Mechanism sand concrete design method for reducing fluidity loss over time

Abstract

The application discloses a mechanism sand concrete design method for reducing flowability loss over time, which comprises providing a first base material of concrete, compensation water and super absorbent polymer; based on the 5min spread of the mortar mixture prepared based on the first base material and the empirical water absorption of the super absorbent polymer, the estimated water absorption of the super absorbent polymer is determined through a first test; based on the estimated water absorption and the 1h spread of the second base material which is equal to the mechanism sand and replaced by natural sand, the amount of the compensation water is determined through a second test; based on the amount of the compensation water and the estimated water absorption of the super absorbent polymer, the addition amount of the super absorbent polymer in the first base material is determined; based on the addition amount of the super absorbent polymer and the amount of the compensation water, the preset mass ratio is adjusted to obtain the design ratio of the mechanism sand concrete. The application solves the problem that the water absorption of the mechanism sand in the concrete leads to high flowability loss over time of the concrete.

Description

Technical Field

[0001] This invention relates to the field of concrete preparation technology, and specifically to a design method for manufactured sand concrete that reduces fluidity loss over time. Background Technology

[0002] Appropriate fluidity of concrete mix is ​​a fundamental condition for ensuring the uniformity and compactness of concrete quality in on-site cast structures. For ready-mixed concrete, the process of transporting fresh concrete mix from the mixing plant to the construction site, unloading, pumping, and casting takes time, during which the fluidity of the mix may change. Significant loss of fluidity can create difficulties for unloading, pumping, and casting operations, thus affecting the quality of the concrete project.

[0003] Generally, the loss of fluidity in concrete over time mainly stems from two aspects: Firstly, after mixing, cement continues to react with water during transportation, consuming water; secondly, unreacted cement particles are prone to flocculation and agglomeration, trapping a significant amount of mixing water within these aggregates. This trapped water contributes nothing to fluidity. To address this issue, admixtures are typically added during concrete mixing. The functional groups of surfactants in these admixtures act on cement particles, opening up the flocculated structure and releasing the water trapped between the cement particles. Generally, admixtures can largely solve the problem of fluidity loss in ordinary concrete over time.

[0004] Sand is one of the raw materials for concrete. With the depletion of natural sand, manufactured sand has been widely used in concrete preparation. For concrete prepared with manufactured sand, there is another source of fluidity loss over time: the manufactured sand absorbs water and admixtures from the concrete mix. Due to the weathering of the parent rock of manufactured sand, the porosity of manufactured sand is often relatively high. Before the concrete mix sets and hardens, the manufactured sand continuously absorbs admixtures from the mix, causing the admixtures to enter the capillaries of the manufactured sand and fail to disperse cement particles, resulting in reduced fluidity of the mix. In particular, if the moisture content of the manufactured sand used to mix the concrete is lower than its water absorption rate, the manufactured sand will absorb water from the mix in addition to admixtures, further reducing the fluidity of the mix. Of course, natural sand also has the problem of water and admixture absorption, but the water absorption rate of natural sand is often lower, and the concrete is often already saturated before mixing. Therefore, the problem of fluidity loss over time caused by water and admixture absorption by natural sand is relatively rare. Assuming each gram of manufactured sand absorbs 0.01g of water per hour, and based on 800kg of manufactured sand per cubic meter of concrete, the cumulative water absorption per cubic meter of concrete in 1 hour can reach as high as 8kg. Coupled with the weakening effect of admixtures on dispersion, the fluidity loss of concrete mix over time can reach as high as 50mm / h, far exceeding the provision in GB50164 "Standard for Quality Control of Concrete" that "the slump loss of pumped concrete mix over time should not exceed 30mm / h", which seriously affects the application effect of concrete projects. Summary of the Invention

[0005] To overcome the shortcomings of existing technologies, a design method for manufactured sand concrete that reduces fluidity loss over time is provided to address the problem of high fluidity loss in concrete caused by water absorption of manufactured sand.

[0006] To achieve the above objectives, a design method for manufactured sand concrete that reduces fluidity loss over time is provided, comprising the following steps:

[0007] The first base material for concrete, compensating water, and a superabsorbent polymer for adding to the concrete to absorb and then slowly release the compensating water, wherein the first base material comprises cement, manufactured sand, crushed stone, admixtures, and water in a predetermined mass ratio;

[0008] Based on the 5-minute spread of the mortar mixture prepared with the first base material and the empirical water absorption capacity of the superabsorbent polymer, the estimated water absorption capacity of the superabsorbent polymer is determined through the first test. The empirical water absorption capacity is the mass of compensating water that a unit mass of the superabsorbent polymer can absorb.

