Method for preparing low-clinker composite mortar material from granite weathered construction engineering residue soil and mortar

Abstract

The invention discloses a method for preparing a low-clinker composite mortar material from granite weathered construction engineering residue soil and mortar. The method comprises the following steps: settling and screening engineering residue soil, and respectively carrying out biomimetic mineralization modification, particle size allocation and proportioning on powdery clayey soil and coarse particles to form mixed mortar; according to the mixed mortar, granite weathering type constructional engineering muck solid waste can be fully utilized, the recycling rate reaches 96%, the performance of the mortar is improved by introducing a biomimetic mineralization modification technology, conditions are mild, no harmful by-products exist, and the mechanical performance of the composite mortar is excellent. Through a biomimetic mineralization modification technology, after the prepared mortar is cured for 28 days, the highest compressive strength can reach 65.45 MPa, and the compressive strength is superior to that of traditional OPC mortar, fly ash composite mortar and untreated muck mortar.

Description

Technical Field

[0001] The invention relates to the technical field of solid waste resource utilization and building materials, and specifically discloses a method for preparing a low-clinker composite mortar material by using granite weathered construction engineering debris and the mortar. Background Art

[0002] Construction waste is a type of solid waste generated in large quantities during urban infrastructure construction. Its main sources include subway tunnel construction, foundation pit excavation, highway construction and expansion, and other processes, with a huge annual output.

[0003] Statistics show that construction activities in certain first-tier cities generate over 100 million tons of construction waste annually. Because this waste is a complex mixture of soil, rocks, and building debris, its indiscriminate disposal can lead to environmental problems such as waste of land resources, water pollution, and the spread of dust. Currently, the mainstream treatment methods for construction waste include landfilling, simple backfilling, and partial reuse, but these methods have low overall utilization rates and fail to achieve high-value resource utilization.

[0004] Mortar is an inorganic binder widely used in construction projects. It is typically a mixture of cement, fine aggregate (such as river sand), and water. It is used for structural connections and surface treatments such as masonry, plastering, and repair. However, traditional mortar production faces two major challenges: first, environmental pressure. The high-temperature calcination process of cement clinker production is accompanied by large amounts of carbon emissions and is one of the main sources of carbon in the construction materials industry. Second, performance control is difficult. When high amounts of auxiliary cementitious materials or non-standard sand sources are used, mortar is prone to performance fluctuations such as poor fluidity, weak adhesion, and large drying shrinkage, which limits the promotion and application of solid waste alternatives.

[0005] At present, solid wastes such as fly ash, slag, and steel slag have been used as admixtures in the preparation of mortar. For example, Chinese patent CN108689663A discloses a composite mortar material based on fly ash. Although it realizes the utilization of industrial by-products, due to the low activity of fly ash and the slow development of early strength, it still requires the use of exogenous high-activity materials. Some other technologies attempt to introduce natural clay minerals, such as kaolin and illite, to explore their gelling potential after calcination. For example, Chinese patent CN115667178A proposes to add kaolin to the mortar system after calcination to enhance the cementing activity, thereby reducing the amount of cement clinker and improving the fluidity of the material. However, this process mostly relies on kaolin with higher purity, and the mining and transportation costs are high. Limestone calcined clay cement has received widespread attention in recent years. Chinese patent CN111875268A proposes to construct a low-carbon cementitious system by synergizing kaolin and limestone, significantly reducing the clinker dosage and carbon emissions. However, this system still relies on high-purity kaolin and does not involve the design of the aggregate system, which is prone to problems such as insufficient density and unstable mechanical properties.

[0006] Furthermore, the sand currently used in mortars is mostly sourced from freshwater river sand, resulting in high system costs. The paper "Research on Problems and Countermeasures of Sand Mining Management in Rivers of Guangdong Province" points out that the long-term and large-scale mining of natural river sand as fine aggregate has led to ecological damage to riverbeds, soil erosion, and mining bans in some areas. Using abundant sea sand to prepare mortar is susceptible to chloride erosion. The paper "Study on the Performance of Sea Sand Concrete and the Migration of Chloride Ions" simulated chloride ion penetration in concrete with varying concentration gradients. The results showed that chloride ions penetrate into low-concentration concrete over time, reducing concrete durability. Due to the limited mining of natural sand, manufactured sand has become a widely used fine aggregate, but its production cost is high. The paper "Analysis of the Performance of Manufactured Sand in Cement Concrete" states that the production of manufactured sand requires multiple stages of crushing, screening, shaping, and cleaning, relying on high-energy-consuming machinery and equipment, resulting in a complex process and significantly higher energy consumption per unit of sand produced than natural sand.

