CN103553380B - Cement containing large volume of fly ash and preparation method thereof - Google Patents

Abstract

The invention provides a high-volume fly ash cement, which comprises: 30-70wt% of fly ash; 0.01-10wt% of nano-boehmite; the balance is Portland cement. Nano-boehmite particles are small, have excellent chemical and mechanical properties and good surface activity, can fill the gaps of cement particles, and enhance the force between cement particles; and nano-boehmite can be combined with cement clinker and fly ash A chemical reaction occurs to generate hydration products and promotes the early hydration of cement. Therefore, not only the early strength of cement is improved, but also the amount of fly ash added is increased, which reduces the cost.

Description

A large amount of fly ash cement and its preparation method

technical field

The invention relates to the field of large-volume cement, in particular to large-volume fly ash cement and a preparation method thereof.

Background technique

Cement is an important building material widely used in roads, bridges, buildings and other infrastructure constructions. However, the cement production process needs to consume a large amount of cement clinker, and the production of cement clinker will consume a large amount of natural materials and cause serious environmental pollution. Using Portland cement clinker as little as possible and using industrial waste residue as much as possible to produce cement is a topic with environmental protection significance and economic value.

Fly ash is one of the industrial wastes with the largest emission and stacking volume at present, but in our country, its utilization rate is less than 40%, and the remaining fly ash can only be stacked in a large area, which not only pollutes the environment, but also occupies Land Resources.

In order to make full use of fly ash, researchers have invented high-volume fly ash cement, in which the doping amount of fly ash is higher than 40% of the total mass of cement. However, due to the low activity of fly ash, the early strength of cement decreases significantly with the increase of its content in cement, which limits its application range.

Contents of the invention

The technical problem solved by the invention is to provide a large-volume fly ash cement with high early strength.

The invention discloses a large-volume fly ash cement, which comprises the following components:

30-70wt% fly ash;

0.01-10wt% nano-boehmite;

The balance is Portland cement.

Preferably, the D50 of the nano boehmite is less than 20nm.

Preferably, the D95 of the nano-boehmite is less than 40nm.

Preferably, 0.1-2.5wt% nano-boehmite is included.

Preferably, 41-60wt% of fly ash is included.

Preferably, the Portland cement is PI type Portland cement.

The invention discloses a preparation method of large-volume fly ash cement, which comprises the following steps:

The nano-boehmite is evenly doped in the fly ash and Portland cement to obtain a large amount of fly ash cement.

Compared with the prior art, the large-volume fly ash cement of the present invention includes: 30-70wt% fly ash; 0.01-10wt% nano-boehmite; the balance is portland cement. Nano-boehmite particles are small, with excellent chemical and mechanical properties and good surface activity, which can fill the gaps of cement particles and enhance the force between cement particles; and nano-boehmite can chemically react with Portland cement , generate hydration products, and promote the early hydration of cement mixed with a large amount of fly ash, so it not only improves the early strength of cement but also increases the amount of fly ash added, reducing the cost.

Description of drawings

Fig. 1 is the SEM photograph of the nano boehmite that embodiment 1 adopts;

Fig. 2 is the XRD spectrum of the cement of Example 1 and Comparative Example 1 after hydration.

Detailed ways

In order to further understand the present invention, the preferred embodiments of the present invention are described below in conjunction with examples, but it should be understood that these descriptions are only to further illustrate the features and advantages of the present invention, rather than limiting the claims of the present invention.

The embodiment of the present invention discloses a large-volume fly ash cement, which includes the following components:

30-70wt% fly ash;

0.01-10wt% nano-boehmite;

The balance is Portland cement.

The present invention uses nano-boehmite as a reinforcing agent, which can not only fill the gaps of cement particles, make its structure more compact, strengthen the force between cement particles, but also chemically react with cement clinker and fly ash to form Hydration products, promote the hydration process of cement and improve the early strength of cement.

The purity of the nano-boehmite is preferably greater than 98%, the D50 of the nano-boehmite is preferably less than 20nm, and the D95 of the nano-boehmite is preferably less than 40nm. The content of the nano-boehmite is preferably 0.01-10wt%, more preferably 0.1-2.5wt%. In the present invention, there is no special limitation on the source of the nano-boehmite, and commercially available products can be used.

In the present invention, the fly ash is an important doping raw material, and the doping of a large amount of fly ash reduces the production cost. The content of the fly ash is 30-70wt%, preferably 41-60wt%.

