A concrete solid brick prepared by using biomass boiler fly ash and a preparation method thereof

Abstract

The application provides a concrete solid brick prepared from biomass boiler fly ash and a preparation method thereof, and relates to the fields of solid waste resource utilization and building materials. The solid brick is prepared from biomass boiler fly ash and portland cement as cementitious components, and is prepared by mixing the components with a specific weight ratio of a composite active activator, an efficient polycarboxylate superplasticizer, graded sand and gravel aggregate and mixing water. The preparation adopts the processes of raw material pretreatment, dry material mixing, twice water wet mixing, online water content detection and self-adaptive filtering, feedforward compensation and water-binder ratio checking, high-pressure pressing forming and constant-temperature and constant-humidity spraying curing. The application improves the activity of biomass fly ash by composite activation, and solves the problems of low activity of biomass fly ash, large water demand and large forming quality fluctuation by precise closed-loop control of water content. The obtained brick body has high strength, small shrinkage, high appearance qualification rate and stable production.

Description

Technical Field

[0001] This invention relates to the fields of solid waste resource utilization and building materials, specifically to a solid concrete brick prepared using fly ash from a biomass boiler and its preparation method. Background Technology

[0002] Fly ash, as a solid waste from coal-fired power plants, has been widely studied and applied in building materials, such as concrete admixtures. However, the physicochemical properties of fly ash produced from the combustion of biomass fuels (such as rice husks and sawdust) in boilers differ significantly from those of traditional coal-fired fly ash. Biomass boiler fly ash typically has higher porosity, larger specific surface area, and different mineral composition, resulting in lower activity and higher water demand.

[0003] In existing technologies, the direct use of fly ash from biomass boilers to prepare concrete products faces the following main technical problems: 1) Due to the low activity of fly ash, the early strength development of the product is slow, which affects production efficiency; 2) The high water demand of fly ash requires an increase in mixing water to achieve workability, which in turn increases the water-cement ratio and impairs the final strength and durability of the product. 3) When using high-pressure molding process, the fluctuation of material moisture content will significantly affect the molding effect and brick quality. Traditional water addition methods are difficult to achieve precise control of moisture content, which can easily lead to uneven density of bricks or cracks. Summary of the Invention

[0004] The purpose of this invention is to solve the problems mentioned in the background art, and to propose a method for preparing solid concrete bricks using fly ash from biomass boilers.

[0005] The technical solution adopted by this invention to solve its technical problem is: A type of solid concrete brick prepared using fly ash from a biomass boiler is composed of cementitious components, admixtures, graded sand and gravel aggregates, and mixing water. The raw material ratio, by weight, is as follows: Fly ash from biomass boilers: 35-45 parts Silicate cement: 18-25 parts Compound active activator: 1.5-2.5 parts High-efficiency polycarboxylate superplasticizer: 0.3-0.6 parts Graded sand and gravel aggregate: 150%-200% of the total weight of (biomass boiler fly ash + silicate cement); Mixing water: The amount used should be controlled so that the water-cement ratio is between 0.32 and 0.4. Water-cement ratio = mass of water / (total mass of biomass boiler fly ash + silicate cement).

[0006] Furthermore, the particle size of the fly ash from the biomass boiler is no greater than 0.075 mm.

[0007] Furthermore, the composite active activator is composed of anhydrous sodium sulfate, anhydrous sodium silicate, and calcium hydroxide in a mass ratio of 1:1:1.

[0008] Furthermore, the maximum particle size of the graded sand and gravel aggregate is no greater than 10 mm.

