KR101275985B1 - Method of manufacturing composite slag for base of road - Google Patents

Abstract

PURPOSE: A manufacturing method of composite slag for a roadbed is provided to enhance the bearing power, transformation resistance, and corrosion resistance of the composite slag, and to suppress enhance expansion collapse by using the composite slag composed of blast furnace slag and steelmaking slag which are treated with aging for over three months. CONSTITUTION: A manufacturing method of composite slag for a roadbed includes the following steps; the composite slag(40) is prepared by mixing blast furnace slag and steelmaking slag with weight ratio of 3:7-7:3; and the composite slag goes through an aging process for more than 3 months after supplying water with multiple injection pipes. The multiple injection pipes have multiple injection holes. An arrangement stepped pulley of the multiple injection holes gets narrower as it goes toward the center of the composite slag. The composite slag further includes 3-10 weight % of fine powder of the blast furnace slag with an average diameter of 0.001-0.05mm about the blast furnace slag. The composite slag further includes 1-3 weight % of a high alkali base solidifying agent about the blast furnace slag.

Description

Method for manufacturing composite slag for roadbeds

The present invention relates to a composite slag (slag) manufacturing method, and more particularly to a composite slag manufacturing method for mixing steelmaking slag and blast furnace slag to be applied to the roadbed of the road.

In general, road pavement is a structure for protecting, strengthening and leveling the road surface to facilitate the passage of people and vehicles. The pavement is composed of surface and subgrade, and the surface should be smooth even under load, resistant to abrasion, high friction against sliding, and able to resist the freezing and thawing destruction. The roadbed is generally composed of a base layer and an auxiliary base layer, and evenly distributes the load acting on the surface layer, and serves to safely transfer the load onto the roadbed under the roadbed. By the way, the base layer and the auxiliary base layer, when settlement occurs, the surface layer loses its flatness, a pumping phenomenon occurs due to the penetration of rainwater, etc., the roadbed as well as the roadbed itself becomes uneven, even the surface layer is broken and hesitant There are problems such as sitting or cracking.

In recent years, supply and demand of aggregates for roadbeds is difficult and various functions required for roadbeds have been diversified. Therefore, the use of steel slag generated in steel mills and the like has been actively proposed. Since the base of the subgrade is located just below the relatively thin surface, it is necessary to use a material that can support it and have a high resistance to deformation since the pressure distribution of the load transmitted to the base is high. In addition, the auxiliary base must support the cyclic load from the surface layer, distribute it to the roadbed, and deliver it safely. Steelmaking slag is a material suitable for roadbeds because it is hard and has excellent abrasion resistance, and has high bearing capacity, resistance to deformation and corrosion resistance.

On the other hand, steelmaking slag is not suitable for use on the roadbed because of the expansion collapse caused by the reaction with water, it is necessary to ensure the stability of the slag itself caused by expansion collapse. Specifically, most of the quicklime (CaO) added in the pig iron process is made of a stabilized mineral, but a part of f-CaO (free-CaO) that does not dissolve remains in the slag. Since f-CaO reacts with water to expand steelmaking slag, it is not suitable as a roadbed material. However, in order to apply steelmaking slag to a roadbed of a road, it can be used as a roadbed material if the expansion collapse is properly adjusted by an aging treatment which is reacted with air and water after crushing.

By the way, when the steelmaking slag is aged in an outdoor yard, the amount of steelmaking slag is so large that aging does not occur properly, which makes it difficult to control expansion and collapse. In addition, steelmaking slag itself is low in hydraulic properties, even when aged for a long time does not occur properly aging treatment.

The problem to be solved by the present invention is to provide a method for producing a composite slag for roadbed roadbed that is high in bearing capacity, resistance to deformation and corrosion resistance, does not cause subsidence of the roadbed due to expansion and collapse, and performs aging treatment well There is.

Composite slag manufacturing method to solve the problem of the present invention first prepare a composite slag mixed blast furnace slag and steelmaking slag in the ratio of 3: 7 to 7: 3 by weight. Thereafter, the composite slag is subjected to aging treatment for three months or more by supplying water to the plurality of injection holes arranged in the plurality of injection pipes having a predetermined step lowered toward the center of the composite slag.

In an embodiment of the present invention, the composite slag may further comprise a fine powder of the blast furnace slag having a weight ratio of 3 to 10wt% relative to the blast furnace slag, the average particle diameter of 0.001mm to 0.05mm, the composite slag The blast furnace slag may further include as much as 1 to 3wt% solidifying agent in weight ratio. In this case, the solidifying agent may be an inorganic coagulant solidifying agent in which sodium silicate is mixed with water glass or the water glass.

In the method of the present invention, the composite slag may increase the change in specific gravity, water absorption, maximum dry density, unit volume weight, modified CBR, permeability coefficient and expandability as the substitution rate of the steelmaking slag increases. The composite slag may have a uniaxial compressive strength greater than 12 kgf / cm ² when the blast furnace slag and the steelmaking slag are mixed in a weight ratio of 3: 7 to 7: 3. Furthermore, by aging the composite slag for three months or more, it is possible to overcome the expansion of the steelmaking slag and to improve the bearing capacity and the permeability.

