JPS5829265B2 - Concrete construction - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing high-strength concrete products (including not only concrete products manufactured in so-called factories but also concrete structures cast on site).

More specifically, the present invention has a low water-cement ratio (referred to as the weight percentage of W/C, hereinafter abbreviated as rW/Cl, when the cement amount kc-1 water used in concrete mixing is W~); Moreover, when pouring so-called high-strength concrete with a large amount of cement, the amount of water required can be reduced without impairing the fluidity of the concrete necessary for the work, and it is necessary to obtain concrete of a certain strength. This invention relates to improvements in the manufacturing method of high-strength concrete products that make it possible to reduce the amount of cement used.

High-strength concrete means that the design standard strength of ordinary unreinforced concrete or reinforced concrete is 160 to 240.
350 to 500 kg/Cr
? This type of high-strength concrete is often used as prestressed concrete, and in addition to being required to have a high compressive strength at 28 days, it is also necessary to use a relatively short material ◆. Since prestress is applied, high strength is required even at the initial stage of the material.

Therefore, due to the mix design of concrete, the material ◆28
The cement content is generally considerably richer than the amount of cement per unit that is sufficient to provide the strength required in the day.

In order to obtain high-strength concrete, the amount of cement per unit must be increased, or if the amount of cement is increased carelessly, undesirable effects such as cracks will occur in the product.
Moreover, the cost increases due to the increase in the amount of cement used.

Furthermore, when the unit amount of cement is increased, the adhesiveness of the fresh concrete becomes stronger due to the large amount of cement paste contained in the root rollers, which significantly inhibits fluidity, making it difficult to place concrete, and resulting in high-strength concrete. In particular, it becomes impossible to obtain the dense and homogeneous material that is important in prestressed concrete.

To overcome this difficulty, when mixing conventional high-strength concrete, the workability of fresh concrete can be improved without increasing the unit water volume of concrete, or the unit water volume can be reduced while maintaining the same workability. Various water reducing agents were used for this purpose.

In other words, the strength of concrete depends not only on the unit amount of cement but also on the unit amount of water, and reducing the W/C reduces the pore volume of the hardened material and increases the strength, but reducing the unit amount of water increases the strength of fresh concrete. Since fluidity is inhibited, an appropriate water reducing agent is used to reduce the amount of water to the extent that fluidity is maintained without hindering work, and generally W/C4
It is set at 5% or less.

The inventors of the present invention intended to modify Portland cement in order to maximize the water-reducing effect when using existing water-reducing agents for concrete, and as a result of intensive research, they found that the water-cement ratio was approximately 45. % to 20%, and which is mainly composed of an organic substance having a sulfonic group, and when mixing concrete, it is necessary to mix the water reducing agent on the 70 weight board, preferably 80 weight upwind, of the added plaster. By using Portland cement in the form of CaSO4, it is possible to significantly improve the workability of fresh concrete compared to conventional methods without increasing the unit water content of concrete, and to maintain the same workability. However, we have found that the unit water volume can be greatly reduced.

Thus, by placing concrete according to the present invention, if the same unit amount of cement as in the conventional method is used and the workability of the fresh concrete IJ-t is kept the same, the unit water amount can be further reduced. , a concrete product with higher strength can be obtained, and if the strength of the concrete product is the same as that of the conventional method, the amount of cement per unit can be greatly reduced, and an economical and high-quality concrete can be obtained.

The significance of the present invention is extremely high as the demand for high-strength concrete or products has increased in recent years with the development of civil engineering and construction technology.

There are various types of water reducing agents for concrete, but organic water reducing agents having sulfone groups are most commonly used and effective because they have excellent performance and are easily available economically.

Examples of such water reducing agents include those containing lignin sulfonate or its derivatives as a main component, such as Boblis 5.
-L (manufactured by Bobris Bussan Co., Ltd.) and Plastocrete (manufactured by Nippon Shika Co., Ltd.), those whose main ingredients are alkylaryl sulfonates, such as Mychie 150 (manufactured by Kao Soap Co., Ltd.)
, those whose main component is a sulfonate of an aromatic condensed polycyclic compound, such as Bobris NL1400 (manufactured by Bobris Bussan Co., Ltd.); those whose main component is a sulfonate of a water-soluble melamine-formalin resin, such as Melmen I- Examples include L-10 (manufactured by Showa Denko).

Among these salts, alkali metal and alkaline earth metal salts, especially sodium and calcium salts, are preferred.

The sulfone groups contained in the main components of these water-reducing agents combine with Ca2+ in the Portland cement compound to make part of the surface of the cement particles hydrophobic, and the large negative charge of the organic compound molecules that make up the water-reducing agent disperses the cement particles. This leads to an improvement in cement efficiency due to water reduction effect and cement particle dispersion, which increases concrete strength, but the mechanism is complex and has not been fully elucidated.

