CN110655364A - A kind of concrete containing pyrolyzed sludge and preparation method thereof - Google Patents

Abstract

The invention discloses a concrete containing pyrolyzed sludge and a preparation method thereof. The concrete containing pyrolyzed sludge comprises the following raw materials: composite cement, fine aggregate, coarse aggregate and water; wherein, the composite Cement contains cement and sludge pyrolysates. The concrete containing pyrolyzed sludge obtained by the invention can handle a large amount of sludge, is economical and environmentally friendly, and its hardness, tensile strength, splitting strength and compressive strength can reach or exceed national standards, and have lower density and weight than ordinary concrete. It has the characteristics of light weight, high water permeability and strong toughness; the preparation method is simple, the production cost is low, and the obtained concrete can handle a large amount of municipal, river, lake and industrial sludge.

Description

A kind of concrete containing pyrolyzed sludge and preparation method thereof

technical field

The invention relates to the technical field of ecological environment protection, in particular to a concrete containing pyrolyzed sludge and a preparation method thereof.

Background technique

Sludge is usually the largest residue produced in the sewage treatment process. According to different sources, it can be divided into river and lake sludge, municipal sludge, and industrial sludge. Sludge from rivers and lakes mainly comes from rivers and lakes, and contains less pollutants. Industrial sludge after sewage treatment and some sludge from special places contain toxic and harmful substances, such as pathogens, heavy metals, chemicals and organic pollutants. Improper disposal will cause secondary pollution, affect the ecological environment, and endanger human health. Therefore, it is regarded as hazardous waste and should be disposed of in accordance with the principles of reduction, recycling and harmlessness. The main methods of sludge disposal in EU countries and the United States are agricultural application, land restoration, landfill and incineration. With the development of industrialization and urbanization in China, a large amount of sludge has been generated along with the treatment of a large amount of sewage. According to relevant information, China's daily sludge output is more than 25 million tons, but the sludge treatment and recovery rate in my country is only 25%, and sludge treatment has become a long-standing problem.

At present, sludge treatment in my country includes sanitary landfill, incineration, agricultural use and building materials and other sludge treatment methods, and corresponding applications have been carried out in my country, but sanitary landfill covers a large area and is difficult to sustain for a long time; incineration, due to The sludge has low water content and low calorific value, requires a large amount of combustion-supporting materials, and has high costs. For the treatment of sludge for agricultural purposes, there are direct application of sludge to the field, and after the sludge is pyrolyzed to eliminate pathogenic bacteria, the ash material containing organic matter is generated and used in the farmland. Factors such as limiting the use of a large number of. As a building material, sludge contains a high amount of organic matter, and the decomposition of the organic matter will lead to a decrease in the quality of the building. In recent years, with the construction of the ecological environment and the strict requirements of laws and regulations, it is urgent to find a clean and efficient sludge treatment method that can be used in large quantities, has low cost, has no side effects, and is clean and efficient.

SUMMARY OF THE INVENTION

In view of the problems existing in the prior art, the purpose of the present invention is to provide a concrete containing pyrolyzed sludge and a preparation method thereof, the concrete containing pyrolysed sludge can handle a large amount of sludge, is economical and environmentally friendly, and The hardness, tensile strength, splitting strength and compressive strength can reach or exceed the national standards. Compared with ordinary concrete, it has the characteristics of low density, light weight, high water permeability and strong toughness; the preparation method is simple, the production cost is low, and the obtained concrete It can handle a large amount of municipal, river, lake and industrial sludge.

In order to achieve the above objects, the present invention adopts the following technical solutions to achieve.

(1) A concrete containing pyrolyzed sludge, comprising the following raw materials: composite cement, fine aggregate, coarse aggregate and water; wherein the composite cement comprises cement and pyrolysed sludge.

Preferably, the cement is Portland cement.

Preferably, the fine aggregate is sand.

Preferably, the coarse aggregate is crushed stone, and the particle size of the crushed stone is 5-20 mm.

Preferably, the mass ratio of the composite cement, sand, gravel and water is: 1:(1-2):(2.5-3.6):(0.3-0.6); 0.01-30% of the quality of the composite cement.

