CN110563351B

CN110563351B - Cement-based material for improving chloride ion binding rate and preparation method thereof

Info

Publication number: CN110563351B
Application number: CN201910980848.8A
Authority: CN
Inventors: 蒋林华; 陈赟杰; 严先萃; 朱鹏飞; 查捷; 宋子健
Original assignee: Hohai University HHU
Current assignee: Hohai University HHU
Priority date: 2019-10-16
Filing date: 2019-10-16
Publication date: 2021-12-28
Anticipated expiration: 2039-10-16
Also published as: CN110563351A

Abstract

The invention relates to a cement-based material for improving chloride ion binding rate, which comprises 8-10% of kaolin by taking the mass of portland cement as a reference; 0.8-1.2% of naphthalene sulfonate water reducing agent; 1-3% of calcium nitrate. The preparation method mainly comprises the steps of mixing naphthalene sulfonate water reducing agent and Ca (NO)₃)₂Dissolving in water, ultrasonic dispersing, mixing with ordinary silicate cement and kaolin, and shaping. The cement-based material prepared by the method can obviously improve the binding rate of chloride ions.

Description

Cement-based material for improving chloride ion binding rate and preparation method thereof

Technical Field

The invention relates to a cement-based material, in particular to a cement-based material for improving the chloride ion binding rate and a preparation method thereof.

Background

Since the advent of concrete technology, the problem of concrete durability has been difficult to effectively solve, and the service life is greatly reduced. The concrete material has large brittleness and poor tensile and bending resistance, and needs reinforcement by reinforcing bars, wherein the reinforcing bars are most widely used. The reinforced concrete structure combines the advantages of steel bars and concrete, and is the preferred form in the civil engineering structure design at present. Among them, corrosion of steel bars caused by chloride ions is the most important durability problem of reinforced concrete structures in marine environments or under the action of deicers. External chloride ions enter the interior of the concrete structure and reach the surface of the steel bar mainly through combined actions of diffusion and permeation, adsorption, capillary action, electrochemical migration and the like. When the content of chloride ions on the surface of the steel bar reaches a certain threshold value (critical concentration of chloride ions), the pH value can be rapidly reduced, the passivation film on the surface of the steel bar is damaged, the passivation phenomenon occurs, and the electrochemical corrosion effect is formed, so that the corrosion rate of the steel bar is greatly accelerated. After the reinforcing steel bars are corroded, on one hand, the effective cross-sectional area of the reinforcing steel bars can be reduced, so that the bearing capacity of a reinforced concrete structure is reduced, and the bond stress of the reinforcing steel bars is reduced; on the other hand, the volume of the steel bar is greatly expanded, and the extrusion causes the concrete to crack and peel from the inside, thereby causing the structural integrity to be damaged. The reinforced concrete structure is deteriorated due to corrosion of the steel bars caused by chloride ion corrosion every year, resulting in huge economic loss.

Disclosure of Invention

The invention aims to increase the binding rate of cement and chloride ions and reduce the corrosion of steel bars in a cement-based material, and provides the cement-based material with the improved binding rate of the chloride ions. The cement-based material can enhance the physical adsorption binding capacity of cement to chloride ions, and further reduce the corrosion of the chloride ions to reinforcing steel bars.

The technical scheme adopted by the invention is as follows: a cement-based material for improving the binding rate of chloride ions comprises the following components in parts by mass based on the mass of cement

100% of Portland cement;

8-10% of kaolin;

0.8-1.2% of naphthalene sulfonate water reducing agent;

1-3% of calcium nitrate.

Further, the kaolin is sandy kaolin.

Further, the Portland cement further comprises graphene and a nano material dispersing agent, wherein the using amount of the graphene is 0.05-0.10% of the mass of the Portland cement.

Further, the nano material dispersing agent is sodium dodecyl benzene sulfonate.

