CN111943620A

CN111943620A - Slurry curing agent and application thereof

Info

Publication number: CN111943620A
Application number: CN202010691376.7A
Authority: CN
Inventors: 陈维灯; 薛军鹏; 丁晓川; 陈松和; 陈新秀; 陈建科
Original assignee: Fujian Academy Of Building Research Co ltd; Fujian Construction Engineering Group Building Material Science & Technology Development Co ltd
Current assignee: Fujian Academy Of Building Research Co ltd; Fujian Construction Engineering Group Building Material Science & Technology Development Co ltd
Priority date: 2020-07-17
Filing date: 2020-07-17
Publication date: 2020-11-17

Abstract

The invention relates to the field of building materials, in particular to a slurry curing agent, which comprises the following components in parts by weight: 15-20 parts of aluminate cement, 13-19 parts of quicklime, 15-20 parts of bentonite and 47-54 parts of desulfurized gypsum. And the use of the mud curing agent in mud treatment. The invention prepares a curing material which can rapidly react with water and obviously improve the strength of the mud curing soil by compounding the high water absorption material and the inorganic hydraulic material, greatly improves the construction efficiency, simplifies the construction process, and the mud curing soil can be used for building construction roads.

Description

Slurry curing agent and application thereof

Technical Field

The invention relates to the field of building materials, in particular to a slurry curing agent and application thereof.

Background

In the engineering construction process, a large amount of slurry is generated due to the working procedures of excavation, piling and the like. The slurry is a suspension liquid containing a certain amount of fine slurry particles, has a certain viscosity, is difficult to stratify after standing for a long time, and is difficult to store and discard in engineering construction.

The current common treatment methods of engineering waste mud comprise a sedimentation tank method, a flocculation treatment method, an equipment treatment method and the like. The sedimentation tank method is characterized in that a waste slurry sedimentation tank is built on site, then the slurry is transported to an outskirts garbage site by a tank for natural drying, and the sedimentation tank method has the defects of high cost, low efficiency, easy generation of 'dripping, scattering, leaking' and the like and easy generation of secondary pollution. The equipment treatment method is to adopt a horizontal centrifuge to carry out dehydration treatment on the slurry, carry out outward transportation treatment on the mud cakes and recycle the wastewater, and has the defects of complex treatment process, high cost, large occupied area and the like. The flocculation treatment method is that a flocculating agent is added into slurry water, the slurry water is a suspension liquid containing a certain amount of fine slurry particles in the water, and a high molecular flocculating agent is a water-soluble high polymer, so that when the high molecular flocculating agent is mixed with the slurry water, the flocculating agent has the functions of bridging, net catching, adsorption, electric neutralization and the like, the stability of the slurry water can be damaged, and the slurry particles are coagulated and settled from the water, thereby achieving the effect of separating the slurry from the water. But the curing process is complex, the curing speed is slow, and the cured slurry is not easy to be recycled.

In addition, temporary internal construction access roads need to be built on the construction site, earth and stone are purchased outside, the construction access roads need to be dismantled and abandoned outside after construction is finished, and the outside transportation cost and the abandonment cost are also needed. If the waste slurry generated on the construction site is solidified and used as a construction pavement material, the earth outsourcing and disposal cost with the same amount can be reduced.

Disclosure of Invention

The invention aims to solve the technical problem of providing a slurry curing agent and application thereof in curing waste slurry, which can quickly react with waste slurry water when meeting the requirement of site operation time, obviously improve the strength of slurry cured soil, greatly improve the construction efficiency and simplify the construction process.

The invention is realized by the following steps:

the invention firstly provides a slurry curing agent which comprises the following components in parts by weight: 15-20 parts of aluminate cement, 13-19 parts of quicklime, 14-28 parts of bentonite and 47-54 parts of desulfurized gypsum.

Further:

the aluminate cement is a commercially available product which meets the requirements of aluminate cement GB/T201-2015.

The quicklime is calcareous lime which accords with 'building quicklime' JC/T479-2013.

