KR102307019B1 - Hydration heat reducer with improved durability and usability - Google Patents

Abstract

The present invention relates to a hydration heat reducing material composed of strontium hydroxide octahydrate (Sr(OH)_2·8H_2O), a hydration heat reducing aid comprising silicon oxide (SiO_2), calcium hydroxide (Ca(OH)_2), and aluminum oxide (Al_2O_3), and a hardening accelerator. The hydration heat reducing material of the present invention has high initial strength and less initial deformation in the process of concreate construction compared to conventional hydration heat reducing materials, thereby improving workability.

Description

Hydration heat reducing material with improved durability and workability.{HYDRATION HEAT REDUCER WITH IMPROVED DURABILITY AND USABILITY}

The present invention relates to a heat of hydration reducing material with improved durability and workability, and more particularly, to a heat of hydration reducing material with improved durability and workability compared to a conventional heat of hydration reducing material by containing a heat of hydration reducing aid and a curing accelerator.

Cement generates 120cal of heat per 1g in the hydration process, and since the concrete constructed using the cement has a relatively low thermal conductivity, it takes a considerable amount of time for the heat of hydration generated through a chemical reaction during the curing process to escape to the outside of the member.

Among concrete structures, in the case of structures with large cross-sectional areas such as mat foundations and dams of high-rise structures, the internal temperature rises due to the low thermal conductivity of the concrete, and the tensile force is caused by the internal/external temperature difference (usually 25℃) due to heat dissipation. will receive When this tensile force is greater than the allowable tensile strength of concrete, temperature cracks occur, and temperature cracks are the main cause of lowering the strength, waterproofness, and durability of the structure. necessary.

In addition, pouring concrete in the summer in an environment with a large daily temperature difference due to seasonal change can increase the probability of cracking in mass concrete. Therefore, the Korean National Construction Standards Center defines the concrete poured in an environment where the average daily temperature exceeds 25℃, and defines the concrete pouring temperature as low-temperature concrete not to exceed 35℃.

In general, methods for reducing cracks in concrete can be divided into design/structural aspects, material aspects, and construction aspects. Among the design and structural aspects, representative construction methods include thermal reinforcement and the installation of crack-inducing joints. However, in the case of thermal reinforcement, the construction is complicated. There are concerns. In terms of construction, the pipe cooling method and split casting are representative, but they have the disadvantages of complicated construction procedures and increased time. On the other hand, in terms of material, various studies are being conducted, such as adjustment of water binder ratio, mixing of super retardant materials, substitution of admixture materials, and mixing of low-heat binders. have. However, in the case of existing methods for reducing heat of hydration, problems such as increase in cost and delay in strength development have been raised. Research is ongoing.

Recently, the application of mass concrete is increasing due to the enlargement and lengthening of concrete structures. In particular, when mass concrete is poured in a mid-weeping environment, the temperature of the material rises due to the high temperature of the outside air, and the temperature of the concrete increases during pouring, which increases the probability of cracking. Therefore, as a countermeasure against temperature cracking of mass concrete, research on various heat-of-hydration reduction technologies is being conducted. As part of this study, it is reported that inorganic hydration heat reducing materials, which are phase transition materials, can exert a phase change in an environment where the hydration temperature of concrete rises due to the heat of hydration of cement, thereby controlling the hydration temperature of concrete and suppressing temperature stress.

The applicant has developed and applied a composition that can significantly reduce the heat of hydration through an inorganic heat-of-hydration reducing material.

For example, in Korean Patent Publication Nos. 10-0766803 and 10-0796534, the effect of reducing the heat of hydration is expressed through a composition in which a nitrate-based, chloride-based, and phosphate-based mixed compound is added to a silica-based diluted solution. At this time, the mixed compound is calcium nitrate tetrahydrate (Ca(NO ₃ ) ₂ ·4H ₂ O), zinc nitrate hexahydrate (Zn(NO ₃ ) ₂ ·6H ₂ O), lithium nitrate trihydrate (LiNO ₃ ·3H _{2 )} O), a nitrate-based compound composed of any one or a mixture thereof, a chloride-based compound composed of calcium chloride hexahydrate (CaCl ₂ .6H ₂ O), and a phosphate composed of disodium hydrogen phosphate dodecahydrate (Na ₂ HPO ₄ .12H ₂ O) As a system compound, it consists of an inorganic hydrate.

