Geopolymer binders were prepared by adding each freshly NWG gradually to metakaolin in a mortar and mixed for 5 min, obtaining series of samples G1 and G2 which correspond to the geopolymers from S1 and S2 respectively. The NWG/MK mass ratio was kept constant at 0.83 obtaining a suitable workability for G1 and G2. The fresh geopolymer paste samples were rapidly molded into cylindrical PE-containers (20 mm in diameter and 40 mm in height), which were closed in order to hinder water evaporation. The samples were demoulded after 24 h and sealed in the plastic for 7, 14, 21, 28 and 56 days prior to measure the compressive strength.