JPH05132346A - Aqueous solution of hydraulic cement admixture - Google Patents

Abstract

PURPOSE:To obtain the title aqueous solution improved in stability by formulating an inorganic acid iron salt with a chelating agent capable of forming an iron chelate compound at a specified molar ratio to the iron. CONSTITUTION:An inorganic acid iron salt containing 0.2-10wt.% of iron (e.g. FeSO4) is first incorporated with (A) 0.05-0.5mol per mol of the iron of a chelating agent capable of forming an iron chelate compound such as sodium gluconate and (B) an appropriate amount of a pH adjustor such as triethanolamine, and the resulting mixture is then dissolved in water into the objective stable aqueous solution. Thence, this solution, an admixture, is added to a cement composition comprising (1) hydraulic cement like Portland cement, (2) aggregate and (3) water at specified proportion so as to be >=0.001 (pref. >=0.01)wt.%, based on the cement, in the iron content of the admixture to prepare mortar, which is, in turn, cured to afford a cement-cured product of high initial compressive strength.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hardening accelerator for promoting the development of initial strength of a hydraulic cement composition.

[0002]

2. Description of the Related Art Conventionally, in order to promote the development of initial strength in the construction at low temperature in winter, or to increase the rotation rate of the mold when the mold is used for molding hardened cement. A hardening accelerator that accelerates the hydration reaction of cement is added to uncured cement.
Calcium chloride, which has a remarkable effect and is inexpensively available, has been most widely used as such a hardening accelerator for cement.

However, from the viewpoint of the durability of concrete, since the regulation of the total amount of chloride has been strengthened since 1987, calcium chloride cannot be practically used for reinforced concrete. As chlorine-free type curing accelerators that should be substituted for this, there have been proposed a large number of alkali metal or alkaline earth metal sulfates, thiocyanates, thiosulfates, carbonates, nitrates, nitrites and the like.

For example, a cement composition containing thiocyanate and thiosulfate in combination (JP-A-60-21840), a cement composition containing calcium nitrite and thiocyanate in combination (JP-A-61-141649), powder A cement composition using amide sulfonic acid (JP-A-1-176255), a cement composition using an amide sulfonate and a water-soluble amino alcohol (JP-A-1-46164) and the like are known.

[0005]

However, none of these conventional ones has a sufficient effect of promoting hardening of cement. It is desired to provide a hydraulic cement admixture aqueous solution which does not contain chlorine ions and has an excellent cement hardening accelerating property.

[0006]

The hydraulic cement admixture aqueous solution of the present invention has a ratio of 0.05 to 0.5 mol of a chelating agent capable of forming an iron chelate compound to 1 mol of iron in an inorganic acid salt of iron. It is characterized in that it contains an inorganic acid salt of the iron in a dissolved state and a chelating agent. Examples of the inorganic acid salt of iron used in the present invention include ferrous sulfate, ferric sulfate,
Examples thereof include ferric nitrate, iron sulfite, iron phosphate, iron thiocyanate, iron thiosulfate, iron fluoride, iron silicofluoride, and iron borate. Particularly, ferrous sulfate, ferric sulfate, and ferric nitrate. 2 Iron or the like is preferable.

As the chelating agent used in the present invention,
A generally known chelating agent that forms a chelate compound with iron can be used, and sodium citrate, sodium gluconate, potassium sodium tartrate and the like are particularly preferable. The hydraulic cement admixture aqueous solution of the present invention is an aqueous solution of the above-mentioned iron inorganic acid salt and a chelating agent, and the chelating agent 0.05 to 0.5 mol, relative to 1 mol of the iron content derived from the iron inorganic acid salt, It is preferably contained in a ratio of about 0.1 to 0.3 mol. And this aqueous solution is 0.2 to 10% by weight as iron content derived from the inorganic acid salt of iron, preferably
It has an iron acid salt concentration of 1 to 3% by weight and a chelating agent concentration of 0.05 to 5% by weight, preferably about 0.2 to 2% by weight.

