FR2520000A1 - Colloidal powder for grouting(s) used to reinforce earth - made by drying and milling of mixt. contg. clay, marl, and calcareous rock, then adding water and cement to obtain pumpable suspension - Google Patents

Abstract

The powder is obtd. by first making a dry mixt. from clay, marl, and calcareous rock or chalk, so the mixt. contains by wt. 74-80% CaCO3 present as calcite, and 12-18% SiO2 present as hydrated aluminium silicate. The mixt. is dehydrated at 90-200 deg.C; and is then milled to a particle size of less than 0.1 mm for 90% of its constituents, to obtain the desired powder. The powder is made into a colloidal suspension by adding 600-1200 litres of water per kg of powder, and then adding cement to the suspension. The powder can be used to replace a pure clay.

Description

The invention relates to Public Works
Due to its granulometry, its high resistance and the difficulties of its preparation, the concrete is not used in a certain number of applications or it is a question of treating the ground with a view to its perforation, its sealing by injection , its consolidation or its replacement.

Multiple products are then used, among which the stabilized cement grouts which are generally constituted by a colloidal clay mud to which cement is added and in general a filler of the sand or fly ash type.

The hydration of the clay is a delicate operation because, if the cement is added too early, the hydration of the clay is blocked by physical and chemical phenomena which can give rise to fioculation, formation of lumps, decantation.

 The object of the invention is to define the composition of a new product intended to replace the previous clay in the form usually encountered of a fairly pure product.

The new product, on the contrary, results from a dry mixture of clay, marl and limestone in well defined proportions which are:
74 to 80% CaC03 in the form of calcite
I2 to 18% SiO2 in the form of hydrated alumina silicate
the remainder being formed from the usual aluminum and iron oxides and
various impurities
This mixture is then dehydrated between 90 degrees and 200 degrees, then finely ground so that more than 90% of the elements are less than 100 microns.

 In the preceding mineralogical composition the percentages are expressed by weight of the final powder obe, the various -minerals being able to - at the origin being as well in clay as limestone or marl.

The product offers the following qualities:
Its hydration is very easy because, chemically, the high amount of CaCO3 buffers a pH of 8àIO. The ph can also be adjusted using alkalis.

Now this ph is the one that causes the clay to fluidify most quickly
The fine grains of limestone also prevent agglomeration of the clay and facilitate its hydration. The hydration is very fast and the cement can be added very quickly.

The final mechanical strengths are very high compared to similar grouts containing the same quantities of minerals but introduced according to the usual methods and successively.

As an indication we will give two compositions of use per cubic meter of final grout and their properties:
First composition of use:
880 kg of product
6I8 liters of water
220, kilograms of cement 1 hour to 2 hours pumping time
25 to 30 bar resistance to crushing at 7 days
Second composition of use:
640 kg of product
725 liters of water
160 kilograms of cement
3 hours to 5 hours pumpability time
4 to 7 bar resistance to crushing at 7 days
Multiple formulas can be used by adding in particular delay or acceleration adjuvants. For example, the first previous composition can be stiffened by adding only 5 liters of sodium silicate at 35-37 degrees balsam so as to make taken in less than 5 minutes.

 In all cases, the quantity of water used for hydration must remain between 600 and 1200 liters per tonne of product J. this dosage makes it possible to obtain a manageable paste which does not decant after adding cement.

Claims (2)

 I. Semi-finished product of the calcareous clay powder type intended for the colloidal suspension of soil treatment grout, characterized by a final mineralogical composition by weight of 74 to 80% of CaC03 and I2 to I8 of SiO2 in the form respectively calcite and hydrated alumina silicate from a mixture of clay, marl and limestone or chalk, dehydrated between 90 and 200 degrees and finely ground to less than 100 microns for 90% of elements.  2. Process for implementing the powder defined in claim 1, characterized by the hydration of this powder at the rate of 600 to 1200 liters of water per kilogram of powder before adding cement.