JP2013256804A - Management method of spraying time of concrete placing joint treatment agent - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a management method capable of easily grasping and managing an appropriate spraying time of a concrete placing joint treatment agent which can ensure performance equivalent to a normal placing joint treatment only by spraying at a construction site.SOLUTION: In a management method of a spray time of a concrete placing joint treatment agent, for a placed concrete surface, an N-type penetration test is performed in which a penetration length of a rammer used in JIS A1101 (a concrete slump testing method) from the placed concrete surface when the rammer is made to freely drop with a drop distance of 750 mm, and a placing joint treatment agent is sprayed on the concrete surface when a penetration amount obtained by the N-type penetration test is within a range of 20-40 mm.

Description

  The present invention relates to a method for managing the timing for spraying a jointing agent for concrete.

  In concrete construction, various joint treatment agents have been developed that are able to ensure the same performance as ordinary joint processing (method of performing joint processing and exposing coarse aggregate particles) just by spraying. Applied in the field. In this case, it is applied for the purpose of reducing labor during the transfer process, the problem of treated water, and the uniformity of the treatment quality, but there are still many parts that have not been clarified about their characteristics, and quantitative information is available. Currently there are few.

  Conventional joint processing methods include a pre-curing treatment method, a post-curing treatment method, and a method using these in combination. As a pre-hardening treatment method, a method of removing a thin layer on the surface of concrete with high-pressure air or water after the setting of the concrete is set to expose coarse aggregate particles is used. This treatment method is efficient when the joints are relatively wide, but if the time suitable for the joints is overdue, the strength of the concrete becomes too high and it is difficult to expose coarse aggregate particles. It is. In order to alleviate such construction restrictions, a setting retarding agent can be sprayed on the concrete joint to delay the hardening of the thin layer on the concrete joint surface and to significantly extend the treatment time. The method is common.

  In addition, the iron weight is allowed to fall freely on the concrete surface immediately after placement, and the surface trace size due to the collision of the iron weight body is measured. An apparatus / method for measuring the degree has been proposed (Patent Document 1). In addition, there is a concrete overlay management method that measures the electrical conductivity of the placed concrete to continuously grasp the progress of the setting of the concrete and obtain the optimum concrete placement time interval. It has been proposed (Patent Document 2).

Japanese Patent Application Laid-Open No. 08-94612 JP2011-117235A

  The spraying agent can ensure the same performance as a normal casting process (setting retarder + high-pressure water) just by spraying, but the timing (timing) of spraying the jointing agent is important. ing. For example, the manufacturer's recommended spraying timing is the time when bleeding water is drawn into the concrete or when the bleeding water is wiped off, but it is basically a subjective judgment based on visual observation. is there. Thus, since it was basically management by visual observation, there was a case where the optimum timing for spraying the joining agent was missed due to a delay in judgment. In addition, visual management is largely based on the subjectivity of the practitioner, making it difficult to make objective judgments.

  In view of the problems of the prior art as described above, the present invention easily grasps an appropriate spraying timing of a concrete transfer processing agent that can ensure the same performance as a normal transfer processing only by spraying at a construction site. The purpose is to provide a management method that can be managed.

  In order to achieve the above object, according to the present invention, the method for controlling the spraying time of the concrete transfer treatment agent is as follows. When an N-type penetration test is performed to measure the penetration length from the concrete surface of the cue stick when freely dropped, and the penetration amount obtained by the N-type penetration test is within a range of 20 to 40 mm, It is characterized by spraying the jointing agent on the concrete surface.

  The inventors of the present invention can use the penetration amount by the N-type penetration test as an index for quantitatively determining the optimum spraying timing of the joint treatment agent, and the penetration amount is within a range of 20 to 40 mm. It has been found that a certain time is the optimum spraying time of the joint treatment agent. Thereby, it is possible to easily grasp and manage an appropriate spraying time of the concrete transfer processing agent that can ensure the same performance as the normal transfer processing only by spraying at the construction site.

  According to the management method of the present invention, it is possible to objectively determine the appropriate spraying timing of the concrete jointing agent that can ensure the same performance as a normal jointing treatment only by spraying according to the penetration amount measured by the N-type penetration test. This makes it possible to make a quantitative determination instead of a conventional visual subjective determination. For this reason, it is possible to manage the appropriate spraying timing of the jointing agent using the penetration amount by the N-type penetration test in any concrete blend.

