RILEM Technical Letters

Testing Methods for Masonry Cores: A way forward to increase reliability of mechanical properties evaluation

Rita Esposito — 2025-01-27

The assessment of unreinforced brick masonry structures and infrastructure is a worldwide challenge for the development of resilient urban areas and preservation of historical assets. Among other factors, the estimation of mechanical performance of masonry in existing construction is of importance. However, the characterisation effort does not always satisfy the requirements from structural analyses point of view, i.e. need of elastic, strength and toughness properties, and/or from technical point of view, i.e. use of conventional technical expertise and limited invasiveness. In this respect, the new RILEM Technical Committee CTM aims at promoting the use of tests on masonry cores for the evaluation of compression and shear properties of unreinforced masonry with regular units. Upon a state-of-the-art review, a database of previous experimental test series will be created to identify influencing factors (e.g., core’s geometry, boundary conditions). Selected testing procedures will be compared at various international institutes for a variety of masonry types typically used in existing structures and infrastructure. By comparing results with standardise tests, correction factors will be identified. Eventually, testing guidelines to characterise masonry with core specimens will be defined and shared within the research and engineering community.

Mechanical behavior of bio-aggregates based buildings materials

Sofiane Amziane — 2025-01-24

This Technical Letter examines the mechanical behaviour of bio-aggregate building materials (BBM), focusing on their performance under compressive, flexural and shear loading. The study synthesises the findings of various RILEM technical committees and recent research, highlighting the unique properties of BBM compared to conventional concrete. The paper discusses the factors influencing the mechanical behaviour of BBM, including bioaggregate type, volume fraction, morphology, mineral matrix, mix design, casting process and curing conditions. It presents detailed analyses of the BBM response under different loading conditions, highlighting the different phases observed during testing. The use of Digital Image Correlation (DIC) as an advanced measurement tool to capture BBM deformation is explored, providing insights into the heterogeneity and local behaviour of the material. The importance of the Interface Transition Zone (ITZ) between bio-aggregates and matrix is highlighted, with a focus on its formation and impact on mechanical properties. The paper also outlines the perspectives of a new technical committee aimed at harmonising test procedures and developing scientific data analysis methods for BBM. This comprehensive review provides valuable insights for researchers and practitioners working with bio-based building materials, paving the way for improved understanding and standardisation of the mechanical characterisation of BBM.

Consolidants in Salt-Weathered Masonry: Retention and Efficiency of DAP and TEOS

V A Anupama — 2025-01-21

Consolidants are widely used to improve grain cohesion in monuments and sculptures under degradation. The porosity and pore size distribution of the substrate and the consolidant properties play a pivotal role in the efficient absorption and retention of the compounds. The substrate mineralogy is critical in product formation and essential for the substrates' long-term durability. In this study, the masonry components – brick, mortar and brick-mortar sandwiches – are consolidated by brushing with two different consolidants – phosphate-based DAP and silane-based TEOS. The accelerated salt weathering of specimens in chloride and sulphate solution simulated their deteriorated stage closer to reality before consolidation. The short-term and long-term effects of carbonation condition, pore size distribution, mineralogy and hygric resistance on the consolidation are investigated through microstructural analysis. The results highlight the importance of pore size distribution and porosity in the initial consolidant uptake and the significance of the compositional similarity between the substrate and the consolidant in the long-term retention amount of the consolidants. The observations indicate that TEOS consolidation's higher efficiency is at the expense of pore occlusion, which could adversely affect the systems' durability under salt weathering and freeze-thaw.

On the New RILEM Technical Committee TC APD: Alternative Paving Materials – Design and Performance

Augusto Cannone Falchetto — 2025-01-21

This paper introduces the new RILEM Technical Committee on Alternative Paving Materials – Design and Performance (TC APD), which builds upon the foundational efforts of the former TC 279-WMR focused on the Valorisation of Waste and Secondary Materials for Roads. The TC APD aims to advance the understanding of alternative paving materials, emphasizing their design and performance as essential components of road composites. The committee addresses three areas of investigation, each dedicated to examining the current technological state of the art, the design process and the field performance of composites incorporating alternative paving materials. The manuscript provides a comprehensive overview of the TC's background, outlines the research objectives and activities proposed, and discusses the committee's position within RILEM and the broader research community. Additionally, it details the anticipated outcomes and the potential impact of the committee's work on advancing the field of sustainable road construction.

RILEM TC CUC: Carbon dioxide uptake by concrete during and after service life – Opening Letter

Gregor Gluth — 2025-01-07

The ability of cement to chemically bind CO2 in a carbonation reaction enables the material to act as a carbon sink, which could partly account for offsetting the CO2 emissions associated with cement production. In response to the many open questions in this context, the RILEM Technical Committee CUC was created in May 2024. The focus of the TC will be to facilitate discussions regarding the current approaches to estimate the CO2 uptake by cementitious materials (concrete and other construction products) during and after service life. This Opening Letter presents aspects of the motivation to establish the TC, a brief overview of the state of the art in the field, the scheduled work programme, and the anticipated impact of the TC outputs. Though it is not intended to be an exhaustive discussion of the challenges to be addressed, from what is summarized in this letter, it is clear that work is required to base estimates of CO2 uptake by cementitious materials on a data set that is as extensive, accurate and forward-looking as possible. It is anticipated that the inclusion of interdisciplinary perspectives and data from academia and industry will enable progress in the field.

