Gypsum slag cement volume shrinkage control agent and preparation method thereof

Abstract

The application discloses a gypsum-slag cement volume shrinkage control agent and a preparation method thereof. The preparation method comprises a sulfoaluminate cement clinker, alkali powder, modified zeolite powder, siloxane powder and nano-composite material powder. The mass ratio of the sulfoaluminate cement clinker, alkali powder, modified zeolite powder, siloxane powder and nano-composite material powder is 1:0.1-1.0:0.5-2.0:0.1-0.5:0.05-0.3. The volume shrinkage control agent can effectively solve the problem that the gypsum-slag cement concrete is prone to shrinkage and cracking in the later period, thereby leading to poor durability.

Description

Technical Field

[0001] The invention belongs to the technical field of cement volume shrinkage control agents, and particularly relates to a gypsum slag cement volume shrinkage control agent and a preparation method thereof. Background Art

[0002] Gypsum slag cement, also known as supersulfated cement or slag sulfate cement, consists of a minimum of 90% total mineral powder and calcium sulfate, with a minimum of 75% mineral powder and a minimum of 10% Portland cement clinker, lime, and other ingredients. The hydration reaction is as follows:

[0003] (1)

[0004] (2)

[0005] The main hydration products are ettringite (AFt) and CSH. AFt provides early strength, while CSH primarily provides late strength. Equations (1) and (2) show that the hydration products of gypsum slag cement are similar to those of Portland cement, and its 28-day volume shrinkage is also comparable to that of ordinary Portland cement, at approximately 0.04-0.1%. However, cement concrete is prone to volume shrinkage in the late stage, leading to cracking and affecting its performance.

[0006] Shrinkage of cement concrete is one of the main causes of cracking and poor durability in later stages of construction. Therefore, improving the volume stability of gypsum slag cement is of great practical significance for its use in engineering applications. Summary of the Invention

[0007] In view of the above-mentioned deficiencies in the prior art, the present invention provides a gypsum slag cement volume shrinkage control agent and a preparation method thereof, which can effectively solve the problem that gypsum slag cement concrete is prone to shrinkage and cracking in the later stage, thereby leading to poor durability.

[0008] To achieve the above-mentioned purpose, the technical solution adopted by the present invention to solve the technical problem is:

[0009] A gypsum slag cement volume shrinkage control agent comprises sulphoaluminate cement clinker, alkali powder, modified zeolite powder, siloxane powder and nanocomposite material powder, wherein the mass ratio of the sulphoaluminate cement clinker, alkali powder, modified zeolite powder, siloxane powder and nanocomposite material powder is 1:0.1-1.0:0.5-2.0:0.1-0.5:0.05-0.3.

[0010] Furthermore, the mass ratio of sulphoaluminate cement clinker, alkali powder, modified zeolite powder, siloxane powder and nanocomposite material powder is 1:0.3:1.0:0.3:0.3.

[0011] Furthermore, the modified zeolite powder is prepared by the following method: adding calcium fluoride powder to zeolite powder, mixing well, calcining, naturally cooling, and then grinding to obtain the modified zeolite powder.

[0012] Furthermore, the addition amount of calcium fluoride is 0.5-1.0%, the calcination temperature is 500-600° C., and the calcination time is 1-2 hours.

[0013] Furthermore, the specific surface area of ​​the powder after grinding is greater than 600m 2 / kg.

[0014] Furthermore, the alkali powder includes at least one of calcium hydroxide powder, potassium hydroxide powder and sodium hydroxide powder.

[0015] Furthermore, the nanocomposite material is a mixture of nano zirconium dioxide and nano calcium oxide, and the particle size is 1-100 nm.

[0016] Furthermore, the mass ratio of nano zirconium dioxide to nano calcium oxide is 1:1-3.

[0017] Furthermore, the content of the shrinkage control agent in the gypsum slag cement is 4-10%.

[0018] The preparation method of the above-mentioned gypsum slag cement volume shrinkage control agent comprises the following steps:

[0019] (1) uniformly mixing aluminum sulfate cement clinker and nanocomposite material powder to prepare composite powder;

[0020] (2) The composite powder in step (1) is mixed evenly with the remaining raw materials.

