Concrete capable of circularly absorbing and releasing water and preparation method thereof

Abstract

The invention relates to the technical field of concrete, in particular to concrete capable of circularly absorbing and releasing water and a preparation method thereof.The concrete comprises high-water-absorption aggregate and a functional additive, floating beads are adopted as an open pore water storage unit, shale sand provides structural strength support, ceramsite serves as an open pore water storage medium, and the functional additive is added into the open pore water storage unit; the cement, the coal ash and the polycarboxylic acid water reducing agent are supplemented to synergistically optimize the performance of the slurry. The preparation process comprises the following steps: saturatively soaking the aggregate to a saturated surface dry state; pre-mixing the shale sand and the ceramsite with the cement and the coal ash which are added in batches; then introducing floating beads for temporary stirring, injecting clear water by stages, synchronously adding a water reducing agent, and fully stirring to form a homogeneous mixture; and finally, pouring and vibrating, and completing standard curing in a constant-temperature and high-humidity environment. According to the method, the concrete has high mechanical strength and a long-acting water absorption and release circulation function, and the technical bottleneck that the water storage capacity and the structural performance of a traditional material are incompatible is broken through.

Description

Technical Field

[0001] The present invention relates to the technical field of concrete, and in particular to concrete capable of cyclically absorbing and releasing water and a preparation method thereof. Background Art

[0002] In recent years, with the acceleration of urbanization and the frequent occurrence of extreme climate events, the dynamic management of urban water resources and the innovation of green building materials have become research hotspots in the field of building materials. In this context, smart concrete technology, which combines water treatment capabilities with structural load-bearing capacity, has become a key research direction in the field.

[0003] In the field of traditional concrete, existing research has largely focused on reducing concrete porosity and increasing density, thereby achieving low or even no water absorption. Alternatively, permeable concrete technology can be used to increase concrete porosity, allowing water to quickly penetrate. However, research in the field of absorbable water storage is scarce.

[0004] In the existing technology, porous lightweight aggregate or super absorbent resin is added to concrete to improve water storage capacity, but there are significant defects: although lightweight aggregate has water storage space, the high porosity leads to a significant reduction in compressive strength, and the water release is explosive, and slow release cannot be achieved; and super absorbent resin materials are prone to expansion and rupture during repeated water absorption and release, destroying the concrete microstructure and resulting in reduced durability. Summary of the Invention

[0005] In order to solve the aforementioned technical problems, the present invention provides a concrete that can absorb and release water cyclically and a preparation method thereof. The concrete has both high mechanical strength and long-term water absorption and release circulation functions, solving the technical problem of the incompatibility between the water storage capacity and structural performance of traditional materials. This is specifically achieved through the following technical solutions.

[0006] The present invention provides a method for preparing concrete capable of cyclically absorbing and releasing water, comprising the following steps: S1. Soak the floating beads, shale sand and ceramsite until saturated with water, and then dry them to obtain saturated surface-dry aggregate for standby use; S2. Add the shale sand and ceramsite obtained in step S1 to a mixer and stir for 1 to 2 minutes. Add cement and fly ash in equal amounts in 3 to 5 portions. Continue stirring for 1 to 2 minutes after addition. S3. The floating beads obtained in step S1 were added to a blender and stirred for 1 min. 110 to 130 parts of water were added and stirred for 8 to 12 min. 55 to 65 parts of water and 10 to 12 parts of a water reducer were then added. The stirring was continued until 28 to 32 min had elapsed since the first addition of water. S4. After mixing, pour into a mold treated with a release agent and vibrate. After solidification and demoulding, standard curing is carried out for 28 days.

[0007] Preferably, the standard curing conditions in step S4 are: temperature 18-22° C., humidity ≥ 95%.

[0008] Preferably, in step S2, the time interval between each addition of cement and fly ash is 20 to 40 seconds.

[0009] Preferably, the vibration conditions are: vibration frequency 50-100 Hz, and vibration time 15-30 s.

[0010] Preferably, the mass ratio of the added floating beads, shale sand, ceramsite, cement, fly ash, clean water and water reducer is 24-30:36-44:45-54:31.5-38.5:12-14:16.5-19.5:0.8-1.2.

[0011] Preferably, the particle size of the floating beads is 0.075-0.425 mm, and the water absorption rate is >35%. The shale sand is medium sand of crushed shale sand, and its crushing value is <30% and the water absorption rate is >15%. The ceramsite has a crushing value <30% and the water absorption rate is >10%.

