JP7401340B2 - Concrete horizontal pour joint treatment method - Google Patents

Description

The present invention relates to a method for treating horizontal pour joints that occur during pouring when concrete is poured in layers upwards.

BACKGROUND ART Conventionally, when building large-scale concrete structures in civil engineering work, etc., concrete is poured in layers in an upward direction. At this time, once the concrete placement for the day is completed, concrete placement will be restarted across the dates, so the treatment of the boundary surface (horizontal pour joint) between the poured concrete and new concrete is This is important in ensuring quality.

Conventionally, the method used was to remove laitance from the surface of the lower layer concrete (which forms the horizontal pour joint) after it had hardened to some extent using wire brushing, chipping, etc. (referred to as green cut treatment), and then concrete was poured onto the upper layer. However, since this method is basically a manual process, it takes a lot of time and effort, and also has problems such as the generation of dust, which requires environmental protection measures.

Therefore, in recent years, treatment methods using setting retarders and seam treatment agents have been proposed and put into practical use. The former setting retarder is, for example, as shown in Non-Patent Document 1 below, after concrete is poured, when the bleeding water has run out, the setting retarder is applied uniformly over the concrete surface using a sprayer or the like. Once sprinkled, cure with a curing mat or sheet, and 6 to 24 hours after pouring, wash out the thin surface layer with a high-pressure washer (latance treatment) before pouring the next concrete. It is intended to do so.

For example, as shown in Non-Patent Document 2 below, the latter method is to spray the seam treatment agent after concrete is poured before the bleeding water finishes subtracting, and after curing for a predetermined period of time, to apply the seam treatment agent to the next concrete. This will enable concrete pouring to be carried out. In the case of this pour seam treatment agent, it has the advantage that a strong polymer concrete layer is formed at the pour joint by dispersing the pour seam treatment agent, so that there is no need to remove the laitance layer.

“Lugasol C concrete pouring joint treatment agent (surface setting retardant)” Sunhit Shokai Co., Ltd., [searched on February 12, 2020], Internet <URL: http://www.sunhit.co.jp/pdf /ruga.pdf ＞ “Concrete pouring surface treatment agent Joint Ace JA-40”, Lion Specialty Chemicals Co., Ltd., [searched on February 12, 2020], Internet <URL: https://www.lion-specialty-chem. co.jp/ja/catalog/06/sja40.php＞

However, in the case of the method using the setting retarder, it is necessary to spray the setting retarder after the concrete is poured and to remove the laitance using high-pressure water the next day, which requires a lot of work and time. In addition, there were other problems, such as the practical difficulty of pouring concrete on consecutive days.

On the other hand, in the case of the method using the seam treatment agent, work efficiency is improved in that there is no need to remove laitance, but there are still problems such as the need to spray the seam treatment agent after concrete pouring. There was a problem.

Therefore, the main object of the present invention is to provide a method for handling horizontal pouring joints that occur during pouring when concrete is poured in layers upwards, so that the pouring work can be done more labor-savingly than before. The objective is to further improve the integration of concrete at horizontal joints.

In order to solve the above problem, the present invention according to claim 1 provides a method for treating horizontal pour joints that occur during pouring when concrete is poured in layers upwards, comprising:
A first step of pouring a layer of concrete to which a super-retardant has been added in concrete pouring of the final layer on the lower stage up to the horizontal pouring joint;
After a predetermined time has elapsed, a second step of pouring a layer of concrete to which a hardening accelerator has been added in the first layer of concrete pouring starting from the horizontal pouring joint;
a third step of stirring and mixing a layer of concrete to which the super retardant has been added and a layer of concrete to which the hardening accelerator has been added;
There is provided a method for treating horizontal concrete joints, which is characterized by comprising a fourth step of sequentially pouring concrete upward in layers on the upper layer.

In the invention as claimed in claim 1 above, in pouring the final layer of concrete on the lower side leading to the horizontal pour joint, a layer of concrete to which a super retardant has been added is poured (first step), and after a predetermined time (the pour joint is poured). Interval: about 1 to 3 days), in the first layer of concrete pouring starting from the horizontal pouring joint, a layer of concrete with a hardening accelerator added was poured (second step), and the super retarder was added. The concrete layer and the concrete layer to which the hardening accelerator has been added are mixed by stirring (third step).

The super-retardant is added to the concrete and cast, which eliminates the need for spraying, and the hardening accelerator is also added to the concrete and cast, eliminating the need for spraying. Although it is necessary to stir and mix the layer of concrete containing the super retardant and the layer of concrete containing the curing accelerator, it is the same amount of work and effort as applying a vibrator, so it can be done at the same time. There will be no delay in work. As shown in the experimental examples below, a concrete layer in which a layer of concrete containing an ultra-retarder and a layer of concrete containing a hardening accelerator are stirred and mixed has high compressive strength and the occurrence of color unevenness is considerably reduced. The appearance is also better, and the integration of the concrete is even better than that of conventional ones.

