CN116120008A - Steam curing-free precast concrete and preparation method thereof - Google Patents

Abstract

The application relates to the technical field of concrete, and in particular discloses steam-curing-free precast concrete and a preparation method thereof, wherein the steam-curing-free precast concrete comprises the following raw materials in parts by weight: 240-320 parts of Portland cement, 950-1050 parts of coarse aggregate, 800-850 parts of fine aggregate, 60-80 parts of admixture, 8-15 parts of compound early strength admixture, 6-8 parts of water reducer and 160-180 parts of water; the compound early-strength admixture comprises calcium aluminum sulfate cement, calcium formate, triethanolamine, calcium aluminate and a retarder; the steaming-free precast concrete prepared by the method has higher early compressive strength.

Description

Steam curing-free precast concrete and preparation method thereof

Technical Field

The application relates to the technical field of concrete, in particular to steam curing-free precast concrete and a preparation method and application thereof.

Background

The concrete uses cement, sand and stone as basic raw materials, and is used as a traditional building material, so that the performance is stable, and the built building body is safe and reliable in the service period. With rapid development of fabricated structures, precast concrete units are increasingly used in various engineering fields. The high early strength can accelerate the turnover rate of the die, improve the production efficiency of enterprises, further accelerate the construction progress, shorten the construction period and improve the economic benefit.

At present, a common countermeasure for prefabricated parts manufacturers is to use a steam curing method to improve the early strength of the concrete prefabricated parts. The steam curing is to put the concrete into normal pressure steam with higher temperature for damp-heat curing, thereby accelerating the hydration speed of the cement and improving the early strength of the concrete. However, in the steam curing process of concrete, the heated expansion of gas and the heated evaporation of free water can increase the total porosity of the concrete, and communication holes are easy to form, so that the strength of the concrete is affected. Therefore, the early strength of the current precast concrete is not high enough, the turnover efficiency of the mould is generally low, and the production efficiency is greatly slowed down.

Disclosure of Invention

In order to improve the early strength of the steam curing-free precast concrete, the application provides the steam curing-free precast concrete and a preparation method thereof.

In a first aspect, the present application provides a precast concrete free of steam curing, which adopts the following technical scheme:

the steam curing-free precast concrete comprises the following raw materials in parts by weight: 240-320 parts of Portland cement, 950-1050 parts of coarse aggregate, 800-850 parts of fine aggregate, 60-80 parts of admixture, 8-15 parts of compound early strength admixture, 6-8 parts of water reducer and 160-180 parts of water; the compound early-strength admixture comprises aluminum calcium sulfate cement, calcium formate, triethanolamine, calcium aluminate and a retarder.

By adopting the technical scheme, the steam curing-free precast concrete prepared by the method is prepared from silicate cement, coarse aggregate, fine aggregate, admixture, compound early strength admixture, water reducing agent and water, wherein silicate cement is adopted as raw materials, calcium silicate is used as a main component to form nano calcium silicate hydrate, and the nano calcium silicate hydrate is used as crystal nucleus, so that when the nano calcium silicate hydrate is added into cement concrete, the cement hydration speed can be quickly improved, calcium silicate hydrate is formed, the induction period of cement hydration can be effectively shortened, and the early strength of the concrete is further improved; in addition, the compound early-strength admixture is added, the compound early-strength admixture is prepared by adopting a compound mode of an organic material and an inorganic material, calcium sulfoaluminate cement is used as a main component, and the prepared compound early-strength admixture is added into raw materials to effectively improve the early strength of concrete by adding other quick-setting powder materials and uniformly mixing.

Preferably, the steam curing-free precast concrete comprises the following raw materials in parts by weight: the steam curing-free precast concrete comprises the following raw materials in parts by weight: 260-300 parts of Portland cement, 980-1000 parts of coarse aggregate, 820-840 parts of fine aggregate, 65-75 parts of admixture, 10-12 parts of compound early strength admixture, 6.5-7.5 parts of water reducer and 165-170 parts of water.

By adopting the technical scheme, the compression strength of the prepared steam-curing-free precast concrete in each period is improved and the slump of the concrete is reduced by optimizing the proportion of the steam-curing-free precast concrete raw materials.

Preferably, the compound early strength admixture comprises the following raw materials in parts by weight: 60-100 parts of calcium aluminum sulfate cement, 4-5.5 parts of calcium formate, 3-4 parts of triethanolamine, 12-15 parts of calcium aluminate and 1.5-3.5 parts of retarder.

