Super slow-setting concrete and preparation method thereof

Abstract

The present application relates to the field of concrete, and more specifically, it relates to a super slow setting concrete and a preparation method thereof. A super slow setting concrete comprises the following raw materials in parts by weight: 90-105 parts of water, 180-200 parts of Portland cement, 150-200 parts of admixtures, 1000-1200 parts of coarse aggregate, 700-800 parts of fine aggregate, 0-8 parts of admixtures, 15-25 parts of wheat straw liquid treatment, 8-15 parts of wheat straw solid treatment, and 1-6 parts of calcium carbonate whiskers; the preparation method of the wheat straw liquid treatment and the wheat straw solid treatment comprises the following steps: step 01: crushing wheat straw; step 02: soaking wheat straw in sodium hydroxide solution; step 03: solid-liquid separation of the material in step 02, the solid part is the wheat straw solid treatment, and the liquid part is the wheat straw liquid treatment. The present application has the advantages of improving early strength and good slow setting effect.

Description

Technical Field

[0001] The present invention relates to the field of concrete, and more specifically, to a super slow-setting concrete and a preparation method thereof. Background Art

[0002] Super slow setting concrete is a special type of concrete with longer initial setting time and slow setting time than ordinary concrete. In some special scenarios, such as bridges and tunnels, where a large area of ​​concrete needs to be poured, ordinary concrete will have a lot of plastic shrinkage after pouring, affecting the quality of the project; or in underwater construction, due to the effect of water, the initial setting time of ordinary concrete is shortened and cannot meet the construction requirements.

[0003] Conventional super-slow setting concrete is produced by adding retarders such as lignin sulfonates to concrete to slow down the hydration reaction of cement particles. However, this also causes problems such as insufficient early strength. Low early strength will make super-slow setting concrete unable to withstand excessive loads in the early stage, affecting the construction quality. Therefore, there is still room for improvement. Summary of the invention

[0004] In order to improve the early strength, the present application provides a super slow-setting concrete and a preparation method thereof.

[0005] In the first aspect, the present application provides a super slow setting concrete, which adopts the following technical solution:

[0006] A super slow setting concrete comprises the following raw materials in parts by weight: 90-105 parts of water, 180-200 parts of Portland cement, 150-200 parts of admixture, 1000-1200 parts of coarse aggregate, 700-800 parts of fine aggregate, 0-8 parts of admixture, 15-25 parts of liquid treated wheat straw, 8-15 parts of solid treated wheat straw, and 1-6 parts of calcium carbonate whiskers;

[0007] The preparation method of the wheat straw liquid treated product and the wheat straw solid treated product comprises the following steps:

[0008] Step 01: Crush the straw;

[0009] Step 02: Soak the wheat straw in sodium hydroxide solution;

[0010] Step 03: Solid-liquid separation of the material in step 02, the solid part is the wheat straw solid processed product, and the liquid part is the wheat straw liquid processed product.

[0011] Preferably, the liquid wheat straw treatment material is 18-23 parts, the solid wheat straw treatment material is 8-12 parts, and the calcium carbonate whisker is 3-5 parts by weight.

[0012] By adopting the above technical scheme, wheat straw is soaked in sodium hydroxide solution to obtain wheat straw liquid treated material and wheat straw solid treated material. The sodium hydroxide solution destroys the cell wall structure of the wheat straw, breaks the ether bond connecting the lignin structure inside the wheat straw, removes part of the hemicellulose and lignin wrapped outside the cellulose, and makes the wheat straw liquid treated material rich in monosaccharides. The wheat straw solid treated material contains wheat straw with undestroyed structure, wheat straw with a small part of the structure destroyed, and wheat straw with a large part of the structure destroyed; the wheat straw with a small part of the structure destroyed and the wheat straw with a large part of the structure destroyed expose the internal pores.

