http://repositorio.lnec.pt:8080/jspui/handle/123456789/1007787 2026-04-04T21:10:30Z 2026-04-04T21:10:30Z Benoliel M. A. Pacheco, J. Silvestre, J. Martins, I. M. Brito, J. http://repositorio.lnec.pt:8080/jspui/handle/123456789/1018981 2025-11-27T12:25:04Z 2025-01-01T00:00:00Z

Life cycle assessment of ready-mixed concrete: paths towards more sustainable practices Benoliel M. A.; Pacheco, J.; Silvestre, J.; Martins, I. M.; Brito, J. Concrete is the second most used material on Earth after water and its large-scale production generates heavy environmental burdens. Effective mitigation of this stress involves understanding the key factors contributing to it. In this work, a cradle-to-gate life cycle assessment was conducted on ready-mixed concrete (RMC) produced in two Portuguese plants. It was found that the extraction and processing of raw materials dominates most environmental impact categories, especially those relating to climate change, with cement production governing the overall global warming potential (GWP). Analysis of several short- to medium-term scenarios to reduce carbon dioxide emissions, as envisioned by the European Cement Association and the Portuguese cement industry, indicates a possible reduction of about 30% in GWP. Of this reduction, 20% is attributed to a decrease of up to 60% in the clinker content of the cement used to produce RMC, while most of the remaining 10% results from the natural carbonation of cement (a process already occurring naturally in the use stage of concrete).

2025-01-01T00:00:00Z Ribeiro, A. C. Custódio, J. Real, S. http://repositorio.lnec.pt:8080/jspui/handle/123456789/1018826 2025-11-27T12:22:33Z 2025-06-13T00:00:00Z

Influence of alkali on the drying shrinkage of cement pastes Ribeiro, A. C.; Custódio, J.; Real, S. Concrete shrinkage remains a relevant topic of study due to the increased use of high-performance concrete. Understanding shrinkage mechanisms is essential for developing non-shrinking concrete and reducing cracking problems. During concrete curing, substantial quantities of alkalis dissolve in the pore solution, and their influence on shrinkage is not fully understood. This paper gives further insight into the role of the alkalis, by monitoring the length changes and mass variations of hardened cement pastes with pore structures saturated with solutions containing potassium hydroxide (KOH) in the presence or absence of a shrinkage reducing admixture (SRA). The method used does not include the effects of the alkalis on the formation of the pore structure, but it has the advantage of isolating the individual influence of KOH and SRA on shrinkage. The results are consistent with a reduction of shrinkage for increased alkali concentrations and suggest an explanation for contradictory experimental results reported in the literature.

2025-06-13T00:00:00Z Custódio, J. Costa, D. Santos Silva, A. Miquithaio, A. http://repositorio.lnec.pt:8080/jspui/handle/123456789/1018824 2025-11-27T12:22:19Z 2025-03-12T00:00:00Z

Diagnosis and prognosis of internal swelling reactions in Cahora Bassa dam, Mozambique – a case study Custódio, J.; Costa, D.; Santos Silva, A.; Miquithaio, A. In recent decades, a significant number of large concrete infrastructures with deterioration problems related to alkali–silica reaction (ASR) and delayed ettringite formation have been identified worldwide. Currently, owing to phenomenological and assessment complexities, it is still difficult to provide recommendations for preventing ASR damage in new structures involving certain aggregates, and to perform a complete assessment of the actual condition of an affected structure and an accurate prediction of its future deterioration. The aim of this paper is to contribute to the ongoing discussion of this topic and presents some of the work performed on the diagnosis and prognosis of internal swelling reactions in concrete from the Cahora Bassa dam, in Mozambique. The Cahora Bassa dam, built between 1972 and 1975, is part of a hydroelectric scheme located on the Zambezi River. This paper includes a very brief overview of the information available on the concrete and its constituents at the time the dam was built, and succinctly presents an analysis of some of the results obtained in the laboratory test campaign (e.g. microstructural analyses, chemical analyses and expansion tests) performed on cores extracted from the structure in 2017 and on the aggregate used in the dam’s concrete.

2025-03-12T00:00:00Z Custódio, J. Mata, J. Serra, C. Ribeiro, A. C. Tavares de Castro, A. Batista, A. L. http://repositorio.lnec.pt:8080/jspui/handle/123456789/1018807 2025-11-27T12:21:14Z 2025-02-02T00:00:00Z

Insights into the Diagnosis and Prognosis of the Alkali–Silica Reaction (ASR) in Concrete Dams, Highlighting the Case of the Demolished Alto Ceira Dam in Portugal Custódio, J.; Mata, J.; Serra, C.; Ribeiro, A. C.; Tavares de Castro, A.; Batista, A. L. Over the past few decades, a significant number of large concrete structures with deterioration problems related to the alkali–silica reaction (ASR) have been identified in Portugal and worldwide. Assessing the condition of ASR-affected concrete dams involves both diagnosis and prognosis. Diagnosis evaluates the structure’s current state, while prognosis predicts deterioration and safety implications. This is key to estimate the period during which the structure will effectively perform its function, and essential for the timely and cost-effective planning of the necessary mitigation, rehabilitation, and/or reconstruction works. This article aims to contribute to the ongoing discussion of this topic by the scientific and technical community and, therefore, presents the methodology adopted to assess the condition of a severely ASR-affected concrete dam in Portugal, the Alto Ceira dam, in which the concrete was produced with susceptible to ASR quartzitic aggregates and that was decommissioned and replaced by a new one in 2014. The article provides a brief review of the diagnosis and prognosis of the ASR in concrete dams, presents and analyses the results from laboratory testing (including chemical, microstructural, physical, mechanical, and expansion tests), in-situ testing, structural monitoring systems, visual inspections, and numerical modelling, aiming at assessing ASR impacts and evidencing the utility of the reported methodology on the appraisal of ASR-affected structures.

2025-02-02T00:00:00Z