JP7596396B2 - Cold asphalt mixture - Google Patents

Description

The present invention relates to cold asphalt mixtures used for road paving, etc.

Conventionally, cold asphalt mixtures that can be applied at room temperature at the construction site have been used for temporary restoration of paved roads following construction work to excavate buried pipes under roads, and for repairing locally damaged areas of existing paved roads. This type of cold asphalt mixture has the advantage that it can be packed in bags, spread evenly at room temperature at the construction site, and compacted, but it has the problem that it is less durable than normal heated asphalt mixtures and cannot be used for long periods of time. In particular, this cold asphalt mixture can only be used for a short period of time in construction locations with heavy traffic, on paved surfaces that are subject to repeated vibrations, and on paved surfaces on decks that have a large amount of deflection.

To solve the above problems, cold asphalt mixtures have been developed in recent years that use reactive substances to develop strength in a short time. Such cold asphalt mixtures are composed of at least aggregate (e.g., crushed stone, crushed sand, fine sand, stone powder, etc.), asphalt, a lubricating solidifier (fatty acid and/or fatty acid dimer and/or fatty acid trimer), and an alkaline additive (cement), and various proposals have been made to improve the strength, durability, and deflection compliance of the pavement constructed using these mixtures.

For example, Patent Document 1 proposes the use of a lubricating solidifying material containing 1 to 15% by weight of palmitic acid, 0.3 to 10% by weight of stearic acid, 39 to 59% by weight of oleic acid, 20 to 48% by weight of linoleic acid, and 1 to 15% by weight of linolenic acid.

Furthermore, Patent Document 2 proposes using a lubricating solidification material containing 50 to 100% by weight of saturated fatty acids having 6 to 30 carbon atoms.

Furthermore, Patent Document 3 proposes using an organic acid polymer with two or more carboxyl and/or sulfo groups in its side chains, and a reactive resin material containing at least divalent metal ions as an alkaline additive (cement). With this room temperature asphalt mixture, the reactive resin material and the alkaline additive undergo a crosslinking and/or polymerization reaction upon addition of water to form an ionomer, which imparts strength and deflection compliance to the pavement.

Furthermore, Patent Document 4 proposes using a fatty acid containing oleic acid and linoleic acid, with the linoleic acid content being set to a value greater than 50% by weight relative to the total weight of the oleic acid and linoleic acid.

Patent No. 5916937 Patent No. 6089139 Patent No. 6344873 Patent No. 6458194

However, the room temperature asphalt mixtures proposed in Patent Documents 1 to 4 do not necessarily have a good balance of flow resistance, aggregate scattering resistance, deflection tracking, and workability at low temperatures, and they also have the problem that the property improvers are expensive. For example, the property improver proposed in Patent Document 4, which is a petroleum lubricant-based liquid, is more expensive than fatty acid pitch, an industrial by-product in the manufacture of fatty acids. For this reason, room temperature asphalt mixtures that contain such expensive property improvers have problems in terms of economics.

The present invention has been made in consideration of the above problems, and its purpose is to provide an ambient temperature asphalt mixture that is excellent in terms of balance between flow resistance, aggregate scattering resistance, deflection tracking ability and low-temperature workability, as well as being economical.

In order to achieve the above-mentioned object, the present invention provides a room temperature asphalt mixture comprising at least aggregate, asphalt, a property improver which is an oily component derived from plants, a lubricant solidifier (fatty acid and/or fatty acid dimer and/or fatty acid trimer) and cement, characterized in that the ratio of the property improver to the lubricant solidifier is set in the range of 40:60 to 5:95.

Here, recycled aggregate may be further mixed into the above-mentioned room temperature asphalt mixture.

It is also desirable that the property improving agent be a fatty acid pitch.

According to the present invention, it has been experimentally confirmed that by setting the ratio of property improver:lubricating solidifier in the range of 40:60 to 5:95, a good balance is achieved between the flow resistance, aggregate scattering resistance, deflection tracking, and low-temperature workability of the room temperature asphalt mixture. In addition, by using inexpensive fatty acid pitch, an industrial by-product of fatty acid production, as the property improver, the cost of the room temperature asphalt mixture is kept low, making it economical.

