GB2142329A

GB2142329A - Road-surfacing material

Info

Publication number: GB2142329A
Application number: GB08411748A
Authority: GB
Inventors: Toetsu Yamato
Original assignee: Sato Road Co Ltd
Current assignee: Sato Road Co Ltd
Priority date: 1983-05-10
Filing date: 1984-05-09
Publication date: 1985-01-16
Also published as: DE3417024A1; GB2142329B; FR2545819B1; FR2545819A1; GB8411748D0; CA1239774A

Abstract

A concrete construction material e.g. for road surfaces having high water permeability and strength is obtained by using a concrete mixture composed of portland cement, an organic binder, water and an aggregate either having particle sizes in specified range, or an aggregate comprising sand and #7 macadam in a weight ratio of 5:95 to 20:80.

Description

SPECIFICATION Process of producing water-permeable cement concrete constructions Field of the Invention This invention relates to a process of producing water-permeable cement concrete constructions and, more particularly to cement concrete constructions having both good water-permeability and strength and suitable for use as, for example, road surfaces.

Background of the Invention A problem which has resulted in modern times from urbanisation is the reduction of rain water permeation into the ground which is caused by the spread of asphalt or concrete roads and pavements and buildings. There are several undesirable consequences of this inhibition of the natural permeation of rain water into the ground, which can occur. Thus, the water-table can fall, causing subsidence as well as environmental damage to living things, eg the growth of trees. On the other hand, the rapid run-off of rain water from impermeable surfaces often causes flooding of rivers during periods of heavy rain, with the risk of flooding to both urban areas and -farmland. These problems are now of major public concern.

Accordingly, there is a long felt need for the development of pavement and road surfaces which are water-permeabie. Water-permeable asphalt has been developed to meet this need but the available products are not always satisfactory, since the resulting asphalt surfaces are only relatively poorly water permeable but at the same time they are liable to melt in hot sun which causes clogging and a reduction in the water permeability whilst their strength changes with time.

lt.has hitherto been considered that a water-permeable concrete using cement concrete cannot form constructions of both sufficient water permeability and strength, and consequently a satisfactory water-permeable concrete has not previously been developed.

A road structure made by using a synthetic binder and an aggregate without using cement is known, as shown in Japanese Patent Publication No. 14,855/'78. However such a structure is unsuitable for practical use in cohstruction work, and moreover is costly. A process of producing a water-permeable concrete block composed of two concrete layers containing relatively fine macadam and relatively coarse macadam, respectively, is disclosed in Japanese Patent Publications (Unexamined) Nos. 10,620/'78 and 30,628/'78. However, these concrete blocks are not always satisfactory as regards their water permeability, and in any event are unsuitable for executing large scale construction works in situ.

As the result of our investigations we have discovered a cement concrete construction made of specific compounded materials which has both good water-permeability and strength properties which moreover do not quickly deteriorate. This discovery is utterly unexpected in view of that the production of a satisfactory water-permeable concrete has hitherto been considered to be difficult.

Summary of the Invention According to a first embodiment of this invention, there is provided a process of producing a water-permeable cement concrete construction, which is characterized by the use of a cement concrete mixture containing 300 to 400 kg of portland cement per m3 of the cement concrete mixture, 0.008 to 0.04 part by weight of a binder, per part by weight of the cement 0.3 to 0.45 part by weight of water per one part by weight of the cement, and an aggregate .comprising sand and #7 macadam in a weight ratio of 5:95 to 20:80.

The term "*7 macadam" as used herein refers to macadam which passes through a 5 mm sieve but does not pass through a 2.5 mm sieve. Also, the expression "per m3 of the cement concrete mixture" refers to the so-called theoretical density of the mixture calculated excluding the voids in the mixture.

