International Conference on Calcium Aluminates 2026

8 Jun 2026, 08:30 → 11 Jun 2026, 18:00 Europe/Zurich

SwissTech Convention Center EPFL

This conference aims to bring together the leading minds from Academia and Industry working in the field of Calcium Aluminates to address scientific progress as well as the global challenges of sustainability and the environment.

Calcium Aluminates 2026 is the sixth conference devoted to the science and application of calcium aluminates.

We extend a warm welcome to the global calcium aluminate Community to participate.

• Welcome Reception
• Conference Banquet
• Exhibition Space
• Keynote Lectures and Parallel Sessions

CAConference26-Poster-Template.pptx

Calcium Aluminates 2026 Abstract.docx

Monday 8 June

1 Opening Reception in the EPFL Laboratory of Construction Materials (LMC) and Courtyard

Tuesday 9 June

08:30 Coffee

Opening Session

Conveners: Jason Ideker (Oregon State University), Karen Scrivener, Matthew Adams (New Jersey Institute of Technology)

2 Welcome

Speakers: Jason Ideker (Oregon State University), Matthew Adams (New Jersey Institute of Technology)

3 Perspectives on Calcium Aluminates

Speaker: Karen Scrivener

Manufacture

Conveners: Karen Scrivener, Hervé Fryda (IMERYS)

4 Calcium Aluminates Manufacturing Current Technologies and Future perspectives

Speaker: Hervé Fryda (IMERYS)

5 Conventional and potential alternative non-conventional raw materials for the production of calcium aluminates-based cements of different hydraulic activity

Calcium aluminate cements (CACs) are well known for their rapid setting characteristics and refractory performance, owing to their significant early strength gain and excellent thermal stability. The properties of CACs vary based on their alumina content. Global demand for CACs has shown consistent growth in recent years. However, this projected rise in production is likely to intensify the demand for natural raw materials such as limestone and bauxite, thereby increasing the environmental impact-particularly due to emissions associated with limestone calcination. Numerous conventional and alternative raw materials have been identified and studied within CAC technology, owing to their multiple advantages, including cost reduction, lower carbon emissions, and enhanced sustainability. This study tackles the combined challenges of incorporating alternative raw materials and developing hydraulic binders exhibiting diverse hydration characteristics.

Acknowledgements
This work is financed by Górka Cement Sp. z o.o. Company. This work was also partly supported by the statutory funds of the Faculty of Material Science and Ceramics AGH University of Krakow, Poland with the Agreement no. 16.16.160.557.

Speaker: Dominika Madej (AGH University of Krakow)

6 PRECIZE: A Novel Approach to Decarbonizing Specialty binders through Hydrogen Combustion

Addressing the significant CO₂ emissions from calcium aluminate cement (CAC) production is a critical challenge for the building and infrastructure sectors, with fossil fuels accounting for a large portion of the greenhouse gas (GHG) footprint. To tackle this, we initiated the PRECIZE project, a strategic collaboration with Air Liquide, LGC, and CEMHTI. Funded by the French state as part of the France 2030 program and operated by ADEME, this initiative is a strategic component of our commitment to science-based targets. One of the key objectives of this project is to demonstrate a scalable pathway to decarbonize CAC production by replacing fossil fuels with a carbon-free alternative like hydrogen. Our study presents the methodology and findings of a successful 12-day pilot trial conducted at our Dunkerque site, detailing the progressive transition from a mixture of 100% natural gas to a 100% hydrogen. The results of this extensive pilot trial will be presented in this paper. We will provide a comprehensive analysis of the impact on CAC quality and performance, as well as on kiln behavior and stability.