The following describes an embodiment of the present invention.

The cold asphalt mixture of the present invention is a repair material that hardens when water is poured onto it at room temperature to form an asphalt pavement, and is basically composed of a mixture of aggregate, a property improver that is an oily component derived from plants, a lubricating solidifier, and cement. An example of the mixing ratio of the various substances that make up this cold asphalt mixture is shown in Table 1.

表１に示すように、本実施の形態に係るアスファルト混合物に含まれる骨材には、７号砕石（最大粒径５ｍｍ）が４３．０％、砕砂が２４．０％、細砂が２８．０％、石粉が５．０％の割合で使用される。なお、骨材には、既設舗装の種類に応じて６号砕石（最大粒径１３ｍｍ）や５号砕石（最大粒径２０ｍｍ）などを用いて粒度調整することができる。

As shown in Table 1, the aggregates contained in the asphalt mixture according to this embodiment are 43.0% No. 7 crushed stone (maximum particle size 5 mm), 24.0% crushed sand, 28.0% fine sand, and 5.0% stone powder. The aggregates can be adjusted in particle size by using No. 6 crushed stone (maximum particle size 13 mm) or No. 5 crushed stone (maximum particle size 20 mm) depending on the type of existing pavement.

As shown in Table 1, the fatty acid as a lubrication solidifier and the fatty acid pitch as a property improver constitute the plasticizer mixture, and this fatty acid mixture and asphalt constitute the binder. The blending ratio of asphalt in the binder is set to 56.1%, and the blending ratio of the plasticizer mixture is set to 43.90%. The plasticizer mixture contains fatty acid and fatty acid pitch as a property improver . Here, the fatty acid does not contain pitch because it is produced as the target product.

Asphalt used is straight asphalt (St. Asphalt 60/80). When selecting asphalt, appropriate asphalt can be selected taking into consideration aggregate peelability, etc. In addition, decolorized asphalt can also be used depending on the conditions of the construction site.

In addition, ordinary cement is used as an externally added alkaline additive.

The mixing ratios of each mixture are shown in Table 1, where the total of the various mixtures excluding the cement as an external additive is taken as 100%, with the mixing ratios of No. 7 crushed stone, crushed sand, fine sand, and stone powder in the aggregate being 40.2%, 22.4%, 26.2%, and 4.7%, respectively. The binder mixing ratio is 6.5%, with 3.65% asphalt, 2.14% lubricating solidifier, and 0.71% property improver. In this case, 0.8% cement is added externally.

As mentioned above, the plasticizer mixture contains a lubricant solidifier and a property improver. The types and mixing ratios of the lubricant solidifier and property improver are shown in Table 2.

本実施の形態では、脂肪酸として築野食品工業（株）社製のＴＦＡ－１４５ＷＦ（型番）を使用した。また、本実施の形態では、性状改善剤として植物由来の油状成分である脂肪酸ピッチを使用した。この脂肪酸ピッチは、脂肪酸製造における工業副産物（残渣）である。なお、本実施の形態では、脂肪酸ピッチとして特別に検討したもの（表２においては、形式的に「ＴＦＡ－Ｂ６０」と表示した）を使用した。

In this embodiment, TFA-145WF (model number) manufactured by Tsuno Foods Industries Co., Ltd. was used as the fatty acid. Also, in this embodiment, fatty acid pitch, which is an oily component derived from plants, was used as the property improving agent. This fatty acid pitch is an industrial by-product (residue) in the production of fatty acids. Note that in this embodiment, a specially investigated fatty acid pitch (formally indicated as "TFA-B60" in Table 2) was used.