  Moreover, since the N-type penetration test can be easily performed at the construction site and there is no place restriction, the management method of the present invention can be easily applied to any concrete construction site.

  Moreover, the said joint treatment agent can use the chemical | medical agent which has a resin emulsion as a main component.

  According to the method for managing the spraying time of the concrete transfer treatment agent according to the present invention, it is possible to easily set an appropriate spraying time of the concrete transfer processing agent at the construction site, which can ensure the same performance as the normal transfer processing only by spraying. It can be grasped and managed.

It is a flowchart for demonstrating the management method of the concrete jointing agent dispersion | spreading time by this embodiment. It is a conceptual diagram for demonstrating the N type penetration test used in the management method of FIG. It is the schematic for demonstrating preparation of the specimen in this experiment example. It is a detailed view of the direct tensile test in this experiment example. It is a figure which shows the outline | summary of the air permeability test in this experiment example. It is a figure which shows the tensile strength (average) of each case in this experiment example. It is a figure which shows the air permeability coefficient of each case in this experiment example. It is a figure which shows the penetration amount of each case in this experiment example.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. FIG. 1 is a flowchart for explaining a method for managing a concrete jointing agent spraying time according to this embodiment. FIG. 2 is a conceptual diagram for explaining the N-type penetration test used in the management method of FIG. 1 (“Cold Joint Problem and Countermeasures in Concrete Structures” (Japan Society of Civil Engineers, issued July 31, 2000)).

  First, the N-type penetration test will be described with reference to FIG. The N-type penetration test is used as a simple method for judging cold joints. It is a simple method for judging cold joints from changes over time in the amount of penetration when a thrust rod used in JIS A1101: 2005 (concrete slump test method) is dropped. It is one of the judgment methods and can be easily implemented at the concrete construction site.

  That is, as shown in FIG. 2, a thrust bar 11 having a diameter of 16 mm and a length of 500 mm made of a round bar made of steel or metal and having a hemispherical tip is disposed at the upper end of a PVC pipe 10 having a diameter of 25 mm and a length of 1000 mm. 11 is aligned with the center 11a (position of 250 mm from the tip), and the PVC pipe 10 placed in the vertical direction on the concrete surface S is used as a guide to freely fall onto the placed concrete surface S. The fall distance at this time is 750 mm. The PVC pipe 10 is pulled out, and the length of the stick 11 penetrating from the concrete surface S is measured and set as the penetration amount.

  Next, with reference to FIG. 1, steps S01 to S04 of the method for managing the concrete jointing agent spraying time according to the present embodiment will be described.

  First, concrete placement is performed at the construction site (S01), and when spraying of the joint treatment agent is required, an N-type penetration test is performed on the placed concrete surface S as shown in FIG. 2 (S02). ).

  If the penetration amount in the N-type penetration test is within the range of 20 to 40 mm, it is judged that the spattering agent is properly distributed (S03), and the spouting agent is applied to the cast concrete surface S. (04).

  When the penetration amount by the N-type penetration test exceeds 40 mm (S03), after a predetermined time has passed, the process returns to step S02 and the N-type penetration test is performed again.

  In addition, the N-type penetration test may be performed a plurality of times at the same time, and the spraying timing of the joint treatment agent may be determined using the average value as the penetration amount.

  In addition, it is preferable to carry out preliminary tests such as a bleeding test and a proctor penetration test, grasp the bleeding characteristics and setting characteristics of the concrete in advance, and determine the timing for performing the N-type penetration test.

  As will be apparent from the results of experiments and research described later, the present inventors can use the amount of penetration by the N-type penetration test as an index for quantitatively determining the optimum spraying timing of the joint treatment agent. I found out. That is, the optimum spraying timing (timing) of the joining treatment agent is when the penetration amount is in the range of 20 to 40 mm.

  According to the management method of the present embodiment, the appropriate spraying timing of the concrete jointing agent that can ensure the same performance as the ordinary jointing treatment only by spraying is objectively determined by the amount of penetration measured by the N-type penetration test. Therefore, it is possible to make a quantitative determination instead of the conventional subjective determination by visual observation. Therefore, it is possible to control the appropriate spraying timing of the joint treatment agent using the penetration amount by the N-type penetration test in any concrete blend.