Speaker: Bela Kumar (Imerys Technology Center Lyon)

10:40 Break

Hydration 1

Conveners: Barbara Lothenbach, Elsa Qoku

7 Hydration and conversion reactions of Calcium Aluminate Cement with reactive Calcite

The hydration reaction and transformation behavior of a calcium aluminate cement (CAC) mixed with reactive calcium carbonate (Cc) were investigated at different temperatures. By introducing CO32- into the pore solution of the hydrating CAC through calcite dissolution, a promising way was investigated to avoid or limit the metastable hydrate phases (CAH10, C2AHx) that typically occur during the hydration of pure CAC.

Instead, the precipitation of carbonate-AFm phases, mainly monocarbonate, is favoured. Analysis of the extensive data base (10-90°C) has shown the general conditions and temperature limits under which the calcium aluminate hydrate phase monocarbonate is formed and stabilized. At 60°C, no thermodynamic stability or formation limit of monocarbonate is found. No conversion of monocarbonate to C3AH6 (or dissolution-precipitation) was observed up to 80°C, this probably only happens above a critical temperature, which is specified in databases as approximately 90°C.

We were able to demonstrate that C2AHX acts as a precursor for monocarbonate in the early hydration of mixtures of CAC with Cc. Below 20°C no or only a small amount of C2AHx and thus also no or only minor monocarbonate should initially form in CA-dominated CAC-pastes. Here, CAH10 is prevailing. At elevated temperatures (40°C and 60°C), when CAH10 does not initially precipitate, monocarbonate is formed as result from the rapid conversion of the precursor phase C2AHx.

Speaker: Prof. Friedlinde Götz-Neunhoeffer (Mineralogy, Friedrich-Alexander-University Erlangen Nürnberg)

8 Influence of the type and amount of calcium sulfate on the hydration of a C12A7-based cement

Mayenite based cements allow for reduction of the global warming potential of dry-mix recipes compared to typical ternary binder system. This is due to the fact that you can achieve the same early age properties with this technology at a lower total binder content of the recipe. Typically, these formulations are poor in Portland cement and calcium sulfates are added to maximize the early ettringite yield during hydration. The type and amount of calcium sulfate plays a critical role in the hydration behavior of mayenite-based systems and not a lot of research has been performed on this topic. In this work we investigated the influence the types and amounts of calcium sulfates have on the hydration of a C12A7-based cement. We investigated both a model system as well as a self-leveling underlayment recipe based on this technology.
It is shown that the reactivity of the calcium sulfate plays a significant role in the early strength build-up and ettringite formation rates. In addition, long term expansion is also significantly influenced by changes in the calcium sulfate types and different hydrate phase assemblages are observed.
This work provides a basis for further investigations within this system, in which, for example, the influence of various retarders and the amount of Portland cement on the hydration behavior and mechanical performance can be examined.

Speaker: Julian Wolf

9 The role of slag and calcined clay in the hydration and conversion of calcium aluminate cement

One of the widely accepted approaches to decarbonizing the cement sector is the partial replacement of clinker with supplementary cementitious materials (SCM), such as slag, limestone, fly ash. Previous studies have shown that slag helps to inhibit the conversion of calcium aluminate cement. Due to the problems with the availability and cost of slag, there is a need to investigate other possible SCMs and their application potential in CAC. Calcined clay with medium kaolin content available in the region was used in this study. The evaluation of the hydration and conversion process was monitored by analyzing the microstructure and compressive strength up to 56 days. The results show the influence of strätlingite hydrate formation on the conversion process of CAC.

Speaker: Marijana Serdar (University of Zagreb Faculty of Civil Engineering)