Heritage ++, a Spatial Computing approach to Heritage Conservation

Yamini Patankar — 2025-01-02

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.

Concrete Infrastructure: Recent Advancements and Needs with a Focus on North America

Pedro Castro-Borges — 2024-11-15

This letter provides an overview of the continent’s diversity in geography and climatic exposure and the impact of chlorides on reinforced concrete structures in North America. Several research needs are identified, including those that arise as specifications begin to change from prescriptive to performance-based approaches. Further, the widespread changes in material compositions or chloride exposures, require important changes to specifications, design practices, or maintenance procedures. Related to reducing carbon emissions, there is a need to reduce clinker content in concrete mixtures, increase the use of novel cementitious and supplementary cementitious materials (SCM), and to understand the durability of such concretes. The following research efforts from a North American context are warranted: (i) investigating the long-term durability of novel cement and SCM systems, including non-Portland cement-based materials and those made with CO₂ mineralization used to meet carbon emission targets; (ii) understanding climate change impacts of temperature and sea levels, including flood impact, on chloride exposure and chloride-induced corrosion; (iii) developing rapid and reliable tests to estimate durability in practice, particularly for scaling, freeze-thaw, salt damage, and chloride-induced corrosion; and (v) developing better understanding of the short and long-term implications of changes in constituent materials and exposure.

Split wooden rods for novel wood-based boards in the construction sector

Ingo Burgert — 2024-11-08

Wood has been utilized as a building material for thousands of years. Nowadays, its renewable nature and carbon-storing capacity can become important factors in climate change mitigation efforts. This has led to a resurgence of timber engineering in recent years, with impressive multi-story timber buildings worldwide. However, it should not be overlooked that the wood sector will face several challenges in the coming years and decades to pave the way to a leading role of wood in the desired transition toward bioeconomy. Based on the assumption that an increasing demand for wood will make it a more precious resource, a couple of strains will emerge across the entire value chain of wood processing. This calls for innovations to address issues arising from predicted changes in resource provision, to increase material yields, and to promote reuse after the end of life. Our conceptual article proposes a new wood separation and processing method. This approach is inspired by the well-known production of wood shingles and is currently being developed for the implementation of new wood-based products.

Leveraging network analysis to improve navigability of design standards

Chase Rogers — 2024-11-07

The utility of building design standards is a growing concern amongst construction professionals. Design standards continue to swell with updates, which makes ensuring all requirements are satisfied increasingly complex for users. Few tools exist for authors of standards to improve navigation for users. This study investigates the use of network analysis to understand the relationship between the organization of a standard and navigational complexity. A case study is presented of the reorganization of American Concrete Institute’s (ACI) flagship design document, ACI 318. The standard’s networks before (ACI 318-11) and after (ACI 318-14) the reorganization are developed via rule-based text extraction. Networks are analyzed assuming that ACI 318-14 is the structurally superior document. Indicators of complexity are identified from each networks' characteristic features, centrality metrics, clustering tendencies, recurring motifs, and geodesic paths. Network analysis is found to be useful for identifying, understanding, and mitigating navigational complexity within a building design standard.

Discussion of “Thermal conductivity of porous building materials: An exploration of new challenges in fractal modelling solutions”

Hans Janssen — 2024-11-07

In November 2023 this journal published “Thermal conductivity of porous building materials: An exploration of new challenges in fractal modelling solutions”. That paper gauges four fractal building materials’ thermal conductivity models, concluding that fractal-geometry-based approaches appear “a promising method” as they “demonstrate high reliability in reproducing experimental data”. This discussion of the paper aims to shine a different light on the potential of fractal thermal conductivity models. It shows that good agreement with experimental data usually originates from calibration of various “physical” factors comprised in these models, with the fitted numbers commonly deviating from physical reality. Moreover, exemplary instances reveal that good agreement with experimental data is obtained despite misinterpretation of measured outcomes or critical defects in model development, or, exceptionally, due to fabrication of validation information. This discussion does hence not share the paper’s positive opinion on the prospects of fractal-geometry-based thermal conductivity models, and advises caution instead.

Practical Insights and Advances in Concrete Pumping

Daniil Mikhalev — 2024-09-19

This technical letter gives a concise overview of the state-of-the-art in concrete pumping. It outlines the different pump systems, briefly describes the general flow behavior of concrete in pipes, and addresses the main challenges of pumping. It also elaborates upon factors influencing the pumping behavior and how to control the pumping process.