Further preferably, the mass ratio of the composite cement, sand, gravel and water is: 1: (1.35-1.98): (2.74-3.44): (0.45-0.55); 0.01-10% of the mass of the composite cement.

(2) a kind of preparation method of the concrete containing sludge pyrolysis product, may further comprise the steps:

Step 1, prepare sludge pyrolysate, for use;

Step 2, mixing the pyrolyzed sludge with cement uniformly, adding fine aggregates, coarse aggregates and water, and stirring uniformly at room temperature to obtain concrete containing pyrolysed sludge.

Preferably, in step 1, the preparation method of the sludge pyrolysate includes the following sub-steps:

The sludge is placed in the integrated sludge continuous carbonization equipment, dry heat pyrolyzed under anaerobic conditions, pulverized and sieved to obtain the sludge pyrolyzed product.

Further preferably, the moisture content of the sludge is less than 80%.

Further preferably, the temperature of the dry heat pyrolysis is 300-900° C., and the time of the dry heat pyrolysis is 0.5-1.5 hours.

Further preferably, the sieving is to pass through a 300-mesh sieve.

Preferably, in step 2, the stirring time is 60-90 seconds.

Compared with the prior art, the beneficial effects of the present invention are:

(1) The concrete containing pyrolyzed sludge obtained by the present invention can handle a large amount of sludge, is economical and environmentally friendly, and the hardness, tensile strength, splitting strength and compressive strength of the concrete can reach or exceed the national standard, compared with ordinary Concrete has the characteristics of low density, light weight, high water permeability and strong toughness.

(2) In the preparation method of concrete containing sludge pyrolysis product, after the sludge is treated by anaerobic pyrolysis at 300-900°C, the fine particulate matter formed, namely the sludge pyrolysis product, contains a variety of cement-like components. Substances such as silicon, aluminum, calcium, and sludge pyrolysis products are used to replace cement to produce concrete, which can increase the mechanical properties of concrete in the range of 1-5%, and can reach the limit performance of concrete at 10%. my country's annual cement consumption is more than one billion tons, and the concrete production volume is several billion tons. These sludge pyrolysis products are used to replace cement to produce ordinary concrete, which can reduce the use of a large amount of cement, realize energy saving and emission reduction, and make a large amount of sludge pass through heat. After the solution is applied to concrete, it can be effectively treated. The production of sludge into pyrolysis products for concrete production can also avoid various problems caused by sludge disposal methods such as sludge sanitary landfill, incineration, agricultural use and building materials.

(3) The sludge pyrolysis products are black particles, which can be crushed and ground into powder, which is equivalent to the fineness of cement, and can be used instead of cement, saving cement consumption, and the sludge pyrolysis products are anaerobic in the production process, that is, The emission of carbon dioxide and other gases in the cement production process is reduced. The sludge pyrolysis product has strong water absorption, and after replacing a small amount of cement, it can reduce water, thereby enhancing the strength of concrete. Sludge pyrolysis products can solidify heavy metals, etc., and are safer to use in the preparation and production of concrete.

Description of drawings

The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

Figure 1 is a graph showing the relationship between the amount of cement replaced by different sludge pyrolysis products and the compressive strength of C20, C30 and C40 concretes;

Figure 2 is a graph showing the relationship between the amount of sludge pyrolysis product substitution and the flexural and splitting tensile strength of C20 concrete;

Figure 3 is a graph showing the relationship between the amount of sludge pyrolysis product substitution and the flexural and splitting tensile strength of C30 concrete;

Figure 4 is a graph showing the relationship between the amount of sludge pyrolysis product substitution and the flexural and splitting tensile strength of C40 concrete;

Figure 5 is a graph showing the relationship between the substitution amount of sludge pyrolysis products and the slump of concrete in C20, C30 and C40 concrete;

Figure 6 is the electron microscope image of the microstructure of the sludge pyrolysis product of C30 strength grade; a is the undoped sludge pyrolysis product 3000x, b is the 2% sludge pyrolysis product 3000x, and c is the undoped sludge The pyrolysis product is 10000x, and d is 10000x the pyrolysis product of doped 2% sludge;

Figure 7 is the electron microscope image of the microstructure of the sludge pyrolysis product of C40 strength grade; a is the undoped sludge pyrolysis product 3000x, b is the 4% doped sludge pyrolysis product 3000x, c is the undoped sludge pyrolysis product The decomposed product is 10000x, and d is 10000x of the pyrolysis product of doped 4% sludge.

