FI78307B - FOERFARANDE FOER FRAMSTAELLNING AV EN HAERDBAR KOMPOSITION. - Google Patents

Description

78307

METHOD OF PREPARING THE HARDENABLE MIXTURE - FÖRFARANDE FÖR FRAMSTÄLLNING AV EN HÄRDBAR KOMPOSITION

The present invention relates to a process for preparing a curable mixture, in which a aggregate such as sand, gravel and / or fibers, a binder consisting partly of cement and partly of blast furnace slag, a blast furnace slag hardening activator which is alkali hydroxide, alkali carbonate, water glass or alkali sulphate, and any additives are combined with water.

The curable mixtures to be prepared according to the invention are, in particular, concretes and mortars in which the aggregate is formed by sand or gravel, the roughness of which varies according to the application. The invention furthermore relates to compositions which can be compressed into sheet-like products in which the base material is fibers, in particular ground or ground wood fibers.

In concrete mixes in particular, in addition to traditional Portland cement, blast furnace slag, a by-product of pig iron production, has recently been increasingly used as a binder. 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 is relative. . the amount of calcium in it is considerably higher; when the ratio CaO / SiOg 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 ____ because of its technical properties. Thus, the slag affects the strength properties of the concrete so that when it cures more slowly than the cement it weakens the early strength of the concrete after casting but then gives the concrete at least the same or even higher strength than Portland cement. Compared to cement, slag also gives concrete 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 Portland cement. Although the hardening of the slag can be accelerated with various Akti lubricants, these have only been of significant benefit when only slag has been used as a binder in the concrete. When using mixtures of slag and cement, activators have proven to be harmful, as they interfere with the hardening of the cement.

It is an object of the present invention to provide a novel method for preparing a concrete or other curable mixture which enables the efficient use of an activating agent in cases where both cement and blast furnace slag are included in the mixture at the same time. The method according to the invention is characterized in 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 idea of the intermittent addition of slag and cement according to the invention is that the activating agent is allowed to be absorbed into the slag so that it no longer affects the cement to be added afterwards and does not interfere with its hardening. Although this idea is so far only an assumption and does not limit the invention per se, it is supported by the experimental results presented below, which show the advantage of the invention over the known simultaneous combination of cement, slag, activator and water.

Since the activator is immediately attached to the slag in the water, the cement could be introduced into the mixture immediately after the mixture of slag, activator and water has been made homogeneous, i.e. practically about 5 seconds after the moment of mixing. Preferably, the cement is added about 15 seconds to 3 minutes after the slag and activator have been mixed with water. It would be possible to add sand, gravel, wood fibers or similar aggregates to the mixture at the same time as the cement, but preferably the ingredients are added only after the slag and cement have mixed with each other in the water, e.g. a few minutes after the addition of the cement. The final limit for the addition of aggregate is the start of the hardening process of the binders, i.e. slag and cement, about 30-60 minutes after they have been combined with water.

The mutual ratio of blast furnace slag and cement in the mixtures prepared according to the invention can vary in the range of 10-78% slag and 90-22% cement. However, in mixtures, it is generally profitable to aim for the highest possible proportion of slag.

According to a preferred embodiment of the invention, blast furnace slag is ground into the mixture, which has been ground to a higher fineness than the cement used. The specific surface area of the blast furnace slag may be e.g. greater than 500 m * / kg or even greater than 1000 m * / kg, while the specific surface area of the cement used typically remains less than 500 m * / kg. High-grade grinding of blast furnace slag is able to improve the strength of the resulting concrete or fiberboard, especially its early strength.

Among the additives which can be used in the process according to the invention, mention must be made in particular of plasticizers which, as surfactants, improve the castability of the resulting mixture. Preferred plasticizers have been found to be sulfonated polyelectrolytes, in particular an aqueous lignosulfonate which can be mixed with water simultaneously with blast furnace slag and an activating agent.

4 78307

The invention is illustrated in the following by means of exemplary embodiments comparing the strength values of concretes (e.g. 1-3), mortars (e.g. 4) and particleboards (e.g. 5) obtained by different time mixing according to the invention and known simultaneous mixing. However, the examples do not limit the invention, the applications of which may vary within the scope of the claims set out below.

