JPS63100047A - Admixing agent for concrete composition - Google Patents

Abstract

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

Description

DETAILED DESCRIPTION OF THE INVENTION Fields of Application on Single Leaves - This invention relates to admixtures for concrete compositions, which are added to concrete for the purpose of increasing the early strength of concrete containing water reducing agents. This article relates to early-strengthening agents.

-Prior art- Adding a water reducer when producing concrete can reduce the amount of water required to obtain the same slump, and this can give concrete various improvement effects. is widely used. On the other hand, if the early strength of concrete (compressive strength 3 to 7 days after concrete pouring) is high, the time required from pouring concrete to removing formwork will be shorter, shortening construction period and reducing construction costs. Therefore, there is a desire to increase the early strength as much as possible.

However, components that reduce water in water reducers, such as geninsulfonates and oxycarboxylate salts, have the effect of retarding the initial setting rate, so adding water reducers increases the early strength of concrete. The problem was that I couldn't do it. Therefore, in the past, a reduction in early strength due to the water reducing agent was prevented by jointly using a water reducing agent and an early strength agent that has the effect of increasing the initial setting rate.

Problems to be Solved by the Invention - Calcium chloride is widely known as this type of early strengthening agent, but it has the disadvantage that chlorine ions in calcium chloride corrode the reinforcing bars in concrete, so in recent years it has been used as an early strengthening agent. use must be avoided or restricted;
Therefore, there is a strong need for an early-strengthening agent that has performance equivalent to or better than calcium chloride and does not contain chloride ions.

The present invention has been intensively researched in response to the above-mentioned demands, and an object of the present invention is to provide a new early-strengthening agent that does not contain chloride ions.

Means for Solving Problems One or more admixtures for concrete compositions of the present invention are selected from the group consisting of ammonium salts of hydrobromic acid and bromides of alkali metals and alkaline earth metals. It contains a bromine compound as an active ingredient, and more preferably, the content of the active ingredient is 0.01 to 0.4% by weight based on the weight of cement in the concrete,
Furthermore, the content of alkanolamine used together with the above-mentioned active ingredients is adjusted to o, o to the cement weight in concrete.
os~0.043! It is expressed as i amount percent.

Here, alkanolamine is a compound having a structure in which 1 to 3 aliphatic alcohols are bonded to a nitrogen atom (the bond is a carbon-nitrogen bond), such as monoethanolamine, jetanolamine, triethanolamine, etc. and so on.

In addition, the most common means of adding bromine compounds to concrete at a predetermined content ratio is to add them during concrete mixing, but they can also be added by post-addition method, or premixed into concrete materials before mixing. good. Further, it is also possible to use it in combination with various other admixtures such as an AE agent (air entraining agent) and fly ash.

Among the bromine compounds that are the active ingredients of the admixture according to the present invention, calcium bromide, sodium bromide, and potassium bromide were selected and compared with conventionally known calcium chloride. Ordinary Portland cement was used as the cement, and F, M, 2°0 sand with a specific gravity of 2.55 was used as the fine aggregate.
A test was conducted in which mortar was produced having a composition of 50% by weight of water and cement and 1:2 by volume of cement and sand.

The results are shown in Table 1.

Table 1 Plain -100 CaBrz O, 1) 1) NaBr 0.1 109KBr
0.1 108CaC1z O,
21) 0 The amount added is based on the weight of cement in the mortar and is expressed in % by weight.

As is clear from the above table, it can be seen that all of the bromine compounds according to the present invention have comparable compressive strengths compared to calcium chloride at 1/2 the amount added. Among them, it is clear that calcium bromide has particularly excellent early-strengthening effects.

Table 2 shows the amount of calcium bromide added and the amount of mortar added.
This study investigated the relationship between compressive strength and compressive strength after several days.

Table 2 Plain -100 CaBrz O, 0251) 3 CaBrz O, 051) 5 CaBrz O, 101) 6 CaBrz O, 151) 6 CaBrz O, 201) 8 CaBrz O, 40120 Calculate the amount of calcium bromide added from the table above. It can be seen that as the compressive strength increases, the compressive strength also gradually increases. Note that in Tables 1 and 2, the difference in compressive strength after 3 days when 41% calcium bromide O was added is due to the difference in materials.

