RILEM Technical Letters

Key challenges and opportunities in transitioning towards road bridges with reduced carbon emissions - Perspectives in Switzerland

Yunus Harmanci, Lukas Kramer, Moslem Shahverdi, René Steiger — Mon, 06 Apr 2026 00:00:00 +0000

The construction sector is a major contributor to CO₂ emissions, responsible for approximately 37% of global and 23% of Switzerland’s total emissions. Addressing this substantial carbon footprint requires innovative and sustainable materials, advanced construction techniques, and comprehensive stakeholder engagement. This paper discusses the key challenges and opportunities in transitioning towards reduced carbon emissions within the construction sector, focusing on the Swiss industry and road bridges as a case study. An extensive dataset of Swiss road bridge infrastructure is assessed herein to understand the current state in Switzerland. An engineering-oriented critical review of high-performance materials such as non-metallic reinforcements, lower impact concrete mixtures and timber products is made in comparison to established construction materials. Circular principles and design for disassembly are explored as strategies for reducing environmental impact. This paper identifies the critical role of availability of early-stage information regarding environmental impact, standardization of emerging materials and techniques, and stakeholder engagement in driving the construction sector towards practices with reduced carbon emissions. Emphasis is put on the requirements and alternatives for achieving reduced carbon emissions in newly constructed bridges, while the potential for extending the service life of existing bridges and its importance for achieving net-zero infrastructure goals is acknowledged but not explored.

Nano silica admixtures: Salt ingress and reaction in mortar

Julien Hubert, Fengyin Du, Cibele De Araujo, O Burkan Isgor , W Jason Weiss — Tue, 31 Mar 2026 00:00:00 +0000

This paper examines the influence of commercially available nano silica (NS) admixtures on salt ingress and reaction in mortar. A series of mortar mixtures at dosages ranging from 2.6 to 41.8 mL/kg were tested using isothermal calorimetry (IC), thermogravimetric analysis (TGA), low temperature differential scanning calorimetry (LTDSC), and chloride profiling. Thermodynamic modeling was used to support the experiments. IC showed that the heat of hydration was slightly higher (2-3%) than the reference mixture when the NS admixtures were used. TGA indicated up to 18% reduction in calcium hydroxide at low admixture concentrations (2.6 to 7.8 mL/kg), which is greater than the reduction that would be expected due to pozzolanic reactions alone. At higher admixture dosages (above the recommended dosages), the calcium hydroxide contents were similar to or higher than those of the reference mixture. LTDSC results showed up to a 30% reduction in calcium oxychloride (CaOXY) formation potential; however, this reduction may not be sufficient to avoid the potential damage associated with expansive CaOXY formation at concrete joints in pavements and flatwork. The NS admixtures did not affect chloride ingress profiles significantly. Thermodynamic calculations indicate that although the admixtures provide reactive silica that acts pozzolanically, the amount is relatively small compared to the admixture dosages used.

Report of RILEM TC 308 PAR: Cold recycling of reclaimed asphalt with bituminous binders – A critical comparison of practices in the countries involved in the TC 308-PAR TG1, Part II

Wed, 25 Feb 2026 00:00:00 +0000

The RILEM technical committee on Performance-based Asphalt Recycling TC 308-PAR is dedicated to advancing research, promoting knowledge exchange, and disseminating information related to asphalt material recycling. Within this framework, Task Group 1 (TG1) “Performance-based Evaluation of Cold Recycled Asphalt Mixtures” concentrates on aligning laboratory testing methods with the real-world performance of cold recycled asphalt mixtures. To this end, TG1 members collaborated to share the various cold recycling practices adopted in their respective countries. This collaboration aimed to compare specific procedures, technical specifications, and expected performance outcomes. The participants diverse backgrounds, spanning differences in road classifications, traffic loads, climatic conditions, and availability of materials, enabled the development of a comprehensive overview of current methodologies and provided insights into the potential expansion of cold recycling applications.

The comparative study of national practices has been structured into two papers: Part I focuses on the constituent materials and mixture composition, while Part II addresses testing protocols and the construction process. In detail, Part II reports a critical comparison of testing procedures, mechanical characteristics, construction methods and quality control procedures used in Italy, Canada, Poland, Brazil and USA, either adopted by selected road administrations or established by reference standards. Accordingly, all initial assumptions, terminology, definitions, and the general context presented in Part I should be considered fully referenced and applicable. This paper focuses on recycling techniques using both cement and bitumen as binders. Conversely, although the use of cement alone is a recognized and widely applied technique, as reported in Part I, Part II does not consider it, since a greater degree of uniformity in procedures and knowledge has already been achieved and shared worldwide.