The bentonite is sodium bentonite which accords with bentonite GB/T20973-2007.

The desulfurized gypsum is the desulfurized gypsum meeting the requirement of flue gas desulfurized gypsum GB/T37785-2019 or semi-hydrated gypsum or anhydrous gypsum produced by calcining the desulfurized gypsum serving as a raw material. For cost reasons, the desulfurized gypsum is selected from wet desulfurized gypsum having a water content of less than 15%.

The mass ratio of the bentonite to the aluminate cement is 1-2: 1.

the invention also provides the application of the mud curing agent in curing the waste mud, the mud curing agent is mixed into the waste mud according to 2.5-30% of the mass of the waste mud, the waste mud is uniformly stirred with the mud, and the water content of the waste mud is 50-1000%.

Further:

the mud is firstly mixed with the quicklime and the desulfurized gypsum uniformly according to the proportion, the bentonite and the aluminate cement are mixed uniformly in advance, the two mixtures are mixed uniformly, finally the mixture is mixed uniformly and then can be spread in a construction site required area, and the mixture can be used as a construction access base layer or even a surface layer after 1-3 days.

The principle of the invention is as follows:

the slurry has fluidity, and has the following two main curing mechanisms that the free water among soil particles is too much, the friction among the soil particles is too small, and the soil particles can move freely: one is to make free water discharge out of the slurry system to increase the friction between soil particles; the other method is that the cementing material is added to bond the soil particles, so that the soil particles which can move freely can be bonded into a whole, the slurry is solidified, and the larger the bonding area among the soil particles is, the stronger the integrity among the soil particles is, and the higher the strength is.

Based on the two mechanisms described above, the curing strategy of the present invention was determined: the larger the volume of the gelled substance generated by the selected solidified material per unit mass of the material is, the better the material is, which means that the larger the volume of the gelled substance is, the larger the area covered by the material when the soil particles are bonded is, the stronger the bonding force is and the higher the strength is under the same mass; the larger the specific surface area of the selected solidified material and the final product is, the better the solidified material is, under the same water content, the less the amount of free water, the more the amount of adsorbed water and the higher the bearing capacity of the solidified soil.

Based on the theoretical analysis, the expanded product component ettringite in a cement concrete system is selected as a target hydration product of the curing material, the ettringite reaction is mainly a liquid phase reaction, and the equation is as follows:

2AlO₂ ^-+6Ca²⁺+4OH^-+3SO₄ ^2-+30H₂O→3CaO·Al₂O₃·3CaSO₄·32H₂O

if CaO or Al is used₂O₃、CaO、CaSO₄As raw materials of the curing material, the following raw materials are added according to the proportion of 1: 2: the slurry is solidified after being mixed with the mol ratio of 3, the water content of 85 percent of the mass of the material can be consumed, the ettringite is generated, and if the calcium sulfate is replaced by desulfurized gypsum wet powder with 15 percent of free water (the mol ratio of the calcium sulfate to the calcium oxide and the aluminum oxide in the gypsum is ensured to be unchanged), the water content of 43 percent of the mass of the material can be consumed by the solidified material. Complete hydration may consume about 24% of its own mass of water relative to portland cement. Assuming that the density of the Portland cement is the same as that of the mixture curing agent, under the condition of the same dosage, the mass of a gelled substance generated by the complete hydration of the silicate is increased by 24 percent, and the mixture is mixedThe mass of the gelled substance generated by the complete hydration of the mixture curing agent is increased by 43-85%, in addition, the silicate hydration can generate volume shrinkage, the hydration reaction for generating the ettringite can generate volume expansion, and the expansion rate is about 120%, therefore, the mixture curing agent, namely the curing material taking the ettringite as a main hydration product, can be presumed to have the capacity-increasing ratio of the gelled substance far larger than that of silicate cement, and the ettringite cementing material has the volume 2-4 times larger than that of the silicate cementing material under the same mass.

