JP2005163484A - Pavement body - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pavement body which has drainage property or water permeability and water retentivity without use of a particular material used in a conventional water-retentive pavement. <P>SOLUTION: The pavement body is provided cured at a percentage of void of 5-30% which consists of porous concrete containing an alkali reactive aggregate as a coarse aggregate. Preferably, the coarse aggregate contains the alkali reactive aggregate of 10 wt.% and an alkali amount of the porous concrete should be 3.0-10 kg/m<SP>3</SP>. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a pavement having both drainage or water permeability and water retention.

  Ensuring drainage of streets during rainfall is an extremely important issue from the perspective of preventing urban flooding and securing groundwater. For such problems, conventionally, a water-permeable pavement that permeates rainwater from the pavement surface to the roadbed and roadbed to ensure drainage of the street, and a surface layer having a water-permeable function on a base layer having a water-impermeable function, Drainage pavement that absorbs rainwater that has fallen on the pavement surface by the surface layer and drains it from the drainage groove provided at the end without penetrating into the base layer or roadbed is used.

  However, according to such a water-permeable pavement and drainage pavement, rain water at the time of rain will permeate the roadbed, or it will be almost completely drained from the pavement surface layer and drainage ditch, There is a problem that it is impossible to suppress the heat island phenomenon of a city that has become serious in recent years.

  Therefore, for the purpose of demonstrating the drainage or water permeability function during rainfall and also suppressing the heat island phenomenon, for example, concrete prepared by mortar using pulverized lightweight cellular concrete waste and agglomerating with gravel as the core A method (Patent Document 1) that spreads the water and a method (Patent Document 2) that uses a water-retaining mortar containing mineral fibers and plant fibers to form a water-permeable paving body are disclosed.

JP-A-11-158804 JP 2003-74005 A

  However, such a conventional water-retaining pavement has to use a special material such as a pulverized material or fiber of lightweight cellular concrete waste material, and there is a problem that the pavement becomes expensive. Moreover, since special work for preparing these special materials or kneading into concrete is required, there is a problem that the construction process becomes complicated.

  The present invention has been made in view of such problems of the prior art, and it is an object of the present invention to provide a pavement that combines drainage or water permeability and water retention without using a special material. It is an issue.

  In view of the above problems, the present invention provides a pavement formed by hardening porous concrete containing an alkali-reactive aggregate as a coarse aggregate with a porosity of 5 to 30%.

The pavement of the present invention may contain 10% by weight of the coarse aggregate, preferably alkali-reactive aggregate.
In the pavement of the present invention, the porous concrete preferably has an alkali amount of 3.0 to 10 kg / m ³ .

  According to the pavement according to the present invention, it is possible to provide a pavement having both drainage or water permeability and water retention without using a special material, and surface water that accumulates on the road surface during rainfall. Can be quickly eliminated, and water can be stored inside the pavement to suppress the heat island phenomenon.

  Hereinafter, a preferable embodiment of the pavement according to the present invention will be described.

The pavement of the present invention is a pavement formed by hardening porous concrete, and an alkali-reactive aggregate is used as the coarse aggregate constituting the porous concrete.
As the alkali-reactive aggregate, an aggregate that can react with an alkali component such as Na ₂ O or K ₂ O contained in concrete to generate a gel reactive with water is preferable. Means an aggregate belonging to the category B of alkali silica reactivity defined in JIS A 5308 Annex 1 “Aggregates for Ready-Mixed Concrete”.

The alkali silica reactivity category is:
In both tests of JIS A 5308 Annex 7 “Aggregate Alkali Silica Reactivity Test Method (Chemical Method)” and JIS A 5308 Annex 8 “Aggregate Alkali Silica Reactivity Test Method (Mortar Bar Method)” , “Class B” is determined as “not harmless”.

Usually, when gel is generated by such an alkali aggregate reaction, the gel expands due to a reaction with water, and in some cases, the concrete is cracked to cause deterioration of the concrete. ing.
However, since the pavement according to the present invention is formed by curing porous concrete having voids, stress due to expansion is relieved by the voids, and cracks as in general concrete do not occur.

