CN107814515B - Premixed mortar prepared from high-volume furnace bottom slag and preparation method thereof - Google Patents

Abstract

The invention belongs to the technical field of ready-mixed mortar, in particular to ready-mixed mortar prepared by using large-mixing amount of furnace bottom slag and a preparation method thereof; the ready-mixed mortar comprises the following components in parts by mass: 100 portions of cement, 10 to 20 portions of thickening powder, 60 to 80 portions of fly ash, 648 portions of sand, 111 portions of bottom slag, and 0.111 to 0.33 portion of water reducing agent; the invention uses the furnace bottom slag generated by the coal-fired power plant as the aggregate to partially replace the sand in the ready-mixed mortar, on one hand, a new way can be provided for the resource utilization of the furnace bottom slag, the use of natural resources is reduced, the development of the comprehensive utilization work of resources is facilitated, on the other hand, the use of the furnace bottom slag is beneficial to the reduction of the cost of the mortar, and meanwhile, the furnace bottom slag is used as a light aggregate, and the large amount of the furnace bottom slag doped in the mortar can certainly improve the performances of the mortar such as heat preservation and the like, and provides national raw materials for the development of the inorganic light.

Description

Premixed mortar prepared from high-volume furnace bottom slag and preparation method thereof

Technical Field

The invention belongs to the technical field of ready-mixed mortar, and particularly relates to ready-mixed mortar prepared by using large-mixing amount of furnace bottom slag and a preparation method thereof.

Background

The furnace bottom slag and the fly ash are main solid coal-fired wastes, wherein the furnace bottom slag is ash slag with coarse particle size discharged from the bottom of a boiler after coal is combusted, generally accounts for about 20% of the total amount of the coal-fired wastes, and the daily yield of each large power plant and thermal power plant is quite large. During the 'twelve-five' period, the production of bottom slag exceeds 400 ten thousand tons. Due to the difference of the discharge mode, the morphology and the appearance, the resource utilization of the bottom slag always lags behind the comprehensive utilization of the fly ash.

At present, three utilization ways are mainly used for recycling furnace bottom slag: firstly, the cement is used as a cement mixture and is ground together with clinker, gypsum and other mixed materials to prepare cement; secondly, the aggregate is used for producing ash bricks, concrete blocks and the like; and thirdly, the material is used as a filling material for engineering application such as road construction. For the first utilization approach, because of a large variety of wastes which can be used as mixing materials in cement and large influence of furnace bottom slag on performances such as water consumption of cement, only a small proportion of furnace bottom slag can be mixed in the cement; the furnace bottom slag is used as aggregate for producing wall materials, so that the product cost can be reduced. However, the characteristics of the hearth slag particles in the combustion process are difficult to maintain stably, and enterprises have no corresponding countermeasures in the production process, so that the product quality is unstable. In addition, compared with quartz sand, the water absorption rate is very high, and the performance such as the integral strength of the material is inevitably influenced by the large amount of the quartz sand; the third utilization mode is a main utilization way of the bottom slag for a long time, is the utilization mode of the lowest end of the bottom slag, and cannot fully exert the physicochemical characteristics of the bottom slag. It can be seen that the utilization mode hardly ensures that the bottom slag can be completely and efficiently utilized, and a more effective utilization way needs to be expanded, which is also an important guarantee for realizing the sustainable high-level development of the domestic coal ash comprehensive utilization work.

The use of ready-mixed mortar in building construction originated in europe at the end of the 19 th century and developed rapidly in europe 30 years after the second war. At present, the application of the ready-mixed mortar in building construction is very popular in industrial developed countries and regions such as Germany, France, Italy, Austria, America, Singapore, Korea, hong Kong and the like, a series of relevant standards and specifications from production, transportation, construction to inspection and the like are formed, more than 200 ready-mixed mortar varieties with different purposes exist, and the requirements of modern buildings on different building functions such as heat preservation, heat insulation, water resistance, color and the like are met.

Since the 21 st century, with the rapid development of the construction industry in China and the advancement of social civilization, the requirements of people on the aspects of construction quality, construction function, appearance color, environmental protection, labor protection and the like are continuously improved, and the development of the ready-mixed mortar production and related industries in China is effectively promoted. Meanwhile, with the popularization and application of novel wall materials in China, higher requirements are also put forward on the quality and performance of building mortar products.