In addition, Korean Patent Publication No. 10-0802988 contains strontium hydroxide octahydrate (Sr(OH) ₂ ·8H ₂ O) to reduce heat generation in concrete, and Korean Patent Publication No. 10-1618682 discloses strontium hydroxide octahydrate Contains hydrates such as (Sr(OH) ₂ .8H ₂ O), zinc nitrate hexahydrate (Zn(NO ₃ ) ₂ .6H ₂ O), and aluminum nitrate hexahydrate (Al(NO ₃ ) ₂ .9H _{2 O)} By doing so, the heat generation of the concrete is reduced.

In addition, Korean Patent No. 10-1882896 discloses a technology for maintaining the crystal structure of a hydrate of a latent heat compound exhibiting an effect of reducing the heat of hydration by mixing a stabilizing agent. Through the mixing of such a stabilizing agent, the effect of improving long-term storage is obtained, thereby improving the construction efficiency.

However, if the heat of hydration of concrete is lowered by the mixing of the heat of hydration reducing material, the initial strength also decreases. has no problem.

Republic of Korea Patent Publication No. 10-0766803 Republic of Korea Patent Publication No. 10-0796534 Republic of Korea Patent Publication No. 10-0802988 Republic of Korea Patent Publication No. 10-1618682 Republic of Korea Patent Publication No. 10-1882896

The present invention has been devised to solve the problems of the prior art as described above, and by adding a heat of hydration reducing agent and a hardening accelerator to the composition of a heat of hydration reducing material with excellent long-term storage properties in an appropriate range, the initial strength at the time of concrete construction is high, so that the concrete An object of the present invention is to provide a hydration heat reducing material with improved durability and improved workability.

In addition, an object of the present invention is to provide a heat of hydration reducing material that can improve the physical properties of concrete while maintaining the heat of hydration reducing performance of the heat of hydration reducing material by using the optimized heat of hydration reducing agent.

The heat of hydration reducing material of the present invention for achieving the above object consists of strontium hydroxide octahydrate (Sr(OH) ₂ ·8H ₂ O), a heat of hydration reducing agent and a curing accelerator, and the heat of hydration reducing agent is silicon oxide (SiO ₂ ), calcium hydroxide (Ca(OH) ₂ ), aluminum oxide (Al ₂ O ₃ ), and the curing accelerator includes anhydrite, hemihydrate gypsum, aluminum hydroxide (Al(OH) ₃ ), calcium aluminate, and calcium sulfo. It is characterized in that it is any one of aluminates.

In this case, the heat of hydration reducing material is preferably composed of 60 to 70 parts by weight of strontium hydroxide octahydrate, 20 to 30 parts by weight of a heat of hydration reducing agent, and 10 to 20 parts by weight of a curing accelerator.

In addition, the hydration heat reducing aid may be made of calcium silicate hydrate and calcium aluminate hydrate prepared through a pozzolan reaction of silicon oxide, calcium hydroxide, and aluminum oxide, wherein the calcium silicate hydrate and calcium aluminate hydrate are 6: It is preferable to mix in a weight ratio of 1 to 10:1.

The heat of hydration reducing material of the present invention has a high initial strength during concrete construction by adding a heat of hydration reducing agent and a curing accelerator to the composition of a conventional heat of hydration reducing material with excellent long-term storage properties in an appropriate range, thereby improving the durability of concrete and improving workability indicates

In addition, it shows the effect of improving the physical properties of concrete while maintaining the heat of hydration reduction performance of the heat of hydration reducing material by using the optimized heat of hydration reducing agent.

