JP2019006665A - PC grout - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a PC grout in which pre-flow and volume reduction hardly occur and which has excellent pumpability. SOLUTION: PC grout includes a hydraulic composition containing Portland cement, a polycarboxylic acid-based superplasticizer, a cellulosic thickener, and silica fume, and water. PC grout is 0.06 parts by mass to 0.15 parts by mass of a polycarboxylic acid-based fluidizing agent, 0.30 parts by mass to 0.50 parts by mass of a cellulosic thickening agent, and 100 parts by mass of Portland cement. Includes 3.0 parts by mass to 4.0 parts by mass of silica fume. The PC grout according to the present invention contains 30 to 44 parts by mass of water with respect to 100 parts by mass of the hydraulic composition. [Selection diagram] None

Description

  The present invention relates to PC grout.

  PC grout is, for example, grout filled in a duct in order to protect the PC steel placed in the duct of post tension type PC (prestressed concrete) from corrosion or to integrate concrete and PC steel. (For example, refer to Patent Document 1). PC grout is pumped into the duct and filled. For this reason, PC grout is required to have fluidity that can be pumped.

JP 2001-311311 A

  The duct filled with the PC grout of the post tension type PC may have a downwardly inclined portion. When the inclined portion is filled with PC grout, a so-called “pre-flow” may occur in which the lower portion of the PC grout in the vertical direction flows before the upper portion. If a pre-flow of PC grout occurs, air may remain in the duct.

  Further, when the PC grout filled in the duct is hardened, if the volume is reduced, an unfilled portion is generated in the duct, and air may remain in the duct.

  Thus, when residual air arises in a duct, the part which is not suitably coat | covered with the hardened | cured material of PC grout may arise in PC steel materials. In that case, a sufficient passive film is not formed on the surface of the PC steel material, and rust is generated on the PC steel material, which may reduce the durability of the PC steel material. However, if the flowability of PC grout is lowered to suppress the occurrence of pre-flow and bleeding, the pressure required for pumping the PC grout becomes too high and it becomes difficult to fill the PC grout appropriately. There is. Accordingly, there is a need for a PC grout that is unlikely to cause forward flow or volume reduction and that has excellent pumpability.

  A main object of the present invention is to provide a PC grout which is less likely to cause a pre-flow or volume reduction and has excellent pumpability.

  As a result of intensive studies, the present inventors have determined that the polycarboxylic acid-based fluidizing agent is 0.06 to 0.15 parts by mass and the cellulose-based thickener is 0.30 parts by mass with respect to 100 parts by mass of Portland cement. The PC grout containing 0.50 parts by mass and silica fume of 3.0 parts by mass to 4.0 parts by mass and containing 30 to 44 parts by mass of water with respect to 100 parts by mass of the hydraulic composition The present inventors have found that volume reduction is difficult to occur and is excellent in pumpability, and have achieved the present invention.

  That is, the PC grout according to the present invention is a PC grout containing a hydraulic composition containing Portland cement, a polycarboxylic acid-based fluidizing agent, a cellulose-based thickener and silica fume, and water. The PC grout according to the present invention is based on 100 parts by mass of Portland cement. Part by mass, and from 3.0 parts by mass to 4.0 parts by mass of silica fume. The PC grout according to the present invention contains 30 to 44 parts by mass of water with respect to 100 parts by mass of the hydraulic composition.

The PC grout according to the present invention preferably has a BET specific surface area of silica fume is ^{15m 2} / ^g~25m 2 / g.

In the PC grout according to the present invention, the viscosity at a shear rate of 0.1 s ⁻¹ of a 1% by mass aqueous solution of a cellulose-based thickener at 20 ° C. is preferably 1 Pa · s to 20 Pa · s. The viscosity at a shear rate of 30 s ⁻¹ of a 1% by weight aqueous solution of the cellulose-based thickener at 20 ° C. is preferably 0.001 Pa · s to 0.015 Pa · s.

  It is preferable that the PC grout according to the present invention further includes at least one selected from the group consisting of an inorganic expansion material, an antifoaming agent, a shrinkage reducing agent, and a setting modifier.

  According to the present invention, it is possible to provide a PC grout that is unlikely to cause pre-flow and volume reduction and that has excellent pumpability.

  The PC grout according to the present invention can be suitably used for, for example, production of a post tension type PC (prestressed concrete).