[0013] With the cooperation of wheat straw liquid treatment, wheat straw solid treatment and calcium carbonate whiskers, part of wheat straw liquid treatment and calcium carbonate whiskers will enter the pores exposed by wheat straw solid treatment. When preparing concrete, the monosaccharides in wheat straw liquid treatment are converted into sugar acids containing more hydroxyl functional groups after dissolving in water. Under the alkaline conditions of concrete preparation, they react with calcium ions of cement hydration to slow down the hydration reaction; and the hydroxyl groups of sugar acids can also combine with water molecules through hydrogen bonds to form a water film on the cement surface, which plays a retarding role. Since part of the wheat straw liquid treatment enters the wheat straw solid treatment, the sugar acid in the system is only a part, not all, at the beginning, and the concrete has the performance of retarding and high early strength. Moreover, wheat straw solid treatment and calcium carbonate whiskers can play a good filling role in the matrix in concrete, strengthen the connection strength between concrete, and help improve the early strength. Part of the concrete will also enter the pores of the wheat straw solid treatment and contact with calcium carbonate whiskers and wheat straw liquid treatment, which is conducive to strengthening the connection between the parts and improving the strength.

[0014] As the hydration reaction occurs, the alkaline conditions will break the ether bonds of a portion of the wheat straw solid treatment material, increase the monosaccharides in the system, and cause the system to continue to have a retarding effect, thereby extending the coagulation time.

[0015] Most of the retarders on the market form a film on a large amount of cement surface at the beginning to block the hydration reaction. Although they have a good retarding effect, the early strength is also low. However, the present application controls the degree of film formation on the cement surface at the beginning, and adopts a method of continuous film formation on the cement surface, and cooperates with wheat straw solid treatment and calcium carbonate whisker to enhance the connection strength of the system, so that the super-slow setting concrete has higher early strength and longer setting time.

[0016] Preferably, in step 02, the concentration of the sodium hydroxide solution is 10-15%, and the mass ratio of wheat straw to the sodium hydroxide solution is 1:(5-10).

[0017] Preferably, in step 02, the soaking time of the wheat straw in the sodium hydroxide solution is 1-3 hours.

[0018] By adopting the above technical solution, the conditions for soaking wheat straw in sodium hydroxide solution are further limited, and the degree of destruction of the wheat straw structure is controlled, so that it has a better coordination effect with the concrete system, effectively improving the early strength of concrete and extending the setting time.

[0019] Preferably, in step 01, the wheat straw is crushed into powder and passed through a 0.05-0.1 mm sieve.

[0020] By adopting the above technical solution, the wheat straw is crushed into powder, which is conducive to the sodium hydroxide solution to fully infiltrate the wheat straw and destroy the wheat straw structure more quickly; at the same time, it also indirectly limits the size of the wheat straw solid treatment material, which can be more fully mixed and evenly dispersed in the concrete system later, playing a good filling and strength improvement role.

[0021] Preferably, the calcium carbonate whiskers include at least one of 1-5 μm calcium carbonate whiskers and 10-15 μm calcium carbonate whiskers.

[0022] Preferably, the calcium carbonate whiskers are 1-5 μm calcium carbonate whiskers and 10-15 μm calcium carbonate whiskers, and the mass ratio of the 1-5 μm calcium carbonate whiskers to the 10-15 μm calcium carbonate whiskers is 1:(0.8-1.2), with the mass of the 1-5 μm calcium carbonate whiskers as the benchmark.

[0023] By adopting the above technical solution, the size of calcium carbonate whiskers is further limited, which can not only better fill the concrete system, but also better embed into the pores of the wheat straw solid treatment. The cement matrix that enters the pores of the wheat straw solid treatment is more firmly combined with the calcium carbonate crystals and is difficult to be pulled out, which effectively improves the effect of the super slow setting concrete.

[0024] Preferably, the admixture is a mixture of one or more of mineral powder, fly ash and steel slag.

[0025] Preferably, the fine aggregate is one of machine-made sand and river sand, or a mixture of the two.

[0026] Preferably, the coarse aggregate is crushed stone, crushed gravel or a mixture of the two.

[0027] In a second aspect, the present application provides a method for preparing super slow-setting concrete, which adopts the following technical solution:

[0028] A method for preparing slow-setting concrete comprises the following steps:

[0029] Step 1: Mix the wheat straw liquid treatment product, the wheat straw solid treatment product and the calcium carbonate whisker at 800-1000 r / min for 10-20 min to obtain a premix for standby use;

[0030] Step 2: Mix the silicate cement, admixture, water, fine aggregate, coarse aggregate, premix and admixture until uniform to obtain super slow setting concrete.

