JPH0442348B2 - - Google Patents

Description

[Detailed description of the invention]

[Field of Industrial Application] The present invention relates to a high-strength concrete composition with little reduction in workability, and more specifically to a compaction composition that prevents the workability of concrete from deteriorating over time and improves its workability and workability. Concerning high strength concrete compositions with good properties. [Prior art and its problems] High-strength concrete is generally produced by adding high-performance water reducing agents such as β-naphthalene sulfonate formalin high condensate, melamine sulfonate formalin high condensate, and purified lignin sulfonate to reduce the water-cement ratio. Manufactured by making it smaller. However, such high-strength concrete with a low water-cement ratio has the disadvantage of a very large slump loss. This concrete slump loss occurs even in ordinary concrete, and the cause is estimated to be as follows. i.e. cement, water and sand;
Cement mixtures made by mixing gravel and admixtures (admixtures) undergo physical and chemical aggregation of cement particles over time after being mixed, gradually losing fluidity and impairing workability and workability. decreases over time. In particular, in high-strength concrete such as the one mentioned above, the concentration of cement particles is high, so the agglomeration effect is much greater than in normal concrete.
It is very difficult to obtain a certain level of workability. In order to solve these problems, various methods have been devised to prevent deterioration of the workability of cement mixtures. For example, there is a method of adding a curing retarder such as oxycarboxylic acid for the purpose of preventing chemical aggregation.
Although this method can delay the hydration reaction of cement, it is difficult to prevent physical aggregation, and therefore slump loss cannot be prevented. Further, there are disadvantages such as a decrease in the early strength of concrete. Various methods have also been devised for adding special lignin sulfonates. However, although this method has a slight slump loss prevention effect compared to the conventional system using β-naphthalenesulfonic acid formalin high condensate, the effect is small;
It cannot be said that it is practically sufficient. As described above, these conventional methods for preventing deterioration in workability of cement mixtures have had many problems and have not been considered satisfactory. [Means for Solving the Problems] The present inventors have solved the above-mentioned problems, and have developed a material with good compaction properties that prevents the workability of concrete from deteriorating over time and improves its workability and workability. As a result of intensive research to obtain a high-strength concrete composition, the present invention has been completed. That is, the present invention provides coarse aggregate, fine aggregate, cement,
In a concrete composition comprising water and an admixture (agent), a sustained release agent (A) comprising a maleic anhydride copolymer having a weight average molecular weight of 500 to 50,000;
Selected from naphthalene sulfonic acid formaldehyde high condensate water reducing agent, sulfonated melamine resin water reducing agent, lignin sulfonic acid water reducing agent, carboxylic acid water reducing agent, styrene sulfonic acid water reducing agent, and water reducing agent having sulfonic and carboxyl groups. (A) and one or more water reducing agents (B).
A cement admixture having a solid content weight ratio of 2:98 to 20:80 with (B) is contained in a solid content of 0.1 to 2.0 parts by weight per 100 parts by weight of cement, and the water-cement ratio is 0.1 to 2.0 parts by weight.
28% to 45%, kneading slump value 12 to 24cm,
High strength with little deterioration in workability, characterized by a slump loss of 6 cm/60 minutes or less, an entrained air amount of 5% or less, and a 91-day age compressive strength of 400 Kg/cm ² or more after standard underwater curing. A concrete composition is provided. The mechanism of preventing slump loss according to the present invention is inferred as follows. After kneading, a cement mixture consisting of cement, water, and optionally sand, gravel, and admixtures (agents) undergoes chemical aggregation due to hydration reactions of cement particles, consumption of cement dispersants, and interparticle bonding. Physical aggregation due to attraction and collisions between particles progresses and fluidity is lost. For this reason, slump loss occurs in cement mixtures such as concrete and mortar. In particular, in such high-strength concrete compositions with a high concentration of cement particles, the distance between cement particles is small, and the probability of collision between particles is proportional to the particle concentration as well as interaction between particles due to consumption of cement dispersant. According to the agglomeration theory, the agglomeration rate is extremely fast and the slump loss is also large. Irrespective of chemical or physical agglomeration, if the aggregates of cement particles are redispersed using a cement dispersant, the fluidity of the cement mixture can be temporarily restored.
However, the hydration reaction of cement progresses further, and a gel of ettringite (commonly known as cementobacillus or calcium sulfoaluminate) is continuously produced, and the cement dispersant is added to the gel of ettringite, which is newly produced in the solution and on the cement particles. It is adsorbed or stored in new precipitated minerals, reducing the cement dispersant concentration in the solution. At the same time, collisions between cement particles also occur, and aggregation of cement particles progresses. For this reason, the fluidity of the system continues to decrease.