[0007] As previously mentioned, the fine particles in construction waste are primarily composed of kaolinite and illite. After heat treatment, they exhibit significant activity and can replace some cement clinker as a cementitious material. The coarse particles contain a high content of quartz, with particle sizes ranging from 0.075 to 5 mm, suggesting potential for use as recycled fine aggregate. Recycled fine aggregate is crucial for improving the density and strength of materials, particularly in the context of skeleton filling. Furthermore, the feldspar particles are primarily potassium feldspar, mostly in a coarse state. Some weathered feldspar in the fine particles also exhibits some cementitious activity after heat treatment, further enhancing the early strength and durability of the mortar.

[0008] Although existing processes have enhanced the activity of slag through heat treatment, insufficient attention has been paid to optimizing the interface of the treated particles, resulting in limited compatibility and mechanical synergy with the cementitious system. Specifically, the surfaces of activated slag particles prepared by existing methods generally lack sufficient interfacial reaction sites and good wettability, making it difficult to form effective interfacial bonding between the particles and the cementitious system, limiting further improvement in the overall performance of the material. Through biomimetic mineralization modification, a stable mineralized deposition layer can be formed in situ on the particle surface, significantly improving the chemical activity and hydrophilicity of the particle surface, thereby effectively enhancing the interfacial bonding strength and mechanical synergy.

[0009] To address the aforementioned issue of solid waste utilization, the inventors have developed a method and mortar for preparing low-clinker composite mortar materials using weathered granite construction waste. This method utilizes a gentle, environmentally friendly, and easily implemented interface enhancement method to further enhance the functionality of waste cementitious materials and aggregates. Consequently, the present invention classifies waste using sedimentation and screening methods, and introduces a mineralization modification process into powdery clay and coarse particles to form multifunctional components with active or reinforced interfaces, achieving efficient and synergistic resource utilization of all components of the construction waste. Summary of the Invention

[0010] The object of the present invention is to provide a method for preparing a low-clinker composite mortar material using weathered granite construction engineering debris and mortar, so as to solve the problems existing in the above background.

[0011] In a first aspect, the present invention provides a method for preparing a low-clinker composite mortar material using weathered granite construction waste, characterized in that the method comprises the following steps:

[0012] (1) Sedimentation and screening of construction waste soil to obtain powdery clay soil and coarse particles;

[0013] (2) After heat treatment of powdered clay soil, it is modified by biomimetic mineralization to obtain active powdered clay soil;

[0014] (3) After biomimetic mineralization modification of the coarse particles, the particle size is adjusted to obtain a gradation combination of recycled fine aggregate;

[0015] (4) mixing active powdered clay soil, limestone, cement clinker, water and recycled fine aggregate in a certain proportion to obtain a mixed mortar;

[0016] The construction slag in step (1) is granite weathered construction slag, and the kaolinite content of the construction slag is 10% to 75%, the illite content is 3% to 30%, the quartz content is 15% to 50%, and the feldspar content is 3% to 30%.

[0017] Preferably, the method further comprises (5) injecting the mixed mortar into a mold, curing and shaping the mortar, and obtaining a composite mortar material.

[0018] Preferably, in step (1), the sedimentation and screening of the construction waste soil comprises the following steps:

[0019] The construction waste soil is crushed, mixed with water, and a dispersant is added to obtain a construction waste soil suspension;

[0020] The engineering waste soil suspension is sieved to obtain the undersize liquid and the coarse particles on the sieve;

[0021] The liquid under the sieve and the coarse particles on the sieve are dried to obtain powdery clay soil and coarse particles.

[0022] Preferably, the dispersant is sodium hexametaphosphate.

[0023] Preferably, the construction waste soil, water and dispersant are mixed in a mass ratio of 1000: (4000-6000): (2-5) to obtain a construction waste soil suspension, and the construction waste soil suspension is passed through a 150-250 mesh sieve.

[0024] Preferably, the construction waste soil suspension is passed through a 200-mesh sieve.

[0025] Preferably, in step (2), when the powdered clay soil is heat-treated, the temperature is set to 550-850° C. and the time is set to 1.5-2.5 hours.

