KR20020082320A - Cement Admixture for high strength, shrinkage-reducing and cold-construction, and cement composite incorporating the admixture - Google Patents

Abstract

PURPOSE: Provided are a cement admixture with high strength, low shrinkage and low temperature application, and a cement composition with much improved initial strength, longtime strength and durability compared with portland cement by mixing cement with the prepared admixture. CONSTITUTION: The admixture comprises 75-100wt.% Al2(SO4)3 as a main material, 0-10wt.% of Na2CO3, 0-10wt.% of NaAlO2, 0-25wt.% of CaCl2, 0-15wt.% of limestone, and 0-5wt.% of magnesium fluosilicate, where the all materials have a specific surface area of 2000cm¬2/g or more, except limestone with a specific surface area of 5000cm¬2/g or more. Also, the cement admixture is prepared by adding 1-10wt.% of the prepared admixture to conventional cement such as portland cement, high early-strength portland cement, fly ash cement or blast furnace slag cement.

Description

Cement admixture for high strength, shrinkage reduction and low temperature construction and cement composition containing same {Cement Admixture for high strength, shrinkage-reducing and cold-construction, and cement composite incorporating the admixture}

The present invention relates to a cement admixture capable of high strength, non-shrinkage and low temperature construction, and a cement composition containing the same. By adding 1 ~ 10% of admixtures to ordinary portland cement, it is possible to improve the initial strength and long-term strength of ordinary portland cement significantly, and to reduce the shrinkage and low temperature construction, and to manufacture cement admixtures that can greatly improve durability. to be.

Since the admixture of the present invention improves the physical properties of mortar or concrete as described above, it is widely used for concrete products and general civil engineering and building structures.

Portland cement, which is currently commonly used, is a powder made by mixing a sufficient amount of raw materials mainly composed of silica, alumina, and lime in an appropriate ratio, and adding a portion of gypsum to a molten and sintered clinker, and the crude steel portland cement is 3CaO. , the content of SiO ₂ as ordinary portland cement manufactured of 3CaO · SiO ₂ content of about 8% to increase the specific surface area of usually at least about 1300㎠ / g than about 3300㎠ / g of portland cement than 54% of nopyieo, usually Since the 7-day strength of Portland Cement is expressed in 3 days, there is an advantage of improving mold turnover when applying secondary products as well as construction requiring air shortening. However, the production of crude steel cement has not been generalized due to the reduction of the production amount and the increase of cost due to the increase of the grinding time.

Therefore, if the crude cement can be prepared by adding admixtures to ordinary portland cement, it will be a revolutionary invention in cement manufacturing history. Based on this point, this research was carried out for 3 years of continuous research to invent the admixture, which was added to ordinary portant cement composition and examined for its physical properties. It is much superior to ordinary portland cement and is better than crude portland cement. Almost equivalent properties.

The initial strength of cement with the admixture prepared by the present invention is 1.4-1.6 times higher than that of ordinary portant cement, and the long-term strength is also very good, so that the mold rotation rate can be improved when applying secondary products as well as construction requiring air shortening. In particular, it can express high strength during steam curing. Therefore, it can also be expected to use a large amount of general purpose, that is, as a general purpose cement.

In addition, the cement according to the addition of a suitable amount of the admixture prepared by the present invention has excellent chemical resistance compared to the ordinary portland cement, which usually generates a large amount of Ca (OH) ₂ while hydrated tricalcium silicate or dibasic silicate lime in portland cement. Its presence plays a negative role in resistance to chemical erosion. However, when an appropriate amount of the admixture of the present invention is added, a large amount of hydrates are formed around ettlingite, which is a needle-shaped crystal form of several μm filling the capillary pores by hydration with Ca (OH) ₂ generated in the hydration reaction of ordinary portland cement. The pore-reducing action in the cement hardened body not only makes the hardened body compact but also partially reduces the amount of Ca (OH) _2, so it is excellent in resistance to various salts, in particular sulfate or seawater. Therefore, it can be used for marine structures, harbor construction, reclaimed land construction, urban substructures and factory wastewater, waste fires, etc., and is suitable for underwater and underwater structures such as irrigation canals and reefs in farming and fishing villages.

In addition, the cement according to the addition of a suitable amount of the admixture prepared by the present invention has an excellent characteristic that the effect of increasing the initial strength is significantly greater even at low temperatures. In case of using ordinary portland cement for concrete construction in concrete with cold temperature below 5 ℃, the compressive strength (typically 30 ~ 50kgf / ㎠) that can secure the resistance to the east sea of concrete is used. Warm curing and warming curing should be performed so as not to receive the East Sea during the initial curing period. However, when the cement containing the admixture according to the present invention is used, the warming curing or warming curing during the initial curing period is omitted or I can alleviate it.