In a preferred method of the present invention, the injection pipe is detachable by the connecting portion, the injection hole may be placed at the same position with respect to the yard tank at regular intervals to the injection pipe.

According to the manufacturing method of the composite slag for roadbed of the present invention, the blast furnace slag which has been aged for 3 months or more: by using the composite slag with steel slag 3: 7 to 7: 3, the bearing capacity, resistance to deformation and corrosion resistance This high, collapse of the roadbed does not occur due to expansion collapse, and the aging treatment can be satisfactorily performed. In addition, by supplying water through a supply pipe in which a step is formed in the composite slag, the water penetrates into the composite slag well and the aging treatment can be effectively performed. By the aging treatment by the above device, it is possible to overcome the expandability, which is a disadvantage of steelmaking slag, and to obtain the advantages of improvement in bearing capacity and permeability. Furthermore, by mixing the fine powder or solidifying agent of the blast furnace slag in the composite slag, it is possible to further improve the physical properties of the composite slag for applying to the roadbed.

Figure 1a is a view for schematically illustrating a composite slag manufacturing apparatus for aging treatment by supplying water according to the present invention.
FIG. 1B is a cross-sectional view illustrating the water supply pipe of FIG. 1A. FIG.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. The embodiments described below can be modified into various other forms, and the scope of the present invention is not limited to the embodiments described below. The embodiments of the present invention are provided to enable those skilled in the art to more fully understand the present invention.

The embodiment of the present invention uses a blast furnace slag: steel slag 3: 7 to 7: 3 after three months or more of the aging treatment, by supplying water through a feed pipe formed with a step, thereby supporting the bearing capacity, resistance to deformation And it presents a method of producing a composite slag for roadbed roadbed, which has high corrosion resistance, does not cause settlement of the roadbed due to expansion collapse, and performs aging treatment well. To this end, the physical properties of the composite slag according to the mixing ratio of the blast furnace slag: steelmaking slag 3: 7 to 7: 3 and the aging treatment period, and also propose a method of performing the aging treatment more efficiently. Furthermore, the additive for improving the physical properties of the composite slag will be described in detail the effects of the additive.

Steelmaking slag is divided into converter slag generated when refining pig iron manufactured in blast furnace in the converter and electric furnace slag generated when refining scrap iron in the electric furnace.The furnace slag is oxidized slag and reduction depending on the environment of the furnace during refining process. Separated by slag. In addition, blast furnace slag occurs when steel is manufactured from iron ore in a blast furnace (furnace), and immediately after the blast furnace is present in a molten state at a high temperature of about 1,500 ° C. Separated by slag.

The expansion of steelmaking slag is mainly caused by the hydration and carbonation of CaO and MgO. However, MgO is not reactive due to high heat, so CaO actually affects the expandability. CaO constitutes a silicate phase, a wastite phase, and the like, but a part forms glass lime in which Mg, Mn, Fe, etc. are dissolved in an undissolved state. The glass lime is a factor in the expansion stability of steelmaking slag because the volume expands in response to water. In addition, a part of the oxidized iron enters into the slag, the specific gravity is larger than that of natural lime.

Blast furnace slag is composed of four components, SiO ₂ , Al ₂ O ₃ , CaO and MgO, accounting for about 96% of the total components. In addition, small amounts of MnO, FeO, TiO ₂ , sulfur and alkali (Na ₂ O, K ₂₎ O) and the like. It is known that not only the same chemical composition as cement, but also the chemical reaction also undergoes similar hydration of cement. However, the hydration reaction of blast furnace slag proceeds due to the property of latent hydraulicity which is somewhat different from that of Portland cement. In other words, cement hydraulic property is a mechanism that forms and hardens hydrates when the components start to dissolve when contacted with water, whereas latent hydraulic properties of blast furnace slag do not elute the components simply by contact with water and the presence of a stimulant is necessary. The difference is that this facilitates the reaction of the blast furnace slag.

Specifically, immediately after contact with water, blast furnace slag is eluted with Ca ions, and a glassy oxide film having poor permeability is formed on the surface thereof. The coating prevents the penetration of water into the blast furnace slag particles and the elution of ions from the blast furnace slag particles. However, when OH ⁻ is adsorbed to the blast furnace slag particles by an alkali stimulant, the coating is broken to promote elution of SiO ₂ , Al ₂ O ₃ , CaO and MgO, and the reaction starts. Once the reaction starts, the blast furnace slag is able to maintain a high pH due to the alkali component eluted from itself. Therefore, the amount of alkali stimulant required for the latent hydrocurability of blast furnace slag is only necessary to cause an initial hydration reaction. After that, the CaO and SiO ₂ components contained in the blast furnace slag are eluted for continuous hydration reaction and silicate hydrate (CaO-SiO). ₂ -H ₂ O system) will be formed. Calcium hydroxide, sodium hydroxide, gypsum and the like as alkali stimulants for improving the initial strength by promoting the latent hydraulic properties of blast furnace slag.

