Untersuchung der Frisch- und Festigkeitseigenschaften von nachhaltigem Zement (AAB)

Abstract

During my investigations, we studied the workability and strength development of mixes with slagbased,Alkali-Activated Binders (AAB) exploring the limits in term of w/b with different water to binder values. The main problems that prevent AAB to be currently used in construction field are its limited workability and the lack of durability testsThe umbrella term of alkali-activated binders is used for building products that represent an alternative to the Ordinary Portland Cement (OPC). The need in finding alternative to OPC is the high CO2 impact of clinker which represents the 95% of cement. Reducing the proportion of clinker in cement has adecisive influence on both fresh and final properties of the hardened material as well as a direct impacton the general cost on construction sites. Therefore, to find eligible substitute to OPC, an extensive study of its fresh and set properties should be made.The largest percentage of our AAB is composed by blast furnace slag, which is a by-product of steelproduction. Blast furnace slag, in combination with alkaline additives, Ca(OH)2 and Na2CO3, can be seenas just one representative of the possible alkali-activated binders (i.e., clay).In this thesis a preliminary work on AAB was extended achieving the influence of adding CaCl2 and PCE into the solutions. This work was the basis for our work. Following the circumstances already studied,the W/B value could be further reduced with the addition of CaCl2 and PCE. Another point that also appeared in the results was that PCE also has a decisive influence on the compactability and the associated compressive strength curve. In the end, it was also interesting to compare the compressive strengths with mortar CEM 32.5, where it was found that the values after 28 days were very similar.This fact shows that further research is definitely worth while.This scientific work is divided into an introduction, in which the current problems with cement as a binder are discussed. Then the materials which we have used, and the test methods employed are presented. In the result, the discussion and the conclusion the achievements of this theis will be described in detail. An appendix with the less relevant results is also presented.