An admixture for rockfill concrete works and a method of preparation

Abstract

This application relates to an admixture for riprap concrete engineering, comprising at least the following components: a starch-dextrin retarder, an activator, a polycarboxylate thixotropic agent, and a water-reducing agent. The admixture is used to modify the workability and hardening properties of high self-compacting concrete. The mass percentages of each component are as follows: starch-dextrin retarder: 1.6%-3.5%; activator: 5.2%-21.3%; polycarboxylate thixotropic agent: 0.25%-0.90%; water-reducing agent: 75.2%-90.5%. Adding this admixture to high self-compacting concrete used in riprap concrete engineering can improve the workability of high self-compacting concrete, such as fluidity, thixotropy, and a longer initial setting time, while also providing good volume stability, good impermeability and frost resistance, and lower cement content, resulting in significant economic benefits.

Description

Technical Field

[0001] This application relates to the field of building materials, and in particular to an admixture for riprap concrete engineering and its preparation method. Background Technology

[0002] Rockfill concrete technology is a novel large-volume concrete technology, commonly used in dam construction for water conservancy and hydropower projects. It primarily consists of rockfill and high self-compacting concrete. Due to the characteristics of dam concrete, such as large single-pour volume, long pouring time, large surface area, and a wide range of void sizes (from centimeters to millimeters) formed by the rockfill, the high self-compacting concrete must possess advantages such as high fluidity, long fluidity retention time, suitable thixotropy, and a relatively long initial setting time. This ensures that the high self-compacting concrete completely fills the voids between the rockfill, forming a dense and uniform rockfill concrete and preventing cold joints.

[0003] Regarding the hardening properties of high self-compacting concrete, due to the low stress level and large structural dimensions of the dam, the design strength grade of the concrete is relatively low, typically C. 90 15 or C 90 20. However, this requires the concrete to have good volume stability. Furthermore, since dam concrete is in long-term contact with water, high self-compacting concrete needs to have good impermeability and frost resistance to ensure the dam's service life. Therefore, adding appropriate admixtures to concrete can improve its performance, resulting in significant economic and social benefits. However, existing admixture-based high self-compacting concrete cannot simultaneously achieve good workability and hardening performance, leading to lower project quality and failing to meet the requirements of high self-compacting concrete in terms of both workability and hardening performance. Summary of the Invention

[0004] To address the technical problems existing in the prior art, this application proposes an admixture for riprap concrete engineering. The admixture is used to modify the workability and hardening properties of high self-compacting concrete; it comprises at least the following components: starch-dextrin retarder, activator, polycarboxylate thixotropic agent, and water-reducing agent, with the following mass percentages for each component:

[0005]

[0006] The admixtures for riprap concrete engineering as described above further include: emulsion water absorbents, with a mass percentage of 1%-2%.

[0007] As described above, the admixture for riprap concrete engineering includes a starch dextrin retarder comprising any one or more of white dextrin and yellow dextrin, wherein the starch dextrin retarder is used to reduce the peak hydration temperature of the high self-compacting concrete.

[0008] As described above, in the admixtures used in riprap concrete engineering, when the starch dextrin-based retarder includes white dextrin and yellow dextrin, the mass ratio of white dextrin to yellow dextrin is 1:1.

[0009] The admixture for riprap concrete engineering as described above includes an activator comprising alkanolamine activators and soluble sulfate activators. The alkanolamine activators include any one or a combination of diethanolamine, triethanolamine, and triisopropanolamine. The soluble sulfate activators include any one or a combination of sodium sulfate, potassium sulfate, and ferric sulfate. The activator is used to improve the hydration efficiency of cementitious materials and reduce cement usage.

[0010] In the admixture for riprap concrete engineering as described above, when the activator includes diethanolamine, triisopropanolamine and sodium sulfate, the mass ratio of diethanolamine, isopropanolamine and sodium sulfate is 1:2:10.

[0011] As described above, the admixture for riprap concrete engineering includes, but is not limited to, any one or a combination of polycarboxylate thixotropic agents such as ammonium polycarboxylate, sodium polyacrylate, and polycarboxylate sulfonate, wherein the polycarboxylate thixotropic agent is used to adjust the thixotropic properties of the high self-compacting concrete.

