High-moisture-retention anti-cracking concrete and preparation method thereof

Abstract

The invention discloses high-moisture-retention anti-cracking concrete and a preparation method thereof. The high-moisture-retention anti-cracking concrete is prepared from the following raw materials in parts by weight: 210 to 240 parts of cement, 55 to 75 parts of fly ash, 130 to 160 parts of slag, 550 to 740 parts of sand, 380 to 510 parts of fine aggregate, 590 to 780 parts of coarse aggregate, 140 to 160 parts of water, 1.7 to 3.2 parts of polycarboxylate water reducing agent and 0.4 to 1.0 part of temperature rise regulating material, and the thickness of a heat-preservation moisture-retention coating is 200 to 500 microns; the external heat and moisture preservation coating is adopted to inhibit water loss in the concrete and reduce external large temperature difference interference, meanwhile, the temperature rise regulation and control material is internally doped to regulate and control the hydration process of the cementing material, rapid increase of temperature rise in the concrete is inhibited, and severe change of temperature stress inside and outside the concrete and the service environment temperature is inhibited. The high-moisture-retention anti-cracking concrete disclosed by the invention has a wide application prospect.

Description

Technical Field

[0001] The invention relates to a high-moisture-retaining and crack-resistant concrete and a preparation method thereof, belonging to the technical field of building materials. Background Art

[0002] The temperature in plateau and Gobi regions changes dramatically, with a day-night temperature difference of more than 20°C and a seasonal temperature difference of more than 40°C. Large temperature differences have an adverse effect on the hydration process and microstructural evolution of cement, and can easily lead to damage cracks in early-age concrete, providing a convenient channel for the entry of corrosive media.

[0003] During the construction phase, low hydration temperature significantly reduces the hydration rate of early-age concrete, and even causes hydration to stop. In addition, the internal and external temperature difference formed during the heat release of cement hydration causes the concrete material to be compressed internally and tensile externally. Under the influence of strong winds, it is very easy to induce early cracks on the concrete surface. During the operation phase, the large external temperature difference causes nonlinear temperature distribution, and excessive temperature stress causes cracks in the main concrete structure under concrete use. At the same time, strong winds will reduce the humidity of the concrete surface during the construction phase, leading to the redistribution of humidity on the concrete surface inside the fresh concrete, and the sand carried by the strong wind will erode the concrete surface during the operation phase, causing initial damage such as microcracks.

[0004] In the environment of large temperature difference and strong wind and sand, special admixtures such as anti-cracking agent and antifreeze agent are often added to concrete with high strength, high crack resistance and high durability to improve the comprehensive performance of concrete. For example, the problems of prolonged setting time and slow strength growth of concrete under large temperature difference conditions are currently mainly alleviated by reasonable arrangement of construction time and strengthening of moisture retention and maintenance. Faced with the complex and changeable environmental conditions in the northwest region, a single type of control technology is difficult to meet the actual engineering needs. Therefore, multiple types of control technologies are urgently needed to synergistically improve the high moisture retention and crack resistance of concrete. Summary of the invention

[0005] In view of the above deficiencies in the prior art, the present invention provides a highly moisturizing and crack-resistant concrete and a preparation method thereof. An external thermal insulation and moisture-retaining coating is used to inhibit the loss of water inside the concrete and reduce external large temperature difference interference. At the same time, an internal temperature rise regulating material is added to regulate the hydration process of the cementitious material, thereby inhibiting the rapid increase in temperature rise inside the concrete, thereby inhibiting the temperature stress inside and outside the concrete and the drastic changes in the service environment temperature.

[0006] The technical solution adopted by the present invention is: a highly moisture-retaining and crack-resistant concrete, wherein the weight fractions of raw materials thereof include 210-240 parts of cement, 55-75 parts of fly ash, 130-160 parts of slag, 550-740 parts of sand, 380-510 parts of fine aggregate, 590-780 parts of coarse aggregate, 140-160 parts of water, 1.7-3.2 parts of polycarboxylate water reducer, and 0.4-1.0 parts of temperature rise control material;

[0007] The thickness of the thermal insulation and moisture-retaining coating of the highly moisture-retaining and crack-resistant concrete is 200-500 microns.

