JPS6256345A - Accelerator for 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] (Industrial application field) The present invention relates to an quick setting agent for cement.

(Conventional technology and problems) In recent years, a new tunnel construction method, the NATM construction method, has become established, and the amount of shotcrete construction is increasing.It is essential to add a quick setting agent for cement to this shotcrete method. Alkaline aluminate salts and alkali carbonate salts are known as quick-setting agents.For example, there are powder quick-setting agents whose main ingredient is a powder mixture of sodium aluminate and soda carbonate, and potassium aluminate and potassium carbonate. There are commercially available liquid quick-setting agents whose main component is a mixed aqueous solution of While it is supplied by a sprayer, it is pumped in the form of powder until it joins with the pumped water from another system near the nozzle tip, which may generate dust that harms the working environment or mixes unevenly with the quick setting agent. In addition, there is a risk that the moisture contained in the aggregate, the cement, and the quick-setting agent may react and cause rIIM of the yarn path, so strict management of materials, etc. is necessary.
There was a desire for an additive that would avoid the above-mentioned drawbacks but would be effective in further improving the rapid setting performance.

However, aqueous solutions of alkali aluminates are chemically unstable and aluminum hydroxide crystals tend to precipitate during storage. To prevent this, gluconic acid or its salts, tartaric acid or its salts, etc. are added as stabilizers. USP 2
, 345, 134) is often performed.

In such cases, there is a problem in that when other quick-setting agents are added, the performance of the alkali aluminate as a stabilizer or the accompanying performance as a quick-setting agent is often impaired.

(Object of the Invention) The present inventors have conducted various studies in order to take advantage of the advantages of liquid quick-setting agents and still improve their quick-setting performance, and as a result they have arrived at the present invention. The purpose of Wood RflA is to provide an alkali aluminate-alkali carbonate liquid quick-setting agent that further improves the quick-setting performance even in the presence of a stabilizer that prevents precipitation of aluminum hydroxide.

(Structure of the Invention) The present invention is a quick-setting agent for cement, characterized in that jetanolamine and an alkali tetraborate salt are blended into an aqueous solution containing an alkali aluminate and an alkali carbonate as main components.

Examples of the alkali aluminates and alkali carbonates include lithium salts, sodium salts, and potassium salts, and potassium salts are preferred in view of their solubility and viscosity. The mixing ratio of alkali aluminate and alkali carbonate to water is, for example, 10 to 20% potassium aluminate to potassium oxide.
In order to improve rapid setting performance and workability, it is desirable to adjust the content of aluminum oxide to 5 to 15% and potassium carbonate to 15 to 30%.

The blending amount of the jetanolamine is preferably 0.1 to 5 [gi%, particularly 0.5 to 3% by weight, based on the aqueous solution. ,
Jetanolamine becomes easier to separate.

The above-mentioned alkali tetraborate salt is a lithium salt.

There are sodium salts, potassium salts, etc., but since the quick-setting agent is a highly concentrated alkali salt, the effect will not change even if you mix either of them. Therefore, from the economic point of view, it is desirable to use sodium west borate decahydrate, which is commercially available as borax.

The blending ratio of the alkali tetraborate salt is preferably 0.1 to 5% by weight, preferably 0.5 to 2% by weight as a hydrate, based on the aqueous solution. If it exceeds 5% by weight, the quick-setting performance will decrease.

The quick-setting agent of the present invention may contain stabilizers such as the aforementioned gluconic acids and tartaric acids, if necessary, such as when long-term storage is required.

The reason why jetanolamine is selected as a component of the liquid quick-setting agent in the present invention is as follows. Examples of this type of ethanolamine are monoethanolamine and jetanolamine.

Triethanolamine is generally known as an ingredient for rapid setting.

For example, it has been proposed to blend polyhydric alcohol as an alkali aluminate-alkali carbonate liquid quick-setting agent that does not contain stabilizers such as gluconic acid (Japanese Patent Laid-Open No. 59-1
No. 56946). However, what is mainly discussed in this specification is triethanolamine, and jetanolamine is not discussed.

This seems to be based on the common general knowledge in the industry that jetanolamine has inferior rapid setting performance than triethanolamine, but the present inventors unexpectedly discovered that an alkali aluminate-alkali carbonate liquid containing a stabilizer Regarding binders, we have found that jetanolamine has much superior performance as an quick-setting agent when added to cement, compared not only with triethanolamine but also with monoethanolamine.