Compared with the traditional building mortar, the ready-mixed mortar as a novel building material has the advantages of stable quality, various varieties, rich colors, convenient use, material and labor saving, environmental protection and the like. The premixed mortar is used for replacing the field stirring mortar, is not simply a homogeneous product replacement, but is a higher-level product replacement with increased technical content and improved product performance, and is a novel and advanced building material for replacing the traditional and laggard building material. The popularization and the use of the ready-mixed mortar have important significance for improving the building quality, developing green building materials, strengthening the building energy conservation and shortening the building period.

Disclosure of Invention

The purpose of the invention is: provides the premixed mortar prepared by using the furnace bottom slag with large mixing amount and the preparation method thereof, which are green and environment-friendly and have good construction performance.

The technical scheme adopted by the invention is as follows:

the premixed mortar prepared by using the furnace bottom slag with large mixing amount comprises the following components in parts by mass: 100 portions of cement, 10 to 20 portions of thickening powder, 60 to 80 portions of fly ash, 324 portions of sand, 330 portions of bottom slag and 0.111 to 0.33 portion of water reducing agent.

Preferably, the water reducing agent is at least one of polycarboxylic acid, sodium dodecyl sulfate and naphthalene water reducing agent.

Preferably, the water reducing agent is polycarboxylic acid.

Preferably, the grain size of the bottom slag is less than 0.63 mm.

Preferably, the furnace bottom slag is pretreated furnace bottom slag, and the pretreated furnace bottom slag is obtained by soaking through a surfactant and a coupling agent.

Preferably, the surfactant is selected from fatty alcohol sulfate anions.

Preferably, the ready-mixed mortar comprises the following components in parts by mass: 105 parts of cement, 15 parts of thickening powder, 70 parts of fly ash, 486 parts of sand, 222 parts of furnace bottom slag and 0.222 part of water reducing agent.

A method for preparing ready-mixed mortar prepared by using large-amount furnace bottom slag is characterized by comprising the following steps:

(1) drying the furnace bottom slag until the water content is lower than 0.2%, sieving to remove large particles of more than 0.63mm, soaking the furnace bottom slag by using a surfactant and a coupling agent to obtain activated furnace bottom slag, and feeding the activated furnace bottom slag into a sand silo for later use;

(2) the selected raw materials are measured according to the mass ratio and fully mixed in a mixing device for 8-10min for standby.

The technical scheme adopted by the invention has the beneficial effects that:

the invention uses the furnace bottom slag generated by the coal-fired power plant as the aggregate to partially replace the sand in the ready-mixed mortar, on one hand, a new way can be provided for the resource utilization of the furnace bottom slag, the use of natural resources is reduced, the development of the comprehensive utilization work of resources is facilitated, on the other hand, the use of the furnace bottom slag is beneficial to the reduction of the cost of the mortar, and meanwhile, the furnace bottom slag is used as a light aggregate, and the large amount of the furnace bottom slag doped in the mortar can certainly improve the performances of the mortar such as heat preservation and the like, and provides national raw materials for the development of the inorganic light.

In the invention, furnace bottom slag is used for replacing part of sand in the ready-mixed mortar, when the fatty alcohol sulfate anionic surfactant and the water reducing agent are used in a composite way, the indexes of the mortar such as consistency, water retention rate, linear shrinkage rate and the like can meet the use requirements, and the workability and the cracking resistance of the mortar are better.

In the invention, the premixed mortar is prepared by replacing partial river sand with the furnace bottom slag, and the mechanical property of the premixed mortar can meet the use requirement by properly adjusting the formula.

Drawings

FIG. 1 is a schematic diagram showing water absorption of bottom slag with different particle sizes.

Detailed Description

The invention is further illustrated by the following specific examples.

Example 1

The premixed mortar prepared by using the furnace bottom slag with large mixing amount comprises the following components in parts by mass: 100 parts of cement, 10 parts of thickening powder, 60 parts of fly ash, 648 parts of sand, 111 parts of furnace bottom slag and 0.111 part of water reducing agent.

Wherein, the water reducing agent is selected from polycarboxylic acid.

Wherein the grain diameter of the furnace bottom slag is less than 0.63 mm.

Wherein, the furnace bottom slag adopts pretreated furnace bottom slag, and the pretreated furnace bottom slag is obtained by soaking a surfactant and a coupling agent.

Wherein the surfactant is fatty alcohol sulfate anion.

Example 2

The premixed mortar prepared by using the furnace bottom slag with large mixing amount comprises the following components in parts by mass: 105 parts of cement, 15 parts of thickening powder, 70 parts of fly ash, 486 parts of sand, 222 parts of furnace bottom slag and 0.222 part of water reducing agent.

Wherein, the water reducing agent is selected from polycarboxylic acid.

Wherein the grain diameter of the furnace bottom slag is less than 0.63 mm.

