JPS6051263A - Ageing of mortar or concrete - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for curing mortar or concrete. In particular, the present invention relates to a curing method using a curing mat made of a water-absorbing material with high water retention.

[Prior Art] In general, the strength after hardening of mortar or concrete (hereinafter simply referred to as "concrete") using Portland cement (hereinafter referred to as "cement" in RL) is as follows:
It depends on the amount of water used during kneading, and the lower the amount of water, the greater the strength. This is known as the basic principle of Concrete 1. Therefore, it is desirable to mix concrete as hard as possible. The hardening phenomenon of concrete 1 is caused by the formation of hydrates, which are reactants between cement and water, but the theory is that cement is completely hydrated.
The amount of water required for irrigation is approximately 20% of the weight of cement.

However, when g of concrete material '1 is kneaded with 20% of the theoretical amount of water, the kneaded material becomes too hard and becomes lumpy, so this kneaded material is poured into formwork and finished uniformly. It is not possible. Therefore, in actual construction, the amount of water used during cement kneading is usually increased to 40 to 60% by weight of the cement, that is, the water-cement ratio (W/C). However, if Concrete 1 is allowed to harden with a water content of 20% or more, excess water unnecessary for cement hydration will dissipate from the concrete into the atmosphere, and voids will be formed inside the concrete. This will weaken the strength of the For this reason, conventionally, immediately after pouring concrete, excess water unnecessary for water use is extracted from the concrete 1 as much as possible by vacuum concrete method or other methods to increase the strength of the concrete 1.

On the other hand, if the surface of poured concrete 1 is exposed to direct sunlight or wind and the surface moisture or temperature suddenly changes, cracks will inevitably occur on the surface. There is a method of curing the concrete surface immediately after pouring by covering it with wet cloth, wet canvas, wet burlap, or water-absorbed sponge mat, or by covering the concrete surface with a moisture-impermeable sheet 14 or a coating agent. The instructions are to use a sealing regimen to prevent water evaporation. This is based on the principle of Concrete 1 J- that it is better to cure and harden concrete in moist air or water than to leave it in the air and let it harden in a dry state. ing.

Therefore, the method for curing concrete after pouring must fulfill the contradictory functions of removing excess moisture from the surface of the concrete 1 and retaining sufficient moisture on that surface. However, conventional curing methods have the disadvantage that when one function is achieved, the other function is impaired, and as a result, it is difficult to increase the strength of concrete after hardening. Furthermore, even if the surface of the concrete is covered with wet wormholes, the wormholes dry out, making it inconvenient to periodically replenish water during curing.

As a result of extensive research in order to eliminate the above-mentioned drawbacks and troubles, the present inventor has discovered that a water-retaining water-absorbing material is added to the surface of concrete 1. The excess water unnecessary for the hydration of cement from the concrete is adsorbed and removed by the water-absorbing material, thereby lowering the water-cement ratio of the concrete.
After increasing the strength of the concrete after hardening, a water-absorbing material that adsorbs the excess water is left on the surface of the concrete to keep the surface moist and cause cracks and other defects on the surface. He invented a unique curing method and filed a patent application under Japanese Patent Application No. 58-8F3233.゛However, after repeatedly implementing the above method, I found that there are some improvements that need to be made to the above method! IG'fi was found.

Firstly, simply spreading a fabric containing a water-retaining water-absorbing material on the surface of concrete will not cause immediate moisture adsorption; It was necessary to press it lightly against the surface. This pressing operation creates unevenness on the still flexible concrete surface, and if the fabric is left as it is, so-called "unevenness" will be formed on the concrete surface.
There was a problem that a smooth concrete surface could not be obtained.

Second, even if a fabric containing a water-retaining water-absorbing material is spread on the surface of concrete and absorbs moisture over time without pressing, the entire fabric will absorb water due to the fabric's moisture absorption. 11j expanded and the surface of the 11j fabric became uneven, resulting in the formation of "uneven areas" on the concrete surface. Here, "uneven" refers to a state in which the concrete surface is not flat and has irregularities.

