JP2007091510A - Acid-resisting concrete - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide acid-resisting concrete capable of preventing the deterioration even under an acidic atmosphere without needing excess additive water. <P>SOLUTION: A binder comprising cement and granulated blast furnace slag is prepared so that the quantity of the granulated blast furnace slag is 40-70% of the binder by weight and the acid-resisting concrete is made by kneading a mixture of the binder, coarse aggregate and fine aggregate with water into which a water reducing agent in the quantity 0.5-2.5% of the weight of the binder and a highly polymerized melamine-formalin condensate having polymerization degree of 50,000-120,000 in the quantity 0.70-2.0% of the weight of the binder are added. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an on-site concrete structure that constructs sewers and drainage channels that are easily affected by the environment, a concrete product such as a box culvert and a fume pipe, and an acid resistance used for a concrete structure that is constructed in an underground part. This is related to concrete.

  Conventionally, as concrete used for concrete products such as box culverts and fume pipes that are placed on site to construct underdrains, usually portland cement is used as a binder, sandstone, limestone The composition is generally composed of crushed stone and sand. In such concrete, a water-reducing agent such as naphthalene sulfonate-based polyol, or a lime-based or ettringite-based swelling agent is used as an admixture.

For example, when a sewer is constructed using concrete products such as box culverts made of concrete, sulfuric acid such as sulfurous acid gas is generated by the action of organic matter and bacteria in the sewage depending on the sewage flowing inside. Then, the sewage becomes acidic water and may react with calcium silicate (mCaO, nSiO ₂ ) which is the main component of Portland cement. As a result, the calcium content in Portland cement reacts with sulfate ions, and gypsum (CaSO ₂ ) is produced in the concrete and expands or dissolves, resulting in deterioration of the concrete and durability of the concrete product. Would cause problems.

  In view of such problems, in recent years, a method such as laminating the inner surface of a structure directly in contact with such sewage with a polymer sheet so that the acidified sewage does not soak into the concrete product, In the case of existing structures, measures such as covering with polymer tape are taken.

Further, for example, Patent Document 1 contemplates acid resistant concrete blended so that the concrete itself has resistance to an environment exhibiting such acidity.
JP-A-10-218644

  However, in the case of using the above-described polymer sheet or the like, the manufacturing cost as a whole increases because the work time required for the construction becomes long, and if the polymer sheet has one pinhole, the desired effect can be obtained. There was a problem that I couldn't expect. That is, when a pinhole is formed in the polymer sheet coated with concrete, the above-described sulfuric acid content or the like enters the concrete from the pinhole. As a result, as in the case where the polymer sheet was not coated, the concrete was eroded by the acidified sewage, and the polymer sheet did not function.

  Moreover, in the thing of patent document 1, since it is very viscous concrete, in order to ensure required workability, it is necessary to add addition water to an overt taste, but this excess addition water is after curing. There existed a problem that it remained in the inside of a hardening body and caused the strength fall.

  Therefore, an object of the present invention is to provide acid-resistant concrete that eliminates such problems and does not require excessive added water and can prevent deterioration even in an acidic environment.

  That is, the acid-resistant concrete of the present invention is a binder composed of cement and blast furnace granulated slag, and the blast furnace granulated slag is prepared to 40 to 70 percent of the binder weight. A mixture composed of fine aggregates, a water reducing agent of 0.5 to 2.5 percent of the binder weight, and a highly polymerized melamine formalin condensation having a degree of polymerization of 0.70 to 2.0 percent of the binder weight of 50,000 to 120,000 It is characterized by being kneaded with water added with salt.

  In the present invention, the binder is composed of cement and granulated blast furnace slag. In this case, the amount of granulated blast furnace slag is set to an amount that replaces 0.40 to 0.70 weight percent of the weight when the weight of cement normally used for concrete is 100. Examples of cement include Portland cement and mixed cement. There are various types of Portland cement, but it is not necessary to be special, and Portland cement is usually used. Other Portland cements such as early-strength Portland cement and low heat Portland cement may also be used. Examples of the mixed cement include blast furnace cement and silica cement.

The granulated blast furnace slag preferably has a fineness of 6000 to 8000 cm ² / g in terms of a brane value.

  Examples of the water reducing agent include naphthalene sulfonate, polycarboxylate, and a low-polymerization melamine formalin condensate salt. In order to impart resin properties to the hardened concrete, a melamine formalin condensate salt having a polymerization degree of 2000 to 4000, that is, a formalin condensate of melamine is preferable.

  The coarse aggregate and the fine aggregate are not particularly limited, and those widely used in the field may be used. The coarse aggregate is preferably a rock having a low calcium content compared to others, and specifically, for example, a granite rock is preferred.

