Mass concrete composition

Abstract

This application discloses a mass concrete composition relating to the field of concrete, which is prepared from the following components in parts by weight: 200-400 parts coarse aggregate; 50-80 parts fine sand; 60-90 parts cement; 28-38 parts water; 2-6 parts water-reducing agent; 10-20 parts slow-release quicklime; and 5-15 parts additives; wherein the additives are selected from one or two of zinc sulfate heptahydrate and borax decahydrate. This application has the effects of reducing the autogenous shrinkage rate of mass concrete, reducing cracks, and improving the compressive strength of mass concrete.

Description

Technical Field

[0001] This application relates to the field of concrete, and in particular to a mass concrete composition. Background Technology

[0002] Mass concrete refers to the concrete used in modern building construction, such as foundations and dams, where the volume of concrete used is large. Due to the large volume of construction, during the solidification process, the hydration of cement causes heat to concentrate inside the mass concrete and is not easily dissipated, resulting in a large temperature difference between the inside and outside of the concrete, which leads to cracks in the concrete.

[0003] Currently, in order to alleviate the heat concentration phenomenon during the solidification of large-volume concrete as much as possible, cement with low heat of hydration and long setting time is often used, such as medium-heat silicate cement, low-heat slag silicate cement, dam cement, and slag silicate cement.

[0004] However, cement with low heat of hydration has a greater tendency to release water, which causes a large amount of water to seep from the inside to the surface during the solidification process of large-volume concrete. This increases the shrinkage rate of large-volume concrete. On the one hand, this reduces the bond strength of large-volume concrete. On the other hand, the reduction in water content results in incomplete curing of some cement inside the concrete. Under the combined effect of this and the concentrated heat inside the large-volume concrete, the large-volume concrete has low compressive strength, high autogenous shrinkage rate, and is prone to cracking. Summary of the Invention

[0005] In order to improve the problems of low compressive strength, high autogenous shrinkage rate and easy cracking of mass concrete, this application provides a mass concrete composition.

[0006] The mass concrete composition provided in this application adopts the following technical solution:

[0007] A mass concrete composition is prepared from the following components in parts by weight:

[0008] 200-400 parts coarse aggregate;

[0009] 50-80 parts fine sand;

[0010] 60-90 parts cement;

[0011] 28-38 parts water;

[0012] 2-6 parts water-reducing agent;

[0013] 10-20 parts slow-release quicklime;

[0014] Additives 5-15 parts;

[0015] The additive is selected from one or both of zinc sulfate heptahydrate and borax decahydrate.

[0016] By adopting the above technical solution, cement and slow-release quicklime are used as gelling materials to bond coarse aggregate and fine sand. Combined with a water-reducing agent, the amount of mixing water is reduced. During the solidification of mass concrete, the cement hydrates, bonding and initially shaping the coarse and fine aggregates. Simultaneously, the heat generated by cement hydration raises the internal temperature of the mass concrete. The additive absorbs heat, causing the bound water to separate and combine with unreacted cement. This alleviates heat concentration within the mass concrete and allows the incompletely reacted cement to bond the coarse aggregate and fine sand. Furthermore, as the mass concrete solidifies, the slow-release quicklime gradually releases and combines with water to further bond the coarse aggregate and fine sand. This minimizes the rapid increase in internal heat during solidification. The combined effect reduces the autogenous shrinkage rate of the mass concrete, decreases cracking, and increases its compressive strength.

[0017] Optionally, the slow-release quicklime can be prepared as follows:

[0018] Polyvinyl alcohol, dispersant and quicklime are mixed and ball-milled to obtain slow-release quicklime.

[0019] Preferably, in the slow-release quicklime, the weight ratio of quicklime to polyvinyl alcohol is (15-30):1.

[0020] Preferably, the weight ratio of the polyvinyl alcohol to the dispersant is 1:(0.4-0.6).

[0021] Preferably, the dispersant is selected from one or both of glycerol and saturated fatty acids.

[0022] Preferably, the degree of polymerization of the polyvinyl alcohol is 500-2400.

[0023] Preferably, the mixing process includes: first premixing polyvinyl alcohol and a dispersant to obtain a premix, and then mixing the premix with quicklime.