[0012] Preferably, the cement is PO42.5 cement, and the fly ash is Class II fly ash.

[0013] Preferably, the water reducer is a polycarboxylic acid high-performance water reducer with a water reduction rate greater than 25%.

[0014] The present invention also provides concrete capable of cyclically absorbing and releasing water, which is prepared using the above-mentioned method for preparing concrete capable of cyclically absorbing and releasing water.

[0015] After adopting the above technical solution, the beneficial effects of the present invention are: 1. Through forced saturated immersion combined with surface drying, the internal pores of the aggregate are filled with water while the surface is free of water film, which completely avoids water competition during mixing, ensures that the cement is fully hydrated on the aggregate surface, forms a dense interface transition zone, and significantly improves the strength and stability of concrete in dry and wet states.

[0016] 2. Add cement and fly ash in batches to avoid flocculation and protect the uniformity of the slurry; delay the addition of floating beads and inject water in stages to effectively avoid mechanical damage to thin-walled hollow structures. Combined with the hydrophilic channels constructed by the water reducer, the synergistic effect of closed-pore water storage and open-pore buffering is achieved.

[0017] 3. Polycarboxylate water-reducing agent reduces the surface tension of the liquid in the pores and guides the water to migrate to the deep layer of the beads; the hydration products generated by standard curing selectively block the pores, and the remaining connected pores form a slow-release path, allowing water to slowly seep out according to the concentration gradient, achieving controllable slow release.

[0018] 4. High water absorption shale sand and expanded clay provide water storage buffer and skeleton strength, floating beads with open holes for water storage and water reducer form a directional water transmission network, fly ash microbeads lubricate the slurry and fill cracks with secondary hydration, so that the concrete has high strength, high water storage and long-term circulation capabilities. DETAILED DESCRIPTION

[0019] The features and exemplary embodiments of various aspects of the present invention will be described in detail below. In order to make the objects, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with specific embodiments. It should be understood that the specific embodiments described herein are only configured to explain the present invention and are not configured to limit the present invention. For those skilled in the art, the present invention can be implemented without the need for some of these specific details. The following description of the embodiments is merely to provide a better understanding of the present invention by illustrating examples of the present invention.

[0020] An embodiment of the present invention provides a method for preparing concrete capable of cyclically absorbing and releasing water, which specifically comprises the following steps: Step 1: According to weight, fully soak 240-300 parts of floating beads, 360-440 parts of shale sand, and 450-540 parts of expanded clay respectively until they reach the water absorption saturation state, and then spread them out to dry on the surface to obtain floating beads, shale sand and expanded clay in a saturated surface dry state for use.

[0021] Among them, the shale sand is crushed shale sand, and the specification is medium sand, that is, the fineness modulus of the crushed shale sand is between 2.3 and 3.0, its crushing value is less than 30%, and the water absorption rate is greater than 15%.

[0022] Among them, the particle size of the floating beads is 0.075~0.425mm, the water absorption rate is greater than 35%, the crushing value of the expanded clay is less than 30%, and the water absorption rate is greater than 10%.

[0023] In this step, the water is forced to enter the internal pores of the aggregate through capillary action by soaking and saturating the aggregate until the surface is dry, thereby eliminating the water film attached to the surface of the aggregate and preventing free water from interfering with the subsequent water-binder ratio calculation.

[0024] After the aggregate is subjected to prior water absorption treatment, the water will not be immediately absorbed when it comes into contact with cement slurry, ensuring that the cement particles are fully hydrated on the surface of the aggregate, forming a dense interface transition zone, avoiding cracks in the gaps between the aggregates, and thus effectively improving the strength and hardness of the concrete.

[0025] In addition, the crushing value of shale sand and expanded clay is less than 30%, which can ensure that the aggregate does not undergo structural collapse under mixing and extrusion. The water absorption rate of shale sand is greater than 15%, and the water absorption rate of expanded clay is greater than 10%. The mixture of the two makes the concrete have both the strength of natural sand and the water storage function of lightweight aggregate, and the overall performance is more excellent.

[0026] At the same time, adding floating beads with a water absorption rate greater than 35% to the concrete components utilizes the function of storing water due to the large number of open pores inside the floating beads, so that it can be slowly released through the concentration gradient when the environment is dry.

