JPS6121949A - Admixing agent for underwater work cement composition - 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] 1. Field of Industrial Application 1. The present invention relates to an admixture for mortar or concrete, and more specifically, the present invention relates to an admixture for mortar or concrete. This invention relates to an admixture that causes less material separation and is particularly suitable for underwater casting.

[Conventional technology 1] Conventionally, when constructing underwater structures such as port construction and seawall construction, unhardened concrete is used as a tremie tube or
Concrete pumps, banuts, etc. are used to place concrete into the water.

The problem in this case is that the cement content is washed away by the action of water and the aggregate is separated from the poured concrete that has not hardened yet, which not only pollutes the surrounding water.
This means that it is difficult to obtain a homogeneous concrete hardened body. In the past, efforts were made to alleviate this problem by devising construction techniques, but the situation was never satisfactory.

Therefore, in recent years, various admixtures have been proposed, such as in JP-A-58-69760, in order to modify the concrete used. However, these admixtures have low material separation resistance in the case of soft concrete, and admixtures with high viscosity result in a large amount of entrained air, which delays curing. Improvement is desired.

[Profile of the Invention] The present invention was made against this background, and the present inventors have discovered that by introducing a specific ionic group into nonionic water-soluble cellulose, the delay in the hardening speed of cement can be suppressed. discovered that the turbidity of surrounding water during underwater pouring was also improved and completed the present invention.

That is, the present invention is an admixture for cement cement cast in water, the main component of which is a nonionic, water-soluble cellulose ether partially substituted with a sulfonic acid group.

Cellulose ethers used in the present invention [alkyl celluloses such as methyl cellulose and ethyl cellulose; hydroxyalkyl celluloses such as hydroxymethyl cellulose, hydroxyethyl cellulose and hydroxypropyl cellulose; alkyl hydroxy cells such as ethyl hydroxyethyl cellulose and methyl hydroxypropyl cellulose; It is a cellulose ether in which a nonionic water-soluble cellulose ether such as alkyl cellulose is partially substituted with a sulfonic acid group.

In the present invention, the substitution reaction of cellulose ether with a sulfonic acid group is not particularly limited, and known reactions [for example, Makromol, Chem, Vol. 93, Vol.
553-261 (1966)]. As the sulfonic acid base, alkali metal salts of sulfonic acid are preferred.

Is the degree of substitution of cellulose ether by sulfonic acid group glucose unit) correct? , :') ranges from 0.05 to 1.0. If the degree of substitution is less than 0.05, the effect of preventing cement hardening speed retardation will not be sufficient, and it is preferably 01.2 or more. When the degree of substitution becomes 1.0 or more, the effect remains unchanged.

The viscosity of the cellulose ether of the present invention (measured using a B-type viscometer at 20°C with a 2t 1% aqueous solution) is 50,000 cps in order to suppress the turbidity of surrounding water during underwater casting.
From the above, it is further preferable that the viscosity is 70+000 cps or more, but if the viscosity is too high, for example 200,000 cps, the amount of air entrained in the composition will increase and the strength of hardened concrete will decrease.

When applying the admixture of the present invention to a cement composition (paste, mortar, concrete), the amount used is usually 0.1 to 5% by weight, preferably 0.5% by weight based on the cement.
~2% by weight. If it is less than 0.1% by weight, the effect will not be as good as 7%, and if it exceeds 5% by weight, the workability will be poor due to increased viscosity and the strength of the cured product will be reduced, which is not preferable.

The admixture of the present invention may be used in either powder or liquid form, and regardless of the mixture of materials, it may be mixed with various fine aggregates, coarse aggregates, fly ash, etc. as necessary. Can be used in cement compositions containing admixtures. In addition, if necessary, antifoaming agents,
Foaming agents, water reducing agents, AE agents, cement setting hardening modifiers, etc. can be used in combination.

[Example] The present invention will be specifically explained below using Examples.

Synthesis Example Commercially available methylcellulose (Matsumoto Yushi Pharmaceutical brand name, EMP
-H) 17g in dioxane 300ml, water 35ml 1.1
Dispersed in 20.5 ml solution of 0.86 N NaOH,
Stir for 1 hour. Thereafter, 24.4 g of Propanesal Fone was dissolved in 501 dioxane and added.

After stirring this mixture at 40°C for 6 hours, the reaction is completed by standing at room temperature overnight. The reactant was added to 5001 ethanol and neutralized with acetic acid while stirring well. The precipitate is washed with ethanol, filtered and dried under reduced pressure at room temperature. The degree of substitution of Na sulfonate in the methylcellulose thus obtained was 0.65. Similarly, hydroxyethyl cellulose (product name Unicell QP-520008, manufactured by Gwicel)
was substituted with sulfonic acid sodium salt, and the degree of substitution was 0.65.
A substituted product of was obtained.

