JP7139178B2 - Paving material with high heat dissipation - Google Patents

Description

TECHNICAL FIELD The present invention relates to a pavement material with high heat dissipation.

Since asphalt pavement, which has been widely used for roads, is generally black in color, it easily absorbs solar heat from the sun, increasing the temperature of the road surface and contributing to the so-called heat island phenomenon. As a measure to suppress the heat island phenomenon, a pavement structure that can suppress the rise in road surface temperature is desired. As a technology to suppress the temperature rise of the pavement surface, for example, the pavement is provided with a water retention function, and the pavement is made to retain moisture when it rains or is sprinkled with water, and the temperature rise of the pavement is suppressed by the heat of vaporization of the moisture. A suppressing method has been proposed (Patent Document 1).

However, the method using moisture evaporation, such as that disclosed in Patent Document 1, has a problem that the effect of suppressing the temperature rise cannot be obtained when the supply of moisture due to rainfall or water sprinkling is insufficient. Therefore, by adding silica, which has a high thermal conductivity, to the pavement material that has a water-retaining function to increase the thermal conductivity of the entire pavement material, the solar heat received by the surface of the pavement material is transmitted downward, A technique for lowering the surface temperature of pavement has been proposed (Patent Document 2).

JP-A-8-209613 Japanese Patent No. 5898350

Since the temperature of the road surface tends to rise due to the effects of global warming, the pavement material shown in Patent Document 2 does not have a sufficient temperature control effect, and there is a demand for a pavement that further suppresses the temperature rise. .

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a highly heat-dissipating paving material that effectively lowers the surface temperature of the pavement compared to conventional pavement materials.

The inventors of the present invention have found that the increase in the surface temperature of the pavement can be suppressed as compared with the conventional pavement material by including alumina particles with high thermal conductivity in the aggregate of the pavement material within a certain amount range. The discovery led to the completion of the present invention. Specifically, the present invention provides the following.

(1) The present invention comprises an aggregate containing porous slag particles, silica stone and alumina particles, cement, and an admixture, and the alumina particles in the total amount of the silica stone and the alumina particles contained in the aggregate The pavement material contains 10 to 50% by mass of particles.

(2) The present invention is the pavement material according to (1), wherein the total amount of the silica stone and the alumina particles contained in the pavement material is 5 to 25% by mass in the pavement material.

(3) The present invention is the pavement material according to (1) or (2), wherein the alumina particles include alumina particles having one particle size distribution range.

(4) The present invention is the pavement material according to (1) or (2), wherein the alumina particles are a mixture of two types of alumina particles having different particle size distribution ranges.

(5) The present invention is the pavement material according to (4), wherein the content ratio of each of the two kinds of alumina particles to the silica stone is 10 to 50%.

ADVANTAGE OF THE INVENTION According to this invention, compared with the conventional pavement material, the high thermal radiation pavement material which can suppress the rise of the surface temperature of a pavement body can be provided.

FIG. 4 is a schematic diagram for explaining a mechanism for lowering the temperature of pavement;

Embodiments of the present invention will be described below. The invention is not limited by these descriptions.

The pavement material according to this embodiment includes aggregates containing porous slag particles, silica stone and alumina particles, cement, and an admixture. Since a structure containing voids caused by porous slag particles is formed inside the pavement material, concrete was mixed with cement in order to support the load with the pavement material.

The mechanism of heat dissipation by the pavement material according to this embodiment will be described with reference to FIG. A pavement constituting the surface layer 1 of the road is composed of a concrete layer. A roadbed 2 and a roadbed 3 are provided below the surface layer 1 , and the load applied to the surface layer 1 is dispersed by the roadbed 2 and supported by the roadbed 3 . The pavement material according to the present embodiment has a high porosity in the pavement due to the existence of pores between the porous slag particles of the aggregate bonded with cement and the existence of pores in the porous slag particles. Since an internal structure with a modulus is formed, the pavement has water retention and permeability. As a result, water falling on the surface of the surface layer 1 due to rainfall, sprinkled water, etc. 6 seeps into the surface layer 1 (pavement) and is stored inside the pavement, resulting in a water retention state 7 . Further, this water takes heat from the surface layer 1, permeates 8 the roadbed 2 and the roadbed 3, and moves underground. In addition, when the water stored inside the pavement body evaporates from the road surface, it absorbs heat of vaporization from the surface layer 1 and heat dissipation 5 is performed. Furthermore, the heat received by the road surface due to solar radiation or the like is transmitted underground through the roadbed 2 and the roadbed 3, and thermal diffusion 4 is performed. Due to the heat transfer, vaporization heat dissipation, heat diffusion, etc., an increase in the surface temperature of the road surface is effectively suppressed.

