JPH0251859B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing thermally engineered asphalt concrete using a thermoplastic resin as a reinforcing material, and an additive for reinforcing asphalt concrete. Thermal engineered asphalt concrete is a bituminous material (mainly straight asphalt) made by heating and melting several types of aggregate (including filler) with different particle sizes.
It is widely used as a road paving material due to its excellent cost and performance. Its static strength is expressed by its marshal stability, and the higher the value, the better it can withstand heavy traffic. In the case of dense-grained asphalt concrete, which is currently most commonly used for surface layers, the amount of asphalt is 6 to 6.5%.
(% by weight, the same applies hereafter), the marshal stability is highest and usually shows a value of 700 to 850 kg. By the way, the standard value is 750 or higher for C traffic or higher, and 500 or higher for other traffic. In addition, the base layer is usually coarse-grained asphalt concrete with an asphalt content of 4.5 to 6%, and the upper subgrade is made of 3.5 to 4% asphalt as a stabilizer.
% of asphalt is used, and the stability is said to be 500 or higher for the base layer and 350 or higher for the upper layer base course. On the other hand, the proportion of asphalt in the material cost of asphalt concrete is extremely high, with standard dense-grained asphalt concrete having a
%, and as crude oil prices rise, this percentage and overall costs will only increase. However, reducing the amount of asphalt lowers the stability; for example, in the case of dense grains, if the asphalt content is 4%, the stability becomes around 550, making it unusable. In view of the above, the present inventors conducted various studies and succeeded in reducing the proportion of asphalt without reducing stability by using strips of polyvinyl chloride film (Japanese Patent Application Laid-Open No. 116167/1983). ).
That is, when mixing aggregate and bituminous material, strips of polyvinyl chloride film are mixed with 0.5 to 5% of asphalt.
By mixing and adding an inorganic polymerization initiator and a surfactant, the asphalt ratio can be adjusted to 3.5 to 5.
% (in the case of dense-grained asphalt concrete), we were able to obtain asphalt concrete that exhibits stability of 750 or more, and in some cases as high as 1300. When the amount of asphalt is around 4%, the stability is highest, and when the amount of asphalt is around 6%, there is almost no increase in stability. This fact suggests that fragments of polyvinyl chloride film that have been melted and partially decomposed in the asphalt are repolymerized by the action of an inorganic polymerization initiator, resulting in the formation of bonds between aggregates and between aggregates and asphalt. Guessed. In addition, the present inventors similarly added asphalt to 4%
By adding putty-like polystyrene (styrofoam melted and softened with a solvent) and putty-like polystyrene and pieces of polyvinyl chloride film, they succeeded in obtaining a product with an amazing stability of more than 2,000. Publication No. 59-213804). Based on the above facts, the inventor continued to experiment and found that thin pieces of polyvinyl chloride film or thermoplastic resins other than putty-like polystyrene had a similar reinforcing effect, thereby completing the present invention. , the present invention will be explained in detail below. In the present invention, polyethylene, polypropylene,
Molded products such as polystyrene, pulverized products thereof, virgin resins such as polyethylene, polypropylene, polystyrene, polyvinyl chloride, copolymers thereof, emulsions, or mixtures thereof are preferably used. Also used is a putty-like polystyrene obtained by melting and softening expanded polystyrene with a solvent, defoaming it, and drying and pulverizing it. In this case, as the solvent, thinner, acetone, ligroin, styrene monomer, a mixture of ethyl alcohol and trichlene, etc. are used. By the way, currently most of the disposal of unnecessary resin molded products (so-called waste plastics) is by incineration or landfilling, but the former has problems such as generation of toxic gas and damage to incinerators, and the latter has limited space and is a big waste. It has become a social problem. Therefore, some methods have been carried out to extract the active ingredients by thermally decomposing the resin or melting and remolding the resin, but these methods require pretreatment such as sorting and cleaning, and are not cost-effective. On the other hand, in the present invention, even if various resins are mixed together, or even if there is dirt attached, such as agricultural waste film, it can be used by pulverizing it as it is. Moreover, 80 to 90% of waste plastics are thermoplastic resins, and up to 90% of them are the resins listed above.
It is a great advantage that it can be used effectively. However, these thermoplastic resins are thermally decomposed by heated asphalt or heated aggregate in a mixer (the temperature of heated asphalt is usually 160-160℃).