Portland cement is produced by adding 2 to 5 weights of plaster to clinker and pulverizing the mixture.

Addition of plaster is essential to prevent rapid setting of cement.

Further, the amount of 803 in Portland cement is at least 0.5%, preferably 1.5 to 2.5%, and if it exceeds 5%, there is a risk of deterioration of concrete quality.

The form of gypsum used is exclusively Sansui Gypsum (Ca S
O, i・2H20) However, as the temperature rises to some extent during the cement grinding process, some or a large portion of the Sanhydrate Gypsum dehydrates and becomes Hemihydrate Gypsum (Ca
S O,i・XH20).

For this reason, the form of gypsum contained in commercially available Portland cement is either trihydrate or hemihydrate, and the ratio of these is dependent on the grinding conditions of the cement and is not necessarily constant0. During manufacturing, plaster (II)
The idea of using -CaSO4) is not necessarily new, and attempts have been made to replace part of the sansui gypsum in order to reduce the drying shrinkage of the cured product.

However, Portland cement, which attempts to harden the entire amount of added plaster, has not been put to practical use because it does not exhibit the same characteristics as mortar or blank concrete that does not use a water reducing agent.

As an example, Table 1 shows cements with different forms of added plaster compared to Portland cement clinker.
The strength was determined according to the JISR5201 cement physical test 1 tatami method, and the results are shown below.

According to these results, even if the entire amount of added plaster is tried to harden, there is no significant difference from other cases.

The present inventors have conducted various studies on the functions of water reducing agents for concrete, and have found two types of water reducing agents: Portland cement in which the added plaster is in the form of hard gypsum, and water reducing agents for concrete whose main component is the above-mentioned organic substance having a sulfone group. By using the water reducing agent in combination, the water reducing and dispersing effect of the water reducing agent is significantly improved. It has been found that the fluidity of fresh concrete can be greatly improved compared to when a water reducing agent is used.

Fluidity or workability of fresh concrete is generally measured by a slump test, and when this slump is held constant, the water reduction effect is further improved compared to conventional methods, and the dispersion of cement is further improved. As a result, homogeneous concrete is obtained without being dense, and the strength increase is 10 when the unit amount of cement is constant.
%, and the cement saving rate reaches 10 to 15% when the strength is the same.

In this way, the form of the gypsum added to Portland cement is hard gypsum, and due to the synergistic effect with a water reducing agent whose main component is an organic substance having a sulfonic group, it is possible to achieve excellent quality that was previously unobtainable. Strong concrete can be obtained, and this effect can only be obtained if at least 70 weight φ or more of the added plaster, preferably 80 weight φ or more, is in the form of hard plaster, and the rest is in the form of sansui or semihydrate plaster. or a mixture thereof.

In addition, high-strength concrete is generally mixed and cast at a W/C of about 45% or less, and the synergistic effect of the above-mentioned hard plaster and a water reducing agent whose main component is an organic substance having a sulfone group is such that the W/C is about 45% or less. This is particularly noticeable when the W/C is 20%, and the effect becomes smaller in the case of so-called soft concrete with a large W/C.

In other words, as an example, if we talk about mixed concrete for construction with a W/C of 69%, if Portland cement in which the form of added gypsum is anhydrite is used, the slump value is 1.
9.2 cm (28-day compressive strength 256 kg/Crl1), but when the added gypsum is used in commercially available Portland cement l-, which is a mixture of trihydrate and hemihydrate gypsum, the slump value is 18.9 cm (28-day compressive strength 258 kg/Crl1). 9/cI?L
), and there is no big difference between the two.

The high-strength concrete obtained in this way is not limited to concrete products manufactured in factories, but is
It goes without saying that exactly the same effect can be obtained even in the construction of prestressed concrete structures cast on site using a water reducing agent whose main component is an organic substance having a sulfonic group and whose water-reducing agent is 45% or less. do not have.

Next, the present invention will be explained in more detail with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist thereof.

Example 1 Standard Boltland Cement Talinker (HM=2.
10. SM=2.7, IM=1.6) were added with trihydrate plaster, amniotic plaster and faecal plaster, respectively, and ground to a specific surface area of 3150±30 CIIt/9 to obtain cement.

The amount of plaster added is based on the SO3 content in the cement.
%.

455 kg of cement per 1 m3 of concrete, fine aggregate (
River sand, FM = 2.83) 714 kg, coarse aggregate (crushed stone, FM = 6.77) 1086 to 9, water 162 kg
(w/c = 35.6%), water reducing agent for concrete (43 weight φ aqueous solution of alkylaryl sulfonate, My Chi 150, manufactured by Kako Soap Co., Ltd.) 2.7 kg (for cement 1 to 0
．． 90% by weight) in a force-stirred mixer.
Kneaded for seconds.