By adopting the technical scheme, the compound early-strength admixture in the application is prepared by compounding aluminum calcium sulfate cement, calcium formate, triethanolamine, calcium aluminate and retarder, so that the early-strength effect of the obtained compound early-strength admixture is remarkable, on one hand, the hydration reaction of the cementing material in the concrete is enhanced along with the increase of a certain amount of the doping amount, the effect of activating the early-strength property is enhanced, the hydration reaction is accelerated, the cementing property of the hydrate is enhanced, and the fluidity of the mixture is reduced; on the other hand, the retarding effect of BoA in the compound functional component plays a positive threshold role in controlling the hydration reaction of the mixture, namely, the compound functional component can be converted from an effective hydration inhibition state to a hydration induction state after an operable working time zone, and has obvious effect on the mechanical properties of concrete.

Preferably, the admixture consists of fly ash and mineral powder.

By adopting the technical scheme, the admixture in the application consists of the fly ash and the mineral powder, wherein the main mineral components of the fly ash are silicon dioxide and Fe ₂ O ₃ 、FeO、TiO ₂ CaO, etc., can make calcium hydroxide which is unfavorable for concrete form good C-S-H gel, and can improve interface combination of slurry and aggregateDegree. The fly ash particles are mainly microbeads, the particle size is smaller than that of cement particles, the effects of filling, lubrication, deflocculation, water drop dispersion and the like in concrete are more outstanding, the water consumption of the concrete is reduced, the workability is improved, the concrete is uniform and compact, and the strength and the durability of the concrete are improved.

Preferably, the mass ratio of the fly ash to the mineral powder is 1: (0.5-2)

By adopting the technical scheme, the mineral powder and the fly ash are mixed, so that the concrete slump loss is well inhibited, the hydration heat of the concrete is reduced, the occurrence of concrete cracks can be effectively reduced, according to test results, when the fly ash and the mineral powder are mixed again, the early strength of the precast concrete is improved, and especially, the mixing amount of the fly ash and the mineral powder is 1:2, the faster the early strength of the concrete is developed.

Preferably, the raw material also comprises 5-15 parts by weight of nano silicon dioxide.

By adopting the technical scheme, the nano silicon dioxide is added in the concrete, is far smaller than cement and silica fume particles, has large specific surface area, and increases the density of the ultra-high-performance concrete on a microscopic scale due to the filling effect. The volcanic ash activity is much higher than that of silica fume and fly ash. The nano silicon dioxide reacts with calcium hydroxide which is unfavorable for strength to be converted into C-S-H gel, and is filled between cement hydration products, so that the early strength of the concrete is greatly promoted to be increased.

Preferably, the water reducer is a polycarboxylic acid high-performance water reducer or an early-strength polycarboxylic acid high-performance water reducer.

Through adopting above-mentioned technical scheme, the intensity is faster at 1d to 5 d's growth after the concrete stirring in this application, can not appear intensity shrinkage phenomenon in the later stage. Therefore, the early strength polycarboxylate superplasticizer exhibits more excellent performance in terms of early strength of concrete.

In a second aspect, the present application provides a method for preparing a non-autoclaved precast concrete, which adopts the following technical scheme:

the preparation method of the steam curing-free precast concrete comprises the following steps:

1) Mixing the coarse aggregate and the fine aggregate, and stirring for 1-3min to obtain a first mixture;

2) Adding Portland cement, an admixture, a compound early strength admixture, a water reducing agent and 3/4 of water into the first mixture, and stirring for 5-15min to obtain a second mixture;

3) And adding the rest 1/4 of water into the second mixture, mixing and stirring for 1-2min to obtain the steam curing-free precast concrete.

By adopting the technical scheme, the steaming-free precast concrete prepared by the method is different from the traditional stirring method in the stirring process, the coarse aggregate and the fine aggregate are poured into a concrete mixer together to be uniformly stirred, and then the cementing material is poured into the mixer to be stirred together with the aggregate, so that the stirring mode is beneficial to improving the workability of the concrete, and the preparation method of the steaming-free precast concrete is simple and feasible, and can effectively improve the production efficiency.

In summary, the present application has the following beneficial effects:

1. the steam curing-free precast concrete is prepared from Portland cement, coarse aggregate, fine aggregate, admixture, compound early strength admixture, water reducer and water, wherein the Portland cement is adopted as raw materials, calcium silicate is used as a main component to form nano calcium silicate hydrate, the nano calcium silicate hydrate is used as crystal nucleus, when the nano calcium silicate hydrate is added into cement concrete, the cement hydration speed can be quickly improved, the calcium silicate hydrate is formed, the induction period of cement hydration can be effectively shortened, and the early strength of the concrete is further improved; in addition, the compound early-strength admixture is added, the compound early-strength admixture is prepared by adopting a compound mode of an organic material and an inorganic material, calcium sulfoaluminate cement is used as a main component, and the prepared compound early-strength admixture is added into raw materials to effectively improve the early strength of concrete by adding other quick-setting powder materials and uniformly mixing.

