JPS5826061A - Operationability decrease prevention for cement admixture - 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 The present invention relates to a method for preventing the workability of a cement mixed material containing a high performance water reducing agent from deteriorating over time.

It is well known that reducing the water mixing ratio of cement increases the strength of the hardened cement product, but lowering the water mixing ratio reduces the fluidity of the cement mixture, so in order to improve this, Addition of water reducing agents is practiced. That is, a water reducing agent is an additive that can reduce the amount of kneading water required to provide the same fluidity, and recently, many additives with improved performance have been proposed. However, all of these water reducing agents cause a decline in fluidity over time in the cement mixture to which they are added, so they still have practical difficulties. As a method for preventing a decrease in the fluidity of a cement mixture containing a water reducing agent, a method described in Japanese Patent Publication No. 54-22460 is known. In this method, a cement mixture is prepared by adding cement additives other than a water reducing agent to cement, and then the water reducing agent is added and kneaded again. After all, a phenomenon of gradual decline occurs, so there is no reason to be satisfied.

Recently, a method of pumping cement mixed materials has been adopted, or the mixed materials are carried out at the factory and then transported to the site where they are placed. wanted i
Ru.

The present inventors investigated the phenomenon of reduced fluidity exhibited by cement mixtures with water reducing agents added, and researched ways to solve the problem. The present invention has been completed by discovering that when gluconic acid, which is a setting retardant, is added and kneaded in addition to through-drilling, the drop in slang of the concrete mixture is significantly lower, and the strength of the hardened concrete is also high.

An object of the present invention is to obtain a cement mixture having high fluidity at a small water mixing ratio by adding a water reducing agent.
Another object of the present invention is to provide a method for preventing the workability of such highly fluid cement mixtures from deteriorating over time.
The method for preventing deterioration in workability of a cement mixture according to the present invention is characterized by adding necessary additives and a high performance water reducer to cement and kneading the mixture, and then adding a setting retarder and further kneading.

Necessary additives for cement in the present invention include water, sand, gravel, and other additives for obtaining ordinary cement paste, mortar, concrete, etc., and if necessary, setting accelerators, reinforcing agents, bulking agents, etc. Examples of high-performance water reducing agents used in the present invention include formalin condensates of sodium naphthalenesulfonate, formalin condensates of sodium methylnaphthalenesulfonate, formalin of sodium alkylarylsulfonates, etc. Examples include condensates, sulfonic acid group-containing melamine formalin condensates, and the like. Commercially available industrial products are sufficient for these. Examples of the setting retarder used in the present invention include saccharose, sugars such as glucose, starch, cellulose, glycerin, polyhydric alcohols such as polyethylene, pyrogallol, gluconic acid, 2-ketogluconic acid, and citric acid. , oxycarboxylic acids or their salts such as tartaric acid, malic acid, and lactic acid; polymeric organic acids and their salts such as polyacrylic acid and carboxymethylcellulose;
Examples include lignosulfonic acid, lignosulfonic acid, and salts thereof. These setting retarders are also commercially available industrial products. Examples of the cement used in the present invention include commonly used cements such as ordinary Portland cement, early strength Portland cement, blast furnace cement, and fly ash.

By adding and kneading the above-mentioned required additives and high-performance water-reducing agent to the above-mentioned cement, cement mixtures such as cement paste, mortar, and concrete 1J-) are usually obtained, but these contain high-performance water-reducing agents. Immediately after the cross-contact, it has sufficiently high fluidity and sufficient workability, and also exhibits high strength after curing, but immediately after the cross-contact, the fluidity gradually begins to decrease. After 60 to 90 minutes, the fluidity necessary for on-site implantation is often already insufficient. 6 immediately after kneading
It is extremely desirable to maintain the high fluidity exhibited immediately after cross-crossing for a period of about 0 to 90 minutes in order to enable the pump transportation method, transportation from the cross-crossing factory to the driving site, etc. The method for preventing deterioration in workability of a cement mixture according to the present invention is a method in which the cement mixture is once prepared, and after a certain period of time has elapsed, the setting retarder is further added thereto and the mixture is kneaded again. Flow value, slump value, etc. hardly decrease for a long time, usually more than 60 minutes,
Maintains high liquidity.

By adding and kneading the setting retarder at the same time as the necessary additives for the cement, high performance water reducing agent, etc., it is not possible to maintain high fluidity in the cement mixture. Moreover, a cement mixed material with little decrease in fluidity cannot be obtained by the method of kneading the above-mentioned required cementol additive and the above-mentioned setting retarder, and then adding and kneading the above-mentioned high-performance water reducing agent.

K that prevents deterioration in workability of cement mixed materials by the present invention
After adding the necessary additives and high-performance water reducer to the cement and kneading, it is recommended to add the setting retarder usually after 30 seconds or more, preferably 5 minutes or more. A highly fluid cement mixture cannot be obtained.

Preferably, the setting retarder is added within 90 minutes, particularly within 50 minutes, and the mixture is kneaded again.

In a preferred embodiment of the present invention, the amount of the high performance water reducing agent added is approximately α05 to 2.0 by weight relative to cement. α
If it is less than 0.05% by weight, the water reduction effect will be poor, and if it is added in excess of 2.0% by weight, it will have an adverse effect on the hardening of the cement mixture.