[0009] The present invention also provides a method for preparing the solid concrete brick, characterized by comprising the following steps: Step 1) Raw material pretreatment: Screen the fly ash from the biomass boiler to remove impurities and large particles; Step 2) Dry material mixing: Add biomass boiler fly ash, silicate cement, graded sand and gravel aggregate, and composite active activator into a mixer and mix thoroughly to obtain a dry mixture; Step 3) First wet mixing with water: Add 70% of the total mixing water and high-efficiency polycarboxylate superplasticizer to the dry mixture, and continue to stir until uniform to obtain semi-dry material; Step 4) After the first wet mixing with water, online moisture content detection and filtering in the middle section of the mixer: collect the real-time raw moisture content signal of the semi-dry material, process the raw signal using discrete adaptive weighted moving average filtering, and output the estimated moisture content value; Step 5) Calculate and verify the water replenishment amount: First, calculate the feedforward compensation water amount based on the moisture content deviation, and then verify it in conjunction with the target water-cement ratio. Take the smaller value between the feedforward compensation water amount and the verification water amount as the final water replenishment amount: Based on the deviation between the estimated moisture content and the target moisture content, combined with the preset dead zone threshold, proportional coefficient and target water-cement ratio, calculate the compensation water amount, and verify the water-cement ratio of the compensation water amount. Step 6) Secondary water replenishment and mixing: Add the verified compensation water to the mixer and continue mixing until uniform to obtain the material for molding; Step 7) High-pressure pressing molding: The molding material is fed into a hydraulic brick making machine and pressed into shape under a pressure of 16-18MPa for 3-5 seconds to obtain a brick blank; Step 8) Curing: Place the brick blanks in an environment with a temperature of 18~22℃ and a relative humidity of ≥90% for 28 days to obtain solid concrete bricks.

[0010] Furthermore, the algorithm for the discrete adaptive weighted moving average filtering described in step 4) is as follows: The formula for calculating the smoothed moisture content estimate wT at the current moment is: wT=(α0·wt+α1·wt-1+α2·wt-2+...+αN-1·wt-N+1) / (α0+α1+α2+...+αN-1) The adaptive weight αi is first calculated according to the following formula, and then normalized (Σαi=1): αi=1 / (1+β·|w t-i w t-i-1 |) Where t is the current sampling time, w t-i Let be the original moisture content sampled value at time ti; N is the sliding window length, 3≤N≤10; β is the sensitivity coefficient, with a value range of 0.5≤β≤2.0. αi is the adaptive weight of the i-th historical point.

[0011] Furthermore, the calculation rule for calculating the compensation water volume based on the moisture content deviation in step 5) is as follows: When |w_target When wT|>δ, Vadd-feed=Kp·(w_target wT) When |w_target When wT|≤δ, Vadd-feed=0.

[0012] Where w_target is the target moisture content that matches the target water-cement ratio, δ is the dead zone threshold with a value ranging from 0.3% to 0.8%, Kp is the proportional coefficient with a value ranging from 100 to 150, and Vadd-feed is the feedforward compensation water volume.

[0013] Furthermore, the formula for checking the water-cement ratio in step 5) is: Vadd-check=B·(w / b)_target w1 w_material w_aggregate Where Vadd-check is the check water volume, B is the total mass of biomass boiler fly ash + silicate cement, (w / b)_target is the target water-cement ratio, w1 is the first water addition, w_material is the water introduced by the raw materials themselves, and w_aggregate is the saturated surface dry moisture content of the aggregate.

[0014] Furthermore, in step 8), the curing stage adopts constant temperature and humidity spray curing, and sprays once every 4 hours for the first 3 days of curing, and sprays twice a day after 3 days. During the curing period, the surface of the brick blank is kept moist and not dry.

[0015] Compared with the prior art, the beneficial effects of the present invention are: In the concrete solid brick and its preparation method as described in this invention, by optimizing the proportion of cementitious materials, introducing a specific composite active activator to activate the potential activity of biomass boiler fly ash, and using a high-efficiency water-reducing agent to reduce the water-cement ratio, the mechanical properties and durability of the product are improved from the material's fundamental nature.

[0016] More importantly, the precise control strategy of "online moisture content detection - adaptive filtering - feedforward compensation and water-binder ratio verification" effectively suppresses random fluctuations in the moisture content of the material, ensuring that the material is in the optimal and stable moisture content state before high-pressure molding.

