Shi, C., Qu, B., Provis, J.L.: Recent progress in low-carbon binders. Provis, J.L., Van Deventer, J.S.J.: Geopolymers and other alkali-activated materials. Zhang, P., Zheng, Y., Wang, K., Zhang, J.: A review on properties of fresh and hardened geopolymer mortar. Komkova, A., Habert, G.: Environmental impact assessment of alkali-activated materials: examining impacts of variability in constituent production processes and transportation. As such, it may contribute towards establishing new model code for new binders in the future.

The methodology of binder design as well as performance validation by combining microscopy with macroscopic properties was found to be quite efficient. Application of these binders in concrete within the framework of the current model codes thus is not allowed. In contrast, the bending strength and Young’s modulus developed either faster (CSH) or slower (NAS) than the compressive strength, leading to an over- or underestimation of these properties predicted on the basis of the 28-day strength in the structural design codes. The 28-day strength is only 2/3 of the predicted ultimate strength. The three types of binders have a similar slow compressive strength development, although they have very different 28-days strengths. Microstructural analysis showed furthermore also very similar total porosity and pore size distribution but three different reaction products: CSH with some Na and Al for the activated slag, CASH with a high amount of sodium for the activated slag/fly ash blend and NAS for activated metakaolin. Mortars were designed for similar paste volumes. In this paper, the microstructures and the relation to performance is investigated from three binder systems, based on the currently most common precursors.

The performance of these new binders thus have to be determined. Structural design codes then may not be valid anymore. Although silicate binders from side streams are very attractive to use in terms of CO 2-reduction and primary material reduction, their performance may deviate from that of already accepted cements.

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