170℃, but there are no quality problems up to about 240℃), and it is dispersed in asphalt. When a polymerization initiator is added in this state, repolymerization begins, and as the temperature of the mixture decreases, the resin begins to solidify, and after paving, the compacted aggregates or aggregates and asphalt are fused together. incorporated in the state. As a result, the stability of the asphalt concrete increases, and even if the amount of asphalt is less than the standard amount, it is thought that the strength is equivalent to or higher than that of the standard amount. In addition, it may be mixed with asphalt or a mixer that has been separately thermally decomposed, or it may be partially or totally decomposed by means other than heat, such as chemicals such as solvents, acids, alkalis, light, radiation, etc. It's okay. In this way, a resin with a high heat resistance temperature can also be used. The mixing ratio of the resin to the asphalt is preferably 0.5 to 5%, particularly 1 to 3%, from the viewpoint of improving stability. On the other hand, the polymerization initiator is preferably an inorganic one from the viewpoint of heat resistance, and pereoxosate and aqueous hydrogen peroxide are particularly effectively used. Peroxo acid salts include ammonium salts, potassium salts, sodium salts, etc. of peroxonitric acid, peroxocarbonate, peroxodisulfuric acid, peroxoboric acid, peroxosulfuric acid, peroxophosphoric acid, and the like. These have properties as oxidizing agents, and among these, potassium salts and ammonium salts of peroxodisulfuric acid are known as polymerization initiators, but peroxoborates also exhibit extremely excellent effects in the present invention. These are used in an amount of about 0.1 to 1% based on the amount of asphalt.
More preferably it is 0.2 to 0.5%. Next, hydrogen peroxide is also an oxidizing agent, but like peroxo acid salts, it also acts as a polymerization initiator, and depending on the type and mixing ratio of the resin, the stability can be increased. just,
If the hydrogen peroxide solution is too small, the polymerization effect will not be sufficient, and if it is too large, the stability will decrease, probably due to decomposition of asphalt, so a solution with a concentration of 30% is 0.1 to 1% of asphalt, more preferably 0.2 to 0.5%. Use %. However, one of the reasons for the increase in stability is thought to be that when hydrogen peroxide is added, the asphalt expands in volume and covers the aggregate well. Note that adding a surfactant to these reaction systems often improves stability (especially in the case of peroxo acid salts), but this is because the resin and polymerization initiator are more uniformly dispersed in the asphalt. This seems to be because the reaction is more complete. This surfactant may be cationic or anionic, but
Particularly preferred are nonionic ones. This seems to be due to the fact that the aggregate is positively charged and the asphalt is negatively charged. The ratio of surfactant to asphalt is 0.3 to 4%, especially
0.5-2% is preferred. By the way, the most preferable ratio of asphalt in normal asphalt concrete for surface layer is 6 to 6.5% as mentioned above (the less fine aggregate or filler is used, the smaller it is, and the more it is, the larger it is). In this case, the most preferable ratio is smaller than this value, and this is also a major feature. That is, the preferable ratio of asphalt in the present invention is about 3 to 6%, particularly about 3.5 to 5% in the case of dense-grained asphalt concrete.
This is because if it is around 6%, there is not enough asphalt to cover the surface of the aggregate, so the thermoplastic resin will not be able to exert sufficient reinforcing action.On the other hand, if it is too small, the binder action will be insufficient, resulting in brittleness and stability. becomes worse. In the case of 4 to 5%, of course the conventional product of 6%, depending on the type of resin and the combination of polymerization initiators, it is as stable as that of conventional products using reinforcing additives such as rubber. You can get the degree. The asphalt concrete obtained by the present invention is
The flow value is also within the standard value (20 to 40 1/100cm). On the other hand, in the case of the base layer and roadbed (upper roadbed), the optimum proportion of asphalt is smaller than that in the surface layer because the particle size of the aggregate is large. That is, as mentioned above, the base layer is composed of coarse-grained asphalt concrete with an asphalt content of 4.5 to 6%, and the upper roadbed is generally made of asphalt concrete mixed with about 3.5 to 4% of asphalt as a stabilizing agent. However, in the case of the present invention, even if the amount of asphalt is 2 to 3%, a product that fully satisfies these standards can be obtained. The amount of asphalt used in the base layer and roadbed is larger than that in the surface layer, and reducing the amount of asphalt has an extremely large economic effect. still,
Each layer (surface layer, base layer, roadbed) may be entirely composed of asphalt concrete obtained by the present invention, or may be used in combination with conventional asphalt concrete. In particular, in the case of the surface layer, the product of the present invention may be used in the upper and lower layers of the upper and lower layers. By the way, most asphalt concrete is currently manufactured by the batch method, in which heated aggregates and fillers are put into a mixer equipped with a heating device, stirred and dried, and then a predetermined amount of asphalt is poured and continued stirring. Make asphalt concrete. Therefore, in the present invention, the resin component is melted in asphalt in advance, or it is put into a mixer together with the aggregate and asphalt and melted. The polymerization initiator and surfactant are preferably added during or after asphalt injection. However, resin, polymerization initiator,