[0009] Based on the estimated water absorption capacity and the 1-hour expansion of the second base material using an equal amount of natural sand to replace the manufactured sand, the amount of compensation water was determined through a second test.

[0010] Based on the amount of compensating water used and the estimated water absorption capacity of the superabsorbent polymer, the amount of superabsorbent polymer added to the first base material is determined;

[0011] Based on the amount of superabsorbent polymer added and the amount of compensating water used, the preset mass ratio is adjusted to obtain the design mix ratio of manufactured sand concrete.

[0012] Furthermore, the superabsorbent polymer is polyacrylate or acrylic-acrylamide copolymer.

[0013] Furthermore, the steps of the first test include:

[0014] The first mortar mixture is obtained by mixing the first base material according to the preset mass ratio;

[0015] Test the 5-minute spread of the first mortar mixture;

[0016] Prepare and mix the first test base material to obtain the first test mortar mixture. The first test base material includes cement, manufactured sand, crushed stone, admixture, superabsorbent polymer, compensating water and water in a first mass ratio.

[0017] Test the 5-minute spread of the first test mortar mixture;

[0018] Based on the comparison between the 5-minute spread of the first test mortar mix and the 5-minute spread of the first mortar mix, the empirical water absorption capacity of the superabsorbent polymer is adjusted so that the 5-minute spread of the first test mortar mix matches the 5-minute spread of the first mortar mix, and the adjusted empirical water absorption capacity is used as the estimated water absorption capacity of the superabsorbent polymer.

[0019] Furthermore, the steps of the second test include:

[0020] The second mortar mixture is obtained by mixing a second base material in which an equal amount of natural sand is used to replace the manufactured sand.

[0021] Test the 1-hour spread of the second mortar mixture;

[0022] Based on the first mass ratio and the estimated water absorption capacity of the superabsorbent polymer, the first mass ratio is adjusted to obtain a second mass ratio;

[0023] The second test base material is prepared and mixed according to the second mass ratio to obtain the second test mortar mixture. The second test base material includes cement, manufactured sand, crushed stone, admixture, the superabsorbent polymer, the compensating water, and water.

[0024] Test the 1-hour spread of the second test mortar mixture;

[0025] Based on the comparison between the 1-hour spread of the second test mortar mix and the 1-hour spread of the second mortar mix, the amount of compensating water is adjusted to match the 1-hour spread of the second test mortar mix with the 1-hour spread of the second mortar mix. Then, based on the adjusted amount of compensating water and the amount of superabsorbent polymer added, the preset mass ratio is adjusted to obtain the design mix ratio of manufactured sand concrete.

[0026] The beneficial effects of this invention are that the method for designing manufactured sand concrete to reduce fluidity loss over time balances the fluidity of the concrete at the time of discharge from the mixer and its fluidity after one hour, resulting in minimal fluidity loss. By adding a superabsorbent polymer to the concrete, the homogeneity of the concrete mix is ​​not affected by excessive addition of admixtures. The superabsorbent polymer does not involve chemical production and does not require contact with hazardous chemicals.

[0027] The present invention provides a method for designing manufactured sand concrete that reduces fluidity loss over time. It precisely controls the content of compensating water, preventing excessive water addition and thus maintaining the strength of the hardened concrete.

[0028] The present invention provides a design method for manufactured sand concrete that reduces fluidity loss over time. It uses the initial values ​​of the estimated water absorption capacity of superabsorbent polymer and the initial value of the compensation water amount, which are based on accumulated engineering experience, and the experimental workload is relatively small. Attached Figure Description

[0029] Other features, objects, and advantages of this application will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0030] Figure 1 This is a flowchart of a method for designing manufactured sand concrete to reduce fluidity loss over time, as described in Embodiment 1 of the present invention.

[0031] Figure 2 The following describes the loss of concrete fluidity over time in Example 1 and Comparative Example 1 of the present invention. Detailed Implementation

[0032] The present application will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, only the parts relevant to the invention are shown in the accompanying drawings.