1 is a DSC/TGA analysis result for the hydration heat reducing material preliminary sample 1 (a), preliminary sample 2 (b), preliminary sample 3 (c) and preliminary sample 4 (d).
Figure 2 is a graph measuring the change in the moisture content before and after the deliquescence resistance evaluation for the heat of hydration reducing material samples 1 to 12.
3 is a result of measuring the simple insulation temperature increase of the hydration heat reducing material.
4 is a result of evaluating the compressive strength of the concrete containing the hydration heat reducing material.

Hereinafter, the present invention will be described in more detail. The terms or words used in the present specification and claims should not be construed as being limited to their ordinary or dictionary meanings, and the inventor may properly define the concept of the term in order to best describe his invention. It should be interpreted as meaning and concept consistent with the technical idea of the present invention based on the principle that there is.

The heat of hydration reducing material according to the present invention is used to reduce the heat of hydration generated while cement and water react during concrete construction by being contained in the composition for concrete construction.

As for the heat of hydration reducing material, various hydrates are applied as latent heat compounds in the prior art, but the heat of hydration reducing material of the present invention _{uses strontium hydroxide octahydrate (Sr(OH) 2} ·8H ₂ O) as a latent heat compound, and silicon oxide (SiO ₂ ), calcium hydroxide (Ca(OH) ₂ ), aluminum oxide (Al ₂ O ₃ ) It is characterized in that it contains a heat-reducing aid and curing accelerator containing aluminum oxide (Al 2 O 3 ).

In general, latent heat compounds are hydrates, so in the case of long-term storage, it is unavoidable to cause agglomeration of particles due to a change in moisture content despite the container being sealed. In addition, the moisture content of the latent heat compound may increase as moisture contained in the outside air is absorbed in addition to the crystal water constituting the hydrate. In addition, in the case of long-term storage, the moisture content of the hydrate itself tends to decrease as the moisture content is lowered according to changes in the external environment such as temperature and humidity.

In addition, when concrete is constructed with a composition mixed with a heat-of-hydration reducing material, the heat of hydration is lowered during the curing process of the concrete, and the initial strength tends to be lowered. Of course, the strength is recovered by curing the concrete for a long time, but the low initial strength leads to a decrease in workability, so it needs to be improved.

In the present invention, strontium hydroxide octahydrate (Sr(OH) ₂ .8H ₂ O) is used as the latent heat compound. When thermogravimetric analysis of the strontium hydroxide octahydrate is performed, the moisture content gradually decreases, and the moisture content decreases after storage for 30 days. It was found to be reduced by 10%, and in this case, the effect of reducing the heat of hydration of the concrete composition was significantly reduced.

The heat of hydration reducing material according to the prior art Korean Patent No. 10-0766803 is prepared by mixing such a latent heat compound with a silica-based dilution solution, and in Korean Patent No. 10-1882896, a latent heat compound and a stabilizing aid (the present invention) Long-term storage is improved by applying a heat-of-hydration reducing material made of (corresponding to hydration heat reducing aid).

The sleep strontium zeal as hydroxide hydrate is a compound octahydrate _{(Sr (OH) 2 · 8H} 2 O), barium hydroxide octahydrate _{(Ba (OH) 2 · 8H} 2 O) any one of, or a mixture thereof, the nitrate-based hydrate As calcium nitrate tetrahydrate (Ca(NO ₃ ) ₂ ·4H ₂ O), zinc nitrate hexahydrate (Zn(NO ₃ ) ₂ ·6H ₂ O), lithium nitrate trihydrate (LiNO ₃ ·3H ₂ O), aluminum nitrate Any of 9 hydrate (Al(NO ₃ ) ₂ ·9H ₂ O), magnesium nitrate hexahydrate (Mg(NO ₃ ) ₂ ·6H ₂ O), or iron nitrate hexahydrate (Fe(NO ₃ ) ₂ ·6H ₂ O) One or a mixture thereof, calcium chloride hexahydrate (CaCl ₂ ·6H ₂ O) as the chloride-based hydrate, and disodium hydrogen phosphate dodecahydrate (Na ₂ HPO ₄ ·12H ₂ O) as the phosphate-based hydrate may be used. In addition, 1 type may be used for a hydrate, and 2 or more types may be mixed and used for it. However, among the known latent heat compounds, strontium octahydrate is used in the present invention, and strontium octahydrate has the most excellent compatibility with the heat of hydration reducing aid and anhydrite according to the present invention among candidates for various latent heat compounds. .

