Geopolymer-binder system for fire concretes, dry fire concrete mix containing the binder system and also the use of the mix

A dry alkaline-activated, cement-free binder composition for cement-free refractory concretes, composed of at least a mineral binder and a mineral activator, which form a curing geopolymer in a mixture with water,

• wherein a combination of at least two magnesium components that form with water an alkaline solution and thereby reactively form a geopolymer with the mineral binder, is contained as the mineral activator, and
• wherein the magnesium components comprise a different reactivity with regard to humidity in the air and with regard to the mineral binder,
• wherein the mineral binder comprises at least one of an amorphous aluminum silicate that is reactive with the mineral activator and forms Si—O—Al bindings and a binder that forms Si—O—Si bindings,
• wherein the amorphous aluminum silicate is selected from the group consisting of:
• metakaolin, tempered clay, brick dust, anthracite flue ash, and granulated slag,
• wherein the binder that forms Si—O—Si bindings is selected from the group consisting of:
• lime/sandstone powder, amorphous silica, and a combination of lime/sandstone powder and amorphous silica, and
• wherein the composition contains 80 to 99 wt.-% mineral binder.