Thirdly, a fabric including woven fabric, knitted fabric, or non-woven fabric was used as the curing mat containing water-retaining water-absorbing material.
From the viewpoint of water retention, we needed a material with high sealing properties to replace IIj fabric.

[Objective of the Invention J] The present invention further improves the above-mentioned invention, and provides a method for curing mortar or concrete that smoothes the surface of concrete with a small number of man-hours and increases its strength after hardening. Let be l' target.

[Structure of the Invention] A feature of the present invention is that a nonwoven fabric and a synthetic resin sheet having approximately the same area as the nonwoven fabric are placed on the surface of mortar or concrete that has been cast into a formwork and has just finished leveling the surface. A curing mat with a structure in which a fiber aggregate mixed with a water-retaining water-absorbing material is interposed is spread so that the non-woven fabric side faces the mortar or concrete surface, and the non-woven fabric side is placed on the concrete surface. After the curing mat adsorbs and removes excess water unnecessary for cement irrigation from the monolith or concrete by contacting it, the curing mat is applied to the mortar or concrete before the mortar or concrete finishes setting. The curing method involves removing the mat from the surface, applying a surface finish to the mortar or concrete, and then leaving the curing mat that has adsorbed the excess water again on the mortar or concrete surface to keep the surface in a moist state.

That is, the curing process of the present invention, as shown in FIG.
Concrete I of the curing cloak, g on the surface, filling process (1
) and the contact process of cured pine I to the concrete surface (
2), the removal process of the curing mantle before the end of concrete setting (3), the surface finishing stage of the concrete before the end of concrete setting (4), and the 1f) laying of the curing mantle h before the end of concrete setting. Step (5), leaving the curing pine I. (6), and steps L are carried out in the order of steps, especially the removal of the curing mat 1 before the concrete 1. finishes setting.
- The process from step (3) to re-crystallization step (5) is a unique process not found in conventional curing methods. Here, the end of setting refers to the time at which setting ends from the time of cement water injection, which is determined according to the setting test of JIS R5201, 7, 1.

[Example] Next, the present invention will be explained in detail with reference to examples.

FIG. 2 is a sectional view of a curing cloak according to an embodiment of the present invention. 1st
In the figure, IO is a nonwoven fabric, and 11 is a synthetic resin sheet. This sheath 11 has approximately the same area as the nonwoven fabric 10, and a fiber aggregate 12 mixed with water-retaining water-absorbing material is interposed between the nonwoven fabric 10 and the sheath I 11. The peripheral edges of the nonwoven fabric 10 and the sheet 11 are adhered to each other, and the fiber assembly 12 is wrapped in a furnace.

The nonwoven fabric 1O is preferably a heat-fusible synthetic fiber such as polyester or nylon so that its peripheral edge can be heat-fused to the synthetic resin sheet 11, but it may also be a cellulose fiber that can be sewn with sewing thread or the like.

The synthetic resin sheet 11 is made of polyethylene, polyester,
Examples include sheets made of nylon, polyvinyl chloride, and the like.

Examples of the fiber aggregate 12 include cellulose + LF raw fibers, artificial MS such as protein-based IJAm, synthetic fibers such as polyester, polypropylene, and nylon, and aggregates of fibers. The water-retaining water-absorbing material mixed in is an organic or inorganic water-absorbing material. An example of this organic water-absorbing material is grafted V powder, and an example of an inorganic water-absorbing material is a porous material such as magnesium silicate powder. Examples include silicate powder.These water-absorbing materials can once absorb moisture and then be dried, allowing the moisture to evaporate and be regenerated.

In addition, the amount of iron in the water-absorbing material curing mat depends on the material of the water-absorbing material and the wood-cement ratio.
It is set depending on the type 1 composition, thickness, etc. of the fiber aggregate 12, and the time required for curing.
It is selected from the range of 5 to 5.0 Kg/m'.

The curing mat of the present invention is suitable for use in flat locations such as roads and bridges where concrete surfaces are exposed to the atmosphere.

