CN111454036A

CN111454036A - Low thermal expansion concrete and admixture

Info

Publication number: CN111454036A
Application number: CN202010509350.6A
Authority: CN
Inventors: 楼晓刚; 郭亮; 丁盛
Original assignee: Zhejiang Chengyu Environmental Protection New Material Co ltd
Current assignee: Zhejiang Chengyu Environmental Protection New Material Co ltd
Priority date: 2020-06-08
Filing date: 2020-06-08
Publication date: 2020-07-28
Anticipated expiration: 2040-06-08
Also published as: CN111454036B

Abstract

The invention relates to a low thermal expansion concrete and an admixture, wherein the concrete comprises cement clinker, fly ash, zeolite powder, granite broken stone and the balance of water, and the cement clinker comprises the following components in percentage by weight: 5-20%, C2S: 20-45%, C3A: 5-10%, and C4 AF: 5-10%, and is characterized in that the cement clinker further comprises 20-40% of barium oxide, 5-15% of strontium oxide, and the cement clinker: (fly ash + zeolite powder): granite macadam =1:1-2:2-4, water: cement clinker = 0.2-0.4. The low-heat micro-expansion concrete is prepared by taking barium oxide and strontium oxide as expansion admixtures for the first time, matching with newly developed retarders, matching with substitute materials of fly ash, particularly zeolite powder, and matching the particle size of granite broken stone aggregate, and finally realizing the low-heat micro-expansion concrete effect.

Description

Low thermal expansion concrete and admixture

Technical Field

The application relates to the field of constructional engineering, in particular to cement/concrete (concrete), and particularly relates to low-heat micro-expansion concrete.

Background

Cement concrete is by far the largest man-made material in the world, and this situation continues for a considerable time into the future. Concrete has two inherent material characteristics, one is the strength increase accompanied by volume deformation-shrinkage in the hydration hardening process, and the other is the low tensile-compression strength ratio of the concrete material. When the tensile stress in the concrete caused by shrinkage exceeds the tensile strength of the concrete, the concrete is broken (cracked). Cracks are generally considered to be the largest defect of concrete structures, which causes the invasion of harmful media such as moisture, CO2, Cl-and the like, accelerates the corrosion of reinforcing steel bars to reduce durability, and causes the reduction or loss of service functions such as water leakage and the like.

The present invention relates to a concrete expansion method, and is characterized by that in 1936L ossier, the expansion of ettringite is used to prepare chemical prestressed concrete, then L afuma and Klein are connected with the above-mentioned research, so that the foundation of expansion cement concrete is laid, and in the American ACI standard, three kinds of expansion cements, i.e. K type, M type and S type are set, and the K type expansion cement is formed from Portland cement and anhydrous calcium sulfoaluminate (3CaO 3. A12O 3. CaSO4, C4A3S), gypsum and calcined lime.

The K-type expansive cement patent was purchased from the United states in Japan in 1962, and on the basis of the K-type expansive cement patent, the calcium sulfoaluminate expansive agent CSA was studied, and the calcium sulfoaluminate expansive agent CSA was commercialized in 1996, and a large amount of researches on the performance and application of the expansive concrete were carried out. Another expanding agent, lime-based expanding agent, was successfully developed in Japan in 1970.

The expansive cement concrete is researched from the beginning of the twentieth century and the fifties, the gypsum vanadine expansive cement based on high-alumina cement and the silicate expansive cement based on ordinary silicate cement are researched and successfully developed in the end of the fifties, two expansive cements with high self-stress values and high impermeability, namely aluminate self-stress cement and sulphoaluminate self-stress cement, are researched and successfully developed on the basis of research on a formation mechanism of ettringite under a low alkalinity condition since the seventies, and the alunite expansive cement is also researched and successfully developed at the same time. The research on the expanding agent is focused for nine eight or five years, and the alunite expanding agent, the anhydrous calcium sulphoaluminate expanding agent, the lime expanding agent, the calcium aluminate expanding agent and the like are successively developed. Therefore, the expanding agent is widely popularized and applied in China.