The coarse aggregate used for the porous concrete preferably contains 10% by weight or more of the alkali-reactive aggregate as described above.
By setting the content of the alkali-reactive aggregate in the coarse aggregate to 10% by weight or more, the amount of gel generated by the alkali-aggregate reaction is increased, and the water retention is further improved.
There is no particular upper limit to the content of the alkali-reactive aggregate, and the total amount of the coarse aggregate can be used as the alkali-reactive aggregate.

The alkali amount of the porous concrete is preferably 3.0 kg / m ³ or more, more preferably 5.0 kg / m ³ or more in terms of Na ₂ O. When the alkali amount is 3.0 kg / m ³ or more in terms of Na ₂ O, the alkali aggregate reaction with the aggregate is promoted, and the pavement has excellent water retention. Further, if 5.0 kg / m ³ or more in terms of Na ₂ O, can be further increased water retention. However, it is preferable that the upper limit of the alkali amount is 10 kg / m ^{3 in} terms of Na ₂ O from the viewpoint of suppressing a decrease in long-term strength and easily securing a suitable strength as a paving body.

When the amount of alkali contained in the cement is small, an alkali adjuster may be added to the porous concrete to adjust the amount of alkali.
As alkali adjusters, use sodium salts such as sodium chloride, sodium hydroxide, sodium carbonate, sodium nitrate, and sodium sulfate, or potassium salts such as potassium chloride, potassium hydroxide, potassium carbonate, potassium nitrate, and potassium sulfate. Can do.

  In the present invention, the amount of alkali in the concrete is measured according to JIS R 5202 “Chemical analysis method for Portland cement”.

  Although it does not specifically limit as cement which comprises porous concrete, The thing which does not suppress alkali-aggregate reaction is preferable. Examples of cements that do not suppress alkali-aggregate reaction include normal, early strength, ultra-early strength, white, sulfate-resistant, medium heat, low heat and other portland cements, jet cements, alumina cements and other special cements. be able to. On the other hand, as cement which suppresses alkali-aggregate reaction, the mixed cement formed by mixing blast furnace slag and fly ash with Portland cement can be mentioned, and these are not preferable in the present invention.

  Moreover, various admixtures can be used for the said porous concrete in the range which does not inhibit the effect of this invention. However, admixtures such as blast furnace slag fine powder, fly ash, silica fume and the like have an effect of inhibiting the alkali aggregate reaction, and are therefore preferably not used for the porous concrete constituting the pavement of the present invention.

  Furthermore, it is preferable to add a water reducing agent such as a high performance AE water reducing agent or an AE water reducing agent to the porous concrete from the viewpoint of securing a desired void by reducing the water cement ratio.

Formulation of such porous concrete is not particularly limited, for example, the unit amount of water ^{40~150kg / m 3, 200~500kg / m} 3 of unit amount of cement, the unit amount of coarse aggregate 1300~1700kg / m ³ And 0 to 5 parts by weight of the water reducing agent may be added to 100 parts by weight of cement.

The porosity of the pavement is 5 to 30%, preferably 7% or more. If the porosity is 5% or more, not only is water permeability or drainage excellent, but also concrete relaxation due to alkali-aggregate reaction can be mitigated and cracking of the pavement can be prevented.
Further, from the viewpoint of ensuring the strength as a paved body, the upper limit of the porosity is 30%, preferably 25%.

  Next, the present invention will be described more specifically with reference to examples and comparative examples.

(Example 1)
And coarse aggregate 1549kg / m ³ consisting of No. 6 crushed stone 95 wt% belonging to No. 6 crushed stone 5 wt% and section A belonging to the section B, the water 119kg / m ^3, ordinary Portland cement 476kg / m ^3, the cement 1% by weight of a high-performance AE water reducing agent (manufactured by Kao Corporation, Mighty 3000S) was kneaded, and sodium chloride was further added to prepare porous concrete having an alkali amount of 6 kg / m ³ . A cylindrical specimen (size: diameter 10 cm × height 20 cm, porosity: about 15%) was prepared using the porous concrete, and was cured for 6 months under conditions of a temperature of 40 ° C. and a humidity of 100% RH.