[0026] Preferably, in step (2), the biomimetic mineralization modification of powdered clay soil comprises the following steps:

[0027] The heat-treated powdered clay is added to a 0.1-0.5 mol / L CaCl2 solution and stirred evenly, and a 0.1-0.5 mol / L Na2CO3 solution is slowly added dropwise at a rate of 6-12 mL / min for 20-40 min. The entire powdered clay biomimetic mineralization modification process is stirred for 60-90 min to obtain a modified product; the modified product is subjected to solid-liquid separation, washed with deionized water, and dried at 50-70° C. to obtain a biomimetic mineralized modified powdered clay.

[0028] Preferably, the stirring speed is 300-600 rpm.

[0029] Preferably, the solid-liquid separation is performed by centrifugation and / or filtration.

[0030] Preferably, the deionized water washing is performed 2-5 times.

[0031] Preferably, in step (3), the biomimetic mineralization modification of the coarse particles comprises the following steps:

[0032] The coarse particles are immersed in a 0.5-2 mol / L NaOH solution for 15-45 minutes, and then washed with deionized water until neutral to obtain alkali-treated coarse particles;

[0033] The alkali-treated coarse particles are added to a 0.05-0.2 mol / L CaCl2 solution, and a 4-6 wt% water glass solution is slowly added dropwise at a rate of 3-6 mL / min for 15-30 min. The mixture is stirred and reacted at room temperature for 12-24 h to complete the biomimetic mineralization treatment.

[0034] The mineralized coarse particles are separated into solid and liquid, washed with deionized water, and dried at 50-70° C. to obtain biomimetic mineralized modified coarse particles.

[0035] Preferably, the stirring speed is 150-300 rpm.

[0036] Preferably, the solid-liquid separation is performed by centrifugation and / or filtration.

[0037] Preferably, the deionized water washing is performed 2-5 times.

[0038] Preferably, in step (3), the modified coarse particles are classified according to particle size and mixed according to mass ratio to form different recycled fine aggregate gradations, including the following combinations: components with particle sizes between 0.15 mm and 0.25 mm, 0.25 mm and 1 mm and 4 mm are mixed in a mass ratio of 2:1:1, 1:2:1 or 1:1:2.

[0039] Preferably, in step (4), the raw materials for preparing the composite cement material include, by mass percentage: 10% to 40% of active powdered clay, 5% to 20% of limestone, 40% to 85% of cement clinker, and 10% to 40% of recycled fine aggregate.

[0040] A second aspect of the present invention provides a composite mortar, which is prepared using the method of the first aspect.

[0041] Preferably, in step (5), the composite mortar material is obtained by curing at room temperature (25° C.) for 24 hours and then demoulding.

[0042] Preferably, after 28 days of curing, the obtained composite mortar material has a compressive strength of 58-66 MPa.

[0043] Preferably, after 28 days of curing, the obtained composite mortar material has a compressive strength of up to 65.45 MPa, which is better than traditional OPC mortar, fly ash composite mortar and untreated slag mortar.

[0044] The beneficial effects of the present invention are:

[0045] (1) The present invention achieves resource utilization of all components of construction waste. Construction waste is divided into powdered clay and coarse particles through sedimentation classification. These are then differentiated for utilization based on their composition and particle size characteristics. This avoids the large-scale landfill and disposal required in traditional waste treatment, significantly improves the synergistic utilization efficiency of multiphase minerals in the waste, and achieves an overall resource utilization rate of over 96%.

[0046] (2) The present invention introduces bionic mineralization modification technology to perform interface regulation and functionalization treatment on the powdered clay soil after heat treatment and the coarse particles after screening, further improving the cementing activity of the powdered clay soil and the interfacial bonding ability of the coarse particles. In addition, the technology is highly operable, has mild process conditions, and does not produce harmful by-products.

[0047] (3) The composite mortar prepared by the present invention exhibits excellent mechanical properties. Through biomimetic mineralization modification technology, the prepared mortar achieves a compressive strength of up to 65.45 MPa after 28 days of curing, which is superior to traditional OPC mortar, fly ash composite mortar, and untreated slag mortar.