  The PC grout according to the present invention includes a cement composition for PC grout including a hydraulic composition and water. Specifically, the PC grout according to the present invention is a kneaded product of a cement composition for PC grout containing a hydraulic composition and water.

  The PC grout according to the present invention comprises a hydraulic composition containing Portland cement, a polycarboxylic acid-based fluidizing agent, a cellulosic thickener and silica fume, and water. Including 0.06 parts by weight to 0.15 parts by weight of an acid fluidizer, 0.30 parts by weight to 0.50 parts by weight of a cellulose thickener, and 3.0 parts by weight to 4.0 parts by weight of silica fume, 30-44 mass parts of water is included with respect to 100 mass parts of hydraulic compositions. For this reason, the PC grout according to the present invention is less prone to pre-flow and volume reduction, and has excellent pumpability.

(Cement composition for PC grout)
The cement composition for PC grout includes a hydraulic composition.

(Hydraulic composition)
In the present invention, the hydraulic composition includes Portland cement, a polycarboxylic acid-based fluidizing agent, a cellulose-based thickener, and silica fume.

(Portland cement)
Examples of Portland cement preferably used include ordinary Portland cement, early-strength Portland cement, ultra-early strong Portland cement, moderately hot Portland cement, low heat Portland cement, and sulfate-resistant Portland cement. Only one of these Portland cements may be used, or a plurality of types may be mixed and used.

  Among the above-mentioned Portland cements, from the viewpoint of improving the curing properties of PC grout prepared using the cement composition for PC grout according to the present invention, from ordinary Portland cement, early strong Portland cement, and very early strong Portland cement. It is more preferable to use at least one Portland cement selected from the group consisting of:

(Polycarboxylic acid type fluidizer)
Examples of the polycarboxylic acid fluidizer include polycarboxylic acid fluidizers, polyether / polycarboxylic acid fluidizers, and modified polycarboxylic acid fluidizers. Only one of these polycarboxylic acid-based fluidizing agents may be used, or a plurality of types may be mixed and used. Among these polycarboxylic acid-based fluidizing agents, polyether / polycarboxylic acid-based fluidizing agents are more preferably used from the viewpoint of realizing a superior upstream flow and a superior pumpability.

  The content of the polycarboxylic acid-based fluidizing agent is 0.06 parts by mass to 0.15 parts by mass, preferably 0.07 parts by mass to 0.14 parts by mass with respect to 100 parts by mass of Portland cement. More preferably, it is 0.075 mass part-0.135 mass part. By setting the content of the polycarboxylic acid-based fluidizing agent in the above range, better pumpability can be realized.

(Cellulose thickener)
The PC grout according to the present invention contains a cellulose thickener as an organic thickener. As the organic thickener, only the cellulose thickener may be used, or in addition to the cellulose thickener, a kind of organic thickener other than the cellulose thickener may be used in combination. In that case, the cellulose-based thickener is preferably used in an amount of 50 parts by mass or more and more preferably 70 parts by mass or more with respect to 100 parts by mass of the organic thickener. Specific examples of organic thickeners other than cellulose thickeners that are preferably used include starch thickeners, guar gum thickeners, vinyl thickeners, and the like.

  As the cellulose thickener, for example, a cellulose thickener containing at least one of hydroxymethylcellulose, hydroxyethylmethylcellulose, hydroxypropylmethylcellulose and the like as a main component can be suitably used. The cellulose-based thickener may contain only one type of the cellulose as a main component, or may contain a plurality of types as a main component.

  In the present invention, “containing as a main component” means containing 50% by mass or more.

  The content of the cellulose-based thickener is 0.30 parts by mass to 0.50 parts by mass, preferably 0.32 parts by mass to 0.48 parts by mass with respect to 100 parts by mass of Portland cement. More preferably, it is 0.34 mass part-0.46 mass part, More preferably, it is 0.36 mass part-0.44 mass part. By setting the content of the cellulosic thickener within the above range, it is possible to further suppress the pre-flow when filling the PC grout.

The viscosity of a 1% by weight aqueous solution of a cellulose-based thickener at 20 ° C. and a shear rate of 0.1 s ⁻¹ is preferably 1 Pa · s to 20 Pa · s, and more preferably 5 Pa · s to 15 Pa · s. Preferably, it is 7 Pa · s to 13 Pa · s, more preferably 8 Pa · s to 12 Pa · s.