[0021] The beneficial effects produced by the present invention are:

[0022] The volume shrinkage control agent in the present invention not only controls the alkalinity and hydration degree of gypsum slag cement, but also exerts shrinkage control effects in the following three aspects: first, it reduces the water loss rate of the hardened body and minimizes drying shrinkage; second, the water storage carrier in the volume shrinkage control agent slowly releases water during the hydration process of the gypsum slag cement, ensuring late hydration and improving the density of the hardened body; third, it achieves shrinkage compensation by generating a hardened structure through chemical reaction. The specific principles are as follows:

[0023] The alkali powder used in the shrinkage control agent of the present invention is mainly used to control the alkalinity during the cement hydration and hardening process, thereby promoting cement hydration. The siloxane powder used has a small molecular structure and can deeply penetrate into the capillary wall of gypsum slag cement, chemically reacting with the hydrated cement to form an interpenetrating polysiloxane network structure. While maintaining breathability, it protects the cement component structure from corrosion, effectively reduces the water absorption rate and water loss rate of the gypsum slag cement capillary pores, and reduces the shrinkage problem caused by water loss.

[0024] The modified zeolite powder has a porous structure and a certain water storage capacity, and can act as a water storage carrier. The hydration rate of gypsum slag cement is slow. As hydration proceeds, the free water content in the hardened gypsum slag cement body gradually decreases, and the relative humidity decreases. At this time, the water stored in the modified zeolite powder is gradually released into the matrix to compensate for the shrinkage problem of the matrix caused by the decrease in moisture content, thereby reducing the shrinkage rate of the hardened gypsum cement body and playing a role in resisting shrinkage. The zeolite powder is modified with calcium fluoride during use. Calcium fluoride is added to the zeolite powder as a mineralizer, which can reduce the reaction temperature of the zeolite powder lattice destruction, so that the crystal structure of the zeolite powder can be destroyed at a lower calcination temperature. The surface of the calcined zeolite powder particles is smoother, the friction interaction between the particles is weaker, and the impact on the working performance of the gypsum slag cement mixture is smaller. At the same time, the water storage and release capacity of the modified zeolite powder is improved, so as to compensate for the shrinkage problem caused by water loss in the hardened gypsum slag cement body.

[0025] Sulphoaluminate cement clinker has the function of accelerating the hydration process of gypsum slag cement. At the same time, it can provide aluminum components. Under the action of mixing water, tricalcium aluminate in the aluminum component first reacts with CaSO4 and calcium hydroxide in gypsum slag cement to form hydrated calcium sulfoaluminate, resulting in volume expansion, which is used to compensate for the problem of macroscopic volume reduction caused by the hydration of gypsum slag cement.

[0026] Nanocomposite materials play a nanopowder filling effect in the gypsum slag cement system, which is used to fill the nanopores of the hardened body and control the shrinkage of the hardened cement body. At the same time, the nanocomposite powder can also play a nucleus role, promote the hydration of the system, improve the density of the system, and control the chemical shrinkage of the system. The specific reaction process is as follows: 3CA+3CaSO4+32H2O→C3A·3CaSO4·32H2O+2(Al2O3·H2O). It can be seen that the problem of controlling shrinkage can be solved by using the above components together. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical solutions 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 intended to limit the present invention. That is, the embodiments described are only part of the embodiments of the present invention, rather than all embodiments.

[0028] Therefore, the detailed description of the embodiments of the present invention provided below is not intended to limit the scope of the invention as claimed, but is merely intended to represent selected embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative work are within the scope of protection of the present invention.

[0029] It should be noted that relational terms such as "first" and "second" are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus. In the absence of further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of other identical elements in the process, method, article, or apparatus comprising the element.

[0030] The features and performance of the present invention are further described in detail below with reference to the embodiments and drawings.

[0031] Example 1

[0032] A gypsum slag cement volume shrinkage control agent comprises sulphoaluminate cement clinker, sodium hydroxide powder, modified zeolite powder, siloxane powder, and a nanocomposite material powder composed of nano-zirconium dioxide and nano-calcium oxide in a mass ratio of 1:1, with a particle size of 1-100 nm. The mass ratio of the sulphoaluminate cement clinker, alkali powder, modified zeolite powder, siloxane powder, and nanocomposite material powder is 1:0.5:1:0.5:0.05, and the shrinkage control agent dosage is 10% of the gypsum slag cement.

[0033] The modified zeolite powder was prepared by the following method: adding calcium fluoride powder to the zeolite powder, the amount of calcium fluoride was 0.5% of the zeolite powder, mixing well, calcining at 500 ° C for 1 hour, cooling naturally and then grinding. The specific surface area of ​​the ground powder was 650m 2 / kg, obtained.