[0012] The admixtures for riprap concrete engineering described above include, but are not limited to, any one or a combination of high water-reducing agents, slump-retaining agents, and slow-release agents, wherein the water-reducing agents are used to improve the fluidity of concrete.

[0013] As described above, the admixtures used in riprap concrete engineering include emulsion-type water-absorbing agents comprising: superabsorbent resin emulsions. These emulsion-type water-absorbing agents are used to reduce the difference between internal and external humidity, thereby reducing the risk of cracking and improving the concrete strength under actual curing conditions in the engineering project.

[0014] According to another aspect of this application, a method for preparing an admixture for riprap concrete engineering as described above is provided, comprising the following steps:

[0015] Using the above-mentioned components of the admixture for riprap concrete as raw materials, weigh each raw material according to the mass percentage of each component; put the weighed raw materials into the container of the mixing device and stir for 20-60 minutes to obtain the admixture for riprap concrete.

[0016] This application determines the mass percentage of each component in the admixture through experiments, thus identifying the optimal dosage of each component. Adding this admixture to high self-compacting concrete used in riprap concrete projects improves the workability of the concrete, including fluidity, thixotropy, and a longer initial setting time. It also provides good volume stability, excellent impermeability and freeze-thaw resistance, and lower cement content, resulting in significant economic benefits. Attached Figure Description

[0017] Figure 1 This is a flowchart of a method for preparing admixtures for riprap concrete engineering according to an embodiment of this application. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0019] In the following detailed description, reference can be made to the accompanying drawings, which form part of this application and illustrate specific embodiments of the present application. In the drawings, similar reference numerals describe substantially similar components in different figures. Specific embodiments of the present application are described in sufficient detail below to enable those skilled in the art to implement the technical solutions of the present application. It should be understood that other embodiments may also be utilized, or structural, logical, or electrical changes may be made to the embodiments of the present application.

[0020] In riprap concrete engineering, to balance the workability and hardening performance requirements of high self-compacting concrete, this application provides an admixture for riprap concrete engineering. This admixture enables the self-compacting concrete used in riprap concrete engineering to possess good fluidity, long fluidity retention time, suitable thixotropy, and a long initial setting time, as well as good stability, good impermeability, and freeze-thaw resistance. The admixture for riprap concrete engineering includes at least the following components: starch dextrin-based retarder, activator, polycarboxylate thixotropic agent, and water-reducing agent, with the following mass percentages for each component:

[0021]

[0022] Among them, starch dextrin-based retarders include any one or a combination of white dextrin and yellow dextrin. These retarders are used to reduce the peak hydration temperature of the riprap concrete. Using white dextrin, yellow dextrin, or a combination of both can reduce the peak hydration temperature of riprap concrete. However, the type or dosage of starch dextrin-based retarders used in high self-compacting concrete with different design requirements and raw materials from different varieties, models, and manufacturers varies slightly and should be adjusted flexibly according to the characteristics of the concrete type. Compared with general concrete structures and components, hydration temperature rise is one of the main causes of cracking in concrete dams. Since cement hydration is an exothermic reaction, adding retarders to concrete adjusts the hydration rate of some clinker minerals in the cement. Without affecting the cement hydration efficiency and the final setting time of the concrete, it prolongs the duration of the cement hydration reaction and reduces the maximum reaction rate, thereby reducing the maximum temperature rise of the concrete, reducing temperature stress, and reducing the risk of concrete cracking. According to one embodiment of this application, when the starch dextrin retarder includes white dextrin and yellow dextrin, the mass ratio of white dextrin to yellow dextrin is 1:1.