If the cement dispersant can be continuously supplied by some method, slump loss can be prevented. Therefore, the present inventors attempted to release a dispersant precursor in a sustained manner in a cement formulation. In other words, water-soluble salts function as dispersants upon addition and do not have sustained release properties, but dispersant precursors containing acid anhydrides in the molecule can release Ca, Na, K, and Mg in cement formulations. It is gradually hydrolyzed by metal ions such as, and a water-soluble salt having dispersibility can be continuously supplied. In other words, it is assumed that the hydrolysis reaction of the dispersant precursor progresses gradually, the dispersant is released in a sustained manner, and slump loss of the cement mixture can be prevented. The cement admixture used in the present invention includes a sustained release agent (A) made of a maleic anhydride copolymer, a naphthalenesulfonic acid formaldehyde high condensate water reducing agent, a sulfonated melamine resin water reducing agent, and a lignin sulfonic acid based water reducing agent. A sustained release drug (A) consisting of one or more water reducers (B) selected from a water reducer, a carboxylic acid water reducer, a styrene sulfonic acid water reducer, and a water reducer having a sulfone group and a carboxyl group.
and water reducing agent (B) in terms of solid content weight ratio of 2:98~
It is from 20:80. The present invention uses the cement admixture as cement 100.
Contains 0.1 to 2.0 parts by weight of solids based on parts by weight,
The water-cement ratio is 28% to 45% and the amount of entrained air is 5.
By setting it below %, the kneading slump value can be reduced.
12-24cm, slump loss is 6cm/60 minutes or less, and compressive strength is 400 after 91 days of standard underwater curing.
It has become possible to obtain a high-strength concrete composition with a strength of more than Kg/cm ² . The sustained release drug used in the present invention is a copolymer of maleic anhydride and another copolymerizable monomer, and has an average molecular weight of 500 to 50,000. Furthermore, it is also possible for this sustained release drug to have an ester, acid amide, or acid anhydride in its molecule. The average molecular weight of the copolymer used in the present invention is expressed as the weight average molecular weight determined by aqueous gel permeation chromatography using polystyrene sulfonic acid as a reference material. In the present invention, other polymerizable monomers copolymerizable with maleic anhydride include olefins having 2 to 8 carbon atoms, styrene monomers, and vinyl monomers. Specific examples of olefins having 2 to 8 carbon atoms include:
Ethylene, propylene, isobutylene, 1-butene, 2-butene, 1-pentene, 2-pentene,
1-hexene, cyclopentene, 2-methyl-1
-butene, cyclohexene, 2-methyl-1-pentene, 3-methyl-1-pentene, 4-methyl-1-pentene, 2-ethyl-1-butene, diisobutylene, etc., including straight-chain or branched olefins. It will be done. Specific examples of the styrene monomer include styrene, α-methylstyrene, vinyltoluene, chloromethylstyrene, and the like. Vinyl monomers include vinyl ethers such as methyl vinyl ether, ethyl vinyl ether, lauryl vinyl ether, and stearyl vinyl ether; acrylic acid, methacrylic acid, maleic acid,
Carboxylic acid monomers such as half esters of carboxylic acids such as citraconic acid, fumaric acid, itaconic acid, and crotonic acid, and dicarboxylic acids such as monomethyl maleate, monoethyl maleate, and monomethyl fumarate; itaconic anhydride, citraconic anhydride Acid anhydrides such as acids; monomers having hydroxyl groups such as allyl alcohol, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, polyethylene glycol mono(meth)acrylate, glyceryl (meth)acrylate; Monomers with sulfonic acid groups such as styrene sulfonic acid and vinyl sulfonic acid; meth) Acrylamide, half amide of maleic acid and monoethylamine, half amide of maleic acid and monopropylamine, etc., half amide of maleic acid and itaconic acid, amide type monomers such as vinylpyrrolidone, vinylcaprolactam, maleimide, etc. Body; dialkylaminoalkyl (meth)acrylates such as dimethylaminoethyl (meth)acrylate, diethylaminoethyl (meth)acrylate, dimethylaminopropyl (meth)acrylate, dialkylaminoalkyl (meth)acrylamides such as dimethylaminopropyl (meth)acrylamide , a monomer having an amino group such as vinylpyridine; and a monomer having an ester group such as allyl ester, vinyl acetate, and alkyl (meth)acrylate. Among the above monomers, lower olefins having 2 to 8 carbon atoms, styrene, and lower alkyl vinyl ethers having 1 to 4 carbon atoms are preferably used, and isobutylene is particularly preferably used. In the present invention, in order to produce concrete with a water-to-cement ratio of 28% to 45%, in addition to the sustained release agent, a naphthalenesulfonic acid formaldehyde high condensate water reducing agent, a sulfonated melamine resin water reducing agent, and a lignin sulfonic acid It is necessary to use one or more water reducing agents selected from water reducing agents, carboxylic acid type water reducing agents, styrene sulfonic acid type water reducing agents, and water reducing agents having sulfonic groups and carboxyl groups. Methods for adding the cement admixture used in the present invention to the