CN100384769C - Preparation method of cement-based graphite steel fiber composite conductive material - Google Patents

Abstract

The invention discloses a preparation method of a cement-based graphite steel fiber composite conductive material, which belongs to the technical field of new materials. The purpose is to provide a new cement-based composite material for bridge deck and road surface that conducts heat and melts snow and deices. This new composite material can also be used on structural components for self-monitoring of structural damage. The present invention is characterized in that steel fibers are spread in the mould, and then the high-fluidity slurry prepared by cement graphite mortar and high-efficiency water reducer is injected into the mould, and a new type of conductive building material is formed after curing. The effect and benefit of the present invention are that the new cement-based composite material has low resistivity, excellent mechanical properties and good long-term stability of resistivity, and the resistivity has no obvious change for more than 2 years. The material is simple to produce and low in cost, and is widely used in projects such as snow melting and deicing of bridge decks and pavements in winter, indoor ground heating, and self-monitoring of structural damage, and can generate huge economic and social benefits.

Description

Preparation method of cement-based graphite steel fiber composite conductive material

technical field

The invention belongs to the technical field of new materials, and relates to a method for manufacturing a high-strength and low-resistivity novel building material by using graphite and high-volume steel fibers as conductive phases.

Background technique

In recent years, with the development of buildings towards intelligence, the requirements for the versatility and intelligence of common building materials have become increasingly urgent. Building bridge deck materials and pavement materials have stable low resistivity to melt snow and deice in winter; use high-strength and low-resistivity materials to manufacture structural components, and monitor structural damage by monitoring small changes in resistivity. These are building intelligence important aspects of. To achieve this goal, it is necessary to use stable and reliable building materials with high strength and low resistivity. Cement-based composite materials are the largest building materials. At present, there are mainly three methods for modifying the conductivity of cement-based composite materials at home and abroad, namely: using graphite as the conductive phase to achieve material conductivity; using low-volume steel fibers and Steel shavings are used as the conductive phase to realize the conductivity of the material; carbon fibers are used as the conductive phase to realize the conductivity of the material. These three methods can reduce the resistivity of the composite material to less than 10Ω.m, which can generally meet the requirements of electrical conductivity, but there are also certain disadvantages: using graphite as the conductive phase to realize the electrical conductivity of the material, this method is due to graphite The incorporation of graphite will significantly reduce the strength of the material. Generally, when the graphite content reaches about 10% of the cement weight, the loss of compressive strength will reach more than 90%, and the strength will be reduced below 10MPa, which cannot meet the structural force requirements. The conductivity of the material is achieved by using low-volume steel fibers and steel shavings as the conductive phase. This method is based on the traditional mixing process to form composite materials. Due to the limitation of the mixing process, the content of steel fibers is difficult to exceed 1%. Its biggest disadvantage is the poor stability of the electrical conductivity (resistivity) of the material. Generally, due to the corrosion and oxidation passivation of steel fibers and steel shavings after one year, its resistivity can increase by more than 100 times the initial value, basically losing It cannot continue to be used due to the loss of electrical conductivity. The carbon fiber is used as the conductive phase to realize the electrical conductivity of the material. Due to the high price of carbon fiber, the application of this method is very uneconomical, thus affecting its wide-scale use.

Contents of the invention

The purpose of the present invention is to provide a new type of building material for the bridge deck and road surface that has good mechanical properties and can conduct heat and solve the problem of snow melting and deicing on bridges and road surfaces in winter; this material can also be used in building structures. The purpose of self-monitoring of structural damage is realized by the small change of material resistivity in the process of force.

The basic principle of the present invention is: high volume rate steel fiber and graphite particles form a conductive network together in the composite material matrix, due to the joint action of the two conductive networks, and the good long-term stability of the graphite ion conductive network, the new composite material The resistivity is very low and the compressive strength and flexural strength are greatly improved, which avoids the disadvantage of serious loss of strength caused by the reduction of resistivity in other methods.