In addition, a special functional cement concrete is low-heat cement concrete, and research heat tide of low-heat portland cement is caused by global energy shortage. Low heat cement due to the reduced firing temperature, it is expected that less energy will be consumed in producing low heat cement. The preference for low heat cements is increasing as engineers shift the emphasis of concrete design from "strength" to "durability" and low heat cements are believed to produce more durable hydrated substrates than ordinary portland cements. A great deal of research on the low-heat portland cement is carried out by a plurality of experts and scholars at home and abroad, and great achievements are obtained

The early stage hydration process of low-heat silicate Cement is researched by Kazuhiro Mori et al, which shows that the low-heat silicate Cement has low freezing resistance, good impermeability and excellent durability compared with the traditional silicate Cement, and the result shows that the low-heat silicate Cement has low early stage hydration rate, low hydration rate and low corrosion rate of Cement slurry (Cezuhiro et al, which is indicated by micro corrosion of Cement sulfate) in the micro Cement slurry (L).

In China, the research of low-heat silicate cement starts from a scientific and technological attack project of 'nine-five-point engineering concrete safety research' in China, reaches a project of a national 'fifteen' key scientific and technological attack plan, and then reaches a research of low-heat dam cement for high-altitude and high-cold areas on the special subject of national western action in 2006, lasts for 10 years, is successfully researched and developed by a national building material scientific research institute, and is successively applied to large hydraulic engineering such as a diversion bottom hole, a tongpen hydroelectric station, a national ferry river deep creek power station and the like in the second-stage engineering of the three gorges. Then, more related performance and application researches of the low-heat portland cement are gradually carried out in China.

The low-heat silicate cement is environment-friendly and energy-saving cement with low hydration heat, high strength, high durability, low dry shrinkage and good volume stability, and the concrete has good working performance, mechanical property, thermal property and high durability. The low-heat silicon cement has low early strength, so that the application and popularization of the low-heat silicon cement in practical engineering are influenced to a certain extent.

The extensive research and development of expanded concrete, low heat concrete, and low heat expansion concrete, as described above, by engineers at home and abroad, and numerous patented technologies have been developed, and for this, US8242038B2 discloses a low heat expansion high strength honeycomb concrete suitable for use in a cement mixture for use with a ceramic honeycomb, for example, for forming an outer layer on the periphery of the honeycomb, or for forming plugs in the honeycomb. The cement mixture preferably exhibits a low coefficient of thermal expansion and high strength when fired. The cement mixture can be applied to a green honeycomb body and fired with the green body, or can be applied to an already fired ceramic honeycomb body and then fired. Comprising a cementitious mixture comprising a plurality of inorganic components including talc, kaolin, alumina, silica and aluminium hydroxide, wherein the mixture comprises less than or equal to 18.0% silica and greater than or equal to 17.0% aluminium hydroxide, by weight of inorganic constituents. Another U.S. patent, US10/828222, relates to the preparation of specific swelling agents, including a blending step, a reaction step and a calcination step. The mixing step is to add soluble calcium sulphate, soluble calcium oxide and soluble aluminium compounds, such as aluminium dross. The addition of water with the above bound materials to ettringite is a so-called reaction step. The calcination step is to calcine the product resulting from the reaction step at a temperature in the range of 60 ℃ to 900 ℃ by separately converting ettringite from amorphous to calcium sulphoaluminate. After calcination, the final product can be used as an expansion additive for cement or concrete. In addition, the manufacturing method can effectively reduce raw material costs and production costs due to the fact that the raw materials are from recycling and do not need to be calcined at high temperatures as compared with other related art.

Korean international application No. PCT/KR2016/012043 provides a raw cement composition comprising portland cement, a carbon mineral, an early strength type expanding agent, and fine blast furnace slag powder. Carbon minerals obtained by reacting carbon dioxide, which is a main cause of greenhouse gases, with the cogeneration plant fly ash are used, and thus the green cement composition has an effect of better reducing the amount of carbon dioxide. Compared with the traditional green cement, the traditional green cement has a simple mixture of fly ash and blast furnace slag micro powder; the combined heat and power generation of the plant fly ash can be effectively utilized, and the problem of conventional raw cement, early strength deterioration and drying shrinkage can be reduced by using the fly ash which is limited in use as a concrete admixture due to the high content of free lime.