(Porous slag particles)
The aggregate in the pavement material of the present embodiment contains porous slag particles, silica stone and alumina particles, and the porous slag particles are preferably granulated blast furnace slag particles. Granulated blast furnace slag is obtained by quenching molten slag produced in a blast furnace with water, and has the form of porous particles containing vitreous particles. For example, the granulated blast furnace slag can be obtained by injecting pressurized water with a predetermined water pressure and water volume onto the molten blast furnace slag. By adjusting the pressure and amount of pressurized water, it is possible to produce hard and heavy hard granulated slag and porous and light soft granulated slag. In this embodiment, the latter soft granulated slag is preferably used. The porous slag particles are preferably particles having an outermost diameter of 10 mm or less, more preferably particles having an outermost diameter of 1 to 3 mm, in order to form a porous pavement structure. As the porous slag particles, for example , " granulated blast furnace slag" can be used.

(silica stone)
As the silica stone according to the present embodiment, crushed quartz schist containing mainly silicic acid (SiO ₂ ) as a main component is used. Those having a particle size of 10 mm or less can be used. The silica stone contained in the aggregate has a thermal conductivity of about 0.35 W/(m·K) and has the effect of increasing the thermal conductivity of the pavement material. As a result of this action, a pavement having high heat dissipation can be obtained, so that the effect of lowering the temperature can be obtained as described above. The content of silica stone in the aggregate is preferably 50% by mass or more. As silica stone, for example, silica stone produced in Kanuma, Tochigi Prefecture (manufactured by Awano Saiseki Co., Ltd.) and recycled silica stone manufactured by Nippon Light Metal Co., Ltd. may be used. Recycled silica stone has an average particle size of about 1.5 mm and a true specific gravity of about 2.6.

(alumina particles)
The alumina particles according to the present embodiment contain alumina (Al ₂ O ₃ ) as a main component, and particles having an average particle diameter within the range of 1.0 mm to 5.0 mm can be used. If the alumina content in the alumina particles is high, the thermal conductivity increases, so the alumina content in the alumina particles is preferably 90% or more, more preferably 95% or more, 99% or more. Alumina has a thermal conductivity of about 32 W/(m·K), which is much higher than silica stone. Therefore, it has the effect of greatly increasing the thermal conductivity of the pavement material, contributing to the provision of a pavement with high heat dissipation. If the content ratio of the alumina particles contained in the aggregate to the total amount of silica stone and alumina particles contained in the aggregate is less than 10%, the above effects of the alumina particles cannot be sufficiently obtained. Therefore, the content ratio of alumina particles is preferably 10 to 50%. More preferably, the upper limit of the content ratio is 40%, 30% or 20%.

As alumina particles, alumina particles having one particle size distribution range may be used. Alternatively, it may be a mixture of two types of alumina particles having different particle size distribution ranges. When the two types of alumina particles are used together, the content ratio of each alumina particle to silica stone is preferably 10 to 50%.

For the alumina particles according to the present embodiment, for example, "Nikkeirandom G1" manufactured by Nippon Light Metal Co., Ltd. can be used. The Nikkei random product is alumina particles obtained by melting an alumina raw material in an electric furnace, obtaining a solidified mass, pulverizing and sieving, and sieving. Alumina particles sized using a sieve with a mesh of 5 mm and a sieve with a mesh of 3 mm are called "5.0-3.0 mm product", and are sized using a sieve with a mesh of 3 mm and a sieve with a mesh of 1 mm. Alumina particles with a thickness of 3.0 to 1.0 mm are called "products of 3.0 to 1.0 mm." The true specific gravity of these alumina particles is 3.98.