  Moreover, since the N-type penetration test can be easily performed at the construction site and there is no place restriction, the management method of this embodiment can be easily applied to any concrete construction site.

  In actual concrete construction, the state of the joint interface such as the bleeding state and the degree of progress of the setting of the concrete is confirmed by visual observation, and is managed by the penetration amount by the N-type penetration test. It is possible to manage by adding a quantitative judgment index to the qualitative judgment about the appropriate spraying time.

[Experimental example]
Next, an experimental example by which the present inventors have found that the amount of penetration by the N-type penetration test can be used and is appropriate as an index for quantitatively determining the optimum spraying timing of the joint treatment agent. This will be described below.

(Experiment overview)
In this experimental example, three types of experiments, roughly divided into mechanical performance, durability performance, and on-site management methods, were conducted. The examination items are shown in Table 1. In the mechanical performance experiment, we focused on the tensile stress that is considered to be a direct factor in the occurrence of cracks, and evaluated the tensile resistance of the joints from the direct tensile test. In the durability performance experiment, an air permeability test (Torrent method) was conducted for the purpose of grasping the denseness of the surface layer of the joint. In addition, an N-type penetration test, which is usually used as one of the indicators of cold joint determination, was conducted as an experiment on site management techniques.

(Experimental case)
The test cases were made into 7 cases in which case 7 of normal transfer treatment was added to 6 cases 1 to 6 shown in Table 2 according to spraying agent spraying timing. Prior to this experiment, a preliminary test (bleeding test / procter penetration test) was carried out, and the spreading time was determined by grasping the bleeding characteristics and setting characteristics of the concrete in advance. Of these, for Case 5 (the time when bleeding water is drawn), it is difficult to determine the specific elapsed time, so for convenience, the intermediate time between Case 3 (200 minutes) and Case 6 (300 minutes) (250 Minutes).

(Specimen preparation)
The direct tensile test was performed on the core specimen, and the specimen was collected by drilling a core from a slab-like concrete member provided with joints having different spraying times shown in Table 2. In addition, Table 3 and Table 4 show the concrete materials used, the composition, and the fresh properties. The core-collecting member had the shape shown in FIG. 3, and after the first layer of concrete was cast, the joint treatment agent and the setting retarder were used at the standard application amount recommended by the manufacturer. In Case 7, the weak layer on the surface was removed using high-pressure water the next day to expose coarse aggregate particles. The second layer was driven 10 days after the first layer. In addition, about the specimen for a direct tensile test, the insert was previously installed in the core drilling center position so that the loading test by a universal testing machine could be performed (refer FIG. 4).

(Joining agent)
The pour-in treatment agent is a chemical having a resin emulsion as a main component, and has a merit that a pour-in treatment can be performed only by spraying after placing the concrete. The following three factors are believed to have a significant impact on the quality of the transfer process using resin emulsions (Toshinobu Maenaka, Shoji Monnaka, Hiroshi Morita, Atsushi Ito: Study on joint surface treatment, Annual report of concrete engineering, Vol.23, No.2, pp.1201-1206, 2001.6).
(A) Bonding force of the modified layer of old concrete (anchor effect)
(B) Immobilization of latency components (resin modification effect)
(C) Bonding force between new concrete and modified layer (chelate effect)
In this experimental example, since the viscosity of the resin emulsion is relatively small, it can be expected to penetrate into the fragile layer of the concrete surface layer. (A) It is thought to have an effect on the bond strength (anchor effect) of the modified layer of old concrete The jointing agent mainly composed of PAE emulsion was used.

(Test method)
Among the evaluation items in this experimental example, the tensile strength was evaluated by a direct tensile test.
Various methods of direct tensile testing have been proposed, but the universal testing machine is designed by embedding the insert in advance inside the specimen and connecting it to the loading jig. Loading is possible. The connecting part between the loading jig and the insert has a pin structure, and transmits only the axial force. In addition, the density of the surface layer of the joint processing section was evaluated by the permeability test (Torrent method) (Concrete Technology Series 80, Concrete Quality and Durability Performance Verification System Research Subcommittee (335 Committee) Results of Structure Surface) Report and Symposium Summary Collection, Japan Society of Civil Engineers, pp30-36). The air permeability test is a non-destructive test that can repeatedly measure the air permeability of the concrete on the surface layer in-situ. As shown in Table 5, the surface air permeability quality is divided into 5 stages based on the air permeability coefficient obtained from the test. And evaluated.