Next, using a slump cone with a height of 30 cm, JIS
, Measure the slump of concrete according to All0I and JIS.

Create a cylindrical specimen for strength testing according to A1132. After steam curing and standard curing (20°G in water), JIS, A1
The strength was measured by the 108 method and the results are shown in Table 2.

was obtained.

Steam curing was carried out by raising the temperature from room temperature to 60°C in 3 hours after 3 hours had elapsed after molding the specimen, and holding it at that temperature for 5 hours, and the strength upon demolding was measured 17 hours after molding the specimen.

In addition, steam curing material 4>28 day strength indicates the strength measured at 28 days after the specimen was cured in water after demolding.

From the results listed in Table 2, it can be seen that the same formulation, that is, constant W/C (3
5.6%), when concrete is poured using a concrete water reducing agent whose main component is an organic substance having a sulfonic group, and when the concrete is in the form of plaster added to cement or in the form of hard plaster. It is clear that the slump development property is significantly better and the strength development property is also superior to that of using other types of cement in the form of added plaster, ie, commercially available Portland cement.

Example 2 In Example 1, three types of cement were used, each with a different form of added plaster and each with an S03 content of 2.0% by weight.
e The slump and strength of concrete were measured when various types of plaster coexisted by mixing at various weight ratios, and the results shown in Table 3 were obtained.

The concrete mix and other experimental conditions were the same as in Example 1.

From Table 3, at least 70% of added plaster in cement
It is clear that when more than % by weight is in the form of plaster, the development of slump is significantly improved, and as shown in Table 3, the development of strength is also good.

Example 3 Approximately 90% by weight of the added gypsum was in the form of anhydrous gypsum, with the remainder consisting of trihydrate and hemihydrate gypsum.Portland cement (HM=2.08,
SM=2.7, IM=1.7.803=1.8φ, specific surface area 3050i/, 9) and commercially available Portland cement (HM= 2.07, SM=2.5,.

In order to compare the slump and strength of concrete using various water reducing agents for concrete having sulfone groups, Example 1 The results shown in Table 4 were obtained when comfleet concrete was poured using the same formulation and experimental conditions.

In addition, the strength shows the value for standard curing.

As is clear from Table 4, a concrete admixture containing an organic sulfonate as a main component is used, and the same mix, that is, W/C
When concrete is poured at a constant rate (35,6 yen), by using Portland cement whose added plaster is mostly hard plaster, slump is reduced compared to when commercially available Portland cement is used. The development property is significantly improved, and the development property of strength is also good.

Example 4 Concerning the cement of Example 1, a test mix of concrete was carried out, a mixture that gave the same slump of 5±ICIrL was determined, and a strength test of the concrete was conducted.
I got the results in the table.

The water reducing agent used, its usage amount, aggregate, concrete kneading, curing method, etc. are the same as in Example 1.

As is clear from the results shown in Table 5, by using Portland cement in which the form of added plaster is hard plaster according to the present invention, the conventional commercially available Portland cement, that is, the form of added plaster, can be Compared to the case of using water or semi-water plaster, if concrete is placed under constant slump conditions, the amount of water used can be significantly reduced, and as is clear from Example 1, even with the same amount of water. Even when concrete is poured, the strength of the present invention is significantly increased due to the synergistic effect of obtaining concrete with higher strength than the conventional method, and the significance of the present invention is significant.

Example 5 Approximately 95% of the added gypsum is hard plaster, and the remainder is semi-hydrated gypsum.Portland cement, which is the main component of the present invention (HM=2.14°SM=2.6
, IM=1.6, S03=1.8φ, specific surface area 3230cr? commercially available Portland cement (HM=2.12°SM=2.t/g) and the form of the added plaster is mostly half-hydrated gypsum and partly trihydrated.
5, IM = 1.6, 803 = 1.9 coefficient, and specific surface area of 3260 ari/l were selected as targets, and concrete tests were conducted under conditions of constant slump (5 ± 1 cm) by varying the amount of cement mixed.

Table 6 shows the concrete mix and measurement slump.

The aggregate used and the test conditions other than those listed in Table 6 were the same as in Example 1.

The Portland cement of the present invention and the commercially available Portland cement were selected as targets, and a water reducing agent for concrete (43 weight φ aqueous solution of alkylaryl sulfonate, MyChi 1
50) Figure 1 shows the relationship between cement content and strength when a concrete test was carried out under the condition of constant slump (5±l cm) using 0.6 weight more than i cement content.

The graph shows the relationship between the steam-cured demolding strength and the standard curing material◆28-day strength on the vertical axis and the cement content on the horizontal axis.

From FIG. 1, it is possible to estimate the amount of cement required to obtain the same strength in concrete using the Portland cement of the present invention and commercially available Portland cement.

