JPS5858206B2 - Manufacturing method of high strength mortar and concrete - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing high strength mortar and concrete.

BACKGROUND OF THE INVENTION Various concrete structures have long been constructed by adding coarse aggregate, fine aggregate, and water to ordinary Portland cement and kneading the mixture.

At this time, the amount of cement, water, fine aggregate, and coarse aggregate to be mixed is determined depending on the purpose of obtaining the strength and durability required of the concrete depending on the structure, and the fluidity required for concrete pouring work. The mixing ratio of these materials differs, and by changing the mixing ratio, the physical properties of the resulting concrete structure also differ.

In order to improve the fluidity of the concrete to be poured and make the pouring work easier, for example, adding a high fluidizing agent etc. is possible in order to adopt a construction method using a concrete pump, etc. A common method is to increase the amount of water in the concrete and increase the slump of the concrete.

However, according to the general method of increasing the amount of mixing water to improve fluidity, if the amount of cement per unit volume is constant, the ratio of water to cement in mixed concrete, that is, the water There is a disadvantage that the cement ratio becomes large and the strength and durability of the concrete decreases after hardening.

This is because surplus water in the mixed concrete causes a breathing phenomenon and separates and rises to the upper surface of the concrete, which reduces the bonding force between aggregates due to cement paste, and the upward flow path of breathing water causes the concrete to harden. This is because they remain as voids afterwards, preventing the formation of dense concrete.

On the other hand, in the case of so-called hard-mixed concrete, which reduces the amount of water while keeping the amount of cement constant, it is possible to cast concrete with excellent quality in terms of strength and durability, but the water and cement ratio Since the concrete has a small flow rate, it is difficult to make high-quality concrete unless the entire culm is carefully constructed in cases involving complex structural shapes, such as in reinforced concrete structures. be.

FIG. 1 shows two typical concrete manufacturing methods that have been used in the past.

The method shown in Figure a is a method of producing concrete by sequentially putting gravel G, sand S, and cement C into a mixer and kneading them, then adding water W and kneading them further.
In addition, the method shown in the figure is to make cement paste by mixing and stirring precaulking cement C and water W using a stirring device called a water cooler, and then mix this cement paste, sand S, and gravel G. This shows a method for producing concrete by mixing the following materials using a concrete mixer.

In other words, in the past, it was assumed that the physical properties of concrete were uniquely determined by the quality of cement, sand, gravel, and water mixed together, and the mixing ratio of these, and the quality of these materials was ensured. Accurate measurement and effective mixing were considered to be the basic indicators for improving the quality of concrete.

In the present invention, a part of the designed amount of water is added to cement in advance and stirred to knead the cement into a ball.
Mechanical vibration (usually 300H) using a vibrator such as an eccentric mass type
z or less) to cause a liquefaction phenomenon, and then add the remaining amount of water in the designed mix and re-stir the cement paste. This invention relates to a method for producing high-strength mortar and concrete that has good fluidity and does not cause breathing by kneading, and when the present invention is used, a small amount of cement is required to obtain a specified strength. This is accompanied by economic effects.

The present invention will be explained below based on an embodiment of the manufacturing method of the present invention shown in FIG.

First, when water W1 equivalent to 25 tons of cement weight is added to the designed amount of ordinary Portland cement C and stirred, the cement powder is kneaded into a ball shape. When mechanical vibration is forcibly applied using a vibrator such as a cam type eccentric mass type vibrator, the lump-like cement temporarily liquefies and remains in a fluid state at the bottom of the container.

When water in the designed mix and water W2 corresponding to the remaining amount of the cement ratio of 55 are added to this cement and stirred, a cement paste is formed that is not much different in appearance from the conventional method shown in Figure 1. The cement paste was mixed with a designed amount of sand (i.e., cement: sand - 1:2.5) or a designed amount of sand and gravel (cement: sand: gravel - 1:2.
5:3.0), compared to mortar or concrete of the same mix by conventional methods.
It was possible to produce mortar and concrete with a hardening strength of 35% or more.

The physical properties of mortar and concrete produced by this method vary depending on the duration of forced mechanical vibration applied to the pre-caulked cement.

FIG. 3 shows the ratio of the initial added water amount W1 and the total added water amount (, W1+W2) to the cement amount C according to the method of the present invention, such that Wl/C=0.25, (W1+W2)/C=0.
After adding initial water W1 to the cement and stirring it, and applying mechanical vibrations with various vibration times,
This figure shows the change over time in the shrinkage strength of mortar produced by stirring with post-added water W2 and kneading with sand S.

The line marked ■ in this figure shows the actual measured value of the compressive strength in water and cement ratio of 0.55, which was produced by the conventional method without applying vibration. ■ and ■ show the respective intensity curves of materials whose excitation times were 1 minute and 30 seconds, 3 minutes, and 5 minutes, respectively.

As can be clearly seen from Figure 3, a large increase in strength appears in the mortar after hardening by applying mechanical vibration, but the highest value is shown when the vibration time is 3 minutes, and after 3 minutes. It is also decreasing.

Although a graph for a 10-minute vibration time is not shown in order to avoid complicating the figure, the intensity curve for a 10-minute vibration is not much different from that for a 5-minute vibration.

That is, there is a certain limit to the increase in intensity due to vibration, and it appears that the vibration peaks at 3 minutes of vibration time and converges to a certain value after 3 minutes.