[0008] The method for preparing the above-mentioned high moisture-retaining and crack-resistant concrete comprises the following steps:

[0009] (1) According to the raw material ratio, the weight fraction of the raw materials includes 210-240 parts of cement, 55-75 parts of fly ash, 130-160 parts of slag, 550-740 parts of sand, 380-510 parts of fine aggregate, 590-780 parts of coarse aggregate, 140-160 parts of water, 1.7-3.2 parts of polycarboxylate water reducer, and 0.4-1.0 parts of temperature rise control material; the weighed cement, fly ash, slag and sand are placed in a concrete mixer and stirred to make various dry materials and temperature rise control materials fully mixed; then fine aggregate and coarse aggregate are added to make them fully mixed; then water and polycarboxylate water reducer are added, and stirring is continued to make the materials mixed evenly to form concrete slurry, and then the slurry is placed in a mold for curing. After demolding, a heat preservation and moisture-reducing coating is applied according to environmental requirements and dried to form a high moisture-retaining and crack-resistant concrete product;

[0010] (2) The temperature rise control material is an internal admixture and is added during concrete preparation;

[0011] (3) After the concrete solidifies and hardens, the thermal insulation and moisture-retaining coating is sprayed on the surface with a thickness of 200-500 microns according to environmental requirements;

[0012] (4) Humidity sensors are embedded in the concrete preparation process to monitor the development of early internal humidity of concrete and simultaneously measure the development of compressive strength at different ages. The curing environment is set as standard curing and variable temperature curing. The standard curing condition is that the temperature should be maintained at (20±1)℃ and the relative humidity is greater than 95%. The variable temperature curing condition is set as follows: the first step is to cool down from 15℃ to -15℃ at a constant speed within 6 hours, and then maintain -15℃ for 6 hours. The third step is to cool from -15℃ to 15℃ at a constant speed within 6 hours, and then maintain +15℃ for 6 hours. One cycle is 24 hours. The humidity is set to 30% until the test age is reached for testing.

[0013] Preferably, in the above-mentioned method for preparing highly moisturizing and crack-resistant concrete, the thermal insulation and moisture-retaining coating is the outer protective material, and a water-soluble polymer with good ductility, resistance to bending and tension, resistance to aging, and adjustable rigidity and flexibility is formed by introducing water-soluble functional groups into isocyanate; the synthesis methods of addition, chain extension, neutralization, and emulsification are designed mainly according to the properties of the raw materials to prepare an anionic carboxylic acid type water-based polyurethane emulsion suitable for cement concrete.

[0014] Preferably, in the above-mentioned method for preparing highly moisturizing and crack-resistant concrete, the temperature rise regulating material is an internal admixture, which is a hydration temperature rise regulating material with adjustable water solubility and setting time formed by introducing water-soluble functional groups into macromolecular polymers; mainly small molecular organic substances such as citric acid are introduced into large molecular weight starch, chitosan, dextrin and other organic substances through acylation reaction to introduce hydrophilic groups such as small molecular groups -COOH to increase their solubility.