By setting the viscosity at 20 ° C. and a shear rate of 0.1 s ⁻¹ of a 1% by mass aqueous solution of a cellulose-based thickener to the above range, it is possible to further suppress the pre-flow at the time of PC grout filling.

The viscosity of a 1% by weight aqueous solution of a cellulose-based thickener at 20 ° C. and a shear rate of 30 s ⁻¹ is preferably 0.001 Pa · s to 0.015 Pa · s, and 0.002 Pa · s to 0.013 Pa · s. s is more preferable, 0.003 Pa · s to 0.01 Pa · s is further preferable, and 0.004 Pa · s to 0.009 Pa · s is still more preferable.

By setting the viscosity at 20 ° C. and a shear rate of 30 s ⁻¹ of a 1% by mass aqueous solution of a cellulose-based thickener to the above range, the pumpability of PC grout can be further improved. Moreover, the volume reduction rate at the time of PC grout hardening can be made lower.

  The “pump pumpability” is a pressure required when the PC grout is pumped into the duct. The lower the pressure, the better the pump pumpability.

(Silica fume)
The PC grout according to the present invention contains silica fume as an inorganic thickener. As the inorganic thickener, only silica fume may be used, or in addition to silica fume, an inorganic thickener other than silica fume may be used in combination. In that case, the silica fume is preferably used in an amount of 50 parts by mass or more, more preferably 70 parts by mass or more with respect to 100 parts by mass of the inorganic thickener. Specific examples of inorganic thickeners other than silica fume that are preferably used include bentonite, kaolinite, and talc.

  The main component of silica fume is silica. As the silica fume, silica fume having a small aluminum content is preferably used. This is because aluminum reacts with water and generates hydrogen having a large expansion action, which may lead to a decrease in strength of the PC grout cured product.

  The content of silica fume is 3.0 parts by mass to 4.0 parts by mass, preferably 3.1 parts by mass to 3.9 parts by mass, more preferably 100 parts by mass of Portland cement. It is 3.2 mass parts-3.8 mass parts, More preferably, it is 3.3 mass parts-3.7 mass parts. By setting the content of silica fume within the above range, it is possible to more effectively suppress the upstream flow at the time of PC grout filling.

BET specific surface area of silica fume is a preferably ^{15m 2} / ^g~25m 2 / g, more preferably ^{16m 2} / ^g~24m 2 / g, more preferably ^{17m 2} / ^g~23m 2 / g . By setting the BET specific surface area of the silica fume within the above range, it is possible to more effectively suppress the upstream flow when filling the PC grout. Further, the pumpability of the PC grout can be further improved.

(Other ingredients)
The PC grout according to the present invention may further contain components other than Portland cement, a polycarboxylic acid-based fluidizing agent, a cellulose-based thickener, and silica fume as long as the effects of the present invention are not impaired.

(Inorganic expansion agent, antifoaming agent, shrinkage reducing agent, setting modifier)
The PC grout according to the present invention may further contain at least one selected from the group consisting of an inorganic expansion material, an antifoaming agent, a shrinkage reducing agent, and a setting modifier as long as the effects of the present invention are not impaired. preferable. The total amount of at least one selected from the group consisting of an inorganic expansion agent, an antifoaming agent, a shrinkage reducing agent and a setting modifier is preferably 0.1 to 8.5 parts by mass with respect to 100 parts by mass of Portland cement. Parts, more preferably 0.15 parts by mass to 7.85 parts by mass, and still more preferably 0.2 parts by mass to 7.2 parts by mass.

(Inorganic expansion material)
By using the inorganic expansion material, a PC grout cured body having high compressive strength can be realized.

  Examples of the inorganic expansion material preferably used include quick lime-gypsum expansion material, gypsum expansion material, calcium sulfoaluminate expansion material and the like. Only one of these may be used, or a plurality of types may be mixed and used. The content of the inorganic expansion material is preferably 3 parts by mass to 7 parts by mass, more preferably 3.5 parts by mass to 6.5 parts by mass, and still more preferably 100 parts by mass of Portland cement. 4 parts by mass to 6 parts by mass. By setting the content of the inorganic expansion material in the above range, a PC grout cured body having higher compressive strength can be obtained. From the viewpoint of realizing higher compressive strength, it is more preferable to use quick lime-gypsum-based expansion material among the inorganic expansion materials.

(Defoamer)
By using an antifoaming agent, a PC grout cured body having higher compressive strength can be realized.