cement mixture include dissolving it in kneading water and adding it to the cement mixture once kneaded. In addition, in the present invention, cement admixtures include naphthalene sulfonic acid formaldehyde high condensate water reducing agents, sulfonated melamine resin water reducing agents, lignin sulfonic acid water reducing agents, carboxylic acid water reducing agents, styrene sulfonic acid water reducing agents, and sulfonate water reducing agents. One or more water reducing agents selected from water reducing agents having a carboxyl group and a carboxyl group and a sustained release agent may be mixed in advance, or one may be mixed with the cement after one is mixed with the cement, or one of the water reducing agents may be mixed with the cement. The other may be added after kneading and kneading. The method of molding a hardened product using the high-strength concrete composition of the present invention can be carried out by charging the concrete composition into a formwork and compacting it with a vibrator, or by using a centrifugal molding formwork at 10G. , molding may be performed by applying centrifugal force for 3 minutes or more. If the centrifugal molding conditions are 10G for 3 minutes or less, the centrifugal moldability is insufficient and sufficient compaction performance cannot be obtained. It is also possible to add other cement additives, such as air entraining agents, fluidizing agents, waterproofing agents, expansion agents, glass fibers, steel fibers, fly ash, blast furnace slag, etc. [Effects of the Invention] As described above, the high-strength concrete composition of the present invention containing a cement admixture consisting of a combination of a sustained-release drug and a water-reducing agent can significantly improve slump loss, which has been considered difficult in the past. , which can facilitate quality control. Furthermore, when the concrete composition of the present invention is centrifugally molded in a centrifugal molding frame and then subjected to high temperature curing and/or high temperature and high pressure curing, a high-strength concrete hardened product with demolding compressive strength of 100 Kg/cm ² or more is obtained. The most characteristic point is that it can be manufactured, and this application discloses it for the first time in the present invention. As mentioned above, the reason why such characteristic performance can be imparted to concrete is
A sustained-release agent made of a maleic anhydride copolymer that is hydrolyzed by alkali in concrete to supply water-soluble substances, a naphthalene sulfonic acid formaldehyde high condensate water reducer, a sulfonated melamine resin water reducer, and lignin sulfone. Acid water reducing agent,
This is possible only by using a cement admixture that is combined with one or more water reducers selected from carboxylic acid water reducers, styrene sulfonic acid water reducers, and water reducers with sulfone and carboxyl groups. It is. Conventionally, due to concrete slump loss, etc., the formwork could not be filled sufficiently, resulting in defects and a high frequency of defective products, but the present invention significantly improves concrete slump loss, which was considered difficult in the past, and improves quality. By using a high-strength concrete composition that is easy to manage, it is possible to manufacture a high-strength concrete hardened body with few defects and good filling properties, improving the productivity and quality of piles, poles, pipes, etc. It is expected that this technology will greatly contribute to the improvement of technology, and the practical impact of this technology is expected to be extremely large. For example, there are two methods of pouring concrete into centrifugal molding frames, such as pump pressure feeding and filling methods. However, if pump pressure feeding is temporarily interrupted due to work lunch breaks, change of setup, mechanical failure, etc., if the interruption time is prolonged, the pumping The fluidity of the concrete in the piping decreases, and the pumping pressure increases rapidly when pumping is resumed.Furthermore, the fluidity of the concrete decreases in the centrifugal molding frame, resulting in poor compaction and filling properties.
It is expected that problems such as an increase in the probability of producing defective products will arise. However, the fluidity of the high-strength concrete composition of the present invention is kept constant,
Since a decrease in fluidity is prevented, sufficient compaction and filling properties are maintained even in the face of the above-mentioned troubles, and good results are expected in terms of quality control. [Example] Hereinafter, the present invention will be explained in more detail with reference to Examples. Example 1 A concrete composition was obtained using the cement, fine aggregate, coarse aggregate, and cement admixture shown below at the mixing ratio shown in Table 1. <Materials used> Cement: Ordinary Portland cement (specific gravity = 3.16) Fine aggregate: River sand from Kinokawa (specific gravity = 2.57) Coarse aggregate: Crushed stone from Takarazuka (specific gravity = 2.61) Cement admixture: Maleic anhydride and isobutylene in moles Ratio 1:
Using a sustained release drug consisting of isobutylene/maleic anhydride copolymer with a molecular weight of 400 to 80,000 obtained by copolymerization in step 1 and a naphthalene sulfonic acid formaldehyde high condensate water reducing agent, 90 parts by weight of the water reducing agent was added. Contains 10 parts by weight of a sustained-release drug.