  The surface air permeability tester is composed of a chamber, a vacuum pump, a control panel, and a measuring instrument, and the chamber has a double structure as shown in FIG. By sucking air from the lateral direction in the outer chamber, sucking air from the inner chamber, applying negative pressure to the concrete for a certain period of time, and measuring the change over time until this pressure recovers Calculate the air permeability coefficient. The calculation formula for the air permeability coefficient is composed of Poisseuille's equation and Boyle-Charles law, which is the ideal gas equation of state. The following formula (1) shows the formula for calculating the air permeability coefficient.

Where, k: air permeability coefficient (m ² ), μ: air viscosity coefficient (Nsm ^-2 ), Vc: measured air volume (m ³ ), ε: porosity of concrete (m ³ m ^-3 ), A : Chamber cross-sectional area (m ² ), P1: Pressure in the inner chamber (time function) (Nm ^-2 ), dP1 / dt: Derivative of time t (Nm ^-2 sec ^-1 ), Pa: Atmospheric pressure (Nm ^-2 ).

On the other hand, N-type penetration test, which is used as a simple method for determining cold joints, was conducted for experiments related to on-site management techniques for spraying time, considering that it can be easily performed at the construction site. As shown in Fig. 2 above, the N-type penetration test determines the cold joint from the time-dependent change in the amount of penetration when the thrust bar used in JIS A1101 (concrete slump test method) is dropped (fall distance = 750 mm). This is one of the simple determination methods to be performed. In general, cold joints have a penetration resistance value in the range of 0.01 to 1.0 N / mm ² , and the N-type penetration test has high detection sensitivity in this range, so it is considered suitable for management in a wide range ( Concrete Library 103, Cold Joint Problems and Countermeasures for Concrete Structures, Japan Society of Civil Engineers, pp51-643). The dimensions of the test body were 500 × 500 × 500 mm, and the test was carried out approximately at the elapsed time from the start of mixing shown in Table 2 above.

(Experimental result)
A bleeding test (JIS A1123) and a proctor penetration test (JIS A 1147) were conducted in parallel with the preparation of the bleeding / condensation property specimen. The bleeding amount was 0.06 cm ³ / cm ² , the bleeding rate was about 1.41%, and the cumulative bleeding amount reached the maximum after about 200 minutes from the start of mixing. The beginning of the setting was about 350 minutes from the start of mixing, and the end was after about 500 minutes.

Direct tensile strength table 6 shows a list of direct tensile test results, and FIG. 6 shows a comparison of average tensile strength. The tensile strength is that after 28 days from the second layer implantation. Except Case 2, the tensile strength tends to increase in the order of Case 1 to Case 7. Further, the difference in tensile strength between cases 4 to 6 is relatively small. On the other hand, Case 1 has the lowest tensile strength, and Case 7 has the highest tensile strength. However, since the case 7 Case 4-6 whereas was 1.5 N / mm ² approximately on average was about 1.3~1.4N / mm ^2, the tensile strength by using a DaTsugi treatment agent There was no tendency to be much lower than normal transfer processing. From this, it is considered that a tensile strength almost equivalent to that of a normal joining process can be expected if an appropriate usage method and an appropriate spraying time are strictly observed.