[0015] Beneficial effects of the present invention:

[0016] The present invention uses an external thermal insulation and moisture-retaining coating to inhibit the loss of water inside the concrete and reduce the external large temperature difference interference, thereby ensuring the rapid development of early strength. The internal temperature rise regulating material regulates the hydration process of the cementitious material, inhibits the rapid increase of temperature rise inside the concrete, reduces the temperature stress inside and outside the large volume of concrete, and achieves the dual effects of inhibiting the relief of temperature stress inside and outside the concrete and stabilizing the temperature of the service environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 The strength change of high moisture-retaining and crack-resistant concrete in test experiment 1 of the present invention;

[0018] Figure 2 This is the humidity change of high moisture retention and crack resistance concrete in test experiment 2 of the present invention. DETAILED DESCRIPTION

[0019] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0020] A highly moisture-retaining and crack-resistant concrete, wherein the raw materials thereof include by weight 210-240 parts of cement, 55-75 parts of fly ash, 130-160 parts of slag, 550-740 parts of sand, 380-510 parts of fine aggregate, 590-780 parts of coarse aggregate, 140-160 parts of water, 1.7-3.2 parts of polycarboxylate water reducer, and 0.4-1.0 parts of temperature rise control material;

[0021] The thickness of the thermal insulation and moisture-retaining coating of the highly moisture-retaining and crack-resistant concrete is 200-500 microns.

[0022] The method for preparing the above-mentioned high moisture-retaining and crack-resistant concrete comprises the following steps:

[0023] (1) According to the raw material ratio, the weight fraction of the raw materials includes 210-240 parts of cement, 55-75 parts of fly ash, 130-160 parts of slag, 550-740 parts of sand, 380-510 parts of fine aggregate, 590-780 parts of coarse aggregate, 140-160 parts of water, 1.7-3.2 parts of polycarboxylate water reducer, and 0.4-1.0 parts of temperature rise control material; the weighed cement, fly ash, slag and sand are placed in a concrete mixer and stirred to make various dry materials and temperature rise control materials fully mixed; then fine aggregate and coarse aggregate are added to make them fully mixed; then water and polycarboxylate water reducer are added, and stirring is continued to make the materials mixed evenly to form concrete slurry, and then the slurry is placed in a mold for curing. After demolding, a heat preservation and moisture-reducing coating is applied according to environmental requirements and dried to form a high moisture-retaining and crack-resistant concrete product;

[0024] (2) The temperature rise control material is an internal admixture and is added during concrete preparation;

[0025] (3) After the concrete solidifies and hardens, the thermal insulation and moisture-retaining coating is sprayed on the surface with a thickness of 200-500 microns according to environmental requirements;

[0026] (4) Humidity sensors are embedded in the concrete preparation process to monitor the development of early internal humidity of concrete and simultaneously measure the development of compressive strength at different ages. The curing environment is set as standard curing and variable temperature curing. The standard curing condition is that the temperature should be maintained at (20±1)℃ and the relative humidity is greater than 95%. The variable temperature curing condition is set as follows: the first step is to cool down from 15℃ to -15℃ at a constant speed within 6 hours, and then maintain -15℃ for 6 hours. The third step is to cool from -15℃ to 15℃ at a constant speed within 6 hours, and then maintain +15℃ for 6 hours. One cycle is 24 hours. The humidity is set to 30% until the test age is reached for testing.

[0027] Example 1

[0028] To prepare highly moisture-retaining and crack-resistant concrete, the components are mixed in the following mass ratio: cement: fly ash: slag: sand: fine aggregate: coarse aggregate: water: polycarboxylate water reducer = 225: 67.5: 157.5: 692: 450: 692: 156: 2.0, wherein the amount of polycarboxylate water reducer is adjusted according to the fluidity on site. The amount of temperature rise control material is 0.2%, the thickness of the thermal insulation and moisture-retaining coating is 200 microns, and after standard curing for 24 hours, demoulding is performed for variable temperature curing, which is marked as Example 1.

[0029] Example 2

[0030] To prepare highly moisture-retaining and crack-resistant concrete, the components are mixed in the following mass ratio: cement: fly ash: slag: sand: fine aggregate: coarse aggregate: water: polycarboxylate water reducer = 225: 67.5: 157.5: 692: 450: 692: 156: 2.0, wherein the amount of polycarboxylate water reducer is adjusted according to the fluidity on site. The amount of temperature rise control material is 0.3%, the thickness of the thermal insulation and moisture-retaining coating is 200 microns, and after standard curing for 24 hours, demoulding is performed for variable temperature curing, which is marked as Example 2.