[0017] This allows the brick blank to be uniformly compacted under high pressure, avoiding defects such as uneven strength and cracks caused by local over-wetting or over-drying. This solves the problems of low activity, high water demand and difficulty in controlling moisture content mentioned in the background technology, and finally obtains high-performance and high-quality solid concrete bricks. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions in the embodiments of this invention will be clearly and completely described below in conjunction with the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0019] The fly ash from biomass boilers to be treated has irregular, porous particles due to its combustion raw materials such as rice husks and sawdust, resulting in lower activity and a higher water requirement compared to traditional fly ash. If used directly in brick making, it will result in low early strength and high water demand, easily leading to product performance defects.

[0020] This invention provides a solid concrete brick prepared using fly ash from a biomass boiler, which is composed of cementitious components, admixtures, graded sand and gravel aggregates, and mixing water. By weight, the raw material ratio is as follows: biomass boiler fly ash: 35-45 parts, silicate cement: 18-25 parts, composite active activator: 1.5-2.5 parts, high-efficiency polycarboxylate superplasticizer: 0.3-0.6 parts, graded sand and gravel aggregate: 150%-200% of the total weight of (biomass boiler fly ash + silicate cement); mixing water: the amount used should be controlled at a water-cement ratio of 0.32-0.4, water-cement ratio = water mass / (biomass boiler fly ash + silicate cement) total mass. By using silicate cement to provide an early strength foundation, a composite active activator to depolymerize and activate the potential pozzolanic activity of fly ash from biomass boilers, a high-efficiency polycarboxylate superplasticizer to release free water in the material at a low water-cement ratio and ensure workability, and graded sand and gravel aggregates to form a solid skeleton, the synergistic effect of each component allows the brick to be formed densely at a low water-cement ratio. The later strength continues to increase with the secondary hydration reaction of fly ash, fundamentally overcoming the problems of insufficient brick strength and durability caused by low activity of fly ash and high water demand in biomass boilers.

[0021] To further enhance the reactivity of fly ash and ensure its full participation in the cementing system, the particle size of the biomass boiler fly ash in this embodiment is no greater than 0.075 mm. After passing through a 0.075 mm sieve, the originally porous and loose structure of the biomass boiler fly ash is improved by removing large particles and unburned organic fiber impurities, significantly increasing the specific surface area of ​​the fine particles, expanding the contact interface with the activator and the cement hydration product calcium hydroxide, and increasing the probability of exposure of active sites.

[0022] In Example 1, if fly ash that passes through a 0.075mm sieve is used, the 28-day compressive strength can be increased by about 15% compared with fly ash that does not pass through a sieve and has a 20% oversize. This indicates that fine-particle fly ash is more easily activated and contributes to the later strength.

[0023] To further maximize the activation potential under a specific composite activator ratio, the composite active activator is composed of anhydrous sodium sulfate, anhydrous sodium silicate, and calcium hydroxide in a mass ratio of 1:1:1.

[0024] Anhydrous sodium sulfate provides SO4 2- The ions can react with the active Al2O3 in fly ash and Ca(OH)2 produced by cement hydration to form ettringite, resulting in an early expansion and densification effect. Anhydrous sodium silicate introduces active SiO3 2- It directly replenishes the silica components required for the gel phase, accelerating the formation of CSH gel; Calcium hydroxide, on the other hand, forcibly increases the alkalinity of the system, disrupts the glassy network structure of fly ash, and accelerates ion dissolution.

[0025] In Example 2, the 1:1:1 activator system showed a 28-day compressive strength that was about 8 MPa higher than that of a scheme using a single activator component or with a deviation in proportion, and a drying shrinkage value that was about 15% lower, demonstrating a significant synergistic enhancement and shrinkage reduction effect.

[0026] To further ensure the density of aggregate packing and the smoothness of the molded blank surface, the maximum particle size of the graded sand and gravel aggregate is no greater than 10mm. Controlling the particle size to 10mm allows the aggregate particles to fill the narrow cavity of the brick mold more tightly, reducing voids between aggregates. It also avoids sharp edges, burrs, or localized stress concentrations caused by large-diameter aggregates piercing the surface of the semi-dry material during high-pressure molding.

