JPH05310454A - Production of light-weight concrete having low shrinkage - Google Patents

Abstract

PURPOSE:To produce a light-weight concrete having excellent dimensional stability by using an inorganic foam as an aggregate. CONSTITUTION:550-750kg binder comprising 8-63wt.% Portland cement, 4-56wt.% fine powder of blast furnace slag and 30-60 silica rock powder based on 1m<3> light weight concrete having low shrinkage is blended with water, a blowing agent, a water-reducing agent and an inorganic foam having 200-1,000 liter bulk volume and cured in an autoclave to give a low-shrinkage light-weight concrete having <=100kg/cm<2> compression strength, <=0.10 shrinkage percentage after drying for 13 weeks, <=0.10% carbonization ratio for two weeks, <=0.22% carbonization ratio for four weeks and 0.75-1.20 specific gravity.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a low shrinkage lightweight concrete obtained by curing an autoclave. More specifically, it relates to a method for producing a lightweight concrete characterized by low shrinkage obtained by curing an autoclave containing an inorganic foam as a lightweight aggregate.

[0002]

2. Description of the Related Art Conventionally, as lightweight concrete, calcined raw materials such as cement, siliceous raw materials such as silica powder, and a semi-hardened body obtained by introducing a large amount of bubbles into water have a specific gravity obtained by autoclave curing. An ALC of about 0.6 is common. In recent years, AL has been used to improve strength and durability.
Attempts have been made to develop concrete having a higher specific gravity than C. When the amount of air bubbles introduced in ALC is reduced, the proportion of the matrix in aerated concrete increases even when autoclave curing is performed, and therefore the tendency for dry shrinkage to increase becomes stronger. It has not been put to practical use due to the problem of warpage. Therefore, in the case of lightweight concrete having a specific gravity of about 0.8 to 1.5, an inorganic foam generally called perlite is used in combination for the purpose of weight reduction, reduction of matrix amount and high strength.

Perlite used as a lightweight aggregate is mainly obsidian type perlite. Sasaki et al. "Water absorption of various pearlites and lightweight mortars using them"
(Annual report of cement technology 40, PP 119-122, 1
As described in 986), the obsidian type of pearlite has a large number of independent bubbles inside, so that the water absorption rate is low and the aggregate strength is high, so the concrete using this has excellent strength characteristics. .. The dry shrinkage property is also relatively good, but it is large compared to general concrete using ordinary aggregate. Further, even when obsidian-based pearlite is used, its air permeability is higher than that of general concrete, so that the rate of carbonation becomes faster, and shrinkage accompanying carbonation occurs. Although the shrinkage due to carbonation has not been a big problem in the past, the accelerated experiments by the inventors have shown that the shrinkage is considerably larger than the dry shrinkage. Although the progress of carbonation does not occur rapidly, it is considered to have a great influence on the cracking due to the contraction of the member in the long term.

Further, since other pinelite-based or pearlite-based pearlite has a large number of continuous or open pores having openings on the surface, it has a very high water absorption rate and weak aggregate strength. Therefore, the concrete using these has a large amount of water used for securing fluidity, and even when cured in an autoclave, the strength of the cured product is low and the drying shrinkage is very large.

[0005]

Although the inorganic foams represented by perlite are easily available on the market, they are generally rarely used as aggregates for concrete because of the above-mentioned reasons. It is used as a filtering material, soil improving material, horticultural, and filling material for cold / heat retaining walls by utilizing its porosity. For concrete, it is often used in parts that do not require strength such as heat insulating materials, sound absorbing materials, backfill materials, plaster materials, etc., and are also used for parts that are not affected by drying, and external wall materials that require strength and durability. It was rarely used for members that combine with steel or reinforcing bars. Especially when used as reinforced concrete,
Large dry shrinkage may cause cracking.

The present inventor has conducted earnest studies for the purpose of establishing a method for producing a lightweight concrete having small dimensional stability with small drying shrinkage and carbonation shrinkage, even though the inorganic foam is used as a lightweight aggregate. The present invention has been reached.

