Low-carbon recycled mortar and preparation process thereof

Abstract

The invention relates to the field of building materials, and discloses low-carbon recycled mortar, which comprises the following component materials: 400-500 parts of low-carbon cement; 100 parts to 150 parts of superfine silica fume; 200 to 300 parts of superfine slag powder; 200 to 300 parts of modified recycled aggregate; 20 to 30 parts of a hydration reaction regulating agent; 20 to 30 parts of a surface modifier; the low-carbon cement is prepared from the following components in parts by weight: 350 to 450 parts of Portland cement, 50 to 60 parts of industrial byproduct powder and 50 to 60 parts of superfine quartz powder. The recycled aggregate is subjected to sand blasting, drying and soaking modification treatment, so that a roughened structure is formed on the surface of the recycled aggregate, the activity is enhanced, the binding force of the aggregate and a cement matrix is improved, the stress transfer effect is improved, the overall strength of the mortar is improved, the durability is enhanced, and the long-term use performance is more stable.

Description

Technical Field

[0001] The present invention relates to the technical field of building materials, in particular to low-carbon regenerated mortar and a preparation process thereof. Background Art

[0002] Low-carbon recycled mortar is an environmentally friendly building material. By reducing the use of traditional cement, employing recycled aggregates, and optimizing hydration reaction control, it achieves low carbon emissions while maintaining mortar performance. This mortar reduces the consumption of natural resources and cement clinker during production, and utilizes construction waste or industrial by-products as raw materials, contributing to the sustainable development goals of the construction industry.

[0003] Existing low-carbon recycled mortar preparation methods include a variety of approaches. One approach involves partially replacing cement with industrial byproducts such as slag powder and fly ash to reduce cement usage. However, due to the low reactivity of these industrial admixtures, their hydration reaction rate is slow, resulting in insufficient early strength in the mortar, limiting its practical application. A second approach involves using chemical admixtures, such as water reducers and coagulants, to adjust the hydration process. However, existing hydration control methods struggle to precisely control the hydration process, leading to low early strength and later strength degradation in practical applications. A third approach involves partially replacing natural aggregate with recycled aggregate to reduce reliance on natural sand and gravel. However, the presence of cement paste residue and high porosity in conventional recycled aggregates results in poor adhesion to the cement matrix, impacting the mortar's mechanical properties and durability. Traditional recycled aggregate modification methods, such as acid washing and alkaline treatment, suffer from low processing efficiency, high costs, and potential environmental pollution. Therefore, current low-carbon mortar technology still faces numerous limitations, making it difficult to balance environmental friendliness with optimized material properties. Summary of the Invention

[0004] In response to the shortcomings of the existing technology, the present invention provides a low-carbon recycled mortar and a preparation process thereof, which solves the problems of high carbon emissions, waste of natural resources and poor bonding strength of recycled aggregates in traditional mortar production.

[0005] To achieve the above objectives, the present invention is implemented through the following technical solutions: low-carbon regenerated mortar, including the following component materials: 400-500 parts of low carbon cement; 100-150 parts of ultrafine silica fume; 200-300 parts of slag powder; 200-300 parts of modified recycled aggregate; 20-30 parts of hydration reaction regulator; 20-30 parts of surface modifier.

[0006] Preferably, the low carbon cement is composed of Portland cement, industrial by-product powder and ultrafine quartz powder, and includes, by weight: 350-450 parts of Portland cement; 30-80 parts of industrial by-product powder; 20-60 parts of ultrafine quartz powder.

[0007] Preferably, the industrial by-product powder is selected from one or more combinations of construction waste recycled fine powder, steel slag powder, fly ash or silicon manganese slag powder.

[0008] Preferably, the specific surface area of ​​the ultrafine quartz powder is not less than 400m 2 / kg, and can react with cement hydration products during the hydration process to form a hydraulic gel structure.

[0009] Preferably, the modified recycled aggregate is processed by the following steps: Use aggregate with a particle size range of 0.5mm-5mm; Perform sandblasting with a sandblasting particle size of 50-100 μm and a sandblasting time of 10-20 minutes; Drying is carried out in an environment of 60-80℃ for 1-2 hours; Soak in a surface modifier solution with a concentration of 1%-3% for 30 minutes.

[0010] Preferably, the hydration reaction regulator is selected from one or more combinations of dihydrate gypsum, calcium carbonate, sodium silicate, and metakaolin; The surface modifier is selected from one or more combinations of 3-aminopropyltriethoxysilane, polycarboxylic acid water reducer, organic silicon emulsion, and titanate coupling agent.