Example 1

The aerated concrete was prepared on a laboratory scale in two batches, each using the same material components in the same mutual ratios, so that in one case (Experiment 1) all components were mixed simultaneously and in the other case (Experiment 2) according to the invention in stages. The material components were RHPC cement (Rapid Hardening Portland Cement) with a fineness of 450 m * / kg, blast furnace slag with a fineness of 1200 m 2 / kg, silica consisting of more than 90% fine, amorphous SiO 2 particles, activator with 50% aqueous NaOH, plasticizer with 25% aqueous lignosulfate, water and sand with a maximum particle size of 5 mm.

In Experiment 2, the mixing order of the components was that the blast furnace slag and silica were first mixed with water in an amount of 28% of the slag, 1 min then a plasticizer was added, 1 min after the plasticizer was added an activator, 1 min after the activator was added cement slurried in water that the amount of water added at this point was 32% of the amount of cement, and finally 1 min after the addition of cement, sand was added.

The following table shows the amounts of components in kilograms / m3 of ready-mixed concrete, excluding water, which is given as a percentage of the total amount of binder, ie cement and slag. In addition, the table shows the compressive strengths (MN / m *) of the concretes obtained in the experiments after the concrete had been kept at a temperature of + 50 ° C for 5, 7 and 14 hours.

K0E_1___________K0E_2___________ RHPC cement (kg / m3) 370 370

Slag 150 150

Silica 20 20

Activator 9 9

Plasticizer 7 7

Sand 1518 1518

Water (¾ binder.) 32 32

Compressive strength (MN / m3) 5 h 9.5 25.0 7 h 25.2 34.8 14 h 43.2 49.1

Example 2 - Two hollow core slabs were prepared each using the same material components in the same relative proportions, so that in the production of the second slab (Experiment 1) all components were mixed simultaneously and in connection with the second slab (Experiment 2) according to the invention in stages. The components were the same as in Example 1, except that instead of the sand of Example 1, very fine aggregate sand with a particle size of 0-1 mm, sand with a particle size of 0-8 mm, and small stones with a size of 6-12 mm were used.

In Experiment 2, blast furnace slag, silica, activator, fine aggregate sand, coarser sand, and small stones were mixed simultaneously with water. After 1 min a plasticizer was added and after 1 min of dryener dry cement was added, after which the concrete mix was ready to be poured.

The following table shows the amounts of components and the compressive strengths of the obtained concretes in the same way as in Example 1. The compressive strengths were measured on 100x100x100 mm test specimens cast next to the tiles and kept at + 50 ° C for 5 or 8 hours.

_________________K0E_1___________K0E_2___________ RHPC cement (kg / m3) 250 250

Slag - "- 100 100

Silica 15 15

Activator - "- 8 8

Plasticizer - "- 4 4

Sand 0-1 mm 218 218

Sand 0-8 mm 1159 1159

Stones 6-12 mm 626 626

Water (% binder.) 34 34

Compressive strength (MN / m *) 5 h 13.0 17.0 8 h 26.0 37.6

Example 3

Facade concretes were prepared in six batches using three different material compositions, so that for each concrete mix was formed by both simultaneous mixing of all components (Experiments 1-3) and by stepwise mixing of components according to the invention (Experiments 4-6). The components were the same as in Example 2 and the mixing order of the components in Experiments 4-6 was that 78307 blast furnace slag, silica, activator, fine fill sand (0-1 mm), coarser sand (0-8 mm) and stones (8-16 mm) were mixed at the same time, 1 min after the addition of a plasticizer and 1 min after the addition of the softener dry RHPC cement · The amounts of components in the different experiments and the compressive strengths of the obtained concretes are shown in the following table in the same way as in Examples 1 and 2. as an average of a piece measuring 100x100x100 mm kept at + 40 ° C for 8, 15 or 24 hours.