Further, the amount of the setting retarder added is usually about 5% by weight based on the cement α01 to Q.

If cL0 is less than 1% by weight, the effect of preventing deterioration in workability of the cement mixture is poor, and if cL is added in excess of 5% by weight, the initial strength of the cement mixture may be lowered, which is not preferable. Particularly preferred setting retarders are oxycarboxylic acids or salts thereof.

Although the physical elucidation of the effect of the present invention to prevent deterioration in workability of cement mixed materials has not yet been completed, it is thought to be as follows. That is, by adding and kneading a high performance water reducing agent without adding a setting retarder, the cement particles are first sufficiently dispersed. Although the cement particles are surrounded by the water reducing agent, the shape of the cement particles is rounded and agglomeration active portions remain, and as a result, as the re-agglomeration of the cement particles progresses, the fluidity gradually decreases. By adding a setting retarder and kneading again at an appropriate time before the re-agglomeration progresses, it is possible to block only the flocculating active portions with the retarder, thereby preventing the progress of re-agglomeration and thereby reducing the gradual decrease in fluidity. It is thought that this can be prevented.

According to the method of the present invention, by adding a setting retarder, it is possible to cause a slight delay in the setting start time, and it is possible to prevent a decrease in the workability of cement mixtures, especially in the summer. Even if a setting retarder is added, after the cement mixture has hardened, the strength of the cured product is higher than that without the addition of a setting retarder, and an reinforcing effect is also observed.

The present invention can be easily implemented and its usefulness is extremely high.

Examples and comparative examples will be described below, but the technical scope of the present invention is not limited thereto.

Examples 1 to 5 After mixing cement, aggregate, water, and high-performance water reducing agent as shown below, mix the mixture in a forced mixing mixer for 60 seconds. Immediately after the mixing ends, the time listed in Table 1 has passed, and at 9 points (at the time of addition) K setting delay. The agent was added to the cement in the amount (%) listed in Table 1 and kneaded again for 60 seconds, and samples were taken from the kneaded material after the second kneading every 50 minutes from the end of the first kneading.
When the slump was measured according to 01, the results shown in Table 1 were obtained. In addition, a separate sample was taken at time 9, 90 minutes after the end of the first crosstalk, and the compressive strength of the cured product was measured after 3 days and 28 days of curing at a room temperature of 20 to 23°C.The results shown in Table 1 were obtained. Obtained.

Blended cement (Ordinary Portland cement made by Chichibu) 10
0 parts by weight coarse aggregate from Kinugawa, maximum dimension 20mm 5
65 weight part fine aggregate from Kinugawa, river sand 22
4 parts by weight water
55 parts by weight High performance water reducing agent Notes below Table 1
cL5tt part Comparative Examples 1 to 5 When neither a high performance water reducing agent nor a setting retarder is used (Comparative Example 1)
and when only setting retarder is not used (Comparative Examples 2 and 5) [
Then, slump measurement and compressive strength measurement were carried out in the same manner as in Example 1, and the results shown in Table 1 were obtained.

Example 4 Slump measurement and compressive strength measurement were carried out in the same manner as in Example 1 except that a formalin condensate of sodium naphthalene sulfonate was used instead of the sulfonated melamine-formalin metal condensate water reducing agent in Example 1, and the results are shown in Table 1. The results described were obtained.

Example 5 Slump measurement and compressive strength measurement were carried out in the same manner as in Example 1 except that sodium citrate was used instead of sodium gluconate in Example 1Vc, and the results shown in Table 1 were obtained.

Comparative Example 4 Slump measurement and compressive strength measurement were carried out in the same manner as in Example 1 except that a set retarder was added and kneaded together with other additives during the first mixing. Got the results.

Comparative Example 5 Example 1 except that during the first cross-talk, a setting retarder was added to the VC without adding a high-performance water reducer, and during the second cross-talk, a high-performance water reducer was added without adding a setting retarder. When the slump and compressive strength were measured in the same manner as above, the results shown in Table 1 were obtained.

Example 6-8 Slump measurement and compressive strength measurement were conducted in the same manner as Examples 1 to 4 except that the type of setting retarder was changed.
The results listed in the table were obtained.

All of the examples of the present invention show that the drop in slump after crosstalk is significantly smaller than that of the comparative examples, and the compressive strength of the cured products is also sufficient.

Claims (1)

[Scope of Claims] (1) A method for preventing deterioration in workability of a cement mixture, which comprises adding necessary additives and a high-performance water reducing agent to cement, kneading the mixture, and then adding a setting retarder and further kneading the mixture. (2) The amount of high-performance water reducing agent added to cement α05
2.0% by weight of a cement mixed material according to claim (1). (8) The amount of setting retarder added to cement α01~[L
Claims (1) or (2) that are outstanding
Method for preventing deterioration in workability of cement-contaminated materials as described in . (4) Claims (1) and (2) in which the high performance water reducing agent is a formalin condensate of sodium naphthalene sulfonate or a sulfonic acid group-containing melamine formalin condensate.
A method for preventing a decrease in workability of a cement mixed material as described in item (8) or item (8). (5) Claims (1), (2), and (8) in which the setting retarder is oxycarboxylic acid or its salt, ligninsulfonic acid or its salt, or polyacrylic acid or its salt. ) or (4), the method for preventing deterioration in workability of cement mixed materials.