National Laboratory for Civil Engineering

Reinforced concrete (RC) structures are well-known for their high durability; however, they remain vulnerable to natural hazards and extreme events that can impact their performance over time. In aggressive environments, there is a high likelihood of increased maintenance, rehabilitation, and repair actions that constitute a significant portion of the total lifecycle spending. Monitoring systems have been implemented during the last decades to collect periodically or continuously essential data about the durability performance of the structures in real operation. However, the effectiveness of these systems is impacted by sensor efficacy, influenced in turn by environmental factors, sensor durability, and power outages, leading to intermittent or permanent data gaps. This study proposes a methodology to address the problem of missing data of a Structural Health Monitoring (SHM) system, specifically aiming to provide more accurate and continuous information from concrete resistivity and temperature sensors to support the early detection of corrosion. The proposed methodology was applied to a repaired RC structure with over fourteen years of data, where significant gaps in the measurements were present. The approach combines several techniques to fill these gaps: deep machine learning for air temperature, generalized linear models for concrete temperature, and pattern recognition for concrete resistivity. To the best of the authors’ knowledge, this is the first time a methodology has been proposed for imputing missing data from resistivity sensors in SHM systems, which are increasingly being implemented. This approach is innovative and offers potential benefits for SHM system managers, providing more information on long-term sensor data that could aid in early corrosion detection and maintenance planning. The application of the proposed methodology to a real case study indicated a successful imputation of 43.4% of missing data although some challenges persist for sensors located in areas characterized by high measurements variability.

The main objective of this study was to evaluate the mechanical properties of three thermal-modified wood species when exposed to weathering in urban and maritime/industrial environments and their durability against subterranean termites. The wood species studied were Maritime pine, ash, and blackwood acacia. All wood samples were exposed to two different environments (urban and maritime/industrial) for 24 months. Then, its physical and mechanical properties were evaluated (modulus of elasticity (MOE), modulus of rupture (MOR), compression strength (CS), and modulus of compression (MOC). Thermally modified woods revealed a lower density, which could explain the loss of MOE and MOR. In compression, no significant changes were verified. The weathered samples showed changes in mechanical properties, mostly verified in MOE and MOR, where some decreases were reported in both locations. Tests were performed to evaluate biodegradation and the resistance of all wood samples to subterranean termites. The grade of attack (≈4) and termite survival rate were similar in all wood species (above 75% and lower than 80%), except for modified acacia (59%), which could indicate that thermal modification increased toxic substances. The cellulose degradation was reflected in FTIR-ATR and Py-GC/MS in natural and thermally modified woods. Py-GC/MS showed a decrease in levoglucosan, while lignin suffered some modifications with slight changes in monomeric composition reflected by the reduction of the S/G ratio. No changes were found between the two environments, and thermal modification did not give extra protection against termites and weathering.

The RILEM TC 281–CCC ‘‘Carbonation of concrete with supplementary cementitious materials’’ conducted a study on the effects of supplementary cementitious materials (SCMs) on the carbonation rate of blended cement concretes and mortars. In this context, a comprehensive database has been established, consisting of 1044 concrete and mortar mixes with their associated carbonation depth data over time. The dataset comprises mix designs with a large variety of binders with up to 94% SCMs, collected from the literature as well as unpublished testing reports. The data includes chemical composition and physical properties of the raw materials, mix-designs, compressive strengths, curing and carbonation testing conditions. Natural carbonation was recorded for several years in many cases with both indoor and outdoor results. The database has been analysed to investigate the effects of binder composition and mix design, curing and preconditioning, and relative humidity on the carbonation rate. Furthermore, the accuracy of accelerated carbonation testing as well as possible correlations between compressive strength and carbonation resistance were evaluated. One approach to summerise the physical and chemical resistance in one parameter is the ratio of water content to content of carbonatable CaO ( w /CaO reactive ratio). The analysis revealed that the w /CaO reactive ratio is a decisive factor for carbonation resistance, while curing and exposure conditions also influence carbonation. Under natural exposure conditions, the carbonation data exhibit significant variations. Nevertheless, probabilistic inference suggests that both accelerated and natural carbonation processes follow a square-root-of-time behavior, though accelerated and natural carbonation cannot be converted into each other without corrections. Additionally, a machine learning technique was employed to assess the influence of parameters governing the carbonation progress in concretes.