AlO₂ ^-The ions mainly consist of Al₂O₃The industrial waste slag contains Al, such as Portland cement, sulphoaluminate cement, aluminate, fly ash, blast furnace slag powder and the like₂O₃Component (B), but Al contained in aluminate cement₂O₃The components are the most, the activity is the highest, and the finally generated ettringite is the most and fastest, so the aluminate cement is selected as Al₂O₃Ingredient source, Al of aluminate cement₂O₃The content of the components is generally 50-60%.

1) The aluminate cement generates calcium aluminate through hydration reaction with free water in the slurry, the hydration reaction is very fast, the reaction degree is over 80 percent at 1d generally, and the aluminate cement is the basis for fast curing of the slurry;

2) the quicklime is an additional CaO source required for converting the calcium aluminate into the ettringite, and the quicklime and the aluminate are mixed for use and are easy to instantly coagulate, so the quicklime and the slurry are mixed and dispersed in advance, and the instant coagulation of the aluminate cement is inhibited;

3) the desulfurized gypsum is a large amount of calcium sulfate source required for converting calcium aluminate into ettringite and is a main source for strength development of the solidified soil, because the gypsum accounts for a large proportion in the solidified agent, if the dried gypsum is adopted, the material cost of the solidified agent can be improved by 33%, but the solidified effect is not obviously improved (the introduced water amount of the dried gypsum is less than that of the wet gypsum, but the difference of the introduced water amount is negligible relative to the own water amount of the slurry), and in view of cost, the wet desulfurized gypsum is recommended to be adopted and is premixed into the slurry, and if the dried gypsum is selected, the slurry can be premixed or is uniformly mixed with aluminate;

4) the main component of the sodium bentonite is montmorillonite which has high water absorption, good dispersibility, good adsorptivity and cation exchange capacity, can adsorb aluminate cement particles, compete with the aluminate cement particles for water absorption, inhibit hydration reaction of the aluminate cement particles in the early stage, prevent instant coagulation generated by contact of the aluminate cement and lime in slurry, and improve the dispersibility of the aluminate cement particles.

5) The water content of the slurry in the prior engineering is greatly changed, the water content of the slurry generated by inorganic soil is generally 50-200%, the water content of the slurry generated by organic soil, such as river silt, lake silt and the like, is generally 80-400%, and the sludge of a sewage treatment plant, the sludge of a garbage leachate tank and the like belong to peat soil or peat, the organic content is high, and the water content of the slurry generated by the sludge treatment plant is generally over 400% and even reaches 1000%. When the curing agent is used for curing slurry with different water contents, the mixing amount of the curing agent is generally related to the water content, the higher the water content is, the higher the mixing amount of the curing agent is required to be, the higher the curing strength is required to be, the higher the mixing amount of the curing agent is, in addition, organic matters of the slurry can strongly inhibit the hydration reaction of a curing agent material, the higher the organic matter content is, the slower the hydration is, the lower the strength after curing is, the curing agent is a material which is less influenced by organic matters, and the mixing amount range of the curing agent is generally 2.5-30%;

6) the slurry is mixed with calcium lime and desulfurized gypsum in proportion to create uniform Ca for aluminate before adding slurry into aluminate cement²、OH^-、SO₄ ^2-After the aluminate is added into the slurry, the calcium aluminate which is just generated by the reaction is quickly converted into needle-shaped ettringite and covers the surface of aluminate cement particles, so that the calcium aluminate is prevented from being hydrated too violently to generate instant coagulation; the bentonite and the aluminate cement are required to be mixed uniformly in advance to ensure that the aluminate waterThe bentonite particles are separated by the bentonite particles as much as possible, the bentonite particles are used as a waterproof agent, the hydration reaction caused by the early contact of moisture and the cement particles is prevented, the storage time of the cement is prolonged, the early hydration reaction of the aluminate cement is delayed, the dispersion effect of the cement particles in the slurry is improved, and the coagulation of the cement particles in the slurry stirring process is prevented to influence the solidification effect.

