<p>A hydratable cementitious composition which includes a blend of; (i) cement and/or; (ii) ground granulated blast furnace slag; and (iii) wastepaper sludge ash which is produced by heating wastepaper sludge to a combustion temperature in the range 850° C. to 1200° C. for a dwell time in the range 1 to 60 seconds.</p>