[0034] Example 2

[0035] A gypsum slag cement volume shrinkage control agent comprises sulphoaluminate cement clinker, potassium hydroxide powder, modified zeolite powder, siloxane powder, and a nanocomposite material powder composed of nano-zirconium dioxide and nano-calcium oxide in a mass ratio of 1:2, with a particle size of 1-100 nm. The mass ratio of the sulphoaluminate cement clinker, potassium hydroxide powder, modified zeolite powder, siloxane powder, and nanocomposite material powder is 1:0.1:0.5:0.1:0.08, and the shrinkage control agent is added in an amount of 8% of the gypsum slag cement.

[0036] The modified zeolite powder was prepared by the following method: adding calcium fluoride powder to the zeolite powder, the amount of calcium fluoride was 1.0% of the zeolite powder, mixing well, calcining at 600 ° C for 2 hours, cooling naturally and then grinding. The specific surface area of ​​the ground powder was 680m 2 / kg, obtained.

[0037] Example 3

[0038] A gypsum slag cement volume shrinkage control agent comprises sulphoaluminate cement clinker, calcium hydroxide powder, modified zeolite powder, siloxane powder, and nanocomposite material powder composed of nano-zirconium dioxide and nano-calcium oxide in a mass ratio of 1:3, with a particle size of 1-100 nm. The mass ratio of the sulphoaluminate cement clinker, calcium hydroxide powder, modified zeolite powder, siloxane powder, and nanocomposite material powder is 1:0.3:2:0.3:0.3, and the shrinkage control agent dosage is 4% of the gypsum slag cement.

[0039] The modified zeolite powder was prepared by the following method: adding calcium fluoride powder to the zeolite powder, the amount of calcium fluoride was 0.8% of the zeolite powder, mixing well, calcining at 550 ° C for 1.5 hours, cooling naturally and then grinding. The specific surface area of ​​the ground powder was 700m 2 / kg, obtained.

[0040] Comparative Example 1

[0041] A gypsum slag cement volume shrinkage control agent comprises sulphoaluminate cement clinker, calcium hydroxide powder, siloxane powder, and nanocomposite material powder composed of nano-zirconium dioxide and nano-calcium oxide in a mass ratio of 1:3, with a particle size of 1-100 nm. The mass ratio of the sulphoaluminate cement clinker, calcium hydroxide powder, modified zeolite powder, siloxane powder, and nanocomposite material powder is 1:0.3:1:0.3:0.3, and the shrinkage control agent dosage is 4% of the gypsum slag cement.

[0042] Comparative Example 2

[0043] A gypsum slag cement volume shrinkage control agent comprises sulphoaluminate cement clinker, modified zeolite powder, siloxane powder, and a nanocomposite material powder composed of nano-zirconium dioxide and nano-calcium oxide in a mass ratio of 1:3, with a particle size of 1-100 nm. The mass ratio of the sulphoaluminate cement clinker, modified zeolite powder, siloxane powder, and nanocomposite material powder is 1:1:0.3:0.3, and the shrinkage control agent dosage is 4% of the gypsum slag cement.

[0044] The modified zeolite powder was prepared by the following method: adding calcium fluoride powder to the zeolite powder, the amount of calcium fluoride was 0.8% of the zeolite powder, mixing well, calcining at 550 ° C for 1.5 hours, cooling naturally and then grinding. The specific surface area of ​​the ground powder was 700m 2 / kg, obtained.

[0045] Comparative Example 3

[0046] A gypsum slag cement volume shrinkage control agent comprises sulphoaluminate cement clinker, calcium hydroxide powder, modified zeolite powder, siloxane powder and nano zirconium dioxide powder, with a particle size of 1-100 nm; the mass ratio of sulphoaluminate cement clinker, calcium hydroxide powder, modified zeolite powder, siloxane powder and nano zirconium dioxide powder is 1:0.3:1:0.3:0.3, and the shrinkage control agent dosage is 4% of the gypsum slag cement.

[0047] The modified zeolite powder was prepared by the following method: adding calcium fluoride powder to the zeolite powder, the amount of calcium fluoride was 0.8% of the zeolite powder, mixing well, calcining at 550 ° C for 1.5 hours, cooling naturally and then grinding. The specific surface area of ​​the ground powder was 700m 2 / kg, obtained.