The invention has the following advantages: the invention prepares a curing material which can react with water rapidly and improve the strength of the mud curing soil obviously by compounding the high water absorption material and the inorganic hydraulic material, thereby greatly improving the construction efficiency and simplifying the construction process, and the mud curing soil can be used for building construction roads.

Drawings

The invention will be further described with reference to the following examples with reference to the accompanying drawings.

FIG. 1 shows the effect of mass ratio of different bentonites to aluminate cement on the strength of the cured soil.

Detailed Description

Example one

The piling mud for the Jia Li Cinnamomum kanehirae project in Fuzhou has the water content of 89 percent and the organic matter content of 2 percent.

Weighing 16 parts of aluminate cement, 16 parts of bentonite, 13 parts of quicklime, 55 parts of desulfurized gypsum with the water content of 15 percent, and 4.5 percent of curing material mixing amount, wherein the quicklime and the desulfurized gypsum are uniformly mixed with slurry, the aluminate cement and the bentonite are uniformly mixed in advance, the slurry is finally added and uniformly mixed, casting molding (1# cured soil) is performed after uniform mixing, the bentonite component in the slurry curing agent is removed by taking the cured soil obtained by curing the P.O.425 portland cement (2# cured soil) and the CA50-I (3# cured soil) with the same mixing amount as a comparison sample, the proportion of other three materials is unchanged, the feeding sequence is unchanged, a slurry curing agent comparison sample (4# cured soil) is prepared, and the slurry is cured with the same mixing amount. Under the same mixing amount, the strength of the No. 1 solidified soil 28d is more than twice that of the No. 2 solidified soil, the strength of the No. 1 solidified soil 1d reaches about 80% of the strength of the No. 28d, the strength development is much faster than that of the No. 2 solidified soil, and the rapid construction and rapid use method has the advantages of rapid construction and rapid use; the initial setting time of the No. 1 solidified soil is equivalent to that of the No. 3 solidified soil, the strength development speed is high, but the strength of the No. 1 solidified soil is obviously higher than that of the No. 3 solidified soil; the strength of the No. 4 solidified soil is higher than that of the No. 1 solidified soil, but the initial setting time is only 5min, the quick forming can be realized only in a laboratory, and the operable time requirement (not less than 30min) of a construction site can not be met; when the quicklime, the aluminate cement and the bentonite are uniformly mixed in advance and then mixed with the gypsum slurry mixture, the solidified material is seriously agglomerated and is difficult to uniformly mix, the material uniformity is poor, and the forming is difficult.

TABLE 1 comparison of properties of mud-cured soils

For the No. 1 curing soil formula, the mixing amount of the curing agent is kept unchanged, the mass ratio of the aluminate cement, the desulfurized gypsum and the quicklime is kept unchanged, only the mass ratio of the bentonite to the aluminate cement is adjusted, as shown in figure 1, along with the increase of the mass ratio of the bentonite to the aluminate cement, the initial setting time of the curing soil is prolonged, the unconfined compressive strength of 1d is reduced, based on the field construction consideration, the initial setting time of the curing soil is not less than 30min, and the factor of the strength of the curing soil is considered, and the mass ratio of the bentonite to the aluminate cement is generally in the range of 1-2.

Example two

The sludge in the straight river channel is taken from a new house in Fuzhou city, the water content is 196 percent, and the organic matter content is 15 percent.

Weighing 17 parts of aluminate cement, 17 parts of bentonite, 14 parts of quicklime, 52 parts of desulfurized gypsum with the water content of 12%, and 10% of a curing material, wherein the quicklime and the desulfurized gypsum are uniformly mixed with slurry firstly, the aluminate cement and the bentonite are uniformly mixed in advance, then the slurry is added for uniform mixing, casting and molding are carried out after uniform mixing (1# cured soil), and the cured soil obtained by curing the P.O.425 silicate cement (2# cured soil) with the same mixing amount is used as a comparison sample. The initial setting time of the No. 1 solidified soil is 32min, the 1d strength reaches 0.52MPa, and is much higher than that of the No. 2 solidified soil under the same mixing amount.

