KR20030004461A - Super retarding agent for concrete and control of hydration heat of mass concrete using super retarding agent - Google Patents

Abstract

PURPOSE: A super set retardant comprising sugar solution, thickener and air entraining agent is provided to delay setting and hardening time of concrete or cement mortar, enabling transportation and storage for a long time. Also, the retardant controls heat of hydration in casting, resulting in reduction of cracking. CONSTITUTION: The super set retardant is obtained by mixing sugar solution, thickener solution and air entraining(AE) agent in a weight ratio of 1 : 0.1-1.5 : 0.001-0.01, wherein the sugar solution is prepared by dissolving sugar and water in a weight ratio of 1 : 1 and the thickener solution is prepared by diluting thickener powder, polyethylene oxide(PEO), into water. Also, the heat of hydration of mass concrete is controlled by the following steps of: dividing a section of mass concrete uniformly; adding a large quantity of super set retardant to the lower part of concrete and a small quantity of super set retardant to the upper part of concrete, wherein the amount of retardant is in the range of 0.01-0.2%; casting conventional concrete on the upper part.

Description

Super retarding agent for concrete and control of hydration heat of mass concrete using super retarding agent

The present invention relates to a super-delay agent for concrete and a method for adjusting the heat of hydration of mass concrete using the super-delay agent, in particular, by adding a thickening agent (PEO) and an air entraining agent (AE) at a predetermined ratio to a sugar solution of a certain concentration, When applied to cement mortar, to produce a super-delay agent to significantly delay the condensation and curing time to extend its usable time, and to adjust the heat of hydration of the mass concrete using the prepared super-delay agent and to reduce the temperature cracks and It relates to a method for regulating mass concrete hydration heat using this super delay agent.

In general, when concrete is installed in special conditions or in a limited environment, it is difficult to find an effective method, resulting in deterioration of quality and economic loss. In other words, it is difficult to transport long-distance concrete that is not solid under special conditions such as book wallpaper or mountainous backcountry. In addition, when the concrete is divided into two or more layers, it is difficult to integrate the structure, resulting in poor construction, such as joint phenomenon, and when mass-concrete with large members is not properly coped with constrained stress cracking caused by the heat of hydration. Failure to do so may cause deterioration of concrete.

In the case of foreign countries, as a way to solve this type of problem, various super-delays with excellent condensation delay performance have been developed and put into practical use to improve the construction method and the quality of concrete. I'm not doing it.

The present invention has been invented in view of the above circumstances, and when applied to concrete or mortar, it does not separate materials such as bleeding, exhibits a target air amount, and condenses concrete or mortar without adversely affecting the strength expression after curing. And the purpose is to produce a super delay agent that gives a variety of applicability or concrete quality improvement by greatly delaying the curing time.

Still another object of the present invention is to provide a method for adjusting the mass concrete hydration heat to reduce the temperature cracking caused by the heat of hydration by controlling the heat of hydration during the mass concrete construction using the manufactured super delay agent.

1 is a graph showing the characteristics according to the mixing ratio of the various additives used in the manufacturing method of the super-retardant for concrete according to the present invention.

Figure 2 is a graph showing the slump and the air amount according to the W / C according to the mixing rate change of the super-retardant for concrete according to the present invention.

Figure 3 is a graph showing the amount of bleeding according to the change in the mixing rate of the ultra-delay retardant according to the present invention divided by W / C.

Figure 4 is a graph showing the setting time according to the mixing rate change of the super-retardant for concrete according to the present invention.

Figure 5 is a graph showing the temperature history of the center of the test specimen according to the change of the mixing rate of the ultra-delay agent according to the present invention divided by W / C.

Figure 6 is a graph showing the compressive strength according to the age of the super-retardant incorporation according to the present invention.

Figure 7 is a graph showing the compressive strength according to the age after the termination of the super-retardant incorporation according to the invention.

8 is a graph showing the rate of change in the length of drying by shrinkage of concrete according to the mixing rate of the super-delay agent according to the present invention

Figure 9 is a graph showing the relative dynamic modulus of elasticity according to the number of cycles of freezing and thawing action of the concrete according to the mixing rate of the super-delay agent according to the present invention.

10 is a view showing a thermocouple embedding position for measuring the size of the mass concrete mock member and the heat of hydration therein, and also the core collecting position.

11 is a graph showing the temperature history according to the age of the simulation member integrally cast the plain concrete.

