CN114804790A

CN114804790A - Ettringite-based energy-storage foam light soil and preparation method and application thereof

Info

Publication number: CN114804790A
Application number: CN202210367279.1A
Authority: CN
Inventors: 张洪智; 邵明扬; 孙仁娟; 齐辉; 葛智; 高辉国; 王其君; 凌一峰; 管延华; 卜令来
Original assignee: Shandong University; Shandong High Speed Group Co Ltd
Current assignee: Shandong University; Shandong High Speed Group Co Ltd
Priority date: 2022-04-08
Filing date: 2022-04-08
Publication date: 2022-07-29

Abstract

The invention relates to ettringite-based energy storage foam light soil and a preparation method and application thereof. The raw materials comprise a cementing material, water and a foam group, wherein the cementing material is a material which generates ettringite after hydration, and the mass ratio of the water to the cementing material is 0.5-0.7, the foaming multiplying power of the foam group is 800-1000, and the standard foam density is 45-55 kg/m ³ The volume of the foam contained in the foam light soil is 50-80%. The foamed light soil can be used as an energy storage material and a structural layer bearing material. The self-shrinkage of cement paste is compensated, the early strength of cement is enhanced, the durability of concrete is improved, and the application requirements can be better met. The energy storage material can melt ice and snow, so that the road surface is as spring in four seasons, and the purpose of ensuring traffic driving safety is achieved.

Description

Ettringite-based energy storage foam light soil as well as preparation method and application thereof

Technical Field

The invention belongs to the technical field of building material preparation, and particularly relates to ettringite-based energy-storage foam light soil and a preparation method and application thereof.

Background

The information in this background section is only for enhancement of understanding of the general background of the invention and is not necessarily to be construed as an admission or any form of suggestion that this information forms the prior art that is already known to a person of ordinary skill in the art.

In cold areas in winter, when the environmental temperature is lower than 0 ℃, the phenomenon of snow accumulation and icing on the road surface can occur, so that the normal traffic order is seriously influenced, traffic safety accidents are easy to happen, and the national economic loss is caused. For the traditional method for melting ice and snow on the road surface, permanent damage to the road surface in different degrees can be caused, the internal structure and durability of the road surface are seriously damaged, and the bridge surface is corroded by steel bars, so that the efficiency is low, the energy consumption is large, and the carbon emission does not meet the background of carbon peak and carbon neutralization at present. Just because the traditional road surface ice and snow melting method has many defects, the existing self-snow melting road surface technology is emphasized by more and more countries and becomes a hot problem of the research of the road boundary. The self-snow-melting technology is used for melting and removing snow through the special functions of the road surface, the ice-melting and snow-removing effects of the technologies which are applied to the road surface at present are more thorough, but the application is relatively less at present because corresponding construction needs to be carried out when the road surface is laid, and the initial investment is larger.

Disclosure of Invention

Aiming at the problems in the prior art, the invention aims to provide an ettringite-based energy storage foam lightweight soil, and a preparation method and application thereof. The invention provides novel ettringite-based phase-change energy-storage foamed lightweight soil which can be used as an energy storage material and a structural layer bearing material.

In order to solve the technical problems, the technical scheme of the invention is as follows:

in the first aspect, the ettringite-based energy-storage foam light soil comprises a cementing material, water and a foam group, wherein the cementing material is a material which generates ettringite after hydration, the mass ratio of the water to the cementing material is 0.5-0.7, the foaming multiplying power of the foam group is 800-1000, and the standard foam density is 45-55 kg/m ³ The volume of the foam contained in the foam light soil is 50-80%.

According to the invention, the binding material is hydrated with water to generate ettringite, and the ettringite has the main functions of: 1) energy storage and heat release are carried out, so that the road surface can melt ice and snow; 2) the ettringite can promote the early strength development and compensate the shrinkage of the cement. The ettringite stores heat and, under high temperature drying conditions, undergoes a dehydration reaction equation of the formula:

the formula of heat release after water absorption and heat release after water absorption of ettringite:

the above dehydration and water absorption processes are reversible reaction processes. The heat-releasing device plays a role in melting ice and snow in the heat-releasing process, and ensures the driving safety of vehicles on the road surface. The foam light soil is energy-storing foam light soil, energy is stored and absorbed and then released, and the cement base is used as a phase-change material, so that the structure-function integration of the material is realized.

The cementing material and water form cement slurry and then are mixed with the foam group to form foam lightweight soil, and a porous structure is formed in the foam lightweight soil. The non-foaming ettringite cement structure can generate cracks after 1-2 cycles due to temperature stress generated by temperature change and stress generated by volume expansion generated after ettringite change. According to the invention, the ettringite product generated by hydration of the sulphoaluminate cement forms a porous system in the concrete, so that the material is stressed uniformly, the internal stress of the material is reduced after foaming, stress concentration is avoided, cracking is reduced, and meanwhile, the transmission rate of heat and humidity can be increased.