[0011] A method for preparing low-carbon regenerated mortar comprises the following steps: S1: Mix low carbon cement, ultrafine silica fume and slag powder in proportion to form a uniform powder; S2: adding the modified recycled aggregate to the mixture obtained in step S1 and performing dry mixing; S3: adding hydration reaction regulator and surface modifier and continuing dry mixing; S4: Pack the evenly mixed dry powder to obtain a low-carbon recycled mortar product.

[0012] Preferably, the dry mixing process in step S2 includes: a. Use a mechanical mixer for dry mixing, control the speed at 60-120r / min, and the mixing time is 40-70 seconds; b. Use air flow conveying device for dynamic mixing to make the components evenly dispersed.

[0013] Preferably, the packaging method in step S4 includes: a. Use sealed bag packaging; b. Use vacuum packaging.

[0014] The present invention provides low-carbon regenerated mortar and its preparation process, which has the following beneficial effects: 1. The present invention modifies the recycled aggregate by sandblasting, drying, and soaking it to form a roughened structure on its surface and enhance its activity, thereby improving the bonding strength between the aggregate and the cement matrix. This modified aggregate is evenly distributed within the mortar, reducing the generation of microcracks at the interface, improving the stress transfer effect, and achieving an overall increase in the mortar's strength, enhanced durability, and more stable long-term performance.

[0015] 2. The present invention introduces a hydration reaction regulator to precisely control the hydration rate of cement, thereby avoiding internal stress concentration caused by excessively rapid hydration in the early stage. The hydration process is more uniform, promoting the formation of CSH gel, and improving the density of the matrix. The mortar exhibits excellent strength growth characteristics at different ages, avoiding early cracking, while ensuring stable mechanical properties in the later stage, thereby ensuring construction quality and structural reliability.

[0016] 3. This invention partially replaces Portland cement with industrial byproducts such as fly ash and steel slag powder, enabling the resource utilization of solid waste and reducing carbon dioxide emissions during cement production. This improves material utilization, significantly reduces the carbon footprint, and optimizes the hydration environment of the mortar, ensuring that mechanical properties are not affected. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a schematic diagram of the process flow of the present invention. DETAILED DESCRIPTION

[0018] The following will clearly and completely describe the technical solution of the present invention in conjunction with the accompanying drawings. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0019] Please see the attached Figure 1 The present invention provides a method for preparing low-carbon regenerated mortar, comprising the following steps: S1: Mix low carbon cement, ultrafine silica fume and slag powder in proportion to form a uniform powder; S2: adding the modified recycled aggregate to the mixture obtained in step S1 for dry mixing; comprising: a. Use a mechanical mixer for dry mixing, control the speed at 60-120r / min, and the mixing time is 40-70 seconds; b. Use air flow conveying device for dynamic mixing to make the components evenly dispersed.

[0020] S3: adding a hydration reaction regulator and a surface modifier, and continuing dry mixing; the hydration reaction regulator and the surface modifier are added as follows: S31. Before premixing low carbon cement with ultrafine silica fume and slag powder, evenly disperse the hydration reaction regulator; S32. After the sandblasting treatment of the modified recycled aggregate is completed, the surface modifier is evenly applied by spraying to allow it to be fully adsorbed, and then mixed with other materials after drying.

[0021] S4: Packing the evenly mixed dry powder to obtain the finished low-carbon recycled mortar, including: a. Use sealed bag packaging; b. Use vacuum packaging.

[0022] Specifically, during the raw material preparation stage, low-carbon cement, ultrafine silica fume, and slag powder are precisely weighed and evenly mixed in proportion. Low-carbon cement reduces the proportion of clinker in traditional cement and replaces it with industrial by-products such as slag and fly ash, thereby reducing carbon dioxide emissions during the cement production process and improving the long-term stability and compressive strength of the mortar. Ultrafine silica fume, as a highly active admixture, can fill the voids in the cement matrix, further improving the density and impermeability of the mortar, and effectively reducing the amount of cement used, thereby further reducing carbon emissions. Slag powder improves the microstructure of the cement matrix, which not only helps to reduce the carbon footprint of the mortar, but also increases its strength. In this process, the raw materials are rationally proportioned and mixed to ensure the uniform dispersion of each component, laying a solid foundation for subsequent dry mixing and hydration reactions.