Examples 1 to 3 and Comparative Examples 1 to 2 Mortar with a water/cement ratio of 0.6/1 and a Toyoura standard sand/cement ratio of 2/1 was prepared and synthesized as described above for cement (Portland cement). 1.0% by weight of methylcellulose and the above hydroxyethylcellulose
was added to prepare mortar. The methylcellulose and hydroxyethylcellulose used are listed in Table 1.

The obtained mortar was tested for water turbidity and hardening speed using the following test methods, and the results are shown in Table 1.

Turbidity of mortar - Water turbidity is the degree of turbidity of water when mortar is freely dropped into water, and a higher value indicates less turbidity.

A transparent acrylic resin cylindrical tube with an inner diameter of 8 cm and a height of 110 cm is filled with water to a height of 100 cm, and mortar is poured into it at once to a height of 5 cm and allowed to fall freely through the water to determine the height of the poured mortar. As soon as it reaches 5 cm,
Drain 2 liters of turbid water from a cock installed at a height of 20 cm + 7) from the bottom of the cylindrical pipe.

Next, on the bottom with an inner diameter of 5 c and a height of 100 c + o (+)
A transparent glass tube with markings and a scale in the height direction is used to draw out the turbid water from the top to the bottom of the glass tube (
Pour while looking at the +) mark, and read the height direction scale when the (+) mark is no longer visible. The read value was taken as the water turbidity and judged according to the following criteria: ◎; The height until the (+) mark is no longer visible is 75 cm or more. 0; The height until the (+) mark is no longer visible. height 50cm or more) less than 5c+m Δ; height until the (+) mark is no longer visible is 25cm or more 5
Less than 0 cm

Hardening speed of mortar The hardening speed of mortar was tested in accordance with JIS R5201 using a Kerr needle tester at 20° C. and 60% indoors. Judgments were made as follows in consideration of concrete pouring: O: Curing completed within 24 hours; curing completed within 6124 to 30 hours; ×: Required 30 hours or more.

Table 1 Examples 4 to 5 and Comparative Example 3 Concrete materials include Onoda ordinary Portland cement, land sand from Ogasa, gravel from Fujitsuki (maximum size 251),
Using a water reducing agent (naphthalene sulfonic acid 7-lemarin condensate, trade name Mighty 150 manufactured by Chemical Soap Co., Ltd.) and the admixture used in Examples 1 and 2, the water-cement ratio was 60%,
Concrete with a fine aggregate ratio of 42% was produced. Further, for comparison, concrete was produced in the same manner as above except that the admixture used in Comparative Example 1 was added.

For each concrete, air volume, slump,
The turbidity of water and the compressive strength of the compacts in air and in water at 28 days of age were measured. The results are shown in Table 2. In addition,
The method for forming the specimens for water turbidity and compressive strength is as follows.

Once you've done that, the *fll beak L is 1 and the east - inner diameter is 10.
cn+, fill a transparent acrylic resin cylindrical pipe with a height of 80 cm with water to a depth of 60 cm, and use a Dosko knob to drop concrete into it. Add until it reaches 120ell. Immediately after filling the water, place a water turbidity measurement rod, 120 cm long, 2 cm square rod with a scale along the length, and a 6 cm diameter circular pellet with a (+) mark engraved on the tip of the rod, into the water. , the circular plate at the tip of the rod (+
) Read the scale when the mark disappears. This read value is taken as the water turbidity.

Su 22 ni Jouji upper p-几11 厘2 degrees-" test groove J(no-section 1
Tenbutsuho - Air forming strength; JIS A 1132r
``How to make concrete strength test specimens.''

Underwater molding strength: φ1010X20 steel mold frame at depth of 50
Submerge it in a cI11 water tank and let the concrete fall freely from the water surface using a hand shovel. At this time, in order to prevent the concrete from spilling out of the mold frame,
Using a wire mesh as a mold, pour in 2 to 3 times with a hand scoop, leaving about 20 I11 mounds from the mold frame. At this time, the work of compacting the concrete,
For example, do not poke with a stick or vibrate the mold.

After pouring in this manner, immediately take it out of the water, smooth the upper surface of the mold, and let it stand.

After this, capping, curing, etc. are performed in the same manner as in-air molding.

Table 2 [Effect of the invention 1 By using the composition of the present invention, delay in cement hardening speed when high viscosity cellulose ester is used is prevented, and turbidity of surrounding water during underwater casting is suppressed. It becomes possible to do so.

In addition, the cement composition to which the admixture of the present invention has been added has a small amount of entrained air, has excellent fluidity and filling properties, and has extremely high material separation resistance not only in air but also in water, so it can be used underwater. Drop casting or spraying is suitable for cement compositions for construction, and also improves the delay in curing speed and provides a cured product with excellent strength.

Claims (1)

[Claims] An admixture for underwater pouring cement compositions whose main component is cellulose ether, which is a nonionic, water-soluble cellulose ether partially substituted with a sulfonic acid group.