From microstructural formation to early-age creep and relaxation

E.A.B. Koenders

Technische Universität Darmstadt, Germany
Institute of Construction and Building Materials

How are early age creep and relaxation linked to the microstructural formation of cementitious materials? This fundamental and extremely complex question has already being researched for many decades by considering various (combined) actions arising from chemical, physical and mechanical changes of the hardening cement-based microstructure. The current paper is prepared as part of a special session during the RILEM Week 2018, which was dedicated to the research work done by Professor Klaas van Breugel. It gives just a very brief impression of his research work done in the field of creep and relaxation, temperature development and early age cracking, and microstructure formation. The two most fundamental topics, on early age creep and relaxation, and its relation with microstructural formation, reflect his significant contributions in this field, represented by the cutting-edge results reported in two of his major deliverables, which are a TU Delft report on early age relaxation and his PhD thesis, which is on simulation of hydration in hardening cementitious materials. Based on this, a further development on the underlying mechanism is proposed for early-age stress and strain development, leading to a unified vision on relaxation, autogenous shrinkage and creep, which is confirmed by evidence achieved from experimental data on creep and relaxation from creep- and TSTM-tests.

Key words: Creep, relaxation, microstructure, autogenous shrinkage