JPH0222022B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a method for producing fluidized concrete,
In particular, the present invention relates to a method for producing fluidized concrete containing ready-mixed concrete that has improved freeze-thaw resistance by entraining stable air that does not change over time in concrete. [Conventional technology] In recent years, demands for concrete have shifted to improving workability and emphasizing quality, but with the spread of pump construction methods and deterioration in the quality of aggregate, there has been strong interest in fluidized concrete as a countermeasure. ing. Fluidized concrete, which is commonly used today, is made by transporting concrete (base concrete) produced in a ready-mixed concrete plant to the casting site, where a fluidizing agent is added to increase its fluidity, and the concrete is poured using a pump. is the current situation. This type of so-called field-added fluidizing agent is mainly a combination of a high-performance water reducing agent and an AE agent, but the method of making fluidized concrete on-site requires a Problems with work efficiency such as the time and effort required to guide the mixer truck at the place where the superplasticizer is added, the effort and cost of controlling the quality of concrete before and after adding the superplasticizer, and the problem of traffic congestion and high-speed agitation. There are many problems such as urban problems such as noise. Despite these problems, the method of adding superplasticizers on-site was used because, when added to ready-mixed concrete, the problem of slump reduction that occurs during transport from the plant to the site in a mixer truck was avoided. This is because the issue could not be resolved. However, recently, slump loss-reducing fluidizers that reduce this slump drop and enable plant addition, so-called plant-added fluidizers, have begun to be put on the market. As this type of fluidizing agent, a high performance water reducing agent combined with a retardant such as a special lignin sulfonate or a polycarboxylate salt, or a polycarboxylate alone system are often used. Although plant-added plasticizers do have less slump drop and can be added to plants, they pose the problem of air loss. That is, a problem has arisen in which the amount of air decreases while concrete is being transported to a construction site using a mixer truck, and as a result, it is feared that the freeze-thaw resistance will deteriorate. Therefore, it is desired that the amount of air in concrete is stable and does not change over time. Generally, the amount of air gradually decreases after kneading, resulting in poor stability. Even in thighs that have been entrained with air using an AB agent, the amount of air decreases over time. If the amount of air is small, durability against freezing and thawing will be reduced. Moreover, if the air content is high, the compressive strength will decrease. Therefore, it is important that the amount of air is appropriate and that it is stable after kneading (small change over time). Conventional naphthalene sulfonic acid fluidizers have a foam-breaking effect that makes it impossible to introduce effective bubbles that are resistant to freezing and thawing even when using ordinary AE agents (anionic and nonionic). It was difficult. To this, Special Publication No. 58-5862 and Special Publication No. 58-5863 were issued.
No. 58-5864 of the Japanese Patent Publication No. 58-5864, inventions have been made in which cationic surfactants and amphoteric surfactants are added to introduce air bubbles that have freeze-thaw resistance. The effect of this on concrete was determined, and changes in the amount of air in concrete over time and stability were not taken into account. [Problems to be Solved by the Invention] The key point of the present invention is to stabilize the amount of air introduced into concrete and reduce changes over time. Air loss in plant-added superplasticizers is thought to be mainly caused by large air bubbles introduced from special lignin sulfonates and polycarboxylate salts, which are retardants contained in the superplasticizer. Immediate AE agents are primarily focused on introducing fine air bubbles into concrete, while plant-added superplasticizers are primarily focused on eliminating slump loss. Therefore, it is assumed that the introduced bubbles are accompanying bubbles, and air loss occurs because they are not fine bubbles like the AE agent. There are some auxiliary AE agents used in conventional high-performance water reducers and superplasticizers that have poor air entrainment properties.
It is unstable over time and the amount of air decreases over time. On the other hand, antifoaming agents are sometimes used on concrete (such as tributyl phosphate) simply to reduce the amount of air; Yes, it is not intended to stabilize the amount of air. [Means for Solving the Problem] As a result of intensive research into this problem, the present invention has developed an AE agent and a fatty acid ester-based air stabilizer, a natural They discovered that a stable amount of air can be maintained by using a fatty acid polyalkylene glycol ester antifoaming agent (hereinafter referred to as an air stabilizer). [Function] That is, by adding an air stabilizer, unstable large air bubbles are selectively removed, stable fine air bubbles are maintained by the AE agent, and stability of the air bubbles over time is obtained. When an air stabilizer is used in combination, the amount of AE agent used must be 2 to 8 times greater than when used alone. High-performance water reducing agents and fluidizing agents used in the present invention include formalin condensates of naphthalenesulfonic acid or alkyl group-substituted naphthalenesulfonic acids, formalin cocondensates of naphthalenesulfonic acid and ligninsulfonic acids, and sulfonated products of melamine-formalin condensates. In addition, examples include those containing special lignin sulfonic acid derivatives and polycarboxylic acid salts. The addition rate of these to cement is
0.15-2.5% is suitable. As the AE agent, amphoteric surfactants and anionic surfactants can be used. The amount of air stabilizer added is 0.0001% to 0.01% based on cement. If it is less than 0.0001%, it will have little effect, and if it exceeds 0.01%, the amount of AE agent required will increase, making it uneconomical. Preferably, it is added in an amount of 0.0005% to 0.005% based on cement. The ratio of air stabilizer to AE agent is AE
A ratio of 1 part by weight of air stabilizer to 15 to 150 parts by weight of agent is preferred. The high-performance water reducing agent, superplasticizer, AE agent, and air stabilizer to be added to the base concrete in the present invention are as follows:
They may be added simultaneously or separately. Further, although the method of the present invention is suitable for a fresh-complant addition type that reduces slump loss, it can also be used for an on-site addition type. [Example] The formulation of the base concrete is as shown in Table 1.

[Table] Additives shown in Table 2 were added and kneaded, and the concrete performance was evaluated. Sunflow FBF (trade name) used as a fluidizing agent is a fluidizing agent that reduces slump loss by blending a formalin cocondensate of naphthalenesulfonic acid and modified ligninsulfonic acid with a ligninsulfonic acid derivative that has undergone special chemical treatment. It is.

【table】

[Table] Concrete test is slump (JIS A 1101),
Based on air content (JIS A 1128) and freeze-thaw resistance (ASTMC-666 relative dynamic elastic modulus after 300 cycles). [Effects of the invention] As shown in Table 2, the combined use of an AE agent and an air stabilizer in a high-performance water reducer/plasticizer reduces the change in air content over time, making freeze-thaw resistance economically stable. improved.

Claims (1)

[Scope of Claims] 1. A ready-mixed compost characterized in that a high performance water reducing agent/plasticizer is used in combination with an AE agent and an antifoaming agent of a fatty acid ester type or a natural fatty acid polyalkylene glycol ester type as an air stabilizer. Method for producing additive fluidized concrete. 2 Adding high-performance water reducers and superplasticizers to cement
The method for producing fluidized concrete according to claim 1, wherein the amount of additive is added in the range of 0.15 to 2.5%. 3 Air stabilizer 0.0001 to 0.01% to cement
Claims 1 or 2 added within the scope of
Method for producing fluidized concrete as described in Section 1. 4 Claims 1 to 3 in which 1 part by weight of air stabilizer is added to 15 to 150 parts by weight of AE agent
A method for producing fluidized concrete according to any one of the following paragraphs.