[0027] Step 2: Add the shale sand and ceramsite obtained in step 1 into a concrete mixer, start the concrete mixer, stir for 1 to 2 minutes, then add a total of 315 to 385 parts of cement and 120 to 140 parts of fly ash in 3 to 5 equal portions, and continue stirring for 1 to 2 minutes after all the additions are completed.

[0028] The cement and fly ash are added in equal amounts each time, and the addition time interval is 20 to 40 seconds. During the addition process of the cement and fly ash, the concrete mixer is always in a stirring working state.

[0029] Among them, the cement is PO42.5 cement and the fly ash is Class II fly ash.

[0030] In this step, cement and fly ash are added in batches to avoid a sudden increase in the local water-cement ratio. When the single addition amount is less than the critical cement agglomeration concentration, the flocculated structure formed by the cement particles can be effectively avoided. In addition, the addition time is 20 to 40 seconds, which is longer than the 15 to 20 seconds of aggregation time of the slurry. Therefore, the shear force during stirring can fully destroy the agglomerates, thereby ensuring the uniformity of stirring. In addition, the coarse aggregate is added first and the fine particles are added later in the above stirring process, which can reduce the loss of stirring energy caused by the fine particles, thereby improving the stirring efficiency.

[0031] The Class II fly ash added during the above steps contains more than half of glass beads, so it can roll between the gaps between aggregates during the mixing process, playing a certain bearing role, thereby reducing the viscosity of the slurry; in addition, the fly ash contains active SiO2, which can react with the cement hydration product Ca(OH)2 to form hydrated calcium silicate, thereby filling the cracks around the lightweight aggregate, thereby significantly improving the later strength of the concrete.

[0032] Step 3: Continue to add the floating beads prepared in step 1 to the concrete mixer, stir for 1 minute, add 110 to 130 parts of clean water, continue stirring for 8 to 12 minutes, then add 55 to 65 parts of clean water and 8 to 12 parts of water reducer, continue stirring until 28 to 32 minutes from the time the first water addition is completed, and turn off the concrete mixer to complete the mixing.

[0033] Among them, the water reducer is a polycarboxylic acid high-performance water reducer, and its water reduction rate is greater than 25%.

[0034] The polycarboxylic acid high-performance water-reducing agent added in this step can be adsorbed on the surface of cement particles, generating electrostatic repulsion and steric hindrance, breaking the cement agglomeration structure, and effectively improving the fluidity of the slurry. In addition, the polycarboxylic acid high-performance water-reducing agent can also reduce the surface tension of water, making it easier for water to penetrate into the gaps and enhance wettability. In addition, the polycarboxylic acid high-performance water-reducing agent can reduce the surface tension of the pore fluid and improve the water penetration efficiency, thereby guiding the water to migrate to the deep pores of the floating beads, effectively increasing the water storage capacity.

[0035] The above-mentioned floating beads are added after the addition of aggregates and powders because the floating beads are hollow beads with thin walls. If they are added too early, the slurry will be too thin, or the shear force generated by stirring will damage their side walls and cause them to break. Stirring for a short time after adding the floating beads and stirring for a long time after adding water ensures that a viscous slurry is formed to effectively buffer the damage to the floating beads caused by mechanical impact.

[0036] In the above steps, water is added twice, respectively, to avoid adding too much water at one time, which causes the lightweight aggregate to float and thus destroys the homogeneity of the mixture. In addition, adding water twice can maintain the stability of the fluidity of the mixture.

[0037] In the above process, when water is added and contacts cement, a hydration reaction occurs to generate hydrated calcium silicate, which provides an initial strength skeleton for concrete.

[0038] In addition, an extra-long mixing time of 28 to 32 minutes is adopted. On the one hand, sufficient shear mixing is used to allow the cement hydrolysis reaction to proceed fully, and on the other hand, the need for sufficient diffusion of the water reducer is met.

[0039] The concrete system constructed through the above steps can be formed, in which the floating beads can be opened to fill with water and serve as the main water storage force, while the shale sand and expanded clay can be opened to store water and serve as a water storage buffer, and the water reducer is used to reduce the surface tension of the liquid in the pores, so that in a dry environment, the water inside the system can continuously seep out through the pores, achieving the effect of slow water release.

[0040] Step 4: The concrete obtained in step 3 is poured into a forming mold, and after solidification, the mold is removed and standard curing is performed for 28 days to obtain concrete that can absorb and release water cyclically.

[0041] Among them, before pouring concrete, it is necessary to apply a release agent in the forming mold to avoid difficulty in demoulding caused by concrete adhesion.