In addition, the hydration heat reducing aid includes silicon oxide (SiO ₂ ), calcium hydroxide (Ca(OH) ₂ ), aluminum oxide (Al ₂ O ₃ ) When used with the latent heat compound, the surface of the latent heat compound to improve the structural stability of the hydrate.

This hydration heat reducing aid consists of a component similar to the stabilizing aid disclosed in Korean Patent No. 10-1882896. However, according to the composition of the heat of hydration reducing material of the present invention, silicon oxide, calcium hydroxide, and aluminum oxide are made of calcium silicate hydrate and calcium aluminate hydrate prepared through a pozzolan reaction, so that it is effective to use as a heat of hydration reducing aid.

The pozzolan reaction is a general reaction to form pozzolans, and the pozzolans include natural pozzolans such as tuff and diatomaceous earth, and artificial pozzolans such as calcined clay, silica gel, silica fume, and fly ash. These pozzolans include silicon, calcium, aluminum It is made up of elements such as That is, soluble components such as silicon oxide and aluminum oxide eluted from the pozzolan material are hydrated by components such as trilime silicate and dilime silicate that make up cement, and calcium hydroxide produced slowly reacts with insoluble calcium silicate hydrate or calcium aluminate hydrate. forming a more dense crystalline structure.

The hydration heat reducing aid obtained through this reaction is adsorbed on the surface of strontium hydroxide octahydrate, which is a latent heat compound, and thus exhibits a function of protecting the hydrate so that the crystal structure of _{the hydrate (H 2 O) is stably maintained.} At this time, it was found that long-term stability of the hydrate could not be sufficiently secured if it was outside the optimal range depending on the ratio of the calcium silicate hydrate and the calcium aluminate hydrate constituting the heat of hydration reducing aid, and experimentally 6:1 to 10: It was found that the stability of the latent heat compound can be most effectively maintained in a mixed state at a weight ratio of 1.

In addition, in the present invention, anhydrite is used as a component of the hydration heat reducing material. The anhydrite had a density of 2.92 g/cm 3 , and as a result of component analysis, SiO ₂ 1.54 wt%, Al ₂ O ₃ 0.36 wt%, Fe ₂ O ₃ 0.21 wt%, CaO 37.6 wt%, MgO 0.05 wt%, It was found to consist of 58.6% by weight of SO3 and other components. It was found that when such anhydrite is contained, the effect of improving the initial strength can be obtained in the construction process of concrete mixed with a heat-reducing material for hydration.

In addition, it was found that the heat of hydration reducing material preferably consists of 60 to 70 parts by weight of strontium hydroxide octahydrate, 20 to 30 parts by weight of a heat of hydration reducing agent, and 10 to 20 parts by weight of a curing accelerator. By adjusting the content of the heat of hydration reducing agent and the curing accelerator to the above ranges, it was found that it was possible to suppress the decrease in the initial strength of concrete due to the reduction of the heat of hydration while maintaining the heat of hydration reduction effect of the heat of hydration reducing material.

As the curing accelerator, any one of anhydrite, hemihydrate gypsum, aluminum hydroxide (Al(OH) ₃ ), calcium aluminate, and calcium sulfoaluminate may be selected and used. The components are generally added as curing accelerators or expanding agents to the concrete composition, and it was found that by mixing with the hydration heat reducing material, they exhibit an effect of improving the initial strength of the concrete composition including the hydration heat reducing material.

