JPH0116436B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing thermally engineered asphalt concrete that is inexpensive and has excellent stability, particularly a method using polyvinyl chloride fine pieces or powder as a binder and a peroxo acid salt and a surfactant as a polymerization initiator. Regarding. 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 paving material for roadways 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. By the way, in the case of dense-grained asphalt concrete, which is currently most commonly used for surface layers, the marshal stability is highest when the amount of asphalt is 6 to 6.5% (wt%, the same applies hereinafter), and it is usually 700%.
Shows a value of ~850Kg. By the way, the standard value is 750 or higher for C traffic or higher, and 500 or higher for other traffic. (Over 500 for the base layer and over 350 for the upper subgrade.) However, on roads with extremely heavy traffic such as major national roads and expressways, ordinary dense-grained asphalt concrete lacks stability, and rubber powder, rubber emulsion, thermoplastic Modified asphalt concrete mixed with resin emulsion etc. is used. However, although these exhibit high stability of 1,000 to 1,600 kg, they have the disadvantage of being difficult to construct and 20 to 30% more expensive. On the other hand, the proportion of asphalt in the material cost of asphalt concrete is extremely high, reaching 50% in the case of standard dense-grained asphalt concrete. Moreover, as the price of crude oil increases, this ratio and the overall cost will continue to increase, and if the amount of asphalt is reduced, the stability will decrease (around 550 in the case of 4%). In order to address the above problems, the present inventors conducted research to reduce the amount of asphalt without reducing stability, and as a result, mixed polyvinyl chloride powder or pieces together with an inorganic polymerization initiator for vinyl chloride. We have developed a technology to do this. This reduces the amount of asphalt,
In addition to improving stability, this also led to a solution to the problem of processing agricultural waste PVC film. However, its stability did not reach that of conventional modified asphalt concrete. Therefore, the present inventors further continued research on polymerization initiators, and as a result, succeeded in significantly improving stability by using a surfactant together with a polymerization initiator. The present invention will be explained in detail below. First, the standard dense-grained asphalt concrete mix aggregate was put into a mixer and mixed for about 5 to 10 seconds.
Straight asphalt (same below), polyvinyl chloride film strips (about 2% based on asphalt), peroxo acid salts, and surfactant are added and mixed thoroughly with stirring. This time is approximately 50 to 60 seconds.
This asphalt mixture is applied in the same way as ordinary asphalt mixtures, but its physical properties and other stability are comparable to or higher than ordinary formulations of 6% straight asphalt, and the combination of peroxo acid salt and surfactant. In some cases, the values were comparable to those of modified asphalt concrete. Although it is not clear how this phenomenon occurs, it is presumed that it is due to the thermal decomposition properties of polyvinyl chloride and the uniform dispersion effect of the surfactant. That is, first, polyvinyl chloride starts thermal decomposition at a relatively low temperature, depending on the degree of polymerization and filler. Moreover, the softening point is usually 65 to 80°C. Therefore, in heated asphalt (max. 185°C, usually 160-170°C), some polyvinyl chloride flakes and powders are partially or completely monomerized. Vinyl chloride monomer has a low boiling point (-13°C) and will evaporate if left as is, but it remains sealed in the highly viscous asphalt for a while. When a polymerization initiator is added in this state, repolymerization begins, and as the temperature of the mixture decreases, the PVC polymer begins to solidify. After paving, the compacted aggregates or aggregates and asphalt are fused together. It will be installed as soon as it is installed. 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. On the other hand, since the stirring time in the mixer is limited from a quality standpoint, the reaction tends to be uneven. Therefore, the surfactant is presumed to have the function of uniformly dispersing the polyvinyl chloride pieces/powder and the polymerization initiator in the asphalt, thereby making the reaction more complete. The materials used in the present invention include heated asphalt, virgin polyvinyl chloride powder resin that is at least partially thermally decomposed in a heated mixture, powders and pieces of PVC film and other molded products, and even PVC and vinyl acetate. Polymer powders and flakes are preferred.
