Last week Daedalus presented his ‘Wet Cement’, a hygroscopic concrete which set but never dried out. A building made from it could creep rather than crack while settling into the soil. He is now taking the idea to extremes. His new, even more advanced cement does not merely creep under load; impact liquefies it completely. The result is the first thixotropic, re-usable concrete.

Anyone who has wiggled a foot in damp beach sand, stirring it into a mobile porridge, will understand the principle. A pile of sand can resist steady compression; but no such pile is fully compact. A few grains take all the load, leaving the rest essentially free and unloaded. Under sudden shock or stirring, the grains shift into a denser packing which occupies a smaller volume. The water around them, however, cannot shrink. The grains find themselves suspended in excess water under strong agitation. They slump into a strengthless fluidized mass.

So DREADCO's Thixocrete contains sand to carry the load, hygroscopic compounds and water-absorbing polymers to keep it wet, and a highly impure, mixed calciferous setting cement. As in ordinary cement, its crystals precipitate from the water to hold the sand grains in place. But the crystals, loaded with impurities and dislocations, are extremely brittle. They shatter to fragments under sudden shock or vibration, freeing the sand grains to fluidize in the water. Now small crystals preferentially dissolve in water whereas bigger ones crystallize from it (this is the ‘ripening’ action of a chemical precipitate). So when agitation ceases, new crystals slowly precipitate, and knit into a restraining matrix round the sand grains. The Thixocrete slowly sets again.

Thixocrete will transform the building trade. The new product will be made and transported not in slowly rotating mixers but in vigorously stirred tanks. Pumped into moulds or extruded along lines of bricks, it will set in minutes. Any mistake or design error will be easily rectified by a powerful vibrator or wrecker's ball, shocking the structure back to re-usable fluid Thixocrete. By the same token, a Thixocrete structure will be easily demolished. And an earthquake or bomb attack will not shatter it disastrously. Instead it will flow and slump. Falling pieces will be soft and plastic; escapers will wade to safety through them. And the deformed building will not be a hazardous, unstable ruin. It will slowly regain its strength.