Concrete, the major construction material used in the civil industry worldwide, displays remarkable performance and economic benefits. Yet, it also presents a huge environmental impact producing about 7% of the global carbon dioxide (CO2). Given the rise of global warming concerns, studies have been focusing on alternatives to reduce the amount of Portland cement (PC), which is the least sustainable ingredient of the mixture, for example by adopting particle packing model (PPM) techniques. Although a promising alternative, there is currently a lack of studies regarding the efficiently use of PPMs to reduce PC without compromising the fresh and hardened properties of the material. This work appraises the influence of PPMs and advanced mix-design techniques on the fresh (rheological behaviour) and hardened (compressive strength, modulus of elasticity, porosity, and permeability) state behaviours of systems with reduced amount of PC, the so-called low cement content (LCC) concrete. Results show that is possible to produce eco-efficient concrete maintaining and/or enhancing fresh and hardened properties of the material. Nevertheless, further durability and long-term behaviour must be performed on LCC systems.

The construction industry is closely tied to economic development economies, and increasing demand also presents a significant contribution to environmental degradation. The construction industry’s impact to climate change is led by the 8% contribution from the production of concrete mixtures, more specifically, the production of cement. The combination of using advanced mixdesign techniques (e.g., particle packing models -PPM) and more sustainable ingredients poses as a promising alternative to overcome concrete environmental impact. However, there is a lack of studies regarding the fresh state difficulties arising from the aforementioned combination. Therefore, this work appraises the use of mobility parameters to overcome the fresh state issue raised when mix-designing mortar mixtures through PPM and with high volume of limestone filler. Twelve mixtures were developed with distinct cement content ranging from 150 kg/m3 to 320 kg/m3. To produce sustainable mortar, besides using PPM, cement content was replaced by limestone filler. Time dependent fresh state analysis was performed using mortar slump flow and a rheological profile. In the hardened states, the compressive strength, porosity, surface electrical resistivity tests were performed. The main findings of the project observed a strong correlation between mobility parameters and five distinct rheological parameters: flow behaviour parameter, high shear rate viscosity and shear stress, low shear rate viscosity and shear stress. Additionally, in the hardened state, a dilution parameter IPScement was used to appraise the dilution and filler effect of the mortar mixtures. The works highlighted a promising method to produce eco-efficient mortars.

Concrete, the second most used material in the world, presents great performance and economic benefits. Yet, it is often characterized by a brittle behaviour, low tensile strength, and toughness. Fibers are usually added to concrete to counteract its brittle behaviour, increasing ductility and toughness, controlling crack propagation and delaying concrete failure. However, their addition significantly worsens the fresh state performance of the material. To improve fresh state of the so-called Fiber Reinforced Concrete (FRC), conventional mix-design methods recommend the use of high paste content, which results in a significant increase of Portland cement (PC) content and raises the carbon footprint of the material. The latter is responsible for 8% of the global annual carbon dioxide (CO2) anthropogenic emissions. Given the current worldwide concerns on global warming, the construction industry is in a need to lessen the demand, and thus production of PC. Recent studies have been focusing on the use of advanced mix-design techniques (i.e. particle packing models- PPMs) along with Inert Fillers (IF) as an alternative to reduce PC content in concrete. However, the latter was not applied to conventional FRC. In this work, advanced mix design techniques (i.e. PPMs) are used to overcome the aforementioned issues and mix-proportion eco-efficient FRC with low cement content (< 300 kg/m3). Fresh (i.e. VeBe time, slump, rheological behaviour) and hardened (i.e. compressive strength, and flexural behaviour) state tests were performed on the proposed mixtures and compared with control high PC content (375 kg/m3) FRC mixes. Results show that PPM designed mixes presented higher minimum torque (yield stress) but quite comparable apparent viscositiy when compared to conventionally designed mixtures. Moreover, the flowability (i.e. VeBe time, and slump) tends to decrease as fiber content, length, and/or as the amount of fillers increase in the mixtures. In addition, PPM mixes exhibited a shear thinning behaviour following the Herschel-Bulkley model, which enables the design of FRC PPM mix-proportioned mixtures for applications requiring high torque regimes such as vibrated and/or pumped concrete. Finally, results show that the use of PPMs to mix proportion eco-efficient low cement FRC mixtures produced improved hardened (i.e. compressive strength, and flexural performance) state behaviour with lower environmental impact than conventional ACI designed FRC mixtures.