Detailed ways

The embodiments of the present invention will be described in detail below in conjunction with the examples, but those skilled in the art will understand that the following examples are only used to illustrate the present invention and should not be regarded as limiting the scope of the present invention.

Example 1

A preparation method of concrete containing pyrolyzed sludge, comprising the following steps:

Step 1. Preparation of sludge pyrolysate: use any municipal, river, lake and industrial sludge with a moisture content of less than 80%, place an integrated sludge continuous carbonization equipment, heat it up to 600 ° C under anaerobic conditions, and dry heat pyrolysis. In 1 hour, it becomes a coarse-grained solid substance, and its carbon content is between 8.74% and 11.3%. The coarse-grained solid matter is pulverized and pulverized into a particle size that can pass through a 300-mesh sieve to obtain a cohesive powdery sludge pyrolysate. Among them, the components and ash content in the sludge pyrolysate are shown in Table 1.

Table 1 Sludge pyrolysate composition and ash content

Step 2: Mix the pyrolyzed sludge with cement uniformly, add sand, gravel and water, pour it into a mixer and stir evenly at room temperature to obtain concrete containing pyrolyzed sludge; the mixing time for C20 concrete is 60s, The mixing time of C30 and C40 concrete is 90s respectively. Among them, the sand is natural river sand with good particle gradation, which meets the national standard for making ordinary concrete; the continuous gradation of the particle size of the crushed stone is 5-20mm; the cement adopts P.O32.5 and P.O42.5 For ordinary Portland cement or other cement of better quality, the average value and properties of specific components are shown in Table 2.

Table 2 Chemical composition and physical properties of P.O42.5 cement

The above method was used to prepare C20 concrete, C30 concrete and C40 concrete respectively. In order to avoid too many influencing factors, any admixtures such as water reducer were not used; among them, the combinations of the raw materials in the concrete of three strength grades were as shown in Table 3- 5; the total amount of cement and sludge pyrolysate is a fixed value, and the replacement rate refers to the proportion of sludge pyrolyzate to replace cement (that is, the proportion of sludge pyrolyzate to composite cement), according to the ratio of sludge pyrolyzate to cement. 0%, 1%, 2%, 3%, 4%, 5%, 10%, 20% and 30% of the cement mass were used to replace the cement dosage, and concretes with a strength greater than 20MPa were respectively made; 0% is the control group.

Table 3 C20 concrete mix ratio

Table 4 C30 concrete mix ratio

Table 5 C40 concrete mix ratio

test

Test 1: Workability and mechanical properties test of sludge pyrolysis product concrete

1) Test method

The C20 concrete, C30 concrete, and C40 concrete obtained in Example 1 were loaded into the oil-painted trial molds, and were shaken on a vibrating table. After 24 hours of demoulding, they were placed in standard curing for a period of 28 days. The workability, compressive strength, flexural strength and splitting tensile strength of concrete were tested according to the standard of test method for ordinary concrete mixture performance (GB/T50080-2016) and the test method for mechanical properties of ordinary concrete (GBT50081-2002). In the test, the size of the compressive and split tensile test specimens is 100mm×100mm×100mm, and the size of the flexural specimen is 100mm×100mm×400mm.

2) Test results: The average values of concrete compressive, tensile and flexural resistance corresponding to the amount of cement replaced by different sludge pyrolysates are shown in Table 6-8, and the corresponding histograms are shown in Figure 1-4 respectively; The results of the workability test of the pyrolysis products for concrete of three strengths are shown in Figure 5.

