DE1150613B - Anhydrite binder with iron-two-sulphate stimulator - Google Patents

Description

Anhydrite binder with iron-two-sulfate stimulator The invention relates based on an anhydrite binder, the activator of which contains two-iron sulfate.

It is well known that finely ground anhydrite binds water so slowly that that this reaction is practically meaningless for the setting process of a mortar, etc. is. The binding of water and the conversion of anhydrite to water-free anhydrite But dihydrate gypsum can be added by adding stimulants, i. H. various salts and Combinations of substances such as iron-two-sulfate, are so accelerated that the Anhydrite binder becomes a valuable binder. The setting process of the anhydrite takes place depending on the fineness of the grind and the type and quantity of the anhydrite to set stimulating stimulator in a longer or shorter time, in which a corresponding anhydrite content is converted into the dihydrate. When entering from Air to the mortar being processed, however, becomes the two-iron sulfate through oxidation converted to the less effective iron-three-sulfate, so that the setting process slows down will. The process of transformation can now only go on for as long as it has free water is present in the binder. Because the setting process is due to oxidation of the iron sulfate is slowed down, it happens that the water of the mortar before Completion of the setting process evaporates, while nevertheless more or less large Fractions of the anhydrite are present in the mortar without setting. If later the Mortar in turn absorbs water, e.g. B. by moistening an anhydrite screed, the stimulator begins to work again, and the setting process has continued until now Unbonded anhydrite components start again. The Screed its volume, so that damage in the form of cracks and bumps in the Surface can arise.

The invention aims to avoid this disadvantage in that the mass has an addition of an organic or inorganic reducing agent, reducing the iron-three-sulphate produced by the action of atmospheric oxygen works. As a reducing agent, for. B. amine phenol, calcium lignosulfonate, Sulphite waste liquor, copper chloride, tin chloride, sodium sulphite, sodium hydrosulphite are used will.

The advantage of the presence of the reducing agent in setting the Anhydrite binder consists in the fact that this is achieved by oxidation of the divalent iron resulting trivalent iron is reduced. So the bivalent iron remains Consistently preserved during the setting process, so the setting process is so strong is accelerated so that the setting is completed before the processed mortar can usually dry out. Since there is no longer any anhydrite that can be set is, a later wetting of the dried out mortar does not cause any further Setting process and consequently no increase in volume. The above Defects are thus avoided.

The addition of organic or inorganic reducing agents is up to 1%. A cash addition is in most cases inappropriate and can Cause interference.

The reducing agent can either be for the anhydrite or for the anhydrite certain aggregate; such as sand or dgL, or the stimulator itself or their mixtures be added. This means that the addition at the construction site or in the manufacturer's works the anhydrite or the exciter or in the delivery plant of the aggregate can.

The following example 1 is a known anhydrite mixture without reducing agents and in Examples, 2, 3 and 4 are anhydrite mixtures with reducing agents specified. The following is to determine the critical points of the setting process Test set-up was made: From the mixed anhydrite mixture with stimulator, according to example 1 no reducing agents or according to the other examples reducing agents contains, prisms of 4 - 4 - 16 cm in size have been produced. After 24 hours or 2, 4, 6, 8, 10, 12, 14 and 16 days are changes in length on the still damp Prisms have been measured. Farther are prisms after 2 and 7 days dried and their flexural strength and compressive strength determined.

The results given in the table below show the determined values of the mixtures according to the invention.

Example 1 A mixture of 1 part anhydrite and 3 parts standard sand 1.8% iron-two-sulphate activator is added. Example 2 A mixture like above, 0.25% sulphite waste liquor is added as a reducing agent.

Example 3 To a mixture such as Example, 0.15% sodium sulfite is added as a reducing agent. Example 4 0.2% tin chloride is added as a reducing agent to a mixture as in Example 1. The following table shows the evaluation based on the above-mentioned experimental set-up: Anhydrite binder with iron-two-sulphate stimulator example 1 2 1 3 4 Reducing agent 00/0 0.250 / 0 0.15010 0.2% Sulphite liquor! NaHS03 SnC12 Expansion after 2 days in mm .......... 0.37 0.25 0.12 0.33 Expansion after 4 days in mm .......... 0.61 0.40 0.21 0.52 Expansion after 6 days in mm .......... 0.74 0.48 0.26 0; 58 Expansion after 8 days in. Mm .......... 0.82 0.51 0.27 0.59 Expansion after 10 days in mm .......... 0.86 0.51 0.27 0.59 Expansion after 12 days in mm .......... 0.88 0.51 0.27 0.59 Expansion after 14 days in mm .......... 0.89 0.51 0.27 0.59 Expansion after 16 days in mm .......... 0.895 0.51 0.27 0.59 Flexural strength after 2 days in kg / cm2 ... 38 38.5 38 40 Flexural strength after 7 days in kg / cm2 ... 42.5 51.5 48.5 47 Strength increase in kg / cm2 ............... 4.5 13 10.5 7 Compressive strength after 2 days in kg / cm2 ...... 135.5 138.5 154 150 Compressive strength after 7 days in kg / cm2 ...... 189 205 214 215.5 Strength increase in kg / cm2 ............... 53.5 66.5 60 65; 5 Evaluation As the table shows, a prism made from a mixture according to Example 1 expands by 0.07 mm after the 7th day, ie a mixture of this type will expand if it dries out after the 7th day. Days and rewetting and has the above defects.

