JPH0292876A - Production of concrete - Google Patents

Abstract

PURPOSE:To inexpensively obtain lightweight concrete having high freezing and thawing resistance by blending a binder with a concrete admixture nonseparable in water and water and kneading the prepared pasty mixture with lightweight coarse aggregate in an absolute dry or air dry state to produce concrete. CONSTITUTION:A binder (e.g., cement) is blended with a concrete admixture (e.g., water-soluble cellulose ether) nonseparable in water and water to prepare a pasty mixture. Then the pasty mixture is kneaded with lightweight coarse aggregate (e.g., granulated material of shale) in an absolute dry or air dry state and then concrete is produced by a conventional procedure. Consequently, water absorbing phenomena of lightweight coarse aggregate are suppressed, reduction in workability can be suppressed, further resistance to repeated freezing and thawing can be improved and the prepared concrete is preferably suitable for uses such as marine structures, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for producing concrete, and is particularly used for marine structures, bridges, high-rise RC structures, and the like. This invention relates to a method for producing concrete that is lightweight and has high freeze-thaw resistance.

[Conventional technology]

In the past, various experiments have been conducted to reduce the weight of concrete as a structural material in order to improve workability and ease of transport when constructing bridges and high ff1Rc structures.1For example, lightweight aggregate is mixed into cement. Concrete is now being put into practical use.

However, since the lightweight aggregate mixed into such lightweight aggregate concrete has higher water absorption than ordinary aggregate, if it is used in a dry state, it may cause water damage during mixing, transporting, or pouring of the concrete. It absorbs water and its quality changes or deteriorates. For this reason, in order to improve the stability of the quality of concrete, such lightweight aggregates are usually mixed in a sufficiently water-absorbed state.

[Problem to be solved by the invention]

However, in the case of such conventional lightweight aggregate concrete using water-absorbed lightweight aggregate, the resistance to repeated freezing and thawing is significantly reduced, and the water absorption rate of the lightweight aggregate is 10 to 10% compared to fine aggregate. 20%, 20~ for coarse aggregate
Because it is 30%.

When water absorption becomes sufficient during the concrete production process, there is a problem in that the weight of lightweight aggregate increases in proportion to the water absorption rate.

On the other hand, in order to improve the freeze-thaw resistance, bone dry aggregate is used.

In anticipation of slump loss during transportation and driving, a large amount of high-performance water reducing agent is used to ensure workability during driving, and the lightweight aggregate itself is artificially coated to prevent water absorption. However, there was a practical problem that it would be economically disadvantageous.

This invention was made by focusing on such conventional problems, and by using a concrete admixture that does not separate in water, etc., it gives viscosity to cement paste, suppresses water absorption phenomenon of lightweight aggregate, and improves quality. The purpose of the present invention is to provide a concrete manufacturing method for obtaining stable and lightweight concrete.

[Means to solve the problem]

The method for producing concrete according to the present invention is to prepare a paste mixture by mixing a binder with an underwater inseparable concrete admixture and water, and adding bone-dry or air-dried lightweight coarse aggregate to the paste mixture. It was made to be kneaded and mixed.

In addition, a method for producing concrete according to another aspect of the present invention is to prepare a mortar-like mixture by mixing a binder with an underwater inseparable concrete admixture, water, and water-absorbed fine aggregate, and to make a mortar-like mixture. It is made by mixing dry or air-dried lightweight coarse aggregate.

Furthermore, another invention of this invention, in addition to the above-mentioned inventions,
Ultrafine blast furnace slag powder is used as part of the binder.

[Effect]

The underwater inseparable concrete admixture in this invention is
When mixed into a concrete mixture, the main ingredient, cellulose-based or acrylic-based water-soluble polymers, adsorbs around the particles of binder such as cement, providing a cross-linked structure between each particle and weakly binding the particles together. However, it acts to increase the viscosity of concrete, and also makes it difficult for water to move toward the lightweight aggregate, thereby preventing the lightweight aggregate from absorbing water. Furthermore, by using ultrafine blast furnace slag powder as part of the binder, the freeze-thaw resistance of underwater non-separable concrete can be improved.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.

First, in this invention, a water-inseparable concrete admixture 1, which is highly effective in reducing water separation, is mixed with ordinary cement paste or mortar.

A paste-like mixture is produced, and a dry lightweight aggregate is mixed with the paste-like mixture to produce mixed concrete.

