FI79090C - Hardenable composition and process for making such. - Google Patents

Description

CURING MIXTURE AND METHOD OF ITS MANUFACTURE

SI - HÄRDBAR KOMPOSITION SAMT FÖRFARANDE FÖR FRAMSTÄLLNING AV

A HUNDRED

The present invention relates to a curable composition for a compressible sheet comprising fibers such as ground or ground wood fibers as a backing material, as well as a binder consisting partly of cement and partly of blast furnace slag, a blast furnace slag hardening activator and possible additives combined with hydrogen.

In addition to traditional Portland cement, blast furnace slag, a by-product of pig iron production, has recently been increasingly used as a binder in curable cement-based alloys. Blast furnace slag resembles cement in chemical composition, consisting mainly of oxides of calcium, silicon, aluminum and magnesium. However, the slag differs substantially from the cement in that the amount of silicon relative to the amount of calcium is considerably higher; when the CaO / SiO 2 ratio in the cement is greater than 2, ratio in the slag range 0.9-1.3.

One major reason for replacing Portland cement with blast furnace slag is the cheaper price of the latter material. However, the increasing use of blast furnace slag is also justified by its technical properties. Thus, the slag affects the strength properties of the resulting product so that when it cures more slowly than cement, it weakens the early strength of the product but then gives the product at least the same or even greater strength than Portland cement. Compared to cement, slag also gives the product better sulphate resistance, as well as better seawater resistance, especially at high slag concentrations.

The disadvantage of using blast furnace slag has already been the slow curing mentioned above compared to Port1and cement. In those cases where only slag 79090 has been used as a binder in the mixture, it has been possible to accelerate the curing of the slag with various activating agents, such as alkali metal hydroxides, alkali carbonates, alkali sulphates or water glass. However, when using mixtures of slag and cement, activators have had a disadvantage as they interfere with the hardening of the cement.

It is an object of the present invention to provide a solution which increases the utility of blast furnace slag as a component of a fibrous, sheet-to-sheet curable composition. The invention is characterized in that the mixture contains blast furnace slag ground to a fineness with a specific surface area of at least 1000 m 2 / kg.

The blast furnace slag with a high degree of grinding used according to the invention can be prepared e.g. with a jet grinder. The slag increases the strength of the fibreboard or the like obtained from the mixture according to the invention, in particular its early strength. The increase in early strength achieved with a high degree of grinding of slag is significantly greater than that achieved by increasing the amount of Akti lubricant; mm. Comparative Example 1 below shows that when doubling the amount of activating agent increases the early strength of a conventional slag mixture having a specific surface area of less than 500 m2 / kg by about 1.5 times, increasing the degree of grinding by about 2; 5 times more than twice the early strength, after which the strength can still be increased by about 1.5 times by doubling the amount of activator.

In the curable mixture according to the invention, the fineness of the Portland cement used in addition to the blast furnace slag is preferably lower than the fineness of the slag, e.g. cement having a specific surface area of about 300-500 m 2 / kg can be used.

The mutual ratio of blast furnace slag and cement in the mixture according to the invention may vary. The slag is at least 10% and preferably 10-78%, and the cement is respectively at most 90%, preferably 22-90%. However, it is worthwhile to aim for the highest possible proportion of slag in the mixture.

3 79090

The components of the curable mixture according to the invention may further be pozzolans, such as silica, which may account for 2 to 20% by weight of the mixture. Silica consists of at least 80 Sirsti finely divided SiO2 particles.

Among the possible additives in the curable mixture according to the invention, mention must be made in particular of plasticizers which, as surfactants, improve the castability of the mixture. Sulfonated polyelectrolytes have been found to be a preferred plasticizer, especially in the form of an aqueous solution.

The invention further relates to a process for preparing the above-mentioned curable, compressible mixture. According to the method, a aggregate consisting of fibers, such as ground or ground wood fibers, a binder consisting partly of cement and partly of blast furnace slag, a blast furnace slag hardening activator and possible additives are combined with water, and the method is characterized by using blast furnace slag. the surface area is at least 1000 m / kg and that the cement and the blast furnace slag are added to the mixture in different stages, first mixing the blast furnace slag and the activating agent with water and then adding cement to the mixture in the next step. The addition of cement can take place 5 sec-30 min, preferably about 15 sec-3 min after both blast furnace slag and activator have been combined with water.

By mixing the blast furnace slag and the cement at different times, the effect of the activating agent is only on the slag. In this case, the activator does not interfere with the hardening of the cement. The advantage obtained by mixing with different times is clearly shown in Example 2 below.

The fibers forming the aggregate of the curable mixture are preferably wood fibers, and the invention also relates to the production of a particle board by compression molding from such a mixture having the composition or method of manufacture described above.

The invention is illustrated by the following working examples, of which Example 1 (Comparative Example) compares the strength values of conventional, low grinding slag and high grinding slag concrete mixtures to show the significance of slag grinding degree. -mixtures containing slag and cement with a simultaneous and different mixing of the components.

Es i. Mer kk i_l ^ (comparison)

Microbed concrete was prepared on a laboratory scale in four batches (Experiments 1-4) using blast furnace slag alone as the binder in all cases. In experiments 1 and 2, coarse slag with a fineness of 450 m * / kg was used in a known manner, and in experiments 3 and 4, finely ground slag with a fineness of 1200 m 2 / kg was used. Other material components included silica, which consisted of more than 90% fine, amorphous SiO 2 particles, an activator with 50% aqueous NaOH, a plasticizer with 25% aqueous lignosulfate, water, and sand with a maximum particle size of 5%. mm.