Table 6 Mechanical properties of C20 concrete under the conditions of different amounts of sludge pyrolysate substitution

Table 7 Mechanical properties of C30 concrete under the conditions of different amounts of sludge pyrolysate substitution

Table 8 Mechanical properties of C40 concrete under the conditions of different amounts of sludge pyrolysate substitution

(1) Compressive strength of concrete

Figure 1 shows the relationship between the amount of cement replaced by pyrolysis products of sludge and the compressive strength of C20, C30 and C40 compressive strength grades of concrete. It can be seen from Figure 2 and Table 1-3 that the compressive strength of concrete of C20, C30 and C40 compressive strength grades has been improved to varying degrees after adding a certain amount of sludge pyrolysis products; When the amount of cement replaced by mud pyrolysis products is within 5%, the compressive strength is basically improved to different degrees compared with the control group.

It can be seen from Table 6 that the compressive strength of C20 reaches a maximum of 27.12MPa when the amount of cement replaced by sludge pyrolysis products is 10%, which is 5.81% higher than that of the control group; when the amount of cement replaced by sludge pyrolysis products is 20% and 30%. %, the compressive strength decreased significantly; but the compressive strength of concrete with 20% of the sludge pyrolysis product substitution amount could still reach the construction standard of C20.

It can be seen from Table 7 that the compressive strength of C30 concrete reaches a peak value of 37.17MPa when the amount of cement replaced by sludge pyrolysis products is 2%, which is 3.3% higher than that of the control group. group decreased by 11.67%; when the amount of cement replaced by sludge pyrolysis products was 20% and 30%, the compressive value of C30 concrete failed to meet the standard for use.

It can be seen from Table 8 that the compressive strength of C40 concrete reaches a peak value of 49.22MPa when the replacement amount of sludge pyrolysis products is 4%, which is 13.4% higher than that of the control group; when the replacement cement content is 20%, the concrete reaches C40 compressive strength. The limit value of qualified compressive strength; when the replacement amount is 30%, the compressive strength is reduced to 36.97MPa, which is 14.83% lower than that of the control group.

(2) Splitting tensile and flexural strength of concrete

2.1 Splitting tensile and flexural strength of C20 concrete

Figure 2 is a graph showing the relationship between the replacement amount of sludge pyrolysis products and the flexural and splitting tensile strength of C20 concrete. From Figure 2 and Table 6, it can be seen that the flexural strength and splitting tensile strength of C20 concrete do not change significantly, but the flexural and splitting tensile strengths of C20 concrete with sludge pyrolysis products are generally higher than those of the original one. The control group added with sludge pyrolysis products improved.

It can be seen from Table 6 that the flexural strength of C20 concrete reaches the maximum value of 4.25MPa when the replacement amount of sludge pyrolysis products is 5%, which is 18.38% higher than that of the control group; when the replacement amount is 10%, the flexural strength is 3.94 MPa, which is still 9.75% higher than the control group; the split tensile strength reaches the maximum value of 2.34MPa when the replacement amount of sludge pyrolysis products is 1%, and is still 0.32MPa higher than the control group when the replacement amount is 20%.

2.2 Splitting tensile and flexural strength of C30 concrete

Figure 3 is a graph showing the relationship between the replacement amount of sludge pyrolysis products and the flexural and splitting tensile strength of C30 concrete. As can be seen from Figure 3 and Table 7, when the amount of sludge pyrolysis products to replace cement is 4%, the flexural strength of C30 concrete reaches a peak value of 4.23MPa; when the amount of sludge pyrolysis products is 1%, 2%, 3% and 5%, the flexural strength of concrete increased slightly compared with the control group, which increased by 5.31%, 9.2%, 6.7% and 8.66% respectively; when the amount of sludge pyrolysis product replacement increased to 10%, 20% and At 30%, the flexural strength of concrete decreased by 3.36%, 13.12% and 24.86% respectively compared with the control group.

