JPH0313302A - Improving method of slump value of fresh concrete - Google Patents

Abstract

PURPOSE:To attain concrete with workable high slump value, while the resistance due to consistency is minimized by a method in which when concrete is kneaded, the necessary amount of high-performance AE water-reducing agent is divided, and those divisions are then it is added to the material to be kneaded each at one segment of the total adding time in a batch process. CONSTITUTION:The necessary amount to be added of the AE water-reducing agent of high efficiency is divided into two parts in such a rate that primary additional amount is 20-50% and secondary additional amount is 80-50%. Said primary additional amount is added to the material composed of cement, fine aggregate and coarse aggregate together with a part of the water to be compounded and is primarily kneaded in a mixer. Next, the secondary additional amount is added into said kneaded material with the residual part of the water to be compounded, and then said materials are secondarily kneaded. The concrete having a slump value of 19-24cm exceeding 18cm of the standard slump value of the method (So method) in which all AE water-reducing agent is added at one time, is obtained by the method (S method) of adding each divided part. Said slump value is improved with the length of kneading time.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for improving the slump value of fresh concrete containing a high performance water reducer.

[Background of the invention]

As a concrete admixture, a high-performance AEM water-reducing agent has recently been developed that has a higher water-reducing effect than conventional AE water-reducing agents2.
For example, a high performance AE water reducer with the trade name Hozolith 5P-8N is available on the market.

However, there are many unknowns about the relationship between the mixing procedure of such high-performance AEN water reducing agents into concrete and the slump value, and in general, a designed amount of high-performance AE water reducing agents is added to the mixing raw materials all at once. A mixing method is used.

[Purpose of the invention]

The purpose of the present invention is to clarify the influence of the blending procedure of a high-performance AE water reducer on the slump value of fresh concrete, and to obtain workable concrete with a high slump value.

(Structure of the Invention) The present invention, when mixing concrete by adding a high performance AEi%! water agent, divides the necessary addition amount of the high performance iAE water reducer and divides the addition time into batches. The present invention provides a method for improving the slump value of fresh concrete, which is characterized by adding the following formula to the kneaded material.

Particularly, in the present invention, the necessary addition amount of the high-performance AE water reducing agent is divided into two at a ratio of primary addition 4i: 20 to 50% and secondary addition amount: gO to 50%.

(a) The primary addition amount is added to the material consisting of cement, fine aggregate, and coarse aggregate together with 1 part of the blended water and kneaded for the first time, and then the secondary addition amount is blended into this kneaded material. A method of secondary kneading by adding with the rest of the water.

What, the amount of the primary addition is added to the cement together with 1 part of the blended water and kneaded, fine aggregate and coarse aggregate are added to the resulting paste and kneaded, and the secondary addition is added to the resulting kneaded product. A method of final kneading by adding the same amount along with the rest of the blending water.

(C), the primary addition amount was added to the air-mixed material of cement and fine aggregate together with 1 part of the blended water and kneaded, and the coarse aggregate was added to the obtained mortar and kneaded. A method of final kneading by adding the secondary addition amount to the kneaded material together with the remainder of the blended water.

This advantageously provides a solution for improving the slump value. Regardless of which method is used, silica fume is used when blending cement.

At least one of fly ash or pulverized blast furnace slag
High strength can be achieved by blending a fine seed powder admixture.

[Function] According to the divided addition of the high performance AE water reducing agent according to the present invention, -
Compared to the case of bulk addition, the loss due to adsorption of the high-performance AE water reducer to the surface of cement and aggregate is reduced, and the entire amount can perform its original function, resulting in less resistance due to consistency. , it is possible to obtain workable concrete with a high slump value.

〔Example〕

Ordinary Portland cement: Silica Fumenia 9 with a specific surface area of 232,000 c+m”/H of 580 kg/rrf
kg#rf Fine aggregate from Fujikawa: 692kg/rrf
Coarse aggregate from Tsukui: 850kg/high performance 8E water reducer (trade name: Hozolith 5P-8%):
181! /+w' were mixed in a mixer according to the following blending procedure at a constant rate of -175 kg/pot per unit of water and a water binder ratio of -25%.

[Blending procedure 1... called So method] Add the above ingredients all at once to a mixer and mix.

[Blending procedure 2... called S method] High-performance AE water reducer is added in the first addition amount -40%, and the second addition!
Divide into 2 parts at a ratio of 1-60% (by weight), add the primary addition amount to the material consisting of cement, silica fume, fine aggregate and coarse aggregate together with 1 part of blended water, and knead the mixture for the first time.
Next, the secondary addition amount is added to this kneaded material together with the remainder of the blended water for secondary kneading.

[Blending procedure 3... called P method] Divide the high performance AE water reduction into two parts at the ratio of primary addition amount - 40% and secondary addition amount - 60% (weight basis), and mix the primary addition amount. Add it to cement and silica fume together with 1 part of water and knead it, add fine aggregate and coarse aggregate to the obtained paste and knead it, and add the secondary addition amount to the obtained kneaded product together with the rest of the blended water. Add and final knead.

[Referred to as compounding method l1liiI4...M method] The high-performance AE water reducer is divided into two parts at the ratio of the primary addition amount - 40% and the secondary addition amount - 60% (by weight), and is mixed with cement, silica fume,
The primary additive amount is added to the blank wire material of fine aggregate along with 1 part of blended water and kneaded.

Coarse aggregate is added to the obtained mortar and kneaded, and the secondary addition amount is added to the obtained kneaded material together with the remainder of the mixing water for final kneading.

Table 1 shows the kneading times when each of the above methods was carried out. The slump bond of the obtained fresh concrete was measured, and the compressive strength of the hardened concrete was also measured. These results are shown in Table 2.