[0048] In summary, the present invention not only achieves the goal of high-value resource utilization and carbon reduction and consumption reduction of construction waste, but also has comprehensive advantages such as a wide source of raw materials, a simple production process, and excellent material properties. It has engineering significance for promoting the recycling of solid waste and the development of green building materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 The XRD pattern of heat-treated silty clay after biomimetic mineralization modification in one embodiment is shown;

[0050] Figure 2 The TG-DSC curve of the coarse particles of one embodiment after biomimetic mineralization modification is shown. DETAILED DESCRIPTION

[0051] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0052] The construction waste used in the examples of the present invention was collected from Longhua District, Shenzhen City, Nanhai District, Foshan City, Conghua District, Guangzhou City, and Panyu District, Guangzhou City, Guangdong Province. The construction waste had a kaolinite content of 10% to 75%, an illite content of 3% to 30%, a quartz content of 15% to 50%, and a feldspar content of 3% to 30%. The coarse particles separated from the construction waste met the requirements of GB / T 14684-2011, "Construction Sand."

[0053] Example 1

[0054] A method for preparing a low-clinker composite mortar material using weathered granite construction slag comprises the following steps:

[0055] (1) The construction waste soil used was taken from the foundation pit of a certain structure in Longhua District, Shenzhen City, Guangdong Province. The XRD quantitative analysis results are as follows: kaolinite 22.4%, illite 20.0%, quartz 49.2%, feldspar 5.5%, and others 2.9%. The construction waste soil was placed in an oven and dried at 105℃ for 24 hours, then crushed manually. It was then mixed with water and sodium hexametaphosphate in a mass ratio of 1000:5000:3 to fully disperse it and form a waste soil suspension. The suspension was passed through a 200-mesh sieve, and water was added, stirred, and sieved three times. All the undersize liquid and coarse particles on the sieve were collected and dried separately to obtain powdery clay soil and coarse particles.

[0056] (2) The dried powdered clay was placed in a muffle furnace and calcined at 750 °C for 2 h. After cooling, it was added to a 0.2 mol / L CaCl2 solution and stirred evenly. Then, a 0.2 mol / L Na2CO3 solution was slowly added dropwise at 8 mL / min for 30 min. The entire reaction process was maintained at 400 rpm for 90 min. After the reaction was completed, the modified product was separated by centrifugation, washed with deionized water three times, and dried at 60 °C to obtain an activated powdered clay.

[0057] (3) The dried coarse particles were soaked in a 1 mol / L NaOH solution for 30 min, then washed with deionized water until neutral, added to a 0.1 mol / L CaCl2 solution, and 5 wt% water glass solution was slowly added at 3 mL / min for 30 min. The mixture was stirred at 200 rpm at room temperature for 18 h to complete the biomimetic mineralization treatment. The mineralized coarse particles were filtered and separated, washed with deionized water three times, and dried at 60°C to obtain recycled fine aggregate.

[0058] (4) The recycled fine aggregate was screened by particle size and divided into three particle size ranges: A, B, and C. Group A particles: 0.15mm-0.25mm; Group B particles: 0.25mm-1mm; Group C particles: 1mm-4mm. The above three types of particles were mixed in different mass proportions to form the following three recycled fine aggregate grading combinations: ①A:B:C=2:1:1; ②A:B:C=1:2:1; ③A:B:C=1:1:2.

[0059] (5) 530 g of active powdered clay, 265 g of limestone, 4503 g of Portland cement, and 1589 g of recycled fine aggregate (gradation combination ①) were placed in a mortar mixer and mixed evenly. 1.6 L of water was added and stirred rapidly to obtain a mortar mixture.

[0060] (6) Pour the obtained mortar mixture into a 70.7×70.7×70.7mm 3 The specimens were placed in a cubic mold and compacted on a cement mortar compaction table for 1 minute. The specimens were sealed with a film and naturally cured at room temperature for 24 hours before demoulding. The resulting specimens were named EM-SZ. The specimens were cured at room temperature for 3 days, 7 days and 28 days to test their mechanical properties.

[0061] Example 2

[0062] A method for preparing a low-clinker composite mortar material using weathered granite construction slag comprises the following steps:

[0063] (1) The construction waste soil used was obtained from a tunnel boring machine (TBM) in Nanhai District, Foshan City, Guangdong Province. The XRD quantitative analysis results are as follows: kaolinite 16.1%, illite 23.2%, quartz 38.2%, feldspar 4.6%, and others 17.9%. The construction waste soil was placed in an oven and dried at 105°C for 24 hours. It was then crushed manually and then mixed with water and sodium hexametaphosphate in a mass ratio of 1000:5000:3 to fully disperse it. A waste soil suspension was formed. The suspension was passed through a 200-mesh sieve, and water was added, stirred, and sieved three times. All the undersize liquid and coarse particles on the sieve were collected and dried separately to obtain powdery clay and coarse particles.