12 is a graph showing the temperature history according to the age of the simulation member when the two times the plain concrete is poured.

13 is a graph showing the temperature history according to the age of the mock member in which the concrete is poured at the top, the concrete mixed with 0.2% super-retardant at the bottom.

14 is a graph showing the upper and lower compressive strength for each core position according to the method of placing the simulation member.

In order to achieve the above object, the ultra-delay agent according to the present invention,

Powdered sugar is used after dissolving water at room temperature in a 1: 1 by weight ratio, and dissolving it, wherein powdered sugar: dilute solution of powdered thickener: AE agent is 1: 0.1 to 1.5: 0.001 to 0.01 by weight ratio. It is prepared by mixing.

Preferably, the super delayed agent is prepared by mixing powdered sugar: a solution in which the powdered thickener is diluted: AE agent in a weight ratio of 1: 1: 0.005.

In addition, the method of adjusting the heat of hydration of mass concrete according to the present invention

In the case of mass concrete pouring, the mass cross section is divided equally, and the super-delay agent prepared according to the above method is gradually reduced and added in the mixing ratio of 0.01 to 0.2%, and the uppermost layer is poured with ordinary concrete to adjust the heat of hydration. ..

In general, the super-delay agent is mainly composed of a compound having a cement delaying effect of the cement and is divided into organic compounds and inorganic compounds as a kind, in general, organic compounds are more delayed and usable than inorganic compounds. In particular, saccharides among organic compounds have excellent effects. The main material of the ultra-delaying agent according to the present invention is a sugar which is a saccharide of the organic compound, which is commonly used in the market.

As mentioned above, according to the present invention, in order to obtain a super delay agent that significantly delays the condensation and curing time of concrete, which has not been studied in Korea yet, relatively thick sugars and thickeners and AE agents are mixed with a certain ratio of grass paper. Prepare a softener.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

In the present invention, in the production of concrete, a mixture of sugar solution is mixed together to produce a concrete having a delay performance. Among the problems occurring in this process, a thickener (PEO) is added to control the increase in the amount of bleeding. In order to recover, the AE agent is added to ultimately solve the problem while developing a super delay agent with improved performance.

The powdered sugar and water at room temperature are mixed at a weight ratio of 1: 1, and the sugar is completely dissolved in water, followed by titration of a certain amount of thickener solution in which the powdered thickener (PEO) is diluted with water at room temperature and a certain amount of AE agent. It is added by the ratio and then mixed for a certain time.

The mixing ratio of powdered sugar: thickener solution: AE agent is mixed at a weight ratio of 1: 0.1 to 1.5: 0.001 to 0.01, but preferably 1: 1: 0.005.

As shown in FIG. 1, the bleeding amount of concrete mixed with a sugar solution is increased by about 60% or more as compared to the concrete, but the amount of bleeding is controlled when 0.2% of thickener (PEO) is added to cement. In addition, the amount of air decreases by 1 to 2%, but when the AE agent is added at a ratio of 0.001% to the cement, the air amount is being recovered, and the sugar: thickener: AE agent is 1: 1: 0.005. When mixing, it is possible to produce a super delay agent that can ensure the required quality.

In addition, by controlling the heat of hydration using the super-delay agent prepared above, it is possible to reduce the temperature cracking due to the heat of hydration during mass concrete construction. Generally, the heat of hydration of ordinary concrete starts to cool down slowly after reaching the maximum temperature within 1 ~ 2 days after pouring and becomes the same as the outside temperature after 5 ~ 6 days. However, when 0.2% of super-retardant is added, the heat of hydration of concrete gradually decreases after reaching the maximum temperature after 6-7 days and becomes the same as the outside temperature after 10-11 days. Therefore, when mass concrete construction of a certain section is divided into several parts of 1/2 ~ 1/5, add a lot of super-retardant to the lower part, reduce the amount of addition to the upper part, and add concrete to the upper part, and at the same time, normal concrete Solving the problem of sticking, watertightness, and durability, which are the problems in case of separate casting to reduce the heat of hydration, by adjusting the heat of hydration, and adjusting the heat of hydration of mass concrete that can reduce the temperature crack caused by the heat of hydration Provide a method.