[0007]

That is, the gist of the present invention is that 8 to 63% by weight of Portland cement, 4 to 56% by weight of blast furnace slag fine powder and 30 to 60% by weight of silica stone per 1 m ^{3 of} low shrinkage lightweight concrete. 550 to 750 kg of a binder made of water, water, a foaming agent, a water-reducing agent, and an inorganic foam having a bulk volume of 200 to 1000 liters are mixed, mixed, and further autoclaved, and a compression strength of 100 kg / cm ² or more, 13 weeks dry shrinkage 0.10% or less, 2 weeks carbonation shrinkage 0.10% or less, 4 weeks carbonation shrinkage 0.22% or less and specific gravity 0.7
It is a method for producing a low shrinkage lightweight concrete having properties of 5 to 1.20.

The Portland cement used in the present invention is an ordinary cement, an early early cement, an ultra early early cement, a moderate heat cement and a sulfate resistant cement, and the compounding amount in the binder is 8 to 63% by weight, preferably 35%. ~ 50% by weight.

The blast furnace slag fine powder used in the present invention is obtained by rapidly cooling and crushing molten slag produced at the same time as pig iron in a blast furnace, and JIS R 5211 “Blast furnace cement” or the Japan Society of Civil Engineers standard “Blast furnace slag fine powder for concrete”. Ordinary ones defined in the "powder specifications (draft)" may be used. The grain size is a Blaine value of 2500 cm ² / g or more, generally 2
It is about 500 to 5000 cm ² / g. Finer powdering is preferable for improving the demolding strength and the resistance to material separation.

The blending amount of the blast furnace slag fine powder in the binder is 4
˜56 wt%, preferably 10-40 wt%. If the blending amount is less than 4% by weight, the effect of improving shrinkage cannot be expected, and if it exceeds 56% by weight, the shrinkage properties of the hardened material are good, but the cement content is low and the setting of concrete is delayed. Separation may occur, or mold demolding may be delayed, affecting productivity.

The silica powder is generally used as a siliceous raw material having a high purity of SiO ₂ content of 60% or more, preferably 90% or more, in order to supplement SiO ₂ necessary for hydrothermal reaction in an autoclave. Grain size is 2000 in brane
cm ² / g or more, and generally 2500~5000cm ² /
It is about g. The amount of silica powder in the binder is 30-
It is 60% by weight, preferably 35 to 45% by weight. If the blending amount is less than 30% by weight, SiO ₂ in the binder will be insufficient, and the production of tobermorite due to the hydrothermal reaction in the autoclave will be insufficient and the pouring of the hardened concrete will be reduced. If the blending amount exceeds 60% by weight, the content of cement in the binder will be small and the setting of concrete will be delayed. Fly ash can also be used as the siliceous raw material.

The inorganic foam is "perlite" specified in JIS A 5007 obtained by firing and foaming obsidian, pearlite, pine rock, etc., the inorganic foam proposed in JP-A-61-197479, expansive shale, and Japanese cedar. It is an ultralight aggregate made by firing and foaming stones. In the present invention, the unit volume weight is 0.
1 to 0.6 kg / liter, a particle size of 20 mm or less, preferably a unit volume weight measured by the method of JIS A 5007 "Perlite" of 0.15 to 0.4 kg / l and a particle size of 5 mm or less are used. .. If the unit volume weight is less than 0.1 kg / liter, the water absorption becomes high, the amount of water for mixing to obtain the fluidity of concrete becomes large, and the aggregate strength also becomes small, so that sufficient concrete strength cannot be obtained. .. Unit volume weight is 0.6
If it is larger than kg / liter, it is difficult to obtain concrete with low specific gravity, and it is possible to use a large amount of bubbles together to reduce the weight. The physical properties of the hardened concrete deteriorate because the uniformity of distribution is impaired and it becomes difficult to use a large amount of aggregate.