From the results in Table 2, S
It can be seen that the slump value at the time of kneading is significantly improved and the rate of decrease in the slump value is also reduced when the two divided addition methods according to the present invention are used, even if the materials and formulation used are the same, compared to the method.

Figure 1 shows the change in slump value when the high-performance AE water reducer is divided into two parts in the S method in the above-mentioned compounding procedure 1, and the ratio of the division ratio is changed and the ratio is compared to the 56 method. (The slump value in the S method is assumed to be 100.chi.) In addition, 5F-0 in Figure 1 indicates that m silica fume is added and the blending procedure is the 50 method.

From the results shown in Figure 19, when the high-performance AE water reducer is added in portions according to the present invention, the primary addition rate of the high-performance AE water reducer is approximately 20 to 50% (therefore, the secondary addition rate is approximately 80 to 50%).
It can be seen that the slump value improvement effect peaks at around 0%).

Furthermore, FIG. 2 shows the slump values at the time of kneading when the divided additions are carried out according to the nine methods of the present invention in relation to the kneading time (total kneading time). The numbers in parentheses for each method indicate the kneading speed (rp+w) of the mixer. From the results in Figure 2, it can be seen that the overall kneading time is longer (the slump value improves), but especially in the S method, this The influence of kneading time is significant.

Figures 3 and 4 show the changes over time after two kneading stages when a high-performance AE water reducing agent was added in portions using the S method. 1) Figure 4 shows the case of high speed rotation (80 rpm). In addition, in the symbol in Figure 1, 8, for example, S
L35N represents normal rotation with a kneading time of 135 seconds in the S method. These results show that the longer the kneading time, the lower the slump loss. In particular, the concretes 3225) 1 and S 270H in Fig. 4 are mixed at high speed and for a long time.

It can be seen that there is little change in slump over time, and it has excellent workability.

As can be seen in Table 2 above, even in the P method, the slump value after 60 minutes shows a higher value as the kneading time increases, and also when the rotation speed is increased. Even better results were obtained, indicating that concrete with good workability was obtained.

The results of the above examples can be summarized as follows.

(1) High-performance AEi [concrete with a slump value of 19 to 24 cm, which exceeds the target slump value of 18clII for the bulk injection method (method 30), is obtained by the split injection method (S method, P method and M method) according to the present invention. ) is obtained by

-(2) When the kneading speed is regular, the M method has the largest slump value immediately after kneading, and when the kneading speed is high, there is no big difference between the S method, P method, and M method (however, the slump value immediately after kneading is (3) The longer the kneading time, the better the slump value for both S method 1 P method 1M method. This is considered to be due to the action of the high performance AE water reducing agent.

(4) The change in slump value over time is the smallest in the S method and the P method, especially when the kneading speed is high and the kneading time is long.
Method and P method result in concrete with good workability.

(5) The compressive strength at 28 days of age of the 1M method tends to be higher by about 2.4% and 1.3% compared to the S method and the P method.

(6) Regardless of the method, the compressive strength at 28 days of age tends to be higher when the kneading time and high speed kneading are used.

(7) Regarding the strength of the initial material age, high-speed kneading is more advantageous than regular kneading.

As described above, according to the present invention, the performance of a high-performance AE water reducing agent can be efficiently brought out, and concrete with improved various properties including workability can be obtained.

It can greatly contribute to concrete construction.

[Brief explanation of drawings]

Figure 1 shows the relationship between the primary addition rate and slump value in the split addition method of the high-performance AE water reducer of the present invention in comparison with the conventional batch addition method. Figure 3 shows the relationship between the slump value of concrete and mixing time. Figure 3 shows the change in slump value over time when concrete is mixed at normal speed according to the method of the present invention. Figure 4 shows the relationship between the slump value of concrete and the mixing time. FIG. 2 is a diagram showing changes over time in slump values when high-speed mixing of concrete is performed.

Claims (5)

[Claims] (1) When mixing concrete with the addition of a high-performance AE water-reducing agent, the required amount of the high-performance AE water-reducing agent is divided into portions, and these are added to the mixed material in batches by dividing the addition time. A method for improving the slump value of fresh concrete. (2) The required amount of high-performance AE water reducing agent is the primary addition amount:
It is divided into two at a ratio of 20 to 50% and secondary addition amount = 80 to 50%, and the primary addition amount is added to the material consisting of cement, fine aggregate, and coarse aggregate together with a part of the blended water. 2. The method for improving a slump value according to claim 1, wherein the kneaded product is firstly kneaded, and then a second addition amount is added to the kneaded material together with the remainder of the blended water for second kneading. (3) The required amount of high-performance AE water reducing agent is the primary addition amount:
It is divided into two parts at a ratio of 20 to 50%, secondary addition amount: 80 to 50%, and the primary addition amount is added to cement together with a part of blended water and kneaded, and the resulting paste is mixed with fine aggregate, 2. The method for improving slump value according to claim 1, wherein coarse aggregate is added and kneaded, and the secondary addition amount is added to the resulting kneaded product together with the remainder of the blended water for final kneading. (4) The required amount of high-performance AE water reducing agent is the primary addition amount:
The primary addition amount is divided into two at a ratio of 20 to 50%, and the secondary addition amount: 80 to 50%, and the primary addition amount is added to the air-mixed material of cement and fine aggregate together with 1 part of the blended water and kneaded. 2. The method for improving slump value according to claim 1, wherein coarse aggregate is added to the obtained mortar and kneaded, and the secondary addition amount is added to the obtained kneaded product together with the remainder of the blended water for final kneading. (5) The method for improving slump value according to claim 2, 3 or 4, wherein at least one fine powder admixture of silica fume, fly ash or powdered blast furnace slag is mixed together when blending the cement.