In alluvial river reaches, flood events are characterized by the inundation of the adjacent land near the main channel course. In these compound channel or overbank configurations, the flow structure is much more complex than in a single channel due to interactions between faster and deeper flow in the main channel and the slower and shallower flow in the lateral floodplains. Moreover, the interactions may be enhanced by the floodplain roughness as this region is usually covered by vegetation. The present study aims at understanding the streamwise flow development and the turbulent flow structure in such conditions. An experimental campaign was carried out in a laboratory compound channel. An iterative procedure to obtain the uniform flow was followed by successive change of the discharge distribution and downstream levels. In total, nine uniform flows were studied, namely (i) six with floodplains made of polished concrete and (ii) three with synthetic grass covering the floodplains. The boundary and mixing layers are presented and the effects of the shallowness and of the floodplain roughness on main flow mechanisms are assessed.

This research aims to experimentally characterize cooling, clogging and jamming of a dry granular flow in a chute partially obstructed by a stopping wall with two slits adjacent to the side walls. We ensemble‐average velocities, determined with Particle Tracking Velocimetry, and its fluctuations, to compute mean flow and granular temperature fields. Full chute‐wide jamming is triggered by the formation of stable arch‐like clogging structures in front of the slits. The statistical distribution of the clogging instant is not heavy‐tailed, which indicates that clogging occurs only when the flow through the slits is liquid‐like. An upstream‐progressing jamming wave eventually forms, similar to that observed in fully obstructed chutes. There is no triple point anywhere, since the flow cools down to a granular liquid before jamming. We identified three main stages of jamming wave propagation. The initial buildup is characterized by high values of the upstream Froude number, slow progression, and transformation of kinetic into potential energy. This occurs with significant granular head losses, as particles attempt to flow over the jam. In the second stage, accretion becomes dominant, characterized by smaller head losses and, consequently, higher values of the jamming wave celerity. In the third stage, the jamming wave propagates against a cooler but faster flow that pushes against the jam, slightly increasing the wave strength. Accretion is the main mechanism of jammed mass increase, justifying a further increase of wave acceleration. The macroscopic aspects of the jamming wave dynamics can be described, as a first approximation, by shallow‐water theory.

Soundscapes have been a growing tool in managing urban sounds through the ISOs series 12913 parts 1 to 3. The ISO/TS 12913-2: 2018 standard (Acoustics - Soundscape - Part 2: Data collection and reporting requirements) provides technical specifications and protocols, as well as a questionnaire for soundscape characterization with perceptual attributes based on soundscape studies. However, such attributes are provided only in the English language, which raises questions about the applicability and reliability of these attributes in regions where English is not the mother tongue. To address this gap, the Soundscape Attribute Translation Project (SATP), an international collaboration with soundscape researchers was established with the aim of validating the translation of perceptual attributes for soundscape assessment in different languages and geographic regions as a way of disseminating and promoting their widespread use, both in academia and in practice. This article presents the results of the work, realized in Brazil and Portugal, contributing to the translation of the perceptual attributes for soundscape assessments from English into Portuguese language through a cross-cultural study.

This study presents a laboratory investigation on the susceptibility of suffusion in soil samples collected from a very old earth dam. The dam, rebuilt around 1800, is composed of two earth fills and lacks a clay core or filtration components, making it vulnerable to internal erosion. Following an inspection in 2006, concerns were raised about the dam’s vulnerability to internal erosion during strong floods. Boreholes and vibro-cores were performed to collect samples, which were then tested for suffusion susceptibility. The study found that four out of six samples were highly susceptible to suffusion erosion, with the erosion process starting at gradients much lower than unity. The opposite was observed for samples with fines content greater than 30% and showing some plasticity. The results were compared to predictions from seven geometric criteria found in the literature, but none of the methods could forecast the behaviour of all tests. The study highlights the need for laboratory tests when there is no agreement between the predictions from available criteria. The findings of this study were used to inform the rehabilitation of the dam, which included installing sand filters designed to capture the smallest particles and relief wells distributed along the entire length and height of the eastern embankment. The study demonstrates the importance of assessing suffusion susceptibility in embankment dam safety control and the need for laboratory tests to validate predictions from geometric criteria.