According to this example, the strength increase on the 28th day was 1 minute 30 seconds, 3 minutes, 5 minutes, and 1 minute compared to the standard mortar without vibration.
Those with 0 minutes of vibration added are 21%, 35φ, and 17, respectively.
%, showed an increase in strength of 17 factors.

Figure 4 shows the amount of initially added water W1 when the excitation time is 3 minutes, Wl/C=0.2 5 , 0.40, 0.55
After applying mechanical vibrations in various ways so that
Mortar adjusted to a cement ratio of 0.55 is mixed with water and cement ratio of 0.55 made using the conventional method without adding any vibration.
The strength curve is shown in comparison with standard mortar.

In the figure, ■, [F], and 0 are Wl/C=0.25°0.
40, which corresponds to 0.55, where 0 is the strength curve for standard mortar without vibration.

As is clear from FIG. 4, the strength of the mortar after 3 days to 28 days is greatest when the initial amount of water added is Wl/C0925, and decreases as Wl/C increases.

However, even with the same water and mortar with a cement ratio of 0.55, the mortar with the initial addition of water at Wl/C = 0.55 and mechanical vibration applied exhibits a much larger value than the standard material without vibration. I can see that

Next, cement: sand: gravel - 1:2.5:3.0゜W/
Comparing the strength of standard mixed concrete with C=0.55 and slump of 7.5 cIrL and the same mixed concrete according to the present invention with Wl/C=0.25 and vibration time of 3 minutes,
The average 28-day strength of the five specimens was 298 kg/day for the former.
cfIt, the latter being 405 kg/ffl, showing a 36% strength increase according to the method of the invention.

Furthermore, the slump increased from 7.5 (11771) for the former to 9.7 CrrL for the latter, indicating that the fluidity of the concrete was significantly improved.

In FIG. 5, the ratio Wl/C between the initial amount of added water W1 and the amount of cement was varied, and tests were conducted based on the above-lined test method of JIS A 1108.

Material◆This shows the compressive strength of concrete after 28 days.

As can be seen from this figure, concrete mixed using vibrated cement paste has an overall increased compressive strength, regardless of the value of Wl/C, compared to concrete made using the normal method. There is.

Furthermore, it can be seen that the maximum value of Wl/C is obtained within the range from around 0.2 to 0.3.

In addition, when the value of Wl/C becomes 0.2 or less, the amount of initially added water is too small, making mechanical kneading difficult.

Therefore, it is desirable to set the value of Wl/C to 20-30.

FIG. 6 similarly shows the relationship between compressive strength and Wl/C on the 28th day in the case of mortar.

In the case of mortar, overall strength is higher than that of concrete, but the maximum value appears in the range of Wl/C from around 0.2 to 0.35.

However, the overall shape of the strength increase graph shows that it is very similar to that of concrete.

Regarding the breathing phenomenon that directly affects the strength increase and high fluidity of mortar and concrete, W/C
= 0.55 standard cement paste and the inventive W 1
/C=0.25, (W1+W2)/C0,5
Comparing the pastes subjected to vibration in No. 5, the breathing rate, which indicates the percentage of floating water to the amount of water in the material, was 11.4% for the former and 2.3% for the latter, indicating a significant decrease in breathing.

FIG. 7 shows the breathing rate of concrete using a vibrated cement paste, measured according to the test method of JIS A 1123.

The breathing rate, which affects the fluidity of concrete, is W
A significant improvement is seen when the value of l/C is in the range from around 0.2 to 0.3, but when the value of W1/C is 0.35
It can be seen that when the value exceeds , the breathing rate suddenly increases and approaches the value of concrete produced by a conventional method.

Furthermore, although this figure shows the case of concrete, similar results were obtained experimentally in the case of mortar as well.

Therefore, according to the method of the present invention, a part of water for kneading is added to the precaulking cement, mechanical vibration is applied to this cement using a high-frequency vibrator, and then the remaining designed amount of water is added and stirred. By creating a highly viscous cement paste with very little breathing, it is possible to produce mortar and concrete with much higher strength and better fluidity than those made using the same composition using conventional methods. This greatly contributes to improving the quality of concrete structures and making construction more economical.

[Brief explanation of drawings]

Figure 1 is a flow diagram of a known concrete structure, Figure 2 is a flow diagram showing the manufacturing method according to the present invention, and Figure 3 is the compressive strength of the present method and the conventional method with various excitation times. Figure 4 is a diagram showing the strength curves comparing the method of the present invention with various amounts of initially added water and the conventional method, and Figure 5 shows the ratio of the amount of initially added water to the amount of cement. FIG. 6 is a diagram showing the relationship between mortar compressive strength and Wl/C, and FIG. 7 is a diagram showing the relationship between Wl/C and breathing rate.

Claims (1)

[Claims] 1. Of the water of a predetermined design mix in cement mortar,
First, water of 25 to 30 φ of cement weight is added to ordinary Portland cement and stirred, mechanical vibration is applied to cause liquefaction phenomenon, then the remaining amount of water in the designed mixture is added and stirred again, A method for producing high-strength mortar, which comprises obtaining high-strength mortar by kneading it with a designed amount of fine aggregate. 2. First, add 25 to 30 φ of water based on the weight of the cement in concrete, apply mechanical vibrations to cause liquefaction, and then add the remaining amount of water in the design mix. A method for producing high-strength concrete, which is characterized in that high-strength concrete is obtained by adding water to the mixture, stirring it again, and then kneading it with a designed amount of fine aggregate and coarse aggregate.