The effect of sludge pyrolysis products on the splitting tensile strength and flexural strength of C30 concrete is basically the same, and the sludge pyrolysis products have little effect on the splitting tensile strength of C30 concrete. When the amount of cement replaced by sludge pyrolysis products is 1%, it is increased by 6.13% compared with the control group; when the replacement amount is 10% and 20%, the splitting tensile strength of concrete decreases slightly, and the tensile strength is 10%. The average value of is basically the same as the average value of the control group. When the replacement amount increases to 30%, the splitting tensile strength of concrete decreases significantly.

2.3 Splitting tensile and flexural strength of C40 concrete

Figure 4 is a graph showing the relationship between the replacement amount of sludge pyrolysis products and the flexural and splitting tensile strength of C40 concrete. From Figure 4 and Table 8, it can be seen that when the amount of cement replaced by sludge pyrolysis products is 4%, the flexural strength of C40 concrete is the most obvious, reaching 5.13MPa; when the replacement amount is 1%, 2% and 5%, respectively The flexural strength of the control group increased by 4.73%, 6.02% and 1.72%; when the replacement amount was 10%, 20% and 30%, the flexural strength decreased significantly, which were 18.49%, 24.32% and 30.75% lower than those of the control group, respectively. %.

The addition of sludge pyrolysis products has no obvious effect on the splitting tensile strength of C40 concrete, only at 2%, it is 2.22% higher than the control group. According to the law of the reaction in Figure 4, when the substitution amount is within 5%, the splitting tensile strength is basically the same as that of the control group, and the tensile strength decreases at 20% and 30%, which is 17.69% lower than that of the control group. and 20.61%.

2.4 Influence of sludge pyrolysis products on workability of concrete with three strengths

Figure 5 is a graph showing the relationship between the replacement amount of sludge pyrolysis products and the slump of concrete in C20, C30 and C40 concrete. It can be seen from Figure 5 that the slump values of concrete with C20, C30 and C40 strength grades are lower than those of the control group without sludge pyrolysis products when they are mixed with sludge pyrolysis products, and In general, the slump value of concrete decreases with the increase of cement replacement by sludge pyrolysis products. When the amount of cement replaced by sludge pyrolysis products is more than 10%, the value of concrete slump drops significantly; when it is 30%, the concrete mixture appears dry and loose. The concrete mixture showed good cohesion and water retention when the amount of sludge pyrolysis product replacement was within 10% by tapping with a tamping rod on one side of the cone sample that had been subjected to the slump test. When the substitution amount of sludge pyrolysis products is more than 20%, the vertebral body slumps around; when it is 30%, some stones will segregate, indicating that the cohesion of the concrete is poor at this time.

Experiment 2: Microstructure of concrete

1) Test method:

To test the microscopic properties of concrete, select the crushed test blocks of the control group, the 2% sludge pyrolysis product substitution group of C30, and the C40 4% sludge pyrolysis product substitution group (the one with the highest compressive strength), respectively. Gold spray treatment, scanned at 3k magnification and 10k magnification using a field emission electron microscope, respectively.

2) Test results: as shown in Figure 6-7.

It can be seen from Figures 6-7 that the structures of the control groups with C30 and C40 undoped sludge pyrolysis products are both flocculent calcium silicate hydrate (C-S-H) gels, needle-like ettringite (Aft) and Lamellar, crystalline calcium hydroxide (CH) intertwined state, more cement hydration products. After curing for 28 days, more Aft and CSH can be observed for concrete with sludge pyrolysis products added, and the increase of Aft and CSH is beneficial to the development of concrete strength.

The environmental benefit of the concrete treatment sludge containing the sludge pyrolysis product obtained by the invention

According to the incomplete statistics of China Concrete Network, the total output of commercial concrete in my country in 2018 was 2.547 billion cubic meters, a year-on-year increase of 9.26%. According to the "Regulations for Design of Ordinary Concrete Mix Proportion" (JGJ22-2011), in addition to the preparation of concrete with a strength level of C15 and below, the minimum cementing amount of plain concrete is 250kg/m ³ , and the minimum cementing amount of reinforced concrete is 280kg/m ³ . , prestressed concrete 300kg/m ³ . At present, China's current JGJ55-2000 "Specification for Design of Mixture Proportion of Common Commercial Concrete" stipulates that the minimum amount of cement and mineral admixture shall not be less than 320kg/m ³ , and the amount of cement and mineral admixture used for pumping commercial concrete shall not be less than 300kg/m 3 . m3. Therefore, based on the total amount of commercial concrete in China in 2018, this paper estimates the consumption of cement in concrete building materials in 2018 to be 764.1 million tons with an average cement consumption of 300kg/ ^m3 .