[Table] The obtained concrete composition was mixed for 3 minutes using a tilting mixer, and then continued to be mixed with 4 revolutions for a predetermined time to evaluate the fluidity of the concrete. In addition, the fluidity of concrete is JIS A
This was done by measuring the slump value using the 1101 slump test. In addition, specimens for compressive strength measurement were collected 90 minutes later, and the compressive strength was measured 91 days after curing in standard water. Table 2 shows the results of concrete slump retention effect and compressive strength in systems in which the molecular weight of isobutylene/maleic anhydride copolymer was varied from 400 to 80,000.

[Table] As is clear from the experimental results shown in Table 2, in Experiment No. 3 using the product of the present invention, almost no slump loss occurred even after 90 minutes, and good strength development was observed. It is clear that the present invention is superior to these. In addition, in Experiment No. 2, which had a low average molecular weight, no slump retention effect was observed, while in Experiment No. 4, which had a high average molecular weight, the effect as a flocculant appeared immediately after kneading, and the fluidity decreased significantly. Example 2 A copolymer of isobutylene and maleic anhydride at a molar ratio of 1:1 as a sustained release drug, a naphthalene sulfonic acid formaldehyde high condensate water reducing agent, a sulfonated melamine resin water reducing agent, and lignin sulfonic acid as water reducing agents. A concrete composition was produced in the same manner as in Example 1, except that the cement admixtures shown in (a) to (f) below, which were prepared using a water reducing agent, were used, and the effect of preventing a decrease in fluidity was tested. The study was conducted in the same manner as in Example 1. The results are shown in Table-3. <Cement admixture> (a) Naphthalenesulfonic acid formaldehyde high condensate water reducing agent (b) Sulfonated melamine resin water reducing agent (c) Lignosulfonic acid water reducing agent (d) Naphthalene sulfonic acid formaldehyde high condensate 90 parts by weight and 10 parts by weight of a copolymer of isobutylene and maleic anhydride having an average molecular weight of 10,000. (e) A blend of 90 parts by weight of a sulfonated melamine resin water reducing agent and 10 parts by weight of a copolymer of isobutylene and maleic anhydride having an average molecular weight of 10,000. (f) A blend of 90 parts by weight of a ligninsulfonic acid water reducing agent and 10 parts by weight of a copolymer of isobutylene and maleic anhydride having an average molecular weight of 10,000.

[Table] *1: Solid content weight% relative to cement
As is clear from the experimental results shown in Table 3, No. 6, in which the amount of concrete admixture added was small, hardly achieved the initial dispersibility. On the other hand, the amount added
Experiment No. 7, which had a high content of 2.5%, showed a separated state, the concrete properties were poor, and sufficient strength could not be obtained. In addition, in Experiment No. 8 where the amount of air entrained in the concrete was large, the slump retention was good, but the entrained air became a defect and it was not possible to obtain sufficiently high strength. In experiments Nos. 12 to 14 using the products of the present invention, almost no slump loss occurred even after 90 minutes, and good strength development was observed. It is clear from these results that the present invention is superior.

Claims (1)

[Claims] 1. In a concrete composition consisting of coarse aggregate, fine aggregate, cement, water, and admixtures (agents),
A sustained release drug (A) made of a maleic anhydride copolymer with a weight average molecular weight of 500 to 50,000, a naphthalene sulfonic acid formaldehyde high condensate water reducing agent, a sulfonated melamine resin water reducing agent, a lignin sulfonic acid water reducing agent , one or more water reducing agents (B) selected from a carboxylic acid water reducing agent, a styrene sulfonic acid water reducing agent, and a water reducing agent having a sulfone group and a carboxyl group; Add a cement admixture with a solid content weight ratio of 2:98 to 20:80 to 100 parts by weight of cement to a solid content of 0.1 to 2.0.
parts by weight, the water-cement ratio is 28% to 45%, the slump value after mixing is 12 to 24 cm, the slump loss is 6 cm/60 minutes or less, and the entrained air amount is 5% or less, and standard underwater curing 91 The compressive strength of the material per day is 400Kg/
A high-strength concrete composition with less deterioration in workability, characterized by having a hardness of at least ^cm2 .