The amount of the inorganic foam compounded is 1 m of concrete.
^The bulk volume per ³ is 200 to 1000 liters.
If the amount is less than 200 liters, the effect of improving the physical properties of the hardened concrete will not be sufficiently exhibited. Also, 100
If it is more than 0 liters, not only the amount of water for obtaining the fluidity of the concrete increases and the physical properties of the hardened product decrease, but also the workability of the concrete decreases due to the large amount of aggregate and the lack of matrix amount. It causes problems in finishing. Here, the bulk volume is the volume in the state in which pearlite is placed in a container without scooping a shovel or the like, and is the volume in the state in which compaction such as vibration and impact is not performed.

The water reducing agent is used to improve the fluidity of the concrete and further reduce the amount of water used for the concrete to further improve the physical properties of the hardened product. As the water-reducing agent, a high-performance water-reducing agent, a high-performance AE water-reducing agent, an AE water-reducing agent, a water-reducing agent for cement, etc. can be used, and the amount of the water-reducing agent is 0.005 to 5% by weight based on the binder.

The foaming agent is used for reducing the weight of concrete and improving workability, and the method of introducing bubbles may be any of a preform method, a mixed foam method and an after foam method. Examples of the foaming agent include synthetic surfactant-based, resin soap-based and protein-based surfactants for cement. A foaming agent such as aluminum powder can also be used. Further, a cellulosic thickening agent, a polymer such as PVA or other admixture having a thickening action such as starch can be used for stabilizing the bubbles.

Next, an example of the manufacturing method of the present invention will be described. A predetermined amount of water, Portland cement, silica powder, blast furnace slag fine powder, an inorganic foam and a water reducing agent are mixed, and the mixture is kneaded in advance with a mixer to form a slurry, and then a foaming agent is used to foam the foam. The mixture is added to a predetermined kneading unit volume weight and further mixed. This concrete uncured body is cast on a mold made of steel, etc., and after demolding, for example, 1
When the autoclave is cured for 5 hours under the conditions of 80 ° C. and 10 atm, a lightweight concrete having a small drying shrinkage and a carbonation shrinkage and a large compressive strength can be obtained. As the curing method of the present invention, autoclave curing is adopted. This is because the shrinkage reducing effect of the present invention is due to the formation of tobermorite during autoclave curing, as will be described later. The conditions for curing the autoclave are not particularly limited, but a temperature of 180 ° C., 10 atm, and a holding time of 5 to 10 hours, which are used for the production of ordinary cement secondary products, are suitable.

[0017]

The calcium hydrate hydrate formed in the cured product after autoclave curing is crystalline 11 angstrom tobermorite and low crystalline CSH. Of these, the amount of tobermorite produced correlates with the drying shrinkage,
It is said to be related to strength. It is also said that the low crystalline calcium silicate hydrate is decomposed into calcite or vaterite and silica gel by carbonation, and at this time, a large shrinkage occurs.

When the cured autoclave cured product according to the present invention is observed by X-ray diffraction, CSH in the cured product is not detected. That is, the crystallization from CSH to tobermorite is almost completely achieved by the hydrothermal reaction during autoclave curing. A certain amount of inorganic foam as aggregate in the cured body and a certain proportion of cement as a binder,
The formation of tobermorite is promoted only when the blast furnace slag fine powder and silica powder are blended.

[0019]

【Example】

Example 1 278 kg of water, 250 kg of Portland cement, 278 kg of silica powder, 167 kg of blast furnace slag fine powder, 200 liters of pearlite pearlite (bulk volume) and 6.94 kg of a water reducing agent were mixed and kneaded with a mixer, and then foamed. Foam preformed with the agent was added to produce a concrete uncured body having a unit volume weight of 1.02 kg / liter. The flow value of the uncured concrete is 1 min after pulling up the container after filling the uncured concrete into a φ8 × 8 cm steel cylindrical container placed on an acrylic plate and scraping off the excess uncured concrete. The subsequent spread of the uncured concrete was 200 mm. This concrete uncured body was cast into a 4 × 4 × 16 cm steel mold, and then demolded in 24 hours, and the temperature was 180 ° C.
A test specimen was manufactured by carrying out autoclave curing for a period of time. The specific gravity of the finished concrete was 0.80.