[0023] The selection and treatment of modified recycled aggregates are key links in this method. By recycling discarded building materials or old concrete, not only can resources be effectively recycled and construction waste reduced, but the carbon footprint of raw materials can also be significantly reduced. During the treatment process, impurities on the surface of the aggregate are first removed by physical methods such as sandblasting to clean up pollutants that may affect the performance of the mortar. Then, the modified recycled aggregate is mixed with materials such as low-carbon cement, slag powder and ultrafine silica fume, and evenly dry-mixed using a mechanical mixer. During the mixing process, the mixer speed is controlled between 60-120 rpm and the mixing time is 40-70 seconds to ensure that the components are fully combined and avoid uneven dispersion. In addition, the use of an airflow conveying device for dynamic mixing can effectively avoid the precipitation of large particles and ensure the uniform dispersion of all components, thereby improving the stability and performance of the mortar.

[0024] The addition of a hydration reaction regulator and a surface modifier significantly improves the performance of the mortar. The hydration reaction regulator is evenly dispersed in the low-carbon cement before it is mixed with other materials, effectively regulating the rate of cement hydration during the initial hydration phase. This not only prolongs the initial setting time but also ensures that the cement particles fully react with water, thereby enhancing the mortar's strength development and durability. The surface modifier is evenly applied to the surface of the modified recycled aggregate via spraying, increasing the aggregate's surface affinity and optimizing the bond between the aggregate and the cement matrix. This treatment not only improves the mortar's impermeability but also enhances its strength. The surface modifier is evenly adsorbed during the spraying and drying process, avoiding performance issues caused by inadequate surface treatment. This ensures the mortar's ultimate superior performance and provides reliable support for subsequent packaging and application.

[0025] The fully mixed mortar is finally packaged in a vacuum or sealed bag to ensure it is not affected by the external environment during storage and transportation. Sealed bag packaging can effectively block moisture from the air, preventing the mortar from absorbing moisture or clumping, and ensuring its stable performance during long-term storage. For moisture-sensitive mortar, vacuum packaging can more effectively isolate moisture and air, preventing oxidation reactions or moisture intrusion that could lead to performance degradation. Vacuum packaging can extend the shelf life of the mortar, ensuring it can still perform at its best during construction. During the packaging process, automated equipment is used to ensure that the packaging is tightly sealed to avoid quality changes during transportation. After packaging, the mortar should be stored in a dry, ventilated environment to avoid the effects of high humidity or extreme climatic conditions on the mortar's performance, thereby ensuring the long-term stability of its physical and chemical properties.

[0026] The following examples are given based on the above preparation method: Example 1: Modified recycled aggregate treatment and mortar preparation: Step 1: Material Selection Select recycled aggregate with a particle size of 0.5mm-5mm, screen and wash it to ensure there are no large impurities.

[0027] Step 2: Sandblasting The aggregate is sandblasted with a particle size of 50-100 μm for 15 minutes. The purpose of sandblasting is to increase the surface roughness of the aggregate and remove surface impurities.

[0028] Step 3: Drying The sandblasted aggregate was placed in an oven and dried at 70°C for 1.5 hours to ensure that there was no moisture remaining on the surface of the aggregate.

[0029] Step 4: Surface modification Prepare a 2% 3-aminopropyltriethoxysilane solution and soak the dried aggregate in it for 30 minutes to allow it to evenly absorb the modifier. After soaking, remove the aggregate and let it sit for 12 hours to dry naturally.

[0030] Step 5: Mortar preparation Modified aggregate, ultrafine quartz powder (specific surface area 400m 2 / kg), fly ash, slag powder, and low-carbon cement are mixed in a weight ratio of 2:1:0.8:0.8:1. Add an appropriate amount of water and use a mechanical stirrer to stir for 5 minutes to ensure uniformity.

[0031] Step 6: Maintenance After the mortar is mixed, it is poured into the mold and cured at room temperature for 28 days, and then the compressive strength test is carried out.

[0032] Example 2: Preparation of composite mortar made of low-carbon cement and industrial by-products: Step 1: Prepare the ingredients Take low carbon cement, ultrafine silica fume, steel slag powder, fly ash, etc., and control the cement density at 300kg / m 3 Steel slag powder and fly ash account for 10% and 15% of the total cement volume respectively.

[0033] Step 2: Adding hydration reaction regulator Add 3% of the total cement content to dihydrate gypsum and mix well. Dihydrate gypsum is mainly used to control the hydration reaction rate of cement and prevent it from hydrating too quickly.