[0048] Comparative Example 4

[0049] A gypsum slag cement volume shrinkage control agent comprises calcium hydroxide powder, modified zeolite powder, siloxane powder, and nano-composite material powder composed of nano-zirconium dioxide and nano-calcium oxide in a mass ratio of 1:3, with a particle size of 1-100 nm; the mass ratio of the calcium hydroxide powder, modified zeolite powder, siloxane powder, and nano-composite material powder is 0.3:1:0.3:0.3, and the shrinkage control agent dosage is 4% of the gypsum slag cement.

[0050] The modified zeolite powder was prepared by the following method: adding calcium fluoride powder to the zeolite powder, the amount of calcium fluoride was 0.8% of the zeolite powder, mixing well, calcining at 550 ° C for 1.5 hours, cooling naturally and then grinding. The specific surface area of ​​the ground powder was 700m 2 / kg, obtained.

[0051] Experimental example

[0052] Taking the cement volume shrinkage control agent in Example 1-3 and Comparative Example 1-4 as an example, it was added to gypsum slag cement, and no substance was added as a control group. The proportion of the components in the gypsum slag cement was: gypsum slag cement, standard sand and polycarboxylic acid water reducer, wherein the sand-cement ratio was 1:1, the water-to-material ratio was 0.12, and the amount of polycarboxylic acid water reducer was 0.5%; gypsum slag cement specimens were prepared, the volume of the gypsum slag cement specimens was measured, and the prepared gypsum slag cement specimens were placed in a cool and dry environment for 28 days. The shrinkage of the gypsum slag cement specimens after 28 days was tested, and the specific results are shown in Table 1.

[0053] Table 1: Gypsum slag cement shrinkage

[0054]

[0055] It can be seen from the data in the above table that the volume shrinkage of the gypsum slag cement specimens prepared by the method in this application is less than 0.03% after being placed for 28 days, while the volume shrinkage of the specimens in the control group without adding any shrinkage control agent is as high as 0.056%, which proves that the gypsum slag cement volume shrinkage control agent in this application can effectively control cement cracking and improve cement durability.

[0056] Although the volume shrinkage rate of the gypsum slag cement specimens prepared by the method in Comparative Examples 1-4 after 28 days of storage is lower than that of the control group, it is much higher than the volume shrinkage rate of the test blocks of the present application; in Comparative Examples 1-4, the use of modified zeolite powder, alkali powder, nano calcium oxide powder and sulfoaluminate cement clinker was eliminated respectively. It can be inferred that each raw material in the present application has a great effect on reducing the shrinkage rate of the specimens.

Claims

1. A gypsum slag cement volume shrinkage control agent, characterized in that: The invention comprises sulphoaluminate cement clinker, alkali powder, modified zeolite powder, siloxane powder and nanocomposite material powder, wherein the mass ratio of the sulphoaluminate cement clinker, alkali powder, modified zeolite powder, siloxane powder and nanocomposite material powder is 1:0.1-1.0:0.5-2.0:0.1-0.5:0.05-0.3; The modified zeolite powder is prepared by the following method: adding calcium fluoride powder to zeolite powder, mixing and calcining, and then naturally cooling and grinding to obtain the modified zeolite powder; the calcium fluoride content is 0.5-1.0%, the calcination temperature is 500-600°C, and the calcination time is 1-2h; The nano-composite material is a mixture of nano-zirconium dioxide and nano-calcium oxide, with a particle size of 1-100 nm; the mass ratio of nano-zirconium dioxide to nano-calcium oxide is 1:1-3.

2. The gypsum slag cement volume shrinkage control agent according to claim 1, characterized in that: The mass ratio of the sulphoaluminate cement clinker, alkali powder, modified zeolite powder, siloxane powder and nanocomposite material powder is 1:0.3:1.0:0.3:0.

3.

3. The gypsum slag cement volume shrinkage control agent according to claim 1, characterized in that: The specific surface area of ​​the powder after grinding is greater than 600m 2 / kg.

4. The gypsum slag cement volume shrinkage control agent according to claim 1, characterized in that: The alkali powder includes at least one of calcium hydroxide powder, potassium hydroxide powder and sodium hydroxide powder.

5. The gypsum slag cement volume shrinkage control agent according to claim 1, characterized in that: The content of the shrinkage control agent in gypsum slag cement is 4-10%.

6. The method for preparing the gypsum slag cement volume shrinkage control agent according to any one of claims 1 to 5, characterized in that: The following steps are involved: (1) uniformly mixing aluminum sulfate cement clinker and nanocomposite material powder to prepare composite powder; (2) The composite powder in step (1) is mixed evenly with the remaining raw materials.

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