In step 3, the rapid hardening Portland cement and silica fume are all put into a mixer and stirred at room temperature, a stirring speed of 140-200 r / min, and a stirring time of 1-2 min; In step 4, a water reducer, a hardener, an accelerating setting agent, hydroxypropyl methylcellulose, a shrinkage reducing agent and silane are sequentially added to water and stirred, and the stirring method is manual stirring at room temperature; The mixing time after adding the water reducer is 1-2 minutes, the mixing time after adding the hardener is 2-3 minutes, the mixing time after adding the accelerator is 2-3 minutes, the mixing time after adding the hydroxypropyl methylcellulose is 2-3 minutes, the mixing time after adding the shrinkage reducing agent is 2-3 minutes, and the mixing time after adding the silane is 1-2 minutes; In step 5, the amount of solution added is 25-35wt% of the total solution, the stirring temperature is room temperature, the stirring speed is 140-200r / min, and the stirring time is 1-2min; In step 6, quartz sand with a particle size of 75-90 μm and polypropylene fiber with a length of 1-3 mm are added to the mixer and stirred at room temperature, a stirring speed of 140-200 r / min, and a stirring time of 1-2 min; In step 7, part of the solution, quartz sand with a particle size of 90-150 μm, and polypropylene fiber with a length of 3-6 mm are added to the blender and stirred continuously. The amount of solution added is 35-45 wt% of the total solution. The stirring temperature is room temperature, the stirring speed is 140-200 r / min, and the stirring time is 2-3 min. In step eight, the remaining solution, quartz sand with a particle size of 150-300 μm, and polypropylene fiber with a length of 6-9 mm are added to the blender and continued stirring. The amount of solution added is 25-35 wt% of the total solution. The stirring temperature is room temperature, the stirring speed is 140-200 r / min, and the stirring time is 2-3 min. In step nine, the stirring speed is increased to 280-350 r / min, and the stirring time is 3-5 min.

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