[0031] Example 3

[0032] To prepare highly moisture-retaining and crack-resistant concrete, the components are mixed in the following mass ratio: cement: fly ash: slag: sand: fine aggregate: coarse aggregate: water: polycarboxylate water reducer = 225: 67.5: 157.5: 692: 450: 692: 156: 2.0, wherein the amount of polycarboxylate water reducer is adjusted according to the fluidity on site. The amount of temperature rise control material is 0.2%, the thickness of the thermal insulation and moisture-retaining coating is 300 microns, and after standard curing for 24 hours, demoulding is performed for variable temperature curing, which is marked as Example 3.

[0033] Example 4

[0034] To prepare highly moisture-retaining and crack-resistant concrete, the components are mixed in the following mass ratio: cement: fly ash: slag: sand: fine aggregate: coarse aggregate: water: polycarboxylate water reducer = 225: 67.5: 157.5: 692: 450: 692: 156: 2.0, wherein the amount of polycarboxylate water reducer is adjusted according to the fluidity on site. The amount of temperature rise control material is 0.2%, the thickness of the thermal insulation and moisture-retaining coating is 400 microns, and after standard curing for 24 hours, demoulding is performed for variable temperature curing, which is marked as Example 4.

[0035] Comparative Example 1

[0036] To prepare highly moisturizing and crack-resistant concrete, the components are mixed in the following mass ratio: cement: fly ash: slag: sand: fine aggregate: coarse aggregate: water: polycarboxylate water reducer = 225: 67.5: 157.5: 692: 450: 692: 156: 2.0, wherein the amount of polycarboxylate water reducer is adjusted according to the fluidity on site. The amount of temperature rise control material is 0.2%, and standard curing is performed after demoulding for 24 hours, which is marked as comparative example 1.

[0037] Comparative Example 2

[0038] To prepare highly moisturizing and crack-resistant concrete, the components are mixed in the following mass ratio: cement: fly ash: slag: sand: fine aggregate: coarse aggregate: water: polycarboxylate water reducer = 225: 67.5: 157.5: 692: 450: 692: 156: 2.0, wherein the amount of polycarboxylate water reducer is adjusted according to the fluidity on site. The amount of temperature rise control material is 0.3%, and after standard curing for 24 hours, demoulding is performed for variable temperature curing, which is marked as comparative example 2.

[0039] Comparative Example 3

[0040] To prepare highly moisture-retaining and crack-resistant concrete, the components are mixed in the following mass ratio: cement: fly ash: slag: sand: fine aggregate: coarse aggregate: water: polycarboxylate water reducer = 225: 67.5: 157.5: 692: 450: 692: 156: 2.0, wherein the amount of polycarboxylate water reducer is adjusted according to the fluidity on site. The thickness of the thermal insulation and moisture-retaining coating is 200 microns, and after standard curing for 24 hours, demoulding is performed for variable temperature curing, which is marked as comparative example 3.

[0041] Comparative Example 4

[0042] To prepare highly moisture-retaining and crack-resistant concrete, the components are mixed in the following mass ratio: cement: fly ash: slag: sand: fine aggregate: coarse aggregate: water: polycarboxylate water reducer = 225: 67.5: 157.5: 692: 450: 692: 156: 2.0, wherein the amount of polycarboxylate water reducer is adjusted according to the fluidity on site. The thickness of the thermal insulation and moisture-retaining coating is 300 microns, and after standard curing for 24 hours, demoulding is performed for variable temperature curing, which is marked as comparative example 4.