In addition, agricultural waste PVC film is very difficult to dispose of, but in the present invention, even if it has soil attached to it, it can be crushed and used as is, so there is no processing cost and it is extremely preferable from the perspective of pollution prevention. be. And the mixing ratio is 0.5 to asphalt.
-5%, especially 1-3% is preferable from the viewpoint of improving stability. Note that the PVC film strips may be used by being directly mixed with asphalt in a heating tank in advance, or may be mixed with aggregate and then injected with asphalt. It is also possible to use a material in which fine pieces are dispersed in water to form an emulsion. On the other hand, peroxo acid salts used as polymerization initiators for vinyl chloride include ammonium salts, potassium salts, and sodium salts of peroxonitric acid, peroxocarbonic acid, 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. Incidentally, these are used in an amount of about 0.1 to 1% based on the amount of asphalt, and more preferably 0.2 to 0.5%. Next, as the surfactant, cationic and anionic surfactants can be used, but nonionic surfactants are particularly preferred. 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%, particularly preferably 0.5 to 2%. By the way, the most preferable ratio of asphalt in normal surface asphalt concrete is 6 to 6.5% as mentioned above (the smaller the amount of fine aggregate or filler, the smaller the ratio, and the larger the amount), but the ratio of asphalt in the present invention is 6 to 6.5%. In this case, it is smaller than this value, and this is also a major feature. That is, the preferred ratio of asphalt in the present invention is 3 to 6% in the case of dense-grained asphalt concrete;
In particular, it is about 3.5 to 5%. This is because if it is around 6%, the amount of asphalt that covers the surface of the aggregate is necessary and sufficient, so vinyl chloride cannot exert a sufficient reinforcing effect.On the other hand, if it is too small, the binder effect will be insufficient, making it brittle and unstable. Deteriorate. And 4-5
%, it is of course possible to obtain products with stability equivalent to or higher than those using other reinforcing additives (for example, rubber-based additives) in the case of 6% of conventional products. On the other hand, in the case of the base layer and roadbed (upper roadbed), the optimum proportion of asphalt is smaller than in the case of the surface layer because the particle size of the aggregate is large. That is, the base layer is composed of coarse-grained asphalt concrete with an asphalt content of 4.5 to 6%, and the upper subgrade is generally mixed with about 3.5 to 4% asphalt as a stabilizing agent. (The standard value of stability is 500 or more for coarse particles and 350 or more for stabilized particles.) However, in the case of the present invention, the amount of asphalt is 2 to 3.
%, it is possible to obtain a product that fully satisfies these criteria. 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. Next, the present invention will be explained in more detail with reference to Examples. Note that % indicates weight %. Example 1 As aggregates, 35 kg of heated S-13 (JIS A5001) crushed stone, 25 kg of S-5 (crushed stone), 19 kg of screenings, 12 kg of sand, and 5 kg of stone powder were put into a mixer and kept at 170°C for 10 minutes. Knead for a second. Then 170
Straight asphalt heated to °C (penetration
69) 4 kg (4% of the total amount of aggregate and asphalt) and 80 g of 1-2 mm square pieces of polyvinyl chloride agricultural waste film (2% of asphalt),
Sodium peroxoborate 10g (vs. asphalt)
0.25%) and solid nonionic surfactant "Emulgen" (ST-7, Kao Corporation) 20g (0.5% to asphalt) were placed in a mixer and stirred for 50 seconds to produce 100.11Kg of heated asphalt. Get a mixture.
In addition, Emulgen 1% (40g) to asphalt,
Heated asphalt mixtures containing 1.5% (60 g) and 4% (160 g) were prepared, respectively. Test pieces were prepared using these mixtures in a conventional manner, and the measurement results obtained are shown in Table 1. Example 2 Sodium peroxoborate 10g (based on asphalt 0.25%), Emulgen 40g (based on asphalt 1)
%) and 40g and 120g of polyvinyl chloride strips, respectively.