According to the conclusion obtained from the test, the compressive, tensile and anti-splitting standards required in the test method for the mechanical properties of ordinary concrete can still be achieved when the sludge pyrolysis product replaces 10% of the cement content. If the sludge pyrolysis products are applied to the national concrete production, 76.41 million tons of cement can be replaced, and 76.41 million tons of sludge pyrolysis products can be consumed. The sludge pyrolysis temperature and time are different, and the output of sludge pyrolysis products is also different, that is, the amount of sludge stored in the concrete treatment of pyrolysis products is different; the sludge is pyrolyzed at 450°C, 650°C and 850°C for one hour , the yields of sludge pyrolysis products are 47%, 45% and 38% respectively. If the sludge pyrolysis product concrete is applied nationwide in 2018, the amount of sludge that can be treated is shown in Table 9.

Table 9 The amount of sludge treated by concrete containing pyrolyzed sludge

Although the present invention has been described in detail with general description and specific embodiments in this specification, some modifications or improvements can be made on the basis of the present invention, which will be obvious to those skilled in the art. Therefore, these modifications or improvements made without departing from the spirit of the present invention fall within the scope of the claimed protection of the present invention.

Claims (10)

1. A concrete containing pyrolyzed sludge, comprising the following raw materials: composite cement, fine aggregate, coarse aggregate and water; wherein the composite cement comprises cement and pyrolysed sludge. 2 . The concrete containing pyrolyzed sludge according to claim 1 , wherein the fine aggregate is sand; the coarse aggregate is crushed stone, and the particle size of the crushed stone is 5-20 mm. 3 . . 3. The concrete containing pyrolyzed sludge according to claim 2, wherein the mass ratio of the composite cement, sand, gravel and water is: 1: (1-2): (2.5-3.6 ): (0.3-0.6); the mass of the pyrolyzed sludge accounts for 0.01-30% of the mass of the composite cement. 4. The concrete containing pyrolyzed sludge according to claim 3, wherein the mass ratio of the composite cement, sand, gravel and water is: 1: (1.35-1.98): (2.74-3.44 ): (0.45-0.55); the mass of the pyrolyzed sludge accounts for 0.01-10% of the mass of the composite cement. 5. a preparation method of the concrete containing pyrolyzed sludge, is characterized in that, comprises the following steps: Step 1, prepare sludge pyrolysate, for use; Step 2, mixing the pyrolyzed sludge with cement uniformly, adding fine aggregates, coarse aggregates and water, and stirring uniformly at room temperature to obtain concrete containing pyrolysed sludge. 6. The method for preparing concrete containing pyrolyzed sludge according to claim 5, wherein in step 1, the method for preparing pyrolyzed sludge comprises the following sub-steps: The sludge is placed in the integrated sludge continuous carbonization equipment, dry heat pyrolyzed under anaerobic conditions, pulverized and sieved to obtain the sludge pyrolyzed product. 7 . The method for preparing concrete containing pyrolyzed sludge according to claim 6 , wherein the sludge has a moisture content of less than 80%. 8 . 8 . The method for preparing concrete containing pyrolyzed sludge according to claim 6 , wherein the temperature of the dry-heat pyrolysis is 300-900° C., and the time of dry-heat pyrolysis is 0.5-1.5 hours. 9 . . 9 . The method for preparing the concrete containing pyrolyzed sludge according to claim 6 , wherein the sieving is a 300-mesh sieve. 10 . 10 . The method for preparing the concrete containing pyrolyzed sludge according to claim 5 , wherein, in step 2, the stirring time is 60-90 s. 11 .

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