Figure 2 shows the slump and the amount of air according to the change of the mixing rate of the developed super delay agent divided by W / C. As shown in FIG. 2, the W / C 40% and 50% showed little change even if the mixing ratio of the developed super delay agent increased. This is believed to be due to the thickeners and AEs added in the ultra delay agent. However, in the case of W / C 30%, it appears to be greatly reduced, and in the case of high-strength concrete, a new compounding ratio is required to reduce the thickener and increase the AE agent. Figure 3 shows the bleeding amount according to the change in the mixing rate of the developed super-delay agent by W / C, the amount of bleeding occurred in all formulations similar to the concrete even when the mixing rate increases. This is due to the increase in viscosity due to the thickener component added to the developed super delay agent.

Figure 4 shows the setting time according to the mixing rate of the developed super delay agent. In the case of concrete, the termination takes about 10 to 12 hours, whereas the termination time is measured between 3 to 4 days at 0.1% of super-delay retardant content and 5 to 6.5 days at 0.2%. appear. The practical applicability of the ultra-delay agent developed in the future is estimated to be used within the mixing ratio of 0.2%.

Figure 5 shows the temperature history of the center of the test specimen according to the change in the mixing rate of the developed super-delay agent divided by W / C. As the mixing rate of ultra-delay was increased, the maximum rise temperature decreased and the time to reach the maximum rise was significantly delayed. First, in the case of 30% of W / C, the maximum temperature at 0.1 and 0.2% was increased as the mixing rate of super-delay was increased. Was reduced by about 10 ℃ and 20 ℃ compared with normal concrete, and the maximum temperature arrival time was delayed by 4 days and 11 days. In the case of 40% and 50% of W / C, the temperature of 5 ° C and 15 ° C was decreased at 0.1% and 0.2% of the super-delay-retardant content, and the maximum temperature reaching time was delayed by 2-3 days and 7-8 days. This temperature drop phenomenon is analyzed as a result of the hydration reaction and heat dissipation effect in a wide time zone as the hydration latency is prolonged by increasing the mixing rate of the ultra delay agent.

Figure 6 shows the compressive strength according to the age of age, Figure 7 shows the compressive strength according to the age after termination. Compared with normal concrete, compressive strength was shown to be lower at early age when super-retardant was mixed. However, as the age passed, the compressive strength increased rapidly. At later ages, the compressive strength was about 10% higher than that of concrete. It is analyzed that this is due to the hydration reaction proceeding gradually due to the initial hydration delay, and the dense hydration product is generated and the internal structure becomes more compact. 8 shows the length change rate by dry shrinkage according to the mixing rate of the ultra-delay agent. Underwater curing during the first seven days showed a slight expansion, and then during the curing period, there was a contraction, with a similar rate of change in length compared to normal concrete.

Figure 9 shows the relative dynamic modulus of elasticity according to the number of freezing thaw cycles by the mixing rate of the super delay agent. In all formulations, the relative dynamic modulus after 300 cycles of freeze-thawing was more than 90%, which showed good freeze resistance, and showed a slight difference of less than 5% compared to that of concrete.

10 shows the thermocouple embedding position for measuring the size of the mass concrete simulation member and the heat of hydration therein, and also the core collecting position.

Figure 11 shows the temperature history according to the age of the simulation member integrally cast the plain concrete. First, the maximum temperature of the heat of hydration reached 1 day (24 hours) after concrete pouring, and then gradually decreased to match the room temperature after 3.5 days. In addition, since the width of the rising and falling curve is narrow and the slope is steep in the temperature history, it is analyzed that the temperature cracking probability due to the initial restraint stress and the temperature cracking occurrence due to the late restraint stress are very high.

Figure 12 shows the temperature history according to the age of the mock member in the case of two separate pouring concrete concrete. Twice separate casting of plain concrete (more than two times possible) is currently used in some concrete concrete construction and it has been shown to reduce the heat of hydration by about 9 ℃ compared to all the placing, but the slope of internal and external temperature difference and temperature history curve Was great, and the heat of hydration of the concrete poured in the second time was also similar to that of the one time.

FIG. 13 shows the temperature history according to the age of the simulation member in which the upper plain concrete and the lower super-retardant 0.2% mixed concrete are poured at the same time. Although the slope of the temperature curve due to the heat of hydration of the early plain concrete was abrupt, the peak temperature was lowered by more than 20 ℃ and the temperature difference between the center and the outer surface was about 10 ℃ lower than that of the general concrete integral casting. In addition, the hydration curve of concrete mixed with super-retardant shows a gentle slope and distributed over a long time, it can be analyzed that it can reduce the crack caused by the restraint stress.

