Carlos Jesus

The use of supplementary cementitious materials (SCM) can enhance concrete durability. Fly ash (FA) has been used as SCM, especially in chloride-rich environments, but its availability is decreasing due to the closure of coal-fired power plants in EU countries such as Portugal. Glass powder (GP) emerges as a promising alternative because of its suitable chemical composition and wide availability. To evaluate concrete performance with high GP incorporation, specimens with different binder contents were produced using 50 % of SCM, either FA or GP. Mechanical and durability properties were evaluated, besides their environmental impact. Results showed that concretes with high GP incorporation are chloride-resistant and can be a potential substitute for FA. GP250-50, using 250 kg/m3 of cement, had lower chloride diffusion coefficients than the reference and FA concretes. At 90 days, the reduction was 91 % and 35 %, respectively. Furthermore, they had a significant CO₂ emission reduction (16 %), confirming their sustainable potential.

1. Climate change mitigation has driven the need to reduce the environmental impact of cement production, as clinker manufacturing remains one of the most carbon-intensive industrial processes worl...

The progressive phase-out of coal-fired power plants in Portugal has significantly reduced the availability of fly ash (FA) as a supplementary cementitious material (SCM), reinforcing the need for sustainable alternatives. Waste glass powder (WGP), characterized by its high amorphous silica content, has emerged as a promising candidate; however, most studies focus on ultrafine particles or isolated performance indicators, lacking an integrated technical, environmental, and economic assessment. This study evaluates cement pastes incorporating 25% WGP (by volume) with different particle size distributions, including fineness levels comparable to cement and FA. Mechanical performance, grinding energy demand, carbon footprint, and cost were systematically analyzed. The results indicate that WGP is technically viable as an SCM, with a median particle size (D₅₀) of approximately 48 µm providing the most balanced performance. Although finer particles enhance pozzolanic reactivity, the associated increase in grinding energy and economic cost offsets these gains. The findings demonstrate that optimizing particle size, rather than maximizing fineness, enables a technically robust and industrially realistic use of WGP. This approach supports circular economic strategies and contributes to the decarbonization of the construction sector by identifying an efficient replacement pathway for FA under resource-scarcity conditions.

As economies and industrialisation have grown, the foundry industry has produced a significant amount of ceramic mould casting waste (CMCW). To promote resource utilisation, this study investigates recycling CMCW as a partial replacement for lightweight aggregates in lightweight concrete. The durability of lightweight concrete mixes with varying CMCW content was studied using surface electrical tests, ultrasonic pulse velocity measurements, non-steady-state accelerated chloride penetration tests and carbonation resistance experiments. The results indicate that a lightweight concrete containing 80% CMCW exhibited greater density and uniformity, greater resistance to chloride ion penetration and better resistance to carbonation. These findings suggest that CMCW can be an effective and sustainable replacement for lightweight aggregate in lightweight concrete, improving durability and environmental performance. This research contributes to the development of sustainable construction materials and provides insights for the use of CMCW in the foundry industry.

Os materiais de pavimento rígido com betão drenante, após sua construção, sofrem um processo de degradação sob a ação do tráfego e das condições climáticas. Esse processo, que ocorre durante a vida útil do piso, pode ser mais lento se for bem construído e mantido. Assim, é fundamental que a caracterização mecânica do betão seja adequada para a sua aplicação. Assim, os ensaios de trabalhabilidade e densidade devem ser realizados em relação ao betão fresco. No caso do betão endurecido, são os ensaios de resistência à compressão e flexão, os ensaios de permeabilidade e os ensaios de resistência ao desgaste. O betão permeável pode ser uma solução de segurança bem-sucedida para chuvas fortes e inundações cada vez mais frequentes. Este estudo teve como foco a obtenção de um betão permeável otimizado, dentro do escopo das normas internacionais, por meio da análise do betão feitos com as mesmas relações A/C e tempos de vibração e os diferentes percentuais de agregado reciclado. Os resultados mostram a forte influência de ambos os parâmetros sobre a distribuição de porosidade e permeabilidade e a influência negativa de porosidades mais altas sobre a resistência. O betão com relação de 0,30 W/C e tempo de vibração de 40 segundos e 20% de agregado reciclado foi selecionado por seu desempenho mecânico superior. Rigid pavement materials with draining concrete, after construction, undergo a degradation process under the action of traffic and weather conditions. This process, which occurs during the life of the floor, can be slower if it is well constructed and maintained. Thus, it is essential that the mechanical characterization of the concrete is suitable for its application. Thus, workability and density tests must be carried out in relation to fresh concrete. In the case of hardened concrete, these are compressive and flexural strength tests, permeability tests and wear resistance tests. Pervious concrete can be a successful safety solution for heavy rains and increasingly frequent floods. This study focused on obtaining an optimized pervious concrete, within the scope of international standards, through the analysis of concrete made with the same W/C ratios and vibration times and different percentages of recycled aggregate. The results show the strong influence of both parameters on porosity and permeability distribution and the negative influence of higher porosities on strength. Concrete with a W/C ratio of 0.30 and a vibration time of 40 seconds and 20% recycled aggregate was selected for its superior mechanical performance.

The use of waste as supplementary cementitious materials (SCMs) in concrete is already widespread, with glass waste being an increasingly used option. The utilization of glass waste as a partial substitute for cement in small proportions has shown satisfactory outcomes. Nevertheless, substituting cement in high proportions requires further investigation. Experimental research was carried out on the mechanical and durability properties of concrete with the replacement of cement by glass powder (GP), at a high volume equal to 50%. Binder content (cement plus GP) varied from 300 to 500 kg/m³. The results are promising regarding the use of the high volume of GP in high-performance concretes. The specimens with 500 kg/m³ of binder (50% of which was GP-G250) achieved almost 55 MPa at 28 days. The specimen with the lowest resistance was G150, with 32 MPa. This result may be related to the high pozzolanic activity index of the used GP. The specimens with GP showed satisfactory performance regarding chloride migration, with diffusion coefficients always below those of the reference specimens. The G250 concrete showed a reduction of 58%. Regarding open porosity, concretes with 50% GP had a lower porosity than the reference concretes. The smallest reduction (21%) occurred in the G150 concrete. The reduction in porosity provided by the fineness of the GP may be the main cause of this high performance. Concerning capillary absorption, the GP concretes have a reduction that varies between 47% for G150 and 67% for G250. This fact may be related to the existence of a larger quantity of larger-sized capillary pores in the reference concretes.