[0023] According to one embodiment of this application, the activator includes: an alkanolamine activator and a soluble sulfate activator. The alkanolamine activator includes any one or a combination of more than one of diethanolamine, triethanolamine, and triisopropanolamine. The soluble sulfate activator includes any one or a combination of more than one of sodium sulfate, potassium sulfate, and ferric sulfate. The activator is used to improve the hydration efficiency of cementitious materials and reduce cement usage. Alkanolamine activators, soluble sulfate activators, or combinations of both can improve the hydration efficiency of cementitious materials and reduce cement usage. However, the type or amount of activator used varies slightly depending on the type, model, and manufacturer of raw materials used to formulate high self-compacting concrete with different design requirements. Adjustments should be made flexibly according to the characteristics of the concrete type. Specifically, high self-compacting concrete often contains a large amount of fly ash, but due to the low cement content, approximately 50% of the fly ash activity is not utilized. Therefore, introducing active activating components into admixtures can significantly improve the reaction rate of fly ash in high self-compacting concrete, achieving a significant reduction in cement usage while maintaining the same strength, thus lowering construction costs. Furthermore, because fly ash has a lower heat of hydration and a longer reaction time than cement, reducing cement usage can further reduce the maximum temperature rise of high self-compacting concrete, lower temperature stress, and reduce the risk of concrete cracking. According to one embodiment of this application, when the activator includes diethanolamine, triisopropanolamine, and sodium sulfate, the mass ratio of diethanolamine, isopropanolamine, and sodium sulfate is 1:2:10.

[0024] According to one embodiment of this application, the polycarboxylate thixotropic agent includes any one or a combination of more than one of polyamine polycarboxylate (APAM), sodium polyacrylate (PAAM), and polycarboxylate sulfonate (PASM). The polycarboxylate thixotropic agent is used to adjust the thixotropic properties of the rubble concrete. By introducing components that alter the thixotropic properties of concrete into the admixture, the thixotropic properties of the concrete mixture can be adjusted. Polyamine polycarboxylate (APAM), sodium polyacrylate (PAAM), polycarboxylate sulfonate (PASM), or one or more combinations thereof can all adjust the thixotropic properties of the rubble concrete. However, the type or amount of polycarboxylate thixotropic agent used varies slightly depending on the type, model, and manufacturer of raw materials used to formulate high self-compacting concrete with different design requirements. It should be flexibly adjusted according to the characteristics of the concrete type. Specifically, rubble concrete projects require that the high self-compacting concrete used can both fill and compact the voids in the rubble mass and have good anti-segregation properties so that the aggregate can be evenly distributed within the concrete without settling after the concrete stops flowing. To ensure compact filling, the viscosity of the cement paste in the concrete should be minimized. However, since the density of cement paste is lower than that of sand and stone aggregates, the buoyancy produced by the cement paste is insufficient to maintain uniform aggregate distribution. Therefore, a certain degree of viscosity is required for the cement paste to ensure good anti-segregation properties of the concrete. As concrete is a fluid, it exhibits a certain shear rate during its flow and filling of voids in the riprap. This shear rate becomes zero once flow ceases. Due to the shear thinning phenomenon caused by thixotropy, the viscosity of the cement paste is inversely proportional to the shear rate. Therefore, this characteristic can be utilized by adding a thixotropic agent to the concrete to adjust its thixotropy. This causes a certain decrease in viscosity during the flow and filling process, which recovers after the concrete stops flowing, thus achieving a balance between compact filling and anti-segregation properties. Based on the above, the static segregation rate index can be used to test the thixotropy of concrete.

[0025] According to one embodiment of this application, the water-reducing agent includes any one or a combination of more than one of the following: high water-reducing agent, slump-retaining agent, and slow-release agent. The water-reducing agent is used to improve the fluidity of concrete. A water-reducing agent is a concrete admixture that can reduce the amount of mixing water while maintaining a relatively constant slump in the concrete. High water-reducing agents, slump-retaining agents, slow-release agents, or combinations thereof can all improve the fluidity of concrete. However, the type or dosage of water-reducing agent used varies slightly depending on the type, model, and manufacturer of raw materials used to formulate high self-compacting concrete with different design requirements. Adjustments should be made flexibly according to the characteristics of the concrete type. Adding a water-reducing agent disperses cement particles, improves workability, reduces unit water consumption, and improves the fluidity of the concrete mixture.

[0026] According to one embodiment of this application, when the water-reducing agent comprises a high water-reducing agent, a slump-retaining agent, and a slow-release agent, the mass ratio of the high water-reducing agent, the slump-retaining agent, and the slow-release agent is 5:36:9. According to another embodiment of this application, when the water-reducing agent comprises a high water-reducing agent and a slump-retaining agent, the mass ratio of the high water-reducing agent to the slump-retaining agent is 3:7.