Figure 14 shows the upper and lower compressive strength for each core position according to the method of placing the simulation member. First, the compressive strength for each core position showed that the central part (①) was somewhat smaller than the outermost part (④), which was analyzed to be degraded by the influence of hydration reaction and internal stress due to high heat of hydration. In addition, the upper and lower core compressive strengths according to the casting method were found to be no significant difference between the upper and lower parts in the case of ordinary concrete integral casting, whereas the upper and lower cores showed a similar strength in the lower part than the upper part in the case of the ordinary concrete separate casting. Since the core compressive strength is 28 days after the end of the upper part, the lower part is already after 28 days. In the case of the lower super-delay concrete (0.2%) and the upper common concrete, the core compressive strength was found to be mixed with the super-delay agent in the lower part than the upper part, which is more closed inside as the concrete containing the super-delay agent is delayed. This may be due to the formation of a hydration product and the dense internal tissue.

In conclusion, in the case of using the developed super delay agent, the slump, air amount and bleeding amount were increased by the thickener and AE agent mixed with the developed super delay agent at the proper ratio. It appeared small, and the amount of bleeding occurred at about the same level as the plane.

The coagulation delay performance showed good coagulation delay performance by delaying the coagulation of concrete for about 6 days within 0.2% of the mixing rate of the developed super delay agent, and the temperature history characteristic by the heat of cement hydration was the highest as the mixing rate of the super delay agent was increased. The rise in temperature has decreased, the duration of hydration heat is widened, and the time to reach the maximum rise temperature tends to be significantly delayed. Therefore, if a casting method using super-delay agents developed during the construction of mass concrete is planned, it will have a great effect on reducing the heat of hydration. It is expected to be.

The compressive strength of hardened concrete was equal to or higher than the plain in all blends when it was mixed, and the developed supertardant did not have a significant effect on the strength. Also, the length change rate and freeze thaw resistance caused by dry shrinkage The durability of is similar to that of concrete, and the effect of the developed super-delay agent on the durability of concrete is found to be little.

The core compressive strength of the mock member was generally smaller than the outermost part, which was analyzed to be lowered due to the heat of hydration of the core. In particular, the core of the mock member cast the upper super-delay concrete (0.2%) Compressive strength was found to be greater in the case of the super delay agent incorporating the lower part than the upper part, which may be due to the formation of more tightly hydrated interior of the concrete as the condensation delayed.

The temperature history showed that the highest temperature in the center of the plain concrete was the highest and the difference with the outer surface was large, and the separation of the plain concrete reduced the maximum temperature in the center slightly. In addition, in the case of integral casting in which concrete containing super-retardant is poured at the bottom of the concrete, the heat of hydration can be greatly reduced, which is very advantageous. The temperature cracking index showed the temperature cracking probability of about 1/4 of general concrete integral casting and 1/2 of general concrete separating casting when concrete mixed with super-retardant was used together with general concrete.

As mentioned above, when the super-delay agent developed by the present invention is used in concrete having a coagulation delay performance, the coagulation delay performance of the concrete is several times to several tens of times larger than that of the conventionally developed retardant. It is expected to be possible to use.

In addition, the developed super delay agent solved the problem of the increase of the bleeding amount and the decrease of the air volume, which was raised due to the problem of use by adding the thickener and the AE agent in a certain ratio to the sugar solution. A great effect can be obtained in improving quality and workability.

In addition, when used to adjust the heat of hydration during the mass concrete construction, it is possible to solve various problems such as adhesion, watertightness, deterioration of durability and construction cost, which are problems such as separation and pipe cooling, which have been conventionally performed for reducing hydration heat.

Although described above with reference to a preferred embodiment of the present invention, those skilled in the art will be variously modified and changed within the scope of the invention without departing from the spirit and scope of the invention described in the claims below I can understand that you can.

Claims (2)

Powdered sugar and water at room temperature are mixed and dissolved in a weight ratio of 1: 1. Powdered sugar: A solution in which a powdered thickener is diluted: AE is mixed in a weight ratio of 1: 0.1 to 1.5: 0.001 to 0.01. Super Delay Retardant In the case of mass concrete pouring, the mass section is divided equally, and the super-delay agent prepared according to the above method is gradually reduced in the mixing ratio of 0.01 to 0.2%, and the uppermost layer is poured with ordinary concrete to adjust the heat of hydration. How to adjust the heat of hydration of mass concrete.