[0042] During the concrete pouring process, a vibrator is used for vibration with a frequency of 50 to 100 Hz and a vibration time of 15 to 30 seconds. The vibration force can make the mixture more uniform and dense, and the floating beads in the slurry are evenly suspended.

[0043] Among them, under normal temperature environment, the initial setting time of concrete is 4 to 5 hours, and the final setting time is 8 to 10 hours.

[0044] Among them, the standard maintenance conditions are temperature 18℃~22℃ and relative humidity greater than or equal to 95%.

[0045] During the standard curing process of the above steps, within 0 to 7 days, the cement continues to hydrate to form hydrated calcium silicate, thereby bridging the aggregates and filling the pores between the aggregates. Around the 7th day, a hydration product ring will appear at the interface of the floating beads and the slurry. This hydration product ring can selectively close the pores, but retain water molecule channels, thereby effectively maintaining the water absorption and release functions; after 8 to 21 days of curing, the slurry structure tends to be stable and the overall strength gradually increases. After 22 to 30 days of curing, the cement mineral hydration reaction is basically completed, and the system strength growth rate slows down.

[0046] In order to facilitate further understanding of the present invention, several embodiments and comparative examples of the present invention are given below.

[0047] Example 1 This embodiment provides a method for preparing concrete capable of cyclically absorbing and releasing water, comprising the following steps: Step 1: According to weight parts, 270 parts of floating beads with a water absorption rate of 40%, 400 parts of crushed shale sand with a crushing value of 25% and a water absorption rate of 16%, and 495 parts of expanded clay with a crushing value of 25% and a water absorption rate of 12% are fully soaked until they reach the water absorption saturation state, and then spread them out to dry on the surface to obtain floating beads, shale sand and expanded clay in a saturated surface dry state for use.

[0048] Step 2: Add the shale sand and ceramsite obtained in step 1 into a concrete mixer, start the concrete mixer, stir for 1 minute, then add a total of 350 parts of PO42.5 cement and 130 parts of Class II fly ash in 5 equal portions, with an addition interval of 30 seconds. Continue stirring for 1 minute after all the additions are completed.

[0049] Step 3: Continue to add the floating beads prepared in step 1 to the concrete mixer, stir for 1 minute, then add 120 parts of clean water, continue stirring for 10 minutes, then add 60 parts of clean water and 10 parts of polycarboxylic acid high-performance water reducer with a water reduction rate of 28%, continue stirring until 30 minutes from the time when the first water addition is completed, and turn off the concrete mixer to complete the mixing.

[0050] Step 4: The concrete obtained in step 3 is poured into a forming mold coated with a release agent, and vibrated for 20 seconds using a vibrator with a vibration frequency of 80 Hz. After solidification, the mold is removed and the concrete is cured at a temperature of 20°C and a relative humidity of 95% for 28 days to obtain concrete that can absorb and release water cyclically.

[0051] Example 2 This embodiment adjusts the ratio of the raw materials in step 1 based on embodiment 1, specifically: Step 1: According to weight, 240 parts of floating beads with a water absorption rate of 40%, 420 parts of crushed shale sand with a crushing value of 25% and a water absorption rate of 16%, and 510 parts of expanded clay with a crushing value of 25% and a water absorption rate of 12% are fully soaked until they reach the water absorption saturation state, and then spread them out to dry on the surface to obtain floating beads, shale sand and expanded clay in a saturated surface dry state for use.

[0052] The remaining steps of this embodiment are exactly the same as those of embodiment 1.

[0053] Example 3 This embodiment adjusts the ratio of the raw materials in step 1 based on embodiment 1, specifically: Step 1: According to weight, 290 parts of floating beads with a water absorption rate of 40%, 380 parts of crushed shale sand with a crushing value of 25% and a water absorption rate of 16%, and 480 parts of expanded clay with a crushing value of 25% and a water absorption rate of 12% are fully soaked until they reach the water absorption saturation state, and then spread them out to dry on the surface to obtain floating beads, shale sand and expanded clay in a saturated surface dry state for use.

[0054] The remaining steps of this embodiment are exactly the same as those of embodiment 1.

[0055] Example 4 This embodiment adjusts the ratio of raw materials in step 2 based on embodiment 1, specifically: Step 2: Add the shale sand and ceramsite obtained in step 1 into a concrete mixer, start the concrete mixer, stir for 1 minute, then add a total of 370 parts of PO42.5 cement and 140 parts of Class II fly ash in 5 equal portions, with an addition interval of 30 seconds. Continue stirring for 1 minute after all the additions are completed.

