JPS5935853B2 - cement additives - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a cement additive useful for improving the loss of fluidity of hydraulic materials such as cement paste, mortar, and concrete over time. The present invention relates to a cement additive containing polyvinyl alcohol produced by copolymerizing a polyvinyl alcohol or an alkaline hydrolyzate thereof, and a cement dispersant.

Traditionally, cement dispersants have been used to improve the fluidity of hydraulic materials.

Examples of such cement dispersants include those based on lignin sulfonate, those based on formalin condensate of β-naphthalene sulfonate, and those based on formalin high condensate of melamine having sulfonic acid residues. However, these have the following drawbacks:

In other words, those mainly composed of lignin sulfonate are
Because the short-term strength is poor, this is improved by using calcium chloride, sulfuric acid nose, amines, etc., but the disadvantage is that workability decreases after a short period of time during summer construction.

In addition, products mainly composed of formalin condensates of β-naphthalene sulfonate and formalin high condensates of melamine having sulfonic acid residues can provide good workability with a small amount of water per unit; You have to use it a lot, and your workability will drop significantly in a short period of time, so you need to be careful when using it.

For example, when these additives are used, the workability of the concrete after mixing rapidly decreases, so that handling operations must be completed within a very short period of time.

When this additive is used in the production of normal ready-mixed concrete, it cannot be transported by concrete mixer trucks or the like.

Furthermore, even when manufacturing concrete products in a factory, it is necessary to pay sufficient attention to the reduction in workability of concrete after mixing.

As a result of various studies aimed at solving these drawbacks, the present inventor found that it is sufficient to use these cement dispersants together with polyvinyl alcohol obtained by copolymerizing dimethyl malate or its alkaline hydrolyzate. , has completed the present invention.

The present invention will be explained in detail below.

Examples of preferred cement dispersants applicable to the present invention are as follows.

■Salts of naphthalene sulfonic acid formalin condensates This is not limited to single condensates of naphthalene sulfonic acid, but also polycyclic aromatic compounds such as naphthalene, alkylnaphthalene, and anthracene, or their sulfonic acid compounds, benzene, toluene, etc. It may also be a formalin co-condensate with one or more compounds selected from , phenol, benzene derivatives such as benzoic acid, or their sulfonic acid compounds.

Salts of these formalin condensates include alkali salts and/or alkaline earth salts, specifically sodium salts, potassium salts, calcium salts, and mixed salts thereof.

Commercial products of the salt of naphthalene sulfonic acid formalin condensate include the product name "Mighty" (manufactured by Kao Soap), the product name "Pole Fine" (manufactured by Monomoto Yushi), and the product name "Cellflow R1551 (Daiichi Kogyo Pharmaceutical Co., Ltd.)". ■) etc.

2. As a base commercial product of a formalin high condensate of melamine with sulfonic acid residues, the product name is "Melment" (manufactured by Showa Denko).
, the product name rNL-4000J (manufactured by Nisso Master Builders ■), and the product name "rNP-20" (manufactured by Nisso Master Builders ■).

3. Commercially available lignin sulfonate products include the product name [Hozolith iFy, 5L].
J (manufactured by Nisso Master Builders ■), and the product name ``Sunflow SJ (manufactured by Sanyo Kokusaku Pulp ■).

The amount of the above-mentioned cement dispersant used can be freely selected depending on the required water-reducing properties and fluidity.

On the other hand, the polyvinyl alcohol copolymerized with dimethyl malate according to the present invention or its alkaline hydrolyzate is a necessary component for maintaining the fluidity of cement paste, mortar, concrete, etc. in which the cement dispersant is used. It is.

The proportion of dimethyl maleate contained in the copolymerized and modified polyvinyl alcohol is preferably about 0.1 to 50 mol%.

Furthermore, the dimethyl malate portion may be hydrolyzed with an alkaline substance such as sodium, potassium, or lithium.

To produce polyvinyl alcohol by copolymerizing dimethyl maleate, for example, when vinyl acetate is polymerized in a methanol solution, dimethyl maleate is continuously added to copolymerize, and then vinyl acetate is copolymerized. Just saponify the parts.

Further, in order to further hydrolyze the dimethyl malate portion, an alkali such as caustic soda may be added in a methanol solution or an aqueous solution, and the reaction may preferably be carried out at a high temperature.

In these, the degree of saponification rate and hydrolysis rate does not significantly affect the effect of the present invention, and any degree can be used.

The amount of polyvinyl alcohol copolymerized with dimethyl malate or its alkaline hydrolyzate used is 0.01 to 0.5% by weight, preferably 0.02 to 0.2% by weight based on cement. This will have a greater effect on maintaining liquidity.

The cement to which the product of the present invention is added is normal, early strength,
Super early strength, medium heat, white Portland cement, mixed cement containing silica, fly ash, granulated blast furnace slag, etc., expanded cement, rapid hardening cement in the presence of calcium aluminate and gypsum, alumina cement, and even Examples include cement made of granulated blast furnace slag and an alkali stimulant such as hydroxides, oxides, carbonates, and sulfates of alkali metals or alkaline earth metals.

The hydraulic material to which the cement additive of the present invention has been added can be used for cast-in-place concrete for civil engineering construction, etc., as well as for curing at room temperature, steam curing, or autoclave after compaction, vibration compaction, or centrifugal force compaction. For example, piles, poles, concrete pipes, box culverts, U-shaped grooves,
Used as concrete for manufacturing factory products such as steel pipe concrete composites and blocks.

The present invention will be explained below with reference to Examples.

Example The additives shown in Table 1 were dissolved in a predetermined amount of water, and added with 2.0 kg of ordinary Portland cement and 6.0 kg of river sand produced in Sagami.
0 kg was added and mixed for 1 minute at 30°C using a band mixer to knead the mortar.

The mini-slump flow of this mortar was measured immediately after mixing, and the mortar was re-kneaded by varying the amount of water until the flow value reached 260m7M.The water-cement ratio W/C was calculated from the required water amount at this time and is shown in Table 1. It was shown to.

Immediately after kneading, the mortar with a flow value of 260 degrees was allowed to stand still, and the flow measurement diameter was set at 15% by a band mixer every 15 minutes.
The mixture was kneaded for seconds and the mini-slump flow was measured.

Mini-slump flow is determined by filling a slump cone with a height of 15 crrL (upper opening diameter: 5 CTrL, lower opening diameter: 10 Cr/L) with mortar, then immediately pulling up the slump cone and measuring the spread of the mortar at this time. Ta.

The results are shown in Table 1. Note: The additive symbols shown in Table 1 represent the following ingredients.

N: Soda salt of β-naphthalenesulfonic acid formalin condensate M: Soda salt of melamine sulfonic acid formalin condensate L: Sodium salt of ligninsulfonic acid A Polyvinyl alcohol B copolymerized with 5% dimethyl maleate in molar ratio Polyvinyl alcohol copolymerized with 50% molar ratio of rainbow methyl maleate and hydrolyzed with NaOH C Polyvinyl alcohol copolymerized with 50% molar ratio of rainbow methyl maleate D Polyvinyl alcohol copolymerized with 50 molar ratio of nidimethyl maleate % copolymerized polyvinyl alcohol hydrolyzed with NaOH

Claims (1)

[Claims] 1. A cement additive containing polyvinyl alcohol copolymerized with dimethyl malate or its alkaline hydrolyzate and a cement dispersant.