According to a second embodiment of this invention, there is provided a process of producing a water permeable cement concrete construction, which is characterized by the use of a cement concrete mixture containing 300 to 400 kg of portland cement per m3 of the cement concrete mixture, 0.005 to 0.1 part by weight of a binder per one part by weight of the cement, 0.35 to 0.45 part by weight of water per one part by weight of the cement, and an aggregate; said aggregate having a particle size distribution such that the weight percentage of the particles passing through a 5 mm sieve is 50 to 100%, the weight percentage of the particles passing through a 2.5 mm sieve is 8 to 25% when the water/cement weight ratio if 0.35 to 0.43 or is O to 18% when the water/cement weight ratio is 0.43 (exclusive) to 0.45%, and the weight percentage of the particles passing through a 1.2 mm sieve is O to 6%.

Brief Description of the Drawing The accompanying figure is a graph showing the particle distributions of aggregates used in the Examples of this invention as well as in the Comparative Examples.

Detailed Description of the First Embodiment In the first embodiment of this invention, the sand/#7 macadam weight ratio in the aggregate sand and *7 macadam must be in the range from 5:95 to 20:80. As the proportion of sand is reduced, so the strength of the concrete tends to be reduced. However a sand/macadam weight ratio of 5:95 is suitable for a sidewall pavement, while a sand/macadam weight ratio of greater than 10:90 is usually employed for a light traffic road pavement.

When the weight ratio of sand/macadam is 15:85, a compressive strength a, of 11 5 kg/cm2 is typically obtained. On the other hand, if the proportion of sand is increased over the foregoing upper limit, the water permeability of the cement concrete construction becomes too low.

A part of the above-described aggregate can be replaced with #6 macadam (having particle sizes of 1 3 mm to 5 mm) in an amount of, preferably, 10 to 30% by weight. This modification is sometimes preferred inasmuch as the compressive strength increases to some extent (typically a7 = 1 25-140 kg/cm2), but on the other hand is accompanied by the disadvantage that the appearance of the concrete is less good owing to the presence of the larger #6 macadam together with the #7 macadam.

The amount of portland cement used in this invention is 300 to 400 kg, preferably 320 to 370 kg, per m3 of the whole cement concrete mixture including water. If the amount of the cement is over 400 kg, the strength of the concrete is increased but the water permeability thereof is reduced, which is unsuitable for the object of this invention. On the other hand, if the amount of the cement is less than 300 kg, the strength of the concrete becomes insufficient.

A binder is added to the cement mixture in an amount of 0.008 to 0.40 part by weight, preferably 0.015 to 0.03 part by weight, per one part by weight of the cement. As the binder, any binder which is conventionally known as an additive for cement mortar can be used in this invention. Examples of suitable binders which can be used in this invention are natural or synthetic rubbers such as styrene-butadiene rubber (SBR), nitrile-butadiene rubber (N BR), acrylic resins, epoxy resins, etc.

The binder is usually added as an emulsion thereof. The foregoing amount of the binder indicates the amount of the resin in the emulsion as solid component; When, for example, a commercially available SBR series latex binder (JSR Tomack Super, trade name, made by Japan Synthetic Rubber Co., Ltd.; solid component of 45%) is used in the above-described range, an improvement of the bending strength of about 10 to 60% has been obtained. If the binder is used over the above-described range, the water permeability of the concrete is reduced. Again, when an acrylic binder (X-5142, trade name, made by ACR Co., Ltd.) is used, an improvement of the bending strength of 60 to 90% has been obtained.In the case of using an epoxy series binder, the improvement of the bending strength of 20 to 40% has been obtained but there is a disadvantage that binders of the epoxy series do not generally show good workability.

The amount of water which is used in this invention is 0.30 to 0.45 part by weight, preferably 0.35 to 0.40 part by weight, per one part by weight of the portland cement. If the amount of water is over the upper limit, the water permeability of the concrete is reduced, while if the amount of water is below the lower limit, it becomes impossible to sufficiently knead the cement mixture.

In addition to the above-described essentiai components in this invention, other additives conventionally added to the cement concrete, such as red oxide for coloring, etc., can be added thereto, for example in an amount of 3 to 5%.

The cement concrete construction which can be made according to this invention include, in general, cement concrete constructions which are required to have water permeability, such as pavements for sidewalks, parking places, etc., permeable concrete layers constructed under top soil for improving drainage, and pre-cast blocks used for the aforesaid purposes.