[0031] By adopting the above technical scheme, the liquid treated wheat straw, the solid treated wheat straw and the calcium carbonate whiskers are first mixed under specific mixing conditions to form a special structure in which part of the liquid treated wheat straw and the calcium carbonate whiskers enter the pores of the solid treated wheat straw, and then mixed with other raw materials, so that the super-slow setting concrete has higher early strength and longer slow setting time.

[0032] In summary, this application has the following beneficial effects:

[0033] 1. With the cooperation of wheat straw liquid treatment material, wheat straw solid treatment material and calcium carbonate whiskers, the monosaccharides in the wheat straw liquid treatment material can effectively slow down the hydration reaction, and under alkaline conditions, the wheat straw solid treatment material is destroyed, and a part of monosaccharides will be produced, which will continuously delay the hydration reaction, thereby playing a good retarding effect.

[0034] 2. With the cooperation of liquid wheat straw treatment material, solid wheat straw treatment material and calcium carbonate whiskers, solid wheat straw treatment material and calcium carbonate whiskers are effectively filled into the system to strengthen the connection strength between concrete, which is beneficial to improve the early strength and later strength. DETAILED DESCRIPTION

[0035] The present application is further described in detail below with reference to the embodiments.

[0036] The raw materials used in the following examples and comparative examples are all commercially available products.

[0037] Preparation Example

[0038] Preparation Example 1

[0039] A method for preparing a liquid processed wheat straw product and a solid processed wheat straw product comprises the following steps:

[0040] Step 01: Grind the wheat straw into powder and pass it through a 0.1mm sieve.

[0041] Step 02: Soak the wheat straw in a 12% sodium hydroxide solution with a mass ratio of wheat straw to sodium hydroxide solution of 1:8 for 2 hours.

[0042] Step 03: Solid-liquid separation of the material in step 02, the solid part is the wheat straw solid processed product, and the liquid part is the wheat straw liquid processed product.

[0043] Preparation Example 2

[0044] A method for preparing a liquid processed wheat straw product and a solid processed wheat straw product comprises the following steps:

[0045] Step 01: Grind the wheat straw into powder and pass it through a 0.05mm sieve.

[0046] Step 02: Soak the wheat straw in a 10% sodium hydroxide solution with a mass ratio of wheat straw to sodium hydroxide solution of 1:10 for 3 hours.

[0047] Step 03: Solid-liquid separation of the material in step 02, the solid part is the wheat straw solid processed product, and the liquid part is the wheat straw liquid processed product.

[0048] Preparation Example 3

[0049] A method for preparing a liquid processed wheat straw product and a solid processed wheat straw product comprises the following steps:

[0050] Step 01: Grind the wheat straw into powder and pass it through a 0.1mm sieve.

[0051] Step 02: Soak the wheat straw in a 15% sodium hydroxide solution with a mass ratio of wheat straw to sodium hydroxide solution of 1:5 for 1 hour.

[0052] Step 03: Solid-liquid separation of the material in step 02, the solid part is the wheat straw solid processed product, and the liquid part is the wheat straw liquid processed product.

[0053] Preparation Example 4

[0054] A method for preparing a liquid processed wheat straw product and a solid processed wheat straw product comprises the following steps:

[0055] Step 01: Grind the wheat straw into powder and pass it through a 0.1mm sieve.

[0056] Step 02: Soak the wheat straw in a 5% sodium hydroxide solution with a mass ratio of wheat straw to sodium hydroxide solution of 1:8 for 2 hours.

[0057] Step 03: Solid-liquid separation of the material in step 02, the solid part is the wheat straw solid processed product, and the liquid part is the wheat straw liquid processed product.

[0058] Preparation Example 5

[0059] A method for preparing a liquid processed wheat straw product and a solid processed wheat straw product comprises the following steps:

[0060] Step 01: Grind the wheat straw into powder and pass it through a 0.1mm sieve.

[0061] Step 02: Soak the wheat straw in a 25% sodium hydroxide solution with a mass ratio of wheat straw to sodium hydroxide solution of 1:8 for 2 hours.

[0062] Step 03: Solid-liquid separation of the material in step 02, the solid part is the wheat straw solid processed product, and the liquid part is the wheat straw liquid processed product.