12:10 Lunch

Hydration 2

Conveners: Barbara Lothenbach, Elsa Qoku

10 Quantification of the metastable calcium aluminate phases C2AHx using an extended PONKS method

Quantification of the metastable hydrate phases CAH10 and C2AHx is essential in understanding and evaluating the conversion progress of CAC pastes for scientific and industrial research. Mainly XRD or TGA are used for phase quantification, whereas XRD proved to be more precise. While structural data exist for CAH10, they do not yet exist for C2AHx, as the proportion of interlayer H2O in the unit cell of this AFm-phase varies during hydration. Pure synthesis is strongly dependent on the relative humidity and made even more critical by the risk of CO2-uptake by C2AHx and transformation to monocarbonate. Thus, in the initial hydration of CACs either x = 8.2, 8 or 7.5 interlayer H2O are described, resulting from reduction of interlayer distances. By further drying at elevated temperatures x = 5 or even 4 is reported.
An evaluation of the synthesized phase contents of C2AHx phases was achieved by multiple synthesis routes, back-quantification of minor phases that have been precipitated as impurities and modeling of an hkl-model according to the PONKS method.
The suitability of this structure model was verified by in-situ XRD of an accelerated system (CA hydration at 40°C, with a maximum crystallinity of C2AHx) and various measurements of synthetic and industrial calcium aluminate cements, e.g. in applications for refractories or binders.
Factor F was determined as the product of the squared volume V of unit cell and the density ρ of C2AHx, (F=V2 * ρ) for the use within the inp-dataset corresponding to this hkl-model for quantification by Topas. This model can be used to determine the quantity of C2AHx in any hydrated CAC sample by XRD.
Error analysis including the influence of the external standard, synthesis inaccuracy and the interlayer H2O variation of C2AHx resulted in an error of only 3.5 rel% of the determined C2AHx quantity.

Speaker: Dr Julian Goergens

11 Influence of curing temperature on the phase composition and microstructure of calcium aluminate cement bond castables subjected to hydrothermal conditions

Calcium aluminate cement is widely used as a binder in refractory castables because it enables shaping complex geometries and allows the material to withstand extreme temperatures. Their typical manufacturing process consists of mixing, curing, demolding, drying and firing. In modern dense and highly dispersed castables with very low permeability, water remains in the castable body during the drying up to 200°C and beyond. This leads to an increase in internal pressure and hydrothermal conditions occur. Consequently, problems such as cracking and explosive spalling can arise.
Different temperatures during hydration of CAC lead to the formation of distinct hydrate phases and consequently, different microstructures can develop in the hardened material. Hydrothermal conditions lead to the transformation of the original hydrate phases, while still preserving microstructural features inherited from the initial hydration stage. This study presents the influence of curing temperature (5, 23, and 40 °C) on phase development and porosity in a refractory castable model system subjected to hydrothermal conditions.

Quantitative X-ray diffraction measurements revealed that CAH10, C2AHx, C3AH6 and AH3 are formed during curing at different temperatures and that the degree of hydration also varies. When hydrothermal conditions occur, the remaining clinker phases react and the already formed hydrate phases first transform to AH3 and C3AH6. While C3AH6 remains stable with increasing temperature and pressure, AH3 converts to boehmite above 140 °C.
Although the final mineralogical phase composition is the same, microstructural analysis via SEM and mercury intrusion porosimetry revealed differences in the three initially differently cured materials. While the total porosity is comparable, the samples that were cured at 40 °C have a higher proportion of large pores and a different appearance of C3AH6. The study could show that the initial microstructure that is created during curing is preserved after hydrothermal conditions induce additional reactions and phase conversions.

Speaker: Dr Andreas Koehler (Almatis GmbH)

12 Reducing the risk of explosive steam spalling of calcium aluminate bonded refractory concretes through a modified hydration path