FIG. 3 is a sectional view showing a specific usage example of the above-mentioned curing mat. This example is an example of curing the paved surface of a road. First, prepare the curing mat shown in Fig. 1 in an area large enough to sufficiently cover the surface of concrete A. Next, the surface of the nonwoven fabric IO of the curing mat is laid so as to face the surface of the concrete A that has just been cast into the formwork and has been leveled. Next, by lightly pressing the curing mat from the side of the synthetic resin sheet 11, excess moisture unnecessary for cement irrigation is guided from the surface of the concrete 1-A to the fiber aggregate 12 through the nonwoven fabric IO. The pressing method may be to press the sheet 11 directly by hand, or by placing a lightweight plate material thereon.

After the water absorbing material mixed into the fiber aggregate 12 adsorbs the excess moisture, the curing mat is removed from the surface of the concrete A before the concrete 1.A reaches the end of setting. After removing the curing mat, finish the surface of concrete 1-A. This surface finishing is carried out using a known finishing trowel, finishing broom, etc. until the required smoothness of the final surface of the concrete 1 is achieved. After finishing the surface, the removed curing mat is gently spread over the surface of concrete 1-A again. The work from removal of the curing mat to re-laying is performed before concrete 1.A finishes setting. In particular, in order to fully demonstrate the effect of surface finishing, it is preferable to perform these operations ((3) to (5) in Figure 1) near the end of setting, but it is preferable to perform these operations ((3) to (5) in Figure 1) near the end of setting. As long as the moisture has been absorbed, there is no problem even before the initial stage of condensation.

Removing the curing mat, finishing the surface, and re-laying the mat before it has finished setting is because once the setting has finished, concrete A will enter the hardening stage, and if stress is applied to the surface during hardening, it may cause fatal problems such as cracks. This is because it may cause defects.

The surface of the re-spread curing mat is already sufficiently impregnated with water and covered with moisture-impermeable synthetic resin sheet II, so if it is left on the surface of concrete A until concrete A has completely hardened, , direct lit [(Even if light or wind hits the curing mat, almost no moisture in the curing mat evaporates, allowing a constant amount of moisture to be applied to the concrete surface over a long period of time.

, [Effects of the Invention] As described above, according to the present invention, in addition to the conventional curing process of a curing mat with high water absorption and water retention performance, a process of removing the curing mat before the end of concrete setting and a process of removing the curing mat from the surface of the concrete are added. By adding a new finishing process and a curing mat re-laying process, it is possible to dissolve the "unevenness" on the concrete surface caused by water absorption and swelling of the curing mat, and also to eliminate unpleasant problems. It has the excellent effect of increasing the strength after curing with fewer man-hours.

[Test Example] Next, a curing test example of concrete 1 using the curing method of the present invention will be described.

Test Example 1> (Curing mat) Graph I-
A curing mat is prepared by heat-sealing each peripheral edge of a polyester nonwoven fabric and a polyethylene sheet with a fiber aggregate mixed with 120 g/m' of converted grass powder.

(b) Specimen! A mortar with a composition of 1 part cement (fy, m ratio), 2 parts Toyoura sand, and water-cement ratio W/C 5, 0, 0% was made into a diameter of 10 cm.
The specimen was cast into a cylindrical form with a height of 20 cm and the surface was leveled. Four of these specimens (test specimens～(
Φ) Create.

(Curing method and various measurements Immediately after surface smoothing, place the above curing cloak on the circular surface of specimens ■ and For specimen (1), the curing mat was removed after 30 minutes had elapsed from the leveling of the surface, and for specimen (2), the same <60 minutes had elapsed, and the water absorption weight of each was measured.Moreover, the water ment ratio of specimens (1) to [Co., Ltd.] was measured. These results are shown in Table 1.Specimens ■ and @ are comparative samples in which no curing mat was spread.Next, after 30 minutes had passed since the surfaces of specimens ■ and 60 minutes after leveling the surface, use a metal trowel to finish the surface.
The curing mats that had been removed were placed on the surfaces of specimens (2) and (2) again and left for 48 hours after the surfaces were leveled.

The above specimens ■ and ■ are covered with curing mats (J
ξ Together with specimens ■ and ■, when the material was 7 days old, it was cut into three layers, top, middle, and bottom, at equal intervals, capped with sulfur, and subjected to a compression test. The test results are shown in Table 1.