Wherein, the furnace bottom slag adopts pretreated furnace bottom slag, and the pretreated furnace bottom slag is obtained by soaking a surfactant and a coupling agent.

Wherein the surfactant is fatty alcohol sulfate anion.

Example 3

The premixed mortar prepared by using the furnace bottom slag with large mixing amount comprises the following components in parts by mass: 110 parts of cement, 20 parts of thickening powder, 80 parts of fly ash, 324 parts of sand, 330 parts of furnace bottom slag and 0.111 part of water reducing agent.

Wherein, the water reducing agent is selected from polycarboxylic acid.

Wherein the grain diameter of the furnace bottom slag is less than 0.63 mm.

The furnace bottom slag is pretreated furnace bottom slag, and the pretreated furnace bottom slag is obtained by soaking a surfactant and a coupling agent.

Wherein the surfactant is fatty alcohol sulfate anion.

Control test

Study on mortar mix proportion

From the economical consideration, the mixing amount of the furnace bottom slag can be as high as possible on the premise of meeting the construction performance, the working performance and the durability of the mortar. Because the bottom slag is light aggregate, the experiment adopts a volume substitution method. According to the measurement, the rho sand to the rho slag = 1.46. Mortar experimental formulation table 1.

TABLE 1 mortar mix design

The consistency, 2h consistency loss, water retention and compressive strength of the above formulated mortar were determined as shown in table 2.

TABLE 2 mortar Properties

As can be seen from Table 2, the mortar was able to reach a greater consistency with a corresponding increase in the water addition and the addition of the polycarboxylate water reducer, and its loss of consistency after 2h was somewhat reduced. The consistency loss of the mortar is continuously reduced along with the increase of the doping amount of the furnace bottom slag. When the bottom slag exceeds 40%, the consistency loss is substantially the same as the blank. This is because, in the case of low-dosage slag, the absolute dosage of the water-reducing agent is also low, and the water-reducing and thickening-keeping effects cannot be effectively achieved. However, with the increase of the mixing amount of the furnace bottom slag, the absolute addition amount of the water reducing agent is correspondingly increased, the ion concentration in the liquid phase is increased, and similar ion membranes can be fully formed on the surfaces of the sand and the cementing material while the same ion hydrophobic membrane is formed on the surface of the furnace bottom slag, so that the whole mortar system has better repulsion between particles, and further obtains larger fluidity, and correspondingly, the consistency loss can be reduced to a certain extent.

The test shows that the water retention rate of the mortar reaches over 95 percent and completely meets the standard requirement. However, as the amount of slag added to the furnace bottom increases, the water retention tends to decrease. This is because the specific surface area of the bottom slag is large although the bottom slag is obtained as sand of the same volume, and the bottom slag adsorbs an additive such as thickening powder correspondingly more. The thickening powder remains fixed in all the proportions, so the water retention effect is correspondingly weakened.

The compressive strength of the mortar tends to be gradually reduced along with the increase of the mixing amount of the furnace bottom slag. When the doping amount of the furnace bottom slag is below 40 percent, the compressive strength of the mortar is not changed greatly, and is about 6MPa, so that the requirement of the mortar can be basically met. However, the compressive strength of the mortar is reduced sharply with the continuous increase of the mixing amount of the furnace bottom slag, and when the mixing amount reaches 60%, the compressive strength is only 3.2 MPa. This is mainly because when the amount of the added bottom slag is relatively low, the main aggregate in the mortar is still natural quartz sand, and although the strength of the bottom slag is lower than that of the quartz sand, the main aggregate has little influence on the compressive strength of the mortar. In addition, because the water reducing agent is added and the furnace bottom slag can quickly absorb moisture in the early stage of hydration, the mortar is relatively compact, the porosity is low, and the adverse effect of the self strength of the furnace bottom slag on the strength of the mortar can be reduced. However, when the mixing amount of the furnace bottom slag reaches a certain degree, due to the porous shape of the furnace bottom slag, part of gelled slurry can be filled into the pores, so that the gelled materials in the mortar are relatively reduced, the coating and the combination of the gelled materials on the aggregates are weakened, the strength is continuously reduced, and when the bonding among the aggregates is reduced to a certain degree, the strength of the mortar is rapidly reduced. If the aim of increasing the amount of the slag at the bottom of the furnace is to increase the amount of the cementing materials correspondingly, the cementing materials are enough to bond the aggregates. Therefore, on the basis of the mixture ratio, the cement dosage is correspondingly increased along with the increase of the doping amount of the furnace bottom slag, as shown in the table 3.

