International Concrete Abstracts Portal

Conventional slab-on-ground design methods rely on simplified assumptions derived from Westergaard solutions that do not capture key behavioral mechanisms such as slab curling, partial loss of support, concrete shrinkage, and realistic load transfer. This paper presents a mechanistic design framework based on two-dimensional (2-D) finite element analysis (FEA) that incorporates these effects, coupled with calibrated empirical methods for estimating slab capacity.

ACI 332 requires contraction joints in plain and reinforced concrete slabs-on-ground. For post-tensioned (PT) residential slabs-on- ground, PTI DC10.1 permits contraction joints to minimize and conceal random cracks. The layout of contraction joints in residential slabs requires special considerations, which are discussed in this TechNote.

In May 1978, the first 3-day conference on the use of superplasticizers in concrete was sponsored by the Canada Centre for Mineral and Energy Technology (CANMET) and the American Concrete Institute (ACI) in Ottawa, ON, Canada, with selected papers from the gathering published as ACI Special Publication SP-62. The Second International Conference on the Use of Superplasticizers in Concrete took place in 1981 in Ottawa, ON, Canada, again under the joint sponsorship of CANMET and ACI, with the resulting technical proceedings published as ACI SP-68. The Third International Conference hosted by CANMET and ACI was held in Ottawa, ON, Canada, in 1989 with the primary purpose of reviewing the technical progress achieved since the initial meetings in 1978 and 1981. This event marked a significant turning point for the series, as its scope was formally expanded beyond superplasticizers to include all other types of chemical admixtures. Furthermore, the conference successfully brought together representatives from the chemical admixtures, cement, and concrete industries to exchange information and delineate new areas of needed research. The comprehensive findings and technical contributions from this expanded dialogue were formally published by ACI as ACI SP-119. The Fourth International Conference was held in Montreal, QC, Canada, in October 1994, sponsored by CANMET in association with ACI and other organizations, with proceedings published as ACI SP-148. In October 1997, the Committee for the Organization of CANMET/ACI International Conference (ACI Council), in association with ACI and various Italian cement and concrete organizations, sponsored the Fifth conference in Rome, Italy, publishing the results as ACI SP-173. The Sixth conference was hosted in Nice, France, in October 2000, where the ACI Council and partners from Canada and France accepted 37 papers for publication in ACI SP-195. In October 2003, the ACI Council and organizations from Canada and Germany sponsored the Seventh conference in Berlin, Germany, featuring 39 papers published as ACI SP-217. The Eighth conference was held in Sorrento, Italy, in October 2006, sponsored by the ACI Council, with 36 papers accepted and published as ACI SP-239. In October 2009, the Committee for the Organization of International Conferences (COIC) sponsored the Ninth ACI International Conference in Seville, Spain, where 35 papers were accepted and published as ACI SP-262. The Tenth International Conference on Superplasticizers and Other Chemical Admixtures in Concrete took place in Prague, Czech Republic, in October 2012, sponsored by COIC, resulting in 33 accepted papers published as ACI SP-288. In July 2015, COIC and ACI sponsored the Eleventh International Conference on Superplasticizers and Other Chemical Admixtures in Concrete in Ottawa, ON, Canada, where more than 36 refereed papers were accepted and published as ACI SP-302. The Twelfth International Conference on Superplasticizers and Other Chemical Admixtures in Concrete was hosted in Beijing, China, in October 2018, sponsored by the Chinese Ceramic Society (CCS) and the China Academy of Building Research (CABR) in association with ACI, with 36 refereed papers published as ACI SP-329. Fifty-four additional papers were presented and were published in the Supplementary Papers volume. In July 2022, following a postponement due to the pandemic, the ACI Italy Chapter and the University of Bergamo sponsored the Thirteenth International Conference on Superplasticizers and Other Chemical Admixtures in Concrete in Milan, Italy, featuring 35 refereed papers published as ACI SP-354 and approximately 20 supplementary papers. The Fourteenth International Conference on Superplasticizers and Other Chemical Admixtures in Concrete is being held in Munich, Germany, from 6-8 July 2026. Hosted by the Technical University of Munich (TUM) with the support of ACI, this event continues a nearly 50-year tradition of fostering global dialogue on chemical innovations that enhance the performance and sustainability of concrete. Thirteen refereed papers for this conference are published herein as an ACI Special Publication, along with more than 60 presentations, most of them available in a Supplementary Papers volume, explore a wide range of topics, including superplasticizers, rheology-modifying agents, shrinkage-reducing agents, superabsorbent polymers, and self-healing admixtures. These studies examine the influence of admixtures on the properties of concrete in both fresh and hardened states, specifically addressing workability, slump retention, heat of hydration, strength, and durability. The organizing committee expresses its profound gratitude to the authors, reviewers, and partner organizations whose dedication continues to drive the evolution of concrete technology toward a more sustainable future. The support of the American Concrete Institute for the publication of the proceedings is gratefully acknowledged. The Editor Prof. Dr. Johann Plank

This article discusses the development and benefits of CEM II/C-M type low-carbon cements, highlighting their future role in reducing CO₂ emissions within the cement industry. It outlines key production strategies, including the use of quality improvers to enhance early strength and overall cement performance. Comprehensive laboratory testing assessed the durability of CEM II/C-M cements, revealing low shrinkage and robust resistance to water ingress and aggressive chemical agents such as chlorides. Additionally, these cements demonstrated adequate freeze-thaw and carbonation resistance, with performance comparable to standard cements. These findings underscore the potential of CEM II/C-M cements to meet the demands of sustainable construction while maintaining high performance standards. The article also showcases examples of industrial production and the application of these cements in concrete.

Supplementary cementitious materials (SCM) are promising alternatives for the reduction of CO₂ emissions in the cement industry. Despite extensive research, their adoption, using Germany as an example, remains low due to potential disruption in manufacturing processes and standardization issues. Furthermore, the precursor output rate of e. g., fly ash and ground granulated blast furnace slag (GGBFS) is limited not only due to general cement substitution but for shortages in their respective industries. As a result, SCMs may only serve as a viable alternative binder in niche applications, such as concrete maintenance and repair. Additionally, the use of dry activators such as Na₂CO₃ facilitates conventional production methods.

This paper discusses results of sodium carbonate-activated slag mortars that were applied to concrete reference plates (A3-type as described in “Technische Regel Instandhaltung von Betonbauwerken,” eng. technical guideline for maintenance of concrete structures). The performance of alkali-activated slag (AAS) mortars was evaluated in terms of shrinkage behavior, compressive, flexural, and adhesive strength after dry thermal cycling and thunder-shower cycling. Interestingly, the results showed enhanced strength after exposure to these experimental conditions in comparison to ambient temperature curing. This highlights the critical role of proper curing, as AAS mortars are highly susceptible to increased shrinkage when not exposed to sufficient moisture.

The previous results show that AAS mortars - even without optimization - meet the required properties for structural repair class “R3” as defined in DIN EN 1504-3, promoting SCMs as promising alternative binders for these practical use cases.