[0033] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0034] Reference Figure 1 and Figure 2 As shown, this invention provides a design method for manufactured sand concrete that reduces fluidity loss over time, comprising the following steps:

[0035] S1. Provides a first base material for concrete, compensating water, and a superabsorbent polymer for adding to the concrete to absorb and slowly release compensating water. The first base material includes cement, manufactured sand, crushed stone, water, and admixtures in a preset mass ratio.

[0036] In this embodiment, the ratio of cement:mineral admixture:manufactured sand:crushed stone:water:admixture in the first base material is C:K:S:G:W:A.

[0037] In this embodiment, the superabsorbent polymer is polyacrylate or acrylic-acrylamide copolymer. A superabsorbent polymer is a polymeric material capable of absorbing tens to hundreds of times its own weight in water. Superabsorbent polymers consist of a network structure formed by the cross-linking of multiple polymer chains. Upon contact with water or solution, they absorb water and swell under various physical influences (primarily osmotic pressure); in dry environments or in highly concentrated solutions, they release water and shrink.

[0038] When the superabsorbent polymer is pre-mixed evenly with cement, and then water is added, the superabsorbent polymer and cement come into contact with water simultaneously. At this point, the ion concentration of the liquid in contact with the superabsorbent polymer is still very low (the cement has not yet had time to dissolve), allowing the superabsorbent polymer to fully absorb water. As the cement dissolves and the ion concentration and pH value of the resulting solution continuously increase, the superabsorbent polymer gradually releases water.

[0039] The water absorption capacity of superabsorbent polymers (SAP) is affected by their manufacturing process and the mineral composition of the cement. The water absorption capacity X of an SAP is typically expressed as the mass of water that 1g of SAP can absorb.

[0040] The water absorption capacity X of the superabsorbent polymer is the ratio between the amount of superabsorbent polymer used P and the amount of compensating water used H (dimensionless).

[0041] In this embodiment, the purpose of the superabsorbent polymer is to release water, and the amount released is approximately the same as the amount of water absorbed by the manufactured sand. The amount of superabsorbent polymer used is 0.025% to 0.125% of the total weight of the first base material.

[0042] S2. Based on the 5-minute spread α0 of the mortar mixture prepared with the first base material and the empirical water absorption capacity of the superabsorbent polymer, the estimated water absorption capacity of the superabsorbent polymer is determined through the first test. The empirical water absorption capacity is the mass of compensating water that a unit mass of superabsorbent polymer can absorb.

[0043] Furthermore, the steps of the first experiment in step S2 include:

[0044] S21. The first mortar mixture is obtained by mixing the first base material according to the preset mass ratio;

[0045] S22. Test the 5-minute spread α0 of the first mortar mixture;

[0046] S23. Prepare the first test base material and mix it to obtain the first test mortar mixture. The first test base material includes cement, manufactured sand, crushed stone, admixture, superabsorbent polymer, compensating water and water in a first mass ratio.

[0047] S24. Test the 5-minute spread of the first test mortar mixture;

[0048] S25. Based on the comparison between the 5-minute spread of the first test mortar mix and the 5-minute spread of the first mortar mix, adjust the empirical water absorption capacity of the superabsorbent polymer to match the 5-minute spread of the first test mortar mix with the 5-minute spread of the first mortar mix, and use the adjusted empirical water absorption capacity as the estimated water absorption capacity of the superabsorbent polymer.

[0049] S3. Based on the estimated water absorption capacity and the 1-hour expansion of the second base material using an equal amount of natural sand to replace manufactured sand, the amount of compensation water is determined through a second test.

[0050] Furthermore, the second test in step S3 includes the following steps:

[0051] S31. The second base material, which uses natural sand to replace the manufactured sand in equal amounts, is mixed to obtain the second mortar mixture;

[0052] S32. Test the 1-hour spread β0 of the second mortar mixture;

[0053] S33. Based on the first mass ratio and the estimated water absorption capacity of the superabsorbent polymer, adjust the first mass ratio to obtain the second mass ratio;

[0054] S34. Prepare the second test base material according to the second mass ratio and mix to obtain the second test mortar mixture. The second test base material includes cement, manufactured sand, crushed stone, admixture, superabsorbent polymer, compensating water and water.