The alumina particles of the Nikkei Random product have a chemical composition in mass% of Al ₂ O ₃ : 99.0% or more, Fe ₂ O ₃ : 0.1% or less, SiO ₂ : 0.1% or less, Na ₂ O: 0.4% or less. A typical chemical composition of a 5.0-3.0 mm product is Al ₂ O ₃ : 99.7%, Fe ₂ O ₃ : 0.01%, SiO ₂ : 0.05%, Na ₂ O: 0.05%. 22%. A typical chemical composition of a 3.0-1.0 mm product is Al ₂ O ₃ : 99.7%, Fe ₂ O ₃ : 0.02%, SiO ₂ : 0.05%, Na ₂ O: 0.05%. 18%.

According to the particle size distribution of the 5.0-3.0 mm product, 92.5% of the total falls within the range of 5.0 mm to 3.0 mm. 95.6% of all 3.0-1.0 mm products are in the range of 3.0 mm to 1.0 mm.

The pavement material according to this embodiment contains silica stone and alumina particles as thermally conductive substances. If the total amount of silica stone and alumina particles contained in the pavement material is less than 5% by mass, a sufficient temperature lowering effect cannot be obtained. On the other hand, if it exceeds 25% by mass, the occupancy ratio of the porous slag particles that form the void structure of the pavement material is reduced, which may reduce the water permeability and water retention effects of the pavement material. Therefore, the content of silica stone and alumina particles in the aggregate is preferably 5 to 25% by mass. The lower limit is more preferably 10% by mass, and the upper limit is more preferably 20% by mass.

(cement)
The ratio of cement to aggregate should be sufficient for it to function as a binder. For example, the porosity of the pavement as a whole can be increased by increasing the ratio of the aggregate to a mass ratio of 2 to 10 for the cement mass of 1.

(Admixture)
As the admixture to be added, for example, those conforming to JIS A 6204 "Chemical admixture for concrete" AE water reducing agent/standard type (I type) are preferably used. can be used. According to this kind of admixture, the unit water content of the concrete is reduced by the interaction between the dispersing action of the cement and the high-quality entrained air bubbles. The resistance to neutralization is improved, and the durability of concrete can be improved. The ratio of the admixture to be added to the pavement material according to the present embodiment may be, for example, 0.006 to 0.1 in mass ratio when the mass of cement is 1.

The pavement material according to this embodiment provides a pavement made of concrete. It is preferably applied to road surfaces such as sidewalks and parking lots.

Examples of the present invention will be described below. The present invention is not limited to the following examples, and can be implemented with appropriate modifications within the scope of the present invention.

(1) Production of pavement material As porous slag particles for the aggregate, granulated blast furnace slag from "East Japan Works, Keihin District, JFE Steel Company, Kawasaki City, Kanagawa Prefecture" is used, and silica stone is "Tochigi Silica stone with a particle size of 10 mm to 0 mm produced in Kanuma Prefecture was used, and as alumina particles, 5.0-3.0 mm products and 3.0-1.0 mm products of Nippon Light Metal Co., Ltd.'s "Nikkeirandom G1" were used. Ordinary Portland cement manufactured by Taiheiyo Cement Co., Ltd. was used as the cement, and "Master Pozzolith 78S" (manufactured by BASF Japan) was used as the admixture. Granulated blast furnace slag, silica, alumina particles, cement, admixture, and water were put into a mortar mixer in that order and mixed for 2 minutes to prepare paving materials of Examples 1 to 3. The mixing ratio of these raw materials is as shown in Table 1, which shows the ratio (parts by mass) when the whole aggregate is 100 parts by mass. The total blending amount of silica stone and alumina particles is constant at 14 parts by mass for 86 parts by mass of granulated blast furnace slag when the total aggregate is 100 parts by mass, and 5.0 parts by mass of alumina particles. The mixing ratio (% by mass) of the −3.0 mm product and the 3.0-1.0 mm product was changed as shown in Table 2 and prepared.

