Supplementary cementitious materials (SCMs) can mitigate alkali-silica reaction by lowering the alkali metal concentration in the pore solution. This is a theoretical study on the applicability of a thermodynamic model (GEMS) and the empirical Taylor model to predict the required replacement level of portland cement (PC) by SCMs to achieve an alkali metal concentration below 300 mmol/L. The SCMs investigated are silica fume (SF), metakaolin (MK), fly ash (FA) and slag. The impact of the alkali content of the PC and the w/b ratio on the required replacement level is modelled and compared to experimental pore solution concentrations. Both models predict a similar impact of the SCM replacement level on the distribution of alkali between the pore solution, C–S–H and unreacted material. The thermodynamic model predicts little impact of the alkali content of PC and the w/b-ratio on the required replacement level, i.e., 20% SF, 20% MK, 40–50% FA and 60–70% slag. This is contrary to the Taylor model, which predicts that the replacement levels of FA and slag ranges from 7 to 58% when increasing the alkali content from 0.47 to 0.93% and from 80 to 10%, when increasing the w/b ratio from 0.3 to 0.9. The required replacement levels for SF and MK vary between 2 and 19% when increasing the alkali content from 0.47 to 0.93%, and from 40 to < 5% when increasing the w/b ratio from 0.3 to 0.9. The main difference between the two models is how they account for the uptake of alkali metals by the C–S–H.

Fiber-reinforced concrete (FRC) mixtures often face challenges in the fresh state, which are typically addressed using high Portland cement (PC) content or chemical admixtures, obstructing sustainability efforts in the construction industry. Therefore, this study employs advanced mixed design techniques, specifically particle packing models (PPMs), to proportion eco-efficient FRC mixtures with reduced cement content (<300 kg/m³) while achieving desirable fresh and hardened state properties. Twelve low-cement (LC) FRC mixtures, containing limestone filler (LF) as an inert material and a partial replacement for PC, were designed with a water-to-cement ratio of 0.64, incorporating two fiber types (polypropylene and steel) at varying contents (0.5% and 1.0% by volume) and lengths (38 mm and 50 mm). PPM-designed mixtures used two coefficients of distribution (q-factors: 0.21 and 0.26) and were evaluated for fresh (VeBe time, slump, and rheology) and hardened (compressive strength and flexural performance) state properties. Results show that PPM-designed FRC mixtures achieved up to 70% higher compressive strength and up to 64% greater flexural capacity compared to conventional mixes (i.e., American Concrete Institute—ACI), despite using 20% less cement. Additionally, PPM mixtures exhibited higher VeBe times (up to 24 s) and yield stress, reflecting improved packing density, while demonstrating shear-thinning behavior for practical applications (i.e., pumped or vibrated concrete). Finally, the findings demonstrate that PPMs enable the development of eco-efficient, low-cement FRC mixtures with similar or improved hardened state performance and reduced environmental impact.

In the present context of mitigating greenhouse gas emissions, interground portland-limestone cement (PLC) with elevated limestone filler (LF) replacement ratios (exceeding 15%) presents a feasible sustainable alternative, capable of diminishing clinker content. While LFs are known to modify the microstructure of concrete, the influence on ASR development has yet to be fully understood and requires further investigation. In this context, this work evaluates the effect of LFs replacement ratios between 15% and 25% on ASR development in concrete mixtures incorporating PLC. Analysis of expansion from accelerated mortar bar tests (AMBT) and concrete prism tests (CPT) indicate that increasing LF content from 15% to 25% does not substantially affect ASR-induced expansion. These findings underscore the viability of PLC as a sustainable construction material that does not compromise durability concerning ASR.