Composite slag according to an embodiment of the present invention was subjected to aging treatment for a certain time in order to lower the expandability. Aging treatment refers to a method of oxidizing slag crushed to a predetermined granularity at an appropriate level in a water-containing state and exposing it to air to oxidize the sulfur compound in the slag for a time without coloration. In view of the factors promoting aging, it is desirable to ensure that the water is in sufficient contact with the slag. Since the aging treatment of the composite slag takes a long time and requires a large place, the aging treatment period can be shortened by supplying hot water to promote the hydration reaction when the place is not sufficient.

Figure 1a is a view for schematically explaining a composite slag manufacturing apparatus for aging treatment by supplying water according to an embodiment of the present invention. FIG. 1B is a cross-sectional view illustrating the water supply pipe of FIG. 1A. FIG.

According to Figure 1a and 1b, the manufacturing apparatus of the present invention is a yard 20, composite slag to pile the composite slag 40 mixed with blast furnace slag and steelmaking slag in the ratio of 3: 7 to 7: 3 by weight ratio And a pump 10 for supplying water to the water supply pipe 30 and the water supply pipe 30 inserted into the 40 to spray water. Water supplied to the water supply pipe 30 can be blocked by the valve 14 provided in each water supply pipe 30. For example, the water supply can be shut off by the valve 14 during the rainfall, and the water filled by the rain can be supplied by the drip tray 36.

The water supply pipe 30 has a plurality of injection pipes 32 having a predetermined length and detachable by the connecting portion 38, for example, the first to third injection pipes 32a, 32b, and 32c as shown. do. In other words, if the portion where the composite slag 40 occupies in the yard 20 is large, the number of the injection pipes 32 can be added by the connecting portion 38. The plurality of injection pipes 32, for example, the first to third injection pipes (32a, 32b, 32c) of each of the composite slag 40 in which a plurality of injection holes (34a, 34b, 34c) drilled apart at regular intervals It is formed to have a constant step toward the center. That is, the injection holes 34 drilled in the respective injection pipes 32 are arranged at the same position with respect to the yard 20 at regular intervals.

According to the composite slag manufacturing apparatus for the roadbed according to an embodiment of the present invention, the composite slag (arranged) of the plurality of injection holes 34 each of the plurality of injection pipes 32 has a constant step for each injection pipe, The closer to the center of the 40) is closer to the yard tank 20. As a result, the composite slag 40 can be smoothly supplied with water, thereby increasing the effect of aging treatment. By the step, it is possible to effectively perform the aging treatment by smoothly flowing the water by gravity to allow the water to properly penetrate the center of the composite slag 40, which is relatively difficult to access the water.

Hereinafter, the physical properties of the composite slag through the preferred embodiment of the present invention will be described in detail. However, the embodiments presented herein are not intended to limit the present invention to illustrate the present invention. An embodiment of the present invention first looks at the various properties affected by the mixing ratio and the aging treatment period of the blast furnace slag and steelmaking slag, and then if the additive is added to further improve the physical properties affected by the mixing ratio and aging treatment period It will be described by dividing by.

<Without additives>

Table 1 shows the particle size change according to the mixing ratio of the composite slag by the aging treatment period according to an embodiment of the present invention. In this case, Table 1 shows the particle size change according to the mixing ratio of the composite slag after mixing the blast furnace slag and steelmaking slag after aging for 6 months, respectively.

Blast furnace: Steelmaking % Of mass passed through sieve 50mm 40mm 20mm 5 mm 2.5mm 0.4mm 0.08mm 100 95-100 60-90 30-65 20 to 50 10 to 30 2 ~ 10 3: 7 100 99.3 84.8 55.1 33.3 15.5 6.0 5: 5 100 99.5 87.0 56.1 34.3 16.7 6.9 7: 3 100 99.7 89.1 58.0 35.2 18.0 7.7

According to Table 1, the majority of the composite slag for the base layer and the sub-base layer of the roadbed is mixed with a plurality of slags having different specific gravity, so that the particle size regulation is prescribed by volume percentage in order to accurately indicate the particle size distribution. However, particle size management is carried out by weight percentage, so the test report lists the volume percentage and the weight percentage. In other words, the particle size distribution of each slag to be mixed is obtained, and the volume distribution ratio of each slag is determined in accordance with the particle size of the target base and auxiliary base composite slag by using the particle size distribution by the volume percentage. Preparation of the composite slag in this Example was tested by combining the weight percentage.

In Table 1, all the mass percentages of the samples passed through the sieve met the KS criterion. In addition, there was no significant change in the particle size distribution curve. In particular, as the blast furnace slag increased, the content of the particle size of less than 5mm tended to increase. Accordingly, it was confirmed that the volumetric mixing ratio is suitable for using the composite slag of the present invention as a roadbed.

Table 2 shows D ₁₀ (mm), D ₃₀ (mm), D ₆₀ (mm), C _u and C _c values according to the mixing ratio of the composite slag according to the aging treatment period according to the embodiment of the present invention. At this time, the particle size corresponding to 10% of the weight percentage in the particle size distribution curve is called an effective particle size (effective particle size), it is represented by D ₁₀ . In addition, constants representing the shape of the particle size distribution curve include a coefficient of uniformity (C _u ) representing the slope of the curve and a coefficient of curvature (C _c ) representing the shape of the curve. The equality coefficient refers to the ratio of the particle size, ie, D ₆₀ , corresponding to 60% of the weight of the pass through to the effective particle size D ₁₀ . D ₃₀ also refers to the size of the particles passing 30%.