TABLE 2 comparison of properties of the slurry in the soil

Solidified soil

Curing material

Initial setting time

1d

7d

28d

1#

Slurry curing agent

32min

0.52

0.63

2#

Portland cement P.O.425

5h

<0.1

0.13

0.22

3#

Aluminate cement CA50-I

25min

0.31

0.35

0.36

EXAMPLE III

The water content of the refuse leachate bottom mud of Fuzhou Hongmiao ridge is 900 percent.

Weighing 16 parts of aluminate cement, 16 parts of bentonite, 17 parts of quicklime, 51 parts of desulfurized gypsum with the water content of 10%, and 30% of a curing material, wherein the quicklime and the desulfurized gypsum are uniformly mixed with slurry firstly, the aluminate cement and the bentonite are uniformly mixed in advance, then the slurry is added for uniform mixing, casting and molding are carried out after uniform mixing (1# cured soil), and the cured soil obtained by curing the P.O.425 silicate cement (2# cured soil) with the same mixing amount is used as a comparison sample. The initial setting time of the No. 1 solidified soil is 40min, the 1d strength reaches 0.57MPa, and is much higher than that of the No. 2 solidified soil under the same mixing amount.

TABLE 3 comparison of properties of mud-cured soils

Solidified soil

Curing material

Initial setting time

1d

7d

28d

1#

Slurry curing agent

40min

0.57

0.65

0.72

2#

Portland cement P.O.425

4d

<0.1

0.13

3#

Aluminate cement CA50-I

21min

0.38

0.48

0.51

Although specific embodiments of the invention have been described above, it will be understood by those skilled in the art that the specific embodiments described are illustrative only and are not limiting upon the scope of the invention, and that equivalent modifications and variations can be made by those skilled in the art without departing from the spirit of the invention, which is to be limited only by the appended claims.

Claims

1. A slurry curing agent characterized by: the composition comprises the following components in parts by weight: 15-20 parts of aluminate cement, 13-19 parts of quicklime, 14-28 parts of bentonite and 47-54 parts of desulfurized gypsum.

2. The mud curing agent of claim 1, wherein: the aluminate cement is a commercially available product which meets the requirements of aluminate cement GB/T201-2015.

3. The mud curing agent of claim 1, wherein: the quicklime is calcareous lime which accords with 'building quicklime' JC/T479-2013.

4. The mud curing agent of claim 1, wherein: the bentonite is sodium bentonite which accords with bentonite GB/T20973-2007.

5. The mud curing agent of claim 1, wherein: the desulfurized gypsum is the desulfurized gypsum which accords with the flue gas desulfurized gypsum GB/T37785-2019, or semi-hydrated gypsum or anhydrous gypsum which is produced by taking the desulfurized gypsum as a raw material and calcining.

6. The mud curing agent of claim 1, wherein: the mass ratio of the bentonite to the aluminate cement is 1-2: 1.

7. use of a mud curing agent according to any one of claims 1 to 6 for curing waste mud, wherein: and (2) mixing the slurry curing agent into the waste slurry according to 2.5-30% of the mass of the waste slurry, and uniformly stirring the slurry curing agent and the waste slurry, wherein the water content of the waste slurry is 50-1000%.

8. Use according to claim 7, characterized in that: the mud curing agent is mixed into the waste mud according to the following steps:

(1) uniformly mixing the waste slurry with quicklime and desulfurized gypsum according to a proportion to obtain a mixture 1;

(2) uniformly mixing bentonite and aluminate cement in proportion to obtain a mixture 2;

(3) and uniformly mixing the mixture 1 and the mixture 2.

9. Use according to claim 8, characterized in that: and (4) spreading the uniformly mixed mixture obtained in the step (3) on a construction site required area, and using the uniformly mixed mixture as a construction pavement base layer or surface layer after 1-3 days.