Method for obtaining a geopolymeric binder allowing to stabilize, solidify and consolidate toxic or waste materials

In a method of consolidating toxic wastes for long-term disposal thereof, comprising reacting said wastes with a binder, the improvement wherein

• said binder is a geopolymeric compound in powder form comprising
• (a) 100 parts by weight of alumino-silicate oxide (Si.sub.2 O.sub.5,Al.sub.2 O.sub.2) having the Al cation in (IV-V) coordination as determined by MAS-NMR analytical spectroscopy for .sup.27 Al,
• (b) 48-72 parts by weight of potassium disilicate K.sub.2 (H.sub.3 SiO.sub.4).sub.2 or a mixture of (i) 35-40 parts of potassium silicate K.sub.2 O, 3SiO.sub.2, 3H.sub.2 O, (ii) 7-15 parts of potassium hydroxide KOH which is at least 90% anhydrous, and (iii) an amount of amorphous silica up to 65 parts, and
• (c) 50-70 parts of vitreous basic silicate, composed partly of at least one of gehlinite, akermanite and wollastonite,
• said geopolymeric compound providing a compressive strength greater than 15 MPa after only four hours at 20.degree. C. when tested in a standard mortar with a binder/sand ratio of 0.38, in the substantial absence of Portland cement, and
• mixing of said toxic waste with said geopolymeric compound is carried out in the absence of water, followed by adding water so as to provide a water/binder ratio lower than 0.27, thereby obtaining hardening and capture of said toxic waste within a resultant geopolymeric matrix in the substantial absence of Portland cement.

In a method of consolidating toxic wastes for long-term disposal thereof, comprising reacting said wastes with a binder, the improvement wherein

• said binder is a geopolymeric compound in powder form comprising the following reactive constituents:
• (a) an alumino-silicate oxide (Si.sub.2 O.sub.5,Al.sub.2 O.sub.2) in which the Al cation is in (IV-V) coordination as determined by MAS-NMR analytical spectroscopy for .sup.27 Al,
• (b) a disilicate of sodium and/or potassium (Na.sub.2,K.sub.2)(H.sub.3 SiO.sub.4).sub.2 ;
• (c) a silicate of calcium
• the molar ratios between the three reactive constituents being equal to or between ##EQU4## where Ca.sup.++ designates the calcium ion belonging to a weakly basic silicate of calcium whose atomic ratio Ca/Si is lower than 1,
• said geopolymeric compound providing a compressive strength greater than 15 MPa after only four hours at 20.degree. C. when tested in a standard mortar with a binder/sand ratio of 0.38, in the substantial absence of Portland cement, and
• mixing of said toxic waste with said geopolymeric compound is carried out in the absence of water, followed by adding water so as to provide a water/binder ratio lower than 0.27, thereby obtaining hardening and capture of said toxic waste within a resultant geopolymeric matrix in the substantial absence of Portland cement.