2. The compound early-strength admixture is prepared by compounding calcium aluminum sulfate cement, calcium formate, triethanolamine, calcium aluminate and a retarder, so that the early-strength effect of the obtained compound early-strength admixture is remarkable, on one hand, the hydration reaction of a cementing material in concrete is enhanced along with a certain increase of the doping amount, the effect of activating the early-strength property is enhanced, the hydration reaction is accelerated, the cementing property of a hydrate is enhanced, and the fluidity of the mixture is reduced; on the other hand, the retarding effect of BoA in the compound functional component plays a positive threshold role in controlling the hydration reaction of the mixture, namely, the compound functional component can be converted from an effective hydration inhibition state to a hydration induction state after an operable working time zone, and has obvious effect on the mechanical properties of concrete.

3. The non-autoclaved precast concrete prepared in the application has higher compressive strength, and after the compressive strength test of the concrete, the compressive strengths of 16h, 1d, 5d and 28d can reach 12.2MPa, 17.0MPa, 36.9MPa and 40.7MPa respectively, and the slump is smaller, 80-110mm, so that the production requirement of precast components is met.

Detailed Description

The present application is described in further detail below with reference to examples.

Raw materials

The Portland cement in the raw materials used in the application adopts P.O52.5 common Portland cement; the fineness of the fly ash is 15.5 by adopting class II fly ash; the mineral powder is S95 mineral powder; the solid content of the polycarboxylate water reducer is 9%, and the pH value is 6.1; the early-strength polycarboxylate water reducer contains 18% of solid content and has a pH value of 6.5, and the rest raw materials are common commercial materials.

Preparation example

Preparation examples 1 to 3

The preparation method of the compound early strength admixture of preparation examples 1-3 comprises the following steps of: the raw materials are weighed according to the dosage in the table 1, and then the raw materials are stirred uniformly, thus obtaining the compound early strength admixture. Wherein, retarder is BoA.

TABLE 1 raw materials for preparation examples 1-3 Compound early strength admixture and amounts (kg) of the respective raw materials

	Preparation example 1	Preparation example 2	Preparation example 3
				Calcium aluminum sulfate cement	60	80	100
Calcium formate	5.5	5	4
				Triethanolamine salt	3	3.5	4
Calcium aluminate	15	13	12
				Retarder agent	1.5	2.5	3.5

Examples

Examples 1 to 4

The raw materials and the amounts of the raw materials of the non-autoclaved precast concrete in examples 1-4 are shown in Table 2, and the preparation method is as follows: 1) Mixing the coarse aggregate and the fine aggregate, and stirring for 1min to obtain a first mixture;

2) Adding Portland cement, an admixture, a compound early strength admixture, a water reducing agent and 3/4 of water into the first mixture, and stirring for 5min to obtain a second mixture;

3) And adding the rest 1/4 of water into the second mixture, mixing and stirring for 1min to obtain the steam curing-free precast concrete.

Wherein the compound early strength admixture is prepared from preparation example 1, and the mass ratio of fly ash to mineral powder in the admixture is 1:0.5, the water reducer is a polycarboxylic acid high-performance water reducer.

TABLE 2 raw materials for examples 1 to 4 and amounts (kg) of the respective raw materials

	Example 1	Example 2	Example 3	Example 4
					Portland cement	240	260	300	320
Coarse aggregate	1050	1000	980	950
					Fine aggregate	800	820	840	850
Admixture material	80	75	65	60
					Compound early strength admixture	8	8	8	8
Water reducing agent	6	6.5	7.5	8
					Water and its preparation method	180	170	165	160

Example 5

The steam curing-free precast concrete is different from example 3 in that the compound early strength admixture is from preparation example 2, and the rest steps are the same as example 3.

Example 6

The steam curing-free precast concrete is different from example 3 in that the compound early strength admixture is from preparation example 3, and the rest steps are the same as example 3.

Example 7

The steam curing-free precast concrete is different from the embodiment 5 in that the addition amount of the compound early strength admixture is 10kg, and the rest steps are the same as the embodiment 5.

Example 8

The steam curing-free precast concrete is different from the precast concrete in the embodiment 5 in that the addition amount of the compound early strength admixture is 12kg, and the rest steps are the same as the embodiment 5.

Example 9

The steam curing-free precast concrete is different from the precast concrete in the embodiment 5 in that the addition amount of the compound early strength admixture is 15kg, and the rest steps are the same as the embodiment 5.