In the present invention according to claim 2, the addition rate of the super-retarder is such that the penetration resistance value of the concrete layer to which the super-retarder is added is 0.1 N/mm2 or less during stirring and mixing in the third step. There is provided a method for treating horizontal pour joints in concrete according to claim 1, which is determined as a standard.

The invention according to claim 2 stipulates a method for determining the addition rate of the super retardant. It is generally known that cold joints occur at pour joints when the concrete penetration resistance value at the time of pour joints exceeds 0.1 N/mm2. Therefore, when determining the addition rate of the super retarder, it is important to ensure that the penetration resistance value of the concrete layer is 0.1 N/mm2 or less when mixing the concrete layer containing the super retarder and the concrete layer containing the hardening accelerator. One thing can be used as a standard.

As the present invention according to claim 3, the horizontal pour joint treatment of concrete according to claim 1 or 2, wherein the solution of the super retardant and the hardening accelerator is converted into a part of the unit water amount and mixed into the concrete. A method is provided.

The invention according to claim 3 provides that the solution of the super retardant and the hardening accelerator is converted into a part of the unit water amount and mixed into the concrete. In this method, the solution of the super retardant and the curing accelerator is added to the concrete rather than being sprayed, so it is desirable to convert it as a part of the unit water amount so as not to increase the unit water amount.

As described in detail above, according to the present invention, when pouring concrete upward in layers, the horizontal pour joints that occur during pouring can be handled more labor-savingly than before. At the same time, it becomes possible to further improve the integration of concrete at horizontal pour joints.

FIG. 2 is a cross-sectional view of concrete according to the method for treating horizontal concrete joints according to the present invention. FIG. 2 is a step diagram (part 1) of the horizontal pour seam processing method. It is a procedure diagram (part 2) of the horizontal pour seam processing method. It is a procedure diagram (part 3) of the horizontal pour seam processing method. 2 is a graph showing the relationship between the time required to obtain a penetration resistance value of 0.1 N/mm2 and the addition rate of a super retarder. It is a graph showing the results of a compressive strength test in an example.

Embodiments of the present invention will be described in detail below with reference to the drawings.

The present invention is a method for treating horizontal pour seams 1 that occur during pouring when concrete is poured in layers upwards as shown in FIG. This is based on the procedure.

(1st step)
In the first step, as shown in FIG. 2, a layer 3 of concrete to which a super retardant has been added is poured in the final layer of concrete on the lower stage up to the horizontal pour joint 1.

In the concrete pouring process, a plan for concrete pouring is determined in advance based on the scale and shape of the structure and taking into account the daily concrete pouring capacity.

Concrete pouring work for one day usually involves compaction using a vibrator, so it is common to divide the height of concrete into two or more layers each day. At this time, the height of one layer of concrete is determined by considering compaction capacity, etc., but the standard height h1 of one layer of concrete is 40 to 50 cm or less.

The types of cement used for concrete are not particularly limited, but include ordinary Portland cement, early strength Portland cement, ultra early strength Portland cement, moderate heat Portland cement, white Portland cement, sulfate-resistant Portland cement, and low heat generation Portland cement. Various types of Portland cement such as Portland cement, and mixed cements such as blast furnace slag cement, fly ash cement, and silica cement can be used. Note that it is desirable to use a general water reducing agent such as a lignin sulfonate type, a polyol type, or an oxycarboxylate type, a high performance water reducing agent, and a high performance AE water reducing agent. Among these, high-performance water reducing agents such as polyalkylaryl sulfonate-based and melamine resin sulfonate-based, and high-performance AE water-reducing agents based on polycarboxylate, which have a large water reduction rate, are preferred. In addition, in the figure, illustrations of reinforcing bars, formwork, etc. are omitted, and only the concrete portion is shown.

The super retarder is an additive that can arbitrarily adjust (slow down) the setting speed of concrete by adding it, and it adsorbs to the surface of cement particles and temporarily blocks contact between water and cement. It delays the setting of concrete. According to JIS A 0203, an admixture used to delay the hydration reaction of cement and prolong the time required for setting is defined as a setting retarder. Set retarders are generally classified into retarders and ultra-retarders.Admixtures that have a short-term retarding effect within a few hours are called retarders, while admixtures that have a long-term retarder effect that lasts from several hours to several days are called retarders. It is called a super retardant. The latter "super retardant" is used in the present invention.

