For the 20th time a conference about the rheology of building materials took place on March, 1st, 2011 in Regensburg, including a laboratory workshop on March, 2nd. Nearly 200 researches from all over the world visited the historical world heritage city Regensburg to learn about the latest results at field of rheology of constructing materials, like mortar or fresh concrete. Speakers from Poland to Newfoundland, and visitors from more than 12 countries, proofed the label of an international conference. The 19 presentations given in two sessions where focused onto the interaction of cement and additives, computer based flow simulation, ultra high performance concrete and innovations in measurement instruments.