TABLE 3 mortar mix design

TABLE 4 mortar Properties

It can be seen that the strength of the mortar is improved to some extent with the increase of the cement amount. However, the addition amount of the cement is increased, so that the strength of the mortar does not completely meet the design requirement. However, if the water consumption of the mortar is greatly increased by only increasing the cement mixing amount, the possibility of shrinkage and cracking of the mortar is increased. Therefore, the shrinkage and crack resistance of the mortar need to be studied and examined.

The cracking problem of mortar is mainly caused by two aspects, and the like. On one hand, the mortar is in early hydration stage, due to poor water retention, environment and other reasons, the mortar is rapidly dehydrated, a cementing material in the mortar is not hydrated in time, and the mortar has low strength, so that cracking is easy to occur; on the other hand, the hydration volume of the cementing material in the mortar shrinks to generate internal stress, and when the shrinkage stress of the mortar is larger than the tensile stress of the mortar, the mortar is easy to crack. At present, there are various methods for the characterization and detection of the tensile property of the mortar around the above cracking mechanism, including the detection of the drying shrinkage property of the mortar and the simulation of the cracking property under extreme conditions, etc., as shown in table 5.

TABLE 5 mortar drying shrinkage Properties

It can be seen that when the mixing amount of the furnace bottom slag is low, the shrinkage of the mortar is relatively small, and even is reduced compared with the blank sample. This is mainly because the amount of water added is mostly absorbed by the bottom slag due to the increased amount of slag, and the water content in the slurry is relatively small, and therefore the drying shrinkage is not large. However, as the amount of cement added increases, the shrinkage of the mortar becomes greater. However, the shrinkage still meets the requirement that the mortar standard is not more than 0.2 percent. The shrinkage rate test is also only a representation of the self-drying shrinkage performance of the mortar under natural curing conditions, and the mortar, particularly the plastering mortar, can be subjected to relatively extreme weather conditions such as high temperature, strong wind and the like after construction. Under such weather conditions, the mortar may undergo rapid dehydration and drying shrinkage, and cracking may occur.

In order to further research the crack resistance of the mortar, the JC/T951-2005 test method is adopted to characterize and compare the crack resistance of different mortars. The bottom of the experimental template is lined with a layer of polyvinyl chloride plastic film to reduce the influence of the bottom die on the shrinkage deformation of the test piece. And a circle of iron nails are nailed around the wood mould and used for limiting free shrinkage deformation of the mortar. Immediately blowing the test piece by using an electric fan after the test piece is formed, wherein the wind speed is 1-2 m/s; meanwhile, a 1000w iodine tungsten lamp about 1.5m above the test piece is turned on to bake the test piece, and the surface temperature of the test piece is kept at about 40 ℃, as shown in the figure. And turning off the lamp after 4 hours of illumination, turning off the electric fan after 24 hours of wind blowing, and measuring the width and the corresponding length of the crack on the surface of the test piece, thereby evaluating the crack resistance of the mortar.

It can be seen that when the mixing amount of the furnace bottom slag is low, the shrinkage of the mortar is relatively small, and even is reduced compared with the blank sample. This is mainly because the amount of water added is mostly absorbed by the bottom slag due to the increased amount of slag, and the water content in the slurry is relatively small, and therefore the drying shrinkage is not large. However, as the amount of cement added increases, the shrinkage of the mortar becomes greater. However, the shrinkage still meets the requirement that the mortar standard is not more than 0.2 percent. The shrinkage rate test is also only a representation of the self-drying shrinkage performance of the mortar under natural curing conditions, and the mortar, particularly the plastering mortar, can be subjected to relatively extreme weather conditions such as high temperature, strong wind and the like after construction. Under such weather conditions, the mortar may undergo rapid dehydration and drying shrinkage, and cracking may occur.

In order to further research the crack resistance of the mortar, the JC/T951-2005 test method is adopted to characterize and compare the crack resistance of different mortars. The bottom of the experimental template is lined with a layer of polyvinyl chloride plastic film to reduce the influence of the bottom die on the shrinkage deformation of the test piece. And a circle of iron nails are nailed around the wood mould and used for limiting free shrinkage deformation of the mortar. Immediately blowing the test piece by using an electric fan after the test piece is formed, wherein the wind speed is 1-2 m/s; and simultaneously, a 1000w iodine tungsten lamp which is about 1.5m above the test piece is started to bake the test piece, and the surface temperature of the test piece is kept at about 40 ℃. The light is turned off after 4 hours of illumination, the electric fan is turned off after 24 hours of blowing, the width and the corresponding length of the crack on the surface of the test piece are measured, and the crack resistance of the mortar is evaluated according to the width and the corresponding length, which are shown in Table 6.