[0027] According to one embodiment of this application, the emulsion-type water-absorbing agent includes a superabsorbent resin emulsion. This emulsion-type water-absorbing agent is used to reduce the risk of cracking by minimizing the difference in internal and external humidity in the early stages, thereby improving the concrete strength under actual curing conditions in engineering projects. Specifically, due to the large volume of dam concrete poured at one time, although the internal humidity can be maintained for a long time after hardening, which is beneficial to the development of concrete performance, the surface concrete is prone to rapid water loss. If curing is inadequate after pouring, the osmotic pressure caused by the difference in internal and external humidity can lead to concrete cracking. Therefore, an emulsion-type water-absorbing agent is added to the concrete. This emulsion-type water-absorbing agent contains a water-absorbing component that can absorb some of the mixing water during the mixing process. Before the concrete hardens, the moisture is locked in the water-absorbing component. When the internal humidity decreases after the concrete hardens, the water-absorbing component begins to release moisture. The rate of moisture release is proportional to the degree of dryness of the concrete, thus reducing the difference in internal and external humidity, lowering the osmotic pressure, and reducing the risk of cracking.

[0028] According to one embodiment of this application, the admixture used in riprap concrete engineering further includes: active silica, with a mass percentage of 0.5%-1%. The active silica includes: nano-silica sol, used to repair cracks in the riprap concrete. Specifically, although defects in dam concrete can be significantly reduced through seepage prevention structures, concrete mix design, and construction processes, it is still impossible to completely avoid small cracks present in hardened concrete. When water enters through these small cracks in the concrete, due to factors such as chemical erosion, freeze-thaw damage, and osmotic pressure, the cracks continuously enlarge and interconnect, ultimately leading to leakage and reduced strength in the concrete dam, affecting the dam's functionality and safety. Therefore, this application adds active silica to the concrete. The active components in the active silica can, upon contact with water, react with the hydration products in the hardened concrete and the incompletely hydrated cementitious materials to produce new hydration products, which can prevent further expansion of crack size and fill and seal defects along the seepage path, achieving self-repair.

[0029] According to one embodiment of this application, the admixture for riprap concrete engineering further includes an air-entraining agent, which has a mass percentage of 0-0.5%. The air-entraining agent includes any one or a combination of more than one of sodium α-alkenyl sulfonate and sodium dodecylbenzene sulfonate, and the air-entraining agent is used to adjust the thixotropic properties of the riprap concrete.

[0030] Figure 1 This is a flowchart illustrating a method for preparing admixtures for riprap concrete engineering according to an embodiment of this application. The method includes:

[0031] S101, using the above-mentioned components of the admixture for riprap concrete as raw materials, weigh each raw material according to the mass percentage of each component;

[0032] S102, after weighing, put all the raw materials into the container of the mixing device and mix for 20-60 minutes to obtain the admixture for riprap concrete engineering.

[0033] To determine the appropriate addition amount of each component in the admixture, this application designed multiple sets of experiments to determine the range of addition amount for each component that achieves the expected effect. Details are as follows:

[0034] Example 1

[0035] Step 1)

[0036] This application uses concrete as C. 90 Taking 20W6F50 high self-compacting concrete as an example, its self-compacting stability is required to be 1 hour, and its compressive strength should reach 25MPa or above. Specific mix proportions are shown in Table 1.

[0037] Table 1

[0038]

[0039] Adding different types and dosages of activators to the original mix proportions can improve the compressive strength of concrete. Conversely, reducing the amount of cement will decrease the compressive strength of concrete. The dosage is based on the mass percentage of the cementitious materials (cement and fly ash). Therefore, this experiment aims to reduce the amount of cement and thus lower manufacturing costs by adding different dosages of activators to the concrete while ensuring the target compressive strength is achieved. The compressive strength of concrete after 90 days of standard curing was tested after adding different types and dosages of activators to the original mix proportions. The test data are shown in Table 2. The compressive strength of concrete after 90 days of standard curing, also known as the 90-day standard curing compressive strength, refers to the compressive strength obtained by testing standard cubic specimens after 90 days of standard curing according to the "Standard for Test Methods of Physical and Mechanical Properties of Ordinary Concrete" (GB50081-2019).