Further, the thickness of the graphene is 2.0-4.0 nm, and the specific surface area is 360-450 m²/g。

The invention also relates to a preparation method of the cement-based material for improving the chloride ion binding rate, which comprises the following steps

S01, dissolving 0.05-0.10% of graphene, a nano material dispersant, 0.5-1.5% of a naphthalenesulfonate water reducer and 1-3% of calcium nitrate into mixing water, and performing ultrasonic dispersion to obtain a mixing water solution;

s02, mixing and stirring the portland cement, the kaolin and the mixed water solution to form cement paste;

s03, forming the cement paste with fluidity;

0.05-0.10% of graphene, 0.5-1.5% of naphthalene sulfonate water reducing agent and 1-3% of calcium nitrate are based on the dosage of portland cement.

Further, in the step S01, the ultrasonic time is 30-40 minutes, the ultrasonic frequency of the ultrasonic wave is 40kHz, and the power density is 0.5-0.7 w/cm²。

Further, the dosage of the kaolin is 8-10% of that of the portland cement.

The beneficial effects produced by the invention comprise: the graphene nanosheets in the cement-based material can improve the workability and strength of concrete, and can promote the microcrystallization of cement components and attach to C-S-H gel on a microscopic level, so that the capacity of adsorbing and combining chloride ions by the C-S-H gel is improved. Ca (NO) in cement-based materials₃)₂Soluble calcium ions can be introduced into the cement-based material to obtain C-S-H gel with higher Ca/Si ratio, so that the physical adsorption binding capacity to chloride ions is enhanced, and the method can greatly improve the chloride ion binding rate of the cement-based material.

The naphthalene sulfonate water reducing agent not only reduces the water consumption and improves the strength of cement-based materials, but also can wrap cement particles on a microscopic level, so that the specific surface area of the cement particles is increased, the hydration degree is improved after the conventional maintenance for 28 days, more hydration products which are easy to combine with free chloride ions are generated, and the performance of combining with the chloride ions is improved. The kaolin added by the method increases the raw materials for forming cement components capable of combining with chloride ions, and also improves the physical and chemical chloride ion combining capability of the cement-based materials. In conclusion, the cement-based material for improving the chloride ion binding rate increases cement hydration products C-S-H gel and C capable of binding chloride ions through the combined action of all components₃AH₆The content and the Ca/Si ratio are improved, and the chloride ion binding rate of the cement-based material can be obviously and effectively improved.

Detailed Description

The present invention is explained in further detail below with reference to specific embodiments, but it should be understood that the scope of the present invention is not limited to the specific embodiments.

Comparative example

Raw materials: ordinary portland cement. The preparation process comprises the following steps:

(1) mixing ordinary Portland cement and mixing water according to the water cement ratio of 0.5, and stirring to form cement paste.

(2) Pouring the slurry with fluidity into a 40X 160mm mold for molding, demolding after 24 hours, and curing for 28 days under the conditions that the relative humidity is 60% and the temperature is 22 ℃.

Example 1

Raw materials: ordinary portland cement, kaolin, naphthalene sulfonate water reducing agent, graphene, nano material dispersant and Ca (NO)₃)₂. The preparation process comprises the following steps:

(1) graphene accounting for 0.05 percent of the mass of the cement, a nano material dispersant, a naphthalene sulfonate water reducing agent accounting for 0.8 percent of the mass of the cement and Ca (NO) accounting for 2 percent of the mass of the cement₃)₂Dissolving in mixed water, and performing ultrasonic dispersion for 40 min at ultrasonic frequency of 40kHz and power density of 0.6w/cm²。

(2) Ordinary portland cement, kaolin accounting for 8 percent of the mass of the cement and the ultrasonically dispersed mixing water solution are mixed and stirred according to the water cement ratio of 0.5 to form cement paste.

(3) Pouring the slurry with fluidity into a 40X 160mm mold for molding, demolding after 24 hours, and curing for 28 days under the conditions that the relative humidity is 60% and the temperature is 22 ℃.