A feature of the water-permeable cement concrete constructions produced by the process of this invention is their relatively large void content. For example, a water permeable cement concrete construction having a voidage of 10 to 30%, preferably 1 5 to 25%, can be obtained according to the process of this invention. Therefore, a cement concrete construction of this invention is generally superior to a water-permeable asphalt pavement in that the cement concrete of this invention temporarily retains water in the voids and thereafter the water permeates very quickly through the concrete. Moreover, water permeable cement concrete constructions produced by the process of this invention have the advantages, as compared with water permeable asphalt pavements, of having a low risk of clogging, low loss of strength and water permeability with the passage of time, and of not melting in sunlight. Still further, particles of earth and sand carried by eg shoes and tires of cars, onto the surface of the cement concrete constructions of this invention, tend to be washed away through the voids of the concrete by rain, and hence the surfaces remain clearer.

As to the degree of water permeability, a water permeable cement concrete construction having a water permeability coefficient of the order of 10-1 to 10-4 cm/sec., typically the order of 10-' to 10-3 cm/sec., can be obtained by the process of this invention. A voidage of 20% corresponds to a water permeability coefficient of the order of 10 - t cm/sec. and a voidage of 1 5% corresponds to a water permeability coefficient of the order of 10-2 cm/sec.

It must be especially mentioned that water permeable cement concrete constructions obtainable by the process of this invention can have a sufficient strength for enduring practical use while still exhibiting the large voidage and good water permeability described above. For example, a water permeable cement concrete pavement having a compressive strength of 200 to 300 kg/cm2 (4 weeks strength, cured in water maintained at 20"C) and a bending strength of 20 to 30 kg/cm2 (4 weeks strength, cured in water maintained at 20"C) can be obtained.

A preferred compounding ratio for the cement concrete mixture of this invention is as follows: weight ratio of sand: &num;7 macadam: 15:85; clement: 350 kg/m3; binder: 0.04 part by weight as a 45% emulsion, based on the cement; and water: 0.4 part by weight including water contained in the emulsion, based on the cement.

Detailed Description of the Second Embodiment In this embodiment, the water/cement weight ratio must be 0.35 to 0.45. When the water/cement weight ratio is 0.35 to 0.43 an aggregate must be used which has a particle size distribution such that the weight percentage of the particles passing through a 5 mm sieve is 50 to 100%, preferably 75 to 100%, the weight percentage of the particles passing through a 2.5 mm sieve is 8 to 25% preferably 8 to 18%, and the weight percentage of the particles passing through a 1.2 mm sieve is 0 to 6%.When the water/cement weight ratio is 0.43 (exclusive) to 0.45, the particle size distribution is such that the weight percentage of the particles passing through a 5 mm sieve is 50 to 100%, preferably 75 to 100%, the weight percentage of the particles passing through a 2.5 mm sieve is 0 to 18%, preferably 5 to 15%, and the weight percentage of the particles passing through a 1.2 mm sieve is 0 to 6%. The aggregate which is used in this invention may contain larger macadam, although the presence of the larger macadam reduces the appearance of the cement concrete product. It is preferred in this embodiment of this invention that the weight percentage of particles passing through a 0.6 mm sieve be 0 to 3%.The sieve sizes referred to in this specification are nominal sizes.

In this embodiment of this invention, by employing an aggregate having the particle size distribution as very strictly defined above, and a water/cement weight ratio as described above, a water permeability coefficient of the order as high as 10-' to 100 cm/sec. can be obtained whilst a sufficiently high strength can be imparted to the cement concrete. Considering that a cpncrete having a water permeability coefficient of the order of 10- 1 to 100 cm/sec. has not hitherto been known, it is astonishing that a cement concrete construction having these desirable properties can be obtained using materials already known in cement concrete mixtures.

Moreover, the excellent water permeability and the strength properties are well maintained with the passage of time.

The lower limit of the particle size (the percentage of particles passing through each sieve) of the aggregate is determined mainly by the requirement for water permeability. In order to obtain high water permeability of the cement concrete construction, it is necessary to strictly control the proportion of the macadam having fine particle sizes. Since macadam conventionally contains a considerable amount of fine sands in addition to macadam within the nominal particle size ranges, for the purposes of determining the particle size range in the second embodiment of this invention, it is necessary to include these sands in the calculation. Accordingly, it is necessary to previously determine the proportion of the fine sands by separating the fine sands by washing the macadam and measuring the amount of the fine sands thus separated.