Blast furnace: Steelmaking D10 (mm) D30 (mm) D60 (mm) Cu Cc 3: 7 0.2 1.9 5.8 29.00 3.11 5: 5 0.14 1.85 5.1 36.43 4.79 7: 3 0.105 1.85 5 47.62 6.52

According to Table 2, as the mixing ratio of the blast furnace slag increased, D ₁₀ and D ₆₀ tended to decrease, and C _u and C _c increased. It can be seen from the table that the particle size distribution is good because C _u is 20 or more in all cases regardless of the mixing ratio and C _c is between 1 and 7 regardless of the mixing ratio. Therefore, when the three types of blast furnace slag and steelmaking slag were combined, the particle size was satisfied with the KS standard.

Table 3 shows the specific gravity and the absorption rate (%) of the composite slag according to the mixing ratio according to the embodiment of the present invention.

% Substitution 0 30 50 70 100 importance 2.60 2.66 2.80 2.96 3.36 Absorption rate 2.54 2.68 3.05 3.04 3.37

According to Table 3, the specific gravity of the composite slag was found to increase gradually with increasing the steel slag substitution rate. On the contrary, as the substitution rate of steelmaking slag increases, the absorption rate of the composite slag decreases. In general, when the absorption of aggregate is too large, it is unsuitable for road use.In the test results, composite slag of 3: 7 and 5: 5 ratio except the ratio of blast furnace slag and steelmaking slag is 7: 3, based on absorption rate of steelmaking slag 3.0 Less than% was satisfied, and even when the mixing ratio was 7: 3, the criterion of blast furnace slag was less than 3.5%.

As a result of the invention on the absorption rate of slag, when the sample was immersed for 24 hours and the absorption rate was measured over time, the absorption rate was about 50% of the 24 hour absorption rate after 30 minutes, which means that the instantaneous absorption rate was high. . Therefore, composite slag must be used by pre-wetting to be used for construction aggregate or roadbed. On the other hand, hydraulic grade granular blast furnace slag (HMS-25), grain sized steel slag (MS-40, MS-25) and crusher steel slag (CS-40, CS-30, CS-) 20) is used for base and auxiliary base materials, so there is no problem about specific gravity and absorption rate. In addition, when considering the specific gravity of soil and aggregate, the specific gravity of steel slag was 3,26 ~ 3.37 and the specific gravity of blast furnace slag was 2.53 ~ 2.61, which is similar to that of sand or gravel.

Table 4 shows the optimum function ratio (%) according to the aging treatment and mixing ratio of the composite slag according to the embodiment of the present invention. In the embodiment of the present invention, the experiment was carried out by impact compaction. Impact compaction is compaction method by impact load, Rammer was used. This method makes it easy to convert the point of impact according to KS F 2535 and the impact energy.

Aging treatment
term Steel slag substitution rate (%) 0 30 50 70 100 Do not process 7.83 7.35 7.33 7.15 7.27 1 month 7.65 7.50 7.33 7.18 7.34 2 months 7.77 7.38 7.51 7.00 7.27 3 months 7.34 7.24 7.39 7.18 7.32 4 months 7.57 7.82 7.42 7.51 7.31

According to Table 4, the optimum function ratio distribution was 7-8%, which was slightly higher than that of 6% of ordinary crushed aggregates, and the optimum function ratio decreased as the substitution rate of steelmaking slag increased. However, the effect of the aging period was not apparent. That is, when the substitution rate of steelmaking slag was 0%, the average of the optimum function ratio was 7.63%, but when the substitution rate was 100%, the average of the optimal function ratio was 7.31% and the optimal function ratio decreased 4.3%.

In general, the effect of moisture content during indoor or field compaction is that, when the water is filled between particles, the fine granules are separated into the water after the compaction energy is given to the material. Settlement causes density variations in the compaction layer. When the particles are completely saturated, the compaction energy is absorbed by the water and energy loss occurs. Therefore, when the same granular material is used for the granulated material, it may be difficult to compact the same energy. However, when the particles are wet, the sliding conditions between the particles are changed as the friction of the particle surface is changed, or the particles are easily broken because the strength of the wet particles is usually lower than that of the dry particles. As a result, the presence of water between the particles, such as a relatively easy condition for filling, causes a complicated effect on the compaction mechanism, so the optimum function ratio is very important in the field construction of the roadbed.

Table 5 shows the maximum dry density (t / m ² ) according to the aging treatment and mixing ratio of the composite slag according to the embodiment of the present invention. In this case, Table 5 shows the maximum dry density according to the steel slag substitution rate and the aging treatment period as a result of the compaction test of Table 4.