  In such a configuration, by replacing a predetermined amount of cement with blast furnace granulated slag that hardly contains calcium, the total calcium content in the binder is more than the binder of only the same amount (same weight) of cement. Is to decrease. For this reason, when used in an environment with strong acidity, it is possible to reduce the generation of gypsum because the calcium content reacting with the sulfuric acid content as described above is small. Also, the use of blast furnace granulated slag is because the hydration reaction of blast furnace granulated slag is slower than cement, resulting in inefficiency in production, but by using fine blast furnace granulated slag as described above, By decreasing the specific surface area and bringing the hydration reaction rate close to that of cement, it is possible to prevent a decrease in production efficiency. Moreover, such blast furnace granulated slag acts to make the concrete surface after hardening dense, and functions to improve acid resistance by reducing the water absorption rate.

  In addition, melamine formalin condensate having a high degree of polymerization, specifically a polymerization degree of 50,000 to 120,000, that is, a highly polymerized melamine formalin condensate salt as an admixture, imparts the properties of melamine resin to concrete with a small amount of addition, and is preferably acid resistant. It contributes to the improvement of the property. In addition, since such a highly polymerized melamine formalin condensate salt has a thickening action, for example, it is easy to drive a concrete product such as a box culvert into a mold and the melamine resin oozes out to the mold surface. It acts to increase the acid resistance, chemical resistance, water absorption resistance, etc. of the concrete after curing.

  In order to further improve the acid resistance, silica fume is used as a part of the fine aggregate, and an amount corresponding to 2.5 to 5.0 weight percent of the binder weight is substituted for the fine aggregate. is there. Silica fume is an ultrafine powder of silica itself and may be of the same type as that blended in silica cement known as acid resistant cement. Silica cement is difficult to obtain because it is a special cement and lacks versatility due to its cost. However, by adding silica fume to the cement, it will give an effect close to the acid resistance of silica cement. Can do. Silica fume also has the effect of increasing the strength because it reduces the crystal voids of the cement, and improves the acid resistance by a combined effect that matches the effect described above.

  The present invention is configured as described above, and can be manufactured in the same way as ordinary concrete without any special work at the time of manufacture, and can be manufactured economically at low cost, and after being cured. It has a water repellency performance and can improve acid resistance.

  Examples of the present invention will be described below.

The first to sixth examples showing specific blends in the concrete blending table-1 are concrete blends having a design strength set to 40 N / mm ² , using ordinary Portland cement as cement, and a fineness of bran A blast furnace granulated slag of 6000 cm ² / g is used. And a binding material is comprised by normal Portland cement and blast furnace granulated slag.

  In the same table, the one with the blending number A-1 is a blend for a comparative example with respect to the acid resistant concrete of the present invention.

  The first example (formulation number A-2) is a composition using a binder prepared by preparing blast furnace granulated slag to 50 weight percent of the weight of the binder, and hereinafter the second example (formulation number). A-3) to the fifth example (composition number A-6) were prepared with 60 weight percent of blast furnace granulated slag, and the sixth example (composition number A-7) was prepared with 70 weight percent of blast furnace granulated slag. It is a binder.

  About the 2nd Example of the mixing | blending number A-3, the high polymerization melamine formalin condensate salt is not mix | blended. In the third example of formulation number A-4, the fourth example of formulation number A-5, and the fifth example of formulation number A-6, the amount of highly polymerized melamine formalin condensate is increased in this order. did. That is, in the third embodiment, 1.0% of the binder weight of the highly polymerized melamine formalin condensate is blended, and similarly, 1.5% in the fourth embodiment and 2.5% in the fifth embodiment. Respectively.

  In the first to sixth examples, the fine aggregate ratio (S / a), which is the absolute volume ratio between the fine aggregate and the total amount of aggregate, was the same. The aggregate is, for example, granite based coarse aggregate, and the fine aggregate may be sand such as standard sand.

  In addition, in the concrete composition table-1, the highly polymerized melamine formalin condensate salt is abbreviated as highly polymerized melamine. As the water reducing agent, a melamine formalin condensate salt having a polymerization degree of 2000 to 4000, which is a melamine water reducing agent, was used.

  With the above blending, the concrete was kneaded and the items listed below were measured in each example. The measurement results are shown in the table “Measurement Value-1”.

(1) Kneading properties, slump value, kneaded unit volume mass, air volume (2) Strength characteristics: Compressive strength [by heat curing with steam] (Age: 2 weeks, 4 weeks)
(3) Acid resistance test: Specimen 4 weeks old is immersed in a 5% sulfuric acid solution, and the change in weight of the specimen is measured after 1 week, 2 weeks and 4 weeks after immersion (Immersion material age: (1 week, 2 weeks, 4 weeks)

  In the comparative example of formulation number A-1, 5% sulfuric acid solution and harsh conditions were used, so that the paste portion on the surface of the test specimen was dissolved in 1 week of the immersion material age, and the surface layer was 2 weeks in the immersion material age. Part of the fine aggregate began to peel off, and the measurement result showed that it fell off about 1% of the total weight.