In a second aspect, the ettringite-based energy storage foam light soil is applied to roadbed construction.

Because the invention is mainly used for roadbed construction and is in an underground sealing state, ettringite can not react with CO in the air ₂ The carbonization reaction takes place as follows:

3CaO·Al ₂ O ₃ ·3CaSO ₄ ·32H ₂ O+3CO ₂ →3CaCO ₃ +3(CaSO ₄ ·2H ₂ O)+Al ₂ O ₃ ·xH ₂ O+(26-x)H ₂ O

in a third aspect, the preparation method of the ettringite-based energy storage foamed lightweight soil comprises the following steps:

mixing water and a cementing material to obtain cement paste;

mixing a foaming agent and water for foaming to obtain a foam group;

and mixing the foam group with cement slurry to obtain the foam lightweight soil slurry.

One or more technical schemes of the invention have the following beneficial effects:

the foam light soil prepared by the invention has the advantages of light weight, high strength, large rigidity, low compressibility, excellent environmental protection and the like, can relieve vertical load so as to avoid damaging and influencing a bottom structure, and is commonly used as a backfill material for roadbed filling engineering. The ettringite has the characteristics of high temperature rise, high energy density and low material cost, effectively saves the engineering cost and has wide application prospect in the construction of traffic infrastructure. The prepared ettringite-based foam light soil can be used as a structural layer for bearing and storing energy, and is a better solution.

On the basis of foamed light soil, the ettringite is added to compensate the self-shrinkage of cement paste, so that the early strength of cement is enhanced, the durability of concrete is improved, and the application requirements can be better met. The energy storage material can melt ice and snow, so that the road surface is as spring in four seasons, and the purpose of ensuring traffic driving safety is achieved.

The preparation method is simple, realizes the full utilization of cement hydration products, reduces the material cost and effectively saves the engineering cost. Peak clipping and valley filling are performed, the incoordination of energy supply and demand on time and space is relieved, the resource utilization efficiency is improved, and the energy crisis is relieved. The structure-function integration of the material is realized, energy is stored in the building material in a phase change mode, the ettringite is subjected to exothermic reaction when ice and snow melt are needed, and the energy is stored in the ettringite matrix when heat is not needed, so that the material can be used as a structural material and an energy storage unit.

The invention adds proper gypsum mixing amount, effectively quickens the early hydration process of cement. And can prevent the ettringite from being converted into the monothio hydrated calcium sulphoaluminate along with the hydration of tricalcium aluminate in the later period. The gypsum also has the function of retarding the coagulation in the portland cement, can prolong the hydration hardening time of the cement, and enables the fresh concrete to keep plasticity for a long time, thereby adjusting the setting time of the fresh concrete. On the premise of meeting the engineering standard, the components such as air bubbles are used for replacing the cement consumption, so that the resources are saved. The density of the material is reduced by doping the air bubbles, and the harm caused by uneven settlement of the foundation in the roadbed construction can be effectively reduced.

Detailed Description

It is to be understood that the following detailed description is exemplary and is intended to provide further explanation of the invention as claimed. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments according to the present application. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, and it should be understood that when the terms "comprises" and/or "comprising" are used in this specification, they specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof, unless the context clearly indicates otherwise.

The inventor researches and discovers that ettringite serving as a hydrated salt phase-change material has the material energy density of 500kWh/m ³ And its material cost is below 1000% ³ The phase transition temperature is about 55-65 ℃, the phase transition condition is easy to achieve, and the energy storage density is guaranteed. The ettringite has wide sources and is a main hydration product of sulphoaluminate cement and high-alumina cement. The characteristics of high energy density and low material cost make ettringite an excellent phase change energy storage material. The ettringite generates a dehydration reaction equation as shown in the following formula under a high-temperature drying condition, the reaction is a reversible reaction, 600J/Kg heat can be generated in the hydration process, the heat circulation is completed by utilizing the hydration and dehydration processes of the ettringite, and the foamed lightweight soil material is taken as an energy storage medium, so that the structure-function integration of the material is realized.

In some embodiments of the invention, the raw materials of the cementitious material are anhydrite and sulphoaluminate cement, and the molar ratio of the anhydrite to the sulphoaluminate clinker is 0.5-3: 1; preferably 1.5-2.5: 1. The sulphoaluminate clinker is the main component of the sulphoaluminate cement. The ettringite-based energy storage foam light soil prepared by the sulphoaluminate cement can not only bear a structure but also store energy. The hydration of sulphoaluminate cements produces a variety of hydration products, including large amounts of ettringite.

In some embodiments of the invention, the molar ratio of anhydrite to sulphoaluminate clinker is 2:1, and the mass ratio of water to cementitious material is between 0.5 and 0.65.