The specimen after curing in the autoclave was immersed in water for 7 days, and the length of the specimen at this point was used as a base length.
20 ° C., R. H. The length change after standing still in a 60% constant temperature and humidity chamber for 13 weeks was measured, and the dry shrinkage ratio was calculated. In addition, the compressive strength of the specimen after curing in the autoclave is determined by JIS
It measured based on R5201. The results are shown in Table 1 and Table 2.
Shown in.

[0021]

[Table 1]

[0022]

[Table 2]

The properties and the like of the raw materials used in the examples and comparative examples of this specification are as follows. Portland Cement: Early Strength Portland Cement (manufactured by Ube Industries, Ltd.) Specific gravity 3.14, Blaine 4520 cm ² / g Silica powder: Specific gravity 2.65, Blaine 3
500 cm ² / g Blast furnace slag fine powder: Brand name Powerment (manufactured by Ube Industries, Ltd.) Specific gravity 2.90, Blaine 4110 cm ² / g Pearlite pearlite: Brand name Perlite type 2 (manufactured by Ube Industries, Ltd., raw material Is a pearlite from Himejima, Oita prefecture.) Unit volume weight 0.24 kg / liter, particle size less than 5 mm U-lite: Product name U-lite 1 (manufactured by Ube Industries, Ltd.) Unit volume weight 0.35 kg / Liter, particle size 2.5mm
Less than obsidian perlite: Toho Perlite Co., Ltd.
Unit volume weight 0.32 kg / liter, particle size 2.5 mm
Less than Foaming agent: Product name Monoclet (manufactured by Daiichi Kasei Sangyo Co., Ltd., main component; animal hydrolyzed protein) Water reducing agent: Product name Mighty 150 (manufactured by Kao Corporation, anionic surfactant (main component) ; Naphthalene sulfonic acid / formalin highly condensed salt)))

Example 2 The same as Example 1 except that 282 kg of water, 231 kg of Portland cement, 257 kg of silica stone powder, 154 kg of blast furnace slag fine powder, 400 liters of perlite type perlite (bulk volume) and 6.42 kg of water reducing agent were used. A slurry, an uncured concrete, and a test piece were manufactured, and the dry shrinkage ratio and the compressive strength were measured in the same manner as in Example 1.
The results are shown in Tables 1 and 2.

Example 3 Same as Example 1 except that 300 kg of water, 277 kg of Portland cement, 230 kg of silica powder, 69 kg of fine blast furnace slag powder, 600 liters of perlite type perlite (bulk volume) and 5.76 kg of water reducing agent were used. A slurry, an uncured concrete, and a test piece were manufactured, and the dry shrinkage ratio and the compressive strength were measured in the same manner as in Example 1. The results are shown in Tables 1 and 2.

Example 4 Same as Example 1 except that 304 kg of water, 206 kg of Portland cement, 229 kg of silica powder, 138 kg of blast furnace slag fine powder, 600 liters of perlite type perlite (bulk volume) and 5.73 kg of water reducing agent were used. A slurry, an uncured concrete, and a test piece were manufactured, and the dry shrinkage ratio and the compressive strength were measured in the same manner as in Example 1.
The results are shown in Tables 1 and 2.

The same test piece was dried with a hot air circulation dryer to 7
After drying at 0 ° C. for 24 hours, 20 ° C. and R.I. H. 60
%, The rate of change in length when left to stand under accelerated carbonation conditions with a CO ₂ concentration of 5% (carbonation shrinkage rate) was measured with the uncured product being demolded as the base length. The results are shown in Tables 1 and 2.