[0027] In Example 3, continuous graded aggregate with a maximum particle size of 10mm was used, and the appearance qualification rate of the brick blanks was maintained above 98.8%. No obvious defects caused by excessively large aggregates were visible to the naked eye, and the compressive strength of the brick body was also effectively guaranteed due to the optimization of the skeleton structure.

[0028] This application also provides a preparation method, including the following steps: Step 1) Raw material pretreatment: Screen the fly ash from the biomass boiler to remove impurities and large particles; Step 2) Dry material mixing: Add biomass boiler fly ash, silicate cement, graded sand and gravel aggregate, and composite active activator into a mixer and mix thoroughly to obtain a dry mixture; Step 3) First wet mixing with water: Add 70% of the total mixing water and high-efficiency polycarboxylate superplasticizer to the dry mixture, and continue to stir until uniform to obtain semi-dry material; Step 4) After the first wet mixing with water, online moisture content detection and filtering in the middle section of the mixer: collect the real-time raw moisture content signal of the semi-dry material, process the raw signal using discrete adaptive weighted moving average filtering, and output the estimated moisture content value; Step 5) Calculate and verify the water replenishment amount: First, calculate the feedforward compensation water amount based on the moisture content deviation, and then verify it in conjunction with the target water-cement ratio. Take the smaller value between the feedforward compensation water amount and the verification water amount as the final water replenishment amount: Based on the deviation between the estimated moisture content and the target moisture content, combined with the preset dead zone threshold, proportional coefficient and target water-cement ratio, calculate the compensation water amount, and verify the water-cement ratio of the compensation water amount. Step 6) Secondary water replenishment and mixing: Add the verified compensation water to the mixer and continue mixing until uniform to obtain the material for molding; Step 7) High-pressure pressing molding: The molding material is fed into a hydraulic brick making machine and pressed into shape under a pressure of 16-18MPa for 3-5 seconds to obtain a brick blank; Step 8) Curing: The brick blanks are cured in an environment with a temperature of 18~22℃ and a relative humidity of ≥90% for 28 days to obtain solid concrete bricks. This method uses two-stage water addition and precise online moisture content compensation control. 70% of the mixing water is added first to form a semi-dry material, providing a stable material flow for subsequent sensor detection and adaptive filtering, making the moisture content estimate accurate and reliable. Then, based on the precise deviation after filtering, water replenishment is calculated, and combined with the water-binder ratio check, the moisture content of the final mixture is ensured to be stable within the set target range. This ensures that the material has a constant and optimal molding moisture content during high-pressure molding, guaranteeing that the density and appearance quality of each brick blank are highly consistent. This solves the problem of brick blank quality fluctuations and crack defects caused by water replenishment based on experience.

[0029] To suppress short-term abrupt changes in moisture content signal caused by batch fluctuations in raw materials or uneven mixing, the algorithm for discrete adaptive weighted moving average filtering in step 4) is as follows; The formula for calculating the smoothed water content estimate wT at the current moment is wT=(α0·w t +α1·w t-1 +α2·w t-2 +...+α N-1 ·w t-N+1 ) / (α0+α1+α2+...+α N-1 The adaptive weight αi is first calculated according to the following formula, and then normalized (Σαi=1). αi=1 / (1+β·|wt-i wt-i-1|) Where t is the current sampling time, w t-i Let be the original moisture content sampled value at time ti; N is the sliding window length, 3≤N≤10; β is the sensitivity coefficient, with a value range of 0.5≤β≤2.0. α i Let be the adaptive weight for the i-th historical point.

[0030] When the difference between two adjacent points of the sensor signal is |w t-i w t-i-1 When the value suddenly increases, the adaptive weight αi will decrease sharply due to the increase in the denominator, thereby reducing the contribution of the suspected noise point in the weighted average; conversely, when the signal changes gradually, the weight approaches 1, and normal data points are fully preserved.