In some embodiments of the invention, the cementitious material is a cement mixture of portland cement and calcium aluminate cement. The molar ratio of the anhydrite to the cement mixture is 0.5-3: 1; preferably 1.5-2.5: 1.

In some embodiments of the invention, the molar ratio of anhydrite to cement mixture is 2:1 and the mass ratio of water to cementitious material is between 0.5 and 0.65.

The function of adding gypsum into the cementing material is as follows: the proper amount of gypsum can effectively promote the early hydration process of cement, directly influence the generation amount, generation time and shape of the trisulfide hydrated calcium sulphoaluminate in a hydration product, influence the volume stability of slurry and finally directly determine the development of slurry strength. When the gypsum mixing amount is low, along with the hydration of tricalcium aluminate in the later period, ettringite is converted into monothio hydrated calcium sulphoaluminate; when the mixing amount is too high, the later strength of the hardened slurry even shrinks reversely, internal stress is generated in the structure, and the problems of cracking, strength reduction and the like occur. Therefore, in order to realize higher mechanical strength and lower drying shrinkage and ensure the stability of the ettringite generated in the slurry, the proportion of the gypsum to the cement is one molar ratio which can be 0.5, 1, 1.5, 2, 2.5 and 3, the content of the ettringite is different according to different ratios, and the optimal molar ratio is 2 mol.

In some embodiments of the present invention, the volume of the foam contained in the unit foamed lightweight soil is 60% to 70%. Too much foaming agent content and too much foam lead to strength reduction, too little foam does not play a role, and the foam rate of the prepared foam light soil is 60-70%.

In some embodiments of the invention, the volume ratio of blowing agent to water in the foam population is from 1:35 to 45; preferably 1: 40.

In some embodiments of the invention, the foaming agent is a plant foaming agent. According to three performance evaluation indexes of the foaming agent, namely the foaming times, the 1h settling distance and the 1h bleeding rate, the plant foaming agent is selected, the plant foaming agent is found to have stronger foaming capacity, and the plant foaming agent has better market status under the same dilution times from the economic point of view, and the stability of the plant foaming agent is superior to that of the animal protein foaming agent.

In some embodiments of the invention, the foamed lightweight soil has a fluidity of 160mm to 190 mm. Because the foam light soil for highway engineering generally adopts a pumping construction technology, and the pumping distance is long (generally within the range of 300-500 m), under the condition of the same water-gel ratio, the flow value is larger, the flowability of the foam light soil is better, when the flow value of the foam light soil is too large and is larger than 190mm, the stability of the prepared foam light soil can be greatly reduced, and when the flow value is too small, the pumping construction difficulty of the foam light soil can be increased. Therefore, the fluidity of the foamed light soil is high, the slurry is required to reach a certain fluidity, the fluidity is required not to be too high, and otherwise, the quality problems of segregation, bleeding and the like are easy to occur.

mixing water and a cementing material to obtain cement paste;

mixing a foaming agent and water for foaming to obtain a foam group;

In some embodiments of the invention, the water and the cementitious material are mixed to form a cement slurry, with the water and then the cementitious material being added. Avoiding the conversion of the ettringite to the mono-sulfur hydrated calcium sulfoaluminate along with the hydration of tricalcium aluminate at the later stage, adding water into the mixture of the silicate cement and the gypsum during the mixing, fully stirring the mixture to obtain cement paste, and standing the cement paste after the cement paste is uniformly stirred.

In some embodiments of the present invention, the foam group is prepared by mixing a foaming agent and water and foaming the mixture by a foaming device.

The invention will be further illustrated by the following examples

Example 1

1) Preparation of cement slurries

A mixture of ordinary portland cement (20 wt%) (designated C80P20) and pre-mixed calcium aluminate cement containing anhydrite (80 wt%) was used to produce a high ettringite content material. The cement mixture was hydrated with demineralized water, the ratio of water to cement mixture being 1.1. The cement mixture, gypsum and water were added to a mixer and mixed to prepare a cement paste, and the mixing molar ratio of cement and gypsum was controlled to 2. Before mixing, the two materials should be fully mixed to ensure full contact during hydration. In order to avoid the conversion of the ettringite to the mono-sulfur hydrated calcium sulfoaluminate along with the hydration of the tricalcium aluminate at the later stage, water is firstly added during the mixing, then the mixture of the silicate cement and the gypsum is added, the cement paste is obtained by fully stirring, and the mixture is kept stand after being uniformly stirred.

3) Preparation of foam flocks

The foaming ratio of the foaming agent is 1:40, that is, the volume ratio of the foaming agent to water is 1: 40. Water is metered according to the proportion, a foaming agent is added to be mixed and stirred uniformly, and the mixed solution is placed into a foaming device for foaming to prepare foam groups.