In addition, the cement according to the appropriate amount of admixture prepared by the present invention generates a large amount of edringite, a needle-like expandable mineral in the capillary pores, thereby fixing a large amount of free water with crystallized water to compensate for mortar and concrete dry shrinkage. Can be.

As described above, the admixture according to the present invention can be manufactured by a simple pulverizing mixing process without imparting a special firing process while giving excellent properties to ordinary portland cement, only 1 to 10% by weight of cement, most preferably 4 to Since the use of 6% can express such excellent properties, it is possible to cheaply manufacture concrete products having excellent properties at a low investment cost.

Therefore, by admixing the admixture according to the present invention in 1-10% of ordinary portland cement, the initial strength and long-term strength of the ordinary portland cement are greatly improved, shrinkage reduction and low temperature construction are possible, and durability (flame resistance, acid resistance) is improved. The purpose is to provide a technique for the production of cement admixtures that can be significantly improved.

1 is a graph comparing the compressive strength of cement containing the admixture of the present invention and ordinary portland cement and crude steel portland cement on the market.

Figure 2 is a graph comparing the compressive strength by curing the cement containing the admixture of the present invention and commercially available ordinary portland cement at low temperature (0 ℃).

Figure 3 is a graph comparing the acid resistance of the cement containing the admixture of the present invention and ordinary portland cement on the market.

Figure 4 is a graph comparing the compressive strength of the concrete produced by using the cement containing the admixture of the present invention and the concrete produced using commercially available portland cement on the market.

Figure 5 is a graph comparing the dry shrinkage of the concrete produced by using the cement containing the admixture of the present invention and concrete produced using a commercially available portland cement on the market.

Composition of the admixture according to the present invention for achieving the above object is 75 to 100% by weight of aluminum sulfate and 0 to 10% by weight of sodium carbonate, 0 to 10% by weight of sodium aluminate, 0 to 25% by weight of calcium chloride, 0 to 25% of limestone fine powder 15 wt%, magnesium silicate includes 0-5%, and other materials except fine limestone powder have a specific surface area of 2,000 cm2 / g or more. Aluminum sulfate as the main material is anhydrous aluminum sulfate or aluminum sulfate containing crystal water, which is commercially available (so-called 17% aluminum sulfate-17% Al ₂ O ₃ , or about 57% Al (SO ₄ ) ₂ ). And impurities contained in it have no effect. Sodium carbonate, sodium aluminate, calcium chloride and fine limestone powder, and magnesium silicate which are added in small amounts may also be commercially available.

The most important thing of the admixture according to the present invention is that it can express high strength in early and long-term age, and the cause is that aluminum sulfate, sodium carbonate, sodium aluminate and calcium chloride in the admixture are dissociated into ions in water to perform the hydration reaction of cement. In addition, the aluminum sulfate reacts with calcium hydroxide, which is produced in the hydration reaction of cement, to form a hydrate based on Calcium Sulfur Aluminate (3CaOAl ₂ O ₃ .3CaSO ₄ 32H ₂ O, ettingite). Incorporation of limestone fine powder with a specific surface area of 5000 cm2 / g or more increases the initial strength by 5-10%. This is due to the filling of the voids generated in the hydration of the cement to increase the degree of closedness, some of them to replace the sulfate in the ettringite to form crystals, while the substituted sulfate promotes the reaction of the cement. Magnesium silicate is useful for ready-mixed concrete because it prevents the rapid condensation and hardening of aluminum sulfate, sodium carbonate and sodium sulfate and ensures fluidity in concrete.

Hereinafter, the present invention will be described in more detail with reference to Examples.

(Example 1-3)

The composition of the admixture according to the present invention is shown in Table 1.

In order to verify the physical performance of the cement containing the admixture as described above, H-OPC (an embodiment of the present invention), which is a cement manufactured by mixing the admixture and the ordinary port cement in 5% and 95% by weight, commercially available Experiments were conducted to compare the compressive strength characteristics of the ordinary port cement (OPC) and the crude steel port cement (ESPC), and the results are shown in Table 2 and FIG.

In Table 2, W / C represents the weight ratio of mixed water (W) to cement (C), C in C / S represents cement, and S represents standard yarn. As shown in Table 2 and FIG. 1, H-OPC containing the admixture prepared according to the present invention increased about 43-60% of OPC at almost 3 days of compressive strength, which was almost equivalent to or greater than ESPC. . The 7-day compressive strength was about 30% better than the OPC as well as the ESPC, and the 28-day compressive strength was significantly higher than the OPC and ESPC. Therefore, the cement containing the admixture according to the present invention is very excellent in strength compared to ordinary portland cement, and can be expressed in physical properties almost equal to that of crude steel portland cement, so it is expected to be utilized in large quantities as concrete and concrete secondary products. However, since the admixture having the composition according to Example 3 may cause reinforcing corrosion by calcium chloride when used in reinforced concrete, it is preferable to use it in concrete secondary products and bare concrete.