[0031] For example, when a local material in the mixer is not fully homogenized and a momentary high moisture content reading occurs, if β is set to 1.0 and the window length N is set to 5, the normalization weight obtained for this outlier will be less than 0.05, and the filtered output wT will hardly produce any error fluctuations, so that the control system can obtain a smooth estimate that can truly represent the overall moisture content of the material.

[0032] To avoid repeated minor water replenishment oscillations caused by small deviations near the target moisture content, and to quickly respond to significant deviations, the calculation rule for calculating the compensation water volume based on the moisture content deviation in step 5) is as follows: When |w _target When wT|>δ, V add - feed =K p ·(w _target wT) When |w _target When wT|≤δ, V add - feed =0.

[0033] Where w _target To match the target water-cement ratio, the target moisture content is defined as δ, which is the dead zone threshold, ranging from 0.3% to 0.8%. K p V is a proportionality constant, with a value ranging from 100 to 150. add - feed This is for feedforward compensation water volume.

[0034] Set a dead zone threshold δ of 0.5%. When the filtered moisture content estimate wT differs from the target value w... _target When the difference is only 0.3%, the system determines it as a measurement fluctuation or an acceptable deviation, and does not output any compensation water volume to avoid frequent operation of the solenoid valve; When the deviation exceeds 0.5%, such as wT being 0.8% lower than the target value, a proportional coefficient Kp=120 can be used to calculate a clear feedforward compensation water volume, achieving rapid, one-time coarse adjustment water replenishment.

[0035] To prevent sensor system deviations or feedforward calculation parameter settings from causing the total water addition to exceed the water-cement ratio limit, the formula for water-cement ratio verification in step 5) is: V add-check =B·(w / b) _target w1 w_ material w _aggregate Where V add-check For verifying water volume, B represents the total mass of fly ash and silicate cement from the biomass boiler (w / b). _target The target water-cement ratio is given, where w1 is the amount of water added initially, and w... _material The amount of water introduced by the raw materials themselves, w _aggregate This refers to the saturated surface-dry moisture content of the aggregate.

[0036] This formula, from the perspective of overall material mass balance, calculates the theoretical upper limit of the amount of water that needs to be added to achieve the target water-cement ratio.

[0037] In one production run of Example 1, the feedforward compensation water volume may be calculated to require 1.5L of water due to the high sensitivity of the coefficient. However, the upper limit of the verification water volume calculated by the water-cement ratio verification formula is only 0.9L. Therefore, the system automatically selects 0.9L as the final water volume, strictly adheres to the upper limit of the water-cement ratio, and eliminates the risk of strength collapse caused by excessive moisture.

[0038] To fully utilize the high water absorption properties of fly ash from biomass boilers and promote continuous cement hydration, step 8) of the curing stage adopts constant temperature and humidity spray curing. For the first 3 days of curing, spray once every 4 hours, and after 3 days, spray twice a day. During the curing period, keep the surface of the brick blank moist and not dry.

[0039] For the first three days, high-frequency spraying ensures that there is always sufficient moisture inside the brick during the most intense hydration reaction stage, counteracting the internal self-drying effect of fly ash from biomass boilers due to their porous structure. Subsequently, the frequency is reduced to twice a day to maintain a constant humidity environment, allowing the pozzolanic reaction of fly ash to continue for up to 28 days under stable humidity, thereby obtaining solid concrete bricks with high density, high strength, and low shrinkage.

[0040] To more clearly illustrate the above technical solutions and their beneficial effects, several embodiments and comparative examples are provided below for comparison. It should be understood that these examples are merely illustrative and do not constitute a limitation on the scope of protection.

[0041] The composite active activator is an anhydrous sodium sulfate, anhydrous sodium silicate, and calcium hydroxide premixed in a mass ratio of 1:1:1 into a uniform powder. The high-efficiency polycarboxylate superplasticizer is a liquid with a solid content of 40%. The graded sand and gravel aggregate is continuously graded natural river sand and crushed stone with a maximum particle size of no more than 10 mm. The fly ash from the biomass boiler passes through a 0.075 mm sieve.

[0042] Unless otherwise specified, all raw materials used in the following examples and comparative examples are commercially available products in the art.

