JPS6144744A - Admixing agent for hydraulic cement - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to an admixture for hydraulic cement or a hydraulic cement mixture, and more specifically to a high performance water reducing agent and a slump loss inhibitor used in concrete. It is related to.

In recent years, ultra-high strength concrete and fluidized concrete have attracted attention, and each is solidifying its unique position in the concrete field. The basis of these new concrete technologies is high performance water reducers.

A high performance water reducing agent is a type of chemical admixture, but its composition is different from that of conventional admixtures, and it has a high water reducing function, while having almost no setting retardation effect or air entrainment. Therefore, it can be used at a higher contamination rate than conventional water reducing agents.
It is also possible to reduce the amount of kneading water by ~30%.

[Conventional technology]

However, it has been recognized that this superior superplasticizer also has some drawbacks. The biggest problem is that when applied to fluidized concrete, there is a large change in consistency over time, so-called slump loss.

For this reason, in Japan, high-performance water reducing agents are added to concrete and mixed with agitation to obtain fluidized concrete at the site where concrete is used. It is necessary to carry out quality control, which requires huge labor costs, and when manufacturing fluidized concrete on-site, there are problems with the parking space for ready-mixed concrete trucks, the noise they generate, and the exhaust gas. Countermeasures have been desperately needed.

One of the measures to prevent slump loss is to add a high-performance water reducing agent in the form of solid lumps and take advantage of its gradual dissolution property, which seems to have already been put into practical use by the German company SKW. If drying costs and granulation costs are included, the admixture will inevitably be extremely expensive. Another proposed method for preventing slump loss is to repeatedly add a high-performance water reducer to concrete, but this method is cumbersome and impractical. Furthermore, one of the other measures to prevent slump loss is to use a retardant in combination, but this often does not sufficiently meet the pot life of about 80 minutes required for fluidized concrete, and also has an impact on concrete performance. Since the amount is so large, excessive care must be taken to control the amount added, which is not practical.

[Problem that the invention seeks to solve]

In view of the current state of technology, the present inventors believe that it is possible to produce fluidized concrete by adding a high-performance water reducing agent in a ready-mixed concrete plant, and to maintain fluidity due to slump loss during the transport time to the site, which takes at least about 90 minutes. We have conducted intensive studies on a high-performance water reducing agent that can prevent the decrease in water content while maintaining a constant fluidity, and as a result, we have arrived at the present invention.

[Means for solving problems]

The hydraulic cement admixture of the present invention is characterized by containing as an active ingredient a mixture consisting of 95 to 50 parts by weight of naphthalene sulfonic acid formaldehyde high condensate salt and 5 to 50 parts by weight of cyclodextrin.

The naphthalene sulfonic acid formaldehyde high condensate salt used in the present invention preferably has a degree of polymerization of about 3 to 100, and the components include naphthalene sulfonate, apricot formaldehyde, and alkylnaphthalene, phenol, anthracene, xylene, lignin, and creosote. It may also be a co-condensation product of an oil and a substituted aromatic compound such as a sulfonated product thereof.

Examples of cations forming water-soluble salts include elements such as Na, K, and Ca, amines such as monoethanolamine, jetanolamine, triethanolamine, and NH.

It is a series of non-reducing maltooligosaccharides, which can be obtained by allowing enzymes produced by certain microorganisms to act on starch.

Through a series of studies, the present inventors discovered that cyclodextrin surprisingly exhibits an extremely strong water-reducing effect on hydraulic cement that dextrin etc. do not have. Its effect is also significant, and it is impossible to utilize its water-reducing effect by adding it alone to hydraulic cement.

The present inventors have succeeded in solving this drawback by using the naphthalene sulfonic acid formaldehyde high condensate salt in combination. In the present invention, the mixing ratio of naphthalene sulfonic acid formaldehyde high condensate salt and cyclodextrin is 95 to 50 parts by weight, preferably 80 to 70 parts by weight.
parts by weight, the latter being 5 to 5 parts by weight, preferably 10 to 30 parts by weight
Parts by weight. If the cyclodextrin content is greater than the above-mentioned mixing ratio, the effect of retarding the hardening of the hydraulic cement will be significant, resulting in a practical-L problem, and if the cyclodextrin content is less than the above-mentioned mixing ratio, the slump loss prevention effect will be insufficient.

The admixture for hydraulic cement of the present invention may be used in powder form or in the form of an aqueous solution.

〔Effect of the invention〕

'The cement admixture of the present invention is normally used in an amount of about 0.1 to 2% by weight in terms of solid content based on cement, and its function is to improve the fluidity of concrete in its initial stage. and maintain fluidity for the approximately 80 minutes normally required.

[Example] The present invention will be described in more detail below by giving examples of the present invention.

Example 1 A predetermined amount of γ-cyclodextrin was dissolved in a 42% by weight aqueous solution of naphthalene sulfonic acid aldehyde high condensate sodium salt (manufactured by Maitini Kao Soap Co., Ltd.), and the solid content ratio in the aqueous solution was adjusted to 42% by weight. Admixture Sample A: 80 parts by weight of acid formaldehyde high condensate sodium salt, 10 parts by weight of γ-cyclodextrin
It was created.

Example 2 80 parts by weight of naphthalene sulfonic acid formaldehyde high condensate sodium salt, γ-
An admixture sample B containing 20 parts by weight of cyclodextrin was prepared.

Comparative Example 1 40 parts by weight of naphthalene sulfonic acid formaldehyde high condensate sodium salt, γ-
An admixture sample C containing 60 parts by weight of cyclodextrin was prepared.

Comparative Example 2゜Naphthalene sulfonic acid formaldehyde high condensate salt 4
A 2% by weight aqueous solution (Mighty: manufactured by Kao Soap Co., Ltd.) was used as an admixture sample.

Example 3. Concrete test (1) Mixed ingredients of concrete Mixed ingredients Cement: Ordinary Portland cement mixed with 3 types of fine aggregate:
Produced river sand for Oi, specific gravity 2.81, particle size 5 mm or less Coarse aggregate: Hard sandstone crushed stone, specific gravity 2.64, particle size 20 mm or less (2) Concrete mixing method and test method So that the amount of kneading is 40 mm. Then, using a tilting mixer with a capacity of 100 g, add coarse aggregate, fine aggregate, cement, water, and admixture (including cases where no admixture is used) at the same time. Mixing slump was measured for 3 minutes. The rotation speed of the mixer was set to 4 rpm, and the mixture was stirred for a maximum of 80 minutes. Slump was measured every 15 minutes. A specimen was prepared in 30 minutes and subjected to standard curing.

Test method Slump: j) Compliant with S A 1101 Compressive strength:
, JIS A 1132 and JIS A
110B (3) Test Results In addition to the results using the admixture of the present invention and the admixture of the comparative example, Table 1 shows the results when no admixture was used at all.

As is clear from the table, the high slump loss of the conventional method has been significantly improved, and sufficient fluidity can be maintained even after 80 minutes.

Furthermore, when the admixture of Comparative Example 1 was used, the concrete did not harden even after one day and night, and subsequent measurements were discontinued.

Claims (1)

[Claims] Naphthalene sulfonic acid formaldehyde high condensate salt 95
An admixture for hydraulic cement characterized by containing as an active ingredient a mixture consisting of ~50 parts by weight and 5 to 50 parts by weight of cyclodextrin.