On the other hand, the upper limit of the particle size range (the percentage of particles passing through each sieve) of the aggregate is determined mainly by the strength requirement for the cement concrete construction. From the viewpoint of practical use, it is advantageous to obtain a 4 weeks bending strength 28 (cured in water kept at 20"C), of higher than 20 kg/cm2, preferably higher than 25 kg/cm2, while attaining also a high water permeability.

The amount of the portland cement in the second embodiment of the process of this invention is 300 to 400 kg, preferably 320 to 370 kg, per m3 of the whole cement concrete mixture. If the amount of the cement is larger than 400 kg, the strength is increased but the water permeability is reduced, which is unsuitable for the object of this invention. On the other hand, if the amount of the cement is less than 300 kg, the strength becomes insufficient.

Furthermore, in this embodiment, a binder is added to the cement concrete mixture in an amount of 0.005 to 0.1 by weight, preferably 0.008 to 0.04 part by weight, per one part by weight of the cement. Suitable binders are those already described in relation to the first embodiment of this invention.

The proportion of water in this embodiment of the invention is 0.35 to 0.45 part by weight per one part by weight of the cement. If water is used over the upper limit, the water permeability of the cement concrete is reduced, while if water is below the lower limit, it becomes difficult to knead the mixture sufficiently.

The water-permeable cement concrete construction produced by the second embodiment of the process of this invention thus not only has adequate strength but also a sufficiently large voidage and an excellent water permeability. In preferred instances, a water permeable cement concrete pavement having a bending strength of higher than 25 kg/cm2 (4 weeks strength, cured in water kept at 20 ) is obtained. The surfaces produced by the process of this invention can be used for construction of sidewalks, parking places, playgrounds, etc., as well as for roads to carry light traffic.

In both embodiments of this invention, water-permeable cement concrete constructions can be obtained by first kneading the specified components, in the specified amounts, whereafter the resulting cement concrete mixture is cast into the desired form and hardened or allowed to harden.

The application of the invention to the construction of pavements will now be dealt with by way of example.

It is first necessary to determine the required depth of the cement concrete pavement in consideration of the anticipated rainfall, rain strength, load applied to the surface of the pavement, water retaining faculty of the pavement, supporting pwer of the roadbed, water permeability of the roadbed, etc. In general, the depth of the pavement should be about 10 cm for a sidewalk, about 1 5 cm for parking places and playfields, and about 1 5 cm to about 20 cm for light traffic roads. Also, for reinforcing the pavement, ropes having high tensile strength (e.g.

glass fiber nets) may be installed if desired during the construction.

In order to form a water-permeable cement concrete pavement construction according to this invention, the above described cement concrete mixture would normally be mixed in a concrete plant equipped with conventional mixing installations, transported to the site by means of a truck mixer or a damp truck, and there spread uniformly and flatly on the surface of the road or the roadbed at the required thickness by means of a finisher.

The invention will be further explained by the following examples.

Examples 1 and 2 and Comparison Examples 1 and 2.

Using each of the aggregates having the particle size distributions shown in Table 1, each cement concrete mixture composed of 350 kg of portland cement per m3 (theoretical) of the cement concrete mixture, 132.3 kg (excluding water contained in the following emulsion) of water, and 14 kg of a binder emulsion (JSR Tomack Super, solid content 6.3 kg), the rest being the aggregate, was kneaded and after casting the mixture, the mixture thus formed was hardened. In each case the water/cement weight ratio of 0.40. The water permeability coefficient and the 4 weeks bending strength of each hardened product are shown in Table 1.