[0043] The fly ash from the biomass boiler was taken from a biomass power plant, and its loss on ignition was 8.5%, with a 20% residue on a 45μm sieve.

[0044] The composite active activator is composed of anhydrous sodium sulfate, anhydrous sodium silicate, and calcium hydroxide mixed in a mass ratio of 1:1:1.

[0045] The high-efficiency polycarboxylate superplasticizer has a solid content of 40%.

[0046] The graded sand and gravel aggregate is a mixture of natural river sand and crushed stone in a certain proportion, with a maximum particle size of 10mm.

[0047] Example 1 A type of solid concrete brick made from fly ash from a biomass boiler has the following raw material proportions by weight: Fly ash from biomass boilers (particle size ≤ 0.075 mm): 40 parts Silicate cement (P.O42.5): 22 parts Compound active activator: 2.0 parts High-efficiency polycarboxylate superplasticizer: 0.45 parts Graded sand and gravel aggregate: mass is (40+22)*180%=111.6 parts Mixing water: to control the final water-cement ratio at 0.36.

[0048] Its preparation method includes the following steps: 1. Raw material pretreatment: Pass the fly ash from the biomass boiler through a 0.075mm square mesh sieve.

[0049] 2. Dry mixing: Add the above-mentioned proportions of fly ash, cement, aggregate, and activator into a twin-shaft mixer and dry mix for 3 minutes.

[0050] 3. First wet mixing with water: Add 70% of the calculated total water (based on a water-to-binder ratio of 0.36) and all the water-reducing agent, and wet mix for 2 minutes to obtain a semi-dry material.

[0051] 4. Moisture content detection and filtering: The online sensor collects the raw moisture content signal, sets the sliding window N=5, the sensitivity coefficient β=1.0, and uses the discrete adaptive weighted moving average filtering algorithm to calculate the current moisture content estimate wT.

[0052] 5. Calculate and verify the water replenishment: Set the target moisture content w _target =15.2% (corresponding to a water-to-binder ratio of 0.36), dead zone threshold δ=0.5%, proportionality coefficient K p =120, based on the filtered wT and w _target Deviation calculation of feedforward compensation water volume V add - feed .

[0053] Meanwhile, according to the water-to-binder ratio verification formula V add-check =B·(w / b) _target w1 w_ material w _aggregate Calculate the verification water volume. Take V. add - feed With V add-check The smaller value is taken as the final water replenishment amount.

[0054] 6. Second water addition and stirring: Add the final determined amount of water and continue stirring for 2 minutes until uniform.

[0055] 7. High-pressure pressing molding: The material is fed into the brick making machine and pressed into shape under a pressure of 17MPa for 4 seconds.

[0056] 8. Curing: The brick blanks are cured at 20℃ and RH≥95%. Spray once every 4 hours for the first 3 days, and then spray once in the morning and once in the evening for 28 days.

[0057] Example 2 The difference from Example 1 is that: the biomass boiler fly ash is 35 parts, silicate cement is 25 parts, composite active activator is 1.5 parts, high-efficiency polycarboxylate superplasticizer is 0.3 parts, the mass of graded sand and gravel aggregate is (35+25)*150%=90 parts, the target water-cement ratio is 0.32, and the molding pressure is 16MPa.

[0058] Example 3 The difference from Example 1 is that: the biomass boiler fly ash is 45 parts, silicate cement is 18 parts, composite active activator is 2.5 parts, high-efficiency polycarboxylate superplasticizer is 0.6 parts, the mass of graded sand and gravel aggregate is (45+18)*200%=126 parts, the target water-cement ratio is 0.4, and the molding pressure is 18MPa.

[0059] Comparative Example 1 The difference from Example 1 is that no composite active activator is added.

[0060] Comparative Example 2 The difference from Example 1 is that steps 4) and 5) in the preparation method are replaced with traditional experience-based water estimation, that is, the operator judges and adds the remaining 30% of the estimated water based on the feel of the material.

[0061] Comparative Example 3 The difference from Example 1 is that an equal amount of ordinary coal fly ash (Grade II) is used to replace the fly ash from the biomass boiler.