(Example 2)
A specimen was prepared in the same manner as in Example 1 except that the aggregate of category B was 10% by weight and the aggregate of category A was 90% by weight.

(Example 3)
A specimen was prepared in the same manner as in Example 1 except that the aggregate of category B was 50% by weight and the aggregate of category A was 50% by weight.

Example 4
A specimen was prepared in the same manner as in Example 1 except that the aggregate of category B was 100% by weight and the aggregate of category A was 0% by weight.

(Example 5)
A specimen was prepared in the same manner as in Example 4 except that the alkali amount was 2.8 kg / m ³ .

(Example 6)
A specimen was prepared in the same manner as in Example 4 except that the alkali amount was 3.5 kg / m ³ .

(Comparative Example 1)
A specimen was prepared in the same manner as in Example 1 except that the aggregate of category A was 100% by weight and the aggregate of category B was not used.

The following tests were performed using the specimens of Examples and Comparative Examples.
Permeability Test Pavement Test Method Handbook 5-3-5 “Permeability test method for water-permeable asphalt mixture” was used to measure the water permeability coefficient.
The water absorption test specimen is placed in a curing room (temperature 20 ° C., humidity 95% RH) for 3 days, further placed in a constant humidity and temperature controlled room (temperature 20 ° C., humidity 60% RH) for 7 days, and then dried. The specimen is placed on a sponge mat placed at 0.5 cm (that is, 0.5 cm of the lower end of the specimen is immersed in water). In this state, the time required for the specimen to absorb 5 cm of water (5 cm suction time) and the value obtained by dividing the volume of water sucked by the specimen after leaving for 12 hours by the volume of the specimen (maximum water absorption rate) ) Was calculated.
The results are shown in Table 1 below.

  As shown in Table 1, the pavement of the comparative example has the same excellent water permeability as that of the example, but because no reactive aggregate is used, a gel due to the alkali aggregate reaction is generated. It can be seen that the maximum water absorption is low, that is, the water retention is poor. On the other hand, it can be seen that the pavement of the example has both water permeability and water retention.

Next, the influence of the porosity was examined.
(Example 7)
Porous concrete was prepared in the same manner as in Example 4 except that 234 kg / m ³ of Sasakawa-produced river sand was added as a fine aggregate to adjust the porosity, and a specimen having a porosity of 6% was prepared.

(Example 8)
Porous concrete was prepared in the same manner as in Example 4 except that 182 kg / m ³ of Sasakawa-produced river sand was added as a fine aggregate to adjust the porosity, and a specimen having a porosity of 8% was prepared.

(Comparative Example 2)
Porous concrete was prepared in the same manner as in Example 4 except that 338 kg / m ³ of Yodogawa sand was added as fine aggregate to adjust the porosity, and a specimen having a porosity of 2% was prepared.

(Comparative Example 3)
Porous concrete was prepared in the same manner as in Example 4 except that 338 kg / m ³ of Sasakawa-produced river sand was added as a fine aggregate to adjust the porosity, and a specimen having a porosity of 4% was prepared.

Measurement of expansion amount The expansion amount of the specimen was measured based on JCI-AAR-3-1987 "Testing method for alkali-silica reactivity of concrete (draft)".
The results are shown in Table 2 below.

As shown in Table 2, in Comparative Examples 2 and 3 in which the porosity is less than 5%, the expansion pressure due to water absorption of the gel generated by the alkali aggregate reaction is not relaxed because the porosity is small, and the specimen is Cracks occurred.
On the other hand, in Examples 7 and 8 having a porosity of 5% or more, the expansion pressure due to water absorption of the gel was relieved by the voids, so that no cracks occurred in the specimen.

Claims (3)

  A pavement formed by hardening porous concrete containing an alkali-reactive aggregate as a coarse aggregate in a state where the porosity is 5 to 30%.   The pavement according to claim 1, wherein the coarse aggregate contains 10% by weight or more of alkali-reactive aggregate. The pavement according to claim 1 or 2, wherein the porous concrete has an alkali amount of 3.0 to 10 kg / m ³ .