RILEM Technical Letters

Journal: RILEM Technical Letters

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RILEM Publications

ISSN

2518 -0231

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Publications 1 - 10 of 21

PH-monitoring in mortar with thermally-oxidized iridium electrodes
Seguí Femenias, Yurena; Angst, Ueli; Elsener, Bernhard (2017)
RILEM Technical Letters
Stone consolidation: a critical discussion of theoretical insights and field practice
Praticò, Ylenia; Caruso, Francesco; Delgado Rodrigues, José; et al. (2020)
RILEM Technical Letters
Stone consolidants have been extensively used for the preservation of historical structures since the 19th century. However, their true effectiveness in practice is often a source of debate, largely because of known cases where badly chosen treatments were unsuccessful, or even caused an accelerated degradation of the substrate. Researchers have therefore strived to better understand, and possibly predict, the behavior of consolidants on-site, in order to assist practitioners in their decision making. Despite the large number of publications available on the subject, however, the contribution of scientific research for practical applications remains scarce. Reasons for this include the limited accessibility of scientific publications and the lack of documentation or preparatory studies from the field. This unfortunately compromises the knowledge exchange between researchers and practitioners, which we consider to be a main challenge that this field must overcome. The target of this letter is to reconnect the critical problems identified on-site through practical experience with the conceptual research outcomes that could help solve them. For this, we present an informed evaluation of the most needed research, along with a synthetic overview of the insights that scientific research can offer in terms of consolidant selection, application and monitoring.
A two-fold strategy towards low-carbon concrete
Zunino, Franco (2023)
RILEM Technical Letters
Concrete is by a substantial margin the most widely used construction material. Projections indicate that the demand for concrete it will continue to increase to sustain the development of emerging economies. This paper presents a new perspective of low-carbon concrete by refocusing on the actual final product, highlighting the tremendous CO₂ saving opportunities of reducing the total paste volume of concrete while simultaneously using high performance, low-clinker cements in the so-called two-fold strategy (low clinker content, low paste volume concrete formulations). Different aspects of low paste volume concrete formulations are discussed based on a combination of published and new concrete performance data, showing the potential for CO₂ savings of the strategy and the technical opportunities to retain the robustness and reliability that make concrete such a versatile and widely used material. Chemical admixtures play a crucial role in reaching those objectives, as they enable to reduce the cement content while retaining the needed workability (slump and slump retention) for each application. The key issues relating to using those admixtures in low carbon concrete are highlighted.
Challenges in material recycling for postwar reconstruction
Troian, Viacheslav; Gots, Volodymyr; Keita, Emmanuel; et al. (2022)
RILEM Technical Letters
Besides the fact that concrete recycling allows to avoid landfills disposal and contributes to a closed-cycle economy, such option may be very much in demand in war struck regions such as Ukraine, which after the end of the war, are faced with the problem of rebuilding and reconstructing. Beyond this emergency, even in peacetime extensive parts of the building stock will sooner or later need to be replaced and concrete recycling is called to play an increasing role there. However, depending on the technology and degree to which aggregates are recycled, concrete may be characterized by poor workability, reduced mechanical properties, increased shrinkage and reduced durability. This deterioration in the properties of recycled concrete is usually attributed to the characteristics of the old cement mortar remaining on the surface of the recycled aggregates, which is best considered as an additional volume of hardened cement paste with fine aggregate and additional porosity. This article attempts to underline how such key concepts help frame the current state of knowledge about concrete recycling, understand the implications of existing regulations, in order to define pragmatic and efficient routes for broadening the use of concrete recycling in war struck regions, with specific examples regarding Ukraine.
X-ray computed tomography to observe the presence of water in macropores of cementitious materials
Rossi, Emanuele; Governo, Susanna; Shakoorioskooie, Mahdieh; et al. (2023)
RILEM Technical Letters
Corrosion of steel reinforcement in concrete is a common degradation mechanism occurring in infrastructures worldwide. Even though extensive research has been conducted over the last decades to accurately predict the influence of steel corrosion on concrete durability, a comprehensive understanding of several micro‐scale processes simultaneously involved in the corrosion mechanism is still lacking. The application of X‐ray Computed Tomography (X‐ray CT) can contribute to elucidate these processes, since this technique allows observing the internal status of specimens non‐destructively, over time, and with a spatial resolution in the range of μm. Nevertheless, the relatively low sensitivity of light elements (e.g., hydrogen and oxygen) to X‐ray CT may hinder the observation of solution within the cementitious matrix. This consideration is discussed in this letter. The results of this study show that the detection of solution in macropores (e.g., air voids) through X‐ray CT is not limited by the relatively low attenuation coefficient of the fluid per se, but more by the spatial resolution at which acquisitions are performed and by the dimensions of the porous volume where solution penetrates. The observations reported in this letter may open several opportunities to further study the influence of the moisture conditions of air voids on several degradation mechanisms of reinforced cementitious materials (e.g., steel corrosion, freeze‐thaw damage), which have been rarely investigated with X‐ray CT according to the literature. The application of these findings could significantly deepen the understanding of several micro‐scale processes that affect the durability of reinforced cementitious materials which still need to be elucidated, as further discussed in the present letter.
Digital Concrete: Opportunities and Challenges
Wangler, Timothy; Lloret, Ena; Reiter, Lex; et al. (2017)
RILEM Technical Letters