The hydraulic cement admixture aqueous solution of the present invention is
Other additives may be contained as long as the object of the present invention is achieved. Examples of preferred additives include water reducing agents, AE agents, AE water reducing agents, and high-performance AE water reducing agents that have been conventionally used as cement admixtures. In order to obtain a uniform and stable aqueous solution by mixing the hydraulic cement admixture aqueous solution of the present invention with the above-mentioned preferred additives, it is desirable to make the pH of the hydraulic cement admixture aqueous solution neutral. To adjust the pH of the hydraulic cement admixture aqueous solution to be neutral, it is preferable to add a water-soluble amino alcohol to the aqueous solution.

As the water-soluble amino alcohol used, monoethanolamine, diethanolamine, triethanolamine, N, N-diethylethanolamine, N-
(Β-aminoethyl) ethanolamine, N-methylethanolamine, N-methyldiethanolamine or a mixture thereof and the like are exemplified, and particularly triethanolamine,
Monoethanolamine, diethanolamine and the like are preferable.

The cement to which the hydraulic cement admixture aqueous solution of the present invention is applied causes hardening by a hydration reaction, and for example, ordinary Portland cement, early-strength Portland cement, moderate heat Portland cement,
Sulfuric acid heat resistant Portland cement, fly ash Portland cement, silica cement, blast furnace cement, white cement, super early strength Portland cement, jet cement and the like. Further, the aqueous solution of the hydraulic cement admixture of the present invention can be applied to ordinary hydraulic gypsum and the like.

[0011]

The cement composition containing the inorganic acid salt of iron exhibits a high initial strength upon hardening, and the inorganic acid salt of iron remarkably promotes the development of the initial strength of the hydraulic cement composition. It was found. However, an aqueous solution prepared by dissolving the above-mentioned inorganic acid salt of iron in water at a high concentration is likely to cause precipitation during long-term storage and is difficult to supply as a stable cement admixture aqueous solution. However, it has been found that when a small amount of the above chelating agent is dissolved in this aqueous solution of an inorganic acid salt of iron, a uniform solution is retained and a stable aqueous solution can be obtained without causing precipitation even after long-term storage. It was Possibly the added small amount of chelating agent forms a stable complex with some iron ions in this aqueous solution and prevents the precipitation of the rest of the dissolved iron mineral acid salt. it is conceivable that.

However, if the amount of the chelating agent added to this aqueous solution is 0.05 mol or less with respect to 1 mol of the iron component derived from the inorganic acid salt of iron in the liquid, the above stabilizing effect is not sufficiently exhibited. On the contrary, if the amount of this chelating agent added is more than 0.5 mol per 1 mol of iron derived from the inorganic acid salt of iron in the liquid, the resulting aqueous solution is stable, but when this is mixed with cement. Further, it is not preferable because it inhibits the hardening acceleration property of cement. It is desirable that the amount of this chelating agent be as small as possible within the range of stabilizing the above-mentioned aqueous cement admixture containing an inorganic acid salt of iron.

Further, the admixture aqueous solution of the present invention may be added in the vicinity of neutral
When adjusting to pH and using amino alcohol
The addition amount of the chelating agent required to obtain an equally stable liquid is a fraction of that required when adjusted with NaOH or the like. When the content of iron derived from the inorganic acid salt of iron in the hydraulic cement admixture aqueous solution of the present invention exceeds 10% by weight, the aqueous solution exceeds the saturated solubility and precipitation is liable to occur. This is not preferable because the concentration of the inorganic iron acid salt having performance is reduced.

[0014]

【Example】

Example 1 Ferrous sulfate and ferric sulfate as inorganic acid salts of iron, sodium gluconate (SGN) as a chelating agent, sodium hydroxide as a pH adjusting agent, and triethanolamine (TEA)
And monoethanolamine (MEA) were prepared and dissolved in water to prepare an aqueous admixture solution shown in Table 1.

