JPS6339536B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an admixture for lightweight concrete, and particularly to an admixture that uses foamed thermoplastic synthetic resin particles as a lightweight aggregate to be mixed into concrete. Conventionally, lightweight concrete has often been made using lightweight aggregates such as perlite, vermicrite, pumice, coal slag, and volcanic rock. However, all of these lightweight aggregates are porous and highly absorbent, and when mixing cement and water to make lightweight concrete, they do not have fluidity unless a large amount of water is added, resulting in poor physical properties after hardening. There are drawbacks. In other words, it has disadvantages such as low strength due to a large water/cement ratio, large drying shrinkage that causes cracks, high water absorption and poor thermal conductivity, and a long time required for curing and drying. On the other hand, if foamed thermoplastic synthetic resin particles (e.g. foamed polystyrene particles) are used as lightweight aggregates, the aforementioned disadvantages can be solved because the foamed particles have almost no water absorption, but since the surface is hydrophobic, Because it has poor affinity with cement and a large difference in specific gravity, it easily separates and rises to the top during hardening, making it impossible to form uniform lightweight concrete. Therefore, in order to make the surface of foamed particles hydrophilic, it has been proposed to coat them with epoxy emulsion, acrylic emulsion, vinyl acetate emulsion, ethylene vinyl acetate emulsion, synthetic rubber latex, asphalt emulsion, etc. In addition, adding cement dispersants and cement superfluidizers to minimize the water/cement ratio during construction eliminates floating particles and improves all physical properties after hardening, so various additives are used. has been done. However, cement superplasticizers (e.g. Kao Maite, Melment, etc.) deteriorate in a short time after being added to concrete and are only effective for about 30 minutes.
Conventionally, foamed particles, emulsion, cement, water, and a cement superplasticizer were mixed and stirred on site, but not only were mixing errors likely to occur due to mistakes in measuring the cement superplasticizer, but also strong force was required. A mixer capable of stirring is required, and even with such a mixer, sufficient mixing and stirring cannot be achieved.
It has the disadvantage that it is difficult to obtain lightweight concrete with good physical properties such as uniform dispersion of foam particles and good bonding with cement. The present invention has been made to improve the above-mentioned drawbacks, and there is no need to mix a cement superplasticizer on site, and it is possible to use pre-made cement and water, or cement, sand, and water, or cement, sand, and water. cement,
To provide an admixture that can be thoroughly mixed and stirred into a mixture of sand, gravel, and water using a mixer in a fresh concrete mixer truck to immediately cast concrete and to obtain lightweight concrete with good physical properties. The mixed material of the present invention is made by adhering a polymer emulsion and a cement high-flow agent to the surface of foamed thermoplastic synthetic resin particles, and in the present invention, adhesion means that the above-mentioned required blending ratio is applied to the surface of the foamed particles. It refers to the state in which a polymer emulsion and a cement high-flow agent are mixed or not coated, and if necessary, an inorganic powder is attached and dried or in an undried state. The present invention will be explained in detail below with reference to the drawings. The foamed thermoplastic synthetic resin particles 1 used in the present invention are preferably those obtained by foaming polyethylene, polypropylene, especially polystyrene by a known method and molding the particles. The foamed particles 1 are spheres expanded 50 to 70 times, and preferably have a particle size distribution of 0.1 to 5 mm to some extent, but may be amorphous. 0.1
If there are many particles smaller than mm, the fluidity during construction will be poor;
If it is larger than mm, it has a large buoyancy and is not suitable for making uniform concrete. Furthermore, if the expansion ratio is small, the foamed particles will have strength but are economically unfavorable, while if the expansion ratio is large, the foamed particles will be economically efficient but have weak strength and become easily crushed. Therefore, when using polyolefin
1.5 times - 10 times, 20 times - when using polystyrene
70 times, especially 50 to 70 times is desirable. The admixture of the present invention is constructed by coating the surface of the foamed particles 1 with a coating material 2 made of, for example, a polymer emulsion and a cement fluidizing agent. The coating material 2 used is one that coats the surface of the foamed particles 1 well and uses a surfactant that does not inhibit the hardening of cement. Examples of the polymer emulsion include epoxy resin emulsion, acrylic resin emulsion, vinyl acetate resin emulsion, or copolymers thereof, ethylene vinyl acetate emulsion, and SBR.
Latex, NBR latex, CR latex and asphalt emulsion or mixtures thereof can be used. Among them, a mixture of asphalt emulsion and acrylic resin emulsion made for mixing with cement has good adhesion to the surface of foamed particles and is excellent in economical efficiency.
The amount of polymer emulsion is 1 to ¹ m3 of the bulk volume of foamed particles in the case of an emulsion with a solid content of 50%.
10 kg is preferred, and 2 to 5 kg is particularly optimal. 1
If it is less than 10 kg, it will not be compatible with the foam particles, and if it exceeds 10 kg, the foam particles will not be coated uniformly and will become lumpy, making it difficult to disperse into cement paste, mortar or concrete. A superplasticizer is a substance used to improve the fluidity of cement paste, mortar, or concrete when mixed with cement and water, cement, sand, and water, or cement, sand, gravel, and water, and is used to improve the fluidity of cement paste, mortar, or concrete. A compound, a melamine derivative, or a lignin sulfonate may be used alone or in a mixture thereof, and an amount corresponding to the specified amount of cement may be mixed with the polymer emulsion. It is also possible to adopt a method in which thermoplastic synthetic resin particles are coated with a polymer emulsion and then coated with a highly fluidizing agent. In addition, as a sulfonated product of naphthalene,
Preferably, a condensation reaction product of naphthalene sulfonic acid and formalin is represented by the following formula, M (metal)
The sodium salt is preferred. As melamine derivatives, sulfonic acid-based melamine resins, especially methylolated melamine sulfonate salts are mainly used, and the amino group of melamine is usually methylolated with 2 to 3 times the mole of formalin, and then this is further modified with a sulfonate salt. It is preferable that As the sulfonate salt, Na salt is preferred for the present invention. The preferred amount of high fluidizing agent used is 1 to 9 kg per 1 m ³ of bulk volume of foamed particles.
Therefore, if it is less than 1 kg, it is insufficient, and if it is more than 9 kg, it is too much and will be wasted. Others that add viscosity to cement paste, mortar or concrete: polyvinyl alcohol (PVA), carboxymethylcellulose (CMC), methylcellulose (MC), mannan,
Coatings with polyethylene oxide, ester gum, etc. also have an auxiliary effect. In order to produce the admixture of the present invention having the above-mentioned structure, first, the expanded particles 1 are placed in a stirrer and the polymer emulsion is sprinkled on the particles while stirring slowly to uniformly coat the particle surfaces. Next, a highly fluidizing agent and other additives are sprayed and coated uniformly to obtain an admixture of the present invention. It is best to sprinkle this admixture on fine inorganic powder such as calcium carbonate, silica powder, talc, diatom, etc. to prevent particles from adhering to each other. Furthermore, if this admixture is manufactured within the range of the blending ratio of the foamed particles, polymer emulsion, and high fluidizing agent, the polymer emulsion, etc. will flow down and separate from the surface of the foamed particles due to the water contained, resulting in the formation of the main material. Since the admixture will not become non-uniform, it is not necessarily necessary to include a drying process, but if it is packed in a bag without being forced to dry, that is, in an undried state, when mixed with cement paste, mortar, or concrete, It prevents particles from adhering to each other or scattering due to static electricity, resulting in good workability. Also, if it is dried, when mixed with cement paste, mortar, or concrete, the superplasticizer will slowly dissolve from the particle surface, but the polymer emulsion will be difficult to separate and will remain on the particle surface, so as a result, the above-mentioned drying will not be possible. The particles maintain an even greater affinity with the cement than in the case of drying, and can be more strongly bonded to the cement after drying. As shown in Table 1, the mixing ratio of cement and foamed particles varies depending on the target specific gravity, but the volume ratio is 1:0.5 to 1:6, and optimally 1:3 to 4.