[0056] The remaining steps of this embodiment are exactly the same as those of embodiment 1.

[0057] Example 5 This embodiment adjusts the feeding method in step 2 based on embodiment 1, specifically: Step 2: Add the shale sand and ceramsite obtained in step 1 into a concrete mixer, start the concrete mixer, stir for 1 minute, then add a total of 350 parts of PO42.5 cement and 130 parts of Class II fly ash in 3 equal portions, with an addition interval of 30 seconds. Continue stirring for 1 minute after all the additions are completed.

[0058] The remaining steps of this embodiment are exactly the same as those of embodiment 1.

[0059] Example 6 This embodiment adjusts the ratio of raw materials in step 3 based on embodiment 1, specifically: Step 3: Continue to add the floating beads prepared in step 1 to the concrete mixer, stir for 1 minute, then add 130 parts of clean water, continue stirring for 10 minutes, then add 65 parts of clean water and 12 parts of polycarboxylic acid high-performance water reducer with a water reduction rate of 28%, continue stirring until 30 minutes after the first water addition is completed, and turn off the concrete mixer to complete the mixing.

[0060] The remaining steps of this embodiment are exactly the same as those of embodiment 1.

[0061] Comparative Example 1 Step 1: According to weight, prepare 270 parts of floating beads with a water absorption rate of 40%, 400 parts of crushed shale sand with a crushing value of 25% and a water absorption rate of 16%, and 495 parts of expanded clay with a crushing value of 25% and a water absorption rate of 12%.

[0062] Step 2: Add the shale sand and ceramsite obtained in step 1 into a concrete mixer, start the concrete mixer, stir for 1 minute, then add a total of 350 parts of PO42.5 cement and 130 parts of Class II fly ash in 5 equal portions, with an addition interval of 30 seconds. Continue stirring for 1 minute after all the additions are completed.

[0063] Step 3: Continue to add the floating beads prepared in step 1 to the concrete mixer, stir for 1 minute, then add 120 parts of clean water, continue stirring for 10 minutes, then add 60 parts of clean water and 10 parts of polycarboxylic acid high-performance water reducer with a water reduction rate of 28%, continue stirring until 30 minutes from the time when the first water addition is completed, and turn off the concrete mixer to complete the mixing.

[0064] Step 4: The concrete obtained in step 3 is poured into a forming mold coated with a release agent, and vibrated for 20 seconds using a vibrator with a vibration frequency of 80 Hz. After solidification, the mold is removed and the concrete is cured at a temperature of 20°C and a relative humidity of 95% for 28 days to obtain concrete that can absorb and release water cyclically.

[0065] Comparative Example 2 Step 1: According to weight parts, 270 parts of floating beads with a water absorption rate of 40%, 400 parts of crushed shale sand with a crushing value of 25% and a water absorption rate of 16%, and 495 parts of expanded clay with a crushing value of 25% and a water absorption rate of 12% are fully soaked until they reach the water absorption saturation state, and then spread them out to dry on the surface to obtain floating beads, shale sand and expanded clay in a saturated surface dry state for use.

[0066] Step 2: The shale sand and ceramsite obtained in step 1 were added to a concrete mixer, which was started. After stirring for 1 minute, 350 parts of PO42.5 cement and 130 parts of Class II fly ash were added, and stirring was continued for 1 minute.

[0067] Step 3: Continue to add the floating beads prepared in step 1 to the concrete mixer. After stirring for 1 minute, add 180 parts of clean water and 10 parts of polycarboxylic acid high-performance water reducer with a water reduction rate of 28%. Continue stirring for 30 minutes and turn off the concrete mixer to complete the mixing.

[0068] Step 4: The concrete obtained in step 3 is poured into a forming mold coated with a release agent, and vibrated for 20 seconds using a vibrator with a vibration frequency of 80 Hz. After solidification, the mold is removed and the concrete is cured at a temperature of 20°C and a relative humidity of 95% for 28 days to obtain concrete that can absorb and release water cyclically.