Aging treatment
term Steel slag substitution rate (%) 0 30 50 70 100 Do not process 2.110 2.203 2.300 2.420 2.580 1 month 2.140 2.220 2.300 2.410 2.610 2 months 2.140 2.190 2.290 2.420 2.622 3 months 2.150 2.200 2.290 2.395 2.658 4 months 2.140 2.175 2.279 2.405 2.619

According to Table 5, the compaction test showed that the maximum dry density was 2.11 t / m ² ~ 2.65 t / m ² , which was slightly higher than that of 2.2 t / m ² of ordinary crushed aggregate. In general, in the case of particle crushing, the aspect of compaction becomes complicated, but it is based on the initial particle size composition, but when the crushed particles are moved to the gap between the particles during compaction, the compaction proceeds due to the movement of the crushed particles. While the compaction proceeds by the gap movement, the compaction does not proceed under the condition that the gap movement of the particles does not occur. On the other hand, particle crushing can be performed by: i) physical and mechanical properties of the particles themselves (particle shape, particle strength, etc.), ii) constituent conditions of the particles (particle composition, maximum particle size, minimum particle diameter, etc.) It occurs due to complex effects such as the transmission method (environmental condition of the assembly material to be compacted, energy supply method, etc.).

In the case of the composite slag according to the embodiment of the present invention, when the substitution rate of steelmaking slag was 0%, the average maximum dry density was 2.14t / m ^2, but when the substitution rate was 100%, the average maximum dry density was 2.62t / m ² . Maximum dry density increased by about 20%. In general, increasing the maximum dry density increases the bearing capacity of the ground and thus has a good effect on the bearing capacity. There is no influence of aging treatment because there is no tendency of maximum dry density with aging treatment period. In addition to the above results, it can be seen that as the substitution rate of steelmaking slag increases, the optimum function ratio decreases and the maximum dry density increases.

Table 6 shows the unit volume weight (kg / L) according to the aging treatment and mixing ratio of the composite slag according to the embodiment of the present invention. At this time, Table 6 shows the unit volume weight according to the steel slag substitution rate and the aging treatment period as a result of the compaction test of Table 4.

Aging treatment
term Steel slag substitution rate (%) 0 30 50 70 100 Do not process 1.725 1.869 1.992 2.155 2.239 3 months 1.734 1.879 1.988 2.175 2.242 6 months 1.778 1.872 1.987 2.125 2.235

According to Table 6, the unit volume weight test results showed that blast furnace slag (substitution rate of 0%) was 1.725-1.778 kg / l, and using only steelmaking slag (substitution rate of 100%) was 2.239-2.235 kg / l. In addition, there was no significant change in unit volume weight by aging treatment, and the unit volume weight tended to increase as the steelmaking slag substitution rate increased. This is because the proportion of steelmaking slag is high, and in general, if the unit volume weight is increased, the ground bearing capacity increases, which has a good effect on the bearing capacity.

Although the unit volume weight according to the aging treatment period does not seem to be significantly affected by the aging treatment, the optimum function ratio decreases and the maximum dry density and unit volume weight increase as the substitution rate of steelmaking slag increases. appear. That is, as the mixing ratio of the steelmaking slag with a specific gravity is increased, the unit volume weight is increased, and more than 1,500kg / L regardless of the mixing of materials.

Table 7 shows the change of the modified CBR according to the aging treatment and mixing ratio of the composite slag according to the embodiment of the present invention. In this case, the modified CBR is called the modified CBR, which represents the strength of the auxiliary base material that can be expected in the field. CBR value after 4 days immersion corresponding to dry unit weight multiplied by compaction degree.

Aging treatment
term Steel slag substitution rate (%) 0 30 50 70 100 Do not process 83 94 107 123 144 1 month 85 94 104 126 146 2 months 85 95 109 129 153 3 months 87 108 111 131 153 6 months 85 105 112 133 155

According to Table 7, the modified CBR values were all 80 or more, and the modified CBR values tended to increase as the steel slag substitution rate increased. On the other hand, the limit of compaction of the granulated material will be the original rock, even if the particles are combined so that there is no gap between the particles. When particle crushing does not occur in normal compaction, it is a limit of compaction when a particle group makes a stable structure corresponding to compaction energy. The compaction system is not sufficiently compacted when the compaction energy is insufficient or when the repulsive force between the particles occurs due to the excessive compaction energy, but the compaction system including the granular composition of the granulated material, the properties of the particles themselves, the layer thickness, and the effective compaction energy of the compaction machine. The intrinsic limit state is formed at the limit in normal compaction. Such limitation exists even when particle breakage occurs by compaction.

In the case of the composite slag of the present invention, when the substitution rate of steelmaking slag was 0%, the average of the modified CBR value was 85. However, when the substitution rate was 100%, the average of the modified CBR value was 137.2, and the modified CBR value increased by 58%. As the substitution rate of steelmaking slag increases, the modified CBR value increases, and as the aging treatment period increases, it tends to increase slightly. In the case of particle size adjustment slag, the KS criterion is satisfied if the modified CBR value is over 80. The modified CBR test value always exceeds 80 regardless of the aging treatment period and the steel slag substitution rate, so that the load transmitted from the top can be sufficiently supported by the strength of the composite slag regardless of the mixing ratio and steel slag substitution rate.