[0024] By adopting the above technical solution and controlling the ratio of polyvinyl alcohol (PVA) to quicklime and the ratio of PVA to dispersant, a water-soluble layer of PVA is formed on the surface of quicklime. During the solidification of mass concrete, the PVA on the surface of quicklime gradually dissolves. As the heat generated during the solidification process of mass concrete increases, the internal temperature of the mass concrete rises, and the dissolution rate of PVA gradually accelerates. This delays the bonding time of quicklime to coarse aggregate and fine sand, alleviating the damage caused by heat concentration in mass concrete and reducing the cracking rate. Furthermore, by adjusting the degree of polymerization of PVA and the gelation of PVA in water under the action of borax decahydrate, a network structure is formed inside the mass concrete, which plays a role in filling gaps, supporting and buffering, reducing the autogenous shrinkage rate of mass concrete and increasing its compressive strength. Under the combined effect, the autogenous shrinkage rate of mass concrete is reduced, cracks are reduced, and the compressive strength of mass concrete is increased.

[0025] Optionally, the weight ratio of the slow-release quicklime to the additive is 1:(0.25-1.5).

[0026] Preferably, the additive is composed of zinc sulfate heptahydrate and borax decahydrate in a weight ratio of (0.25-4):1.

[0027] Preferably, the water-reducing agent is selected from one or more of polycarboxylate-based water-reducing agents, naphthalene-based water-reducing agents, aminosulfonate-based water-reducing agents, aliphatic-based water-reducing agents, and lignin cycloalkanes.

[0028] By adopting the above technical solution, and by controlling the ratio of slow-release quicklime to additives and the composition and ratio of additives, while reducing the amount of mixing water by using water-reducing agents, the polyvinyl alcohol on the surface of the slow-release quicklime is dissolved during the solidification and heating process of the large-volume concrete, and water is slowly supplied to the quicklime and unhydrated cement. Under the action of borax decahydrate, the dissolved polyvinyl alcohol gels. Under the combined effect, the autogenous shrinkage rate of the large-volume concrete is reduced, cracks are reduced, and the compressive strength of the large-volume concrete is improved.

[0029] In summary, this application includes at least one of the following beneficial technical effects:

[0030] 1. At the same time, the heat generated by the hydration of cement causes the internal temperature of the large-volume concrete to rise. The additive absorbs heat, causing the bound water to separate and combine with the unreacted cement. On the one hand, this alleviates the heat concentration inside the large-volume concrete, and on the other hand, it allows the incompletely reacted cement to hydrate and bind the coarse aggregate and fine sand. Meanwhile, as the large-volume concrete solidifies, the slow-release quicklime is gradually released and combines with water to further bind the coarse aggregate and fine sand.

[0031] 2. Polyvinyl alcohol on the surface of quicklime gradually dissolves, and as the heat generated during the solidification process of mass concrete increases, the internal temperature of the mass concrete rises, and the dissolution rate of polyvinyl alcohol gradually accelerates. This delays the bonding time of quicklime with coarse aggregate and fine sand, alleviating the damage caused by heat concentration in mass concrete and reducing the cracking rate. Furthermore, by adjusting the degree of polymerization of polyvinyl alcohol and the gelation of polyvinyl alcohol in water under the action of borax decahydrate, a network structure is formed inside the mass concrete, which plays a role in filling gaps, supporting and buffering, reducing the autogenous shrinkage rate of the mass concrete and improving its compressive strength.

[0032] 3. By controlling the ratio of slow-release quicklime to additives and the composition and proportion of additives, and by reducing the amount of mixing water by using water-reducing agents, the polyvinyl alcohol on the surface of slow-release quicklime is dissolved during the solidification and heating process of large-volume concrete, and water is slowly supplied to quicklime and unhydrated cement. Under the action of borax decahydrate, the dissolved polyvinyl alcohol gels. Attached Figure Description

[0033] Figure 1 This is a flowchart of the preparation steps of slow-release quicklime in this application.

[0034] Figure 2 yes Figure 1 The flowchart for step S1. Detailed Implementation

[0035] The present application will be further described in detail below with reference to the embodiments. The following embodiments are for illustrative purposes only and should not be considered as limiting the scope of the invention. Unless otherwise specified, specific conditions in the following embodiments were performed under conventional conditions or conditions recommended by the manufacturer. Unless otherwise specified, the methods used are conventional methods known in the art, and the consumables and reagents used are commercially available. Unless otherwise stated, the technical and scientific terms used herein have the same meaning as those familiar to those skilled in the art. Furthermore, any methods or materials similar to or equivalent to those described herein may also be applied to the present invention.