Example 10

The steam curing-free precast concrete is different from the embodiment 9 in that the mass ratio of fly ash to mineral powder in the admixture is 1:1, the rest of the procedure is the same as in example 9.

Example 11

The steam curing-free precast concrete is different from the embodiment 9 in that the mass ratio of fly ash to mineral powder in the admixture is 1:2, the rest of the procedure is the same as in example 9.

Example 12

The steam curing-free precast concrete is different from example 11 in that 5kg of nano silica is added into the raw materials, and the rest steps are the same as example 11.

Example 13

The steam curing-free precast concrete is different from example 11 in that 10kg of nano silica is added into the raw materials, and the rest steps are the same as example 11.

Example 14

The steam curing-free precast concrete is different from example 11 in that 15kg of nano silica is added into the raw materials, and the rest steps are the same as example 11.

Example 15

The steam curing-free precast concrete is different from the embodiment 14 in that the water reducer is an early-strength polycarboxylic acid high-performance water reducer, and the rest steps are the same as the embodiment 14.

Comparative example

Comparative example 1

The steam curing-free precast concrete is different from the embodiment 10 in that the addition amount of the compound early strength admixture is 0, and the rest steps are the same as the embodiment 10.

Comparative example 2

The steam curing-free precast concrete is different from example 7 in that the addition amount of fly ash in the admixture is 0, and the rest steps are the same as example 7.

Comparative example 3

The steam curing-free precast concrete is different from example 7 in that the addition amount of mineral powder in the admixture is 0, and the rest steps are the same as example 7.

Performance test

Detection method/test method

The following performance tests were conducted on the non-autoclaved precast concrete prepared in examples 1 to 15 and comparative examples 1 to 3, and the test results are shown in Table 3.

The non-autoclaved precast concrete samples prepared in examples 1 to 15 and comparative examples 1 to 3 were each carried out under standard curing conditions (temperature 20.+ -. 2 ℃ C., humidity not less than 95%) in preparation for performance test.

Compressive strength test: compressive strength testing was performed according to the test method described in GB/T50081-2019 test method for mechanical Properties of ordinary concrete.

Slump test: the test adopts a slump barrel with the upper opening diameter of 100mm, the lower opening diameter of 200mm and the height of 300mm, the stirred concrete slurry is filled in three times, the filling amount is 1/3 of the slump barrel, after each filling, iron bars are used for tamping 20 up and down, and after the slump barrel is filled, a spatula is used for trowelling the upper opening of the slump barrel. And then slowly lifting the slump barrel, wherein the concrete slurry can slump, measuring the height of the concrete slurry by using a ruler when the concrete slurry stops falling, and subtracting the slump height from the slump barrel height to obtain the difference value, namely the slump of the precast concrete.

TABLE 3 detection results for examples 1-15 and comparative examples 1-3

As can be seen by combining the detection data of examples 1-4, the proportion of the raw materials in example 3 is better, and the steaming-free precast concrete prepared by adopting the proportion of example 3 has higher compressive strength of 16h, 1d, 5d and 28d and smaller slump after the compressive strength test of the concrete, which indicates that the early strength of the steaming-free precast concrete prepared by adopting the proportion is higher.

As can be seen by combining the test data of example 3 and examples 5-6, the compound early strength admixture of preparation example 2 has a better proportion, the compound early strength admixture prepared by preparation example 2 is added into the preparation process of the steam curing-free precast concrete, and the finally prepared steam curing-free precast concrete has higher compressive strength of 16h, 1d, 5d and 28d and smaller slump after the compressive strength test of the concrete, which indicates that the steam curing-free precast concrete prepared by adopting the compound early strength admixture has higher early strength.

The test data of the embodiment 5 and the embodiment 7-9 show that the strength of the non-autoclaved precast concrete in each period is gradually increased along with the increase of the addition amount of the compound early-strength admixture, which proves that the compound early-strength admixture can effectively improve the compressive strength of the non-autoclaved precast concrete. When the addition amount of the compound early-strength admixture is 15kg, the proportion of the raw materials of the non-autoclaved precast concrete is better, and the prepared non-autoclaved precast concrete has higher compressive strength of 16h, 1d, 5d and 28d and smaller slump after the compressive strength test of the concrete, so that the early strength of the non-autoclaved precast concrete prepared by adopting the compound early-strength admixture in the proportion is higher.

