CN111704405A - A kind of sisal nanocellulose ultra-high toughness concrete and preparation method thereof - Google Patents

Abstract

The invention discloses sisal hemp nano cellulose ultra-high toughness concrete and a preparation method thereof, wherein the sisal hemp nano cellulose ultra-high toughness concrete comprises the following components in percentage by mass: 10 to 15 percent of Portland cement, 1.5 to 2 percent of fly ash, 2 to 5 percent of slag, 30 to 35 percent of fine aggregate, 44 to 48 percent of coarse aggregate, 0.1 to 0.2 percent of water reducing agent and 0 to 0.1 percent of sisal nanocellulose. The sisal hemp nano cellulose ultra-high toughness concrete comprehensively utilizes two solid wastes of fly ash and slag, and the ultra-toughness sisal hemp nano cellulose is added, so that under the action of a water reducing agent, through reasonable proportioning design, the tensile property of the prepared sisal hemp nano cellulose ultra-high toughness concrete is far higher than that of common concrete, and meanwhile, the internal pore structure of the concrete can be improved to improve the durability of the concrete.

Description

A kind of sisal nanocellulose ultra-high toughness concrete and preparation method thereof

technical field

The invention relates to the technical field of civil engineering, in particular to a sisal nanocellulose ultra-high toughness concrete and a preparation method thereof.

Background technique

At the nano and atomic level, the brittle fracture of cementitious composites is due to the relative displacement of ceramic ionic covalent bonds at room temperature. Adding nano-scale cellulose to concrete with brittle mechanical properties is of great significance for the improvement of its mechanical properties. Adding plant nanofibers to cement materials can provide good stress bridging and enhance the toughness, tensile and flexural properties of concrete. Foreign scholars have incorporated nanofibers into cement materials to improve the mechanical properties of concrete after cracking. The mechanical properties of concrete can be improved by incorporating nanofibers into concrete. Plant fibers are generally transformed into plant nanofibers by mechanical methods rather than chemical methods, which reduces the damage to the mechanical properties of plant fibers. Through mechanical shear force, plant fibers with a geometric size in the mm order are turned into plant nanofibers with a geometric size in the nm order. Due to the change of the geometric shape, the specific surface area is increased, thereby potentially increasing the bonding with the cementitious material. Because the concrete pores are alkaline, the ionic bonds of the nanofibers are destroyed, that is, the plant nanofibers undergo a hydrolysis reaction in an alkaline environment, reducing the degree of polymerization; therefore, by making plant fibers into nanofibers and incorporating them into cement materials to Reinforced concrete has a very broad development prospect. Because plant nanofibers can enhance the crack resistance of concrete, delay the invasion of external harmful ions (such as chloride ions, sulfate ions, etc.), improve the durability of the structure, and increase the service life of the structure, which greatly saves economic costs and resources. use. To sum up, the use of plant nanofibers to add to concrete has great economic benefits, provides new ways to utilize local advantageous resources and extend the industrial chain, and is of great significance to protecting the environment and promoting the sustainable and healthy development of the local economy.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a kind of sisal nanofiber ultra-high toughness concrete and preparation method thereof, and this sisal nanocellulose ultra-high toughness concrete comprehensively utilizes these two solid wastes of fly ash and slag, plus Compared with ordinary concrete, hemp nanofibers can improve the tensile strength of concrete, enhance the toughness of concrete, improve the internal pore structure, and have low permeability. , to improve the durability of concrete.

In order to achieve the above purpose, the sisal nanofiber ultra-high toughness concrete provided by the present invention and its preparation method are composed of the following components in terms of mass percentage: Portland cement 5%-20%, fly ash 0.8%-2%. %%, slag 1.5%～6%, fine aggregate 30%～40%, coarse aggregate 40%～50%, water 5%～10%, water reducing agent 0.02%～0.3%, plant nanocellulose 0% ~5%.

As a preferred solution, the sisal nanofiber ultra-high toughness concrete is composed of the following components in terms of mass percentage: Portland cement 10%-15%, fly ash 1.5%-2%, slag 2%-5%, fine Aggregate 30%-35%, coarse aggregate 44%-48%, water 5%-8%, water reducing agent 0.1%-0.2%, plant nanocellulose 0%-1%.