Table 1  Admixture Admixture Admixture Iron inorganic acid salt Chelating agent pH stabilitySign And concentration (%) And concentration (%) Regulator pH   A FeSO_Four 10 None ─── ── Precipitation within 1 day B FeSO_Four 10 SGN 2 ─── ── Stable for 3 months or more C FeSO_Four 10 None NaOH 3 Precipitation within 1 day D FeSO_Four 10 None NaOH 7 Precipitation within 1 day E FeSO_Four 10 None TEA 4 Precipitation within 1 day F FeSO_Four 10 None TEA 7 Precipitation within 1 day G FeSO_Four 10 None MEA 4 Precipitation within 1 day H FeSO_Four 10 None MEA 7 Precipitation within 1 day I FeSO_Four 10 SGN 2 TEA 6 Stable for over 3 months J FeSO_Four 10 SGN 10 NaOH 6 Stable for over 3 months K Fe₂(SO_Four)₃10 None NaOH 2 Precipitation within 1 day L Fe₂(SO_Four)₃10 None NaOH 7 Precipitation within 1 day M Fe₂(SO_Four)₃10 None TEA 4 Precipitation within 1 day N Fe₂(SO_Four)₃10 None MEA 4 Precipitation within 1 day OFe₂(SO_Four)₃10 SGN 2 TEA 4 Stable for over 3 monthsP Fe ₂ (SO ₄ ) ₃ 10 SGN 2 MEA 4 Stable for 3 months or more However,% in the table represents% by weight. Then mix these
Store the agent solution in a closed container and keep it at 20 ° C to
Stability was observed. The results are shown in Table 1.
is there.

The results in Table 1 show that the aqueous solution of hydraulic cement admixture containing ferrous sulfate or ferric sulfate and sodium gluconate is a homogeneous and stable aqueous solution which does not cause precipitation for a long period of time. It is shown that. In addition, the admixture I shown in Table 1 above and a separately prepared commercially available 35% by weight
The admixture was prepared by mixing the melamine-based high-performance water reducing agent of 1. in equal weight, and the stability was tested in the same manner as above. The stability was 3 months or more.

Example 2 A mortar was prepared by adding an admixture to a mixture of ordinary Portland cement 1: river sand 2: water 0.5 in an amount to be added to the cement shown in Table 2, and the mortar was prepared in a humidity box at a temperature of 5 ° C. After curing for a day, a test for measuring the compressive strength was conducted. Experiments No. 1 to 6 shown in Table 2 were conducted.

Table 2 Experiment No. Admixture and its addition amount (%) Compressive strength (Kgf / cm ² ) 1 None 72 2 Admixture aqueous solution I 0.5 108 3 Admixture aqueous solution O 0.5 104 4 Ca (SCN) ₂ aqueous solution 1.0 98 5 NaSCN aqueous solution 1.0 99 6 CaCl ₂ aqueous solution 1.0 91 However, the admixtures I and O in Table 2 are as shown in Table 1. No. 4 has a separately prepared 10 wt% Ca (SCN) ₂ aqueous solution, No. 5 has a separately prepared 10 wt% NaSCN aqueous solution, and No. 6 has a separately prepared CaCl ₂ aqueous solution. 24 wt% and SG
An aqueous solution containing 1.5 wt% N and 1.2 wt% TEA was used.

No. 1 is a comparative example in which no additive is added.
o.2 to 3 are examples of the present invention, and Nos. 4 to 6 are comparative examples in which a conventional admixture is added. Looking at the compressive strength in Table 2, the admixture containing ferrous sulfate or ferric sulfate together with sodium gluconate and triethanolamine has a lower addition amount than the conventional curing accelerator. Nevertheless, it is shown that it gives a remarkably high initial strength.

[0020]

As shown in the examples, according to the present invention,
A uniform and stable hydraulic cement admixture aqueous solution that does not cause precipitation for a long period of time is obtained. The cement composition using the hydraulic cement admixture aqueous solution of the present invention exhibits remarkably high initial strength. Such a cement hardening accelerating effect is obtained by adding the hydraulic cement admixture aqueous solution of the present invention to the cement as iron content derived from the inorganic acid salt of iron in the solution, which is 0.001% by weight or more, and preferably 0.01% by weight or more with respect to the cement. It can be fully obtained. However, even if it is added in a large amount of 1% by weight or more, the promotion effect is not improved and the cost becomes high.

The hydraulic cement admixture aqueous solution of the present invention is
By a conventional method, it can be used as a cement kneaded product in any form of cement paste, mortar and concrete mixed with cement, water, fine aggregate, coarse aggregate and the like. And these kneaded materials can be applied by a usual method.

Claims (1)

[Claims] 1. An iron inorganic salt of an iron salt and a chelating agent are contained in a ratio of 0.05 to 0.5 mol of a chelating agent capable of forming an iron chelate compound with respect to 1 mole of iron in the iron inorganic salt. A stable hydraulic cement admixture aqueous solution characterized by: