RILEM Technical Letters

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.