As the best solution, the sisal nanofiber ultra-high toughness concrete is composed of the following components by mass percentage: Portland cement 11.29%, fly ash 1.61%, slag 3.23%, fine aggregate 33.57%, coarse bone Material 44.34%, water 6.97%, water reducing agent 0.17%, plant nanocellulose 0.56%.

Further, the plant nanocellulose is sisal nanocellulose.

Further, the sisal nanocellulose is prepared by using sisal fiber pulp (SP) as a raw material, and 40.0 g of powdery sisal fiber pulp samples are put into sodium chlorate (NaOCl) with a mass fraction of 10% to 20%. % 420mL solution for bleaching, the bleaching time is 20-25 minutes, and the bleaching temperature is between 150°C and 170°C.

Further, for the sisal nanocellulose, bleached sisal fiber pulp (SP) is soaked in a sodium hydroxide solution with a concentration of 2M for 2 hours at a temperature of 155°C to 160°C.

Further, the shrinkage inhibitor is one or both of a polycarboxylate superplasticizer and a naphthalene-based water reducer.

Further, the Portland cement is P·II52.5 Portland cement, the fly ash is FII grade low calcium fly ash, the slag is S95 grade ground slag, and its surface area is 330-360 m ² / kg. .

The present invention also provides the preparation method of the above-mentioned sisal nanofiber ultra-high toughness concrete, comprising the following steps:

1) prepare sisal nanofibers, put 40.0g powdery sisal fiber pulp sample into 420mL solution of sodium chlorate (NaOCl) mass fraction of 10%～20% for bleaching, and the bleaching time is 20～25 minutes, The bleaching temperature is between 150°C and 170°C. The bleached sisal fiber pulp (SP) was soaked in a sodium hydroxide solution with a concentration of 2M for 2 hours at a temperature of 155°C to 160°C. Wash with distilled water until the sample pH is neutral.

(2) Degrease and pigment in step (1), use 1.492 g/mL chloroform, 99.8% pure anhydrous methanol and distilled water to form a mixed solution in a volume ratio of 4:2:1, and (1) Soak the sample obtained in the mixed solution for 20 minutes, and then rinse the sample with distilled water until the pH value is neutral;

3) Mix the sample in step 2) with 2M 100mL HCl (1.1g/cm ³ ) solution, and let it stand at 100°C for 10 hours to obtain wet sisal nanocellulose. After standing for 7 days, a white powder of sisal nanocellulose will be obtained.

4) Calculated by mass percentage, Portland cement 10%-15%, fly ash 1.5%-2%, slag 2%-5%, fine aggregate 30%-35%, coarse aggregate 44%-48% %, 5% to 8% of water, 0.1% to 0.2% of a water reducing agent, and 0% to 0.1% of the sisal nanocellulose prepared in step (3), for subsequent use;

5) Mix the Portland cement, fly ash, slag, fine aggregate, coarse aggregate, water reducing agent and sisal nanofiber obtained in step 4), put it into a concrete mixer and stir for 15min, and cure for 28d in a natural state That's it.

Compared with the prior art, the present invention has the following advantages:

First, the present invention utilizes fly ash with large specific surface area and smooth particles, and adding fly ash into concrete changes the original chemical reaction balance in concrete, changes the content of various minerals, and also changes the microstructure of concrete. The influence of fly ash mainly has three aspects: ① Morphological effect. Cement is a composite material composed of various components. There are great differences in the geometric appearance, physical properties of the surface and chemical effects of each material. , for different combinations will produce different physical and chemical effects. ② Active effect, the active effect of fly ash is divided into two kinds, one is the inherent physical property, and the other is the chemical activity related to the chemical effect of the substance. ③ Micro-aggregate effect. The addition of fly ash can enhance the fluidity of concrete and increase the working performance of concrete.