[0034] Step 3: Mixing Mix low-carbon cement, ultrafine silica fume, steel slag powder, fly ash, and dihydrate gypsum according to the appropriate proportions. Add water at a rate of 0.4-0.45 times the mass of cement to ensure good mortar fluidity.

[0035] Step 4: Mixing mortar Use a blender to blend the mixture for 5-8 minutes to ensure all ingredients are evenly distributed.

[0036] Step 5: Maintenance and performance testing The mortar was poured into the mold and cured at room temperature for 28 days to test its compressive strength, flexural strength and water resistance.

[0037] Example 3: Preparation and application of green and environmentally friendly mortar: Step 1: Prepare the modifier A 2% titanate coupling agent solution was prepared to treat the surface of the recycled aggregate and enhance the interfacial bonding between the aggregate and the cement matrix.

[0038] Step 2: Modified recycled aggregate processing Select recycled aggregates with a size of 0.5mm to 5mm and sandblast them with 50μm sand for 12 minutes. Then, soak the aggregates in a titanate coupling agent solution for 20 minutes to ensure uniform coverage.

[0039] Step 3: Mortar ingredients Mix modified aggregate, ultrafine quartz powder, slag powder and low carbon cement in a weight ratio of 3:1:1:1, add 1.5% polycarboxylate water reducer, and adjust the water-cement ratio to 0.35 to ensure that the mortar has good fluidity.

[0040] Step 4: Mixing and stirring Use a high-efficiency mixer to mix all materials evenly to ensure that the mortar is free of lumps and has good workability.

[0041] Step 5: Pouring and curing The mixed mortar is poured into the precast component mold and cured at room temperature for 28 days. During the curing process, the compressive strength, water resistance and frost resistance of the mortar are regularly tested.

[0042] Example 4: Preparation of high-efficiency hydration-controlled mortar: Step 1: Raw material selection Select low-carbon cement and ultrafine quartz powder that meet the standards and mix them in a ratio of 1:2. Add 1% sodium silicate to promote the formation of CSH gel during cement hydration.

[0043] Step 2: Adding regulator Adding metakaolin at 2% of the weight of cement can improve the performance of the gelling material generated during the cement hydration process and enhance the later strength of the mortar.

[0044] Step 3: Stir to mix Mix low carbon cement, ultrafine quartz powder, sodium silicate, and metakaolin, and add an appropriate amount of water to keep the water-cement ratio of the mixture at 0.38. Mix and stir for 5 minutes to ensure full uniformity.

[0045] Step 4: Forming and maintenance Pour the mixed mortar into the mold and cure it at room temperature for 28 days. During the curing period, perform compressive strength and water resistance tests regularly.

[0046] Comparative Example 1: Preparation of unmodified recycled aggregate mortar: Comparative Example: Example 1 (Modified Recycled Aggregate Treatment and Mortar Preparation) Comparative design: No sandblasting, drying or surface modifier soaking of the recycled aggregate is performed, and only recycled aggregate after ordinary cleaning is used.

[0047] Preparation process: Raw material selection: Select recycled aggregate with a particle size of 0.5mm-5mm and perform simple water washing to remove mud and sand impurities.

[0048] Mortar preparation: recycled aggregate without surface modification, ultrafine quartz powder (specific surface area 400m 2 / kg), slag powder and low carbon cement are mixed in the ratio of (2:1:0.8:0.8:1).

[0049] Hydration regulator: No hydration regulator was added, and the water-binder ratio was kept consistent with that in Example 1.

[0050] Stirring and curing: The same stirring method and curing conditions as in Example 1 were used for the treatment.

[0051] Comparative Example 2: Low carbon cement mortar without hydration reaction regulator: Comparative Example: Example 2 (Preparation of Composite Mortar of Low-Carbon Cement and Industrial By-products) Comparative design: No hydration reaction regulator (such as dihydrate gypsum) is added, and only low-carbon cement is mixed with industrial by-product powder.

[0052] Preparation process: Raw material selection: low carbon cement, ultrafine silica fume, steel slag powder, fly ash, cement density controlled at 300kg / m 3 .

[0053] Mixing ratio: dry mix according to the ratio (low carbon cement: steel slag powder: fly ash = 1:0.1:0.15).

[0054] Hydration regulator: Omit the addition of hydration regulator and do not add dihydrate gypsum.

[0055] Water-cement ratio: Keep the water-cement ratio consistent with Example 2.

[0056] Mixing and curing: The mixture was stirred using a mixer as in Example 2 and cured for 28 days.