[0040] Table 2

[0041]

[0042] As shown in Table 2, the experimental data indicate that experiments #2 (0.06% triethanolamine), #3 (0.06% diethanolamine), #4 (0.04% triethanolamine and 0.02% triisopropanolamine), #5 (0.04% diethanolamine and 0.02% triisopropanolamine), and #7 (0.02% diethanolamine, 0.04% triisopropanolamine, and 0.5% sodium sulfate) all improved the compressive strength of concrete, thus achieving the goal of reducing cement content. The concrete prepared using experiment #6 (0.02% diethanolamine, 0.04% triisopropanolamine, and 0.2% sodium sulfate) exhibited the highest compressive strength after 90 days of standard curing. This means that the concrete with the highest compressive strength after 90 days of standard curing was prepared when the mass ratio of diethanolamine, isopropanolamine, and sodium sulfate was 1:2:10.

[0043] Therefore, based on the mix proportion of experimental grade 6, the cement content was reduced to ensure that the 90-day standard curing strength of the concrete met C. 90 The design requirements for 20W6F50 are detailed in Table 3, along with specific experimental data.

[0044] Table 3

[0045]

[0046] As shown in Table 3, the compressive strength of concrete #8 after 90 days of standard curing is 25 MPa greater than the target compressive strength, which meets the requirements of C. 90 The strength requirement is 20W6F50. Therefore, for concrete with added activators of 0.02% diethanolamine, 0.04% triisopropanolamine, and 0.2% sodium sulfate, the dosage of cement and fly ash should refer to the experimental grade 8#. This results in a concrete mix with 15 kg / m³ less cement than the original mix design. 3 And it can achieve the required compressive strength.

[0047] Step 2)

[0048] Based on step 1), yellow dextrin and white dextrin retarders were added, and the concrete setting time and 28-day adiabatic temperature rise were tested. The test data are shown in Table 4. The 28-day adiabatic temperature rise of concrete refers to the temperature change and maximum temperature rise of concrete at 28 days of age, under conditions where the heat generated by the hydration of the cementitious materials does not exchange with the external environment. 28 days is usually chosen as the time point for measuring the adiabatic temperature rise of concrete because the hydration reaction of the concrete is usually basically completed within this period, and the temperature rise reaches its peak. The adiabatic temperature rise of concrete is an important parameter; the lower the adiabatic temperature rise, the lower the risk of cracking due to hydration temperature rise.

[0049] Table 4

[0050]

[0051] As shown in Table 4, experimental data showed that experiments 11# (0.02% yellow dextrin) and 13# (0.01% yellow dextrin and 0.01% white dextrin) were able to reduce the temperature rise. However, experiment 12# with a dosage of 0.02% white dextrin showed the most significant reduction in the 28-day adiabatic temperature rise of concrete without prolonging the concrete setting time. In other words, the reduction in the 28-day adiabatic temperature rise of concrete was most significant when the mass ratio of white dextrin to yellow dextrin was 1:1.

[0052] Step 3)

[0053] Based on step 2), thixotropic agents of different types and dosages are added. These thixotropic agents include any one or a combination of more than one of the following: ammonium polycarboxylate (APAM), sodium polyacrylate (PAAM), and polycarboxylate sulfonate (PASM). The static segregation rate of the concrete is tested; specific experimental data are shown in Table 5. The static segregation rate of concrete refers to the degree to which the materials in concrete separate or stratify during the static setting process after pouring. Typically, concrete is a composite material made of cement, aggregates, sand, water, and other admixtures. After the concrete is poured, due to its gravity and the interaction between internal particles, the materials may separate or stratify to some extent, resulting in uneven distribution of components in different locations within the concrete. Therefore, the lower the static segregation rate, the more uniform the distribution in each location.

[0054] Table 5

[0055] serial number Dispersant type Dosage Segregation rate after standing 14# - 0％ 12.7 15# APAM 0.001％ 9.2％ 16# APAM 0.003％ 6.7％ 17# PAAM 0.003％ 8.7％ 18# PAAM 0.005％ 10.1％ 19# PASM 0.005％ 9.6％ 20# PASM 0.010％ 9.4％

[0056] The data in the table above show that the segregation rate of concrete in Experiment No. 17 (0.003% PAAM) meets the requirements for thixotropy. In Experiment No. 16, the segregation rate was lowest when the PAAM content was 0.003%.