Second, the present invention utilizes the characteristics of high tensile strength of sisal nanofibers, sisal nanofibers improve the internal structure of concrete, and in the stage of concrete microcrack formation, sisal nanofibers utilize high tensile strength to form bridges between cracks, The further development of cracks is prevented, thereby improving the toughness of concrete; at the same time, sisal nanofibers are soluble in water, which solves the problem of poor dispersion of conventional fibers such as steel fibers and sisal fibers, resulting in unstable performance of concrete.

Thirdly, in the present invention, the sisal nanofiber raw material is abundant, and the problem of sisal pollution is solved, and the price is low. Sisal is a filamentous algae that covers a wide range of coastal areas, such as along lakes and oceans; bloomed by algae, especially in hot climates, they cover the entire water surface and, if not removed from the water, can cause lakes, seawater Eutrophication, the removal of these algae is good for the environment.

Fourth, the preparation process of the sisal nanofiber of the present invention is simple and the preparation efficiency is high. The sisal nanofibers in the present invention can be prepared by processes such as bleaching and sulfuric acid hydrolysis. Compared with other preparation processes, processes such as centrifuge purification are omitted, energy consumption is saved, and the preparation speed is also improved.

Fifth, the blast furnace slag of the power plant is used in the present invention to solve the problem of solid waste pollution.

Sixth, the preparation process of the present invention is simple, the raw materials are cheap and easy to obtain, and the cost is obviously lower than that of carbon fiber and steel fiber concrete.

Detailed ways

The present invention will be further described in detail below in conjunction with specific embodiments.

Preparation: Batch preparation of sisal nanofibers (200g)

1) Put 40.0g powdery sisal fiber pulp sample into 420mL solution with sodium chlorate (NaOCl) mass fraction of 10%～20% for bleaching, the bleaching time is 20～25 minutes, and the bleaching temperature is 150℃～ between 170°C. The bleached sisal fiber pulp (SP) was soaked in a sodium hydroxide solution with a concentration of 2M for 2 hours at a temperature of 155°C to 160°C. Wash with distilled water until the sample pH is neutral.

(2) Degrease and pigment in step (1), use 1.492 g/mL chloroform, 99.8% pure anhydrous methanol and distilled water to form a mixed solution in a volume ratio of 4:2:1, and (1) Soak the sample obtained in the mixed solution for 20 minutes, and then rinse the sample with distilled water until the pH value is neutral;

3) Mix the sample in step 2) with 2M 100mL HCl (1.1g/cm ³ ) solution, and let it stand at 100°C for 10 hours to obtain sisal nanocellulose, and place the wet sisal nanocellulose at 40°C for 7 days. day, a white powder of sisal nanocellulose will be obtained.

4) Repeat steps 1) to 3) until the preparation of sisal nanofibers reaches more than 200 g, for subsequent use;

Embodiment 1

The preparation method of the sisal nanocellulose ultra-high toughness concrete provided in the present embodiment is as follows:

1) Proportion of raw materials: Portland cement 11.29%, fly ash 1.61%, slag 3.23%, fine aggregate 33.5%, coarse aggregate 44.9%, water 6.97%, water reducing agent 0.17% by mass percentage of each component %, sisal nanocellulose 0.00%.

2) Mix the Portland cement, fly ash, slag, fine aggregate, coarse aggregate, water, water reducing agent and sisal nanofibers obtained in step 1), put into a concrete mixer and stir for 15min, under natural conditions It can be maintained for 28d.

Embodiment 2

The preparation method of the sisal nanocellulose ultra-high toughness concrete provided in the present embodiment is as follows:

1) Proportion of raw materials: Portland cement 11.29%, fly ash 1.61%, slag 3.23%, fine aggregate 33.5%, coarse aggregate 44.9%, water 6.97%, water reducing agent 0.17% by mass percentage of each component %, sisal nanocellulose 0.06%.

2) Mix the Portland cement, fly ash, slag, fine aggregate, coarse aggregate, water, water reducing agent and sisal nanofibers obtained in step 1), put into a concrete mixer and stir for 15min, under natural conditions It can be maintained for 28d.