[0057] Comparative Example 3: Mortar without polycarboxylate water reducer: Comparative Example: Example 3 (Preparation and Application of Green and Environmentally Friendly Mortar) Comparative design: No polycarboxylate water reducer is used, and only the water-binder ratio is adjusted to improve fluidity.

[0058] Preparation process: Raw material selection: Select modified recycled aggregate, ultrafine quartz powder, low carbon cement, fly ash, etc., and mix them according to the ratio (2:1:0.8:0.8).

[0059] Surface modification: As in Example 3, the recycled aggregate was modified using a titanate coupling agent.

[0060] Adjustment of water-binder ratio: without using polycarboxylate water-reducing agent, adjust the water-binder ratio to 0.38 and keep the fluidity equivalent to that of Example 3.

[0061] Stir and Mix: Blend in a blender for 5 minutes to ensure even mixing.

[0062] Curing: Use the same curing conditions and carry out curing at room temperature for 28 days.

[0063] Comparative Example 4: Low-carbon mortar without ultrafine quartz powder: Comparative Example: Example 4 (Preparation of High-Efficiency Hydration Control Mortar) Comparative design: No ultrafine quartz powder is used, the addition of mineral components is reduced, and only low-carbon cement and industrial by-product powder are used.

[0064] Raw material selection: low carbon cement, fly ash, steel slag powder, slag powder, etc., the cement density is controlled at 300kg / m 3 .

[0065] Hydration reaction control: Metakaolin was added as a control agent, and the proportion of the hydration control agent was the same as that in Example 4.

[0066] Mortar ratio: Do ​​not use ultrafine quartz powder, only mix fly ash and slag powder in proportion, and adjust the water-binder ratio to 0.36.

[0067] Mixing: Dry mix according to the above proportions and use a blender to mix for 5 minutes to ensure uniform mixing.

[0068] Maintenance: Maintain at room temperature for 28 days.

[0069] Experiment 1: Mortar compressive strength test: The purpose of this experiment is to verify the effect of additives such as modified aggregate and hydration reaction regulator on improving the mortar strength in the scheme of the present invention by comparing the compressive strength of different mortar ratios.

[0070] Preparation: Select the mortar formulas of Example 1, Example 2, Example 3, Comparative Example 1 and Comparative Example 2. All samples are mixed according to the same water-binder ratio (0.38).

[0071] Batching and Mixing: Choose between different recycled aggregate treatments (unmodified, sandblasted, and surface-modified) and different cement substitute ratios (such as slag powder and fly ash). Weigh the required raw materials according to the preset ratios. Use a standard mortar mixer to mix all ingredients for 5 minutes to ensure a uniform mortar.

[0072] Mold pouring: Pour the mixed mortar into a standard mold (10 cm x 10 cm x 10 cm). Ensure that the amount of mortar is consistent for each group. Prepare at least three samples for each experimental group.

[0073] Curing Conditions: After mold casting, perform room temperature curing for 28 days. Keep samples moist during curing to prevent cracking. Compressive Strength Test: After 28 days of curing, perform compressive strength testing using a pressure testing machine. Perform three tests per group, and take the average value as the compressive strength of that group.

[0074] Mortar compressive strength test results table: Experimental group Sample 1 (MPa) Sample 2 (MPa) Sample 3 (MPa) Average value (MPa) Example 1 35.2 38.7 36.1 36.7 Example 2 29.3 30.4 28.1 29.3 Example 3 34.0 33.2 32.8 33.3 Comparative Example 1 25.6 24.8 26.1 25.5 Comparative Example 2 22.0 23.2 21.9 22.3 The experimental data shows that the mortar in Example 1 has significantly higher compressive strength, with an average value of 36.7 MPa, significantly outperforming Comparative Examples 1 and 2. This is primarily due to the use of recycled aggregate in Example 1 that has been sandblasted and surface-modified. This effectively improves the surface roughness and reactivity of the aggregate, strengthens the bond between the aggregate and the cement matrix, and reduces the occurrence of interfacial microcracks. This surface modification effectively increases the compressive strength of the mortar and makes the overall structure more stable.

[0075] In contrast, the compressive strength of Comparative Example 1 was significantly lower than that of Example 1, indicating that the unmodified recycled aggregate performed far worse in the cement matrix than the treated aggregate. This also highlights the innovative nature of the present invention in improving the mechanical properties of the mortar. By improving the surface structure of the aggregate, not only is the strength increased, but also the durability during long-term use.