To explain this specifically, first, a paste mixture is made by mixing a binder such as cement with a water dispersant and an inseparable concrete admixture, and then this paste mixture is mixed with dry lightweight fine particles. One or both of the aggregate and lightweight coarse aggregate are mixed to obtain the desired concrete composition. Dispersants used here include AE agents such as special anionic surfactants, water reducers and AE water reducers such as polysulfone/polycarboxylate, high performance water reducers such as polyalkylaryl sulfonate, and polysulfone polycarboxylic acid. Glidants such as salts are used. In addition, acrylic and cellulose-based water-soluble polymer compounds and water-soluble cellulose ethers are used as water-inseparable concrete admixtures.

This provides a thickening function and makes it difficult for water to migrate to the aggregate side.

Further, as the lightweight fine aggregate or lightweight coarse aggregate, for example, an artificial lightweight aggregate made by crushing and granulating shale rock and baking and hardening the granulated rock is used.

Now, if we look at the case where a paste-like mixture as described above is made using a cellulose-based water-soluble polymer compound as an inseparable concrete admixture, as shown in Figure 1, the cellulose-based water-soluble polymer Assuming that Compound 1 is a long chain with an average length of about 1 micron and a thickness of about 0.001 micron, when this is mixed with water, a binder, etc., the above cellulose-based water-soluble polymer compound 1 adsorbs around the particles 2 of the binder such as cement, forms a crosslinked structure between each particle 2, weakly bonds these particles 2, and increases the viscosity of the paste mixture. It acts on

Furthermore, even when dry lightweight fine aggregate or lightweight coarse aggregate as described above is mixed into a paste mixture containing such an underwater inseparable concrete admixture, these cannot be directly removed from the paste mixture. Water absorption can be suppressed, and problems such as changes in quality during pumping or pouring of the concrete or a pump closure accident can therefore be avoided. In this way, by adding viscosity to the paste mixture and suppressing the water absorption phenomenon of lightweight aggregates,
It is possible to produce concrete that is lightweight and easy to handle.

Furthermore, in the present invention, concrete similar to the above can be made by mixing lightweight coarse aggregate with a mortar-like mixture containing a water-inseparable concrete admixture. That is, this involves mixing a binder such as cement with a water dispersant, an inseparable concrete admixture, and water-absorbed fine aggregate to create a mortar-like mixture, and then drying this mortar-like mixture! lrl amount of coarse aggregate is mixed to obtain the desired concrete composition. Here, the same dispersant and water-inseparable concrete admixture as those in the above embodiments are used, but here, a-aggregate such as water-absorbed sand is mixed into the mortar-like mixture.

In this example, a polymer compound 1 such as a cellulose-based compound adheres to the periphery of the binder particles 2, weakly binding these particles 2, and forming a mortar-like mixture even if water-absorbed fine aggregate is mixed in. It acts to increase the viscosity of the aggregate, and it acts to prevent water from being absorbed into the dry lightweight coarse aggregate that is mixed in afterwards. Therefore, it is difficult to use fine aggregate that has absorbed water. Although the weight increases slightly, it is during kneading.

Deterioration of concrete during transportation and pouring can be suppressed, and freeze-thaw resistance can be improved.

In addition, by using ultrafine blast furnace slag powder or fly ash as a part (for example, 50%) of the binder used in each of the above examples, film formation is possible due to the adsorption phenomenon of the polymer compound 1 such as cellulose to the cement particles. By this action, water utilization of the binder can be suppressed, and the freeze-thaw resistance of the cement paste as a binder can be further improved.

Table 1 shows the amounts and effects of the constituent materials of concrete manufactured by this method based on experimentally determined data.

(Margin below) Here, case Nα1 is air-dried lightweight fine aggregate.

Concrete using air-dried lightweight coarse aggregate and water-inseparable concrete admixture, case Nα2 is air-dried light ffk fine aggregate, bone-dry light coarse aggregate and water-inseparable concrete Concrete using an admixture, Case NQ 3 is air-dried lightweight fine aggregate,
Each case of concrete using bone-dry coarse aggregate but not using Kioki non-separable concrete admixture is shown. According to this, there is no difference in concrete properties between case Nα1 and case No. 2. However, compared to case Nα2, case Nα3 has a smaller slump and lower workability despite having the same composition relationship, and as a result, the concrete property improvement effect of the water-inseparable concrete admixture is less effective. It can be seen that there are some remarkable results.