Surfactants make up a very small proportion of the total and must be measured accurately. In the case of liquids such as emulsion resins and hydrogen peroxide solutions, metering can be carried out reliably by pump injection, but in the case of powders and pulverized materials, they must be metered one by one, making the operation complicated. Therefore, the predetermined amounts of resin, polymerization initiator, and surfactant required for one batch (for example, 1 ton of asphalt concrete) [for example, assuming 4% asphalt, 800 g of resin (2% of asphalt), 100 g of polymerization initiator (0.25% of asphalt) ), surfactant
400g (1% of asphalt)] is mixed well and packed in a bag as a reinforcing additive, and then sprinkled into the mixer when injecting asphalt. Handling is convenient and accurate mixing ratio can be obtained. You can get things easily. This reinforcing additive is
Type of asphalt concrete, required stability, type and particle size distribution of aggregate, type of asphalt (plain asphalt or modified asphalt)
It is necessary to select various types and proportions of resins and polymerization initiators, as well as types and proportions of surfactants, depending on the type and grade. Next, the present invention will be explained in more detail with reference to Examples. Note that % indicates weight %. Example 1 Heated S-13 (JIS A 5001) as aggregate
35 kg of crushed stone, 25 kg of S-5 (crushed stone), 19 kg of screenings, 12 kg of sand, and 5 kg of stone powder were respectively put into a mixer, kept at 170°C, and mixed for 10 seconds (dense particle size blend). Next, 4 kg (4% of the total amount of aggregate and asphalt) of straight asphalt (penetration degree 69) heated to 170°C and 80 g of strips of polyethylene agricultural waste film (1 to 2 mm square) were added. Asphalt 2%), sodium peroxoborate 10g
(0.25% of asphalt) into a mixer,
Stirred for 50 seconds to obtain 100.09Kg of heated asphalt mixture. A test piece was prepared using this mixture in a conventional manner, and the measurement results obtained are shown in Table 1.
(). In addition to the above formulation, the solid nonionic surfactant "Emulgen" (ST-7, manufactured by Kao Corporation) 10
g (0.25% to asphalt), polyethylene strips to 4% to asphalt, 1% to asphalt, polyethylene strips to 4% to asphalt, and sodium peroxoborate to 0.5% to asphalt. A heated asphalt mixture was prepared. Test pieces were prepared using these mixtures in a conventional manner, and the measurement results obtained are also shown in Table 1. Comparative Example 1 A heated asphalt mixture was obtained in the same manner as in Example except that sodium peroxoborate (polymerization initiator) was not used. The measurement results are shown in Table-1. Comparative Example 2 4 kg of straight asphalt heated in the same manner as in Example 1 was added to aggregate (96 kg) in the same proportion as in Example 1.
were mixed and stirred to obtain 100 kg of heated asphalt mixture. The measurement results are shown in Table-1. Comparative Example 3 As aggregate, heated S-13 crushed stone 35 kg, S-5
Put 25kg of crushed stone, 19kg of screenings, 12kg of sand, and 5kg of stone powder into a mixer, and dry mix for 10 seconds while keeping the temperature at 170℃. 6.13 kg of straight asphalt (6% based on aggregate and asphalt amount) heated to 170℃ and 15.3 g of 30% hydrogen peroxide solution (0.25% based on asphalt amount) were poured into a mixer and stirred for 50 seconds to produce 102.1453 kg of straight asphalt. A heated asphalt mixture is obtained. Similarly, the measurement results are shown in Table-1. Comparative Example 4 Using the same amount and ratio of aggregate (94 kg) as in Comparative Example 3 and the same amount of straight asphalt (6 kg), the same operation was performed to obtain 100 kg of heated mixture. Similarly, the measurement results are shown in Table-1. Example 2 96 kg of aggregate in the same proportion as in Example 1 was stirred and heated in a mixer in the same manner as in Example 1, and then 4 kg of straight asphalt heated in the same manner as in Example 1.
Crushed polypropylene molded products packed in bags
A mixture of 80 g (2% of asphalt) and 10 g of sodium peroxoborate (0.25% of asphalt) was taken out of the bag and put into a mixer, and stirred for 50 seconds to obtain 100.09 kg of heated asphalt mixture (). In addition, the same ratio of aggregate as in Example 1, heated asphalt, and pulverized polypropylene molded product were used.

【table】

[Table] and sodium peroxoborate are mixed in the proportions shown in Table 1 to obtain a heated asphalt mixture (
~). The results of each measurement are shown in Table-1. Example 3 95 kg of aggregate and 5 kg of asphalt in the same proportions as in Example 1, 100 g of a mixture of equal amounts of polyvinyl chloride film pieces, expanded polystyrene powder, and polypropylene film pieces (2% of asphalt), and peroxoboric acid as a polymerization initiator. 12.5 g each of sodium and 30% hydrogen peroxide solution (0.25% to asphalt) were mixed and treated in the same manner as in Example 1 to obtain a heated asphalt mixture. Example 4 A mixture of equal amounts of polyvinyl chloride chips, expanded polystyrene powder, and polypropylene film chips was added to 96 kg of aggregate and 4 kg of asphalt in the same proportions as in Example 1.