[0064] (2) The dried powdered clay was placed in a muffle furnace and calcined at 750 °C for 2 h. After cooling, it was added to a 0.2 mol / L CaCl2 solution and stirred evenly. Then, a 0.2 mol / L Na2CO3 solution was slowly added dropwise at 8 mL / min for 30 min. The entire reaction process was maintained at 400 rpm for 90 min. After the reaction was completed, the modified product was separated by centrifugation, washed with deionized water three times, and dried at 60 °C to obtain an activated powdered clay.

[0065] (3) The dried coarse particles were soaked in a 1 mol / L NaOH solution for 30 min, then washed with deionized water until neutral, added to a 0.1 mol / L CaCl2 solution, and 5 wt% water glass solution was slowly added at 3 mL / min for 30 min. The mixture was stirred at 200 rpm at room temperature for 18 h to complete the biomimetic mineralization treatment. The mineralized coarse particles were filtered and separated, washed with deionized water three times, and dried at 60°C to obtain recycled fine aggregate.

[0066] (4) The recycled fine aggregate was sieved according to particle size and divided into three particle size ranges: A, B, and C. Group A particles: 0.15mm-0.25nm; Group B particles: 0.25mm-1mm; Group C particles: 1mm-4mm. The above three types of particles were mixed in different mass proportions to form the following three recycled fine aggregate grading combinations: ①A:B:C=2:1:1; ②A:B:C=1:2:1; ③A:B:C=1:1:2.

[0067] (5) 1059 g of active powdered clay, 530 g of limestone, 3708 g of Portland cement, and 1324 g of recycled fine aggregate (gradation combination ①) were placed in a mortar mixer and mixed evenly. 1.6 L of water was added and stirred rapidly to obtain a mortar mixture.

[0068] (6) Pour the obtained mortar mixture into a 70.7×70.7×70.7mm 3The specimens were placed in a cubic mold and compacted on a cement mortar compaction table for 1 minute. The specimens were sealed with a film and naturally cured at room temperature for 24 hours before demoulding. The resulting specimens were named EM-FS. The specimens were cured at room temperature for 3 days, 7 days and 28 days to test their mechanical properties.

[0069] Example 3

[0070] A method for preparing a low-clinker composite mortar material using weathered granite construction slag comprises the following steps:

[0071] (1) The construction waste soil used was taken from a foundation pit soil of a road project in Conghua District, Guangzhou City, Guangdong Province. The XRD quantitative analysis results are as follows: kaolinite 50.3%, illite 3.3%, quartz 22.0%, feldspar 24.0%, and others 0.4%. The construction waste soil was placed in an oven and dried at 105°C for 24 hours and then crushed manually. It was then mixed with water and sodium hexametaphosphate in a mass ratio of 1000:5000:3 to fully disperse it and form a waste soil suspension. The suspension was passed through a 200-mesh sieve, and water was added, stirred, and sieved three times. All the liquid under the sieve and the coarse particles on the sieve were collected and dried separately to obtain powdery clay soil and coarse particles.

[0072] (2) The dried powdered clay was placed in a muffle furnace and calcined at 750 °C for 2 h. After cooling, it was added to a 0.2 mol / L CaCl2 solution and stirred evenly. Then, a 0.2 mol / L Na2CO3 solution was slowly added dropwise at 8 mL / min for 30 min. The entire reaction process was maintained at 400 rpm for 90 min. After the reaction was completed, the modified product was separated by centrifugation, washed with deionized water three times, and dried at 60 °C to obtain an activated powdered clay.

[0073] (3) The dried coarse particles were soaked in a 1 mol / L NaOH solution for 30 min, then washed with deionized water until neutral, added to a 0.1 mol / L CaCl2 solution, and 5 wt% water glass solution was slowly added at 3 mL / min for 30 min. The mixture was stirred at 200 rpm for 18 h at room temperature to complete the biomimetic mineralization treatment. The mineralized coarse particles were filtered or centrifuged, washed with deionized water three times, and dried at 60°C to obtain recycled fine aggregate.