[0055] S35. Test the 1-hour spread of the second test mortar mixture;

[0056] S36. Based on the comparison of the 1-hour spread of the second test mortar mix with the 1-hour spread of the second mortar mix, adjust the amount of compensating water to match the 1-hour spread of the second test mortar mix with the 1-hour spread of the second mortar mix.

[0057] S4. Based on the amount of compensating water and the estimated water absorption capacity of the superabsorbent polymer, determine the amount of superabsorbent polymer to be added to the first base material.

[0058] S5. Based on the amount of superabsorbent polymer added and the amount of compensating water used, adjust the preset mass ratio to obtain the design mix ratio of manufactured sand concrete.

[0059] Taking a total weight of 2000g for cement, manufactured sand, crushed stone, water, and admixtures as an example, the present invention's method for designing manufactured sand concrete to reduce fluidity loss over time includes the following steps:

[0060] S10, providing a first base material for concrete, compensating water, and a superabsorbent polymer for adding to the concrete to absorb and re-release compensating water, the first base material comprising cement, manufactured sand, crushed stone, water, and admixtures in a predetermined mass ratio.

[0061] The preset mass ratio of cement, manufactured sand, crushed stone, water, and admixtures in the first base material is C:K:S:G:W:A. The total weight of the first base material is 2000g. The superabsorbent polymer is prepared according to the preset ratio of the first base material, and is 1.5g.

[0062] S20. Based on the 5-minute spread α0 of the mortar mixture prepared with the first base material and the empirical water absorption capacity of the superabsorbent polymer, the estimated water absorption capacity of the superabsorbent polymer is determined through the first test. The empirical water absorption capacity is the mass of compensating water that a unit mass of superabsorbent polymer can absorb.

[0063] Specifically, S201, the first mortar mixture is obtained by mixing the first base material according to the preset mass ratio.

[0064] The first mortar mix is ​​a cement mortar without the addition of superabsorbent polymer. The total weight of the first mortar mix is ​​2000g, and all raw materials are in the same proportion as the concrete mix, namely: cement 2000C / (C+K+S+W+A), mineral admixtures 2000K / (C+K+S+W+A), manufactured sand 2000S / (C+K+S+W+A), and water 2000W / (C+K+S+W+A), in grams.

[0065] S202, Test the 5-minute spread α0 of the first mortar mixture.

[0066] After thoroughly mixing the cement, mineral admixtures, and manufactured sand, add water and mix slowly for 3 minutes using a planetary mixer. Let it stand for 1 minute, scraping off any material adhering to the inner wall of the pot and adding it back in. Finally, mix at high speed for 1 minute. Remove the mixed mortar and test its spread, recording it as α0 (unit: mm). The above operations must be performed at an environment of 20±2℃.

[0067] S203. Prepare and mix the first test base material to obtain the first test mortar mixture. The first test base material includes cement, manufactured sand, crushed stone, admixture, superabsorbent polymer, compensating water and water in a first mass ratio.

[0068] S204. Test the 5-minute spread of the first test mortar mixture.

[0069] After thoroughly mixing cement, mineral admixtures, manufactured sand, and superabsorbent polymer, water is added. The mixture is then slowly stirred for 3 minutes using a planetary mixer, followed by a 1-minute settling period. During this settling period, any material adhering to the inner wall of the pot is scraped off and added back into the pot. Finally, the mixture is stirred at high speed for 1 minute. The resulting mortar mixture is then removed and its spread is tested, recorded as α1 (unit: mm). The above operations must be performed at an environment of 20±2℃.

[0070] S205. Based on the comparison of the 5-minute spread of the first test mortar mix with the 5-minute spread of the first mortar mix, adjust the empirical water absorption capacity of the superabsorbent polymer to achieve a 5-minute spread α of the first test mortar mix. i (i = 1, 2, 3...) (i.e., the 5-minute spread of the i-th first test mortar mix) is matched with the 5-minute spread α0 of the first mortar mix, and the adjusted empirical water absorption is used as the estimated water absorption of the superabsorbent polymer.

[0071] The first experimental mortar mixture was a cement mortar with added superabsorbent polymer and compensating water. The amounts of cement, mineral admixtures, manufactured sand, additives, and water were the same as those in the first mortar mixture, with the superabsorbent polymer dosage being 1.5g and the compensating water dosage being 1.5X. i The water in the first test mortar mixture includes the water from the original first base material and the compensation water, which is 2000W / (C+K+S+W+A)+1.5X. i The unit is grams, where X i (i = 1, 2, 3…) represents the estimated water absorption capacity of the superabsorbent polymer in the i-th test mortar mix. Based on extensive practical experience, the estimated water absorption capacity X… i The initial value of X1 is 30.