[0036] All raw materials used in the examples are commercially available. The coarse aggregate is continuously graded stone, the cement is low-heat silicate cement, and the water-reducing agent is a polycarboxylate-based water-reducing agent.

[0037] Examples 1-9

[0038] Examples 1-9 provide a large-volume concrete composition, the composition and formulation of which are shown in Table 1.

[0039] The slow-release quicklime preparation methods in Examples 1-9 are as follows:

[0040] S1. Mixing: Mix 1 part by weight of polyvinyl alcohol, 0.5 parts by weight of glycerol and 20 parts by weight of quicklime to obtain a mixture.

[0041] S2. Ball milling: Add the mixture to a ball mill and mill it evenly to obtain slow-release quicklime.

[0042] The polyvinyl alcohol used in Examples 1-9 to prepare slow-release quicklime has a degree of polymerization of 500 and a degree of alcoholysis of 88%.

[0043] Table 1: Composition and proportions of mass concrete compositions

[0044]

[0045] Example 10

[0046] Example 10 provides a large-volume concrete composition. The difference between Example 10 and Example 8 lies in the preparation method of the slow-release quicklime. The preparation method of the slow-release quicklime in Example 10 is as follows:

[0047] S1. Mixing: Mix 2 parts by weight of polyvinyl alcohol, 0.8 parts by weight of glycerol and 30 parts by weight of quicklime to obtain a mixture.

[0048] S2. Ball milling: Add the mixture to a ball mill and mill it evenly to obtain slow-release quicklime.

[0049] Example 11

[0050] Example 11 provides a large-volume concrete composition. The difference between Example 11 and Example 8 lies in the preparation method of the slow-release quicklime. The preparation method of the slow-release quicklime in Example 11 is as follows:

[0051] S1. Mixing: Mix 0.5 parts by weight of polyvinyl alcohol, 0.3 parts by weight of glycerol and 15 parts by weight of quicklime to obtain a mixture.

[0052] S2. Ball milling: Add the mixture to a ball mill and mill it evenly to obtain slow-release quicklime.

[0053] Example 12

[0054] Example 12 provides a large-volume concrete composition. The difference between Example 12 and Example 8 is that, in the preparation of slow-release quicklime in Example 12, step S1 includes the following steps:

[0055] S11. Premix: Add 1 part by weight of polyvinyl alcohol and 0.5 parts by weight of glycerol to a mixing tank and stir evenly to obtain a premix; S12. Remix: Add 20 parts by weight of quicklime to the premix in the mixing tank and stir evenly to obtain a mixture.

[0056] Example 13

[0057] Example 13 provides a large-volume concrete composition. The difference between Example 13 and Example 12 is that the degree of polymerization of polyvinyl alcohol in Example 13 is 1700.

[0058] Example 14

[0059] Example 14 provides a large-volume concrete composition. The difference between Example 14 and Example 12 is that the degree of polymerization of polyvinyl alcohol in Example 14 is 2400.

[0060] Example 15

[0061] Example 15 provides a large-volume concrete composition. The difference between Example 15 and Example 13 is that saturated fatty acids are used instead of glycerol in the preparation of slow-release quicklime.

[0062] Comparative Example 1

[0063] Comparative Example 1 provides a large-volume concrete composition. The difference between Comparative Example 1 and Example 2 is that no borax decahydrate is added in Comparative Example 1.

[0064] Comparative Example 2

[0065] Comparative Example 2 provides a large-volume concrete composition. The difference between Comparative Example 2 and Example 2 is that no slow-release limestone is added in Comparative Example 2.

[0066] Comparative Example 3

[0067] Comparative Example 3 provides a large-volume concrete composition. The difference between Comparative Example 3 and Example 2 is that no decahydrate borax and slow-release limestone are added in Comparative Example 3.

[0068] Testing and Inspection

[0069] Samples were prepared according to the composition and proportion of the large-volume concrete compositions in Examples 1-15 and Comparative Examples 1-3. The preparation method is as follows: slow-release quicklime and additives were weighed according to the proportion and put into a concrete mixer for mixing. Then, cement, coarse aggregate and fine sand were weighed according to the proportion and added to the concrete mixer for further mixing. Finally, water-reducing agent and water were weighed according to the proportion, and after the water-reducing agent and water were mixed evenly, they were added to the concrete mixer for further mixing to obtain large-volume concrete.