Ground Penetrating Radar (GPR) is a widely used technology for the detection of concealed underground structures. This paper presents a GPR survey carried out in response to the floor collapse of a workshop at the Olivais Centre of the Municipality of Lisbon, due to the presence of an unknown underground gallery. The collapse raised concerns about the presence of additional underground galleries beneath the workshop floor. Initial GPR testing in the vicinity of the collapse site provided critical information that led to a comprehensive survey of the entire workshop floor. Analysis of the GPR data revealed anomalies predominantly concentrated in the northwest quadrant of the workshop. Subsequent interpretation of the GPR profiles suggested the existence of another gallery running beneath the floor. These findings highlight the importance of GPR as a fast, efficient and nondestructive technique for detecting underground infrastructure.

To mitigate groundwater level decline, managed aquifer recharge (MAR) with secondary treated wastewater (STWW) is increasingly considered and implemented. However, the effectiveness and potential risks of such systems need evaluation prior to implementation. In this study, we present a large-scale sand tank experiment to analyse processes related to the infiltration of real STWW through the vadose zone and subsequent mixing with oxic native groundwater. The varying composition of STWW from 15 infiltration cycles over six months of operation and the retention times were the main drivers of the observed processes, which were characterized by a wide range of analytical techniques such as in situ high-resolution oxidation-reduction potential (ORP) measurements, closed mass balances of solutes, characterization of dissolved organic carbon (DOC), stable nitrate isotopes analysis, as well as numerical flow and transport modelling. Depending on the composition and infiltration rates of the STWW, both nitrification and denitrification could be observed, even simultaneously at different locations in the tank. Furthermore, due to the variability of the real STWW we observed enhanced arsenic mobilisation during times of elevated phosphate concentrations of the infiltrating STWW. Additionally, uranium was mobilised in our experimental system via carbonate mineral dissolution caused by the infiltrating STWW which was undersaturated of calcite for all infiltration cycles. Overall, our results showed the importance of conducting studies with waters of complex matrix, such as real STWW, and considering mixing with groundwater to assess the full range of possible processes encountered at MAR field sites.

Sand waves are flow-transverse bedforms common in coastal environments, whose activity may affect navigation channels, offshore infrastructure and sediment management. Sand wave asymmetry is generally assumed to indicate the dominant direction of sediment transport, as well as the direction of bedform migration, but the latter assumption is not always confirmed by observations. The complex interaction of sand waves with larger-scale features (e.g. sandbanks, tidal inlet shoals) is also poorly understood. This paper examines the morphology and migration of sand waves in the seaward part of the main ebb channel of the Tagus estuary, based on two multibeam surveys conducted in 2019 and 2020. Sand waves are restricted to the channel side adjacent to the main ebb-tidal delta shoal. Geometric parameters (length, height, steepness and asymmetry) and migration rates were calculated over a 1400 m transect, at an average depth of 20 m, divided into two sections (landward, A, and seaward, B). The average wavelength and height were found to be 80 m and 2.1 m respectively (steepness of 0.027). The spacing versus height relationship is in good agreement with the global mean trend equation of Flemming (1988). The bedform asymmetry is always ebb-oriented (in 2019: 0.29 ± 0.14 in transect A; 0.39 ± 0.17 in transect B). The direction of sand wave migration obtained from the comparison between surveys is also ebb-oriented on average, but more variable (in 2019-2020: 5.3 ± 24.8 m year-1 in transect A; 9.9 ± 18.7 m year-1 in transect B). The observed evolution appears to be generally consistent with ebb dominance in the main channel. It is suggested that (a) sediment transported by waves and flood currents over the main shoal is partially mobilised by the ebb-dominant currents on its steep side, (b) the sand waves reflect a sediment transport pathway along the shoal edge towards the terminal lobe, and (c) sediment is eventually recirculated in a counterclockwise direction.