[0072] Between the adjusted first test mortar mixtures (1-i), the amount of superabsorbent polymer remained constant, while the amount of water was used to compensate for the change.

[0073] Based on α0 and α i The relationship can be divided into three cases:

[0074] ①If |α0–α i If |<5mm, then the 5-minute spread of the first mortar mix is ​​basically the same as that of the first test mortar mix.

[0075] ②If |α0–α i |≥5mm and α i >α0, indicating that X i If the value is too large, adjust the first test mortar mix (Group 2) starting with X. i Reduce the amount by 2 (X2 = 28) compared to the previous group, and repeat the above steps of water consumption calculation, stirring, and expansion test until |α0 – α i | up to 5mm.

[0076] ③If |α0–α i |≥5mm and α i <α0, indicating that X i If the value is too small, then start with the adjusted first test mortar mix (Group 2), X i Increase by 2 (X2 = 30) compared to the previous group, and repeat the above steps of water consumption calculation, stirring, and expansion test until |α0 – α i | up to 5mm.

[0077] The water absorption rate of the last group of first test mortar mixes is estimated to be the water absorption capacity of the superabsorbent polymer, i.e., X = X i .

[0078] S30. Based on the estimated water absorption capacity and the 1-hour expansion of the second base material using an equal amount of natural sand to replace manufactured sand, the amount of compensating water is determined through a second test.

[0079] Specifically, the steps of the second experiment in step S3 include:

[0080] S301. The second base material, which uses natural sand to replace the manufactured sand in equal amounts, is mixed to obtain the second mortar mixture.

[0081] The second base material is cement mortar made with natural sand (replacing the manufactured sand in the first base material in equal amounts) and without superabsorbent polymers or compensating water. The total weight of all raw materials is 2000g, and all raw materials are mixed in the same proportion as the concrete, namely: cement 2000C / (C+K+S+W+A), mineral admixtures 2000K / (C+K+S+W+A), natural sand 2000S / (C+K+S+W+A), and water 2000W / (C+K+S+W+A), in grams.

[0082] S302, Test the 1-hour spread β0 of the second mortar mixture.

[0083] After thoroughly mixing cement, mineral admixtures, and natural sand, add water and mix slowly for 3 minutes using a planetary mixer. Let it stand for 1 minute, scraping off any material adhering to the inner wall of the container and adding it back in. Then mix at high speed for 1 minute. Afterward, mix slowly for 20 seconds every 5 minutes. After the 11th 20-second slow mixing cycle, remove the mixed mortar and test its spread, recording it as β0 (unit: mm). The above operations must be performed at 20±2℃. When not mixing, the container should be covered to prevent moisture exchange with the outside environment.

[0084] From the addition of water to the completion of the 11th slow stirring for 20 seconds, the time taken is 3 + 1 + 1 + 5 × 11 = 60 min = 1 h.

[0085] S303. Based on the first mass ratio and the estimated water absorption capacity of the superabsorbent polymer, adjust the first mass ratio to obtain the second mass ratio.

[0086] S304. Prepare the second test base material according to the second mass ratio and mix to obtain the second test mortar mixture. The second test base material includes cement, manufactured sand, crushed stone, admixture, superabsorbent polymer, compensating water and water.

[0087] S305. Test the 1-hour spread of the second test mortar mixture.

[0088] For the second test mortar mixture, cement, mineral admixtures, manufactured sand, and superabsorbent polymer were mixed evenly. Water was then added, and the mixture was first slowly stirred for 3 minutes using a planetary mixer, followed by a 1-minute settling period. During the settling period, any material adhering to the inner wall of the pot was scraped off and added back into the pot. Finally, the mixture was stirred at high speed for 1 minute. Thereafter, slow stirring for 20 seconds was performed every 5 minutes. After the 11th 20-second slow stirring cycle, the mixed mortar mixture was removed, and its spread was tested and recorded as β1 (unit: mm). The above operations must be conducted at an environment of 20±2℃.

[0089] S306. Based on the comparison of the 1-hour spread of the second test mortar mix with that of the second mortar mix, adjust the amount of compensating water to make the 1-hour spread β of the second test mortar mix... j (j=1,2,3…)(i.e., the 1h spread of the j-th second test mortar mix) matches the 1h spread β0 of the second mortar mix.