[0069] Comparative Example 3 Step 1: According to weight parts, 270 parts of floating beads with a water absorption rate of 40%, 400 parts of crushed shale sand with a crushing value of 25% and a water absorption rate of 16%, and 495 parts of expanded clay with a crushing value of 25% and a water absorption rate of 12% are fully soaked until they reach the water absorption saturation state, and then spread them out to dry on the surface to obtain floating beads, shale sand and expanded clay in a saturated surface dry state for use.

[0070] Step 2: Add the shale sand and ceramsite obtained in step 1 into a concrete mixer, start the concrete mixer, stir for 1 minute, then add a total of 350 parts of PO42.5 cement and 130 parts of Class II fly ash in 5 equal portions, with an addition interval of 30 seconds. Continue stirring for 1 minute after all the additions are completed.

[0071] Step 3: Continue to add the floating beads prepared in step 1 to the concrete mixer, stir for 1 minute, then add 120 parts of clean water, continue stirring for 10 minutes, then add 60 parts of clean water and 10 parts of polycarboxylic acid high-performance water reducer with a water reduction rate of 28%, continue stirring until 30 minutes from the time when the first water addition is completed, and turn off the concrete mixer to complete the mixing.

[0072] Step 4: The concrete obtained in step 3 is poured into a forming mold coated with a release agent, and vibrated for 20 seconds using a vibrator with a vibration frequency of 80 Hz. After solidification, the mold is removed and the concrete is left to stand outdoors for 28 days to obtain concrete that can absorb and release water cyclically.

[0073] By using the method steps in the above embodiment and comparative example, concrete test blocks of 100×100×100 mm were prepared, and their water absorption and water release properties as well as their strength in the states of complete water absorption and complete water release were tested.

[0074] Among them, the strength test uses a press to load the test block and record its specific value.

[0075] Among them, the water absorption performance is reflected by the water absorption rate, and the calculation formula of the water absorption rate is: W=(M 湿 -M 干 ) / M 干 *100% M 湿 It indicates the mass of the test block in the state of complete water absorption. The measurement method is: the test block is completely immersed in water, and the top surface of the test block is not less than 15 cm from the water surface. During the immersion process, a large number of tiny bubbles are released from the surface of the test block into the water. When the bubbles are no longer released, the test block is considered to be saturated with water. The test block is taken out of the water and the water on the surface of the test block is quickly wiped dry. The mass in the saturated water absorption state is weighed as M 湿 .

[0076] M 干 It indicates the mass of the test block in the state of complete water release. The measurement method is: place the concrete test block in an oven at 110℃, ventilate and dry it, and measure its mass every 1 hour. When the difference between the masses of two consecutive measurements is less than 1g, the concrete is considered to be in a dry state, and its mass is weighed as M 干 .

[0077] According to the above testing method, the water absorption performance of the test blocks corresponding to each embodiment and comparative example, as well as the strength of the test blocks in the state of complete water absorption and complete water release, were tested and calculated respectively, and the data were recorded as follows:

[0078] Among them, the water release performance testing method is: place the test block in a completely water-absorbed state in an environment with a temperature of 20°C and a humidity of 50%, let it stand to release water freely, weigh it once every 24 hours, record the data for the first 7 days, and record the time after 80% of the water is released.

[0079] According to the above detection method, the water release performance of the test blocks corresponding to each embodiment and comparative example was detected and calculated, and the recorded data were as follows:

[0080] According to the above data, we can know that: 1. The water absorption rate of each embodiment is generally maintained between 9.5% and 10%. In comparison, due to the omission of the aggregate pre-saturation step, the aggregate competes for cement hydration water during the mixing process, the internal pores are not fully utilized, and the water absorption rate drops to 8%; due to the one-time addition of cement and fly ash in Comparative Example 2, flocculation structure and agglomerates are easily formed, and the homogeneity of the slurry after stirring is poor, resulting in the inability to mix evenly after adding the floating beads, and the binding force between the floating beads and the slurry is poor. In addition, the one-time addition of clean water promotes the floating beads with poor mixing effect to be enriched on the surface under the action of buoyancy, affecting the overall distribution pattern of the floating beads, thereby reducing the water storage capacity, and the water absorption rate is only 6.2%; although Comparative Example 3 completes the aggregate treatment, the outdoor maintenance causes insufficient humidity, the development of the hydration product ring is hindered, the pore channels are blocked, and the water absorption rate is reduced to 7%.