-Example- Test results when calcium bromide having such an early-strengthening effect was actually used in concrete are shown below.

1 Test conditions 1 Cement 320 kg (Lotl), Sand 841 kg (32
6J) and 939kg of aggregate (35W) with a maximum aggregate size of 25W.
3J), 210 kg of water is required to obtain concrete with a slump (SL) value of 18 cm, and the resulting concrete is designated as plain (sample 1).

Next, when adding 1% of AEJ water agent to the cement weight in the above concrete composition, the amount of water required to obtain the same slump value is 185 kg, and the water reduction rate is 12%.
concrete is obtained (sample ■).

Furthermore, 0.
A sample to which 1% calcium bromide was added was designated as sample M, and a sample to which 0.04% triethanolamine was further added to the cement weight was designated as sample (2). Samples ■ and ■ are comparative samples, and sample ■ is sample H with the addition of conventionally known calcium chloride and triethanolamine at 0.2% and 0.04% based on the cement weight, and sample ■
Sample (2) was prepared by adding only 0.2% calcium chloride to the cement weight.

-Test results- Table 3 First issue End 3rd 7th 28th II +20 +20 135 126 1
)5I[1-10-101461301)4TV
-25-301671501)6V -25-25
1621461) 5MI O-51431341
)5 In the above test, a standard lignin-based AE water reducing agent was used.

As is clear from the table above, the sample (sample ■) in which calcium bromide was added at 0.1% based on the cement weight was treated with the AEfIi water agent for 30 minutes compared to the sample (■) in which the AE water reducer was added. The concrete setting start and end times are reduced by 10 minutes for the non-concrete plain (Sample I). In addition, sample (2), in which 0.04% of triethanolamine was added to sample (2), was compared to sample (2), in which 0.2% of calcium chloride and 0.04% of triethanolamine, which were conventionally known early-strengthening agents, were added. When compared, they are superior in setting completion time and early strength, and can be fully put to practical use. Furthermore, since the purpose can be achieved with the amount of calcium bromide used being 1/2 of the amount of calcium chloride used, the corrosiveness of reinforcing bars, etc. can be improved as much as possible.

- Effect of the invention 1 One or more bromine compounds selected from the group consisting of ammonium salts of hydrobromic acid and bromides of alkali metals and alkaline earth metals, which are the active ingredients of the admixture according to the present invention, are added to concrete. When added to concrete, it increases the initial setting speed of the concrete and prevents early strength loss due to the water reducing agent, reducing the time required from pouring concrete to removing formwork, shortening construction period and It is possible to save construction costs. As for the bromine compound in the admixture according to the present invention, it can be seen from Table 2 that as the amount added increases, the compressive strength after 3 days also increases. However, in practice, it is 0.01 to 0.0% relative to the weight of cement in concrete.
It is best to add 4% by weight, and in particular, as can be seen from Table 3, if it is used at 0.1% based on the weight of cement in concrete, the compressive strength after 3 days will be 167%.
Therefore, the compressive strength after 3 days, which has been considered as a standard, is 1
Since it exceeds 60, it is possible to achieve that purpose.

Furthermore, if it is used in combination with a water reducing agent that has various useful effects, it is possible to improve the delayed action, which is a drawback of water reducing agents, and to fully demonstrate the usefulness of the water reducing agent.

In addition, the admixture according to the present invention does not contain chlorine ions as a component, and has the same early strength effect on concrete with only half the amount of calcium chloride used in the past. Corrosion of the reinforcing steel inside can be prevented as much as possible. Furthermore, if an alkanolamine such as triethanolamine is added, a synergistic effect can provide a better early strength effect.

Claims (3)

[Claims] (1) An admixture for concrete compositions containing as an active ingredient one or more bromine compounds selected from the group consisting of ammonium salts of hydrobromic acid and bromides of alkali metals and alkaline earth metals. (2) The content of the active ingredient is 0.01 to 0.4 percent by weight based on the weight of cement in the concrete.
An admixture for concrete compositions according to claim 1. (3) The admixture for concrete compositions according to claim 2, which contains an alkanolamine in an amount of 0.005 to 0.04 weight percent based on the weight of cement in the concrete together with the above-mentioned active ingredient.