JPH08169741A - Admixture for controlled-release cement - Google Patents

Abstract

PURPOSE: To retard the aggregation of concrete grains and to obtain a controlled-release cement admixture capable of controlling the dispersibility and fluidity deteriorating with time for a long time and excellent in slump holding property and workability by incorporating a specified compd. CONSTITUTION: Polysuccinimide having 1000-300,000, preferably 2000-200,000, weight average mol.wt. is incorporated. The amt. of polysuccinimide to be added to cement is not specially limited but controlled to 0.01-2.0wt.% or preferably to 0.05-1.0%. The polysuccinimide is gradually hydrolyzed by the alkali component in concrete to form a polyasparaginate, which is gradually released to prevent the aggregation of cement grains.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a novel admixture for hydraulic cement. More specifically, it relates to an admixture for sustained release cement, which has excellent properties as a dispersant, a water reducing agent, a fluidizing agent, etc. and delays the setting of concrete.

[0002]

2. Description of the Related Art In recent years, as construction work has become more technically advanced and needs for concrete performance have diversified, new concrete admixtures have been developed, which has expanded the field of new applications of concrete.
It is leading to advances in utilization technology.

Concrete admixtures are classified and defined by JIS A 0203 (concrete terminology) and JIS A 6204 (chemical admixtures for concrete) depending on their action and purpose, and they are AE agents, water reducing agents or superplasticizers. And AE
The agents and water-reducing agents are classified into standard type, delayed type and accelerated type depending on the difference in setting time.

Conventionally, as typical examples of such an admixture, a naphthalene sulfonic acid formaldehyde condensate and a melamine sulfonic acid formalin condensate admixture have been known.
Further, as an admixture excellent in fluidizing effect and slump retention, it is described in JP-B-56-12268.
An olefin-α, β-unsaturated dicarboxylic acid copolymer type (hereinafter simply referred to as polycarboxylic acid type) admixture is also known. Further, lignin sulfonate which is a natural polymer is also used.

Fluidized concrete, which has become popular as a general construction method, has the advantage of improving the physical properties of concrete, but has a problem of large slump loss. At present, as a method of reducing this slump loss, a splitting addition of a fluidizing agent and a granulation method are adopted. It is an attempt to recover.
However, the divided addition of the superplasticizer causes new problems such as the trouble of the step of introducing the superplasticizer on site, the exhaust gas and noise of the ready-mixed concrete vehicle, and the like.

[0006]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to obtain a sustained-release concrete admixture capable of reducing slump loss for a long time without adding a fluidizing agent in portions.

[0007]

Means for Solving the Problems As a result of intensive studies for solving the above-mentioned problems, the present inventors have found that when polysuccinimide is used as a concrete admixture, the fluidity of concrete can be controlled for a long time, and as a result, The inventors have found that not only a cement composition having excellent workability can be obtained, but also fluidized concrete can be manufactured in a batching plant and the construction time can be extended, and the present invention has been completed.

[0008] That is, the present invention relates to an admixture for sustained release cement, which contains a polysuccinimide.

The method for producing the polysuccinimide used in the present invention is not particularly limited, but it can be generally produced by dehydration condensation of aspartic acid with phosphoric acid.

The polysuccinimide used in the present invention has a weight average molecular weight (hereinafter abbreviated as Mw) of 100.
0 to 300,000 is preferable. If the molecular weight is less than this, sufficient water reducing effect is not exhibited. On the other hand, if the molecular weight is higher than this, the viscosity is increased, which is the opposite effect. Particularly preferably, Mw =
It is 2,000 to 200,000.

The amount of polysuccinimide added is not particularly limited, but is usually 0.01 to 2.0 wt% with respect to the cement.
%, And preferably 0.05 to 1.0 wt%.

The polysuccinimide of the present invention may be used alone and may be used together with other commonly used admixtures such as melamine sulfonic acid formalin condensate, naphthalene sulfonic acid salt condensate and polycarboxylic acid compound. You may use together.

The addition time to the cement mixture can be appropriately selected depending on the purpose of use. For example, a method of premixing with cement, a method of adding at the same time when kneading a cement mixture such as concrete, a method of adding water or another admixture after starting stirring, and after appropriately kneading the mixture, appropriately. Examples include a method of adding after an interval.

The polysuccinimide used in the present invention is gradually hydrolyzed into the polyaspartate by the alkaline component in the concrete. The sustained release of this polyaspartic acid salt in the concrete prevents the agglomeration of cement particles and allows the slump to be retained for a long time. Examples of alkaline components in concrete include calcium oxide, potassium oxide, and sodium oxide.

The type of cement to which the admixture of the present invention can be applied is not particularly limited, and examples thereof include ordinary Portland cement, early strength Portland cement, alumina cement, fly ash cement, blast furnace cement, silica cement and various mixed cements.

[0016]

The present invention will be described in detail below with reference to examples, but the present invention is not limited to the examples.

Example 1 100 g Portland cement, 26 g water, and Mw
After kneading 0.2 g of polysuccinimide (= 80,000) in a polycup, the sample was placed on a flow table and tapped 15 times to measure the flow value according to the flow test method of JIS R-5201.

Example 2 100 g Portland cement, 26 g water, and Mw
After kneading 1 g of polysuccinimide (= 80,000) with a polycup, the sample was placed on a flow table and tapped 15 times according to the flow test method of JIS R-5201 to measure the flow value.

Example 3 100 g Portland cement, 26 g water, and Mw
= 0.58 g of polysuccinimide of 78,000, naphthalene sulfonic acid, and 0.5 g of formalin high-condensate salt cement admixture (Mighty FD: manufactured by Kao Co., Ltd.) were kneaded with a poly cup, and then JIS R-5201 According to the flow test method of No. 1, tapping was performed 15 times on the flow table, and the flow value was measured.

Comparative Example 1 100 g of Portland cement and 26 g of water were hand-kneaded in a polycup, and then, according to the flow test method of JIS R-5201, placed on a flow table and tapped 15 times to measure the flow value.

Comparative Example 2 1 g of naphthalene sulfonic acid, a formalin high-condensate cement admixture (Mighty FD: manufactured by Kao Co., Ltd.), Portland cement 100 g, and water 26 g were hand kneaded in a polycup, and then flow test of JIS R-5201. According to the method, the sample was placed on a flow table and tapped 15 times to measure the flow value.

Comparative Example 3 Lignin sulfonate cement admixture (Ligace A:
Fukui Chemical Industry Co., Ltd.) 1g, Portland cement 1
After kneading 00g and 26g of water with a poly cup, JIS
According to the flow test method of R-5201, the sample was placed on a flow table and tapped 15 times to measure the flow value.

The results of Examples 1 to 3 and Comparative Examples 1 to 3 are shown in Table 1 (Table 1).

[0024]

[Table 1] From the above examples, it is understood that by mixing the polysuccinimide with the cement, sufficient fluidity is obtained even after 90 minutes.

[0025]

When a cement admixture containing polysuccinimide as an active ingredient is used, aggregation of concrete particles is delayed and dispersibility and fluidity which are lost with time can be controlled for a long time, and slump retention can be achieved. A cement admixture having excellent properties and workability can be obtained.

Claims (2)

[Claims] 1. An admixture for sustained-release cement, which comprises polysuccinimide. 2. The admixture for cement according to claim 1, wherein the polysuccinimide has a weight average molecular weight of 1,000 to 300,000.