Ceramics-Silikáty 55, (4) 362 - 372 (2011)

This research dealt with metakaolinite geopolymers of various textures controlled by the addition of a quartz sand in a range of 0–93 wt.%. Mechanical properties were measured to quantify the impact of changing composition on the specimen structure, aimed to the mixture optimizing. The compressive and flexural strengths, Young’s modulus and frost resistance were compared with structure parameters determined by mercury porosimetry. The resulting relations are discussed revealing varying control plots modifying the strengths and frost resistance. The existence of an interfacial transition zone caused by the interaction between the quartz aggregates and the geopolymer was verified to be positively affecting the composite strengths. It has been found that the material of the best mechanical properties underwent the maximal densification of the sand aggregates causing the approaching on the shortest distance with the condition of entirely coating by geopolymer gel. In this manner, the highest interface participation is represented on the composite structure. Besides the high strength, freezing resistance was conditioned by an at least 20% content (within the total porosity) of 1-8 μm large mesopores.