80g (2% based on asphalt), 10g sodium peroxoborate (based on asphalt) as a polymerization initiator
0.25%) and 20 g of 30% hydrogen peroxide solution (0.5% to asphalt) were mixed in and treated in the same manner as in Example 1 to obtain a heated asphalt mixture. Example 5 96 kg of aggregate in the same proportion as in Example 1, 4 kg of asphalt, and putty-like polystyrene [1 kg of foamed polystyrene was crushed appropriately and soaked in 1. Lutzker thinner (containing about 50% toluene) to soften and melt. 800 g (20% to asphalt) of dried and pulverized material (mixed well with a spatula), and 10 g (20% to asphalt) of sodium peroxoborate (20% to asphalt)
0.25%) to obtain a heated asphalt mixture in the same manner as in Example 1. Example 6 Aggregate with coarse particle composition [20% crushed stone of S-20, S-13
Crushed stone 31%, S-55 crushed stone 22%, S.C 11%, sand
11, 5% stone powder], 4% asphalt (based on the total amount of aggregate and asphalt), pulverized polypropylene molded product with 2% asphalt content, and sodium peroxoborate with 0.25% asphalt content as in Example 1. to obtain a heated asphalt mixture. Comparative Example 5 As in Example 6, only asphalt was mixed in an amount of 5% based on the total amount of coarse-grained aggregate to obtain a heated asphalt mixture. Example 7 Aggregate mixed for upper roadbed [S-20 crushed stone 33%, S
-13 crushed stone 16%, S-5 crushed stone 14%, S.C 19%,
15% sand, 3% stone powder], 3% asphalt (based on the total amount of aggregate and asphalt),

【table】

[Table] A pulverized polypropylene molded product containing 2% asphalt and sodium peroxoborate containing 0.25% asphalt were treated in the same manner as in Example 1 to obtain a heated asphalt mixture. Comparative Example 6 4% asphalt was mixed into the aggregate having the same composition as in Example 7 to obtain a heated asphalt mixture. The measurement results of Examples 4 to 10 and Comparative Examples 5 and 6 are shown in Table 2. From the above results, it can be seen that the thermally engineered asphalt concrete obtained according to the present invention exhibits excellent values in the marshal stability test. In particular, in the case of dense-grained asphalt concrete, even if the amount of asphalt is reduced from 6% to 4% (from a cost perspective
(17% reduction), it completely satisfies the standard value at 6%, and depending on the combination of resin, polymerization initiator, and even surfactant, it can be improved by about 40% over the usual 6%. In addition, in the case of particle size and stabilization treatment, even if the amount of asphalt is reduced by 1 to 2% from the conventional standard ratio, sufficient practical strength can be obtained, allowing for effective use of asphalt, cost reduction, and strength of asphalt concrete. This will make an extremely large contribution in terms of development. On the other hand, as for the resin, not only virgin resin powder, pellets, and emulsion, but also unnecessary resin molded products, so-called waste plastics, and their pulverized products can be effectively used, which is a major feature of the present invention. Furthermore, only a small amount of polymerization initiator or surfactant needs to be added to the asphalt, and no special equipment or technology is required; conventional equipment can be used as is, and the manufacturing cost remains almost the same.
Furthermore, if you mix and package the resin powder, pulverized material, polymerization initiator, and surfactant necessary for each batch in a predetermined proportion according to the type of asphalt concrete, you will not have to worry about measuring it before use and will be able to use it accurately. It is extremely convenient to mix.

Claims (1)

[Scope of Claims] 1 Thermoplastic resin powder, pellets, emulsion, thermoplastic resin molded products, or pulverized products thereof, or mixtures thereof (excluding pulverized polyvinyl chloride resin alone), partially or completely. The decomposition step is performed during or before mixing the aggregate and bituminous material, and the decomposed resin in the mixture is repolymerized by an inorganic polymerization initiator also mixed in the mixture. A method for producing asphalt concrete for pavement, characterized by using repolymerized resin and bituminous material as an aggregate binder. 2. The method for producing asphalt concrete for pavement according to claim 1, wherein a peroxo acid salt is used as an inorganic polymerization initiator. 3. The method for producing asphalt concrete for paving according to claim 1, wherein a surfactant is added. 4 In dense grained asphalt concrete,
The method for producing asphalt concrete for pavement according to claim 1, 2, or 3, wherein 3.5 to 5.0% by weight of asphalt is used based on the total amount of asphalt.