Example 2

(1) graphene accounting for 0.10 percent of the mass of the cement, a nano material dispersant, a naphthalene sulfonate water reducing agent accounting for 1.2 percent of the mass of the cement and Ca (NO) accounting for 2 percent of the mass of the cement₃)₂Dissolving in mixed water, and performing ultrasonic dispersion for 40 min at ultrasonic frequency of 40kHz and power density of 0.6w/cm²。

Example 3

(1) graphene accounting for 0.10% of the mass of the cement, a nano material dispersing agent, a naphthalene sulfonate water reducing agent accounting for 1.2% of the mass of the cement and Ca (NO) accounting for 3% of the mass of the cement₃)₂Dissolving in mixed water, and performing ultrasonic dispersion for 40 min at ultrasonic frequency of 40kHz and power density of 0.6w/cm²。

(2) Ordinary portland cement, kaolin accounting for 10 percent of the mass of the cement and the ultrasonically dispersed mixing water solution are mixed and stirred according to the water cement ratio of 0.5 to form cement paste.

And after the steps, chiseling the outer surface of the test piece by using a geological hammer, cutting the test piece into small pieces by using a cutting machine, appropriately crushing the small pieces by using a crusher, screening the small pieces to obtain a plurality of particles with the particle size of 0.63-1.25 mm, and drying the particles in a blast drying oven at 40 ℃ for 24 hours. 20g of each particle is weighed and placed in a 100mL plastic bottle, 80mL of 0.1mol/L sodium chloride solution is added, and the mixture is sealed, shaken up and kept stand. After 14 days of standing, the solution is filtered off and 10mL of filtrate are titrated potentiometrically with 0.05mol/L silver nitrate solution to give the volume V (mL) consumed. The obtained corresponding chloride ion binding rate B is as follows: b = (0.1-V × 0.05/10)/0.1=1-V/20

The improvement rate of chloride ion binding compared with the comparative example is as follows: p_B=(B-B₀)/B₀×100%

The results obtained are shown in table 1.

Table 1 shows the binding rate B and binding enhancement rate P of chloride ions in each example_B

	Chloride ion binding Rate B	Chloride ion binding enhancement ratio P_B
			Comparative example	18.4%	/
Example 1	25.8%	40.2%
			Example 2	26.6%	44.6%
Example 3	28.1%	52.7%

According to the implementation results, the cement-based material has obvious effects in the chloride ion binding rate compared with the common Portland cement, and the chloride ion binding rate of the cement-based material in the invention is as high as 52.7%.

The embodiments described above are intended to facilitate one of ordinary skill in the art in understanding and using the present invention. It will be readily apparent to those skilled in the art that various modifications to these embodiments may be made, and the generic principles described herein may be applied to other embodiments without the use of the inventive faculty. Therefore, the present invention is not limited to the embodiments described herein, and those skilled in the art should make improvements and modifications within the scope of the present invention based on the disclosure of the present invention.

Claims

1. A preparation method of a cement-based material for improving the chloride ion binding rate is characterized by comprising the following steps: based on the mass of the portland cement, the portland cement mortar comprises the following components in parts by mass:

100% of Portland cement;

10% of sandy kaolin;

1.2 percent of naphthalene sulfonate water reducing agent;

3% of calcium nitrate;

0.10% of graphene;

the nano material dispersant is sodium dodecyl benzene sulfonate;

the thickness of the graphene is 2.0-4.0 nm, and the specific surface area is 360-450 m²/g；

The method comprises the following steps:

s01, dissolving 0.10% of graphene, a nano material dispersant, 1.2% of a naphthalene sulfonate water reducing agent and 3% of calcium nitrate into mixed water together, and performing ultrasonic dispersion to obtain a mixed water solution; the ultrasonic time is 40 minutes, the ultrasonic frequency of the ultrasonic wave is 40kHz, and the power density is 0.6w/cm²；

S02, mixing and stirring the Portland cement, the kaolin and the mixed water solution according to the water cement ratio of 0.5 to form cement paste;

s03, pouring the cement paste with fluidity into a mould for forming, demoulding after 24 hours, and curing for 28 days under the conditions that the relative humidity is 60% and the temperature is 22 ℃;

0.10 percent of graphene, 1.2 percent of naphthalene sulfonate water reducing agent and 3 percent of calcium nitrate are all based on the dosage of portland cement;

the chloride ion binding rate B of the cement-based material is 28.1%.

2. A cementitious material, characterized by being produced by the method of claim 1.