[0062] The performance of the solid concrete bricks prepared in the above embodiments and comparative examples was tested, and the results are shown in Table 1 below: Table 1. Performance test results of solid concrete bricks in each embodiment and comparative example.

[0063] As can be seen from the data in Table 1, Examples 1 to 3 all showed excellent performance in 28-day compressive strength, drying shrinkage value, water absorption rate, and appearance qualification rate.

[0064] Comparative Example 1 showed a significant decrease in strength and an increase in shrinkage and water absorption in the later stages due to the lack of a composite active activator, demonstrating the key role of the activator in the release of active fly ash in biomass boilers.

[0065] Comparative Example 2, which used empirical water replenishment, saw its brick blank qualification rate plummet to 92.5%, and its appearance showed obvious cracks. This fully demonstrates the decisive significance of the online moisture content detection and adaptive compensation method of this application in overcoming human uncertainty and material fluctuations, and stabilizing the quality of high-pressure molding.

[0066] Although Comparative Example 3 achieved higher strength using traditional coal-fired fly ash, it did not involve the disposal problem of fly ash from biomass boilers.

[0067] Data analysis and results description: 1. Strength and durability: Examples 1-3 all exhibited high compressive strength (≥35.2MPa) and low drying shrinkage and water absorption, indicating that the formulation of the present invention effectively activated the activity of fly ash in biomass boilers and improved density through a low water-cement ratio.

[0068] 2. Precision of moisture content control: The qualified rate of brick blanks in Examples 1-3 is higher than 98.8%, and the appearance quality is excellent. This is due to the precise moisture content control strategy.

[0069] 3. Formula Application Effect: The discrete adaptive weighted moving average filtering formula in step 4) assigns higher weights (α) to historical data with gradual changes. i (Larger), effectively filtering out sensor noise and sudden changes in moisture content signal caused by local unevenness of materials, resulting in a more stable and reliable moisture content estimate wT.

[0070] Step 5) Feedforward compensation formula V add - feed =K p ·(w _target wT) achieves a fast deviation response, while the dead zone threshold δ avoids unnecessary adjustment oscillations near the target value.

[0071] Water-to-binder ratio verification formula V add-check =B·(w / b) _target w1 w_ material w _aggregate This provides a theoretical upper limit for the amount of water to be added based on the total amount of material, preventing excessive water addition due to systematic deviations of the sensor system or errors in feedforward calculations. The combination of these two factors ensures the accurate realization of the final water-cement ratio.

[0072] In summary, the solid concrete bricks and their preparation method provided in this application, through the combination of a specific material system and intelligent preparation process, synergistically improve the product performance and production stability of solid concrete bricks prepared using biomass boiler fly ash, and have good application prospects. They can efficiently dispose of low-quality biomass boiler fly ash and stably manufacture solid brick products with high strength, high durability and excellent appearance.

[0073] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of protection claimed by the present invention. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A type of solid concrete brick prepared using fly ash from a biomass boiler, characterized in that, It consists of cementitious components, admixtures, graded sand and gravel aggregates, and mixing water; The raw material ratio, by weight, is as follows: Fly ash from biomass boilers: 35-45 parts Silicate cement: 18-25 parts Compound active activator: 1.5-2.5 parts High-efficiency polycarboxylate superplasticizer: 0.3-0.6 parts Graded sand and gravel aggregate: 150%-200% of the total weight of (biomass boiler fly ash + silicate cement); Mixing water: The amount used should be controlled so that the water-cement ratio is between 0.32 and 0.

4. Water-cement ratio = mass of water / (total mass of biomass boiler fly ash + silicate cement).

2. The solid concrete brick according to claim 1, characterized in that, The particle size of the fly ash from the biomass boiler is no greater than 0.075 mm.

3. The solid concrete brick according to claim 1, characterized in that, The composite active activator is composed of anhydrous sodium sulfate, anhydrous sodium silicate, and calcium hydroxide in a mass ratio of 1:1:

1.