High performance (HP) refractory concrete rely mainly on sophisticated, highly densified matrix systems with a high charge of pore-filling alumina and silica micro-powders, deflocculated with efficient polymer admixtures, and bonded with 70% Al2O3 containing calcium aluminate. However, these HP concretes experience a challenge concerning the safe and rapid removal of free pore and hydrate water prior to the utilisation of the refractory concrete as protection linings in industrial furnaces. Their low permeability risks an internal pressure build-up and hydrothermal conditions during the first heat-up. The pressure can potentially exceed the strength of the refractory material if heated too fast. However, time is an important economic factor and creating cracks or even explosive spalling of the refractory lining during the first heat-up could be the consequence if specifically designed dry-out procedures for such highly densified refractory concrete are not entirely followed.
Possibilities to promote a microstructure that allows for more permeability to evacuate the water more easily and at relatively lower temperature without losing the advantage of low porosity and small pore sizes will be discussed in this paper. The hydration and dehydration path of calcium aluminate plays a crucial role in this regard. It will be shown that it is possible to trigger more gel-like calcium aluminate hydrates at the expense of the usually occurring crystalline hydrates, eg. CAH10, C2AH8, C3AH6, AH3, and AH. This calcium aluminate gel releases its water already between 100 and 150°C, at a significantly lower temperature range than the crystalline calcium aluminate hydrates, and even before a high pressure build-up and hydrothermal conditions occur. It creates a more permeable system through which the water can be transported to the surface of the concrete more easily and the risk of pressure build-up is significantly reduced.

Speaker: Jean Michel Auvray (IMERYS)

Admixtures/Rheology

13 Calcium Aluminate Cement Hydration under the Influence of Mineral Acids

In technical applications, the hydration kinetics of calcium aluminate cement (CAC) are commonly modified by chemical admixtures. In this phenomenological study, we investigate the influence of five strong acids - HCl, HNO₃, HClO₄, H₂SO₄, and H₃PO₄ - on CAC hydration under two conditions: dilute suspensions (w/s = 100) and cement pastes (w/s = 0.3). In dilute systems, in-situ pH and conductivity measurements show that all acids inhibit the initial dissolution of monocalcium aluminate (CA). The inhibition time increases exponentially with proton concentration. Thermodynamic modeling suggests that early precipitation of Al(OH)₃ plays a key role. Notably, the acids differ in their inhibiting efficiency at equivalent proton dosages. Phosphoric acid stands out, which is attributed to the simultaneous formation of hydroxylapatite and Al(OH)₃. For the other acids, the inhibition follows the order SO₄²⁻ > Cl⁻ > NO₃⁻ > ClO₄⁻. This sequence is in line with the Hofmeister series, indicating that anion-specific effects influence calcium solvation. In cement pastes, isothermal calorimetry reveals that all acids delay the CAC main reaction, though the retardation order differs significantly from that in dilute suspensions. The different hydration kinetics with H₃PO₄ suggests a unique retardation mechanism, likely due to early formation of hydroxylapatite and Al(OH)₃. For the other acids, thermodynamic calculations suggest that Al(OH)₃ and anion-specific AFm phase formation during the dormant period may explain the observed differences in retardation behavior. In summary, this work provides new insights into acid-specific mechanisms during initial CAC dissolution and subsequent phase formation by combining experimental data with thermodynamic modeling.

Speaker: Lukas Deffner

14 Hydration control additives for OPC CAC anhydrite system

Modern dry mortar formulations require precise hydration control to address performance, sustainability, and supply chain considerations. The OPC–CAC system is a ternary binder composed of Ordinary Portland Cement (OPC), Calcium Aluminate Cement (CAC), and a calcium sulfate source such as anhydrite or hemihydrate. This combination is commonly used in applications including self-leveling underlayments, tile adhesives, and repair mortars where fast setting and high performance are required.

This study examines the use of hydration control additives (HyCon® R), which function as selective ettringite retarders. These additives provide control over early hydration, workability, and strength development in ternary CAC-based systems. Key performance indicators such as mechanical strength and setting time were evaluated, with XRD and calorimetry employed to analyze hydration kinetics. HyCon® R was found to delay ettringite nucleation without impacting its growth rate, resulting in changes to flow retention, early strength development, and dimensional stability. These effects may contribute to performance characteristics and potential material savings without compromising mechanical properties. Additionally, the system has the potential to reduce lithium usage, supporting certain sustainability objectives.