In the present invention, the balance of Portland cement is also included. The present invention has no special limitation on the type of Portland cement, which may be PI type Portland cement without mixing materials, or PII type Portland cement, preferably PI type Portland cement. The present invention has no special limitation on the source of Portland cement, and commercially available products can be used.

The invention also discloses a preparation method of large-volume fly ash cement, comprising the following steps:

The nano-boehmite is evenly doped in the fly ash and Portland cement to obtain a large amount of fly ash cement.

The nano-boehmite must be uniformly doped in the fly ash and Portland cement, and the present invention has no special limitation on the specific doping method. The nano-boehmite can also be mixed with fly ash and Portland cement when in use. The preferred solution is: ultrasonically disperse the nano-boehmite in water, and the ultrasonic dispersion time is preferably 5 to 15 minutes ; Then, mix the fly ash and Portland cement with the aqueous solution uniformly dispersed with nano-boehmite, and then it can be used.

The high-volume fly ash cement of the present invention comprises: 30-70 wt% of fly ash; 0.01-10 wt% of nano-boehmite; the balance is Portland cement. Nano-boehmite particles are small, with excellent chemical and mechanical properties and good surface activity, which can fill the gaps of cement particles and enhance the force between cement particles; and nano-boehmite can chemically react with Portland cement , generate hydration products, and promote the early hydration of cement mixed with a large amount of fly ash, so it not only improves the early strength of cement but also increases the amount of fly ash added, reducing the cost. In addition, the present invention uses the method of doping nano-boehmite to increase the early strength of high-volume fly ash cement, and the process is simple, which provides a new way for expanding the application of high-volume fly ash cement.

In order to further understand the present invention, the following examples illustrate the large-volume fly ash cement provided by the present invention and its preparation method, and the protection scope of the present invention is not limited by the following examples.

The nano-boehmite used in the following examples is produced by Sasol Company of the United States.

Example 1

The high-volume fly ash cement in this embodiment includes 220.5 grams of PI type Portland cement cement clinker (gypsum accounts for 4% of the clinker mass), 220.5 grams of fly ash and 9 grams of nano boehmite. The particle size of the nano-boehmite is 10-50 nm, and the specific structure is shown in FIG. 1 . FIG. 1 is a SEM photo of the nano-boehmite used in Example 1.

The large-volume fly ash cement in Example 1 was made into cement mortar to test its early strength.

Disperse 9 grams of nano-boehmite in water evenly for 10 minutes, with an ultrasonic power of 300w (DS-5510DTH ultrasonic cleaning machine), and then prepare cement mortar specimens according to the preparation process of ordinary cement mortar specimens in my country's current standards. After the test piece is made, put it into a standard curing room (temperature 20±1°C, relative humidity ≥95%) for curing, remove the mold after 1 day and continue the standard curing to the set age, and then the cement mortar test piece can be obtained. The components of the cement mortar test piece are shown in Table 1.

Table 1 Components of cement mortar test piece

After curing to the experimental age, the cement specimen was taken out, and its flexural strength and compressive strength were tested by flexural testing machine and compression testing machine for 3 days. The specific experimental data are shown in Table 2.

Table 2 3D strength comparison of cement mortar specimens

Comparative example 1

The large-volume fly ash cement in this comparative example includes 225 grams of PI type Portland cement and 225 grams of fly ash.

Prepare cement mortar specimens according to the preparation process of ordinary cement mortar specimens in my country's current standards. After the specimens are prepared, put them in a standard curing room (temperature 20±1°C, relative humidity ≥95%) for curing, and disassemble them after 1 day. The mold and continue the standard maintenance to the set age, and then the cement mortar test piece can be obtained. The components of the cement mortar test piece are shown in Table 1.

It can be seen from the data in Table 2 that nano-boehmite can significantly improve the compressive and flexural strength of high-volume fly ash cement, in which the flexural strength increased by 27.6%, and the compressive strength increased by 29.5%.

Therefore, adding a small amount of nano-boehmite to high-volume fly ash cement can significantly improve the early strength of cement.

Simultaneously X-ray diffractogram is as shown in Figure 2, and Fig. 2 is the XRD collection of illustrative plates after the cement hydration of embodiment 1 and comparative example 1, and wherein A is the XRD collection of illustrative plates after the cement hydration of embodiment 1, and B is the XRD collection of illustrative plates of comparative example 1 XRD pattern of cement after hydration. Fig. 2 shows that embodiment 1 generates hydrated garnet and more calcium hydroxide after adding nano-boehmite, indicating that the hydration of cement is promoted.