[0074] (4) The recycled fine aggregate was screened by particle size and divided into three particle size ranges: A, B, and C. Group A particles: 0.15mm-0.25mm; Group B particles: 0.25mm-1mm; Group C particles: 1mm-4mm. The above three types of particles were mixed in different mass proportions to form the following three recycled fine aggregate grading combinations: ①A:B:C=2:1:1; ②A:B:C=1:2:1; ③A:B:C=1:1:2.

[0075] (5) 1589 g of active powdered clay, 795 g of limestone, 2913 g of Portland cement, and 1059 g of recycled fine aggregate (gradation combination ②) were placed in a mortar mixer and mixed evenly. 2.1 L of water was added and stirred rapidly to obtain a mortar mixture.

[0076] (6) Pour the obtained mortar mixture into a 70.7×70.7×70.7mm 3 The specimens were placed in a cubic mold and compacted on a cement mortar compaction table for 1 minute. The specimens were sealed with a film and naturally cured at room temperature for 24 hours before demoulding. The resulting specimens were named EM-CH. The specimens were cured at room temperature for 3 days, 7 days and 28 days to test their mechanical properties.

[0077] Example 4

[0078] A method for preparing a low-clinker composite mortar material using weathered granite construction slag comprises the following steps:

[0079] (1) The construction waste soil used was taken from the foundation pit soil of a tunnel project in Panyu District, Guangzhou City, Guangdong Province. The XRD quantitative analysis results are as follows: kaolinite 66.9%, illite 3.5%, quartz 18.0%, feldspar 10.0%, and others 1.6%. The construction waste soil was placed in an oven and dried at 105°C for 24 hours and then crushed manually. It was then mixed with water and sodium hexametaphosphate in a mass ratio of 1000:5000:3 to fully disperse it and form a waste soil suspension. The suspension was passed through a 200-mesh sieve, and water was added, stirred, and sieved repeatedly for 3 times. All the liquid under the sieve and the coarse particles on the sieve were collected and dried separately to obtain powdery clay soil and coarse particles.

[0080] (2) The dried powdered clay was placed in a muffle furnace and calcined at 750 °C for 2 h. After cooling, it was added to a 0.2 mol / L CaCl2 solution and stirred evenly. Then, a 0.2 mol / L Na2CO3 solution was slowly added dropwise at 8 mL / min for 30 min. The entire reaction process was maintained at 400 rpm for 90 min. After the reaction was completed, the modified product was separated by centrifugation, washed with deionized water three times, and dried at 60 °C to obtain an activated powdered clay.

[0081] (3) The dried coarse particles were soaked in a 1 mol / L NaOH solution for 30 min, then washed with deionized water until neutral, added to a 0.1 mol / L CaCl2 solution, and 5 wt% water glass solution was slowly added at 3 mL / min for 30 min. The mixture was stirred at 200 rpm for 18 h at room temperature to complete the biomimetic mineralization treatment. The mineralized coarse particles were filtered or centrifuged, washed with deionized water three times, and dried at 60°C to obtain recycled fine aggregate.

[0082] (4) The recycled fine aggregate was sieved according to particle size and divided into three particle size intervals: A, B, and C. Group A particles: 0.15mm-0.25mm; Group B particles: 0.25mm-1mm; Group C particles: 1mm-4mm. The above three types of particles were mixed in different mass proportions to form the following three recycled fine aggregate grading combinations: ①A:B:C=2:1:1; ②A:B:C=1:2:1; ③A:B:C=1:1:2.

[0083] (5) 2119 g of active powdered clay, 1059 g of limestone, 2119 g of Portland cement, and 795 g of recycled fine aggregate (gradation combination ③) were placed in a mortar mixer and mixed evenly. 2.1 L of water was added and stirred rapidly to obtain a mortar mixture.

[0084] (6) Pour the obtained mortar mixture into a 70.7×70.7×70.7mm 3 The specimens were placed in a cubic mold and compacted on a cement mortar compaction table for 1 minute. The specimens were sealed with a film and naturally cured at room temperature for 24 hours before demoulding. The resulting specimens were named EM-PY. The specimens were cured at room temperature for 3 days, 7 days, and 28 days to test their mechanical properties.