  Examples of the antifoaming agent preferably used include synthetic oils such as mineral oils, silicones, alcohols, and polyethers, or plant-derived natural substances. Only one of these may be used, or a plurality of types may be mixed and used. The content of the antifoaming agent is preferably 0.2 parts by mass to 0.5 parts by mass, more preferably 0.25 parts by mass to 0.45 parts by mass with respect to 100 parts by mass of Portland cement. More preferably, it is 0.3 mass part-0.4 mass part. By setting the content of the antifoaming agent in the above range, a PC grout having higher compressive strength can be realized. From the viewpoint of realizing excellent dispersibility and excellent sustaining effect, a polyether-based or mineral oil-based antifoaming agent is more preferably used.

(Shrinkage reducing agent)
By using the shrinkage reducing agent, a PC grout that hardly causes cracks in the cured body can be realized.

  Examples of the shrinkage reducing agent that is preferably used include lower / higher alcohol alkylene oxide adducts and glycol ether derivatives. Only one of these may be used, or a plurality of types may be mixed and used. The content of the shrinkage reducing agent is preferably 0.1 parts by mass to 0.5 parts by mass, more preferably 0.15 parts by mass to 0.45 parts by mass with respect to 100 parts by mass of Portland cement. More preferably, it is 0.2 mass part-0.4 mass part. By setting the content of the antifoaming agent within the above range, it is possible to suppress the occurrence of cracks in the cured body. From the viewpoint of further improving the dimensional stability of the PC grout cured product, a polyether derivative is more preferably used among the shrinkage reducing agents.

(Setting agent)
By using a setting modifier, a PC grout having a moderately long curing time and an appropriate pot life can be realized.

  Specific examples of the setting regulator preferably used include, for example, sodium salts, specifically, inorganic sodium salts such as sodium sulfate and sodium bicarbonate, sodium tartrate, sodium malate, sodium citrate and sodium gluconate. Organic sodium salts of Only one of these may be used, or a plurality of types may be mixed and used. The content of the setting modifier is preferably 0.1 parts by mass to 0.5 parts by mass, more preferably 0.1 parts by mass to 0.45 parts by mass with respect to 100 parts by mass of Portland cement. More preferably, it is 0.1 mass part-0.4 mass part. By setting the content of the antifoaming agent in the above range, a PC grout having a moderately long curing time and an appropriate pot life can be realized.

(water)
The PC grout according to the present invention contains 30 to 44 parts by mass of water with respect to 100 parts by mass of the hydraulic composition. That is, the PC grout according to the present invention is a kneaded product of 100 parts by mass of a hydraulic composition and 30 parts by mass to 44 parts by mass of water. From the viewpoint of pre-flow and pumpability, the water content is preferably 32 to 42 parts by mass, more preferably 34 to 40 parts by mass with respect to 100 parts by mass of the hydraulic composition. is there. By setting the content of water in the PC grout within the above range, a PC grout that hardly causes pre-flow and has excellent pumpability can be obtained.

(Future)
The pre-flow of the PC grout according to the present invention is preferably 0.1 cm to 3 cm, more preferably 0.1 cm to 2 cm.

  The pre-flow of PC grout can be measured by performing the following pre-flow property test.

  First, with an acrylic tube having a diameter of 65 mm arranged in the vertical direction, 430 g of PC grout immediately after kneading is filled into the acrylic tube. Next, the acrylic tube was tilted by 15 ° from the horizontal direction so that the lower portion of the acrylic tube filled with PC grout was above the upper portion of the acrylic tube, and the acrylic tube was allowed to stand until the flow of the PC grout stopped. In this state, the distance along the axis of the acrylic tube between the lower end in the vertical direction of the lower end of the PC grout and the upper end is measured, and this distance is taken as the pre-flow of the PC grout.

(Rheological properties)
The rheological properties of the PC grout according to the present invention at a shear stress of 0.1 s ⁻¹ are preferably 30 Pa to 168 Pa, more preferably 32 Pa to 100 Pa, and still more preferably 35 Pa to 80 Pa.

The rheological properties of the PC grout according to the present invention at a shear stress of 30 s ⁻¹ are preferably 70 Pa to 299 Pa, more preferably 100 Pa to 250 Pa.

  By setting the rheological characteristics of the PC grout according to the present invention within the above range, better pumpability can be realized, and forward flow can be more effectively suppressed.

  The rheological properties of PC grout can be measured by performing the following test.