However, the modified CBR value of the present invention was found to increase as the substitution rate of steelmaking slag increases and the aging treatment period increases. For example, when 70% is substituted compared to when the substitution rate is 30%, the modified CBR value is 28.8%. Due to the strong engagement effect according to the excellent properties of the steelmaking slag, physical properties that can sufficiently support the load transmitted from the top of the road are realized. Although the modified CBR value is 80 or more regardless of the substitution rate, the composite slag according to the embodiment of the present invention can secure more sufficient bearing capacity.

Table 8 shows the change in the permeability coefficient (10 ^-4 cm / sec) after 6 months aging treatment of composite slag according to the embodiment of the present invention. At this time, the permeability coefficient is a constant (velocity dimension) indicating the degree to which soil in any state passes water. The size of the permeability coefficient depends on the viscosity of the liquid and the density, passage area and shape of the sample. Viscosity is a function of temperature, so if the temperature is high and the viscosity is low, the permeability coefficient increases. Hazen assumes that the permeability coefficient of a viscous and clean granule is proportional to the square of the effective particle diameter, and k (permeability coefficient; cm / sec) = C × (D ₁₀ ) ² [C is a constant from 1.0 to 1.5, D ₁₀ Has an effective particle diameter (mm)].

Steel slag substitution rate (%) 0 30 50 70 100 6.6 7.4 7.6 11.9 13.6

According to Table 8, the coefficient of permeability increased approximately 1.4 times from 5.5 × 10 ⁻⁴ cm / sec on the basis of 0% steelmaking slag to 13.3 × 10 ⁻⁴ cm / sec on the 100% substitution rate. Permeability coefficient increases as the ratio of steelmaking slag to composite slag increases, because the grain size of steelmaking slag is larger than the blast furnace slag as a whole, and in particular, the fine grain content is small. The higher the substitution rate of steelmaking slag (more than 70%), the better the modified CBR value and the permeability coefficient, indicating the bearing capacity, which can be maximized as roadbed. However, there is a need for measures to reduce the expandability, which is the biggest disadvantage of steelmaking slag.

Table 9 shows the C and D ₁₀ (mm) at Hazen permeability coefficient (10 ⁻⁴ cm / sec) after 6 months aging of the composite slag according to the embodiment of the present invention.

division
Steel slag substitution rate (%) 0 30 50 70 100 Average Permeability coefficient 6.6 7.4 7.6 11.9 13.6 9.4 D ₁₀ 0.09 0.11 0.14 0.20 0.31 0.169  Official coefficient 8.1 6.7 3.9 3.0 1.4 4.6

According to Table 9, the coefficient C of the composite slag was found to be 4.61 on average, and the coefficient of permeability increased in proportion to the particle D ₁₀ . On the other hand, Hazen's formula uses only D ₁₀ to calculate the permeability coefficient, but the actual permeability coefficient is not only different from D ₁₀ but also depends on various complex factors such as pore ratio, compaction, hydraulic gradient, and grain structure. It may be indicated.

Table 10 shows the change in the expandability of the composite slag according to the mixing ratio after the three months and six months aging treatment according to an embodiment of the present invention.

division
Steel slag substitution rate (%) 30 50 70
Three months of aging
The first experiment 1.19 1.29 1.39 Second experiment 1.09 1.29 1.32 Third experiment 1.22 1.22 1.28
6 months
The first experiment 1.04 0.73 1.06 Second experiment 1.11 0.84 1.01 Third experiment 0.83 0.93 0.96

According to Table 10, the higher the substitution rate of steelmaking slag, the larger the expansion ratio of the composite slag. This is because the expansion of steelmaking slag is larger than that of the blast furnace slag, and the effect of reducing the amount of expansion due to the blast furnace slag also appears. In steelmaking slag, hydration of free-CaO and free-MgO is the cause of expansion, and expansion of free-CaO continues for a long time due to rapid expansion of free-CaO. Meets and changes to Ca (OH) ₂ , resulting in expansion of the material. The chemical formula for this is as follows.

CaO + H ₂ O → Ca (OH) ₂

Residual free-CaO can cause the material to expand, and damage can occur in many ways.

In order to solve the above problems, the average expansion ratio of composite slag was 1.16% when steel slag substitution rate was 30%, 1.26% when 50%, and 1.33% when 70% was replaced. KS standards (1.5% or less of blast furnace slag and 2.0% or less of steelmaking slag) were satisfied. In the case of 6 months of aging treatment, the average expansion ratio of the composite slag was 0.97% when the steel slag substitution rate was 30%, 0.92% when 50%, and 1.02% when the replacement rate was 70%. Slag 1.5% or less, steelmaking slag 2.0% or less). After 3 months, the expansion rate of the composite slag after 6 months is smaller than that of the composite slag, showing about 1% expansion rate. If steel slag is to be used as a composite slag roadbed, the aging treatment should be used for 3 months or more to overcome the disadvantages of steel slag inflation and improve the bearing capacity and permeability.

