JPH0215496B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to concrete, which is a cement composition,
It relates to additives for mortar or cement paste. [Prior Art] Generally, fresh cement paste, mortar, and concrete that are freshly mixed gradually lose their fluidity over time. This phenomenon is caused not only by chemical factors based on the very early hydration reaction between cement and water, but also by the physical agglomeration of cement particles in cement paste, mortar, and concrete over time, creating a secondary agglomerated structure. This is thought to be caused by the following. This decrease in fluidity varies depending on the type of cement, aggregate, admixture, blending conditions, kneading conditions, method of adding admixtures, etc.; ) Fluctuations in the quality of concrete, etc. due to fluctuations in waiting time at the pouring site for ready-mixed concrete, etc. (C) This causes many problems such as restrictions on pumping distance during pump construction and problems with pipe blockages. The following means have been proposed as conventional techniques for solving these problems, but at present no satisfactory solution has yet been found. One of these methods is to add a high-performance dispersant containing naphthalene sulfonic acid formalin condensate (hereinafter referred to as NSF) as a main ingredient to cement compositions such as concrete with reduced fluidity as a fluidizing agent to improve fluidity. This is a method of restoring it at the pouring site. [Problems to be solved by the invention] However, the fluidity of cement compositions containing such high-performance dispersants is significantly reduced, and the pot life after restoration is limited to 20 to 30 minutes. In addition, there are many other problems, such as the difficulty in securing a place to add the superplasticizer in urban areas, the amount of work required to add the superplasticizer, and the time required to confirm the type after adding the superplasticizer, resulting in a decrease in work efficiency. In addition, high-performance dispersants and high-performance AE water reducing agents with little change in fluidity over time, such as a dispersant made of a mixture of NSF and lignin sulfonate (Japanese Patent Laid-Open No. 60-5052
Although a dispersant consisting of a mixture of NSF and a polycarboxylate (Japanese Patent Application Laid-open No. 183157/1983) has been proposed, the change in fluidity over time is not satisfactory. [Means for Solving the Problems] Therefore, it is currently desired to develop a high-performance dispersant whose fluidity changes little over time. Under such circumstances, the present inventors have determined that the weight average molecular weight is 1000.
A mixture of polystyrene sulfonate with a weight average molecular weight of ~100,000 and a water-soluble salt of a copolymer of lower olefin and maleic anhydride with a weight average molecular weight of 2,000 to 20,000 is a high-quality cement additive with less change in fluidity over time than conventional cement additives. The present invention was achieved by discovering that it is a high-performance dispersant. The present invention uses polystyrene sulfonate (a) having a weight average molecular weight of 1000 to 100000 and a weight average molecular weight of 1000 to 100000.
The ratio of the water-soluble salt (b) of the copolymer of 2000 to 20000 lower olefin and maleic anhydride is 97:3 to 20:
The present invention provides a cement additive characterized by containing a mixture of 80% and 80% as an active ingredient. The polystyrene sulfonate in the present invention has a weight average molecular weight of 1000 to 1000 in terms of water reduction effect.
A value of 100,000 is desirable, and dispersibility is poor even if it is smaller or larger than this. Particularly desirable is 5000 ~
50000. Further, examples of the lower olefin constituting the copolymer of lower olefin and maleic anhydride include olefins having 2 to 4 carbon atoms such as ethylene, propylene, and isobutylene. Among these, isobutylene is particularly desirable. The composition ratio of lower olefin and maleic anhydride in the copolymer of lower olefin and maleic anhydride is such that the salt of the copolymer is required to be water-soluble, and the ratio of lower olefin to 1 mole of maleic anhydride is A ratio of 1 to 3 moles is desirable. If the weight average molecular weight of the copolymer is too small, the water-reducing effect will be small and the amount of air will be large when used as a cement additive. Furthermore, if the weight average molecular weight is too large, the water reduction effect will be reduced. Therefore, the weight average molecular weight of the copolymer is preferably 2,000 to 20,000, and it is preferable that the copolymer is not only copolymerized to have a weight average molecular weight of 2,000 to 20,000, but also purified using an ultrafiltration method or the like. desirable. If the water-soluble salt of the copolymer of lower olefin and maleic anhydride is too large, curing will be delayed, and if it is too small, the water-reducing effect will be reduced. The mixing ratio of the combined water-soluble salt is 97:3
〜20:80 is preferable, especially 95:5〜