In addition, when the hydration heat reducing material is applied to the concrete composition, it was found that it is good to contain 0.5 to 10% by weight, preferably 1 to 5% by weight, based on the total weight of the composition. If the amount of the heat of hydration reducing material is too small, it is difficult to expect a sufficient effect of reducing the heat of hydration of concrete, so the problem caused by the generation of heat of hydration during conventional concrete construction is not solved. It was found to be inefficient in terms of economy compared to the heat of hydration reduction performance of concrete.

In addition, the hydration heat reducing material of the present invention may be used by applying to the low heat generating binder composition. In this case, 0.5 to 10 wt% of the heat of hydration reducing material is added to 100 wt% of the three-component binder including cement, preferably type 1 ordinary Portland cement, blast furnace slag fine powder, and fly ash, by a premixing process. It can be produced by input. In this case, the binder is preferably a three-component binder, but may be used alone, or a two-component binder of cement and blast furnace slag fine powder, cement and fly ash. That is, the low-heat binder may consist of one to three components, and it is preferable to include 0.5 to 10 wt% of the heat of hydration reducing material with respect to 100 wt% of the binder. This is because when the content of the heat of hydration reducing material is too small, the effect of reducing the heat of hydration cannot be obtained, and even if it is too large, the effect of reducing the heat of hydration is rather reduced, and economical efficiency is lowered by using a large amount of the expensive heat of hydration reducing material. Also, in any case, since the heat of hydration generated during concrete formation is suppressed by the added heat of hydration reducing material, it is possible to manufacture high-quality concrete.

Hereinafter, the present invention will be described in more detail through the description of preferred embodiments of the present invention. However, the following examples are merely examples to help the understanding of the present invention, thereby the scope of the present invention should not be reduced or limited.

[Evaluation of hydration heat reducing materials]

As shown in Table 1, a heat-reducing material for hydration was prepared. The hydration heat reducing material was prepared by mixing an appropriate amount of silicon oxide, calcium hydroxide, and aluminum oxide followed by a pozzolan reaction, and as a result of XRF and XRD analysis, the weight ratio of calcium silicate hydrate and calcium aluminate hydrate was estimated to be 9 to 9.5:1. . In addition, for comparison, a heat-reducing material for hydration heat composed of a latent heat compound and a stabilizing aid according to Korean Patent No. 10-1882896 was prepared. In this experiment, strontium octahydrate was used as a latent heat compound, anhydrite was used as a curing accelerator, and CaO was used as a stabilizing agent. In addition, in Table 1, a unit is a weight part.

latent compounds Hydration heat reducing agent hardening accelerator stabilizing agent Preliminary sample 1 70 30 10 - Preliminary sample 2 80 20 10 - Preliminary sample 3 90 - - 10 Preliminary sample 4 100 - _- -

DSC/TGA analysis results for preliminary samples 1 to 4 are shown in FIG. 1 . In DSC/TGA analysis, the analysis was performed with a maximum temperature of 300°C and a temperature increase rate of 5°C/min.

Looking at the analysis results, a peak at 80 to 100°C and a peak at 130 to 150°C were observed for each of the preliminary samples 1 to 4. The peak at 80 to 100° C. appears to be the removal of moisture remaining on the surface, and the peak at 130 to 150° C. appears to be a peak appearing due to the loss of the hydrate of the latent heat compound.

Looking at the peak at 130 to 150 ° C, preliminary sample 1 has a peak at 140.5 to 148.8 ° C, preliminary sample 2 has a peak at 127.7 to 137.5 ° C, and preliminary sample 3 shows a peak at 144.7 to 145.6 ° C, Preliminary Sample 4 has a peak at 149.5 to 155.7°C.

In the case of Preliminary Sample 3, the narrowest and strongest peaks are observed, and it seems that the hydrates constituting the latent heat compound are largely lost at a specific temperature due to chemical bonding following the addition of the stabilizing agent.