Speaker: Dr Joerg Nehring (BASF Construction Additives GmbH)

Admixtures/Rheology: Poster Session

15 Effect of Calcium Sulfate Source and Curing Temperature on the Hydration Behavior of CAC-OPC-C$ Ternary Systems

In this study, the hydration behavior of ternary binder systems composed of calcium aluminate cement (CAC), ordinary Portland cement (OPC), and different types of calcium sulfate sources (C$) was investigated under variable curing temperatures. As calcium sulfate sources, natural gypsum and phosphogypsum, a by-product of the phosphate fertilizer industry, were compared to evaluate their influences on early hydration kinetics, phase formation, and setting properties. To investigate the effect of calcium sulfate sources, the composition of the binder was kept constant at CAC:OPC:C$ = 63:13:24 by mass, and the water-to-binder ratio was fixed as 0.5 across all mixtures. The study was performed at three different curing temperatures: 5℃, 25℃, or 45℃. An isothermal calorimeter was utilized to observe the heat of hydration. Phase evaluation of 1-day, 3, 7- and 28-day-old samples was employed using X-ray diffraction (XRD) and Thermogravimetric analysis (TGA) equipment, providing insights into the mineralogical changes occurring during hydration and curing processes. Scanning electron microscope (SEM) images of the samples of different curing times were taken to observe the microstructure of hydration products. The initial and final setting times were determined with automatic Vicat equipment. Compressive and flexural strengths at 28 days were used to assess mechanical performance. Results show that both calcium sulfate source and curing temperature significantly affect the rate of ettringite formation and strength development. Phosphogypsum tends to delay setting and early hydration but promotes sustained reaction at later ages, particularly under high temperatures. Differences in microstructural evolution and crystalline hydrate phases were evident across curing regimes and C$ types.

Speaker: Özge Demirdogan (Sabanci Technology Center GmbH - Middle East Technical University)

16 Energy-Efficient 3D Printable Mortars Using CAC–WPC Blends and Microencapsulated PCMs

Additive manufacturing (3D printing) continues to advance as an alternative to conventional construction techniques due to its numerous technical and operational advantages. This study aims to develop a mortar system incorporating Calcium Aluminate Cement (CAC), White Portland Cement (WPC), and microencapsulated Phase Change Materials (mPCMs) for 3D-printing applications. The inclusion of mPCMs provides latent heat storage capability, offering potential benefits for energy‐efficient construction materials. The CAC used in the formulations contains a minimum alumina content of 50%, and the mineralogical characteristics of both CAC and WPC were determined by XRD–Rietveld analysis.

Printability requirements for extrusion-based additive manufacturing were evaluated through extrudability, buildability, workability loss, open time, green strength, and early-age compressive strength. The results demonstrate that the combined use of CAC and WPC induces the thixotropic behavior essential for maintaining structural stability during layer-by-layer deposition. The designed mortar mixtures exhibited sufficient flowability for extrusion while achieving high green strength to ensure dimensional stability. Furthermore, the incorporation of mPCMs was found to enhance buildability, indicating their potential to improve the performance of 3D-printed cementitious systems.

Speakers: Mr Ahmet Selim Engin, Ms Melike Sucu, Sibel Sönmez (Çimsa Çimento)

17 Review of conversion of calcium aluminates cements: What data science could bring?

During decades, calcium cements had been studied as a simple case to study hydration of more complex multiphase cements such as Portland cement, due to its very quick hydration and apparent simple chemistry. The strong dependence of temperature on mechanical strengths development was quickly noticed with unexpected regression of mechanical strength with time when initial hydration proceeds at low and room temperature.
A significant amount of studies were run since, with different curing conditions, sample sizes and analyses of hydrates (DTA, DTG, XRD, microscopy, synchrotron …). Temptative models were proposed to describe hydration and strength development.
This paper provides an approach to combine data science (statistical tools), old experiments (data) and scientific descriptors (models from literature) to assess hydration and its impact. This approach could be useful for other blends of cements used in oil well industry, when temperature profile could have a significant impact on hydrates stability.