TABLE 6 mortar crack resistance

In order to further understand the water absorption performance of the furnace bottom slag particles, the furnace bottom slag is sieved to obtain the furnace bottom slag particles with a plurality of granularity intervals, such as more than 5mm, 2.5 mm-5 mm, 1.25 mm-2.5 mm, 0.63 mm-1.25 mm, 0.315 mm-0.63 mm, 0.16 mm-0.315 mm, less than 0.16mm and the like, and the water absorption rate of the furnace bottom slag particles is tested for 2 hours, and the result is shown in figure 1.

As can be seen from FIG. 1, the furnace bottom slag water absorption rate of different particle sizes is greatly different, the larger the particle size is, the lower the water absorption rate is, the water absorption rate of the furnace bottom slag larger than 5mm is less than 2%, and the water absorption rate of the particles smaller than 0.63mm is between 8% and 10%. The large particles have relatively smooth surfaces, less open pores and large pores, and can be rapidly filled with water when immersed in water, so that the subsequent water absorption amount is less. And for fine particles, the pore diameter of the pores is small, the water permeation resistance is large, and the water absorption is slow, so that the finally measured water absorption rate is large. The difference of the water absorption rate and the water absorption rate of the particles with different sizes can provide certain guidance for the pretreatment process of the furnace bottom slag, such as crushing, screening, grading and the like.

TABLE 7 Effect of Water reducing Agents on mortar consistency Performance

It can be seen that the polycarboxylate superplasticizer has a good effect on reducing the consistency loss rate, and the addition of the sodium dodecyl sulfate can increase the initial consistency of the mortar, but the consistency loss rate is also increased, so that the standard requirement cannot be met. When the doping amount of the polycarboxylic acid is increased to 5 per mill of the quality of the furnace bottom slag, the mortar can obtain higher consistency, the loss rate of the consistency within 2 hours is only 19.2 percent, and the standard requirement of the mortar can be completely met. Although polycarboxylic acid is also an anionic surfactant, the polycarboxylic acid has the action of making the cement particles, the hearth slag particles and the like directionally adsorbed and arranged on the surfaces of the cement particles, the hearth slag particles and the like, so that the cement particles, the hearth slag particles and the like are mutually exclusive, and the polycarboxylic acid has a good effect of increasing the fluidity. The action mechanism of the sodium dodecyl sulfate is mainly a ball effect, so that the initial consistency can be very large, but due to the stability of bubbles and other reasons, the bubbles are broken in a short time, the ball effect is reduced, and a certain amount of water is absorbed by the bottom slag, so that the consistency of the mortar is greatly changed.

In light of the foregoing description of the preferred embodiment of the present invention, many modifications and variations will be apparent to those skilled in the art without departing from the spirit and scope of the invention. The technical scope of the present invention is not limited to the content of the specification, and must be determined according to the scope of the claims.

Claims (3)

1. The ready-mixed mortar prepared by using the large-mixing-amount furnace bottom slag is characterized by comprising the following components in parts by mass: 100 portions of cement, 10 to 20 portions of thickening powder, 60 to 80 portions of fly ash, 648 portions of sand, 111 portions of bottom slag, and 0.111 to 0.33 portion of water reducing agent;

the water reducing agent is a polycarboxylic acid water reducing agent,

the furnace bottom slag adopts pretreated furnace bottom slag, the pretreated furnace bottom slag is obtained by soaking through a surfactant and a coupling agent, the surfactant is a fatty alcohol sulfate anionic surfactant,

the grain diameter of the furnace bottom slag is less than 0.63 mm.

2. The ready-mixed mortar prepared by using the furnace bottom slag with large mixing amount according to claim 1, which is characterized by comprising the following components in parts by mass: 105 parts of cement, 15 parts of thickening powder, 70 parts of fly ash, 486 parts of sand, 222 parts of furnace bottom slag and 0.222 part of water reducing agent.

3. A method for preparing ready-mixed mortar prepared by using high-content hearth slag according to any one of claims 1 to 2, which comprises the following steps:

(1) drying the furnace bottom slag until the water content is lower than 0.2%, sieving to remove large particles of more than 0.63mm, soaking the furnace bottom slag by using a surfactant and a coupling agent to obtain activated furnace bottom slag, and feeding the activated furnace bottom slag into a sand silo for later use;

(2) the selected raw materials are measured according to the mass ratio and fully mixed in a mixing device for 8-10min for standby.

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