International application WO2017137788 provides a delayed expansion cement mix or hydraulic cement slurry comprising an expanding agent having a hydrophobically modified surface and a hydrophobic and/or self-assembling film. Methods of retarding cement expansion include treating the expansion agent with a self-assembling film precursor compound, slurrying with cement and water, and setting and expanding the cement. The cementing process places a mixture or slurry downhole in a location where it hardens and expands.

The Chinese invention patent CN201410738455.3 discloses a low-heat micro-expansion composite cement and a preparation method thereof, wherein, the magnesium oxide expanding agent: 1-8 parts of industrial waste residue: 25-70 parts of Portland cement clinker, 25-70 parts of gypsum and 1-4 parts of gypsum; magnesium oxide expanding agent and silicate in the mixtureThe magnesium oxide expansion cement is prepared by mixing and grinding cement clinker and gypsum, and the specific surface area of the cement is not less than 300m²The magnesium oxide expansive cement and the industrial waste slag are mixed uniformly according to the proportion to prepare composite cement; or the magnesium oxide expanding agent, the cement clinker, the gypsum and the industrial waste residue are proportioned, mixed and ground together to prepare the composite cement, the fineness of the composite cement prepared by the method is that the screen residue of a square-hole sieve with the fineness of 80 microns is less than 10 percent, and the specific surface area is not less than 300m²In terms of/kg. The expansion can be generated in the early stage and the middle and later stages, and the early, middle and later stage shrinkage of the compensated concrete can be met, so that the shrinkage and cracking of the concrete can be prevented.

The research of expansive and low-heat cement concrete by combining the theoretical and engineering boundaries still has the problem of insufficient compensation in early and middle stages, particularly in early stage, so that the concrete is cracked.

Disclosure of Invention

The invention provides a novel low-heat micro-expansion concrete for overcoming the defects: the cement clinker comprises cement clinker, fly ash, zeolite powder, granite broken stone and the balance of water, wherein the cement clinker comprises the following components in percentage by weight: 5-20%, C2S: 20-45%, C3A: 5-10%, and C4 AF: 5-10%, and is characterized in that the cement clinker further comprises 20-40% of barium oxide, 5-15% of strontium oxide, and the cement clinker: (fly ash + zeolite powder): granite macadam =1:1-2:2-4, water: cement clinker = 0.2-0.4.

The retarder is preferably ethylene glycol diethyl ether diamine tetraacetic acid, triethylenetetramine hexaacetic acid, 1, 2-diaminocyclohexane tetraacetic acid and potassium and sodium salts thereof, more preferably ethylene glycol diethyl ether diamine tetraacetic acid and potassium and sodium salts thereof, and most preferably ethylene glycol diethyl ether diamine tetraacetic acid.

The amount of retarder added is 0.03-0.3wt%, particularly preferably 0.05-0.2, most preferably 0.1-0.15wt% of the cement clinker.

The fly ash and the zeolite powder are characterized in that the content ratio of the fly ash to the zeolite powder is 9-19: 1.

The granularity of the granite macadam is 1-20mm, and the grading is as follows: 15-20mm in the ratio of 30-40wt%, and 1-5mm in the ratio of 10-20 wt%.

The invention also provides a method for using granite macadam in concrete, which has the grain diameter and the proportion.

Another aspect of the invention is to provide a construction structure, a method of construction of an engineering structure, a building, preferably a dam, a building or the like, using the concrete of the aforementioned characteristics.

Detailed description and advantageous effects of the invention:

1. the barium oxide and the strontium oxide are novel low-heat micro-expansion admixtures newly researched by the inventor, and have relatively stable expansion rates in the proportion of 20-40% of barium oxide and 5-15% of strontium oxide; the experiments were detailed in the net expansion ratio test of table 2.

2. After addition of fly ash and zeolite powder, it was unexpected to reduce the heat of hydration by about 30% more, with less shrinkage at the early, middle and late stages, as in example 1 and comparative example 2.