The uncured concrete of this composition was set with a deformed steel bar (D19) centered in the axial direction.
It was cast in a steel mold of × 10 × 40 cm, and autoclave-cured in the same manner as in Example 1 to produce a test piece as shown in FIG. The test piece in which this deformed steel bar was arranged in the axial center was similarly dried at 70 ° C. for 24 hours and then at 20 ° C. H. 60
%, CO ₂ concentration of 5% was left under accelerated carbonation conditions. Fig. 2 shows the state of cracks (expanded view of the test piece) up to a standing period of 4 weeks. The specimen did not crack at all until the accelerated carbonation period of 3 weeks. The X-ray diffraction result of the sample is shown in FIG. A clear diffraction peak of 11 angstrom tobermorite is observed. However, CSH is not recognized.

Example 5 Same as Example 1 except that 272 kg of water, 145 kg of Portland cement, 242 kg of silica stone powder, 217 kg of blast furnace slag fine powder, 600 liters of perlite type perlite (bulk volume) and 6.04 kg of water reducing agent were used. A slurry, an uncured concrete, and a test piece were manufactured, and the dry shrinkage ratio and the compressive strength were measured as in Example 1.
The results are shown in Tables 1 and 2.

Example 6 Water 247 kg, Portland cement 202 kg, silica powder 225 kg, blast furnace slag fine powder 135 kg, U-
Light 600 liters (bulk volume) and water reducing agent 5.6
A slurry, an uncured concrete and a sample were produced in the same manner as in Example 1 except that 2 kg was used, and the dry shrinkage, compressive strength and carbonation shrinkage were measured in the same manner as in Example 4. The results are shown in Tables 1 and 2.

Example 7 A slurry was prepared in the same manner as in Example 1 except that 261 kg of water, 204 kg of Portland cement, 227 kg of silica powder, 136 kg of blast furnace slag fine powder, 600 liters of obsidian perlite (bulk volume) and 5.67 kg of water reducing agent were used. Then, uncured concrete and test specimens were manufactured, and the dry shrinkage, compressive strength and carbonation shrinkage were measured in the same manner as in Example 1. The results are shown in Tables 1 and 2.

Comparative Example 1 Using 281 kg of water, 444 kg of Portland cement, 296 kg of silica powder and 7.40 kg of water reducing agent,
A slurry, an uncured concrete and a sample were manufactured in the same manner as in Example 1 except that the blast furnace slag fine powder and the lightweight aggregate were not used, and the drying shrinkage rate, the compressive strength and the carbonation removal were performed in the same manner as in Example 4. The shrinkage ratio was measured and the cracking condition due to carbonation was observed. The results are shown in Tables 3 and 4 and FIG.

[0033]

[Table 3]

[0034]

[Table 4]

The specimen with the deformed steel bar cracked after curing in the autoclave, and the crack increased as the accelerated carbonation period passed. Moreover, the X-ray-diffraction result of a specimen is shown in FIG. Both 11 angstrom tobermorite and CSH peaks are observed, but the peak value of tobermorite is much lower than in the case of Example 4.

Comparative Example 2 A slurry was used in the same manner as in Example 1 except that 276 kg of water, 268 kg of Portland cement, 298 kg of silica powder, 179 kg of blast furnace slag fine powder and 7.45 kg of water reducing agent were used, and no lightweight aggregate was used. An unhardened concrete body and a test piece were manufactured, and the drying shrinkage rate, compressive strength and carbonation shrinkage rate were measured and the cracking state due to carbonation was observed in the same manner as in Example 4. The results are shown in Tables 3 and 4 and FIG.

The specimen with the deformed steel bar cracked after curing in the autoclave, and the cracking increased as the accelerated carbonation period passed. Moreover, the X-ray-diffraction result of a specimen is shown in FIG. Both 11 angstrom tobermorite and CSH peaks are observed, but the peak value of tobermorite is much lower than in the case of Example 4.

Comparative Example 3 Water 283 kg, Portland cement 414 kg, silica powder 276 kg, pearlite perlite 200 liters (bulk volume) and water reducing agent 6.90 kg were used, except that blast furnace slag fine powder was not used. A slurry, an uncured concrete, and a specimen were manufactured in the same manner as in Example 1, and the dry shrinkage ratio and the compressive strength were measured in the same manner as in Example 1. The results are shown in Tables 3 and 4.