Digital fabrication has been termed the “third industrial revolution” in recent years, and promises to revolutionize the construction industry with the potential of freeform architecture, less material waste, reduced construction costs, and increased worker safety. Digital fabrication techniques and cementitious materials have only intersected in a significant way within recent years. In this letter, we review the methods of digital fabrication with concrete, including 3D printing, under the encompassing term “digital concrete”, identifying major challenges for concrete technology within this field. We additionally provide an analysis of layered extrusion, the most popular digital fabrication technique in concrete technology, identifying the importance of hydration control in its implementation.
Active Control of Properties of Fresh and Hardening Concrete
De Schutter, Geert; Abidi, Imene; Korda, Eleni; et al. (2024)
RILEM Technical Letters
Concrete mixtures have an optimized mix design in view of attaining desired properties. However, after mixing, during further processing, it is typically not possible to further adjust the performance of the fresh and hardening concrete. A new and emerging approach is to actively control the concrete properties by means of responsive particles or polymers triggered by an externally applied signal. Active control of properties of concrete refers to the concept of on- demand changes of one or more properties of the concrete after mixing by triggering a response to one or more of the constituents using a specific trigger signal (e.g. thermal, chemical, electrical, magnetic...). The on-demand control of properties can focus on the processing stage (including e.g. pumping, casting, 3D printing), the curing and hardening stage (including e.g. control of capillary pressure, shrinkage, setting, and hardening) and even on the hardened stage during service life (e.g. active corrosion control, active crack healing...). Addressing specific obstacles in cementitious environments, ensuring responsive material stability, controlling signal applicability, cost, logistics, and on-site safety is crucial for successful implementation. A RILEM technical committee has been initiated in 2023, working on the concept of Active Control of Properties of Concrete (RILEM TC 317-ACP). The committee will focus on active control of properties of fresh and hardening concrete. This paper gives a short introduction to scope and activities of TC 317-ACP.
Recommended practice for reporting experimental data produced from studies on corrosion of steel in cementitious systems
Isgor, O. Burkan; Angst, Ueli; Geiker, Mette; et al. (2019)
RILEM Technical Letters
Experience has shown that many aspects of experimental design for studying steel corrosion in cementitious systems may significantly influence the obtained results. In the absence of standardized methods to study steel corrosion in concrete, researchers usually define their own test setups, which partially explains the large scatter and uncertainty in the aggregated published data. When the details of these setups are not provided adequately, experimental results cannot be interpreted in a wider context. Unfortunately, many scientific publications lack important experimental details. Therefore, this paper aims at improving the quality of reported experimental details, observations, and data in scientific publications, and raising awareness for relevant issues to improve the quality of research in the field. To this end, this paper provides a list of experimental details that have been found important by many decades of research, and which are, thus, recommended to be considered in conducting and reporting laboratory studies involving corrosion of steel embedded in cementitious systems. Finally, we propose a c hecklist for reporting experimental data in scientific publications.
Heritage ++, a Spatial Computing approach to Heritage Conservation
Patankar, Yamini; Tennenini, Camilla; Bischof, Rafael; et al. (2024)
RILEM Technical Letters
Historic structures are affected by numerous degradation processes driven by a complex system of interconnected and mutually influencing factors. Preserving these monuments is a multidisciplinary endeavour that extends beyond one-time interventions, necessitating a comprehensive methodology that involves various stakeholders, expert consultations, monitoring tools, and impact assessments. Limitations arise due to communication barriers and difficulty in translating and transferring experience among disciplines, often compromising the collective ability to define the best possible conservation strategies.Recent advancements in 3D modelling and data management technologies offer collaborative platforms for information sharing. However, the complex interfaces of these tools often limit their accessibility, making them exclusive to specialists. Integrating Spatial Computing could address these challenges by fostering intuitive engagement and enhancing accessibility and depth in interdisciplinary interactions. This letter outlines initial efforts in using spatial computing to tackle the challenges of built heritage conservation and presents a vision for its future development.
In-Crease: Less Concrete More Paper
Lloret-Fritschi, Ena; Choma, Joseph; Scotto, Fabio; et al. (2022)
RILEM Technical Letters
Concrete is one of the most used materials after water. Largely owing to this, its environmental impact is substantial, although its embodied carbon per unit volume or mass is low when compared to most alternatives. This, along with the broad availability, good strength, durability and versatility of concrete means that it will remain a material of choice, although more efficient ways of using it must be found. Structurally optimized building components are a means to do this as they can save about 50% material. Unfortunately, however, such elements are presently too expensive to produce owing to them requiring non-standard formwork. It is an objective of digital fabrication to propose solutions to this issue. In this con-text, Digital Casting Systems (DCS) have advanced material control strategies for setting-on-demand in digital concrete processing. Thereby, the formwork pressure is reduced to a minimum, which opens possibilities of rethinking formworks as systems that are dynamically shaping, millimetre thin or weakly supporting the material cast inside. In this paper we present a brief overview of millimetre thin formworks and summarize the first realization of concrete elements that utilizes the mechanics of paper folding to make millimetre thin formworks up to 2.5 meters high. Such formworks could initially be flat packed, erected into shape, and eventually peeled-off and recycled in established material streams. This would reduce waste and transport cost, while offering a surface finish that meets the expectations for exposed concrete surfaces.

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Journal: RILEM Technical Letters

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