Speaker: Mr Bruno Espinosa (-)

18 Effects of silica nano-particles on hydration properties, microstructure and strength of calcium aluminate cement

Abstract: Hydration phenomena of a commercial white calcium aluminate cement (CAC (Górkal 70); Al2O3 – 69–72%) at 20°C was modified by adding silica nanoparticles addition in varying amounts and additives in the context of using CACs in the aspiration to achieve climate neutrality and the goal of net zero. The hydration process of CAC modified with silica sol (SS) was tracked by heat flow calorimetry, XRD and SEM experiments supplemented by mechanical strength determination at different curing ages. The findings demonstrate the potential to modify the traditional early (24 hours) hydration pathway of CAC-based systems by both SS and additives, leading to an accelerated process, in terms of the second exothermic peak of paste, and improved mechanical strength, even though no crystalline hydrates were formed. The results indicate that the evolution of the hydration is closely related to the effect of the SS content and additives on the densification and microstructure properties. CAC-based mortar containing 5 wt.% SS and additives exhibited the highest compressive strength, suggesting that early strength development may be attributed to silica nanoparticles acting as a filler. It is also evident that silica sol promotes the formation of CAH10 rather than C2AH8. All binder systems remain strength increase when exposed to 28-days curing conditions.

Speaker: Renata Boris (PhD)

19 Hydration Kinetics and Reactivity of Ternary Binders Based on Ground Granulated Blast Furnace Slag for Low-Carbon fast setting binder

Ternary binders are frequently used in fast-setting applications, such as rapid tile adhesives, where high early-age performance is required. In this context, the incorporation of ground granulated blast furnace slag (GGBS) offers an effective pathway to reduce the carbon footprint of construction materials, while maintaining reactivity and durability.
This research focuses on evaluating the hydration potential of a GGBS-rich ternary binder composed of calcium aluminate cement (CAC), calcium sulfate (C$), and GGBS. Hydration kinetics are investigated using isothermal microcalorimetry, and the mechanisms of phase formation are studied through microstructural characterization techniques, including X-ray diffraction (XRD) and magic-angle spinning nuclear magnetic resonance (MAS-NMR) of 27Al and 29Si.
The results highlight the effective reactivity of GGBS under the specific conditions and its significant contribution to the hydration process and the final properties of the binder system.

Speaker: Dr Yasmine Kaci (Ecocem)

20 Hydration of CAC-alumina systems in the presence of silica fume

The study is focused on how the hydration of a refractory binder system consisting of commercial white CAC and tabular alumina is changed by the addition of different silica fumes. Four silica fumes, two each of identical quality grade, but obtained from different batches, were selected and characterized by their physical and chemical properties (XRF, laser granulometry, BET). Then they were added to the system with a SF/CAC ratio of 1 and w/c of 1.4 at 23 °C. Even though no clear differences could be observed between the fumes of the same grade with regard to chemical bulk analysis and specific surface area, they exhibited different rheological behavior after paste preparation. To examine this, the hydration was followed via heat flow calorimetry, in-situ XRD and pore solution analysis. Additionally, hardness development within the first hours of hydration was measured with a Gillmore-needle device (IMETER).
It was found that the mixes with lower viscosity show an additional heat flow event located between the initial heat flow after mixing and the main reaction. This intermediate event is likely correlated to an initial dissolution of CA, which occurs directly after water addition in the mixes without this event. Also, an increased rate of hardness development was observed during the intermediate event. A potential link to the amount of dissolved silicon provided by the silica fumes shown in the pore solution data was examined by adding solutions containing low amounts of sodium silicate to the mixes. By this, the event could be induced in the two systems previously not showing this reaction. Higher concentrated solutions retard the hydration until a critical point, where the main reaction is eventually suppressed for at least 48 h.