[0070] The following tests were performed on the samples prepared according to the mass concrete compositions of Examples 1-15 and Comparative Examples 1-3: (1) The 56-day compressive strength (MPa) of each sample was tested according to GB / T 50081-2002.

[0071] (2) The 28-day shrinkage rate (‰) of each sample was tested according to GBT 50082-2009.

[0072] (3) The total crack area per unit area (mm²) of each sample was tested according to GB / T 50082-2009. 2 / m 2 ).

[0073] The test data are shown in Table 2.

[0074] Table 2: Compressive strength, shrinkage properties, and cracking of the specimens

[0075]

[0076] The following detailed description of this application is based on the experimental data provided in Table 1-2.

[0077] Examples 1-3 investigated the effects of coarse aggregate, fine sand, cement, water, and water-reducing agent in the mass concrete composition on the compressive strength, autogenous shrinkage rate, and total crack area per unit area of ​​the prepared samples. The 56-day compressive strength of the sample prepared in Example 2 was greater than that of the samples prepared in Examples 1 and 3. The 28-day autogenous shrinkage rate and total crack area per unit area of ​​the sample prepared in Example 2 were both smaller than those of the samples prepared in Examples 1 and 3. This indicates that the mass concrete prepared in Example 2 has higher compressive strength, lower autogenous shrinkage rate, and is less prone to cracking. Considering all factors, Example 2 is the preferred embodiment.

[0078] Using Example 2 as a control, Examples 4 and 5 investigated the effect of the ratio of slow-release quicklime to additives in the mass concrete composition on the compressive strength, autogenous shrinkage rate, and total crack area per unit area of ​​the prepared samples. The 56-day compressive strength of the sample prepared in Example 2 was greater than that of the samples prepared in Examples 4 and 5. The 28-day autogenous shrinkage rate and total crack area per unit area of ​​the sample prepared in Example 2 were both smaller than those of the samples prepared in Examples 4 and 5. This indicates that the mass concrete prepared in Example 2 has higher compressive strength, lower autogenous shrinkage rate, and is less prone to cracking. Considering all factors, Example 2 is the preferred embodiment.

[0079] Using Example 2 as a control, Examples 6-9 investigated the effects of the type of additives and the ratio of borax decahydrate and zinc sulfate heptahydrate in the mass concrete composition on the compressive strength, autogenous shrinkage, and total crack area per unit area of ​​the prepared samples. The 56-day compressive strength of the sample prepared in Example 2 was lower than that of the sample prepared in Example 6. The 28-day autogenous shrinkage and total crack area per unit area of ​​the sample prepared in Example 2 were both greater than those of the sample prepared in Example 6, indicating that zinc sulfate heptahydrate helps to improve the compressive strength of mass concrete. The 56-day compressive strength of the samples prepared using Examples 7-9 was greater than that of the samples prepared using Examples 2 and 6. The 28-day autogenous shrinkage rate and total crack area per unit area of ​​the samples prepared using Examples 7-9 were both smaller than those of the samples prepared using Examples 2 and 6. Furthermore, the 56-day compressive strength of the sample prepared using Example 8 was greater than that of the samples prepared using Examples 7 and 9, and the 28-day autogenous shrinkage rate and total crack area per unit area of ​​the sample prepared using Example 8 were both smaller than those of the samples prepared using Examples 7 and 9. In summary, the synergistic effect of using a compound of borax decahydrate and zinc sulfate heptahydrate in a specific ratio helps to improve the compressive strength of mass concrete and significantly reduces its autogenous shrinkage rate and total crack area per unit area. Considering all factors, Example 8 is the preferred embodiment.

[0080] Using Example 8 as a control, Examples 10 and 11 investigated the effect of the proportion of raw materials used to prepare slow-release quicklime in the mass concrete composition on the compressive strength, autogenous shrinkage rate, and total crack area per unit area of ​​the prepared samples. The 56-day compressive strength of the sample prepared in Example 8 was greater than that of the samples prepared in Examples 10 and 11. The 28-day autogenous shrinkage rate and total crack area per unit area of ​​the sample prepared in Example 8 were both smaller than those of the samples prepared in Examples 10 and 11. This indicates that the mass concrete prepared in Example 8 has higher compressive strength, lower autogenous shrinkage rate, and is less prone to cracking. Considering all factors, Example 2 is the preferred embodiment.

