The civil construction industry consumes huge amounts of raw materials and energy, especially infrastructure. Thus, the use of eco-friendly materials is indispensable to promote sustainable development. In this context, the present work investigated low-carbon concrete to produce eco-friendly paving blocks. The binder was defined according to two approaches. In the first, a binary binder developed with eucalyptus biomass ash (EBA) and silica fume (SF) was used, in total replacement for Portland cement. In the second, the mixture of residues was used as a precursor in alkali-activation reactions, forming alkali-activated binder. The experimental approach was carried out using five different mixtures, obtained by varying the amount of water or sodium hydroxide solution. The characterization of this new material was carried out using compressive strength, expandability, water absorption, deep abrasion, microstructural investigation, and organic matter degradation potential. The results showed that the EBA-SF system has a performance compatible with Portland cement when used as an alternative binder, in addition to functioning as a precursor to alkali-activated concrete. The blocks produced degraded organic matter, and this degradation is more intense with the incidence of UV. In this way, the EBA-SF binder can be successfully used for the manufacture of ecological paving blocks with low carbon emissions.

The present study evaluated the mechanical behaviour of thin high-performance cementitious composite slabs reinforced with short steel fibres. For this purpose, slabs with 1%, 3% and 5% vol. of steel fibres were moulded using the slurry infiltration method. Fibres concentrated in the region subjected to traction during bending stresses. After curing for 28 days, all slabs underwent flexural testing. The slabs with 5% fibre showed significantly higher flexural strength, deflection and toughness compared to those of the control group without reinforcement. The dense fibre distribution, resulting from the production process, led to profiles with multiple random cracks in the region of failure of the slabs as the fibre content increased. The results of the statistical analysis showed the intensity of the correlation between the variables and revealed that the increase of the fibre content significantly influenced the parameters of mechanical behaviour (load, flexural strength, deflection, toughness and toughness factor). Images obtained by optical microscopy aided in understanding the fibre–matrix interface, showing the bonding surface between the constituents of the composite.

The high demand for concrete has triggered studies on the mitigation of Portland cement production impacts, such as greenhouse gas emissions and energy demands, in addition to enabling cost reduction. Partial replacement of cement with other materials has been employed as an alternative to minimize the damage caused by the cement industry. In this regard, it is necessary to use materials that efficiently replace cement clinker. This study uses waste generated from the production of metallic magnesium as a partial replacement for Portland cement. The substitution is aimed at reducing the amount of clinker used, as its production necessitates high energy consumption and results in emission of large quantities of CO2 into the atmosphere. The tailings were characterized via X-ray fluorescence (XRF), X-ray diffraction (XRD), scanning electron microscopy (SEM), and granulometric analysis. For evaluating the mechanical behavior and porosity, 25% of the cement (by mass) was replaced with tailings, and the resulting composite was molded into cylindrical specimens. After curing for 28 and 91 days, all specimens underwent compression testing. The results of the physical characterization showed that more than 65% of the tailing grain was lesser than 45 μm in size, which contributes to the packaging effect. In terms of the chemical and mineralogical composition, the tailing had high levels of calcium, and the predominant phases could be identified. The compressive strength of the mortar with substitution was higher than 40 MPa. The convergence observed between the results of the different characterization techniques demonstrates the efficiency of using the waste as a supplementary cementitious material.

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