The technical scheme of the present invention uses steel fiber and graphite as the conductive phase of the composite material, and adopts a high-fluidity cement-graphite mortar grouting molding process, which can make the volume ratio of the steel fiber up to more than 15%, and the graphite content is 1/2 of the cement weight. More than 10%. High-dosage steel fibers and graphite form a conductive network in the material matrix. The resistivity of the material is between 5-8Ω.m, the compressive strength can reach more than 80MPa, and the flexural strength can reach more than 30MPa;

The effect and benefit of the present invention are that this cement-based composite material has lower resistivity and excellent mechanical properties (compressive strength is more than 80MPa and flexural strength is more than 30MPa) and good resistivity long-term stability, 2 There is no significant change in resistivity over the years. The material is simple to produce and low in cost, and is widely used in projects such as snow melting and deicing of bridge decks and pavements in winter, indoor ground heating, and self-monitoring of structural damage, and can generate huge economic and social benefits.

Detailed ways

Specific embodiments of the present invention will be described in detail below in conjunction with technical solutions.

Embodiment one:

Step 1. Evenly spread straight steel fibers with a length of 30-40mm and an aspect ratio of 50-60 in a mold of a certain shape, and the volume ratio of the steel fibers is in the range of 16%-18%.

Step 2. Production of cement-graphite-silica fume mortar

The cement is 42.5MPa Portland cement, the graphite is powdered graphite, the fineness is 200-250 mesh, the carbon content is 96-98%, the sulfur content is less than 0.05%, and the moisture content is less than 1%. The sand is fine sand with a particle size of 125-150 μm. The ratio of mortar to sand (weight ratio of cement + graphite + silica fume to sand) is 1:1.25, the weight ratio of cement to silica fume is 10:1, and the weight ratio of cement to graphite is 10:1. The dosage of high-efficiency water reducer is 1% of the sum of the weight of cement + graphite + silica fume. The water-binder ratio (weight ratio of mixing water to cement + graphite + silica fume) is 0.38. Pour the cement graphite into the mortar mixer and stir for 30-60 seconds, then pour the sand into the mixer and stir for 30-60 seconds, dissolve the superplasticizer in the mixing water and slowly pour it into the mixer for 60 seconds.

Step 3. Inject the slurry made in step 2 into the mold in which steel fibers have been evenly spread in step 1. In order to make the slurry evenly embed in the steel fiber layer, the mold can be moderately vibrated. If it is a component, it can be cured in a curing room with a temperature of 20±2°C and a relative humidity greater than 90% for 28 days, and then the formwork can be removed. If it is produced on site, after grouting, cover the surface with a layer of plastic film for maintenance until a certain age.

Embodiment two:

Step 1. Evenly spread special-shaped steel fibers with a length of 30-35mm and an aspect ratio of 40-50 in a mold of a certain shape, and the volume ratio of the steel fibers is in the range of 15%-16%.

Step 2 and step 3 are the same as above.

Claims (1)

1. method for preparing cement base graphite steel fiber composite conductive material, be spreading length 30mm-40mm in mould, length-to-diameter ratio is the straight shape steel fiber of 50-60, the volume volume 16%-18% of steel fiber, the slip that cement graphite mortar and high efficiency water reducing agent are mixed with injects mould again, a kind of conducing composite material that forms through maintenance; It is characterized in that utilizing graphite and steel fiber as conductive phase, adopt fineness 200 orders-250 order, the powder graphite of carbon content 96%-98%, sand adopts fine sand, particle diameter 125 μ m-150 μ m; Cement mortar rate is that cement+graphite+silicon ash is 1: 1.25 with the weight ratio of sand, the weight ratio of cement and silicon ash is 10: 1, cement and graphite weight ratio are 10: 1, the high efficiency water reducing agent volume is 1% of cement+graphite+silicon ash weight sum, water-cement ratio is that mixing water and cement+graphite+silicon ash weight ratio are 0.38, make slip through stirring, adopt slip casting technology, the preparation cement base graphite steel fiber composite conductive material.