Looking at the loss of hydrate according to the content of the hydration heat reducing aid and anhydrite in preliminary sample 1 and preliminary sample 2, in the case of preliminary sample 2, a relatively wide peak can be observed at 127.7 to 137.5 ° C, but the peak peak is 134.3 ° C. Compared with 146.3°C of 1, it showed a lower temperature, indicating that hydrate loss occurred at a relatively low temperature.

From these analysis results, it can be seen that the rate of hydrate loss in preliminary sample 1 is the slowest. This is the conclusion that can be drawn by comparing the width of the peak to the position of the peak.

Next, as shown in Table 2, a sample of a heat-reducing material for hydration was prepared and evaluated at the same time. In Table 2, the unit is parts by weight, and strontium octahydrate was used as the latent heat compound. Reduction aid 1 is CaO, reducing aid 2 is a heat of hydration reducing aid in which calcium silicate hydrate and calcium aluminate hydrate obtained through the pozzolan reaction are present in a weight ratio of 9:1 to 10:1, and reducing aid 3 is through a pozzolan reaction Heat of hydration reducing aid and reducing aid 4 in which the obtained calcium silicate hydrate and calcium aluminate hydrate are present in a weight ratio of 6:1 to 7:1, calcium silicate hydrate and calcium aluminate hydrate obtained through a pozzolan reaction are 3:1 to It is an auxiliary for reducing heat of hydration present in a weight ratio of 4:1.

latent heat compound Reduction Aid 1 Reduction aid 2 Reduction Aid 3 Reduction Aid 4 hardening accelerator sample 1 100 - - - - - sample 2 95 5 10 sample 3 90 10 10 sample 4 90 10 10 sample 5 90 10 10 sample 6 90 10 10 sample 7 80 20 10 sample 8 80 20 10 sample 9 80 20 10 sample 10 70 30 10 sample 11 70 30 10 sample 12 70 30 10

In order to evaluate the deliquescent properties of the prepared sample, the change with time of the sample left at room temperature was observed.

The state of the sample was observed for 5 weeks, and in Sample 1 (plain), agglomeration due to deliquescence occurred 7 days after preparation.

In addition, in the case of Sample 2 containing the reduction aid 1, agglomeration occurred from 14 days after preparation, and the lump was relatively easily broken, but it was found that the size of the lump increased as the elapsed days increased. In addition, sample 3 did not show agglomeration until 35 days after preparation.

In addition, in the case of sample 4 containing the reduction aid 2, agglomeration occurred from 28 days after preparation, but the size of the agglomeration did not increase and showed a tendency to break easily. In addition, in the case of Sample 7, agglomeration was not observed until 35 days after preparation. In addition, in the case of sample 10, agglomeration was not observed until 35 days after preparation.

In addition, in the case of sample 5 containing the reducing aid 3, agglomeration occurred 7 days after preparation, and it was found that the stiffness of the lump increased as time passed. In addition, in the case of Sample 8, the same trend as in Sample 5 was confirmed, and the mass size and stiffness were also increased compared to Sample 5. In addition, in the case of sample 11, the same trend as in sample 5 was confirmed, and it was found that the lump size and stiffness were increased compared to sample 5.

In addition, in the case of sample 6 containing the reduction aid 4, agglomeration occurred 7 days after preparation, and the lump was easily broken, but it was found that the size increased as time passed. In addition, in the case of sample 9, the same trend as that of sample 6 was confirmed, and the lump size and stiffness were slightly increased compared to sample 6. In addition, in the case of Sample 12, the same trend as in Sample 6 was confirmed, and the lump size and stiffness were also slightly increased compared to Sample 6.

Therefore, it was confirmed that the deliquescent properties were improved when the reducing aid was included compared to Sample 1 not containing the reducing aid.

