JPS5915105B2 - Cement retarder for preventing cold joints - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a cement retarder 1, particularly a cement retarder containing a calcium aluminate-based material containing fluorine to prevent cold joints.

Conventionally, when constructing a structure by pouring concrete into pour concrete and concrete to be poured, the setting and hardening time naturally differs depending on the time difference between pouring the concrete, so water usage of the cement in the pour joint area is affected. The amount of heat generated becomes uneven, causing cracks called cold joints.

As one of the countermeasures against this problem, a method has been proposed in which a known cement retarder is added to the concrete so that the setting and hardening times of the concrete to be poured and the concrete to be poured are approximately the same.

However, the known cement retarder does not provide a fundamental solution because it delays not only the setting but also the hardening speed of the cement, and in some cases causes poor hardening.

The present inventor has conducted various studies on cement retarders that only delay the setting time of cement but does not have a large effect on the hardening speed, and has found that calcium aluminate-based materials containing fluorine are effective. This has led to the present invention.

That is, the present invention provides 3Ca0・3A1203・CaF2
and/or crystallized products of 11Ca0.7A71!203.CaF2, and/or amorphous products having the same chemical composition as these crystallized products (hereinafter, these are simply referred to as calcium haloaluminates).

).

Furthermore, these calcium haloaluminate powders 1
A cement retarder for preventing cold joints, characterized in that it contains an easily soluble inorganic sulfate in a ratio of 100 parts by weight or less to 00 parts by weight.

In the past, calcium haloaluminate was known to have the effect of rapidly hardening cement when used in combination with insoluble anhydrite, but as mentioned above, it only delays the setting of cement and does not affect the hardening speed. The present inventor discovered this property for the first time.

Therefore, the feature of the present invention is that the unique properties of this calcium haloaluminate are applied to a cement retarder for preventing cold joints.

In the present invention, calcium haloaluminate uses a crystallized product and an amorphous product, and the crystallized product refers to 3Ca
0.3A1203.CaF2 and 11CaCL7A120
It is obtained by adjusting the molar ratio of raw materials containing these to obtain 3.CaF 2 and then heat-treating this at a high temperature.

Further, the amorphous material is obtained by melting the raw material and rapidly cooling it.

Calcium haloaluminate powder as cement retarder
When added to cement, as the amount added increases, the effect of retarding the setting of the cement increases, but as a result, the cement becomes more rapid-setting, so by replenishing it, it is easier to control the setting of the cement. Therefore, it is advantageous to use a readily soluble inorganic sulfate in combination.

Easily soluble inorganic sulfates include gypsum other than insoluble anhydrite, such as Ca5O4-HH2o, type Ca5O4Ca
These are SO4.2H20 and MgSO4, and other sulfates have no significant effect.

When calcium haloaluminate and easily soluble inorganic sulfate are used together as a cement retarder, the proportion is 100 parts by weight or less, preferably 5 to 50 parts by weight, per 100 parts by weight of calcium haloaluminate.

When the proportion of the easily soluble inorganic sulfate exceeds 100 parts by weight, the action of the sulfate to promote cement water utilization becomes stronger.

In order to delay the setting of cement for a certain period of time, it is not preferable to add a large amount of calcium haloaluminate.

Calcium haloaluminate or easily soluble inorganic sulfate is used in powder form, and although the degree of powder is not limited in the present invention, it is sufficient to use the same level as that of ordinary cement, about 3000 crtt/g. .

The amount of the cement retarder of the present invention to be added is a maximum of 0.1 to 5% by weight relative to the cement, and within this range, as the amount added increases, only the setting time of the cement increases, and the hardening properties do not change. No effect at all.

In other words, if the amount of the cement retarder of the present invention added is less than 0.1 times the maximum amount of cement, the retardation effect will be small, and if it exceeds 5 times the maximum amount, the cement will set rapidly and the setting delay time of the cement will be abnormal. It will take 3 to 7 days to harden.

The cement is normal, early strength, super early strength, medium heat, white Portland cement, or Portland cement mixed with silica and fly matshu.
Modified rapid hardening cements, expansive cements, and high sulfate slag cements containing large amounts of gypsum are not suitable.

As explained above, the present invention is a cement retarder for preventing cold joints containing calcium haloaluminate used in the cement pouring method, and by blending a small amount of the product of the present invention into cement,
It is an epoch-making cement retarder that can delay the setting time of cement, but does not change the hardening speed, and can prevent cracking at the joints of cone concrete, etc.

The present invention will be explained in more detail with reference to Examples below.

Example 1 3CaO・3A1203・C having the chemical composition shown in Table 1
a Crystallized and amorphous products of F 2 and 11CaO・7A1203・CaF2 were added as cement retarders to ordinary Portland cement by weight of 0 to 5. Obtained by mixing 40 parts by weight of water with 100 parts by weight of this cement. The heat generation pattern of cement paste was measured.

The results are shown in Figures 1 and 2. Note that A in Figure 1 is 3C.
The crystallized product of aO・3A1203・CaF2, B is the case when its amorphous product is used, and A in Figure 2 is the case where 11CaO is used.
・7A1203・CaF2 crystallized product, B is the result when its amorphous product was used.