3. Cement hydration is an exothermic process. Because the concrete thermal conductivity is poor, the heat released by hydration of cement in mass concrete cannot be discharged in time, so that the internal temperature is higher, the surface of the concrete structure dissipates heat relatively fast, and the temperature is slightly higher than the outside temperature. Thus, large temperature difference exists between the inside and the outside of the mass concrete, and temperature gradient is generated. Concrete has the nature of expansion with heat and contraction with cold like other building materials, and the temperature gradient causes internal stress. Generally, the surface part is under tension stress, and when the strength of concrete is low, cracks are easy to generate, and the cracks are generally called temperature cracks. The invention delays the hydration rate of cement by adding the retarder, thereby having remarkable effects of reducing the hydration heat temperature rise rate in concrete, reducing the internal temperature rise and preventing temperature rise cracking, and three novel retarder applicable materials are developed, which have better effects than the common tartaric acid and ethylenediamine tetraacetic acid retarder materials, specifically, as examples 1-3, and comparative examples 3 and 4, the time of the exothermic peak is obviously delayed, the internal temperature of concrete is obviously reduced, and the difference with the organic acid retarder generally considered in the field is not more than 0.5 degrees.

4. Granite rocks with high thermal conductivity are selected, the influence of granularity on shrinkage is researched through gradation, the condition that the shrinkage is low and basically stable after 28 days is achieved within the gradation range of the granite rocks, and if the shrinkage is lower than the proportion, the shrinkage is changed badly, as can be seen in table 3. The addition of 50% of 15-20mm and 5% of 1-5mm, the balance being other particle sizes, is significantly less effective than the examples of the present invention.

The specific implementation mode is as follows:

examples 1-3, comparative examples 1-5, were prepared according to the general concrete process and curing, according to the mix ratios of table 1. The results of the specific experiments are shown in tables 1-3.

TABLE 1

Note 1: the raw materials in the table are by weight, and the selected unit is kg.

TABLE 2 determination of Net dilatancy test results (ref. JC/T313-2009)

TABLE 3 shrinkage test results

	7day	14 day	28day	1 Month	6 Month
						Example 2	0.029	0.038	0.050	0.053	0.055
Comparative example 5	0.041	0.051	0.061	0.071	0.081

Although the present invention has been described with reference to various embodiments, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention, and therefore, the scope of the invention is to be determined by the appended claims.

Claims

1. The low-heat micro-expansion (concrete) concrete comprises cement clinker, fly ash, zeolite powder, granite broken stone and the balance of water, wherein the cement clinker comprises the following components in percentage by weight: 5-20%, C2S: 20-45%, C3A: 5-10%, and C4 AF: 5-10%, characterized in that the cement clinker also comprises 20-40% of admixture barium oxide and 5-15% of strontium oxide; cement clinker: (fly ash + zeolite powder): granite macadam =1:1-2:2-4, water: cement clinker = 0.2-0.4.

2. The concrete according to claim 1, further comprising a retarder, wherein the retarder is preferably ethylene glycol diethyl diamine tetraacetic acid, triethylenetetramine hexaacetic acid, 1, 2-diaminocyclohexane tetraacetic acid and potassium and sodium salts thereof, more preferably ethylene glycol diethyl diamine tetraacetic acid and potassium and sodium salts thereof, and most preferably ethylene glycol diethyl diamine tetraacetic acid.

3. Retarder according to claim 2, characterized in that the retarder is added in an amount of 0.03-0.3wt%, particularly preferably 0.05-0.2, most preferably 0.1-0.15wt% of the cement clinker.

4. The fly ash and zeolite powder of claim 1, wherein the ratio of the fly ash to the zeolite powder is 9-19: 1.

5. The granite macadam of claim 1 having a particle size of 1-20 mm.

6. The particle size of claim 5, graded as: 15-20mm in the ratio of 30-40wt%, and 1-5mm in the ratio of 10-20 wt%.

7. Granite crushed stone for use in concrete, further preferably low thermal expansion concrete, further wherein the granite crushed stone preferably has a particle size according to claim 5, further preferably the grading of claim 6.

8. A construction article characterized by comprising the subject application as claimed in claims 1-7.

9. A method of construction of a project, characterized in that the subject matter claimed in the preceding claims 1-8 is applied thereto.

10. A building, preferably a dam, a building or the like, characterised by the use of a construction method according to claim 9 and/or by the use of a structural element according to claim 8 and/or by the use of a concrete according to claims 1-7.