[0063] Preparation Example 6

[0064] A method for preparing a liquid processed wheat straw product and a solid processed wheat straw product comprises the following steps:

[0065] Step 01: Grind the wheat straw into powder and pass it through a 0.1mm sieve.

[0066] Step 02: Soak the wheat straw in a 12% sodium hydroxide solution with a mass ratio of wheat straw to sodium hydroxide solution of 1:1 for 2 hours.

[0067] Step 03: Solid-liquid separation of the material in step 02, the solid part is the wheat straw solid processed product, and the liquid part is the wheat straw liquid processed product.

[0068] Preparation Example 7

[0069] A method for preparing a liquid processed wheat straw product and a solid processed wheat straw product comprises the following steps:

[0070] Step 01: Grind the wheat straw into powder and pass it through a 0.1mm sieve.

[0071] Step 02: Soak the wheat straw in a 12% sodium hydroxide solution with a mass ratio of wheat straw to sodium hydroxide solution of 1:20 for 2 hours.

[0072] Step 03: Solid-liquid separation of the material in step 02, the solid part is the wheat straw solid processed product, and the liquid part is the wheat straw liquid processed product.

[0073] Preparation Example 8

[0074] A method for preparing a liquid treated product and a solid treated product comprises the following steps:

[0075] Step 01: Crush peanut shells into powder and pass through a 0.1mm sieve.

[0076] Step 02: Soak peanut shells in 12% sodium hydroxide solution with a mass ratio of peanut shells to sodium hydroxide solution of 1:20 for 2 hours.

[0077] Step 03: Solid-liquid separation of the material in step 02, the solid part is the solid processed product, and the liquid part is the liquid processed product.

[0078] Example

[0079] Example 1

[0080] A super slow-setting concrete, comprising the following raw materials:

[0081] Water, Portland cement, admixture, coarse aggregate, fine aggregate, admixture, liquid treated wheat straw, solid treated wheat straw, calcium carbonate whisker.

[0082] The specific dosage is shown in Table 1.

[0083] Portland cement is commercially available with a specification of P042.5.

[0084] The admixtures are mineral powder and fly ash, and the mass ratio of mineral powder to fly ash is 1:2.1, that is, the mineral powder is kg and the fly ash is kg.

[0085] The coarse aggregate is 5-20mm crushed stone.

[0086] Fine aggregate is machine-made sand, specifically medium sand.

[0087] The admixture is a polycarboxylic acid-based water reducer, which is commercially available.

[0088] The liquid processed wheat straw and the solid processed wheat straw were the liquid processed wheat straw and the solid processed wheat straw prepared in Preparation Example 1.

[0089] The calcium carbonate whiskers are 1-5 μm calcium carbonate whiskers and 10-15 μm calcium carbonate whiskers, and the mass ratio of the 1-5 μm calcium carbonate whiskers and the 10-15 μm calcium carbonate whiskers is 1:1. That is, the 1-5 μm calcium carbonate whiskers are 1 kg, and the 10-15 μm calcium carbonate whiskers are 1 kg.

[0090] The present application also provides a method for preparing super slow-setting concrete, comprising the following steps:

[0091] Step 1: Put the liquid treated wheat straw, the solid treated wheat straw and the calcium carbonate whisker into a reactor and mix them at 900 r / min for 15 minutes to obtain a premix for later use.

[0092] Step 2: Mix the silicate cement, admixture, water, fine aggregate, coarse aggregate, premix and admixture, and stir until uniform to obtain super slow setting concrete.

[0093] Example 2

[0094] A super slow setting concrete, which is different from Example 1 in that the amounts of liquid treated wheat straw, solid treated wheat straw and calcium carbonate whiskers are different, as shown in Table 1 for details.

[0095] Example 3

[0096] A super slow setting concrete, which is different from Example 1 in that the amounts of liquid treated wheat straw, solid treated wheat straw and calcium carbonate whiskers are different, as shown in Table 1 for details.

[0097] Example 4

[0098] A super slow setting concrete, which is different from Example 1 in that the amount of each raw material is different, as shown in Table 1 for details.