The air permeability coefficient table 7 and FIG. 7 show a list of air permeability test results and a comparison of air permeability coefficients in each case. The spraying time (minutes) in the table indicates the elapsed time from the start of mixing of concrete. The value of the air permeability coefficient in each case is in the range of 0.01 to 1.0 (× 10 ⁻¹⁶ m ² ), the air permeability grade is “3 to 2”, and the air permeability evaluation is in the range of “general to good”. From this result, the difference in the air permeability coefficient due to the difference in the spraying time is relatively small, and it was not possible to confirm a clear tendency that the denseness of the joining seam becomes extremely small by using the joining treatment agent. However, in Case 4 and Case 5, the variation in measured values was small compared to the other cases. Although there is no significant difference in the denseness of the joint interface due to the difference in spraying timing, it is possible to ensure stable processing quality by spraying using the timing of Case 4 or Case 5 as a guide. Suggests that. In addition, since the air permeability evaluation of case 5 is only “good” in all cases, it is considered appropriate to use the timing of case 5 as a guide in terms of processing quality. The reason for the small variation in Cases 4 and 5 compared to other cases is considered to be dominated by the effect of the amount of moisture present at the joint interface. Cases 4 and 5 are assumed to have a lower degree of dilution of the treatment agent because there is less moisture at the joint interface than in other cases. Further, in case 5, it is surmised that the treatment agent was drawn into the inside together with bleeding water, and the permeability coefficient was reduced because the penetration depth was larger than in case 4. In Case 6, the cause of the large variation in the air permeability coefficient is not clear, but it can be mentioned that there was a local difference to the extent that the condensation progressed and the treatment agent was drawn into the concrete.

Penetration amount in N-type penetration test Table 8 shows a list of penetration amounts of N-type penetration test in each experimental case. The rows in this table indicate the difference in spraying timing of the joint treatment agent, and the column indicates the time when the N-type penetration test was performed. It can be confirmed that the penetration amount in each experimental case gradually decreases with time. FIG. 8 shows a graph in which this list is replaced with the correlation between the elapsed time and the penetration amount. The horizontal axis of FIG. 8 is the elapsed time from the start of mixing, and each plot shows the average value of three N-type penetration tests. From this result, there was no significant difference in the amount of penetration due to the difference in spraying treatment agent spraying timing. A relatively large variation in penetration was observed at an elapsed time of about 90 minutes, but the tendency gradually decreased with the passage of time, and after 200 minutes, the variation was within the range of 20 to 40 mm. This is mainly due to the presence or absence of coarse aggregate at the point where the tip falls, but as the setting of the concrete progresses, the mortar part other than the coarse aggregate hardens, so the effect can be gradually reduced. Can be guessed.

  From the results of the above-mentioned direct tensile test and air permeability test, the results of case 4 (at the time of maximum bleed wiping) and case 5 (at the time when bleeding water is drawn in) are considered to be appropriate as the timing of spraying the treatment agent Met. That is, in case 4 (spraying time 200 minutes), the penetration amount at the test time 200 minutes and 250 minutes is 27 mm to 18 mm from Table 8 and FIG. 8, and in case 5 (spraying time 250 minutes), 38 mm to 27 mm. That is, it can be confirmed that the penetration amount of the N-type penetration test corresponding to these timings (case 4 and case 5) is in the range of about 20 to 40 mm from FIG. In this case, the N-type penetration test is carried out at the construction site, and it is considered that the optimum spraying time of the joint treatment agent can be managed by setting the penetration amount in the range of 20 to 40 mm. Actually, it is not managed only by the N-type penetration test, but by visually confirming the state of the joint interface (for example, the bleeding state and the degree of progress of the setting of the concrete) and further using this N-type penetration test together, We think that it will be possible to add a quantitative judgment index to the qualitative judgments made so far.

  According to the above experimental example, the penetration amount of the N-type penetration test corresponding to the appropriate spraying time is in the range of about 20 to 40 mm, and the N-type penetration test with this range as a guide is performed as a field management technique. Therefore, it is thought that the optimal spraying time can be quantitatively grasped.

  As mentioned above, although the form and experiment example for implementing this invention were demonstrated, this invention is not limited to these, A various deformation | transformation is possible within the range of the technical idea of this invention. For example, in this experimental example, a joint treatment agent mainly composed of a PAE emulsion was used. However, the present invention is not limited to this, and the present invention can also be applied when other joint treatment agents are used. it can.

10 PVC pipe 11 Cue stick S Concrete surface

Claims (2)

N-type penetration that measures the penetration length from the concrete surface of the thrusting rod when the thrusting rod used in JIS A1101 (concrete slump test method) is dropped freely at a falling distance of 750 mm. Conducted the test,
A method for managing a concrete joint treatment agent spraying time, comprising spraying a joint treatment agent on the concrete surface when an amount of penetration obtained by the N-type penetration test is in a range of 20 to 40 mm.   The method for managing a concrete joint treatment agent spraying time according to claim 1, wherein the joint treatment agent is a medicine mainly composed of a resin emulsion.