[0057] Step 4)

[0058] Based on step 3), different dosages of internal curing agent (water-absorbing emulsion) were added, and the 90-day compressive strength of concrete under standard curing and identical curing conditions was tested. Specific data are shown in Table 6. After concrete sets and hardens, as the curing period increases, the internal moisture of the concrete continuously dissipates, preventing the cementitious materials from fully undergoing hydration, thus affecting strength growth and increasing shrinkage. Utilizing the water-absorbing effect of the internal curing agent, when the internal humidity of the concrete decreases, the internal curing agent releases the absorbed water, allowing the cementitious materials in the concrete to undergo a more complete hydration reaction under actual engineering conditions. Therefore, it increases the ratio of the strength under identical curing conditions to the strength under standard curing, thereby improving the strength of the concrete structure in actual engineering projects. The 90-day compressive strength under standard curing conditions refers to the compressive strength of concrete materials after 90 days under standard curing conditions (usually a curing environment controlled by room temperature and relative humidity). The 90-day compressive strength under identical curing conditions refers to the compressive strength of a concrete cube specimen measured after 90 days under conditions similar to the actual engineering or application environment. Simultaneous curing tests aim to better simulate the performance of concrete under actual service conditions, including temperature, humidity, and other environmental factors. This type of test is typically used for special engineering projects or situations requiring more accurate prediction of concrete behavior in real-world environments. The 90-day shrinkage rate of concrete refers to the degree of shrinkage that occurs in concrete during its curing period (i.e., 90 days after pouring). Concrete undergoes volume changes during its curing period due to factors such as moisture evaporation and chemical reactions, typically manifesting as shrinkage. Adding an internal curing agent (water-absorbing emulsion) to concrete reduces volume changes caused by moisture evaporation and chemical reactions, thus decreasing the 90-day shrinkage rate.

[0059] Table 6

[0060]

[0061] As shown in Table 6, the concrete shrinkage rate decreases with the increase of the internal curing agent dosage, and the strength ratio of the cured under the same conditions to the standard curing increases. However, excessive dosage will reduce the compressive strength of the concrete (which does not meet the strength requirements of the concrete). Therefore, based on the compressive strength, the mix proportion of Experiment No. 22# is the best, with an internal curing agent dosage of 0.02%.

[0062] Step 5)

[0063] Based on step 4), experiments were conducted using high-water-reducing agent (G01), slump-retaining agent (B01), and slow-release agent (H01) to test the initial, 30-minute, and 60-minute self-compacting properties of concrete. The test data are shown in Table 7. Slump indicates the degree to which concrete collapses or caves after being dropped freely from a certain height, usually expressed in millimeters (mm). Concrete slump is used to measure the fluidity and plasticity of concrete. The V-funnel time of concrete usually refers to the time it takes for concrete to flow through a slump cone (also called a V-funnel), usually expressed in seconds (s). This test is part of the concrete slump test and is used to evaluate the fluidity and plasticity of concrete. Spread indicates the diameter of the concrete mixture after slumping, usually expressed in millimeters (mm).

[0064] Table 7

[0065]

[0066]

[0067] According to the "Technical Specifications for Cemented Granular Material Dam Construction" (SL678-2014), after 1 hour of static standing, the slump of the concrete should not change by more than ±10 mm compared to the initial value, the spread should not be less than 650 mm and not less than 95% of the initial value, and the V-shaped funnel time should be within the range of 7s to 25s. Experimental data shows that in experiment number 28#, the water-reducing agent dosage was 0.92%, of which high-water-reducing agent (G01) accounted for 10%, slump-retaining agent (B01) accounted for 72%, and slow-release agent (H01) accounted for 18%. This meets the design requirement of a 1-hour self-compacting stability time, meaning that a mass ratio of 5:36:9 for high-water-reducing agent, slump-retaining agent, and slow-release agent satisfies the 1-hour self-compacting stability requirement.