[0076] From the perspective of hydration reaction, the hydration control agent (such as dihydrate gypsum) added in Example 1 works synergistically with the ultrafine quartz powder to optimize the hydration process of cement. The high specific surface area of ​​the ultrafine quartz powder enables it to react with cement hydration products, further enhancing the strength of the mortar. In contrast, the mortar of Comparative Example 2 does not use a hydration control agent, and the hydration rate of the cement is too fast or too slow, resulting in uneven strength development and a lower compressive strength. This once again proves that the present invention can effectively improve the strength of the mortar by precisely controlling the cement hydration process.

[0077] Experiment 2: Mortar flexural strength and workability test: This experiment primarily tests the flexural strength and fluidity of mortar. Flexural strength reflects a material's ability to resist fracture under bending loads and directly impacts the integrity of the structure. Fluidity determines the ease of mortar construction; too low a fluidity can make construction difficult, while too high a fluidity can cause segregation. The experiment focused on the effects of modified recycled aggregate and polycarboxylate superplasticizer.

[0078] Sample Preparation: The mortar formulations for Example 1, Example 3, Comparative Example 1, and Comparative Example 3 were prepared, and raw materials were weighed according to the respective ratios. The water-binder ratio of the mortars was set at 0.35 to ensure comparability between the different formulations. The processing of the recycled aggregates was determined according to the respective protocols, including whether sandblasting, drying, and modifier treatment were performed.

[0079] Mixing and fluidity testing: Pour the mortar into a mixer and set the mixing time to 5 minutes to ensure uniform mixing. Immediately after mixing, perform a fluidity test. Pour the mortar into a standard fluidity tester (a truncated cone mold). Gently lift the mold to allow the mortar to expand freely. Record the diameter of the mortar expansion. Measure three times and take the average value.

[0080] Flexural Strength Test: Pour the mortar into a 40mm x 40mm x 160mm test mold and compact it using a vibration table to ensure that there are no bubbles or voids inside the specimen. Cure the specimen for 28 days at 20°C ± 2°C, with humidity maintained above 95%. After curing, load the specimen using a three-point flexural testing machine at a loading rate of 50N / s. Record the maximum failure load and calculate the flexural strength.

[0081] Mortar flexural strength and fluidity test results table: The improved fluidity of the mortar means that the construction process is smoother, easier to pour, and more filling. Example 3 has the highest fluidity, reaching 180mm, while Comparative Example 3 has the lowest, only 132mm. The addition of polycarboxylic acid water-reducing agent significantly improves the dispersibility of the mortar particles, reduces the cohesive force, and thus improves the fluidity. This change directly affects the convenience of construction and also avoids the decrease in strength caused by the addition of too much water. In contrast, the mortar of Comparative Example 3, which does not use a water-reducing agent, is viscous, has a large stirring resistance, and the test mold is unevenly filled, which is very easy to segregate.

[0082] The difference in flexural strength is also obvious. The mortar in Example 1 has the highest flexural strength, with an average of 6.3 MPa, while that in Comparative Example 1 is significantly lower, at only 4.7 MPa. The main reason for this is that the aggregate that has not been sandblasted and modified has more smooth or contaminated layers on the surface, which affects the bonding with the cement matrix. The increase in weak interface areas causes stress concentration when subjected to force, leading to earlier failure. The modified aggregate forms a more uniform bonding interface with the cement slurry, and the force transmission is smoother, so the flexural strength is stronger.

[0083] Simply improving fluidity does not fully guarantee optimized mechanical properties. The flexural strength of Example 3 is lower than that of Example 1, indicating that while the introduction of a polycarboxylate superplasticizer improves workability, it must be combined with surface modification of the aggregate to achieve its maximum effect. Even if the mortar with unmodified aggregate meets the required fluidity requirements, it still exhibits significant interfacial defects. During the hydration process, the bond between the aggregate and the matrix is ​​insufficient, making the final mortar susceptible to cracking along the interface and reducing its flexural strength.

[0084] Experiment 3: Mortar water resistance test: This experiment primarily examines the changes in mass and compressive strength of mortars with different formulations when immersed in water. Water resistance determines the stability of mortar in humid environments and directly affects its long-term service life. This experiment focuses on the effects of hydration regulators and ultrafine quartz powder on water resistance.

[0085] Sample Preparation: Select the mortar formulas from Example 2, Example 4, Comparative Example 2, and Comparative Example 4, and weigh the raw materials according to their respective proportions. The mortar water-binder ratio was uniformly set at 0.36 to ensure comparability of experimental data. Pour the mortar into a standard 5 cm × 5 cm × 10 cm mold, and prepare six samples per group.