Example 2

The high-volume fly ash cement in this embodiment includes 218.25 grams of PI type Portland cement, 225 grams of fly ash and 6.75 grams of nano-boehmite. The particle size of the nano-boehmite is 10-50 nm.

The large-volume fly ash cement in Example 1 was made into cement mortar to test its early strength.

Disperse 11.25 grams of nano-boehmite in water evenly for 10 minutes, with an ultrasonic power of 300w (DS-5510DTH ultrasonic cleaning machine), and then prepare cement mortar specimens according to the preparation process of ordinary cement mortar specimens in my country's current standards. After the test piece is made, put it into a standard curing room (temperature 20±1°C, relative humidity ≥95%) for curing, remove the mold after 1 day and continue the standard curing to the set age, and then the cement mortar test piece can be obtained. The components of the cement mortar test piece are shown in Table 1.

After curing to the experimental age, the cement specimen was taken out, and its flexural strength and compressive strength were tested by flexural testing machine and compression testing machine for 3 days. The specific experimental data are shown in Table 2.

Example 3

The high-volume fly ash cement in this embodiment includes 213.75 grams of PI type Portland cement, 225 grams of fly ash and 11.25 grams of nano-boehmite. The particle size of the nano-boehmite is 10-50 nm.

The large-volume fly ash cement in Example 1 was made into cement mortar to test its early strength.

Disperse 11.25 grams of nano-boehmite in water evenly for 10 minutes, with an ultrasonic power of 300w (DS-5510DTH ultrasonic cleaning machine), and then prepare cement mortar specimens according to the preparation process of ordinary cement mortar specimens in my country's current standards. After the test piece is made, put it into a standard curing room (temperature 20±1°C, relative humidity ≥95%) for curing, remove the mold after 1 day and continue the standard curing to the set age, and then the cement mortar test piece can be obtained. The components of the cement mortar test piece are shown in Table 1.

After curing to the experimental age, the cement specimen was taken out, and its flexural strength and compressive strength were tested by flexural testing machine and compression testing machine for 3 days. The specific experimental data are shown in Table 2.

Example 4

The high-volume fly ash cement in this embodiment includes 202.5 grams of PII type Portland cement, 225 grams of fly ash and 22.5 grams of nano boehmite. The particle size of the nano-boehmite is 10-50 nm.

The large-volume fly ash cement in Example 1 was made into cement mortar to test its early strength.

Disperse 11.25 grams of nano-boehmite in water evenly for 10 minutes, with an ultrasonic power of 300w (DS-5510DTH ultrasonic cleaning machine), and then prepare cement mortar specimens according to the preparation process of ordinary cement mortar specimens in my country's current standards. After the test piece is made, put it into a standard curing room (temperature 20±1°C, relative humidity ≥95%) for curing, remove the mold after 1 day and continue the standard curing to the set age, and then the cement mortar test piece can be obtained. The components of the cement mortar test piece are shown in Table 1.

After curing to the experimental age, the cement specimen was taken out, and its flexural strength and compressive strength were tested by flexural testing machine and compression testing machine for 3 days. The specific experimental data are shown in Table 2.

The descriptions of the above embodiments are only used to help understand the method and core idea of the present invention. It should be pointed out that for those skilled in the art, without departing from the principle of the present invention, some improvements and modifications can be made to the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

The above description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the present invention will not be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims (7)

1. a large-doping-amount fly ash cement, comprises following component:

The flyash of 30 ~ 70wt%;

The nm boehmite of 0.01 ~ 10wt%;

Surplus is silicate cement.

2. large-doping-amount fly ash cement according to claim 1, is characterized in that, the D50 of described nm boehmite is less than 20nm.

3. large-doping-amount fly ash cement according to claim 1, is characterized in that, the D95 of described nm boehmite is less than 40nm.

4. large-doping-amount fly ash cement according to claim 1, is characterized in that, comprises the nm boehmite of 0.1 ~ 2.5wt%.

5. large-doping-amount fly ash cement according to claim 1, is characterized in that, comprises the flyash of 41 ~ 60wt%.

6. large-doping-amount fly ash cement according to claim 1, is characterized in that, described silicate cement is PI type silicate cement.

7. a preparation method for large-doping-amount fly ash cement as claimed in claim 1, comprises the following steps:

By nm boehmite Uniform Doped in flyash and silicate cement, obtain large-doping-amount fly ash cement.