[Table] Next, we will discuss the production of lightweight concrete.
Cement and water, or depending on the purpose, cement, sand, water, or cement, sand, gravel, and water are mixed and stirred in advance and placed in the mixer of a ready-mixed concrete mixer truck and transported to the construction site. The water to cement ratio varies depending on the purpose, but around 40% is appropriate.
It never exceeds %. The ready-mixed concrete mixer truck should be a rotating drum-type ready-mixed concrete mixer truck that can rotate up to 30 times per minute.
It is not necessary to have a mixer capable of powerful forced stirring. Uniform lightweight concrete can be obtained by adding a specified amount of the admixture of the present invention on site and stirring at 30 times/minute for 5 to 15 minutes. This can be poured and placed using a concrete pressure pump truck. As is clear from the above, according to the present invention, the admixture for lightweight concrete is made by adhering a polymer emulsion and a cement superplasticizer to the surface of foamed thermoplastic synthetic resin particles, so it has the following effects. play. Unlike the case where a relatively small amount of superplasticizer is mixed equally with synthetic resin foam particles, cement, water, etc. on site, the superplasticizer is preadhered and mixed with synthetic resin foam particles and polymer emulsion. , it is possible to uniformly disperse foamed particles in cement at the site in a short time and with a small amount of power, and it is possible to obtain a more uniform finished lightweight concrete product. Since the admixture of the present invention can be mixed into cement paste, mortar, or concrete on site in a short time, it is possible to perform concrete pouring work while maintaining high fluidity even with a small amount of water and before the effectiveness of the superplasticizer decreases. can be carried out. It is possible to eliminate mixing errors caused by mistakes in measuring the superplasticizer when blending the superplasticizer on-site, and there is no need for a mixer that performs special strong stirring as a mixer for mixing. A low powered mixer such as a mixer from a fresh concrete mixer truck can be used. Since the polymer emulsion and superplasticizer are attached to the surface of the foamed synthetic resin particles in advance, when such admixtures are mixed with cement paste, mortar, concrete, etc., the superplasticizer will slowly dissolve. The polymer emulsion is difficult to separate, and as a result, the affinity between the foamed particles and cement is maintained, making it easier to prevent separation due to floating of the foamed particles, and also solidifying the bond between the foamed particles and cement even after the cement dries. It is possible to improve the physical properties of lightweight concrete. The lightweight concrete mixed with the admixture of the present invention also has the advantage of being extremely easy to pump. In other words, long-distance pumping is possible without losing fluidity during pumping, and water,
Even if the cement ratio is small (less than 40%), the slump value (JIS A1101-1975) is over 20, which means it is extremely fluid, so it will not separate during pumping or only water will take the lead, and the pumping will be smooth. There is almost no change in the physical properties before and after. Next, Examples, Comparative Examples, and Reference Examples will be shown in order to help you understand the effects of the present invention. Example 1 A cement paste made by mixing 1300 kg of cement and 520 kg of water was loaded into a fresh concrete mixer truck with a total internal volume of 8 m ³ and a loading capacity of 5 m ³ , and the foamed polystyrene particles (admixture of the present invention) whose surface was treated with this were loaded.
3500 was mixed at the construction site and 10 times at a rate of 30 times/min.
The mixture was mixed and stirred for a minute, and concrete was poured using a pump. As a result, with a slump value of 21, the specific gravity
0.4, compressive strength 12Kg/cm ² , thermal conductivity 0.08kcal/mh
℃ lightweight concrete was obtained. The admixture of the present invention used here included 5 kg of asphalt emulsion per 1 m ³ of apparent bulk volume of the particles on the surface of polystyrene particles expanded 70 times, and sulfonated naphthalene (a product manufactured by Kao Soap Co., Ltd.) as a high fluidizing agent. FD) coated with 5 kg of stone powder and 10 kg of stone powder was used. It should be noted that no wetting or stickiness due to the emulsion was felt on the surface of the particles. Example 2 In the same ready-mixed concrete mixer truck as in Example 1,
A mortar made by mixing 1,800 kg of cement, 2,700 kg of sand, and 1,080 kg of water was loaded, and Example 1 was applied at the site.
3800 times of the same inventive admixture as above, 30 times/
After mixing and agitating for 15 minutes at a speed of 15 minutes, concrete was poured using a pump. As a result, lightweight concrete with a slump value of 15, a specific gravity of 1.0, and a compressive strength of 60 Kg/cm ² and a thermal conductivity of 0.25 kcal/mh°C was obtained. Comparative example: 1800 kg of cement and sand in the same ready-mixed concrete truck as in Example 1.
A mortar made by mixing 2,700 kg and 1,080 kg of water was loaded, and 18 kg of the aforementioned Mighty FD was added as a high fluidizing agent on site and mixed for 10 minutes. After that, 3,800 kg of admixture that was not coated with a high fluidizing agent was added. When the mixture was mixed for 15 minutes and then pumped, the effect of the superplasticizer diminished in the latter half of pumping, and the slump value became less than 10. Comparative example: 1800 kg of cement and sand in the same ready-mixed concrete truck as in Example 1.
A mortar made by mixing 2,700 kg and 1,080 kg of water was loaded, and 3,800 kg of the same admixture as in Example 1 was added, except that it was not coated with a high fluidizing agent on site, and mixed for 15 minutes.The slump value was determined. 5, pumping could not be done, and 180 kg of water was added to make the water/cement ratio 0.7, resulting in a slump value of 15, but the concrete hardened and shrank due to too much water, causing cracks.

[Brief explanation of the drawing]

The drawing is a sectional view showing an example of the admixture of the present invention. 1... Thermoplastic synthetic resin expanded particles, 2... A coating layer consisting of a polymer emulsion and a cement superplasticizer.

Claims (1)

[Claims] 1. Polymer emulsion and naphthalene sulfonate on the surface of foamed thermoplastic synthetic resin particles,
A lightweight concrete admixture comprising at least one cement superplasticizer selected from the group consisting of melamine derivatives and ligurin sulfonate.