  A part of Portland cement is replaced with granulated blast furnace slag, that is, the first example to the sixth example of the blending number A-2 to the blending number A-7, the paste portion of the surface layer is slightly in one week of immersion. Although it was dissolved, the weight was slightly increased. This result is presumed that moisture is adsorbed on the gel part because the cured crystal of the granulated blast furnace slag exhibits a gel-like element. This has little effect on the deterioration of the concrete, and the specimens of the first to sixth examples show almost no cracking or peeling of the aggregate, and the acid resistance is effective in comparison with ordinary concrete. Sex was recognized.

  In the sixth example, it is a measurement result that some early decrease in strength is observed, and when the blending amount is higher than the blending amount (substitution rate) of granulated blast furnace slag in this sixth example, the acid resistance is improved. However, considering the delay in the development of strength, it is expected to become inefficient in the production of concrete products.

  As described above, in the first, fourth and sixth examples in which 1.5% of the binder weight of the highly polymerized melamine formalin condensate salt was added, the weight difference between 1 week and 4 weeks was not reduced. It was confirmed that the acid resistance was improved because the amount was increased.

  In addition, in the fifth example, the viscosity of the concrete is high, and it is clear that the slump loss (the slump value after the end of the kneading is small and the property that the fluidity is lost at an early stage) is exhibited, It was confirmed that 2.5% or more of the addition of the highly polymerized melamine formalin condensate salt is not preferable for the production of concrete.

  Next, in place of the low-polymerized melamine formalin condensate salt, which is a melamine water reducing agent, a seventh embodiment (formulation number B-1) in which a naphthalene water reducing agent (a naphthalene sulfonate water reducing agent) was added, melamine water reducing The eighth example (composition number C-2) to the tenth example (composition number C-4) in which the silica fume was added while using the agent will be described. Also in these seventh to tenth embodiments, the design strength is the same as that of the above-described embodiments. Also, the measurement items in the test are the same as in the above-described embodiments. The blends of the seventh to tenth examples are shown in the concrete blending table-2, and the measured values of the test results are shown in the table “measured value-2”.

  The seventh example of formulation number B-1 is the same as the fourth example with respect to the formulation other than the water reducing agent. However, the amount of the naphthalene-based water reducing agent was less than that of the melamine-based water reducing agent, and was about ½.

  About the silica fume, the compounding quantity was increased in order of the 8th Example of the blending number C-2, the 9th Example of the blending number C-3, and the 10th Example of the blending number C-4. That is, in the eighth example, silica fume was blended at 2.0% of the binder weight, 2.5% in the ninth example, and 5.0% in the tenth example.

  In the seventh embodiment, a naphthalene sulfonate-based water reducing agent was used as a water reducing agent. However, even if a water reducing agent different from the melamine water reducing agent is used in this way, various performances of concrete are achieved. It has been confirmed that there is little effect, and that it does not reduce the performance of concrete even when used in combination with highly polymerized melamine formalin condensate salt.

  It was confirmed that the addition of silica fume had a positive effect on the acid resistance. That is, the blending ratio (addition ratio) with respect to the binder is as small as 0.65% in the weight difference between the 2nd and 4th weeks of the dipping material age in the eighth example, and similarly in the ninth example, the weight difference is small. By increasing the blending amount of silica fume, the acid resistance was improved in synergy with the effect exhibited by the highly polymerized melamine formalin condensate salt.

  In contrast, in the tenth example, the effect of adding silica fume was recognized, but the weight difference between the 2nd and 4th week of the soaking material age was 0.43%, which was twice that of the ninth example. Despite the blending ratio, the effect was not much different from that of the ninth example. In the tenth embodiment, the viscosity tends to be rather high, and when a concrete product or the like is manufactured, it is in a kneaded state that is somewhat difficult to put concrete into a mold or the like.

  In addition, the specific configuration of each part is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention.

  Examples of utilization of the present invention include concrete products that constitute drainage channels and sewers, such as sewers and drainage channels that are installed and constructed on site, box culverts, fume pipes, manholes, U-shaped side grooves, and the like. . Moreover, it can be used for a concrete structure constructed in an underground portion of an area where there is a high possibility of coming into contact with gas containing sulfur, cold water, hot water, or the like in an area where the hot spring is located or in the vicinity of the hot spring.

Claims (4)

  A binder comprising cement and granulated blast furnace slag, wherein the granulated blast furnace slag is prepared to 40 to 70 percent of the weight of the binder, and the mixture comprising the binder, coarse aggregate and fine aggregate is combined with the binder. Mix with water containing 0.5-2.5 percent by weight of water reducing agent and highly polymerized melamine formalin condensate salt with a degree of polymerization of 0.70-2.0 percent by weight of the binder. Acid resistant concrete.   The acid resistant concrete according to claim 1, further comprising 2.5 to 5 percent of silica fume by weight of the binder.   The acid resistant concrete according to claim 1 or 2, wherein the water reducing agent is a melamine formalin condensate salt having a polymerization degree of 2000 to 4000.   The acid-resistant concrete according to claim 1, 2 or 3, wherein the cement is Portland cement.