In addition, the freeze-thaw resistance of concrete using a water-inseparable concrete admixture is somewhat inferior to that of concrete without it, but ultrafine powder of blast furnace slag (specific surface area 8
000co? /g or more) as part of the binder, especially by replacing it by 50% or more.

Now, ordinary cement and blast furnace cement are used as binders, and 0% ultra-fine blast furnace slag powder is added to them.

Mix at a ratio of 25%, 50%, and 1.00%, freeze,
When the relative dynamic elastic modulus (%) is experimentally determined for each of 0 to 300 melting cycles, it is as shown in FIGS. 2 and 3. This relative dynamic elastic modulus indicates the density of concrete, and is, for example, the elastic modulus of the material determined from the propagation speed of ultrasonic waves. Therefore, when ultrafine blast furnace slag powder is mixed with ordinary cement at the above ratio as shown in Figure 2, the relative dynamic elastic modulus is hardly improved at low mixing ratios of 0% and 25%, but at 50% Ya10
It can be seen that at 0%, sufficient results are obtained even after 300 cycles. On the other hand, since the blast furnace cement shown in Figure 3 is made by mixing fine blast furnace slag powder into Portland cement in advance, if the amount of ultrafine blast furnace slag powder newly mixed into this blast furnace cement is 0% or 25%. But freezing,
A sufficient relative dynamic elastic modulus was obtained even after 120 melting cycles, and even if 50% ultrafine blast furnace slag powder was mixed, the relative dynamic elastic modulus decreased after 150 freezing and thawing cycles. It ends up.

Therefore, when the amount of ultrafine blast furnace slag powder is 50% or more, better results can be obtained by using ordinary cement. Therefore, the amount of ultrafine blast furnace slag powder mixed in is:
An appropriate one is selected depending on the type of cement (binding material) to be mixed with it.

〔Effect of the invention〕

As described above, according to the present invention, a paste-like mixture is made by mixing a binder with an underwater inseparable concrete admixture and water, and this paste-like mixture is added with bone-dry or air-dried lightweight coarse aggregate and Since one or both of the lightweight fine aggregates are mixed together, the water absorption phenomenon of these lightweight aggregates can be suppressed even when using the above-mentioned lightweight aggregates in bone-dry or air-dried conditions, improving workability. It is possible to suppress the decrease in concrete, and also to reduce the weight of concrete and improve its freeze-thaw resistance.

According to another aspect of the present invention, a mortar-like mixture is prepared by mixing a binder with an underwater inseparable concrete admixture, water, and water-absorbed fine aggregate, and the mortar-like mixture is kept in an absolutely dry state or air-dried state. Since the dry lightweight coarse aggregate is kneaded and mixed, even if fine aggregate that has absorbed water in advance is mixed in to form a mortar mixture, the dry lightweight coarse aggregate that is added later will absorb water as described above. Since the water-inseparable concrete admixture suppresses the increase in concrete weight, the only increase in the weight of concrete is due to water absorption, and overall there is little change in workability, and it is possible to improve freeze-thaw resistance.

Furthermore, by using ultrafine blast furnace slag powder as a part of the binder, the freeze-thaw resistance of the cement paste 1 can be further improved by using the ultrafine blast furnace slag powder as a binder.

[Brief explanation of drawings]

Fig. 1 is a composition diagram of concrete made by the concrete production method according to the present invention, Fig. 2 is a relative dynamic elastic modulus characteristic diagram regarding the mixing ratio of ultrafine blast furnace slag powder to ordinary cement, and Fig. 3 is a diagram of the relative dynamic elastic modulus characteristic of the mixed ratio of ultrafine blast furnace slag powder to ordinary cement. It is a relative dynamic elastic modulus characteristic diagram regarding the mixing ratio of blast furnace slab ultrafine powder to cement. 1. High molecular compound, 2. Particle.

Claims (1)

[Claims] 1) A paste-like mixture is prepared by mixing a binder with an underwater inseparable concrete admixture and water, and an absolutely dry or air-dried lightweight coarse aggregate is kneaded into this paste-like mixture. Concrete manufacturing method to produce concrete. 2) Make a mortar-like mixture by mixing the binder with an underwater inseparable concrete admixture, water, and water-absorbed fine aggregate;
A concrete manufacturing method in which concrete is manufactured by mixing bone-dry or air-dried lightweight coarse aggregate into this mortar-like mixture. 3) The method for producing concrete according to claims 1 and 2, characterized in that ultrafine blast furnace slag powder is used as a part of the binder.