If, on the other hand, a reducing agent is used, as described in the examples 2, 3 and 4 is listed, then hear the expansion of the prism, as from the table can be seen after the 7th day. So such a body dries up after that 7. Days out and if it is moistened again, it no longer shows any expansion. The above-mentioned deficiencies are thus avoided.

Surprisingly, the table also shows that the bending tensile and compressive strength for the masses according to Examples 2 to 4 compared to the mass of Example 1 is significantly enlarged.

The mortar with reducing agent has two advantages: 1. hears the Expansion after the 7th day of setting the mortar, and 2. the strength is larger than that of the known mortar.

The drawing shows graphically the expansion of prisms according to Examples 1 to 4 as a function of time. Example 5 Standard test specimens (DIN 4208) made of anhydrite and standard sand were tested after storage according to standard. The same amounts of ferrous sulfate were used as stimulators in all samples, mixture 2 containing 0.20/0 tin chloride (SnCl2) as reducing agent and mixture 3 containing 0.250/0 calcium lignosulfonate as reducing agent. The strengths of the bodies with the reducing agents are in any case considerably higher than the strengths of the bodies of mixture 1 without reducing agents: 1 bending pressure hardness strength strength kg / cm ° kg / cm = kg / cmq Without reducing agent 33 157 955 With 0.2 "/ o SnC12 ...... 39 190 995 With 0.25% lignin calcium sulphate 41 202 1137 The reducing effect of calcium lignosulfonate is that it contains splittable sulphurous acid, which is a known reducing agent; How it can be proven in an experiment; it reduces trivalent iron to divalent iron. The reaction takes place in the following stages: The ferrous sulphate hydrolyses in an aqueous solution: FeS04 + H20: 2: Fe0 + H2SO4 The sulfuric acid produced reacts with the calcium sulphite from the sulphite waste liquor: CaS03 + H2S04 = CaS04 -! - H., 0 + S02 The released sulfur dioxide now reduces the ferric sulfate that may be present, whereby it is itself oxidized to sulfuric acid: Fee (S04) 3 + 2 H20 + S02 = 2 FeS04 + H2S04 The Fe0 produced by hydrolysis is returned to the FeS04 by the excess sulfuric acid formed . In summary, the following reaction occurs: Fee (S04) 3 + CaS03 + H20 = 2 FeS04 + CaS04 + H2S04 Aminophenol has approximately the same effect as the reducing agents listed above.

Example 6 Comparative tests, anhydrite excited with divalent and trivalent iron compounds The strengths of an anhydrite excited with divalent and trivalent iron compounds were determined, the amounts of salts added being the same in the first four cases, namely 2% of the anhydrite weight. The following were used: salt 1, ferrous sulfate (FeS04 * 7 1120) salt 2, ferric chloride (FeCl3 - 6 140) salt 3, ferroammonium sulfate FeS04 - (N1-14) 2S04 - 6 H20 salt 4, ferric ammonium sulfate Fe-2 (SO4) 3 - (NH4) 2S04 - 24 140. The mortar prisms 1: 3 with standard sand made with the same water factor of 0.378 have the following strengths: Type of salt bending tension pressure kg / cm ° - I kg / cm2 1 39 244 2 8 24 3 43 294 4 34 128 A second series of strength tests was set up so that the amount of iron contained in the salts (as an active substance) always remained the same in relation to the anhydrite. In addition, 0.6% potassium sulfate (K2S04) was added to all mixtures to further improve the strength. These mortar prisms made with the same water factor 0.378 and with standard sand 1: 3 have the following strengths: Type of salt Amount of salt Bending tension pressure % kg / cm- I kg / cm2 1 1.20 49 320 2 1.17 26 104 3 1.69 49 274 4 2.08 49 224 The results show that in both cases the divalent iron compounds give considerably better strengths than the trivalent iron compounds. It is advantageous to reduce any oxidized salts by adding reducing agents accordingly.

Claims (2)

PATENT CLAIMS: 1. Anhydrite binder with an activator made from two-iron sulfate, characterized in that the mass has an addition of an organic or inorganic Has reducing agent that acts on the resulting from the action of atmospheric oxygen Iron-three-sulfate has a reducing effect. 2. Anhydrite binder according to claim 1, characterized in that the addition of reducing agents is up to 1 %.