Cow dung (CD) is a material that has been used for millennia by humanity as a stabilizer in earth building techniques in vernacular architecture. However, this stabilization has been little addressed scientifically. In this study, the effect of CD additions was assessed on earth mortars produced with one type of earth from Brazil and two other types from Portugal (from Monsaraz and Caparica). The effect of two volumetric proportions of CD additions were assessed: 10% and 20% of earth + sand. The German standard DIN 18947 was used to perform the physical and mechanical tests, and classify the mortars. In comparison to the reference mortars without CD, the additions reduced linear shrinkage and cracking. An increase in flexural and compressive strengths was not observed only in mortars produced with earth from Monsaraz. In mortars produced with the earth from Caparica, the addition of 10% of CD increased flexural strength by 15% and compressive strength by 34%. For mortars produced with the earth from Brazil, the addition of 10% of CD increased these mechanical strengths by 40%. The increase in adhesive strength and water resistance promoted by the CD additions was observed in mortars produced with all three types of earth. Applied on ceramic brick, the proportion of 10% of CD increased the adherence by 100% for the three types of earth. Applied on adobe, the same proportion of CD also increased it more than 50%. For the water immersion test, the CD additions made possible for the mortar specimens not to disintegrate after a 30 min immersion, with the 20% proportion being more efficient. The effects of the CD on mechanical performance, including adhesion, were more significant on the tropical earth mortars but the effects on water resistance were more significant on the Mediterranean earthen mortars. CD has shown its positive effects and potential for both tropical and Mediterranean earthen plasters and renders tested, justifying being further studied as an eco-efficient bio-stabilizer.

Industrial masonry chimneys became widespread in the mid-19th century and were eventually integrated into urban landscapes, gaining significance as symbolic historical remnants of local industries. This poses new challenges, particularly concerning the safety of populations and goods, as well as the preservation of the now-historical structures. In this article, we assess the conservation status of the 45-meter-high chimney of the former cork processing factory Mundet, located in Montijo, Portugal. The study involved a structural survey conducted using height access equipment, along with an investigation to diagnose moisture and salt decay at the base of the chimney. The later included measuring current and hygroscopic moisture distributions, as well as XRD characterization of brick and mortar samples. At the chimney’s base, salt crystallization causes efflorescence and erosion leading to masonry disintegration. This is associated with rising damp and the presence of sodium sulfate in the brick and sodium chloride in the mortar. In the shaft, mortar erosion becomes more pronounced as we ascend. At the crown, extensive mortar erosion and limited compression have caused the NE-facing half to disappear, while the rest is at risk of imminent collapse. Damage mitigation measures to address this situation are proposed.

New methods are proposed for the verification of the presence of superabsorbent polymers (SAP) in freshly mixed concrete and estimation of SAP quantity. The methods are in general based on flushing concrete with excess water. They allow separating the light, water-sorbed hydrogel particles from the mineral components in the fresh concrete and making these particles available for further tests. Two types of tests are proposed: Test 1 serves for a visual verification of the presence of SAP (qualitative test), while Test 2 enables quantifying the mass of the collected SAP as a proxy of their concentration in concrete (quantitative test). Different procedures are proposed for these two test methods and their performance is evaluated. The testing procedures were scrutinized in an interlaboratory study carried out by 14 participants from 12 countries. All participating groups detected the presence of SAP in the mix using the qualitative procedures (Test 1). Based on this outcome, we suggest that this method should be applied in the field. In contrast, while most participants obtained reasonably reliable results with the quantification procedure of Test 2, some participants reported large errors. Therefore, the quantification method needs to be further refined, starting from the experience gained in this interlaboratory study.

Despite providing important ecosystem services, termites are also serious pests of wooden structures. Termites are highly adaptive organisms that cause concern as an invasive species. Predictions of the future spread of their distribution range due to factors such as climate change, urban growth, and global trade present new challenges to our capacity to protect our wood and wood-based materials and structures effectively. Reticulitermes grassei Clément, 1978 (Blattodea: Rhinotermitidae) is a subterranean termite native to the Iberian Peninsula and France, whose global distribution has widened over recent years. This article updates the distribution range of this species, confirming its identification in the Azores, Madeira, and Morocco through molecular analysis. The origin and consequences of these putative invasive populations are discussed in light of previously available data. The resulting network showed a highly structured base consisting of many haplotypes from the southern and southwestern Iberian Peninsula (Spain and Portugal), including those from Morocco (in natural landscapes) and Switzerland (in infrastructures). The more derived part of the network includes the haplotypes from southwest France, the northwest Iberian Peninsula, the United Kingdom, Azores, and Madeira, the last 3 being linked probably to human-mediated transportation events. The potential impacts of invasive subterranean termite populations expanding into new regions are concerning, especially in urban environments, and remain uncertain in natural areas. The challenges posed by these termites could be especially worrying in island ecosystems. Hence, it is crucial to implement early warning systems and monitoring programs in regions susceptible to subterranean termite invasions.