Comparative Example 4 Example 1 was repeated except that 300 kg of water, 346 kg of Portland cement, 231 kg of silica powder, 600 liters of perlite type perlite (bulk volume) and 5.77 kg of water reducing agent were used, and no blast furnace slag was used. A slurry, an uncured concrete, and a specimen were produced in the same manner as in, and the drying shrinkage, compressive strength, carbonation shrinkage, and cracking due to carbonation were observed in the same manner as in Example 4. The results are shown in Tables 3 and 4 and FIG.

The specimen with the deformed steel bar placed at 70 ° C. and 24
After the time dried it cracked. After that, cracking occurred under accelerated carbonation conditions, but hardly increased after 2 weeks. Moreover, the X-ray-diffraction result of a specimen is shown in FIG. 11 angstrom tobermorite and C
Both SH peaks are observed, but the tobermorite peak value is much lower than in the case of Example 4.

Comparative Example 5 As Example 1 except that 270 kg of water, 324 kg of Portland cement, 216 kg of silica stone powder, 600 liters (bulk volume) of U-light and 5.40 kg of water reducing agent were used, and no blast furnace slag was used. Similarly, a slurry, an uncured concrete, and a specimen were manufactured, and similarly to Example 4, the dry contraction rate, the compressive strength, the carbonation shrinkage rate, and the cracking state due to carbonation were observed. The results are shown in Tables 3 and 4 and FIG.

The test piece on which the deformed rod rope is arranged is 70 ° C., 24
Cracking occurred after drying for a period of time, and the cracking also increased with subsequent accelerated carbonation period.

Comparative Example 6 As Example 1 except that 232 kg of water, 358 kg of Portland cement, 238 kg of silica powder, 600 liters of obsidian pearlite (bulk volume) and 5.96 kg of water reducing agent were used, and no blast furnace slag was used. Similarly, a slurry, an uncured concrete, and a specimen were manufactured, and similarly to Example 4, the dry shrinkage rate, the compressive strength, the carbonation shrinkage rate were measured, and the cracking state due to carbonation was observed. The results are shown in Tables 3 and 4 and FIG.

The specimen with the deformed steel bar placed at 70 ° C. for 24 hours.
After the drying for a certain period of time, the cracking was mainly observed, and the cracking also increased with the progress of the accelerated carbonation period.

[0045]

As is apparent from the above description, according to the present invention, it is possible to obtain a lightweight concrete having excellent dimensional stability even though an inorganic foam is used as an aggregate for concrete.

[Brief description of drawings]

FIG. 1 is a specimen for observing the occurrence of cracks due to carbonation contraction.

FIG. 2 is a cracked state under accelerated carbonation conditions of a test piece in which the deformed rods in Example 4, Comparative example 1, Comparative example 2, Comparative example 4, Comparative example 5, and Comparative example 6 are arranged in the axial center. FIG.

FIG. 3 shows Example 4, Comparative Example 1, Comparative Example 2 and Comparative Example 4.
3 is an X-ray diffraction diagram of the lightweight concrete manufactured in FIG.

Claims (1)

[Claims] 1. Portion cement 8 to 63% by weight, blast furnace slag fine powder 4 to 56% by weight and silica stone powder 30 to 60% by weight per 1 m ^{3 of} low shrinkage lightweight concrete.
550 to 750 kg of a binder made of water, water, a foaming agent, a water-reducing agent, and an inorganic foam having a bulk volume of 200 to 1000 liters are mixed, mixed, and further autoclaved, and a compression strength of 100 kg / cm ² or more, 13 weeks dry shrinkage 0.10% or less, 2 weeks carbonation shrinkage 0.10% or less, 4 weeks carbonation shrinkage 0.22% or less, and specific gravity 0.75 to 1.20 Method for producing low shrinkage lightweight concrete having.