Curve numbers 1 to 7 in the figure are 0 (curve 1), 0.1 (curve 2), 0.5 (curve 3), 1. 0
(Curve 4), 2.0 (Curve 5), 4.0 (Curve 6), 5
．． 0 (curve 7).

As shown in Figures 1 and 2, when comparing the heat generation patterns of curve numbers 2 to 7 with the addition of calcium haloaluminate and the heat generation pattern of curve number 1 without the addition, there is almost no difference, except for the start time of heat generation. It can be seen that only the amount of calcium haloaluminate is delayed depending on the amount of calcium haloaluminate added.

In addition, when the amount of calcium haloaluminate added to cement exceeds 5% by weight by internal cutting, it took 3 to 7 days for the cement to harden.

Example 2 A mixture of 80 parts by weight of a crystalline form of 3CaO・3A1203・CaF2 and 20 parts by weight of easily soluble inorganic sulfate as a reagent was added to cement in various proportions as a cement retarder.
The heat generation pattern was measured in the same manner as in Example 1.

Using CaSO4.2H20 as easily soluble inorganic sulfate
FIG. 3 shows the results using CaSO4.IH20, FIG. 4 shows the results using CaSO4, FIG. 5 shows the results using CaSO4, and FIG. 6 shows the results using MgSO4.

Note that the curve numbers in the figure are the same as in Example 1, and curve number 8 is the case where 3% by weight of cement was added by internal cutting.

As shown in Figures 3 to 6, the addition of easily soluble inorganic sulfate helps to retard the setting of cement when the cement retarder has a low content, and accelerates it when the content is high. In either case, it can be seen that the heat generation pattern is unchanged compared to the case where no cement retarder was added (curve 1).

In addition, in this example, if the amount of cement retarder added exceeds 5% by weight of the cement by internal cutting, the setting time of the cement will be significantly delayed, and no matter what kind of inorganic sulfate is used, Unable to recover from this
It took more than three days for the cement to harden.

In addition, in this example, 3Ca0・3A1203・
Similar experiments were conducted using other calcium haloaluminates in place of the CaF2 crystallized product, and the results were not significantly different.

Example 3 Crystallized product of 3CaO'3A7203'CaF2 and Ca
The heat generation pattern was measured in the same manner as in Example 1, except that an equal weight mixture of S04'I and H20 was used as the cement retarder.

The results are shown in FIG. The curve numbers in the figure are the same as in Example 1, and curve numbers 9 and 10 are for cases where 6% by weight and 100% by weight, respectively, were added to cement by internal cutting.

As shown in Figure 7, 3Ca0, 3A1203, CaF
It can be seen that the cement setting retardation effect of No. 2 is suppressed.

This tendency was the same in combinations of other calcium haloaluminates and easily soluble inorganic sulfates.

Therefore, if the blending ratio of the easily soluble inorganic sulfate to the calcium haloaluminate exceeds an equal weight, it is not preferable because a large amount of the calcium haloaluminate will be added.

Example 4 A mixture consisting of 80 parts by weight of crystallized 3Ca0, 3A1203, CaF2 and 20 parts by weight of CaSO4, Hao H2O was added as a cement retarder by 0 to 5% by weight to Shichimen [. A cement mortar obtained by mixing 100 parts by weight of standard sand, 150 parts by weight of standard sand, and 40 parts by weight of water was mixed in a mixed manner according to the results shown in Fig. 4 so that the heat generation start time of the placed mortar was about the same. Cement retarders were placed at intervals of 0.1 cm at intervals of 40 cIrL on a 10X 10X240 (cm) formwork by varying the setting time.
The mortar containing 2.3.4.5 (maximum weight) was poured and cured indoors at 20°C and RH 80% or higher.

In order to measure the bending strength at each splicing part, a 1 0 x 10
It was cut into specimens of x40 (crrL), and the bending strength was measured when the material was 3 days old.

The results are shown in Table 2.

Note that no cracks were found in any of the joints.

In addition, other calcium haloaluminates are used instead of 3Ca0, 3A1203, and CaF2, and CaSO4,! 4
A similar test was conducted using another easily soluble inorganic sulfate instead of H20, but the results were not much different.

[Brief explanation of the drawing]

FIGS. 1 to 7 are diagrams showing the relationship between the material age and the heat generation temperature of the cement paste when adding the cement retarder of the present invention. The correspondence between the curve number in the figure and the amount of cement retarder added is as follows.

Claims (1)

[Claims] 13Ca0, 3A1203, CaF2 and/or 11C
Cement retarder for preventing cold joints containing a crystallized product of a0.7A1203.CaF2 and/or powder of an amorphous compound having the same chemical composition as these crystallized products.-8 23Ca()3A1203.CaF2 and/or or 11C
Contains easily soluble inorganic sulfate in a proportion of 100 parts by weight or less per 100 parts by weight of powder of a0/7A1203/CaF2 crystallized product and/or amorphous compound having the same chemical composition as these crystallized products Cement retarder for cold joint prevention-8