Comparative Example 1 shown in Table 2 is a coating material containing no silica stone, and Comparative Example 2 is a pavement material containing no alumina particles. Comparative Example 3 is a pavement material that does not contain alumina particles, and uses "recycled silica stone" manufactured by Nippon Light Metal Co., Ltd. as silica stone. Each paving material of Comparative Examples 1-3 was prepared according to the same procedure as Examples 1-3, except that silica stone or alumina particles were mixed.

(2) Measurement and evaluation of temperature change Using the pavement materials of Examples 1 to 3 and Comparative Examples 1 to 3, "Pavement Design Handbook" Chapter 7 (7-3-9) A test pavement was constructed according to "Concrete pavement" in "Pavement". A pavement for test was provided to a thickness of about 7 cm on a roadbed having a thickness of about 10 cm. Under the roadbed, a filter layer with a thickness of about 10 cm containing granulated slag and sand was provided. The filter layer and roadbed were finished to be flat with no camber formed in the center by a general construction method. The pavement for test was constructed by kneading the raw materials at a predetermined mixing ratio and spreading the mixture to a predetermined thickness. If the surface of the roadbed was dry, water was sprinkled to make it wet before construction. In addition, standard asphalt pavement was constructed with reclaimed dense-grade asphalt mixture to evaluate temperature change.

A thermocouple was attached to one location on the surface of the test pavement and connected to a data logger. During the daytime hours (6:00 to 17:59) from July to August 2017, the road surface temperature (° C.) of the test pavement and Alphalt was measured with a data logger using a thermocouple. Based on this measurement result, the road surface temperature every hour was averaged to find the average road surface temperature for each day of measurement (hereinafter also referred to as "average temperature"), and each of Examples 1 to 3 and Comparative Examples 1 to 3 was obtained. Average temperature of pavement with painted material and average temperature of standard asphalt pavement were obtained. Then, the difference between the average temperatures of both was calculated. In addition, we set up a box box at the place where these tests were conducted, and measured the temperature and precipitation on the measurement day.

Tables 3 and 4 show the measurement results in July and August 2017. The temperature difference from the asphalt pavement was shown by the numerical value obtained by subtracting the average temperature of the examples and comparative examples from the average temperature of the asphalt pavement. The "dry" column in these tables indicates the average temperature on the measurement day when precipitation was less than 1 mm on both the measurement day and the day before that, and the "wet" column indicates the precipitation on either the measurement day or the day before that Indicates the average temperature on the measurement days when the volume was 1 mm or more. In addition, the number of days of the measurement date corresponding to each was displayed.
)

As shown in Tables 3 and 4, in Examples 1 to 3 corresponding to the present invention, the average road surface temperature is lower than that of the asphalt pavement, and the degree of reduction in the average road surface temperature is about 3.5 to 3.5. It was 5.7°C. The extent of such temperature drop exceeded the results of Comparative Examples 1 to 3, which did not contain alumina particles. By blending alumina particles with excellent thermal conductivity into the pavement material containing porous slag particles and silica stone so that the content ratio of the alumina particles in the aggregate is 10 to 50%, the conventional pavement material is improved. In comparison, it showed the effect of further suppressing the rise of the road surface temperature. In this respect, it was confirmed that the pavement material according to the present invention has high heat dissipation.

Moreover, in Example 2, the temperature lowering effect was particularly large. Although not shown in the table, depending on the measurement date within the measurement period, the time when a decrease of about 10 to 20 ° C. was observed compared to the asphalt pavement in the wet state (wet) of Examples 1 to 3. There was also an obi.

1 surface layer 2 roadbed 3 roadbed 4 thermal diffusion 5 vaporization heat release 6 rainfall or sprinkled water 7 water retention 8 infiltration

Claims (2)

Aggregate containing porous slag particles, silica stone and alumina particles, cement, and an admixture, wherein the content ratio of the alumina particles in the total amount of the silica stone and the alumina particles contained in the aggregate is 10 to 10 50% by mass of pavement material ,
A pavement material, wherein the total amount of the silica stone and the alumina particles contained in the pavement material is 5 to 25% by mass in the pavement material . A method of manufacturing the pavement material of claim 1, comprising:
A process for producing pavement by mixing two products of alumina particles with different particle size distribution ranges.

Images