[0086] Initial curing: After the specimen is formed, perform standard wet curing for 7 days at 20℃±2℃ and maintain humidity at 95%. After curing, weigh the initial mass of the specimen and record the value.

[0087] Water immersion test: The specimens were completely immersed in clean water at 20°C, covering the specimens to a depth of at least 5cm. The specimens were removed every 24 hours, their surfaces wiped dry, and their mass measured for changes. The data were continuously monitored for seven days, with the data recorded. After the seventh day, the specimens were removed and subjected to a compressive strength test. Three measurements were taken for each group, and the average value was calculated.

[0088] Mortar water resistance test results table: After 7 days of water immersion, the mass change in Examples 2 and 4 was minimal, remaining at around 0.4%, while Comparative Examples 2 and 4 showed significant water absorption, reaching up to 2.7%. This means that formulations without hydration reaction regulators or ultrafine quartz powder are more susceptible to water absorption and expansion after water immersion, resulting in volume changes. Mortars with such high water absorption can develop microcracks at the interface due to volume expansion in a humid environment for a long time, thus affecting the overall structural stability. The role of ultrafine quartz powder cannot be ignored. It reacts with cement hydration products to form a denser CSH gel, which effectively creates an additional "waterproof layer" within the mortar, reducing the possibility of water intrusion.

[0089] The downward trend of compressive strength is also obvious. Comparative Example 4 shows the most serious decline, with the strength remaining at only 21.7 MPa after the hydration structure is damaged. In contrast, the strength of the mortar in Example 4 after water immersion is still maintained at above 30 MPa. The addition of a hydration reaction regulator plays a key role here. It regulates the hydration rate of the cement, making the early hydration structure more uniform, thereby maintaining high strength in a long-term water immersion environment. In contrast, in Comparative Example 2, because no hydration regulator was added, the hydration reaction was already too fast or too slow in the early stage, resulting in an uneven internal cement matrix, increased porosity, and easier softening and damage after water ingress, which ultimately led to a significant decrease in strength.

[0090] For mortars exposed to long-term humidity, simply improving early strength is insufficient; durability is crucial. Examples 2 and 4 demonstrate that the synergistic effect of a hydration reaction regulator and ultrafine quartz powder effectively reduces water erosion and improves structural stability. However, the experimental results of Comparative Example 4 further confirm that mortars without these materials are easily penetrated and decomposed by water, resulting in significant strength loss. This gap cannot be remedied in the short term; ultimate durability is determined from the very beginning of the hydration reaction.

[0091] Experiment 4: Carbon Emission Analysis: This experiment primarily measured the carbon emissions generated during the production of mortars with different formulations, analyzing the present invention's contribution to reducing carbon footprint. Cement is a major carbon emitter, but this invention reduces carbon emissions per unit strength by partially replacing cement with industrial byproducts and optimizing the hydration reaction. This experiment focused on the impact of cement content on carbon emissions and compared emissions from different formulations.

[0092] Calculate the amount of cement used: Select the formulas of Example 2, Example 3, Comparative Example 1, and Comparative Example 4. Record the amount of cement, slag powder, fly ash, and other materials used in each group, and calculate the cement replacement rate.

[0093] Calculation of carbon emissions: Using public data, each ton of cement emits approximately 800-900kg CO2.

[0094] Based on the cement usage, the carbon emissions per unit mass during the production of each group of mortar were calculated.

[0095] Carbon emissions per unit strength: Based on the compressive strength data from Experiment 1, calculate the carbon emissions per MPa of mortar (kgCO2 / MPa). This indicator can directly reflect the carbon emission efficiency rather than simply an absolute value.

[0096] Mortar carbon emission test results table: It seems easy to understand that reducing cement consumption leads to lower carbon emissions. However, there is another logic hidden in the data.3 , the carbon emission per unit strength is as high as 10.0kgCO2 / MPa, while the amount of cement in Example 3 is reduced to 200kg / m 3 , carbon emissions per unit strength dropped to 4.8kgCO2 / MPa. This means that this invention not only reduces cement but also utilizes cement more efficiently, improving the carbon emission efficiency of the material. Cement is the primary source of strength, and using less of it can still improve strength. This indicates that the hydration environment has been optimized, byproducts participate more deeply in the hydration reaction, the mortar structure is more compact, and strength loss is reduced.