[0081] Compared with Example 8, Example 12 investigated the effect of the step of preparing slow-release quicklime in the mass concrete composition on the compressive strength, autogenous shrinkage rate, and total crack area per unit area of ​​the obtained samples. The 56-day compressive strength of the sample obtained in Example 12 was greater than that of the sample obtained in Example 8. The 28-day autogenous shrinkage rate and total crack area per unit area of ​​the sample obtained in Example 12 were both smaller than those of the sample obtained in Example 8. This indicates that the mass concrete prepared in Example 12 has higher compressive strength, lower autogenous shrinkage rate, and is less prone to cracking. Considering all factors, Example 12 is the preferred embodiment.

[0082] Using Example 12 as a control, Examples 13 and 14 investigated the effect of the step in preparing slow-release quicklime in the mass concrete composition on the compressive strength, autogenous shrinkage rate, and total crack area per unit area of ​​the obtained samples. The 56-day compressive strength of the sample prepared in Example 13 was greater than that of the samples prepared in Examples 12 and 14. The 28-day autogenous shrinkage rate and total crack area per unit area of ​​the sample prepared in Example 13 were both smaller than those of the samples prepared in Examples 12 and 14. This indicates that the mass concrete prepared in Example 13 has higher compressive strength, lower autogenous shrinkage rate, and is less prone to cracking. Considering all factors, Example 13 is the preferred embodiment.

[0083] Using Example 13 as a control, Example 15 investigated the effect of the dispersant used to prepare slow-release quicklime in the mass concrete composition on the compressive strength, autogenous shrinkage, and total crack area per unit area of ​​the prepared samples. The 56-day compressive strength of the sample prepared using Example 13 was greater than that of the sample prepared using Example 15. The 28-day autogenous shrinkage and total crack area per unit area of ​​the sample prepared using Example 13 were both smaller than those of the sample prepared using Example 15. This indicates that the mass concrete prepared using Example 13 has higher compressive strength, lower autogenous shrinkage, and is less prone to cracking, suggesting that using glycerol as a dispersant is more effective than using saturated fatty acids. Considering all factors, Example 13 is the preferred embodiment.

[0084] Using Example 2 as a control, Comparative Examples 1-3 investigated the effects of additives and slow-release limestone in the mass concrete composition on the compressive strength, autogenous shrinkage, and total crack area per unit area of ​​the prepared samples. The 56-day compressive strength of the sample prepared in Example 2 was significantly greater than that of the samples prepared in Comparative Examples 1-3. Conversely, the 28-day autogenous shrinkage and total crack area per unit area of ​​the sample prepared in Example 2 were significantly smaller than those of the samples prepared in Comparative Examples 1-3. This indicates that the additives and slow-release limestone have a synergistic effect, greatly improving the compressive strength of the mass concrete, reducing its autogenous shrinkage, and mitigating the degree of cracking.

[0085] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A mass concrete composition characterised in that: It is prepared from the following components by weight parts: Coarse aggregate 200-400 parts; Fine sand 50-80 parts; Cement 60-90 parts; Water 28-38 parts; Water reducing agent 2-6 parts; Slow-release quicklime 10-20 parts; Additive 5-15 parts; The preparation method of the slow-release quicklime is as follows: Mix, ball mill polyvinyl alcohol, dispersant and quicklime to obtain slow-release quicklime; The dispersant is selected from one or both of glycerol and saturated fatty acid; The weight ratio of the quicklime, polyvinyl alcohol and dispersant is (15-30):1:(0.4-0.6); The additive is composed of zinc sulfate heptahydrate and borax decahydrate in a weight ratio of (0.25-4):

1.

2. Mass concrete composition according to claim 1, characterized in that: The degree of polymerization of the polyvinyl alcohol is 500-2400.

3. The mass concrete composition of claim 1, wherein: The mixing includes: first, premixing polyvinyl alcohol and dispersant to obtain a premix, and then uniformly mixing the premix with quicklime.

4. The mass concrete composition of claim 1, wherein: The weight ratio of the slow-release quicklime to the additive is 1:(0.25-1.5).

5. The mass concrete composition of claim 1, wherein: The water reducing agent is selected from one or more of polycarboxylate type water reducing agent, naphthalene type water reducing agent, aminosulfonate type water reducing agent, aliphatic type water reducing agent and lignin ring acid salt.

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