_TEST 1 TEST 2 TEST 3 TEST 4 TEST 5 TEST 6 RHPC cement (kg / m3) 127 101 76 127 101 76

Slag - "- 108 133 160 108 133 160

Silica - "- 12 10 7 12 10 7

Activator% of the amount of slag 3 3.5 4 3 3.5 4

Plasticizer - "- 111111

Sand 0-1 mm (kg / m3) 220 220 220 220 220 220

Sand 0-8 mm 721 721 721 721 721 721

Stones 8-16 mm - "- 1010 1010 1010 1010 1010 1010

Water (% binder) 0.65 0.62 0.59 0.65 0.62 0.59

Compressive strength (MN / m *) 8 h 4.0 4.5 3.0 7.5 7.2 7.6 15 h 6.5 5.5 5.1 10.9 9.1 10.0 24 h 10 .3 10.0 10.5 15.2 14.5 16.0 E £ im ££ kki_4

The mortar was prepared in two batches using the same material components in the same mutual proportions, so that in one case (Experiment 1) all the components were mixed simultaneously and in the other case (Experiment 2) according to the invention in stages. The components of the mortar were the same as in the microconcrete of Example 1. The order of mixing of the components in Experiment 2 was that the blast furnace slag and silica were first mixed with water in an amount of 37.7% of the slag, 1 min then a plasticizer was added, 1 min after the addition of the plasticizer Akti activator, 1 min after the addition of the activator was added cement to the water slurried so that the amount of water added at this stage was 37.7% of the amount of cement, and finally 1 min after the addition of cement, sand was added. The amounts of the components and the compressive strengths of the obtained mortars during the curing process are shown in the following table in the same manner as in the previous examples. The compressive strengths in each case were obtained as the average of three measurements of a prism-shaped body with dimensions of 4x4x16 cm. Measurements were made after keeping the mortar for 2, 5 and 12 hours at + 50 ° C.

78307 _______________________________ ΚΟΕ_1 ___________ Κ0Ε_2 ___________ RHPC cement (g / dose) 250 250

Slag 250 250

Age 25 25

Activator% of slag 3 3

Plasticizer 1.2 1.2

Sand (g / dose) 1500 1500

Water (% binder.) 0.377 0.377

Compressive strength (MN / m *) 2 h 0 1.5 5 h 0 14.7 12 h 57.5 66.9

Esimerkki_5

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 stepwise according to the invention. For RHPC cement, blast furnace slag, activator and plasticizer, the components were the same as in Example 1. Sand or silica was not used for the particle boards, but instead the wood material was spruce. The mixing order of the components in Experiment 2 was that the blast furnace slag was first mixed with water, 1 min after which a plasticizer was added, 1 min after the addition of the plasticizer was added, 1 min after the addition of the activator was added cement dry and 1 min after the addition of cement wood fibers were added. After adding the wood fibers for 9 minutes, the resulting mixture was pressed into a sheet at a pressing pressure of 34 kg / cm * at a temperature of 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.

______________________________KOE_l_____K0E_2__________________ RHPC cement (g / dose) 240 240

Slag 2142 2142

Activator (¾) of the amount of slag 5 5

Plasticizer 1.7 1.7

Wood fibers (g / dose)

Water 762 762

Bending tensile strength (N / mm2) 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 stay together.

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 compositions to be prepared may further contain, in addition to silica, other pozzolans such as fly ash, peat ash or finely ground quartz sand.

Claims (9)

A process for preparing a curable composition in which a base material, such as sand, gravel and / or fibers, a binder consisting of some cement and part of a blast furnace, an activating agent, promotes the blast furnace hardening, so is alkali hydroxide, alkali carbonate, water glass or acai sulphate, any additives softened in water, may be characterized in that the cement and blast furnace slag are added to the mixture at different stages so that the blast furnace and activator are first mixed in water the cement is added at a subsequent stage. 2. A process according to claim 1, characterized in that cementing takes place no earlier than 5 seconds after the blast furnace slag and the activating agent have been mixed in the water. 3. A process according to claim 2, characterized in that the cement is added 15 s - 3 minutes after the blast furnace slag and the activating agent have been mixed in the water. 4. A process according to any one of the preceding claims, characterized in that the process produces a concrete mixture with sand as the base material, which is added to the mixture after the cement addition. 5. A method according to any one of claims 1-3, characterized in that wood fibers are used as the base material, the mixture being suitable for pressing to disk. Il