Page 50 - Demo

CONCRETE TECHNOLOGY48 CPI %u2013 Concrete Plant International %u2013 4 | 2025 www.cpi-worldwide.comThe results show that the combination of accelerating admixtures and elevated curing temperature in the initial phase after production (here = 8 hours) leads to a significantly accelerated early strength development for mortar compositions with a clinker content of up to 40 wt.-%, provided the granulometry of the slag is adjusted accordingly. Compressive strength values above 15 MPa after 8 hours, which is the standard early strength required for demoulding in the production of tunnel segments, can thus be achieved with significantly CO2-reduced mix compositions.Summary The results of the investigations show that granulometric optimization of the binder in combination with accelerating admixtures provides highly suitable solutions for the development of eco-efficient mortars with low clinker content and high early strength. Since the binder system, and particularly the w/b-ratio, is primarily responsible for strength development in concrete, these findings can be readily transferred from mortar to concrete.Mortar compositions with a maximum clinker content of 40 wt.-% demonstrate compressive strengths exceeding 15 MPa after 8 hours, as a result of optimized slag granulometry, the use of accelerating admixtures, and elevated curing temperatures during the first hours after casting. This value corresponds to the standard early strength required for demoulding during precast tunnel segment (tubbing) production. Therefore, such optimized mix designs make it possible to significantly reduce the CO2 emissions of the mixes while maintaining comparable technical performance. nReferences[1] Stindt, J.; Forman, P.; Mark, P. Influence of Rapid Heat Treatment on the Shrinkage and Strength of High-Performance Concrete. Materials 14 2021. 4102.[2] Adu-Amankwah, S.; Bernal, S. A.; Black, L.: Influence of component fineness on hydration and strength development in ternary slag-limestone cements. RILEM Technical Letter 4 2019. pp. 81-88.[3] Berodier, E.; Scrivener, K.: Understanding the Filler Effect on the Nucleation and Growth of C-S-H. Journal of American Society 97 2014. pp. 3764-3773.[4] Birki, Y.; Zajac, M.; Mohsen, B. H.; Scrivener, K.: Impact of limestone fineness on cement hydration at early age. Cement and Concrete Research 147 2021. 106515.[5] John, E.; Matschei, T.; Stephan, D.: Nucleation seeding with calcium silicate hydrate %u2013 A review. Cement and Concrete Research 113 2018. pp. 74-85.[6] Hallet, V.; De Belie, N.: Pontikes. Y.: The impact of slag fineness on the reactivity of blended cements with high-volume nonferrous metallurgy slag. Construction and Building Materials 257 2020. 119400.[7] Zhou, Y.; Zhang, Z.: Effect of fineness on the pozzolanic reaction kinetics of slag in composite binders: experiment and modelling. Construction and Building Materials 273 2020. 121695.[8] Lothenbach, B.; Le Saout, G.; Gallucci, E.; Scrivener, K. Influence of limestone on the hydration of Portland cements. Cement and Concrete Research 38 2008. pp. 848-860.[9] Zajac, M.; Rossberg, A.; Le Saout, G.; Lothenbach, B. Influence of limestone and anhydrite on the hydration of Portland cements. Cement and Concrete Composites 46 2014. pp. 99.108.[10] Schack, T.; Haist, M.: Performance assessment of eco-efficient concrete with ternary blended cementitious materials considering the effect of binder component fineness. Case Studies in Construction Materials 20 2024. e03154.[11] European Cement Research Academy: TR-ECRA-106/2009 ECRA CCS Project - Report about Phase II 2009.[12] Br%u00e4u, M.; Ma-Hock, L.; Hesse, C.; Nicoleau, L.; Strauss, V.; Treumann, S.; Wiench, K.; Landsiedel, R.; Wohlleben, W.: Nanostructured calcium silicate hydrate seeds accelerate concrete hardening: a combined assessment of benefits and risks, Archives of 599 Toxicology 86 2012. pp. 1077-1087.[13] Pedrosa, H.C.; Reales, O.M.; Reis, V.D.; Paiva, M.D.D.; Fairbairn, E.M.R.: Hydration of Portland cement accelerated by C-S-H seeds at different temperatures, Cement and Concrete Research 129 2020. 105978.[14] Li, X.; Bizzozero, J.; Hesse, C.; Impact of C-S-H seeding on the hydration of slag blended cement. Cement and Concrete Research 161 2022. 106935.[15] https://www.dyckerhoff.com/de/next-base (Letzter Zugriff: 27.04.2025)[16] Schack, T.; Strybny, B.; Haist, M. (2024) Improving the Early Age Strength of Eco-Efficient Mortar with Low Clinker Content Considering Binder Granulometry and Chemical Additives. Materials 17(18). 4509.[17] DIN EN 197-1:2011-11: Cement - Part 1: Composition, specifications and conformity criteria for common cements. Beuth, Berlin, 2011.[18] Dyckerhoff GmbH [ed.] Dyckerhoff Mikrodur%u00ae %u2026 vom Feinsten. Dyckerhoff GmbH, Product marketingFig. 4: Compressive strength after 8 hours as a function of clinker content and curing temperature (20%u00b0C to 60%u00b0C). Compressive strength at 8 h [MPaClinker content [m.-%]