Table 11 shows the change in uniaxial compressive strength (kgf / cm ² ) according to the curing period and the mixing ratio of the composite slag according to the embodiment of the present invention with respect to the aging treatment period. At this time, the uniaxial compressive strength of 12 kgf / cm ² KS standard Values below are underlined.

division
Uniaxial compressive strength (kgf / ㎠) Aging 0 months 1 month of aging 2 months Three months of aging 6 months Blast furnace: Steelmaking 14 days 28 days 91 days 180 days 14 days 28 days 91 days 14 days 28 days 91 days 14 days 28 days 91 days 14 days 28 days 91 days 10: 0 15 20 25 27 14 19 26 15 25 27 14 27 29 14 28 29 7: 3 14 19 20 24 10 15 26 12 14 21 13 12 19 13 15 24 5: 5 12 13 18 20 14 17 30 10 16 22 13 15 18 13 17 22 3: 7 11 14 14 16 9 13 23 12 12 16 12 14 17 12 17 20 0:10 9 14 14 17 9 13 19 11 13 15 10 13 14 10 13 17

 According to 11, irrespective of the aging treatment period, when the steelmaking slag substitution rate is 70% or more in 14 days of curing, the uniaxial compressive strength criteria are not met. However, if the curing period is more than 28 days, most of them meet the uniaxial compressive strength criteria. Therefore, it can be seen that the uniaxial compressive strength of composite slag is more affected by curing period and steel slag substitution rate than aging treatment period. In addition, as the substitution ratio of steelmaking slag increases, the uniaxial compressive strength of the composite slag is found to be generally smaller, and the compressive strength of the composite slag also increases as the age is increased. However, 3 months and 6 months of aging treatment satisfied the criterion of the compressive strength regardless of the curing period when the ratio of blast furnace slag: steel slag is 7: 3 to 3: 7.

Table 12 shows the in-phase ratio (%) according to the mixing ratio of the composite slag according to the embodiment of the present invention for the aging treatment period of 3 months and 6 months. At this time, the experiment was carried out with reference to the Japan Road Association pavement test manual.

Granularity division Steel slag substitution rate (%) 0 30 50 70 100 Three months of aging Frosting rate (%) 0.198 0.216 0.192 0.195 0.188 6 months 0.219 0.226 0.194 0.195 0.192

According to Table 12, even if frostbite frost does not occur, freezing and thawing may reduce the support force of the auxiliary base and damage the road. This usually occurs due to rapid melting in the spring. In this state, melting occurs from the top to the bottom of the soil layer, so that there is a soft soil layer melted under the package, and the bearing capacity of the package decreases drastically. The possibility of such strength loss is very high when there is a high rainfall between autumn and winter due to high saturation of subbases or heavy rainfall during freezing and thawing.

At 3 months of aging treatment, when the substitution rate of steelmaking slag was 0, the in-phase ratio was 0.198%. When the substitution rate of steelmaking slag was 70%, it was 0.175%. However, in the six-month aging treatment, as the steelmaking slag mixture ratio increases, the frostbite ratio tends to be lower. This is because the frostbite slag has a high absorption rate, which is considered to be slightly higher. However, as a whole, as the substitution rate of steelmaking slag increases, the effect of preventing frostbite increases.

The composite slag manufactured by the manufacturing apparatus according to the embodiment of the present invention has a C _u of 10 or more and a C _c of 1 to 7 regardless of the aging treatment period, so that the particle size distribution is very good, and the road steel slag The KS standard was met. In addition, as the substitution rate of steel slag increased in the composite slag, the specific gravity of the composite slag gradually increased, and the absorption rate was 3.5% or less, which is the KS standard in all formulations. Furthermore, the optimum function ratio was about 7.5% when the substitution rate of steelmaking slag was 70%, and the maximum dry density was about 2.405, which had little effect on the aging treatment period.

In the composite slag of the present invention, the modified CBR value was mostly 100% or more, and the modified CBR value was increased in proportion to the substitution rate and the aging treatment period of steelmaking slag. In addition, as the ratio of steelmaking slag to composite slag increases, the permeability coefficient increases, and as a result of estimating the permeability coefficient according to the aging treatment period from the particle size distribution test results, the permeability coefficient decreases according to the aging treatment period. The decrease was greatly reduced. Furthermore, the expansion ratio of the composite slag gradually decreases as the aging treatment period increases, and the expansion ratio of the composite slag increases as the substitution rate of the steelmaking slag increases. The immersion expansion ratio of steelmaking slag was less than 2.0% of KS standard when the aging treatment period was more than 2 months. In addition, after six months of aging, the composite slag of all formulations exhibited an expansion rate of 2.0% or less.

In the composite slag of the present invention, as the substitution rate of steelmaking slag increases, the uniaxial compressive strength of the composite slag is generally reduced. As the curing days of the composite slag increase, the uniaxial compressive strength gradually increases, and the initial strength of the composite slag increases. Larger long-term intensity was also expressed. In addition, as a result of freeze-thawing experiment after 6 months of aging treatment of composite slag, when the substitution rate of steelmaking slag was 50%, the phase frosting rate was 0.194%, and the substitution rate of steelmaking slag was low.