[0068] Based on the above experimental results, the dosage of each functional component in the admixture relative to the cementitious material was finally determined, as shown in Table 8.

[0069] Table 8

[0070]

[0071] The experimental data above show that the final concrete mix proportions are shown in Table 9, with a total cementitious material (cement and fly ash) content of 469 kg / m³. 3 .

[0072] Table 9

[0073]

[0074] The actual dosage of each admixture component in each cubic meter of concrete can be calculated based on the data in Tables 8 and 9. Specific data are shown in Table 10.

[0075] Table 10

[0076]

[0077] Adding the dosages of each component together yields an admixture dosage of 5.73587 kg / m³ for high self-compacting concrete. 3 Based on the admixture dosage per cubic meter of high self-compacting concrete (5.73587 kg / m³). 3 The admixture formula for riprap concrete was calculated based on the data in Table 10, as detailed in Table 11. For example, the amount of white dextrin retarder added per ton of riprap concrete is: (0.0938 / 5.73587)×1000=16.4kg / t

[0078] Table 11

[0079]

[0080]

[0081] The proportions of each component of the admixture can be obtained from Table 11. For details, please refer to Table 12.

[0082] Table 12

[0083]

[0084] Example 2

[0085] Step 1)

[0086] In one embodiment, concrete is used as C 90 Taking 15W4F100 high self-compacting concrete as an example, its self-compacting performance stability time is required to be 1 hour. The specific mix proportion is shown in Table 13.

[0087] Table 13

[0088]

[0089]

[0090] Step 2)

[0091] Different types and dosages of activators were added to the original mix proportions, and the 90-day compressive strength of the concrete was tested. The test data are shown in Table 14.

[0092] Table 14

[0093]

[0094] The experimental data in the table above show that the concrete prepared with 0.06% triethanolamine in experiment #30 exhibited the highest 90-day compressive strength. Therefore, reducing the cement content based on the mix proportion of experiment #30 will allow the concrete to meet the C standard at 90 days. 90 The design requirements for 15W4F100 are detailed in Table 15, along with specific experimental data.

[0095] Table 15

[0096]

[0097] As shown in Table 15, the compressive strength of concrete in experiment number 36# meets the C standard. 90 The 15W4F100 design requirements and the strength of the original mix proportion are similar, therefore the mix proportion with experimental number 36# is selected.

[0098] Step 3)

[0099] Based on step 2), yellow dextrin and white dextrin retarder were added, and the concrete setting time and 28-day adiabatic temperature rise were tested. The test data are shown in Table 16.

[0100] Table 16

[0101]

[0102] As shown in the experimental data in Table 16, the dosage of 0.02% white dextrin and 0.02% yellow dextrin in experiment number 40# can reduce the adiabatic temperature rise of concrete to the greatest extent without significantly prolonging the concrete setting time. That is, the mass ratio of white dextrin to yellow dextrin should be 1:1.

[0103] Step 4)

[0104] Based on step 3), different types and dosages of thixotropic agents were added, and the static segregation rate of the concrete was tested. Specific experimental data are shown in Table 17.

[0105] Table 17

[0106]

[0107]

[0108] As shown in Table 17, the concrete segregation rate was lowest when the PASM content was 0.010% in Experiment No. 47#.

[0109] Step 5)

[0110] Based on step 4), experiments were conducted using high water-reducing agent (G01), slump-retaining agent (B01), and slow-release agent (H01) to test the initial, 30-minute, and 60-minute self-compacting properties of concrete. The test data are shown in Table 18.

[0111] Table 18

[0112]

[0113]

[0114] As can be seen from the experimental data in Table 18, the concrete using two types of water-reducing agents in Experiment No. 50# can meet the design requirement of a self-compacting performance stability time of 1 hour.

[0115] Step 6)

[0116] Based on the above experimental results, the dosage of each functional component relative to the cementitious material in this project was finally determined, as shown in Table 19.

[0117] Table 19

[0118]

[0119] The final concrete mix proportions used in the above experiments are shown in Table 20. The total cementitious material content (the sum of cement and fly ash content) is 501 kg / m³. 3 .

[0120] Table 20

[0121]

[0122] The actual dosage of each component admixture in each cubic meter of concrete can be calculated based on the data in Tables 19 and 20. Specific data are shown in Table 21.