[0099] The calcium carbonate whiskers are 1-5 μm calcium carbonate whiskers and 10-15 μm calcium carbonate whiskers, and the mass ratio of the 1-5 μm calcium carbonate whiskers to the 10-15 μm calcium carbonate whiskers is 1:0.8. That is, the 1-5 μm calcium carbonate whiskers are 0.56 kg, and the 10-15 μm calcium carbonate whiskers are 0.44 kg.

[0100] The liquid treated wheat straw and the solid treated wheat straw were the liquid treated wheat straw and the solid treated wheat straw obtained in Preparation Example 2.

[0101] Example 5

[0102] A super slow setting concrete, which is different from Example 1 in that the amount of each raw material is different, as shown in Table 1 for details.

[0103] The calcium carbonate whiskers are 1-5 μm calcium carbonate whiskers and 10-15 μm calcium carbonate whiskers, and the mass ratio of the 1-5 μm calcium carbonate whiskers to the 10-15 μm calcium carbonate whiskers is 1:1.2. That is, the 1-5 μm calcium carbonate whiskers are 2.27 kg, and the 10-15 μm calcium carbonate whiskers are 2.73 kg.

[0104] The liquid treated wheat straw and the solid treated wheat straw were the liquid treated wheat straw and the solid treated wheat straw prepared in Preparation Example 3.

[0105] Table 1

[0106]

[0107] Example 6

[0108] A super slow-setting concrete, which is different from Example 1 in that the liquid treated wheat straw and the solid treated wheat straw are the liquid treated wheat straw and the solid treated wheat straw prepared in Preparation Example 4.

[0109] Example 7

[0110] A super slow-setting concrete, which is different from Example 1 in that the liquid treated wheat straw and the solid treated wheat straw are the liquid treated wheat straw and the solid treated wheat straw prepared in Preparation Example 5.

[0111] Example 8

[0112] A super slow-setting concrete, which is different from Example 1 in that the liquid treated wheat straw and the solid treated wheat straw are the liquid treated wheat straw and the solid treated wheat straw prepared in Preparation Example 6.

[0113] Example 9

[0114] A super slow-setting concrete, which is different from Example 1 in that the liquid treated wheat straw and the solid treated wheat straw are the liquid treated wheat straw and the solid treated wheat straw prepared in Preparation Example 7.

[0115] Comparative Example

[0116] Comparative Example 1

[0117] A super slow setting concrete, which is different from Example 1 in that no liquid treatment with wheat straw is used.

[0118] Comparative Example 2

[0119] A super slow setting concrete, which is different from Example 1 in that wheat straw solid treatment is not used.

[0120] Comparative Example 3

[0121] A super slow setting concrete, which is different from Example 1 in that the calcium carbonate whiskers are replaced by calcium sulfate whiskers.

[0122] Comparative Example 4

[0123] A super slow-setting concrete, which is different from Example 1 in that the liquid treated material of wheat straw is replaced by the liquid treated material of Preparation Example 8, and the solid treated material of wheat straw is replaced by the solid treated material of Preparation Example 8.

[0124] Comparative Example 5

[0125] A super slow setting concrete, which is different from Example 1 in that the liquid processed wheat straw is 1.5 kg, the solid processed wheat straw is 10 kg, and the calcium carbonate whisker is 0.5 kg; the mass ratio of the calcium carbonate whisker of 1-5 μm to the calcium carbonate whisker of 10-15 μm is 1:1.

[0126] Comparative Example 6

[0127] A super slow setting concrete, which is different from Example 1 in that the wheat straw liquid treatment material, the wheat straw solid treatment material, and the calcium carbonate whisker are replaced by sodium wood sulfonate, that is, the wheat straw liquid treatment material is 0 kg, the wheat straw solid treatment material is 0 kg, the calcium carbonate whisker is 0 kg, and the sodium wood sulfonate is 12 kg.

[0128] Performance testing

[0129] 1. Compressive strength: Referring to GB / T 50081-2019 "Standard for Test Methods for Physical and Mechanical Properties of Concrete", the compressive strength of the concrete of Examples 1-9 and Comparative Examples 1-6 was tested, and the compressive strengths at 3d, 7d, and 28d were recorded in Table 1.