Because the heat of hydration reducing material easily agglomerates and is often agglomerated by the addition of a stabilizing agent, to exclude the agglomeration effect, we tried to observe the change after grinding the sample 1 week after preparation using a blender. In addition, when the prepared sample was stored, the entrance part was sealed with a plastic container and high-performance tape, and deliquescent resistance over time was evaluated.

As a result of observation for 4 weeks, in the case of sample 1 (plain), it was confirmed that agglomeration due to deliquescence occurred from 1 week after pulverization. After that, only small lumps were maintained, and no major changes were observed.

In addition, in the case of samples 2 and 3 containing the abatement aid 1 and samples 4, 7, and 10 containing the abatement aid 2, agglomeration was not observed until 28 days after pulverization.

In addition, in the case of sample 5 containing the reducing aid 3, agglomeration occurred 7 days after grinding, and it was found that the size of the agglomerate increased as time passed. In addition, in the case of samples 8 and 11, the same trend as in sample 5 was confirmed, but the lump size was decreased.

In addition, in the case of sample 6 containing the reducing aid 4, a little agglomeration occurred from one week after preparation, but the lump was not large and the size of the lump did not increase even with the passage of time. In addition, in the case of samples 9 and 12, the same trend as that of sample 6 was confirmed, and the lump size showed a tendency to decrease.

In addition, the quality was evaluated by measuring the moisture content of the manufactured heat-of-hydration reducing material. The latent heat compound contained in the hydration heat reducing material of the present invention is a phase change material, and when the phase change material is heated, it absorbs heat and releases heat again when the heat is reduced to the previous level, causing a phase transition. Since the release and absorption of water occurs in the process of changing the phase of the phase change material, the homogeneous water content of the phase change material has a very important effect on the quality as an inorganic heat of hydration reducing material.

The moisture content was measured using a moisture meter XC63 (CAS corp.), and the set temperature was set to 120°C.

As a result of collecting and analyzing 1 g of each sample (Samples 2 to 12), the minimum value of the moisture content in the entire phase change material sample was 50.94% and the maximum value was 56.89%. Therefore, the average value of moisture content for the heat-of-hydration reducing material of the present invention was calculated as 53.44%, and the moisture content error rate was 1.39%, confirming that the basic phase change material properly retains homogeneous quality.

In addition, the moisture content after deliquescence resistance evaluation of the samples was measured, and this was used as an index for evaluating long-term storage properties. The results of measuring the decreasing tendency of the moisture content are shown in FIG. 2 . Looking at the results of FIG. 2 , as the content of the heat of hydration reducing aid increased, the amount of moisture loss tended to decrease. Also, it was found that there was a difference in the amount of moisture reduction according to the combination of the hydration heat reducing aid.

Based on the experimental results as described above, the concrete heat of hydration reduction performance when using the heat of hydration reducing material of the present invention was evaluated.

[Performance evaluation of cement and concrete containing hydration heat reducing material]

Sample 1, Sample 3, Sample 7, and Sample 10 were selected from the results of evaluating long-term storage properties, and performance evaluation was performed. Sample 1 is a conventional heat-of-hydration reducing agent composed only of a latent heat compound, Sample 3 contains the reducing aid 1, and samples 7 and 10 contain the reducing aid 2.

Performance evaluation was conducted through the amount of simple insulation temperature rise and compressive strength. The amount of simple insulation temperature rise was evaluated using cement paste, and the compressive strength was evaluated by manufacturing concrete. Table 3 shows the composition of cement paste and concrete. In addition, in both cement paste and concrete, the mixing amount of the heat of hydration reducing material was set to 5% by weight of the binder.