Using an Anton Paar rheometer MCR101, the coaxial double cylindrical jig CC27 / P6 is filled with PC grout immediately after kneading and sheared at a low shear rate of 0.1 s ⁻¹ and a high shear rate of 30 s ^−1. The stress (Pa) is measured and the measured value is set as a rheological property.

(Volume reduction rate during PC grout curing)
In the present invention, the volume shrinkage during PC grout curing after 1.5 hours is preferably 0.20% or less, more preferably 0.17% or less, and 0.15% or less. More preferably.

  In addition, the volumetric shrinkage rate at the time of PC grout hardening can be measured based on JSCE-F535 using a vertical pipe.

  The above tests are performed under conditions of 20 ° C. and humidity 65% RH.

  Hereinafter, the present invention will be described in more detail on the basis of specific examples. However, the present invention is not limited to the following examples, and may be appropriately modified and implemented without departing from the scope of the present invention. Is possible.

(Comparative Example 1)
Raw materials (total amount 16 kg) were mixed for 7 minutes using an Eirich mixer at the blending ratio shown in Table 1 below to prepare a hydraulic composition.

As Portland cement, specifically, early-strength Portland cement (Brain specific surface area of 4440 cm ² / g) was used.

As the organic thickener, cellulose thickener “main component: hydroxypropylmethylcellulose” (viscosity of shear rate 0.1 s ⁻¹ 9.76 Pa · s, shear rate 30 s ⁻¹ viscosity 0.00678 Pa · s) Was used.

Silica fume (BET specific surface area 20.0 m ² / g) was used as the inorganic thickener.

  As the fluidizing agent, a polyether / polycarboxylic acid based fluidizing agent was used.

  Next, 6.4 kg of water (tap water) is added to 16 kg of the prepared PC grout cement composition, and the mixture is kneaded for 2 minutes using a chemistor in a constant temperature and humidity chamber maintained at 20 ° C. and a humidity of 65% RH. PC grout was obtained.

(Comparative Example 2)
A PC grout was prepared in the same manner as in Comparative Example 1, except that the mixing ratio of the hydraulic composition was as shown in Table 1 and 5.76 kg of water was added.

(Examples 1 and 2)
A PC grout was prepared in the same manner as in Comparative Example 2 except that the mixing ratio of the hydraulic composition was changed to the ratio shown in Table 1.

(Example 3)
PC grout was prepared in the same manner as in Comparative Example 2 except that the mixing ratio of the hydraulic composition was as shown in Table 1, and sodium tartrate and sodium bicarbonate were used in a ratio of 1: 1 as the setting modifier. .

(Evaluation)
With respect to the PC grout produced in each of Examples 1 to 3 and Comparative Examples 1 and 2, rheological properties and volume change rate were evaluated by the above evaluation methods. The results are shown in Table 1.

In addition, regarding the pumpability, the material having a shear stress of 30 s- ¹ o'clock within 300 Pa was judged as ◯, and the material exceeding 300 Pa was judged as x.

  When the volume change rate calculated by the above method was 0.20% or less after 1.5 hours, it was judged as ◯, and when it was larger than 0.20%, it was judged as x.

Claims (4)

A PC grout comprising a hydraulic composition containing Portland cement, a polycarboxylic acid-based fluidizing agent, a cellulosic thickener and silica fume, and water,
0.06 to 0.15 parts by mass of a polycarboxylic acid-based fluidizing agent, 0.30 to 0.50 parts by mass of a cellulose-based thickener, and silica fume 3.0 with respect to 100 parts by mass of Portland cement. Including parts by mass to 4.0 parts by mass,
PC grout which contains 30-44 mass parts of water with respect to 100 mass parts of hydraulic compositions. BET specific surface area of silica fume is ^{15m 2 / g~25m 2 / g,} PC grout of claim 1. The viscosity at a shear rate of 0.1 s ⁻¹ of a 1% by weight aqueous solution of a cellulose-based thickener at 20 ° C. is 1 Pa · s to 20 Pa · s,
The PC grout according to claim 1 or 2, wherein the viscosity at a shear rate of 30 s ^-1 of a 1 mass% aqueous solution of a cellulose-based thickener at 20 ° C is 0.001 Pa · s to 0.015 Pa · s.   The PC grout according to any one of claims 1 to 3, further comprising at least one selected from the group consisting of an inorganic expansion material, an antifoaming agent, a shrinkage reducing agent, and a setting modifier.