Embodiment 3

The preparation method of the sisal nanocellulose ultra-high toughness concrete provided in the present embodiment is as follows:

1) Proportion of raw materials: Portland cement 11.29%, fly ash 1.61%, slag 3.23%, fine aggregate 33.5%, coarse aggregate 44.9%, water 6.97%, water reducing agent 0.17% by mass percentage of each component %, sisal nanocellulose 0.14%.

2) Mix the Portland cement, fly ash, slag, fine aggregate, coarse aggregate, water, water reducing agent and sisal nanofibers obtained in step 1), put into a concrete mixer and stir for 15min, under natural conditions It can be maintained for 28d.

Embodiment 4

The preparation method of the sisal nanocellulose ultra-high toughness concrete provided in the present embodiment is as follows:

1) Proportion of raw materials: Portland cement 11.29%, fly ash 1.61%, slag 3.23%, fine aggregate 33.5%, coarse aggregate 44.9%, water 6.97%, water reducing agent 0.17% by mass percentage of each component %, sisal nanocellulose 0.28%.

2) Mix the Portland cement, fly ash, slag, fine aggregate, coarse aggregate, water, water reducing agent and sisal nanofibers obtained in step 1), put into a concrete mixer and stir for 15min, under natural conditions It can be maintained for 28d.

Embodiment 5

The preparation method of the sisal nanocellulose ultra-high toughness concrete provided in the present embodiment is as follows:

1) Proportion of raw materials: Portland cement 11.29%, fly ash 1.61%, slag 3.23%, fine aggregate 33.5%, coarse aggregate 44.9%, water 6.97%, water reducing agent 0.17% by mass percentage of each component %, sisal nanocellulose 0.42%.

2) Mix the Portland cement, fly ash, slag, fine aggregate, coarse aggregate, water, water reducing agent and sisal nanofibers obtained in step 1), put into a concrete mixer and stir for 15min, under natural conditions It can be maintained for 28d.

Embodiment 6

The preparation method of the sisal nanocellulose ultra-high toughness concrete provided in the present embodiment is as follows:

1) Proportion of raw materials: Portland cement 11.29%, fly ash 1.61%, slag 3.23%, fine aggregate 33.5%, coarse aggregate 44.9%, water 6.97%, water reducing agent 0.17% by mass percentage of each component %, sisal nanocellulose 0.56%.

2) Mix the Portland cement, fly ash, slag, fine aggregate, coarse aggregate, water, water reducing agent and sisal nanofibers obtained in step 1), put into a concrete mixer and stir for 15min, under natural conditions It can be maintained for 28d.

Embodiment 7

The preparation method of the sisal nanocellulose ultra-high toughness concrete provided in the present embodiment is as follows:

1) Proportion of raw materials: Portland cement 11.29%, fly ash 1.61%, slag 3.23%, fine aggregate 33.5%, coarse aggregate 44.9%, water 6.97%, water reducing agent 0.17% by mass percentage of each component %, sisal nanocellulose 0.71%.

2) Mix the Portland cement, fly ash, slag, fine aggregate, coarse aggregate, water, water reducing agent and sisal nanofibers obtained in step 1), put into a concrete mixer and stir for 15min, under natural conditions It can be maintained for 28d.

The performance test of the sisal nanocellulose ultra-high toughness concrete prepared in Embodiments 1 to 7 is carried out. The test proportions are shown in Table 1, and the test results are shown in Table 2.

Table 1 Mixing ratio of sisal nanofiber ultra-high toughness concrete (kg/m ³ )

Table 2 Test results

It can be seen from the test results in Table 1 and Table 2 that the ultra-high-toughness concrete using sisal nanofibers described in Embodiments 1 to 7 has efficient tensile properties, which shows that the addition of sisal nanofibers can effectively improve the concrete's performance. Toughness, the tensile strength of concrete with 0.56% sisal nanofibers is 2.97 times that of ordinary concrete.

The above examples are only to illustrate the technical solutions and features of the present invention, and their purpose is to better enable those who are familiar with the technology to implement them, and cannot limit the scope of protection of the present invention. Changes or modifications are all within the protection scope of the present invention.