[0130] 2. Setting time: The setting time of the concrete of Examples 1-9 and Comparative Examples 1-6 was tested with reference to GB / T 50080-2016 "Standard for Test Methods for Performance of Ordinary Concrete Mixtures", and the initial setting time and final setting time were recorded in Table 2.

[0131] Table 2

[0132]

[0133]

[0134] Comparative Example 6 is based on Example 1, but the liquid treated wheat straw, the solid treated wheat straw, and the calcium carbonate whisker are replaced with sodium lignosulfonate. According to the comparison of the test data of Examples 1-9 and Comparative Example 6 in Table 2, it can be seen that the retarding effect of Comparative Example 6 is similar to that of Example 1, and Example 1 is slightly better; and the more obvious improvement of Example 1 over Comparative Example 6 is the compressive strength. The concrete of Example 1 has a higher compressive strength than that of Comparative Example 6 in the early stage, which significantly improves the performance of the concrete. It shows that the concrete provided by the present application can have a relatively good strength in the early stage without affecting the retarding effect.

[0135] According to the comparison of the test results of Example 1 and Comparative Examples 1-5 in Table 2, it can be seen that the compressive strength and coagulation effect of Comparative Examples 1-5 are lower than those of Example 1 to varying degrees, and obviously cannot achieve the performance of Example 1 with high early strength, high late strength, and good slow setting effect. This shows that the combination of wheat straw liquid treatment material, wheat straw solid treatment material, and calcium carbonate whisker in specific dosage is a complete and organic technical solution, and the selection or dosage combination of wheat straw liquid treatment material, wheat straw solid treatment material, and calcium carbonate whisker cannot be arbitrarily destroyed, otherwise the special effect cannot be exerted.

[0136] In Example 6-9, the soaking conditions of the sodium hydroxide solution and the wheat straw are changed on the basis of Example 1. According to the comparison of the test data of Example 1 and Example 6-9 in Table 2, the compressive strength of the concrete of Example 6-9 is reduced and the setting time is also shortened. This indicates that further limiting the combination of the sodium hydroxide solution and the wheat straw at a specific concentration and a specific mass ratio can have a more appropriate degree of damage to the wheat straw structure so as to cooperate with the subsequent function in the concrete.

[0137] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make modifications to the present embodiment without any creative contribution as needed, but such modifications are protected by the patent law as long as they are within the scope of the claims of the present application.

Claims

1. A super slow setting concrete, characterized in that: The raw materials include the following in parts by weight: 90-105 parts of water, 180-200 parts of Portland cement, 150-200 parts of admixture, 1000-1200 parts of coarse aggregate, 700-800 parts of fine aggregate, 0-8 parts of admixture, 6-8 parts of liquid treated wheat straw, 2.5-4.0 parts of solid treated wheat straw, and 1.5-2.5 parts of calcium carbonate whisker; The calcium carbonate whiskers are 1-5 μm calcium carbonate whiskers and 10-15 μm calcium carbonate whiskers, and the mass ratio of the 1-5 μm calcium carbonate whiskers to the 10-15 μm calcium carbonate whiskers is 1:(0.8-1.2), with the mass of the 1-5 μm calcium carbonate whiskers as the basis; The admixture is a mixture of one or more of mineral powder, fly ash and steel slag; The preparation method of the wheat straw liquid treated product and the wheat straw solid treated product comprises the following steps: Step 01: Crush the wheat straw into powder and pass it through a 0.05-0.1mm sieve; Step 02: Soak the wheat straw in a sodium hydroxide solution, wherein the concentration of the sodium hydroxide solution is 10-15%, the mass ratio of the wheat straw to the sodium hydroxide solution is 1:(5-10), and the soaking time of the wheat straw in the sodium hydroxide solution is 1-3 hours; Step 03: Solid-liquid separation of the material in step 02, the solid part is the wheat straw solid processed product, and the liquid part is the wheat straw liquid processed product.

2. A method for preparing the super slow setting concrete according to claim 1, characterized in that: The following steps are involved: Step 1: Mix the wheat straw liquid treatment product, the wheat straw solid treatment product and the calcium carbonate whisker at 800-1000 r / min for 10-20 min to obtain a premix for standby use; Step 2: Mix the silicate cement, admixture, water, fine aggregate, coarse aggregate, premix and admixture until uniform to obtain super slow setting concrete.

Images