Table 1 Indicates the rate of failure (χ).

From the results in Table 1, it can be seen that the water-cement ratio of specimen (1) was reduced by about 3% due to the curing mat, and the water-cement ratio of specimen (?) was also reduced by about 4.6%. In addition, the compressive strength of specimen (i) using the curing mat was 62% in the upper layer, 13% in the middle layer, and 10% in the lower layer, compared to the compressive strength of specimen (i) without the curing mat. did. Similarly, the compressive strength of specimen L using the curing mat was improved by 66% in the upper layer, 22% in the middle layer, and 15% in the lower layer compared to the compressive strength of specimen L without using the curing mat. . This shows that the higher the layer, the higher the strength, and the effect of the curing mat is more pronounced.

Test example 2> Re-nursing mat Same as Test Example 1.

ψ) Specimen Mortar with the same composition as Test Example 1 with a diameter of 24 cffl,
The specimen was cast into a cylindrical form with a height of 20 cm, and the surface was leveled to prepare the specimen. Three of these specimens (test specimens ■～■)
Create.

■ Curing method and various measurements Immediately after finishing the surface smoothing, spread the above curing mat on the circular surface of the specimen (■) with the nonwoven fabric side facing down, press it lightly with your hands, and after 80 minutes have passed, place the curing mat on the circular surface of the specimen (■). It was removed and the water absorption weight was measured. Further, the surface of the specimen (2) was finished using a metal trowel, and then the removed curing mat was spread over the surface of the specimen (2) again and left for 48 hours after the surface was leveled. On the other hand, the specimen after 60 minutes of surface smoothing
■The water-cement ratio was measured. These results are shown in Table 2. In addition, specimen ① is a comparative sample in which no curing mat was laid down and no damage was caused. In addition, for specimen ■, the curing mat was not used until the above 60 minutes had passed, and after the above 60 minutes had passed,
The above-mentioned curing mat, which had been sufficiently impregnated with moisture in advance, was spread with the nonwoven fabric side facing down, and left for 48 hours after the surface was leveled.

The strength of each surface of the above specimens (1) and (2), together with specimen (2) without a curing mat spread, was measured using a Schmidt hammer tester at 3 and 7 days of age. The test results are shown in Table 2.

Table 2 From the results in Table 2, it can be seen that the water-cement ratio of specimen (1) was reduced by approximately 6.3% due to the curing mat.

In addition, the Schmidt/Bemmer value of Φ for the specimen that used a curing mat from the beginning is approximately 2.8 times the Schmidt/Bemmer value of specimen O, which was aged 3G and did not use any curing cloak.
Similarly, the strength had improved by about 1j times at 7 days of age. In addition, there is almost no difference between specimens 0 and ■ in terms of table +fj strength, and it is clear that the surface strength changes depending on the water absorption effect of the curing mat.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of the curing process of the present invention, and FIG. 2 is a sectional view of a curing mat according to an embodiment of the present invention. FIG. 3 is a sectional view showing its usage. A: Concrete, 10: Nonwoven fabric, 11: Synthetic resin sheet, 12: Fiber aggregate. Applicant: Yoshino Rika Jogyo Co., Ltd. Agent: Hajime Kawakami (2 others) Figure 1 Figure 2 Figure 1 Figure 3

Claims (1)

[Claims] (1) Immediately after being driven into the formwork and leveling the surface, the mortar is placed on the surface of the concrete I between the non-woven fabric and the synthetic resin sheet having approximately the same area as the non-woven fabric. A curing mat interposed with a fiber aggregate mixed with a water-retaining water-absorbing material is spread so that the surface of the non-woven IIi faces the mortar or concrete surface, and the non-woven fabric is placed on the concrete surface. After the excess moisture unnecessary for hydration of the cement in the mortar or concrete is adsorbed and removed by the curing mat, the curing mat is placed in the mortar or concrete before the mortar or concrete finishes setting. The method is characterized in that the mortar or concrete is removed from the surface, the surface of the mortar or concrete is finished, and the RLF and the curing mat that has adsorbed the excess moisture are left on the surface of the mortar or concrete to maintain the surface in a moist state. How to cure mortar or concrete.