In this embodiment, the ratio of fatty acid pitch to fatty acid in the room temperature asphalt mixture is set to 25:75 (shown as "Example 1" in Table 2). In Table 2, "Comparative Example 1" refers to a case where 100% fatty acid (TFA-145WF) is used without using any property improver, and "Comparative Example 2" refers to a case where mineral oil (aromatic type) is used as a property improver, specifically Risei Cool Super (product name), a recycling additive manufactured by Santoku Shoji Co., Ltd., and the fatty acid:mineral oil ratio is set to 75:25. "Comparative Example 3" refers to a case where vegetable oil (recycled waste edible oil) is used as a property improver and the fatty acid:vegetable oil ratio is set to 75:25.

The fatty acid pitch used as a property improver in the cold asphalt mixture of this embodiment ("Example 1" in Table 2) is an industrial by-product (residue) and is therefore less expensive than the mineral oil that has traditionally been used, making it economical. It also has advantages as a biomass material over petroleum-derived materials (e.g., a renewable resource and the saving of petroleum resources). In terms of properties, the cold asphalt mixture can ensure high fluidity resistance, aggregate scattering resistance, and deflection tracking, while also improving low-temperature workability, and it has been demonstrated in various tests described below that a good balance between these is maintained.

Below, we explain the evaluation of the room temperature asphalt mixture of this embodiment ("Example 1" in Table 2) in comparison with Comparative Examples 1 to 3 in Table 2.

Here, an evaluation summary is shown in Table 3.

表３に示すように、評価は下記の４項目についてそれぞれ行われた。

As shown in Table 3, the evaluation was carried out on the following four items.

1) Ease of use:
The pour point of the plasticizer component is one of the test items for workability during use. The test was carried out by air-cooling a 50g sample from 12.5 to -17.5°C in 2.5°C increments and checking the presence or absence of fluidity at each temperature. In this case, the pour point was determined as the temperature just before the temperature at which fluidity was lost. If the temperature was -10°C or lower, the pour point was judged as ○ (good), if it was -10 to 0°C, the pour point was judged as △ (passable), and if it was 0°C or higher, the pour point was judged as × (unacceptable).

2) Deflection followability:
A bending test is one of the test items for the deflection follow-up property, and this bending test was performed by preparing a specimen by spraying water at a temperature of 20° C., curing this specimen for 7 days at a temperature of 20° C., and testing at a temperature of -10° C. As a result of this bending test, if (bending strain×10 ⁻³ ) was 4 or more, it was judged as ○ (good), if it was 3 to 4, it was judged as △ (passable), and if it was less than 3, it was judged as × (unacceptable).

3) Aggregate scattering resistance:
One test item for aggregate scattering resistance is the 20°C Cantabro test, in which water is sprayed at 20°C, the concrete is pressed 50 times on both sides, and after demolding, the concrete is cured for 24 hours at 20°C, and then the test is performed at 20°C. As a result of the 20°C Cantabro test, if the loss rate is less than 10%, it is judged as ○ (good), if it is 10-20%, it is △ (passable), and if it is 20% or more, it is judged as × (unacceptable).

4) Resistance to fluidity:
A test item for fluidity resistance is a wheel tracking test, in which a test specimen was prepared by spraying water at a temperature of 20° C. on the specimen, which was then cured for 7 days at a temperature of 20° C., and then tested at a temperature of 60° C. As a result of the wheel tracking test, if the dynamic stability was 3000 times/mm or more, it was judged as ○ (good), if it was 1000 to 3000 times/mm, it was judged as △ (passable), and if it was less than 1000 times/mm, it was judged as × (unacceptable).

The 20°C Cantabro loss rate (%) obtained by the 20°C Cantabro test to evaluate the above-mentioned aggregate scattering resistance, the dynamic stability DS (times/mm) obtained by the wheel tracking (WT) test to evaluate the flow resistance, the -10°C bending strain (×10 ^-3 ) obtained by the bending test to evaluate the deflection follow-up ability, and the pour point (°C) of the plasticizer component to evaluate the workability during use are summarized in Table 4 for Example 1 and Comparative Examples 1 to 3 shown in Table 2.