[0043] Test experiment 1: Figure 1 The strength variation law of high moisture-retaining and crack-resistant concrete is given. In Example 1, the mechanical properties of concrete synergistically regulated by the thermal insulation and moisture-retaining coating and the temperature rise regulating material are significantly better than those of Comparative Examples 1 and 2. Test Experiment 2: Similarly Figure 2 The humidity variation law of highly moisturizing and crack-resistant concrete was given, and the same evolution law was obtained. The humidity inside the concrete of Example 1 was significantly better than the internal humidity content of Comparative Examples 1 and 2, which illustrates the effectiveness of the coordinated control measures of the thermal insulation and moisture-retaining coating and the temperature rise control material.

[0044] The above description is only a preferred embodiment of the present invention and does not limit the technical scope of the present invention. Therefore, any modifications, equivalent changes and modifications made to the above embodiments based on the technical properties of the present invention are within the scope of the technical solution of the present invention.

Claims

1. A highly moisture-retaining and crack-resistant concrete, characterized in that: The raw materials weight fraction of the high moisture-retaining and crack-resistant concrete include 210-240 parts of cement, 55-75 parts of fly ash, 130-160 parts of slag, 550-740 parts of sand, 380-510 parts of fine aggregate, 590-780 parts of coarse aggregate, 140-160 parts of water, 1.7-3.2 parts of polycarboxylate water reducer, and 0.4-1.0 parts of temperature rise control material; The thickness of the thermal insulation and moisture-retaining coating of the highly moisture-retaining and crack-resistant concrete is 200-500 microns.

2. The method for preparing the highly moisturizing and crack-resistant concrete according to claim 1, characterized in that: The following steps are involved: (1) According to the raw material ratio, the weight fraction of the raw materials includes 210-240 parts of cement, 55-75 parts of fly ash, 130-160 parts of slag, 550-740 parts of sand, 380-510 parts of fine aggregate, 590-780 parts of coarse aggregate, 140-160 parts of water, 1.7-3.2 parts of polycarboxylate water reducer, and 0.4-1.0 parts of temperature rise control material; the weighed cement, fly ash, slag and sand are placed in a concrete mixer and stirred to make various dry materials and temperature rise control materials fully mixed; then fine aggregate and coarse aggregate are added to make them fully mixed; then water and polycarboxylate water reducer are added, and stirring is continued to make the materials mixed evenly to form concrete slurry, and then the slurry is placed in a mold for curing. After demolding, a heat preservation and moisture-reducing coating is applied according to environmental requirements and dried to form a high moisture-retaining and crack-resistant concrete product; (2) The temperature rise regulating material is an internal admixture material and is added during the preparation of concrete; (3) The thermal insulation and moisture-retaining coating is sprayed on the surface of the concrete with a thickness of 200-500 microns according to environmental requirements after the concrete solidifies and hardens; (4) Humidity sensors are embedded in the concrete preparation process to monitor the development of early internal humidity of concrete and simultaneously measure the development of compressive strength at different ages. The curing environment is set as standard curing and variable temperature curing. The standard curing condition is that the temperature should be maintained at (20±1)℃ and the relative humidity is greater than 95%. The variable temperature curing condition is set as follows: the first step is to cool down from 15℃ to -15℃ at a constant speed within 6 hours, and then maintain -15℃ for 6 hours. The third step is to cool from -15℃ to 15℃ at a constant speed within 6 hours, and then maintain +15℃ for 6 hours. One cycle is 24 hours. The humidity is set to 30% until the test age is reached for testing.

3. The method for preparing highly moisturizing and crack-resistant concrete according to claim 2, characterized in that: The heat-insulating and moisture-retaining coating is an outer protective material, which is a water-soluble polymer with good ductility, bending and tension resistance, aging resistance, and adjustable rigidity and flexibility, formed by introducing water-soluble functional groups into isocyanate.

4. The method for preparing highly moisturizing and crack-resistant concrete according to claim 2, characterized in that: The temperature rise regulating material is an internally doped material, which is a hydrated temperature rise regulating material with adjustable water solubility and coagulation time formed by introducing water-soluble functional groups into a macromolecular polymer.

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