In each experiment, all material components were mixed together simultaneously and cast into concrete. The early strength of the concretes was determined by measuring their compressive strength.

The following table shows the amounts of components in each test in kilograms / m3 of ready-mixed concrete, excluding water, which is a percentage of the amount of slag. In addition, the table shows the compressive strengths (MN / m2) of the concrete measured from 4x4x16 cm pieces after holding 5,79090 pieces for 3, 6, 12 and 24 hours from the time the concrete was mixed at a temperature of + 40 ° C.

_KOE 1_KOE 2_KOE 3_KOE 4_

Coarse slag (kg / m3)

Fine slag

Silica 55 55 55 55

Activator

Plasticizer 9999

Sand 1485 1485 1485 1485

Water (% slag)

Compressive strength (MN / m2) 3 h 9.6 14.4 20.4 29.1 6 h 21.0 29.1 37.7 52.8 12 h 28.8 43.0 51.0 63.3 24 h 45.0 50.0 65.0 72.6

Es ^ mark_2 (invention)

Two binder-reinforced particle boards were prepared using the same material components in the same relative proportions, each with the second board (Experiment 1) mixing all components simultaneously and the second board (Experiment 2) mixing the components in stages. The base material of the boards was wood fibers made of spruce, and the other material components were RHPC cement (Rapid Hardening Portland Cement) with a fineness of 450 m2 / kg, blast furnace slag with a fineness of 1200 m2 / kg, silica formed more than 90% of fine, amorphous SiO 2 particles, an activator with a 50% aqueous NaOH solution and a plasticizer with a 25% aqueous lignosulfate solution. The order of mixing of the components in Experiment 2 was that the blast furnace slag was first mixed with water, 1 min then a plasticizer was added, 1 min after the addition of the plasticizer was added, 1 min after the addition of the activator was added dry cement and 1 min after the addition of cement was added wood fibers. After adding the wood fibers for 9 minutes, the resulting mixture was pressed into a sheet at a pressing pressure of 11a at 34 kg / cm * at 95 ° C with a pressing time of 5 minutes. In the same way, the plate was compressed in Experiment 1.

The following table shows the amounts of material components, the flexural tensile strengths of the resulting sheets measured after compression from the sheets stored at 20 ° C for three and seven days, and the percentage swelling of the sheets stored at three and seven days when kept in water for two hours.

______________________________ TEST 1_____KOE_2________________ RHPC Cement (g / dose) 240 240

Slag 2142 2142

Activator (%) of the amount of slag 5 5

Plasticizer 1.7 1.7

Wood fibers (g / dose)

Water 762 762

Bending tensile strength (N / mm *) 3 days 1.9 7.9 7 days 2.3 11.3

Swelling in water (¾) 3 days - 4.3 7 days _ 4.0

In Experiment 1, swelling could not be measured because the plates did not stick together.

79090

It will be apparent to those skilled in the art that the various embodiments of the invention are not limited to the foregoing examples but may vary within the scope of the appended claims. Thus, for example, other organic or inorganic fibers, such as metal, plastic or glass fibers, can be used instead of wood fibers. The mixtures may also contain, in addition to silica, other pozzolans such as fly ash, peat ash or finely ground quartz sand.

Claims (10)

A curable mixture for a compressible sheet, comprising as a matrix fibers, such as ground or ground wood fibers, and in addition a binder consisting partly of cement and partly of blast furnace slag, blast furnace slag hardening activator and possible additives combined with water, known that the mixture contains blast furnace slag ground to a fineness of at least 1000 m 2 / kg. Mixture according to Claim 1, characterized in that the mixture contains, as binder, in addition to blast furnace slag, Portland cement, the fineness of which is preferably lower than that of the slag. Mixture according to Claim 2, characterized in that the specific surface area of the cement is approximately 300 to 500 m 2 / kg. A mixture according to claim 3, characterized in that the cement has a specific surface area of about 450 m 2 / kg and a slag of about 1200 m 2 / kg. A process for preparing a sheet-pressable mixture according to any one of claims 1 to 4, which process comprises combining a aggregate consisting of fibers, such as ground or ground wood fibers, a binder consisting partly of cement and partly blast furnace slag, blast furnace slag hardening activator and any additives thereof, , that a blast furnace slag having a specific surface area of at least 1000 m 2 / kg is used in the mixture and that the cement and the blast furnace slag are added to the mixture at different stages by first mixing the blast furnace slag and Akti with water and then adding cement to the mixture. 9 79090 Process according to Claim 5, characterized in that the cement is added 15 seconds to 3 minutes after both the blast furnace slag and the activator have been combined with water. Method according to Claim 5 or 6, characterized in that the wood fibers as aggregate are added to the mixture after the addition of the cement. Process according to one of Claims 5 to 7, characterized in that the activating agent is an early hydroxide, an early carbonate, an early sulphate or water glass. 8 79090 A method of manufacturing a particle board, characterized in that the board is produced by pressing from a mixture according to any one of claims 1 to 4, wherein the base material is wood fibers. A method of manufacturing a particle board, characterized in that the board is produced by pressing from a mixture prepared according to any one of claims 5 to 8, in which the frame material is wood fibers. 10 79090