[0090] Based on β0 and β j The relationship can be divided into three cases:

[0091] ①If |β0–β j If the expansion is less than 5mm, the control group and the experimental group are considered to have basically the same expansion.

[0092] ②If |β0–βj |≥5mm and β j The value >β0 indicates that the amount of compensating water h1 is too large. The amount of compensating water h1 in the second test mortar mixture should be adjusted. j Reduce the amount of compensating water in the second test mortar mix by 4 grams compared to the amount before adjustment, and repeat the above steps of water calculation, mixing, and spread test until |β0–β j | up to 5mm.

[0093] ③If |β0–β j |≥5mm and β j <β0, indicating h j If the amount is too small, then starting from the second test mortar mix after adjustment, compensate for the water usage h. j Increase the water content by 4 grams compared to the second test mortar mix before adjustment, and repeat the above steps of water calculation, mixing, and spread test until |β0–β j | up to 5mm.

[0094] The second mortar mix was a cement mortar using manufactured sand, with added superabsorbent polymer and compensating water. The amounts of cement, mineral admixtures, and manufactured sand were the same as those in the second experimental mortar mix. The amount of compensating water h in the j-th (j=1,2,3…) experimental group was the same. j The amount of superabsorbent polymer used in the j-th experimental group is h. j / X, the total amount of water (including compensation water) is 2000W / (C+K+S+W)+h j The unit is grams. Where X is the water absorption rate of the superabsorbent polymer obtained in the first step.

[0095] Based on extensive experience, the estimated compensation water consumption h j The initial value h1 is taken as 2000pS / (C+K+S+W), in grams. The p value represents the water absorption rate of the manufactured sand over 1 hour, and is dimensionless. Table 1 summarizes the common p values ​​for manufactured sand based on extensive experience.

[0096] Table 1. Water absorption rate (p) of common manufactured sand in 1 hour

[0097] Pebble manufactured sand 0.006 Limestone manufactured sand 0.012 Granite manufactured sand 0.018

[0098] The amount of superabsorbent polymer and compensating water in the second test mortar changed before and after the adjustment, but the ratio of the two remained the same.

[0099] S40. Based on the amount of compensating water and the estimated water absorption capacity of the superabsorbent polymer, determine the amount of superabsorbent polymer to be added to the first base material.

[0100] S50. Based on the amount of superabsorbent polymer added and the amount of compensating water used, adjust the preset mass ratio to obtain the design mix ratio of manufactured sand concrete.

[0101] The amount of compensating water used in the second base material h j The additional water content H in the concrete is calculated based on the mix proportion, i.e., H = h. j (C+K+S+W) / 2000;

[0102] The amount of superabsorbent polymer used is P = H / X.

[0103] The adjusted mix proportion is: Cement: Mineral admixtures: Manufactured sand: Crushed stone: Total water: Superabsorbent polymer: Additives = C:K:S:G:(W+H):P:A.

[0104] Concrete flowability is generally measured by slump or spread. The test method for spread is in accordance with GB / T 50080-2016 Standard for Test Methods of Performance of Ordinary Concrete Mixtures.

[0105] In this embodiment, the method for testing the spreadability of the mortar mixture refers to GB / T 2419-2005 "Method for Determination of Flowability of Cement Mortar".

[0106] Furthermore, in this embodiment, both the first and second test mortar mixtures are made of mortar. This eliminates the influence of coarse aggregate, resulting in more accurate and repeatable results; it also offers convenience and speed. The spreadability of the mortar in both the first and second test mortar mixtures can be used as an evaluation index.

[0107] To further illustrate the technical effects of the design method for manufactured sand concrete that reduces fluidity loss over time according to the present invention, the following examples and comparative examples are provided for comparison.

[0108] Comparative Example 1

[0109] The raw material usage for concrete is shown in Table 2 below (unit: kg). Among them, the manufactured sand is granite manufactured sand, and the water absorption rate in 1 hour is unknown.

[0110] Table 2. Concrete raw material usage for Comparative Example 1

[0111] cement fly ash Manufactured sand gravel water admixtures 420 30 785 1060 150 4.2

[0112] Concrete was prepared using this mix proportion. The slump change over time, starting from the moment water was added and mixing, is shown in Table 3 below.