Table 1

Weight % of macadam (A) (B) (C) \ passing through sieve \ 13 mm 5 Sin 2.5 mn 1.2tiin \ Example 1 100 85 15 4 0.40 8x10.1 26.3 Canparison Ixample 1 100 85 4 4 0.40 8.5xlO-1 19.0 Example 2 100 85 20 4 0.40 1,3x10-1 28.8 Cbnparison Example 2 100 85 20 15 0.40 9.1x10-3 30.5 (A): Water/cement weight ratio (B): Water permeability coefficient (cm/sec) (C):Bending strength (kg/cm2) As is clear from the results shown in Table 1, the samples in Examples 1 and 2 show an excellent water permeability coefficient and bending strength but the samples in Comparison Examples 1 and 2 are inferior in bending strength and/or water permeability.

Example 3 and Comparison Example 3.

Using each of the aggregate having the particle size distribution shown in Table 2, each cement concrete mixture composed of 350 kg of portland cement per m3 (theoretical) of the cement concrete mixture and 148.8 kg of water (excluding water contained in the following binder emulsion) and 1 5.8 kg of a binder emulsion (solid component 7.1 kg), the rest being the aggregate, was kneaded, cast, and hardened. Thus, the water/cement weight ratio was 0.45 in each case. The water permeability co-efficient and the 4 weeks bending strength of each hardened sample are shown in Table 2.

Table 2

Weigt%ofnicadam (A) (B) (C) passing through sieve 13iirn Sin 2.Sin 1.2in 5 5 F*awple 3 100 85 10 4 / 0.45 4.5xlO 1 27.0 Comparison Example 3 100 85 25 4 0.45 1.5x10 32.0 (A), (B) and (C) in Table 2 have the same meaning as in Table 1.

As is clear from the results shown in Table 2, the sample in Example 3 has an excellent water permeable coefficient and bending strength as compared with the sample in Comparison Example 3.

Claims

1. A process of producing a water-permeable cement concrete construction, which is characterized by the use of a cement concrete mixture containing 300 to 400 kg of portland cement per m3 of the cement concrete mixture, 0.008 to 0.04 part by weight of a binder, per part by weight of the cement 0.3 to 0.45 part by weight of water per one part by weight of the cement, and an aggregate comprising sand and #7 macadam in a weight ratio of 5:95 to 20:80.

2. A process as claimed in Claim 1, wherein the weight ratio of sand to #7 madacam is from 10:90 to 15:85.

3. A process as claimed in Claim 1 or Claim 2, wherein the proportion of the binder in the cement concrete mixture is 0.015 to 0.03 part by weight per one part by weight of the cement.

4. A process as claimed in any preceding claim, wherein the proportion of water in the cement concrete mixture is 0.35 to 0.40 part by weight per one part by weight of the cement.

5. A process as claimed in any preceding claim, wherein the proportion of portland cement is 320 to 370 kg per m3 of the cement concrete mixture.

6. A modification of the process as claimed in any preceding claim, wherein a proportion of #7 macadam is replaced with #6 macadam.

7. A process of producing a water permeable cement concrete construction, which is characterized by the use of a cement concrete mixture containing 300 to 400 kg of portland cement per m3 of the cement concrete mixture, 0.005 to 0.1 part by weight of a binder per one part by weight of the cement, 0.35 to 0.45 part by weight of water per one part by weight of the cement, and an aggregate; said aggregate having a particle size distribution such that the weight percentage of the particles passing through a 5 mm sieve is 50 to 100%, the weight percentage of the particles passing through a 2.5 mm sieve is 8 to 25% when the water/cement weight ratio is 0.35 to 0.43 or is 0 to 18% when the water/cement weight ratio is 0.43 (exclusive) to 0.45%, and the weight percentage of the particles passing through a 1.2 mm sieve is 0 to 6%.

8. A process as claimed in Claim 7, wherein the weight percentage of the aggregate passing through a 0.6 mm sieve is 0 to 3%.

9. A process as claimed in Claim 7 or Claim 8, wherein the proportion of the binder in the cement concrete mixture is 0.015 to 0.03 part by weight per one part by weight of the cement.

10. A process as claimed in any one of Claims 7-9, wherein the proportion of the cement in the cement concrete mixture is 320 to 370 kg per m3 of the mixture.

11. A process of producing a water-permeable cement concrete construction substantially as hereinbefore described.