The present invention was completed based on the finding that by further adding an alkali tetraborate salt to jetanolamine, a rapid setting performance superior to that of jetanolamine alone can be obtained.

The product of the present invention can be used by dissolving it in advance in mixing water for shotcrete, by press-mixing it into mixing water using a pump, or by injecting only the quick-setting agent into the nozzle tip. In normal spraying work, the amount used is 1 to 10% by weight, preferably 4 to 6% by weight, based on the amount of cement.

The cement used in the present invention is preferably Portland cement, but mixed cements such as furnace cement, silica cement, and fly ash may also be used.

The present invention will be specifically explained below with reference to Examples.
is based on weight.

Example 1 Potassium aluminate (2013% in aqueous solution).

Solution A is an aqueous solution containing ANzO (39%), potassium carbonate 25%, and sodium gluconate 0.2%.

Jetanolamine θ~5% with respect to this A solution.

A liquid quick setting agent was made by adding 00 to 2% of porium.

In order to compare the quick setting performance of this liquid quick setting agent, 2.0 OOQ of ordinary Portland cement and 6.0 OOQ of river sand were used. OOOg(F,
M, 2,6. 5% surface level), 45% water to cement, and 4 to 6% liquid quick-setting agent to cement, mixed for about 15 seconds, then quickly packed into a mold, and after 1 minute, a broctor penetration resistance test ( ASTM C463-63T
), the start (500PS I) and the end (4000PS I)
PSI) was measured. The results are shown in Table-1 and Table-2. Note that the test was conducted at 20°C.

Table 1 (without addition of quick setting agent vs. cement ratio: 4%) Table 2 (addition of quick setting agent vs. cement ratio: 6%) * indicates a comparative example.

Example 2 In order to see the effect on the compressive strength of a liquid quick-setting agent created by adding 3% jetanolamine and 1% borax to liquid A in Example 1, a strength test was conducted on JISK5201-9 cement. I did it.

Transparent Portland Semen l-600 (+, River Sand 1800
g (F, M, 2, 6. Surface water rate 5%), mix 45% water to cement, 6% liquid quick setting agent to cement, mix for about 10 seconds, then quickly 4x4x 16. Packed into a double formwork, and after demolding, the temperature was 20℃ and the humidity was 9℃ until the specified material age.
It was cured at 0%. In addition, tests were also conducted using only liquid A and when no quick-setting agent was added. The results are shown in Table-3. Please note that only liquid A is available.

Tests were also conducted in the case where no accelerating agent was added.

Table-3 Compressive strength of mortar ■Item: Comparative example In liquid A of Example 1, monoethanolamine (MEA),
Jetanolamine (DEA).

Three types of liquid quick setting agents were prepared by adding 3% triethanolamine (TEA). In order to compare with these liquid quick-setting agents, each of these quick-setting agents was mixed in the same manner as in Example 1 at a ratio of 6% to cement, and a setting test was conducted. Further, in order to examine the influence on strength, each of these quick-setting agents was mixed in the same manner as in Example 2 at a ratio of 6% to cement, and a strength test was conducted. The results are shown in Table 4.

Table 4 Initial and final strength and compressive strength of mortar As shown above, the product of the present invention showed good results in setting tests and strength tests, especially in initial strength (1 to 6 hours), which is important in agriculture due to its rapid setting effect, when only liquid A was mixed. It clearly has a remarkable rapid setting performance compared to the above.

When the quick setting agents of the present invention of Examples 1 and 2 were left at room temperature for 3 months, no precipitation of crystals such as aluminum hydroxide was observed. Furthermore, when 6% jetanolamine and 1% borax were blended into liquid A, a small amount of jetanolamine was observed to be separated into the upper layer.

(Effects of the Invention) The quick-setting agent for cement of the present invention has higher quick-setting properties than conventional liquid quick-setting agents, so it is possible to reduce the amount added to cement, which is advantageous in terms of cost. Since it has particularly high initial strength, it is particularly effectively used in the S1-M construction method. Also, if a stabilizer is added, the product can be stored for a long time without changing its performance.

Claims (1)

[Claims] A quick-setting agent for cement, characterized in that diethanolamine and alkali tetraborate are blended into an aqueous solution containing alkali aluminate and alkali carbonate as main components.