[0113] Table 3. Changes in slump of concrete in Comparative Example 1 over time.

[0114] Time (min) 5 15 30 45 60 Slump (mm) 173 172 163 147 118

[0115] Example 1

[0116] Step S1: The following is the amount of raw materials used in the concrete (unit: kg). The slump at the mixer is good, but the subsequent losses are significant. The sand is manufactured granite sand, and the water absorption rate after 1 hour is unknown.

[0117] Table 4. Concrete raw material usage in Example 1

[0118] cement fly ash Manufactured sand gravel water admixtures 420 30 785 1060 150 4.2

[0119] In this embodiment, the mineral admixture in the first base material is fly ash. The C:K:S:G:W ratio of the first base material is 420:30:785:1060:150.

[0120] The dosage of each material in the first base material control group is shown in Table 5 below (unit: grams):

[0121] Table 5. Amounts of each material in the first base material control group in Example 1

[0122]

[0123] The measured spread of the first mortar mix over 5 minutes was α0 = 184 mm.

[0124] Step S2: The quantities of each material in the first test mortar mix of the first group are shown in Table 6 below (unit: grams):

[0125] Table 6. Material quantities of the first test mortar mixture in the first group of Example 1

[0126]

[0127] The measured 5-minute spread of the first test mortar mixture in the first group was α1 = 191 mm, and α1 – α0 = 7 mm > 5 mm, so test group 2 needs to be prepared.

[0128] The quantities of each material in the first experimental mortar mixture of the second group are shown in Table 7 below (unit: grams):

[0129] Table 7. Material quantities of the first test mortar mixture in the second group.

[0130]

[0131] The measured 5-minute spread of the first test mortar mixture in the second group was α2 = 187 mm, α2 – α0 = 3 mm < 5 mm, indicating the end of step S2. X = 28.

[0132] Step S3: The amounts of each material in the second mortar mix (as shown in Table 8 below) are the same as those in the control group of Step 1, except that the manufactured sand is replaced with an equal amount of natural sand (unit: grams).

[0133] Table 8. Material quantities of the second mortar mixture in Example 1

[0134]

[0135] The measured spread β0 of the control group was 180 mm after 1 hour.

[0136] The second test mortar mix for Group 1: From the table, p = 1.8. The quantities of each material in the second test mortar mix for Group 1 are shown in Table 9 (unit: grams):

[0137] Table 9. Material quantities of the second test mortar mixture in Group 1

[0138]

[0139] The measured 1-hour spread β0 of the second test mortar mixture in the first group was 182 mm. Since |β2–β0| = 2 mm < 5 mm, there is no need to conduct the second test mortar mixture in the second group.

[0140] Step S4: The compensation water usage H = H1(C+K+S+W) / 2000 = 14.4;

[0141] Total water volume W + H = 150 + 14.4 = 164.4;

[0142] The amount of superabsorbent polymer used is P = H / X = 14.4 / 28 = 0.514.

[0143] Step S5: The adjusted mixing ratio is:

[0144] Cement: Mineral admixtures: Manufactured sand: Crushed stone: Total water: Superabsorbent polymer: Admixture = C:K:S:G:(W+H):P:A = 420:30:785:1060:164.4:0.514:4.2.

[0145] Concrete was prepared using the adjusted mix proportions, and the slump change over time was shown in Table 10 below, with the moment of adding water and mixing as the starting point.

[0146] Table 10. Changes in slump of concrete prepared with the adjusted mix proportion in Example 1 over time.

[0147] Time (min) 5 15 30 45 60 Slump (mm) 170 170 165 164 161

[0148] The slump loss over time for the comparative examples and embodiments is as follows: Figure 2 As shown.

[0149] In this embodiment, step S1 involves one control group and two experimental groups; step S2 involves one control group and one experimental group. Since step S2 can be performed simultaneously on both the control and experimental groups, the comparison takes an additional (1+2)×5+(1+1)×5+1×55=80 minutes.

[0150] This invention relates to a method for designing manufactured sand concrete that reduces fluidity loss over time, balancing the fluidity of the concrete upon discharge from the mixer and after one hour. By adding a superabsorbent polymer to the concrete, the homogeneity of the concrete mix is ​​not affected by excessive admixture addition. The superabsorbent polymer is not involved in chemical production and does not require contact with hazardous chemicals.

