Rational design of cement composites containing pozzolanic additions

- New approach to dosing of pozzolanic additions in concrete based on the phase composition of pozzolana was proposed.
- Waste ceramics can be effective cement substitute if its composition is taken into account.
- Behavior of the amorphous portion of waste ceramics is comparable to metakaolin.

In cement composite design, pozzolanic additions (PAs) are primarily considered as mass equivalents of cement to be replaced. This paper presents a modification to the traditional approach that takes into account the amounts of active and passive components in a particular PA. The practical application of the modified design method is demonstrated for a red-ceramic residue from brick production. First, the residue is physically and chemically characterized via particle size distribution analysis, X-ray fluorescence spectroscopy, the Chapelle test of pozzolanic activity, and quantitative X-ray diffraction analysis to obtain detailed information on its activity. Subsequently, the effective pozzolanic properties of the residue are assessed by investigating the lime hydrate-ceramic system using solid-state magic angle spinning 27Al and 29Si nuclear magnetic resonance spectroscopy analysis and compressive strength measurements. Finally, cement composites containing different dosages of the ceramic residue are designed using the modified approach and their mechanical and durability properties are compared with reference samples prepared via the conventional method. The experimental results show an improvement of up to 35% in compressive strength and a significant gain in freeze/thaw resistance using the proposed approach.