4) Energy-storage foam light soil for generating ettringite

Adding the prepared foam group and the ettringite into the slurry, mixing and stirring until the foam is uniformly dispersed in the slurry and floating foam can not be seen on the slurry surface, completing stirring to obtain ettringite energy storage foam light soil slurry, and at the moment, achieving the pouring degree.

5) After casting and compacting the grout, it was covered with a plastic film for 24 hours. Subsequently, the samples were demolded in water at 20 ± 1 ℃ and cured until tested, with a curing relative humidity of 90%. The prepared bubble mixed light soil slurry is prepared into a compression-resistant test piece of 100mm multiplied by 100mm to measure the compression strength. The 3d compressive strength is about 0.5MPa, the 7d compressive strength is about 3.5MPa, the 28d compressive strength is about 4.3MPa, the elastic modulus is 3.03GPa, and the CBR value is 79 percent, thereby meeting the requirement of the foundation bearing capacity specification.

6) The prepared bubble mixed light soil is subjected to energy release and energy storage analysis, the temperature of dehydration reaction and water absorption reaction are respectively 95 ℃ and 20 ℃, the relative humidity is 20.1%, and the heating rate and the water loss rate are both 5.1m ³ The light soil has obvious energy storage advantages under the experimental environment that the water vapor pressure is 2100Pa, and the material energy storage density is about 176kWh/m ³ The average discharging power is 33.3W/kg, and the maximum power density reaches 915W/kg.

Example 1

The method comprises the following steps: and (3) preparing cement slurry, namely using the sulphoaluminate cement to produce a material with high ettringite content. Anhydrous gypsum (CaSO4) and sulphoaluminate cement are mixed according to the molar ratio of the anhydrous gypsum to the sulphoaluminate clinker (main component of the sulphoaluminate cement) of 2:1, and mixing well. Adding cement and water into a special cement stirrer according to the proportion of 0.7 of water-cement ratio. Slowly stirring every 8kg of cement for 6 minutes, and then stirring at a medium speed for 6 minutes to fully stir and fuse the cement and water to obtain cement paste;

step two: foaming by adopting a plant foaming agent, diluting the foaming agent at room temperature, wherein the mass ratio of the foaming agent to water is 1: 40-50, the foaming ratio is 800-1000, and the standard foam density is 45-55 kg/m ³ In the foaming device, a bubble group is formed.

Step three: and (4) generating the foamed light soil, namely mixing the foam with cement slurry. Mixing cement paste with the bubble groups, wherein the volume of the foam contained in unit foam light soil is 60-70%, the water-gel ratio is 0.5-0.65, and the foam concrete with relatively light weight can be prepared, and the stirring speed is 3000 r/min. And finally pouring, forming and maintaining the ettringite-based energy storage foam light soil.

The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. An ettringite-based energy storage foam light soil is characterized in that: the raw materials comprise a cementing material, water and a foam group, wherein the cementing material is a material which generates ettringite after hydration, the mass ratio of the water to the cementing material is 0.5-0.7, the foaming multiplying power of the foam group is 800-1000, and the standard foam density is 45-55 kg/m ³ The volume of the foam contained in the foam light soil is 50-80%.

2. The ettringite-based energy storage foam lightweight soil according to claim 1, characterized in that: the raw materials of the cementing material are anhydrous gypsum and sulphoaluminate cement, and the molar ratio of the anhydrous gypsum to the sulphoaluminate clinker is 0.5-3: 1; preferably 1.5-2.5: 1.

3. The ettringite-based energy storage foam lightweight soil according to claim 2, characterized in that: the molar ratio of the anhydrous gypsum to the sulphoaluminate clinker is 2:1, and the mass ratio of the water to the cementing material is 0.5-0.65.

4. The ettringite-based energy storage foam lightweight soil according to claim 1, characterized in that: the raw materials of the cementing material are portland cement and calcium aluminate cement containing anhydrite.

5. The ettringite-based energy storage foam lightweight soil according to claim 1, characterized in that: the volume of the foam contained in the unit foam light soil is 60 to 70 percent.

6. The ettringite-based energy storage foam lightweight soil according to claim 1, characterized in that: the volume ratio of the foaming agent to the water in the foam group is 1: 35-45; preferably 1: 40.

7. The ettringite-based energy storage foam lightweight soil according to claim 1, characterized in that: the foaming agent is a plant foaming agent.

8. The ettringite-based energy storage foam light soil of claim 1, wherein: the fluidity of the foam light soil is 160mm-190 mm.

9. Use of the ettringite-based energy storage foamed lightweight soil according to any one of claims 1 to 8 in roadbed construction.

10. The method for preparing ettringite-based energy storage foam lightweight soil according to any one of claims 1 to 8, characterized in that: the method comprises the following steps:

mixing water and a cementing material to obtain cement paste;

mixing a foaming agent and water for foaming to obtain a foam group;