The results shown in Table 4 for each item obtained for Example 1 and Comparative Examples 1 to 3 are shown in Table 5 as ○ (good), △ (passable), or × (unacceptable).

表５に示す評価結果から明らかなように、可塑剤として脂肪酸と脂肪酸ピッチを併用した実施例１においては、脂肪酸のみを単体で使用した比較例１に比してたわみ追従性（曲げひずみ）や骨材飛散抵抗性（２０℃カンタブロ損失率）が改善され、当該常温アスファルト混合物の作業性の良否の指標となるアスファルトの可塑剤成分の流動点（低温時の作業性）も改善されている。その一方で、実施例１においては、耐流動性（動的安定度）は、比較例１よりも低い値を示すものの、舗装計画交通量３０００台／日以上の道路の塑性変形輪数の基準値を満足している。

As is clear from the evaluation results shown in Table 5, in Example 1, in which fatty acid and fatty acid pitch were used in combination as plasticizers, the deflection follow-up (bending strain) and aggregate scattering resistance (20°C cantabro loss rate) were improved compared to Comparative Example 1, in which only fatty acid was used alone, and the flow point of the plasticizer component of the asphalt (workability at low temperatures), which is an indicator of the workability of the asphalt mixture at room temperature, was also improved. On the other hand, in Example 1, although the flow resistance (dynamic stability) is lower than that of Comparative Example 1, it meets the standard value of the number of wheels for plastic deformation on roads with a planned pavement traffic volume of 3,000 vehicles/day or more.

However, when an oil-based property improver is added to a room temperature asphalt mixture that utilizes the saponification reaction (neutralization reaction) of fatty acids to impart flexibility, there is a trade-off in properties in which the deflection tracking ability, aggregate scattering resistance (cantabro loss rate), and flow point of the plasticizer component (workability at low temperatures) improve, but the flow resistance (dynamic stability) decreases.

However, Example 1 has a better balance of the trade-off than Comparison Example 2, in which mineral oil was used instead of fatty acid pitch, and Comparison Example 3, in which vegetable oil was used.

The above results confirm that the fatty acid pitch used in Example 1 has superiority as a property improving agent among oil components.

Therefore, the room temperature asphalt mixture of this embodiment uses inexpensive fatty acid pitch, an industrial by-product (residue) of fatty acid production, as a property improvement agent, and by setting the fatty acid:fatty acid pitch ratio to 75:25, it is possible to achieve the effects of improving low-temperature workability and economy while maintaining high flow resistance, aggregate scattering resistance, and deflection tracking ability.

In particular, it was confirmed that low-temperature workability can be improved by using a combination of fatty acids and fatty acid pitch (vegetable oil) as a plasticizer. In other words, it was found that fatty acids alone will crystallize and solidify below a certain temperature, although the temperature varies depending on the composition. Therefore, it was confirmed that mixing with materials that are difficult to crystallize and have a low melting point, such as vegetable oil or mineral oil, inhibits the crystallization of the fatty acids and lowers the freezing point.

In the present embodiment, the ratio of fatty acid pitch:fatty acid is set to 25:75 , but it has been confirmed that the same effect as described above can be obtained by setting this ratio in the range of 40:60 to 5:95.

In addition, in the present invention, recycled aggregate obtained by crushing and classifying waste materials from asphalt pavement may be used to partially replace the crushed stone and sand shown in Table 1. By using recycled aggregate in this way, further cost reductions in cold asphalt mixtures can be achieved.

In addition, the present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims and the technical ideas described in the specification.

Claims (2)

A cold asphalt mixture comprising at least aggregate, asphalt, a plant-derived property improver that is fatty acid pitch, an industrial by-product of fatty acid production , a lubricating solidifier (fatty acid and/or fatty acid dimer and/or fatty acid trimer , none of which contains pitch ), and cement;
A cold asphalt mixture characterized in that the ratio of the property improver to the lubricant solidifying agent is set in the range of 40:60 to 5:95. The cold asphalt mixture according to claim 1, characterized in that recycled aggregate is mixed as part of the aggregate.