4. The solid concrete brick according to claim 1, characterized in that, The maximum particle size of the graded sand and gravel aggregate is no more than 10 mm.

5. A method for preparing solid concrete bricks according to any one of claims 1-4, characterized in that, Includes the following steps: Step 1) Raw material pretreatment: Screen the fly ash from the biomass boiler to remove impurities and large particles; Step 2) Dry material mixing: Add biomass boiler fly ash, silicate cement, graded sand and gravel aggregate, and composite active activator into a mixer and mix thoroughly to obtain a dry mixture; Step 3) First wet mixing with water: Add 70% of the total mixing water and high-efficiency polycarboxylate superplasticizer to the dry mixture, and continue to stir until uniform to obtain semi-dry material; Step 4) After the first wet mixing with water, online moisture content detection and filtering in the middle section of the mixer: collect the real-time raw moisture content signal of the semi-dry material, process the raw signal using discrete adaptive weighted moving average filtering, and output the estimated moisture content value; Step 5) Calculate and verify the water replenishment amount: First, calculate the feedforward compensation water amount based on the moisture content deviation, and then verify it in conjunction with the target water-cement ratio. Take the smaller value between the feedforward compensation water amount and the verification water amount as the final water replenishment amount: Based on the deviation between the estimated moisture content and the target moisture content, combined with the preset dead zone threshold, proportional coefficient and target water-cement ratio, calculate the compensation water amount, and verify the water-cement ratio of the compensation water amount. Step 6) Secondary water replenishment and mixing: Add the verified compensation water to the mixer and continue mixing until uniform to obtain the material for molding; Step 7) High-pressure pressing molding: The molding material is fed into a hydraulic brick making machine and pressed into shape under a pressure of 16-18MPa for 3-5 seconds to obtain a brick blank; Step 8) Curing: Place the brick blanks in an environment with a temperature of 18~22℃ and a relative humidity of ≥90% for 28 days to obtain solid concrete bricks.

6. The preparation method according to claim 5, characterized in that, The algorithm for the discrete adaptive weighted moving average filter described in step 4) is as follows: The formula for calculating the smoothed moisture content estimate wT at the current moment is: wT=(α0·w t +α1·w t-1 +α2·w t-2 +...+a N-1 ·w t-N+1 ) / (α0+α1+α2+...+α N-1 ) Wherein, the adaptive weight α i First calculate using the following formula, then normalize (Σαi=1): αi=1 / (1+β·|w t-i w t-i-1 |) Where t is the current sampling time, w t-i Let be the original moisture content sampled value at time ti; N is the sliding window length, 3≤N≤10; β is the sensitivity coefficient, with a value range of 0.5≤β≤2.

0. α i Let be the adaptive weight for the i-th historical point.

7. The preparation method according to claim 5, characterized in that, The calculation rule for calculating the compensation water volume based on the moisture content deviation in step 5) is as follows: When |w _target wT| > δ, V add - feed = K p ·(w _target wT) When |w _target When wT|≤δ, V add - feed =0. Where w _target To match the target water-cement ratio, the target moisture content is defined as δ, which is the dead zone threshold, ranging from 0.3% to 0.8%. K p V is a proportionality constant, with a value ranging from 100 to 150. add - feed This is for feedforward compensation water volume.

8. The method for preparing solid concrete bricks using fly ash from a biomass boiler according to claim 5, characterized in that, The formula for checking the water-cement ratio in step 5) is: V add-check =B·(w / b) _target w1 w_ material w _aggregate Where V add-check For verifying water volume, B represents the total mass of fly ash and silicate cement from the biomass boiler (w / b). _target The target water-cement ratio is given, where w1 is the amount of water added initially, and w... _material The amount of water introduced by the raw materials themselves, w _aggregate This refers to the saturated surface-dry moisture content of the aggregate.

9. The preparation method according to claim 5, characterized in that, Step 8) During the curing stage, use constant temperature and humidity spray curing. Spray once every 4 hours for the first 3 days of curing, and spray twice a day thereafter. Keep the surface of the brick moist and not dry during the curing period.

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