A heated asphalt mixture was obtained in the same manner as in Example 1 except that 1% and 3% of asphalt were used. Example 3 80 g of polyvinyl chloride strips, 40 g of Emulgen,
A heated asphalt mixture was obtained in the same manner as in Example 1 except that 4 g and 40 g of sodium peroxoborate (0.1% and 1% relative to asphalt) were used. Example 4 Using 40g of liquid "NC-50" (manufactured by Lion Corporation) as a surfactant (1.0% of asphalt),
Otherwise, a heated asphalt mixture is obtained in the same manner as in Example 1. Example 5 A heated asphalt mixture was obtained in the same manner as in Example 1 except that 10 g of ammonium peroxodisulfate (0.25% based on asphalt) was used as a polymerization initiator. Comparative Example 1 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. Comparative Example 2 Straight asphalt 6.13 heated in the same manner as in Example 1 was added to the same proportion of aggregate (96 kg) as in Example 1.
Kg (6% based on the amount of aggregate and asphalt) is mixed and stirred to obtain 100.13 Kg of heated asphalt mixture. The measurement results of Examples 2 to 5 and Comparative Examples 1 to 2 are shown in Table 1, respectively.

【table】

[Table] Example 6 Aggregate with coarse particle size [S-20 crushed stone 19.0%, S-
13 crushed stone 29.3%, S-5 crushed stone 20.9%, S.C10.4
%, sand 10.4%, stone powder 4.7%], the same straight asphalt as in Example 1 at 3, 4, and 5% (based on the total amount of aggregate and asphalt), polyvinyl chloride at 2% asphalt, and asphalt
0.25% of 30% hydrogen peroxide solution is mixed in the same manner as in Example 1 to obtain a heated asphalt mixture. Comparative Example 3 As in Example 6, only asphalt was mixed into coarse-grained aggregate in an amount of 5% based on the total amount of aggregate and asphalt to obtain a heated asphalt mixture. Example 7 Aggregate mixed for upper roadbed [S-20 crushed stone 31.5%,
S-13 crushed stone 15.4%, S-5 crushed stone 13.5%, S.
C18.3% sand 14.4%, stone powder 2.9%] and the same straight asphalt as in Example 1 at 2, 3, and 4%, respectively.
(based on the total amount of aggregate and asphalt), polyvinyl chloride with an asphalt content of 2% and a 30% hydrogen peroxide solution with an asphalt content of 0.25% are mixed in the same manner as in Example 1 to prepare a heated asphalt mixture. obtain. Comparative Example 4 Add asphalt only to the aggregate at the same mixing ratio as in Example 7 at a ratio of 4 to the total amount of aggregate and asphalt.
% to obtain a heated asphalt mixture. The measurement results of Examples 6-7 and Comparative Examples 3-4 are shown in Table-2. From the above results, it can be seen that the thermally engineered asphalt concrete of the present invention exhibits excellent values in the Marshall stability test. Especially for dense grain size,
Depending on the combination of polymerization initiator and surfactant, even if the amount of asphalt is reduced from the standard 6% to 4% (reducing the cost by about 17%), it will still be about 50% lower than the value when it is 6%. It may improve. In addition, coarse grain size
In the case of stable treatment, even if the amount of asphalt is reduced by 1 to 2% from the conventional standard ratio, sufficient practical strength can be obtained, making a significant contribution to the effective use of asphalt, reducing the cost of asphalt concrete, and increasing its strength. It is something that does. Furthermore, it is only necessary to add a very small amount of polymerization initiator and surfactant to the asphalt, and no special equipment or techniques are required; conventional equipment can be used as is, and the manufacturing cost is also the same as that of conventional ones. Furthermore,
It also enables effective use of agricultural waste films, which have traditionally been difficult to dispose of, and is also highly effective in terms of energy conservation.

Claims (1)

[Scope of Claims] 1. A method for producing asphalt concrete for pavement, which comprises adding polyvinyl chloride powder or pieces, a peroxo acid salt, and a surfactant to aggregate and bituminous material, and stirring and mixing the mixture. 2. The method for producing asphalt concrete for pavement according to claim 1, wherein a nonionic surfactant is used as the surfactant.