Super retardants are generally classified into inorganic compounds and organic compounds. Examples of the former inorganic compound super retardant include zinc chloride, zinc carbonate, lead monoxide, phosphate, silicofluoride, borax, magnesia salt, and the like. Super retardants for the latter organic compounds include sugars and their derivatives, lignin sulfonates, organic acids and their acid salts, oxycarboxylate salts such as citrates and gluconates, cellulose derivatives, and polyvinyl alcohol. Examples include water-soluble polymers. In general, organic compound retardants are larger than inorganic compounds, and when used as a super retardant, organic compounds are considered advantageous.

The addition rate of the super-retarder is preferably determined based on the fact that the penetration resistance value of layer 3 of the concrete to which the super-retarder is added during stirring and mixing in the third step is 0.1 N/mm2 or less. . When performing horizontal pour joints, cold joints are said to occur if the penetration resistance value exceeds 0.1 N/mm2. Therefore, it is desirable to control the penetration resistance of the concrete layer 3 to which the super retardant has been added to be 0.1 N/mm2 or less at the start of concrete pouring after a predetermined period of time.

The interval (time) between successive shots is approximately 24 to 72 hours, and has a wide range of time. In order to control the penetration resistance value of the concrete layer 3 to which the super retardant was added to be 0.1N/mm2 or less, an indoor test was conducted in advance as shown in Figure 5, and the penetration resistance value was 0.1N. It is desirable to have a graph showing the relationship between the time required to obtain /mm2 and the addition rate of the super retarder used. By obtaining such a graph, it becomes possible to easily determine the addition rate of the super retardant even if the interval between pouring changes. Note that the penetration resistance value can be measured according to JIS A 1147 concrete setting time test method.

Furthermore, in order to prevent the unit amount of water from increasing due to the addition of the super retardant solution, it is desirable that the amount of the super retardant solution added is converted into a part of the unit water amount and mixed into the concrete.

The height h2 of the concrete layer 3 to which the super-retardant has been added is 1/2 to 1/2 of the height h1 of one layer of standard concrete 2, taking into consideration the stirring in the third step described below. It is desirable to set the height to about 3.

(Second step)
In the second step, after a predetermined time has elapsed, that is, after the pouring interval time has elapsed, a layer 4 of concrete to which a hardening accelerator has been added is poured in the first layer of concrete starting from the horizontal pouring seam 1. Set up

The hardening accelerator is an additive that accelerates the hardening of concrete by promoting the formation of hydration products leached from cement, and is specified as one of the chemical admixtures for concrete in JIS A 6204. There is.

The curing accelerators are generally classified into inorganic compounds and organic compounds. The hardening accelerators for the former inorganic compounds include chlorides such as calcium chloride (limited to plain concrete), nitrates and nitrites, highly soluble sulfates and sulfites, and aluminum such as alums and alumite. Known compounds include thiosulfate, thiocyanate, and chromate. As curing accelerators for the latter organic compounds, formates, acetates, and amino acid compounds are known.

The amount of curing accelerator added varies greatly depending on the type of curing accelerator, but is generally 1 to 5% by weight based on the weight of the binder (cement). In order to quickly harden the three layers of concrete to which the super retardant has been added, it is added in a larger amount than usual. In any case, it is desirable to carry out test preparations to confirm that the target concrete workability is achieved.

The height h3 of the layer 4 of concrete to which the curing accelerator has been added is 1/2 to 1/2 to 1 of the height h1 of one layer of standard concrete 2, taking into consideration the stirring in the third step described below. It is desirable to set the height to about /3.

(Third step)
In the third step, as shown in FIG. 3, a layer 3 of concrete to which the super-retardant has been added and a layer 4 of concrete to which the hardening accelerator has been added are stirred and mixed. It is desirable that the stirrer 6 used be one that can be held and operated by a worker. The stirring blade portion at the tip is inserted into the concrete and moved horizontally to stir and mix the layer 3 of concrete to which the super retardant has been added and the layer 4 of concrete to which the hardening accelerator has been added.

(Fourth step)
After that, according to standard concrete pouring, concrete 5 is poured upwardly on the upper layer side of the layer in which layer 3 of concrete added with the super retardant and layer 4 of concrete added with the hardening accelerator are stirred and mixed. The concrete will be poured in layers in order. Note that the standard height h4 of one layer of concrete 5 is 40 to 50 cm or less.

Next, compressive strength tests were conducted on concrete specimens obtained by the method for treating horizontal pour seams of concrete according to the present invention and concrete specimens obtained by other methods for treating horizontal pour seams. We verified the effectiveness. In addition, for the ultra-retardant manufactured by Florrick Co., Ltd. used, a graph (Fig. 5) showing the relationship between the time required to obtain a penetration resistance value of 0.1 N/mm2 and the addition rate of the ultra-retarder was obtained.