From these results, the strength during steam curing demolding was set to 4509/
According to the present invention, the amount of cement used can be reduced by about 55 kg/m'' (12%) compared to the conventional method, and the 28-day strength of the standard curing material can be reduced to 750 kg/criL.
When compared to the conventional method, it can be easily estimated that the amount of cement used can be reduced to about 70% by 9/vr (14%), which shows that the economic effect of the present invention is extremely high. Thick.

Example 6 For the purpose of observing the effect of trying to harden the form of added plaster for early-strength Portland cement, which is often used in high-strength concrete, early-strength Portland cement clinker (HM = 2.26, SM
= 2.8, IM = 1.7), anhydrous gypsum and semi-hydrated gypsum were individually added and crushed so that the S03 content in the cement was 2.5%, and the specific surface area was 4250i.
/9 cement was obtained.

410 cement per liter of concrete! 9. Fine aggregate (river sand, FM=2.80) 736k19, coarse aggregate (crushed stone, FM=6.78) 1146kg, water 173! 9
(W/C = 42.2%), water reducing agent for concrete (43 weight aqueous solution of alkylaryl sulfonate, My Chi 150, manufactured by Kako Soap Co., Ltd.) 2.45 kg (for Shichimen l-
A material of 0.6 weight φ) was used and mixed for 90 seconds using a forced-to-bone stirring mixer to obtain concrete.

Table 7 shows the results of measuring concrete slump and concrete strength using the method described in Example 1.

From the results listed in Table 7, the same proportion, that is, constant W/C (4-2
, 2%), when concrete is poured using a water reducing agent for concrete mainly composed of organic substances having sulfonic groups, and when the form of the plaster added to the Portland cement is anhydrous plaster. , the occurrence of slump is significantly improved compared to the case of using cement in which the form of added plaster is semi-hydrated plaster, and the same -W/
It is understood that even C has higher strength, and the object of the present invention can be achieved in early-strength type Portland cement in the same way as in ordinary Portland cement.

Example 7 In Example 1, when the form of the added plaster is anhydrite and trihydrate, the amount of added plaster is changed depending on the SO3 in the cement: 1.5, 2.0, 2.5°3.0
Adjust to weight percent, specific surface area 3150
±3o=,', p's Sefa 14 admonition.

Concrete was poured using these cements under the same conditions as in Example 1, and the slump of the concrete and the 28-day strength of standard cured concrete specimens were measured, and the results shown in Table 8 were obtained.

As is clear from Table 8, the effect of the amount of added plaster on the slump and strength of concrete is the same for Sansui Gypsum and Gypsum, and the amount of Gypsum added to Portland cement is Even if this is used, it is considered that the judgment can be made based on the same well-known knowledge as conventional commercially available Portland cement, and there is no need to be particularly limited, and regardless of the amount of added plaster, the form is In this case, the slump development property is always better than in the case of Sansui Gypsum, and the strength is also better.

Example 8 In Example 5, per concrete') -11 m', 500 kg of cement, 686 kg of fine aggregate, and 1086 kg of coarse aggregate were used.
kg, water 158 kg (W/C = 31.6%) concrete water reducing agent (43 weight aqueous solution of alkylaryl sulfonate, My Chi 150, manufactured by Kako Soap Co., Ltd.) 6.0 k
Concrete was cast using a mixing ratio of 1.2 g (by weight of cement), and the molded specimen was cured in an autoclave.

Autoclave curing was performed 3 hours after molding the specimen.
The temperature was raised to 60°C at a heating rate of 20°C/Hr, and after steam curing at this temperature for 5 hours, the steam pressure was 10 kg/Hr.
CI? t, that is, curing at 179° C. for 6 hours → conditions were set.

As is clear from the results listed in Table 9, by using Portland cement in the form of added gypsum or mostly composed of hard gypsum, the slump resistance is much better than in the conventional method, and the autoclave curing strength is also improved. Are better.

Furthermore, from this table, when the Portland cement of the present invention is placed in the same slump as commercially available Portland cement, it is possible to reduce the amount of water used by at least 15 to 9/m' compared to the amount of water used in the conventional method. I can understand.

Therefore, the strength after autoclaving is further improved,
We can expect a greater effect.

[Brief explanation of the drawing]

Figure 1 shows the strength when demolding after steam curing and the standard curing material 4>28
It is a graph showing the relationship between daily strength and amount of cement used.

Claims (1)

[Claims] 1 When kneading a concrete water reducer with a water-to-cement ratio of 45 weight φ or less and containing a sulfonic group-containing organic substance as a main component and mixing it in a comfleet truck, it is necessary to If Ca
A method for producing a high-strength concrete product, characterized by using Portland cement in the form of SO4.