Claims (8)

1. The sisal hemp nano cellulose ultra-high toughness concrete is characterized in that the ultra-high toughness concrete is doped with plant nano cellulose, and the concrete comprises the following substances in percentage by mass: 5 to 20 percent of Portland cement, 0.8 to 2 percent of fly ash, 1.5 to 6 percent of slag, 30 to 40 percent of fine aggregate, 40 to 50 percent of coarse aggregate, 5 to 10 percent of water, 0.02 to 0.3 percent of water reducing agent and 0 to 5 percent of plant nano-cellulose.

2. The sisal hemp nano cellulose ultra-high toughness concrete according to claim 1, wherein the ultra-high performance concrete batch comprises the following components in percentage by mass: 10 to 15 percent of Portland cement, 1.5 to 2 percent of fly ash, 2 to 5 percent of slag, 30 to 35 percent of fine aggregate, 44 to 48 percent of coarse aggregate, 5 to 8 percent of water, 0.1 to 0.2 percent of water reducing agent and 0 to 1 percent of plant nano-cellulose.

3. The sisal hemp nano cellulose ultra-high toughness concrete according to claim 2, wherein the ultra-high performance concrete batch comprises the following components in percentage by mass: 11.29 percent of Portland cement, 1.61 percent of fly ash, 3.23 percent of slag, 33.57 percent of fine aggregate, 44.34 percent of coarse aggregate, 6.97 percent of water, 0.17 percent of water reducing agent and 0.56 percent of plant nano-cellulose.

4. The sisal nanocellulose ultrahigh-toughness concrete according to claim 3, wherein the plant nanocellulose is sisal nanocellulose.

5. The sisal nanocellulose ultrahigh-toughness concrete according to claim 4, wherein the sisal nanocellulose is prepared from sisal fiber pulp (SP).

6. The sisal nano-cellulose ultrahigh-toughness concrete according to claim 1, wherein the portland cement is P.II 52.5 portland cement, the fly ash is FII-grade low-calcium fly ash, the slag is S95-grade ground slag, and the surface area of the slag is 330-360 m 2/kg.

7. The sisal hemp nano cellulose ultra-high toughness concrete of claim 1, wherein the water reducing agent is one or two of a polycarboxylate high efficiency water reducing agent and a naphthalene water reducing agent.

8. The preparation method of the sisal nano-cellulose ultra-high toughness concrete according to any one of claims 1-7, comprising the following steps:

(1) preparing sisal hemp nanofibers, putting 40.0g of a powdery sisal hemp fiber pulp sample into 420mL of a solution with 10-20% of sodium chlorate (NaOCl) by mass for bleaching, wherein the bleaching time is 20-25 minutes, the bleaching temperature is 150-170 ℃, soaking bleached sisal hemp fiber pulp (SP) in a sodium hydroxide solution with the concentration of 2M for 2 hours, the temperature is 155-160 ℃, and washing with distilled water until the pH value of the sample is neutral;

(2) degreasing and coloring the product obtained in the step (1), and adding 1.492g/mL of chloroform, absolute methanol with the purity of 99.8% and distilled water according to the volume ratio of 4: 2: 1, preparing a mixed solution, soaking the sample obtained in the step (1) in the mixed solution for 20 minutes, and then washing the sample with distilled water until the pH value is neutral;

(3) mixing the sample obtained in the step (2) with 2M 100mL of HCl solution, standing for 10 hours at 100 ℃ to obtain wet sisal hemp nano-cellulose, and standing the wet sisal hemp nano-cellulose for 7 days at 40 ℃ to obtain white powder of the sisal hemp nano-cellulose;

(4) weighing 10-15% of portland cement, 1.5-2% of fly ash, 2-5% of slag, 30-35% of fine aggregate, 44-48% of coarse aggregate, 5-8% of water, 0.1-0.2% of water reducing agent and 0-0.1% of sisal hemp nano cellulose prepared in the step (3) for later use;

(5) and (4) mixing the portland cement, the fly ash, the slag, the fine aggregate, the coarse aggregate, the water reducing agent and the sisal nano-cellulose obtained in the step (4), putting the mixture into a concrete mixer, stirring for 15 minutes, and naturally curing for 28 days.