[0085] Comparative Example 1

[0086] (1) The Portland cement used in this comparative example is commercial OPC (PO42.5R), which complies with the Chinese standard GB175-2007;

[0087] (2) Place 5297 g of Portland cement and 1584 g of standard river sand in a cement slurry mixer, add 1.6 L of water and stir rapidly to obtain cement mortar;

[0088] (3) Pour the obtained mortar mixture into a 70.7×70.7×70.7mm 3 The specimens were placed in a cubic mold and compacted on a cement mortar compaction table for 1 minute. The specimens were sealed with a film and naturally cured at room temperature for 24 hours before demoulding. The resulting specimens were named OPC. The specimens were cured at room temperature for 3 days, 7 days and 28 days to test their mechanical properties.

[0089] Comparative Example 2

[0090] (1) The fly ash used in this comparative example is Class II fly ash, which complies with the Chinese standard GB / T1596-2017, and the Portland cement is commercial OPC (PO 42.5R), which complies with the Chinese standard GB175-2007;

[0091] (2) 1584 g of fly ash, 3708 g of Portland cement, and 1584 g of standard river sand were placed in a mortar mixer and mixed evenly. 1.6 L of water was added and stirred rapidly to obtain a mortar mixture:

[0092] (3) Pour the obtained mortar mixture into a 70.7×70.7×70.7mm 3 The specimens were placed in a cubic mold and compacted on a cement mortar compaction table for 1 minute. The specimens were sealed with a film and naturally cured at room temperature for 24 hours before demoulding. The resulting specimens were named FA-OPC. The specimens were cured at room temperature for 3 days, 7 days and 28 days to test their mechanical properties.

[0093] Comparative Example 3

[0094] (1) The construction waste soil used in this comparative example was taken from the foundation pit soil of a structure project in Longhua District, Shenzhen City, Guangdong Province. The construction waste soil was placed in an oven and dried at 105°C for 24 hours, then crushed and used directly as a replacement material without sedimentation, screening, heat treatment or biomimetic mineralization modification;

[0095] (2) 530 g of untreated slag powder, 265 g of limestone, 4503 g of Portland cement, and 1584 g of standard river sand were placed in a mortar mixer and mixed evenly. 1.6 L of water was added and stirred rapidly to obtain a mortar mixture.

[0096] (3) Pour the obtained mortar mixture into a 70.7×70.7×70.7mm 3 The test blocks were placed in a cubic mold and compacted on a cement mortar compaction table for 1 minute. The blocks were sealed with a film and naturally cured at room temperature for 24 hours before demoulding. The resulting test blocks were named UC-SZ. The test blocks were cured at room temperature for 3 days, 7 days and 28 days to test their mechanical properties.

[0097] According to the provisions of JGJ / T70-2009 "Test Method for Basic Properties of Building Mortar", the compressive strength of the mortar test blocks prepared in Examples 1-4 and Comparative Examples 1-3 was measured using a universal testing machine. The results are shown in Table 1 below.

[0098] Table 1

[0099]

[0100] From the attached Figure 1The XRD pattern of the silty clay after heat treatment and biomimetic mineralization modification shows that the Ca 2+ and CO3 2- A nano-calcium carbonate deposition layer is formed on the surface of the silty clay soil, and the characteristic peaks of calcite can be clearly observed in XRD.

[0101] From the attached Figure 2 From the TG-DSC curve of the medium-coarse particles modified by biomimetic mineralization, it can be seen that there are obvious weight loss and endothermic peaks at 25℃~220℃, which correspond to the removal of physically adsorbed water and chemically bound water in the CSH gel, indicating that nano-CSH gel is deposited on the surface of the coarse particles during the biomimetic mineralization process.

[0102] The above is a detailed introduction to the method and mortar provided by the present invention for preparing low-clinker composite mortar materials using weathered granite construction project debris. Specific examples are used herein to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core ideas, including the best mode, and also enables any technician in this field to practice the present invention, including the manufacture and use of any device or system, and the implementation of any combined method.

[0103] It should be noted that those skilled in the art will readily appreciate that various improvements and modifications may be made to the present invention without departing from the principles of the present invention. In particular, as long as no structural conflicts exist, the various features of the embodiments disclosed herein may be combined with one another in any manner. The omission of an exhaustive description of these combinations in this specification is solely for the sake of space and resource conservation. Therefore, the present invention is not limited to the specific embodiments disclosed herein, but encompasses all technical solutions within the scope of the claims.

