JPS5915106B2 - cement retarder - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a cement paste tarder, particularly to a cement paste tarder for preventing cold joints.

Conventionally, when constructing a structure by folding the concrete to be poured into the concrete to be poured, the setting and hardening time of the concrete differs depending on the time difference between pouring the concrete, so it is difficult to The amount of heat of hydration 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 invention solves this drawback and provides a cement retarder for the purpose of preventing cold joints.

The present invention is characterized in that the inorganic sulfate is contained in a ratio of 50 to 500 parts by weight per 100 parts by weight of the water-soluble inorganic fluoride.

Conventionally, water-soluble inorganic fluoride, which is a component of the present invention, has been known as a cement retarder, but even when used alone, it is difficult to control the setting time, and the setting delay time is long. As the temperature increases, curing is also delayed, making it unsuitable for preventing cold joints.

The present invention uses a water-soluble inorganic fluoride and an inorganic sulfate in combination to solve the drawbacks of using an inorganic fluoride alone.

In the present invention, the blending ratio of both is particularly important.
50 parts by weight of inorganic sulfate per 100 parts by weight of water-soluble inorganic fluoride
~500 parts by weight, preferably 100-300 parts by weight.

If the proportion of inorganic sulfate is less than 50 parts by weight, the above-mentioned disadvantages of using inorganic fluoride alone cannot be solved;
If the amount exceeds 0 parts by weight, the water utilization promotion effect of the inorganic sulfate becomes significant, and in either case, the object of the present invention cannot be achieved.

In addition, the ratio of the above water-soluble inorganic fluoride and inorganic sulfate is:
All values are on an anhydride basis.

In the present invention, water-soluble inorganic fluoride is an inorganic fluoride that easily dissolves in water, and specific compounds include N
a2SiF6, M g S t F a, NaF.

KF, LiF, He1SiF6, BaSiF6, AlF3
, K 2 S t F a, H2SiF6, Fe5tF
6, CaS iF6, A12(SiF6)3, etc.

In addition, as an inorganic sulfate, Ca S 04 ・2 H2
0, Ca5O4H'lH2O, ■ type Ca5O,, MgS
Among them, MgSO4 is the most preferred inorganic sulfate.

The amount of the product of the present invention added to cement is 0.01 in external cutting.
It is preferably about 2% by weight, and if the amount added is less than 0.011 parts by weight, the effect will be small, and there is no advantage to adding more than 2 parts by weight.

Target cements include normal, early strength, super early strength, medium heat, and white Portland cement, silica cement, fly ash cement, and blast furnace cement, as well as alumina cement, calcium aluminate, or calcium haloaluminate. Rapid hardening cement containing a large amount has little effect.

As explained above, the present invention is a cement retarder for preventing cold joints containing a water-soluble inorganic fluoride and an inorganic sulfate for use in cement pouring method. By adding a small amount to the cement, the setting time of cement can be delayed, but the curing speed remains unchanged, making it an innovative seven-layer l-IJ tarder that can prevent cracking at joints in concrete, etc.

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

The cement used in the following examples is ordinary Portland cement, and the relationship between the curve numbers in FIGS. 1 to 9 and the amount of cement retarder added is as shown in Table 1.

Example 1 A cement retarder obtained by mixing first class reagents Na2SiF6 and MgSO4 in the ratio shown in Table 2 was added to cement to make a cement paste with a water-cement ratio of 49%, and the heat generation pattern of this was measured. did.

The results are shown in FIG. 1, A to D. Example 2 100 parts by weight of inorganic fluoride shown in Table 3 and Mg8042
The heat generation pattern of the cement paste was measured in the same manner as in Example 1, except that a cement retarder consisting of 0.00 parts by weight was used.

The results are shown in Figures 2-9.

As is clear from Figures 1 to 9, by blending an appropriate amount of inorganic sulfate with water-soluble inorganic fluoride, the disadvantages of conventional use of inorganic fluoride alone can be solved and the setting time can be easily adjusted. Moreover, it can be seen that it is an ideal cement retarder that does not change the curing speed, that is, the heat generation pattern is completely the same as when no additive is used.

Example 3 A cement retarder consisting of 100 parts by weight of Na2SiF6 and 200 parts by weight of Mg5O was added to the cement by external cutting at a maximum of 0 to 1.0 parts, and the weight ratio of cement to standard sand was 1.
．． 5. Prepare mortar with a water-cement ratio of 40%, and change the kneading and casting time so that the heat generation start time of the placed mortar is about the same according to the results shown in Figure 1C.
0X240 (crfL) formwork with cement retarders at intervals of 40 cm 1.0.0.5.0.25.0.
15.0.08 and O (maximum amount) was poured into the mortar 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
A specimen of x40 (CrrL) was cut, and the bending strength was measured after 3 days.

The results are shown in Table 4.

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

Further, even when other water-soluble inorganic fluorides were used in place of Na2SiF6, results similar to those in this example were obtained.

[Brief explanation of the drawing]

1 to 9 are diagrams showing the relationship between the material age and the heat generation temperature of the cement paste in the case of cement retarder addition. The correspondence between the curve number in the figure and the amount of cement retarder added is as follows.

Claims (1)

[Claims] 1. A cement paste tarder containing 50 to 500 parts by weight of an inorganic sulfate to 100 parts by weight of a water-soluble inorganic fluoride.