As can be seen from the test data of examples 8 and 10-11, when the mass ratio of fly ash to mineral powder in the admixture is 1:2, the ratio between the fly ash and the mineral powder is better, and the prepared steam curing-free precast concrete has higher compressive strength of 11.6MPa, 16.5MPa, 36.3MPa and 39.9MPa respectively after the compressive strength test of the concrete, and has smaller slump and 86mm, which indicates that when the mass ratio of the fly ash to the mineral powder in the admixture is 1:2, the prepared steaming-free precast concrete has higher early strength.

The test data of example 11 and examples 12-14 show that the compressive strength of the non-autoclaved precast concrete is improved after the nano-silica is added into the raw materials, which indicates that the nano-silica can improve the mechanical strength of the non-autoclaved precast concrete. When the addition amount of the nano silicon dioxide is 10kg, the prepared steam curing-free precast concrete has higher compressive strength of 16h, 1d, 5d and 28d after the compressive strength test of the concrete, respectively reaches 11.9MPa, 16.7MPa, 36.7MPa and 40.3MPa, and has smaller slump and 83mm slump.

As can be seen from the detection data of the examples 14 and 15, when the water reducer in the raw materials adopts the early-strength polycarboxylic acid high-performance water reducer, the compressive strength of the prepared non-autoclaved precast concrete is higher, and after the compressive strength test of the concrete, the compressive strengths of 16h, 1d, 5d and 28d respectively reach 12.2MPa, 17.0MPa, 36.9MPa and 40.7MPa, and the slump is smaller at the moment and 80mm.

As can be seen from the detection data of the example 1 and the comparative example 1, when the addition amount of the compound early-strength admixture is 0, the compressive strength of the prepared non-autoclaved precast concrete is reduced, the slump is increased, and the fact that the compound early-strength admixture can effectively improve the early strength of the non-autoclaved precast concrete is demonstrated.

As can be seen from the detection data of the embodiment 1 and the comparative examples 2-3, when the addition amount of the fly ash or the mineral powder in the admixture is 0, the compressive strength of the prepared steam curing-free precast concrete is reduced in each period, which indicates that the fly ash and the mineral powder in the admixture have a synergistic effect, and the compressive strength of the steam curing-free precast concrete can be effectively improved.

The present embodiment is merely illustrative of the present application and is not intended to be limiting, and those skilled in the art, after having read the present specification, may make modifications to the present embodiment without creative contribution as required, but is protected by patent laws within the scope of the claims of the present application.

Claims (8)

1. The steam curing-free precast concrete is characterized by comprising the following raw materials in parts by weight: 240-320 parts of Portland cement, 950-1050 parts of coarse aggregate, 800-850 parts of fine aggregate, 60-80 parts of admixture, 8-15 parts of compound early strength admixture, 6-8 parts of water reducer and 160-180 parts of water; the compound early-strength admixture comprises aluminum calcium sulfate cement, calcium formate, triethanolamine, calcium aluminate and a retarder.

2. The non-autoclaved precast concrete as recited in claim 1, wherein: the steam curing-free precast concrete comprises the following raw materials in parts by weight: 260-300 parts of Portland cement, 980-1000 parts of coarse aggregate, 820-840 parts of fine aggregate, 65-75 parts of admixture, 10-12 parts of compound early strength admixture, 6.5-7.5 parts of water reducer and 165-170 parts of water.

3. The non-autoclaved precast concrete as recited in claim 1, wherein: the compound early strength admixture comprises the following raw materials in parts by weight: 60-100 parts of calcium aluminum sulfate cement, 4-5.5 parts of calcium formate, 3-4 parts of triethanolamine, 12-15 parts of calcium aluminate and 1.5-3.5 parts of retarder.

4. The non-autoclaved precast concrete as recited in claim 1, wherein: the admixture consists of fly ash and mineral powder.

5. The non-autoclaved precast concrete of claim 4, wherein: the mass ratio of the fly ash to the mineral powder is 1: (0.5-2).

6. The non-autoclaved precast concrete as recited in claim 1, wherein: the raw materials also comprise 5-15 parts by weight of nano silicon dioxide.

7. The non-autoclaved precast concrete as recited in claim 1, wherein: the water reducer is a polycarboxylic acid high-performance water reducer or an early-strength polycarboxylic acid high-performance water reducer.

8. A non-autoclaved precast concrete as claimed in any one of claims 1 to 7, characterized in that: which comprises the following steps:

1) Mixing the coarse aggregate and the fine aggregate, and stirring for 1-3min to obtain a first mixture;

2) Adding Portland cement, an admixture, a compound early strength admixture, a water reducing agent and 3/4 of water into the first mixture, and stirring for 5-15min to obtain a second mixture;

3) And adding the rest 1/4 of water into the second mixture, mixing and stirring for 1-2min to obtain the steam curing-free precast concrete.