In order to verify the strength development performance and acid resistance of the cement containing the admixture according to the present invention at low temperatures, by mixing 6% and 94% by weight of the admixture (Example 2 above) and ordinary portland cement, A comparative experiment was conducted with the common portland cement sold. The result is shown in Table 3, FIG. 2, and FIG. Here, the acid resistance test was performed after curing at 20 ° C. for 28 days.

As shown in Table 3, the present invention can express the initial strength at low temperature without loss of the basic performance of the cured product, and it can be seen that it had excellent performance as a mortar and concrete admixture for low temperature construction. It can also be seen that the acid resistance is very good compared to ordinary portland cement.

(Example 4)

In order to verify the physical performance of the cement composition containing the admixture according to the present invention, H-OPC is a cement prepared by mixing 5% and 95% by weight of the admixture and ordinary portland cement prepared as shown in Table 4 ) And commercially available commercial portland cement (OPC) were used to prepare and cure concrete at 20 ° C to measure slump and compressive strength. Concrete specimens were prepared with the formulation as shown in Table 5 and the results are shown in Table 6 and Figure 4. In addition, in order to verify the shrinkage characteristics of the concrete containing the admixture according to the present invention, the admixture is commercially available with H-OPC (invention), which is a cement manufactured by mixing the admixture with ordinary port cement at a ratio of 5% and 95%. After the demoulding, the composition of the concrete prepared by using ordinary portland cement (OPC) was dried at 20 ° C. to measure the shrinkage according to age. The results are shown in Table 7 and Figure 5.

In Table 4, S represents fine aggregate (steel sand, specific gravity 2.54) and G is coarse aggregate (crushed stone, specific gravity 2.62), and the largest dimension is used.

As shown in Table 6, the concrete containing the admixture prepared by the present invention showed about 2 cm less slump immediately after the beam than the concrete containing only OPC, because the adsorbent rapidly absorbs water. However, the change in slump over time can prevent the sudden slump decrease due to the magnesium fluoride contained in the admixture, so that it is not a big problem when used as a ready-mixed concrete in the future. In addition, the initial strength and long-term strength were significantly higher than those of OPC-only concrete. The initial compressive strengths of 1 and 3 days were about 30 ~ 40% greater than that of OPC-only concrete, and were better than about 30% even at 7 days of compressive strength. The long-term age of 28 and 90 days was also significantly higher than that of OPC-only concrete.

As shown in Table 7, the concrete containing the admixture prepared by the present invention can reduce the amount of shrinkage by more than 50% compared to the concrete added only OPC can obtain the effect of preventing the shrinkage cracking of the existing mortar and concrete .

On the other hand, as a result of placing concrete in which the admixture of the present invention was added to the mold of 1m × 1m, it was confirmed that the drying shrinkage was reduced as described above, so that cracking did not occur.

The admixture according to the present invention can be widely used in the production of concrete or concrete products by incorporating 1 to 10% of ordinary portland cement.

That is, the cement composition containing the admixture according to the present invention has a significantly higher initial strength and long-term strength than the composition using ordinary portland cement, significantly reduces shrinkage, and can be manufactured with excellent durability and low temperature construction. Do. Therefore, the working period can be shortened with respect to general civil engineering and construction structures, and construction can be performed at low temperatures, thereby improving efficiency and rationality of construction work. It can also shorten the release cycle and improve productivity with respect to secondary products.

Claims (6)

75 to 100% by weight of aluminum sulfate, 0 to 10% by weight of sodium carbonate, 0 to 10% by weight of sodium aluminate, 0 to 25% by weight of calcium chloride, 0 to 10% by weight of fine limestone powder, and 0 to 5% by weight of magnesium silicate Cement admixture composition, characterized in that. The cement composition according to claim 1, wherein the mixture prepared in the above manner contains 1 to 10% by weight of cement as admixture. The cement admixture composition according to claim 1, wherein the specific surface area of the material excluding the fine limestone powder (specific surface area 5,000 cm 2 / g or more) has a specific surface area of 2,000 cm 2 / g or more. 3. The cement composition according to claim 2, wherein the cement is one of ordinary portland cement, crude steel portland cement, fly ash cement, and blast furnace slag cement. A method for producing ready-mixed concrete, wherein the cement composition containing the admixture according to claim 1 is blended as necessary. A method for producing a concrete secondary product, comprising admixing a admixture or admixture as necessary to a cement composition containing the admixture according to claim 1 or 3.