It's 30:70. The high-performance dispersant as a cement additive of the present invention can be used as an AE water-reducing agent, a high-performance AE water-reducing agent, and a fluidizing agent, and is also effective in combination with other dispersants. [Example] The present invention will be explained below using concrete test results. Example 1 Sodium polystyrene sulfonate (manufactured by Toyo Soda KK, trade name Ultraite PS-1, weight average molecular weight 10000) and isobutylene and maleic anhydride copolymer (manufactured by Kuraray KK, trade name Isoban,
Concrete was produced by adding 0.5% (solid content equivalent) of an additive obtained by mixing 50:50 of 10,000 (weight average molecular weight: 10,000) with respect to cement, according to the formulation shown in Table 1. Example 2 Isobutylene and maleic anhydride copolymer (manufactured by Kuraray KK, trade name Isoban, weight average molecular weight
10000) with an ultrafiltration membrane (manufactured by Toyo Roshi KK, product name)
UK-50, molecular weight cut off 50,000), and the permeate is filtered through an ultrafiltration membrane (Bio Engineering K.
Concentration and purification were carried out using a product manufactured by K. K., trade name GO5T, molecular weight cutoff 5000). This and sodium polystyrene sulfonate (manufactured by Toyo Soda KK, trade name Ultraite PS-1,
Concrete was produced by adding 0.5% (solid content equivalent) of an additive obtained by mixing 50:50 of 10,000 (weight average molecular weight: 10,000) with respect to cement, according to the formulation shown in Table 1. Example 3 As in Example 1, an additive obtained by mixing sodium polystyrene sulfonate, isobutylene, and maleic anhydride copolymer at a ratio of 80:20 was added to cement.
Concrete was produced with the addition of 0.5% (in terms of solid content) according to the formulation shown in Table 1. Example 4 As in Example 1, an additive obtained by mixing sodium polystyrene sulfonate, isobutylene, and maleic anhydride copolymer at a ratio of 40:60 was added to cement.
Concrete was produced with the addition of 0.5% (in terms of solid content) according to the formulation shown in Table 1. Comparative Example 1 Naphthalene sulfonic acid formalin condensate (Kao
Mix 60:40 of a lignin sulfonate ultrafiltration product concentrated and purified using an ultrafiltration membrane (manufactured by Bio Engineering KK, product name GO5T, molecular weight cut off 5000) (manufactured by KK, product name Mighty 150). The obtained additive was added at 0.5% (solid content equivalent) based on cement, and concrete was manufactured according to the formulation shown in Table 1. Comparative Example 2 Naphthalene sulfonic acid formalin condensate (Kao
(manufactured by KK, trade name Mighty 150) and sodium polyacrylate (weight average molecular weight 10,000) in a ratio of 76:24.
0.5% (solid content equivalent) of the additive obtained by mixing with cement was added to produce concrete according to the formulation shown in Table 1. Comparative Example 3 As in Example 1, an additive obtained by mixing sodium polystyrene sulfonate, isobutylene, and maleic anhydride copolymer in a ratio of 98:2 was added to cement.
Concrete was produced with the addition of 0.6% (in terms of solid content) according to the formulation shown in Table 1. Comparative Example 4 As in Example 1, an additive obtained by mixing sodium polystyrene sulfonate, isobutylene, and maleic anhydride copolymer at a ratio of 10:90 was added to cement.
Concrete was manufactured with the addition of 0.4% (in terms of solid content) according to the formulation shown in Table 1. The materials and mix of concrete used are as follows. Materials used: Cement (C): Ordinary Portland cement Fine aggregate (S): Land sand from Kisarazu (specific gravity 2.59,
FM2.40) Coarse aggregate (G): Crushed stone from Yamaguchi (specific gravity 2.70, FM6.75) Water (W): Tap water

[Table] Immediately after kneading for 3 minutes with a 1001 mixer, 30,
Slump was measured after 60 and 90 minutes. All measurements of concrete slump, air content, 28-day compressive strength, and setting time were conducted in accordance with JIS. The measurement results are shown in Table 2, and it can be seen that the product of the present invention (Example) has better fluidity retention than the conventional dispersant (Comparative Examples 1 and 2). Comparative Examples 3 and 4 have problems such as poor slump stability and long coagulation time when the two-component composition ratio of sodium polystyrene sulfonate, isobutylene, and maleic anhydride copolymer is outside the claimed range. It shows.

【table】

〔Effect of the invention〕

By using the product of the present invention, it is possible to obtain a cement composition whose fluidity changes less over time than with conventional cement additives.

Claims (1)

[Claims] 1 Contains the following components (a) and (b) as essential components, and the ratio of components (a) to (b) is 97:3 to 97:3.
A cement additive comprising a 20:80 mixture as an active ingredient. (a) A polystyrene sulfonate having a weight average molecular weight of 1,000 to 100,000; (b) A water-soluble salt of a copolymer of lower olefin and maleic anhydride having a weight average molecular weight of 2,000 to 20,000.