[0081] 2. In the strength test data, the strength of all test blocks in the completely water-absorbed state is about 15% lower than that in the dry state. This is a natural phenomenon that water weakens the cement matrix. The completely water-absorbed strength of the embodiment is maintained at 28-30.1 MPa, and the completely water-released strength reaches 32.5-35.2 MPa; while the strength of Comparative Example 1 decreases due to the loose interface area caused by the lack of pre-saturation of aggregate; the strength of Comparative Example 2 is further deteriorated due to the lack of homogeneity caused by the enrichment of floating beads on the surface; Comparative Example 3 is affected by insufficient curing humidity, the hydration reaction is incomplete, and the strength is significantly lower than that of the standard curing group.

[0082] 3. In the water release performance test, each embodiment achieved a 12-15 day slow release period through the hydrophilic channels constructed by the porous water storage of the floating beads and the water reducer, and the water slowly migrated according to the concentration gradient; Comparative Example 1 relied on the porous aggregate to store water, and the water escaped quickly, reaching 80% water release within 7 days; Comparative Example 2 was enriched in the surface of the concrete components, and the water was directly exposed to the environment, and the main water release process was completed within 5 days; Comparative Example 3 was severely hindered in water release due to the blockage of the pore channels. Although it could maintain a high quality, it took 20 days to release 80%, and lost its functionality.

[0083] From the above data, it can be concluded that aggregate pre-saturation treatment is the basis for ensuring water storage capacity and interface strength; the timing of adding water in batches and adding floating beads is crucial to protecting the microstructure; the hydration product ring formed by standard curing is the functional guarantee of water channels.

[0084] While the embodiments of the present invention are described above, these embodiments do not exhaustively describe all details, nor do they limit the present invention to only specific embodiments. Clearly, many modifications and variations can be made based on the above description. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present invention, thereby enabling those skilled in the art to make good use of the present invention and its modifications and uses. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A method for preparing concrete capable of cyclically absorbing and releasing water, characterized in that: The following steps are involved: S1. Soak the floating beads, shale sand and ceramsite until saturated with water, and then dry them to obtain saturated surface-dry aggregate for standby use; S2. The shale sand and ceramsite obtained in step S1 are added to a mixer and stirred for 1 to 2 minutes. Cement and fly ash are added in equal amounts in 3 to 5 portions. Stirring is continued for 1 to 2 minutes after addition. S3. The floating beads obtained in step S1 were added to a blender and stirred for 1 min. 110 to 130 parts of water were added and stirred for 8 to 12 min. 55 to 65 parts of water and 10 to 12 parts of a water reducer were then added. The stirring was continued until 28 to 32 min had elapsed since the first addition of water. S4. After mixing, pour into a mold treated with a release agent and vibrate. After solidification and demoulding, standard curing is carried out for 28 days.

2. The method for preparing concrete capable of cyclically absorbing and releasing water according to claim 1, characterized in that: The standard curing conditions in step S4 are: temperature 18-22° C., humidity ≥ 95%.

3. The method for preparing concrete capable of cyclically absorbing and releasing water according to claim 1, characterized in that: In step S2, the time interval between each addition of cement and fly ash is 20 to 40 seconds.

4. The method for preparing concrete capable of cyclically absorbing and releasing water according to claim 1, wherein: The vibration conditions are: vibration frequency 50~100Hz, vibration time 15~30s.

5. The method for preparing concrete capable of cyclically absorbing and releasing water according to claim 1, wherein: The mass ratio of added floating beads, shale sand, expanded clay, cement, fly ash, clean water and water reducing agent is 24-30:36-44:45-54:31.5-38.5:12-14:16.5-19.5:0.8-1.

2.

6. The method for preparing concrete capable of cyclically absorbing and releasing water according to claim 1, characterized in that: The particle size of the floating beads is 0.075-0.425 mm, and the water absorption rate is >35%. The shale sand is medium sand of crushed shale sand, and its crushing value is <30% and the water absorption rate is >15%. The ceramsite has a crushing value <30% and the water absorption rate is >10%.

7. The method for preparing concrete capable of cyclically absorbing and releasing water according to claim 1, characterized in that: The cement is PO42.5 cement, and the fly ash is Class II fly ash.

8. The method for preparing concrete capable of cyclically absorbing and releasing water according to claim 1, wherein: The water reducer is a polycarboxylic acid high-performance water reducer with a water reduction rate greater than 25%.

9. A concrete capable of cyclically absorbing and releasing water, characterized in that: The concrete is prepared by the method for preparing concrete capable of cyclically absorbing and releasing water according to any one of claims 1 to 8.

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