[0123] Table 21

[0124]

[0125]

[0126] Adding the dosages of each component together yields an admixture dosage of 5.7615 kg / m³ in high self-compacting concrete. 3 The admixture formula was calculated based on the admixture dosage per cubic meter of high self-compacting concrete and the data in Table 21, as detailed in Table 22.

[0127] Table 22

[0128]

[0129] The proportions of each component of the admixture can be obtained from Table 22. For details, please refer to Table 23.

[0130] Table 23

[0131]

[0132] Based on the data in Tables 12 and 23, when the mass percentage of starch dextrin-based retarder in the admixtures is 1.6%-3.5%, the mass percentage of activator is 5.2%-21.3%, the mass percentage of polycarboxylate thixotropic agent is 0.25%-0.90%, and the mass percentage of water-reducing agent is 75.2%-90.5%, it can be applied to most types of riprap concrete, improving the workability and hardening properties of riprap concrete.

[0133] In summary, adding the admixture of this application to riprap concrete can improve its workability, such as fluidity, thixotropy, and longer initial setting time, while also providing good volume stability, good impermeability and frost resistance, and lower cement content, resulting in significant economic benefits. The above embodiments are for illustrative purposes only and are not intended to limit the scope of this application. Those skilled in the art can make various changes and modifications without departing from the scope of this application; therefore, all equivalent technical solutions should also fall within the scope of this application.

Claims

1. An admixture for use in riprap concrete engineering, characterized in that, It includes at least the following components: starch dextrin-based retarder, activator, polycarboxylate thixotropic agent, and water-reducing agent. These admixtures are used to modify the workability and hardening properties of high self-compacting concrete. The mass percentages of each component are as follows: Starch-dextrin retarder: 1.6%-3.5%; Activator: 5.2%-21.3%; Polycarboxylate thixotropic agent: 0.25-0.90%; Water-reducing agent: 75.2%-90.5%; The starch dextrin-based retarder includes white dextrin and yellow dextrin, with a mass ratio of 1:

1. The starch dextrin-based retarder is used to reduce the peak hydration temperature of the high self-compacting concrete. The activator includes alkanolamine activators and soluble sulfate activators; when the activator includes diethanolamine, triisopropanolamine and sodium sulfate, the mass ratio of diethanolamine, isopropanolamine and sodium sulfate is 1:2:10; the activator is used to improve the hydration efficiency of cementitious materials and reduce the amount of cement used.

2. The admixture for riprap concrete engineering according to claim 1, characterized in that, Further includes: Emulsion-type absorbents, with a mass percentage of 1%-2%.

3. The admixture for riprap concrete engineering according to claim 1, characterized in that, The alkanolamine activator includes any one or a combination of more than one of diethanolamine, triethanolamine, and triisopropanolamine, and the soluble sulfate activator includes any one or a combination of more than one of sodium sulfate, potassium sulfate, and ferric sulfate.

4. The admixture for riprap concrete engineering according to claim 1, characterized in that, The polycarboxylate thixotropic agent comprises any one or a combination of polycarboxylate ammonium salt, sodium polyacrylate, and polycarboxylate sulfonate, and is used to adjust the thixotropic properties of the high self-compacting concrete.

5. The admixture for riprap concrete engineering according to claim 1, characterized in that, The water-reducing agent includes any one or a combination of high water-reducing agent, slump-retaining agent, and slow-release agent, and is used to improve the fluidity of concrete.

6. The admixture for riprap concrete engineering according to claim 2, characterized in that, The emulsion-type water absorbent includes: superabsorbent resin emulsion. The emulsion-type water absorbent is used to reduce the difference between internal and external humidity, reduce the risk of cracking, and improve the concrete strength under actual curing conditions in engineering.

7. A method for preparing an admixture for riprap concrete engineering as described in any one of claims 1-6, characterized in that, Includes the following steps: Using the components of the admixture for riprap concrete engineering as described in any one of claims 1-6 as raw materials, each raw material is weighed according to its mass percentage. After weighing, put all the raw materials into the container of the mixing device and mix for 20-60 minutes to obtain the admixture for use in riprap concrete projects.

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