W/B S/a unit weight(kg/㎥) HR (wt%) W C S G cement paste 45.1 - 600 1,330 - - 5 concrete 47 43.3 185 394 717 992 5

As a result of evaluating the increase in the simple insulation temperature of the hydration heat reducing material, the highest temperature decrease rate compared to OPC was found to be high in the order of Sample 3 > Sample 10 > Sample 1 > Sample 7. In addition, the time to reach the maximum temperature compared to OPC was delayed in the order of Sample 3 > Sample 10 > Sample 1 > Sample 7. In addition, when the heat of hydration reducing material was mixed, it was found that the maximum temperature of the heat of hydration was reduced by 6.7 to 13.1°C compared to OPC. In addition, the time to reach the maximum temperature was delayed from 1 hour to 2 hours 30 minutes compared to OPC. This result can be confirmed from the measurement result of the simple insulation temperature increase in FIG. 3 . Looking at the results of FIG. 3 , in the case of OPC, it was found to reach the maximum temperature of 68.6° C. in 13 hours and 10 minutes, Sample 1 reached the maximum temperature of 56.9° C. in 15 hours and 10 minutes, and Sample 3 reached 61.9° C. 14 hours and 10 minutes were reached, sample 8 reached 15 hours and 40 minutes to 55.5 °C, and sample 10 reached 59.3 °C in 14 hours and 10 minutes. That is, samples 8 and 10 had the same maximum temperature as sample 1, which is a conventional heat of hydration reducing agent, and thus it was evaluated that the effect of reducing the heat of hydration was excellent. In addition, sample 10 showed the fastest time to reach the maximum temperature, which was evaluated to have a better effect on initial strength expression.

In addition, the effect on compressive strength by mixing the heat of hydration reducing material into concrete was evaluated. The result is shown in FIG. 4 .

Referring to the results of FIG. 4 , in the case of 7-day age compressive strength, samples other than sample 10 showed lower compressive strength compared to OPC, confirming that sample 10 had the best initial compressive strength. In addition, in the case of 28-day and 56-day compressive strength, samples 7 and 10 showed higher compressive strength than OPC, and Hyper-HR and sample 3 showed lower compressive strength than OPC.

From these results, in the case of Sample 10, the initial compressive strength was the highest and the simple insulation temperature increase was slightly lower than that of Sample 3, but the effect of reducing the heat of hydration was evaluated as showing sufficient performance compared to the existing heat of hydration reducing material. This is evaluated as the effect that appears due to the use of anhydrite and components and content of the heat of hydration reducing aid included in the heat of hydration reducing material. Therefore, when the heat of hydration reducing material according to the present invention is applied, it was evaluated that it can exhibit the same degree of long-term storage and heat of hydration reduction performance as the conventional heat of hydration reducing material while increasing the initial compressive strength of concrete.

Although the present invention has been described with reference to preferred embodiments as described above, it is not limited to the above embodiments and various modifications are made by those skilled in the art within the scope of not departing from the spirit of the present invention. and can be changed Such modifications and variations are intended to fall within the scope of the present invention and the appended claims.

Claims (3)

It consists of strontium hydroxide octahydrate (Sr(OH) ₂ ·8H ₂ O), a heat of hydration reducing agent, and a curing accelerator.
The hydration heat reducing aid includes silicon oxide (SiO ₂ ), calcium hydroxide (Ca(OH) ₂ ), aluminum oxide (Al ₂ O ₃ ),
The curing accelerator is any one of anhydrite, hemihydrate gypsum, aluminum hydroxide (Al(OH) ₃ ), calcium aluminate, and calcium sulfoaluminate,
The hydration heat reducing aid consists of calcium silicate hydrate and calcium aluminate hydrate prepared through a pozzolan reaction of _{silicon oxide (SiO 2} ), calcium hydroxide (Ca(OH) ₂ ), and aluminum oxide (Al ₂ O _{3 ),}
The hydration heat reducing material, characterized in that the calcium silicate hydrate and calcium aluminate hydrate are mixed in a weight ratio of 6:1 to 10:1.
The method according to claim 1,
The heat of hydration reducing material comprises 60 to 70 parts by weight of strontium hydroxide octahydrate, 20 to 30 parts by weight of a heat of hydration reducing agent, and 10 to 20 parts by weight of a curing accelerator.
delete

Images