[0151] The present invention provides a method for designing manufactured sand concrete that reduces fluidity loss over time. It precisely controls the content of compensating water, preventing excessive water addition and thus maintaining the strength of the hardened concrete.

[0152] The present invention provides a design method for manufactured sand concrete that reduces fluidity loss over time. It uses the initial values ​​of the estimated water absorption capacity of superabsorbent polymer and the initial value of the compensation water amount, which are based on accumulated engineering experience. This method allows the spread of the test mortar to quickly approach that of the control group with less work, and the amount of experimental work is relatively small.

[0153] The above description is merely a preferred embodiment of this application and an explanation of the technical principles employed. Those skilled in the art should understand that the scope of the invention involved in this application is not limited to technical solutions formed by specific combinations of the above-described technical features, but should also cover other technical solutions formed by arbitrary combinations of the above-described technical features or their equivalents without departing from the inventive concept. For example, technical solutions formed by substituting the above features with (but not limited to) technical features with similar functions disclosed in this application.

Claims

1. A design method for manufactured sand concrete that reduces fluidity loss over time, characterized in that, Includes the following steps: The first base material for concrete, compensating water, and a superabsorbent polymer for adding to the concrete to absorb and then slowly release the compensating water, wherein the first base material comprises cement, manufactured sand, crushed stone, admixtures, and water in a predetermined mass ratio; Based on the 5-minute spread of the mortar mixture prepared with the first base material and the empirical water absorption capacity of the superabsorbent polymer, the estimated water absorption capacity of the superabsorbent polymer is determined through the first test. The empirical water absorption capacity is the mass of compensating water that a unit mass of the superabsorbent polymer can absorb. Based on the estimated water absorption capacity and the 1-hour expansion of the second base material using an equal amount of natural sand to replace the manufactured sand, the amount of compensation water was determined through a second test. Based on the amount of compensating water used and the estimated water absorption capacity of the superabsorbent polymer, the amount of superabsorbent polymer added to the first base material is determined; Based on the amount of superabsorbent polymer added and the amount of compensating water used, the preset mass ratio is adjusted to obtain the design mix ratio of manufactured sand concrete.

2. The method for designing manufactured sand concrete to reduce fluidity loss over time according to claim 1, characterized in that, The superabsorbent polymer is polyacrylate or acrylic-acrylamide copolymer.

3. The method for designing manufactured sand concrete to reduce fluidity loss over time according to claim 1, characterized in that, The steps of the first test include: The first mortar mixture is obtained by mixing the first base material according to the preset mass ratio; Test the 5-minute spread of the first mortar mixture; Prepare and mix the first test base material to obtain the first test mortar mixture. The first test base material includes cement, manufactured sand, crushed stone, admixture, superabsorbent polymer, compensating water and water in a first mass ratio. Test the 5-minute spread of the first test mortar mixture; Based on the comparison between the 5-minute spread of the first test mortar mix and the 5-minute spread of the first mortar mix, the empirical water absorption capacity of the superabsorbent polymer is adjusted so that the 5-minute spread of the first test mortar mix matches the 5-minute spread of the first mortar mix, and the adjusted empirical water absorption capacity is used as the estimated water absorption capacity of the superabsorbent polymer.

4. The method for designing manufactured sand concrete to reduce fluidity loss over time according to claim 1, characterized in that, The steps of the second test include: The second mortar mixture is obtained by mixing a second base material in which an equal amount of natural sand is used to replace the manufactured sand. Test the 1-hour spread of the second mortar mixture; Based on the first mass ratio and the estimated water absorption capacity of the superabsorbent polymer, the first mass ratio is adjusted to obtain a second mass ratio; The second test base material is prepared and mixed according to the second mass ratio to obtain the second test mortar mixture. The second test base material includes cement, manufactured sand, crushed stone, admixture, the superabsorbent polymer, the compensating water, and water. Test the 1-hour spread of the second test mortar mixture; Based on the comparison between the 1-hour spread of the second test mortar mix and the 1-hour spread of the second mortar mix, the amount of compensating water is adjusted to match the 1-hour spread of the second test mortar mix with the 1-hour spread of the second mortar mix. Then, based on the adjusted amount of compensating water and the amount of superabsorbent polymer added, the preset mass ratio is adjusted to obtain the design mix ratio of manufactured sand concrete.

Images