1. Concrete mix Table 1 shows the mix of concrete used.

2. Graph of the relationship between the time to obtain a penetration resistance value of 0.1N/mm2 and the addition rate of super retardant The time to obtain a penetration resistance value of 0.1N/mm2 and the addition rate of super retardant for the super retardant made by Frolic Co., Ltd. used A graph showing the relationship between The addition rate of the super retardant was determined at five points: C×(0, 0.40, 0.55, 0.70, 0.85). The results are shown in FIG. For reference, a penetration resistance value test was also conducted on two super retardants from other companies (manufactured by Company A and Company B) with an addition rate of C x 0.7%. The super retardant was added as part of the unit water amount immediately after mixing the concrete.

In Figure 5, once the pouring interval time is determined, draw a horizontal line at that time and easily determine from the graph that it is sufficient to add a larger amount of super retardant than the addition rate at the point where it intersects with the relational curve. be able to. In addition, the case where the pouring interval was 40 hours was shown in the figure. In this case, since the point of intersection with the curve is the addition rate of 0.75%, it can be seen that the addition rate of the super retardant should be 0.80%.

3. compression test
(1) Regarding the super retardant and curing accelerator used The super retardant and curing accelerator used were as shown in Table 2 below.

圧縮試験の供試体１～３の形状は、いずれもφ150×300とした。供試体１は、高さ方向に３分割し、下層の高さ100mmに遅延剤0.8%を添加したコンクリートを充填し、中間層及び上層の200mmの空間にベースコンクリート（con1）を充填した。供試体２は高さ方向に３分割し、下層の高さ100mmに遅延剤0.8%を添加したコンクリートを充填し、４０時間経過後に中間層の高さ100mmに硬化促進剤5%を添加したコンクリートを充填し、上層の高さ100mmにベースコンクリート（con1）を充填した。供試体３は高さ方向に３分割し、下層の高さ100mmに遅延剤0.8%を添加したコンクリートを充填した後、４０時間経過後に中間層の高さ100mmに硬化促進剤5%を添加したコンクリートを充填し、遅延剤0.8%を添加したコンクリートと混合撹拌し、上層の高さ100mmにベースコンクリート（con1）を充填した。 The test items for the concrete specimens were as shown in Table 3 below.

The shapes of specimens 1 to 3 for the compression test were all φ150×300. Specimen 1 was divided into three parts in the height direction, and the lower layer, 100 mm in height, was filled with concrete containing 0.8% retardant, and the 200 mm spaces in the middle and upper layers were filled with base concrete (con1). Specimen 2 was divided into three parts in the height direction, and the lower layer, 100mm high, was filled with concrete containing 0.8% retardant, and after 40 hours, the middle layer, 100mm high, was filled with concrete containing 5% curing accelerator. The upper layer was filled with base concrete (con1) to a height of 100 mm. Specimen 3 was divided into three parts in the height direction, and the lower layer, 100 mm high, was filled with concrete containing 0.8% retarder, and after 40 hours, 5% curing accelerator was added to the middle layer, 100 mm high. Filled with concrete, mixed and stirred with concrete to which 0.8% retarder was added, and then filled with base concrete (con1) to a height of 100 mm in the upper layer.

FIG. 6 shows the results of a compression test performed on these specimens 1 to 3. Compared to Specimen 1 and Specimen 2, the compressive strength of Specimen 3 according to the present invention was the highest in all cases of 3-day, 7-day, 14-day, and 28-day strength.

In addition, color unevenness was observed in both specimens 1 and 2 in terms of appearance, but specimen 3 had a clean surface without any color unevenness.

1...Horizontal pour joint, 2.5...Concrete, 3...A layer of concrete to which a super-retardant has been added, 4...A layer of concrete to which a hardening accelerator has been added, 6...Agitator

Claims (3)

A method for treating horizontal pour joints that occur during pouring when concrete is poured in layers upwards,
A first step of pouring a layer of concrete to which a super-retardant has been added in concrete pouring of the final layer on the lower stage up to the horizontal pouring joint;
After a predetermined time has elapsed, a second step of pouring a layer of concrete to which a hardening accelerator has been added in the first layer of concrete pouring starting from the horizontal pouring joint;
a third step of stirring and mixing a layer of concrete to which the super retardant has been added and a layer of concrete to which the hardening accelerator has been added;
A method for treating horizontal concrete joints, comprising a fourth step of sequentially pouring concrete upward in layers on the upper layer. The addition rate of the super-retarder is determined based on the fact that the penetration resistance value of the concrete layer to which the super-retarder is added is 0.1 N/mm2 or less during stirring and mixing in the third step. Method for treating horizontal concrete joints. 3. The method for treating horizontal concrete joints according to claim 1, wherein the solution of the super retardant and the hardening accelerator is converted into a part of the unit water amount and mixed into the concrete.

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