[0097] Examples 2 and 3, while replacing cement, ensure the integrity of cement hydration. This isn't a simple replacement; rather, with the help of hydration regulators and ultrafine quartz powder, the mineral admixtures form a more efficient cementitious system with the cement product during the hydration process. In contrast, while Comparative Example 4 does replace some cement, it doesn't optimize the hydration process, resulting in low mortar strength and even higher carbon emissions per unit strength than Comparative Example 1. In other words, reducing cement is fundamental, while optimizing hydration is paramount. Otherwise, strength is reduced and carbon emissions become even more uneconomical.

[0098] The data clearly shows that simply reducing cement may not be the optimal solution. Reasonable hydration reaction control and material ratio truly determine the performance and carbon emission efficiency of the material. Example 3 only uses 200kg / m 3 Cement is used, yet the strength reaches 33.3 MPa, with the lowest carbon emissions per unit strength. Comparative Example 4, which still relies on cement for strength, ultimately achieves even lower carbon emissions than the traditional formulation. Clearly, optimizing the mix ratio and controlling the hydration process not only conserves resources but also makes the mortar more environmentally friendly and provides more reliable strength.

[0099] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. Low-carbon recycled mortar, characterized in that: Includes the following component materials: 400-500 parts of low carbon cement; 100-150 parts of ultrafine silica fume; 200-300 parts of slag powder; Modified recycled aggregate 200-300 parts; 20-30 parts of hydration reaction regulator; Surface modifier 20-30 parts.

2. The low-carbon regenerated mortar according to claim 1, characterized in that: The low carbon cement is composed of silicate cement, industrial by-product powder and ultrafine quartz powder, and includes, by weight: 350-450 parts of Portland cement; 30-80 parts of industrial by-product powder; Ultrafine quartz powder 20-60 parts.

3. The low-carbon regenerated mortar according to claim 2, characterized in that: The industrial by-product powder is selected from one or more combinations of construction waste recycled micro powder, steel slag powder, fly ash or silicon manganese slag powder.

4. The low-carbon regenerated mortar according to claim 1, characterized in that: The specific surface area of ​​the ultrafine quartz powder is not less than 400 m2 / kg, and can react with cement hydration products during the hydration process to form a hydraulic gel structure.

5. The low-carbon regenerated mortar according to claim 1, characterized in that: The modified recycled aggregate is processed by the following steps: Use aggregate with a particle size range of 0.5mm-5mm; Sandblasting is performed with a sandblasting particle size of 50-100 μm and a sandblasting time of 10-20 minutes; Drying is carried out in an environment of 60-80℃ for 1-2 hours; Soak in a surface modifier solution with a concentration of 1%-3% for 30 minutes.

6. The low-carbon regenerated mortar according to claim 1, characterized in that: The hydration reaction regulator is selected from one or more combinations of dihydrate gypsum, calcium carbonate, sodium silicate, and metakaolin; The surface modifier is selected from one or more combinations of 3-aminopropyltriethoxysilane, polycarboxylic acid water reducer, organic silicon emulsion, and titanate coupling agent.

7. A method for preparing low-carbon regenerated mortar, according to the low-carbon regenerated mortar according to any one of claims 1 to 6, characterized in that: The following steps are involved: S1: Mix low carbon cement, ultrafine silica fume and slag powder in proportion to form a uniform powder; S2: adding the modified recycled aggregate to the mixture obtained in step S1 for dry mixing; S3: adding hydration reaction regulator and surface modifier, and continuing dry mixing; S4: Pack the evenly mixed dry powder to obtain a low-carbon recycled mortar product.

8. The method for preparing low-carbon regenerated mortar according to claim 7, characterized in that: The dry mixing process of step S2 includes: a. Use a mechanical mixer for dry mixing, the speed is controlled at 60-120r / min, and the mixing time is 40-70 seconds; b. Use air flow conveying device for dynamic mixing to make the components evenly dispersed.

9. The method for preparing low-carbon regenerated mortar according to claim 7, characterized in that: In step S3, the hydration reaction regulator and the surface modifier are added in the following manner: S31. Before premixing low carbon cement with ultrafine silica fume and slag powder, evenly disperse the hydration reaction regulator; S32. After the sandblasting treatment of the modified recycled aggregate is completed, the surface modifier is evenly applied by spraying to allow it to be fully adsorbed, and then mixed with other materials after drying.

10. The method for preparing low-carbon regenerated mortar according to claim 7, characterized in that: The packaging method in step S4 includes: a. Use sealed bag packaging; b. Use vacuum packaging.

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