Claims

1. A method for preparing low-clinker composite mortar material using granite weathered construction engineering slag, characterized in that: The following steps are involved: 1) Settle and screen the construction waste soil to obtain powdery clay soil and coarse particles; 2) heat-treating the powdered clay soil and then subjecting it to biomimetic mineralization modification to obtain active powdered clay soil; 3) After biomimetic mineralization modification of the coarse particles, the particle size is adjusted to obtain a gradation combination of recycled fine aggregate; 4) Mixing active powdered clay soil, limestone, cement clinker, water and recycled fine aggregate in a certain proportion to obtain a mixed mortar; The construction slag in step (1) is granite weathered construction slag, and the kaolinite content of the construction slag is 10% to 75%, the illite content is 3% to 30%, the quartz content is 15% to 50%, and the feldspar content is 3% to 30%.

2. The method for preparing low-clinker composite mortar material using granite weathered construction engineering debris according to claim 1, characterized in that: In step (1), the construction waste soil is subjected to sedimentation and screening treatment, which includes the following steps: The construction waste soil is crushed, mixed with water, and a dispersant is added to obtain a construction waste soil suspension; The engineering waste soil suspension is sieved to obtain the undersize liquid and the coarse particles on the sieve; The liquid under the sieve and the coarse particles on the sieve are dried to obtain powdery clay soil and coarse particles.

3. The method for preparing low-clinker composite mortar material using granite weathered construction engineering debris according to claim 2, characterized in that: The dispersant is sodium hexametaphosphate.

4. The method for preparing low-clinker composite mortar material using granite weathered construction engineering debris according to claim 2, characterized in that: The construction waste soil, water and dispersant are mixed in a mass ratio of 1000:4000-6000:2-5 to obtain a construction waste soil suspension, and the construction waste soil suspension is passed through a 150-250 mesh sieve.

5. The method for preparing low-clinker composite mortar material using granite weathered construction engineering debris according to claim 1, characterized in that: In step (2), when the powdered clay soil is heat-treated, the temperature is set to 550-850° C. and the time is set to 1.5-2.5 hours.

6. The method for preparing low-clinker composite mortar material using granite weathered construction engineering debris according to claim 1, characterized in that: In step (2), the biomimetic mineralization modification of powdered clay soil comprises the following steps: The heat-treated powdered clay soil is added to a 0.1-0.5 mol / L CaCl2 solution, and stirred continuously. A 0.1-0.5 mol / L Na2CO3 solution is added dropwise at a rate of 6-12 mL / min for 20-40 min. The entire powdered clay soil biomimetic mineralization modification process is stirred for 60-90 min to obtain a modified product. The modified product is separated into solid and liquid, washed with deionized water, and dried at 50-70 DEG C to obtain powdered clay soil modified by biomimetic mineralization.

7. The method for preparing low-clinker composite mortar material using granite weathered construction engineering debris according to claim 1, characterized in that: In step (3), the biomimetic mineralization modification of the coarse particles comprises the following steps: The coarse particles are immersed in a 0.5-2 mol / L NaOH solution for 15-45 minutes, and then washed with deionized water until neutral to obtain alkali-treated coarse particles; The alkali-treated coarse particles are added to a 0.05-0.2 mol / L CaCl2 solution, and a 4-6 wt% water glass solution is added dropwise at a rate of 3-6 mL / min for 15-30 min. The mixture is stirred and reacted at room temperature for 12-24 h to complete the biomimetic mineralization treatment; The mineralized coarse particles are separated into solid and liquid, washed with deionized water, and dried at 50-70° C. to obtain biomimetic mineralized modified coarse particles.

8. The method for preparing low-clinker composite mortar material using granite weathered construction engineering debris according to claim 1, characterized in that: In step (3), the modified coarse particles are graded according to particle size and mixed according to mass ratio to form different recycled fine aggregate gradations, including the following combinations: components with particle sizes between 0.15 mm and 0.25 mm, 0.25 mm and 1 mm and 4 mm are mixed in a mass ratio of 2:1:1, 1:2:1 or 1:1:

2.

9. The method for preparing low-clinker composite mortar material using granite weathered construction engineering debris according to claim 1, characterized in that: In step (4), the raw materials for preparing the composite cement material include, by mass percentage, 10% to 40% of active powdered clay, 5% to 20% of limestone, 40% to 85% of cement clinker, and 10% to 40% of recycled fine aggregate.

10. A composite mortar, characterized in that: The method is prepared by any one of claims 1 to 9.

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