The composite slag according to the embodiment of the present invention was affected by the substitution rate of steelmaking slag in specific gravity, optimum function ratio, maximum dry density, unit volume weight, modified CBR value, permeability coefficient, change of expandability, uniaxial compressive strength and in-phase ratio. . In particular, the permeability coefficient was largely affected by the substitution rate, and the average expansion ratio satisfied the KS criterion when the blast furnace slag: steel slag was aged from 3 months to 6 months or more at 3: 7 to 7: 3. In addition, in the case of uniaxial compressive strength, when the blast furnace slag: steel slag subjected to aging treatment for at least 3 months or at least 6 months was 3: 7 to 7: 3, the KS criterion was satisfied regardless of the curing period. In addition, the composite slag of the present invention by aging treatment for more than three months, it is possible to overcome the expandability which is a disadvantage of steelmaking slag and to obtain an improvement in bearing capacity and permeability.

<If an additive exists>

In recent years, the functions required for the roadbed have been diversified, and a composite slag having better physical properties has been required. Accordingly, in the embodiment of the present invention, 3 to 10% by weight of blast furnace slag fine powder having an average diameter of 0.001 mm to 0.05 mm is added to the blast furnace slag: steel slag 3: 7 to 7: 3 composite slag. Or adding 1 to 3% by weight of a high alkali-based solidifying agent to the blast furnace slag. In addition, when the fine powder and the hardening agent were added, the average expansion ratio and uniaxial compressive strength were performed in the same manner as described above. At this time, the price of the hardener and the hardener is relatively expensive, it is not economical to add more than 3wt%. The solidifying agent according to an embodiment of the present invention may vary within the scope of the present invention, but inorganic coagulant solidifying agents such as a mixture of sodium silicate mixed with high alkali water glass and water glass capable of promoting the hydration reaction of blast furnace slag include desirable.

Table 13 shows the change in the expandability of the composite slag including the blast furnace slag fine powder and the solidifying agent after three months of aging treatment according to an embodiment of the present invention.

division
Fine powder content (wt% / blast furnace slag) Solidifying agent content (wt% / blast furnace slag) 3 5 10 One 2 3
Blast furnace: Steelmaking
3: 7 0.38 0.35 0.39 0.32 0.34 0.34 5: 5 0.35 0.33 0.25 0.41 0.31 0.35 7: 3 0.25 0.26 0.24 0.27 0.26 0.23

According to 13, when the blast furnace slag fine powder was added as compared with only the composite slag, the expansion coefficient did not have a significant effect, and the solidifying agent also did not show an increase in the expandability according to the addition amount. The results are shown.

Table 14 shows the uniaxial compressive strength (kgf / cm ² ) after three months of aging treatment of the composite slag containing blast furnace slag fine powder according to an embodiment of the present invention.

division
Fine powder content (wt% / blast furnace slag) Solidifying agent content (wt% / blast furnace slag) 3 5 10 One 2 3
Blast furnace: Steelmaking
3: 7 16 29 35 18 32 40 5: 5 18 29 37 21 42 47 7: 3 21 36 42 22 42 45

According to Table 14, when the blast furnace slag fine powder was added, the uniaxial compressive strength change was rapidly increased when the replacement amount of the blast furnace slag fine powder was 5% or more, and the high alkali solidifying agent was added according to the addition amount. The increase in compressive strength is increasing greatly, and the result does not increase significantly at the addition amount of 2% or more. However, under all the conditions, the strength increase of about 70% or more than the composite slag alone is possible, thus ensuring stable support.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, but many variations and modifications may be made without departing from the scope of the present invention. It is possible.

10; Pump 20; Yard
30; Water pipe 32; Injection pipe
34; Injection hole 36; Drip
38; Connection 40; Composite slag

Claims (9)

Preparing a composite slag in which blast furnace slag and steelmaking slag are mixed in a weight ratio of 3: 7 to 7: 3; And
Manufacturing the composite slag for the roadbed including the step of supplying water to the plurality of injection holes arranged with a predetermined step lowered toward the center of the composite slag to the plurality of injection pipes in the composite slag for more than three months Way. The composite slag of claim 1, wherein the composite slag further comprises a fine powder of the blast furnace slag having a weight ratio of 3 to 10 wt% with respect to the blast furnace slag, and an average particle diameter of 0.001 mm to 0.05 mm. Slag production method. The method of claim 1, wherein the composite slag further comprises 1 to 3 wt% of a high alkali-based hardener in a weight ratio with respect to the blast furnace slag. The method of claim 3, wherein the solidifying agent is water glass or an inorganic flocculating solidifying agent in which sodium silicate is mixed with the water glass. The method of claim 1, wherein the composite slag increases the change in specific gravity, water absorption, maximum dry density, unit volume weight, modified CBR, permeability coefficient and expandability as the substitution rate of the steel slag increases. Composite slag manufacturing method. The roadbed according to claim 1, wherein the composite slag has one side compressive strength greater than 12 kgf / cm ² when the blast furnace slag and the steelmaking slag are mixed in a weight ratio of 3: 7 to 7: 3. Composite slag manufacturing method for. The method of claim 1, wherein the composite slag is aged for three months or more, thereby overcoming the expansion of the steelmaking slag and improving bearing and permeability. The method of claim 1, wherein the injection pipe is detachable by the connection portion composite slag manufacturing method for the roadbed. The method of claim 1, wherein the injection hole is placed at the same position with respect to the yard tank at regular intervals in the injection pipe.

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