Speaker: Tillmann Schramm (Mineralogy, Friedrich-Alexander-University Erlangen Nürnberg)

15:45 Break

Ettringitic Systems 1

Conveners: Prof. Friedlinde Götz-Neunhoeffer (Mineralogy, Friedrich-Alexander-University Erlangen Nürnberg), Marijana Serdar (University of Zagreb Faculty of Civil Engineering)

21 Ettringite systems - Microstructure, Performance and Characterization Techniques

With the cement technology moving towards low embodied CO2 cements, optimization of ternary binders composed of Portland cement (PC)-Calcium aluminate cement (CAC) and calcium sulfate (C$) that meet the sustainability need becomes relevant. Previous reports demonstrate that replacement of CAC by slag, silica fume or fly ash hinders the conversion process. However, the incorporation of SCMs in PC-CAC-C$ ternary binders, has been overlooked.
This study, examines the role of limestone and metakaolin as cement substitute in CAC-PC-calcium sulfate ternary binders. Combinations of CAC-PC-C$ with amounts of 5 up to 25% wt.% metakaolin/limestone were investigated in terms of heat evolution, setting time, phase formation, dimensional stability and strength development up to 90 days of hydration.
Within the first 24 hours of hydration both metakaolin and limestone lead to an acceleration of the heat of hydration, presumably serving as nucleation sites.
Compressive strength increased by ~ 36%, in the metakaolin based compositions over 90 days compared to the control, while shrinkage was mitigated. No major difference between samples with 5, 15 and 25 wt.% of substitution were observed, hence indicating that that even small additions are sufficient to achieve an improvement in strength. Formation of AFm-carbonate equivalent phases was favored in presence of limestone, whereas the use of metakaolin enhanced strätlingite formation. The content of AH3 decreased with the increase of substitution level.
The study suggests that mainly metakaolin has a profound influence on the hydration and resulting microstructure of CAC-rich ternary binders. This can be used as a tool to maximize the use of SCMs in such ternary binders for environmental benefits

Speaker: Elsa Qoku (Institue for Building Materials Research (ibac))

22 Development of temperature-dependent phase composition during hydration of ternary OPC-CAC-C$ mixtures with two different CAC types

Ternary mixtures composed of calcium aluminate cement (CAC), Portland cement (OPC) and calcium sulfates (CS) are commonly used as tile adhesives, self-levelling compounds, repair cements or technical mortars. Different setting and hardening times as well as expansion, shrinkage and early strength can be easily controlled by varying the proportions of the three components. Many studies have shown that formation of different hydrate phases in the mixtures is strongly influenced by both the OPC/CAC and the CAC/CS ratio. In general, calcium aluminates (C3A and/or CA) can react with the calcium sulfate, which is leading to formation of ettringite. However, the quality of the CACs, which is related to the reactive clinker composition, also has an effect on the composition of the phase formed during and after hydration in the mixture. Depending on the CAC and C$ content or limestone addition (Cc), the conversion of ettringite to AFm (monosulfate or -carbonate) can also be accelerated or prevented.
The influence of two different CACs (iron-containing and iron-free) on the hydration of application-related ternary mixtures was therefore investigated. The reaction kinetics were determined using heat flow calorimetry and quantitative x-ray diffraction analysis (QXRD). Storage samples for up to 90 days at 10 °C and 23 °C were examined with G-factor method in order to clarify the influence of the CA and iron content of the respective clinker on the stable hydrate phase composition and on the amorphous phase content. It could be shown what differences in the phase composition occur during storage at 10 °C or 23 °C. In addition, strength measurements could provide further insights into the influence of the various CACs on the development of strength during hydration.

Speaker: Pauline Rost (Friedrich-Alexander-Universität Erlangen-Nürnberg)

23 Controlled calcium sulfoaluminate synthesis and influence of superplasticizers on the formation kinetics

Ettringite (AFt) is a key phase influencing the early-stage hydration and rheology of calcium aluminate, calcium sulfoaluminate and blended cements. However, a quantitative and mechanistic understanding of early-stage hydration - specifically nucleation and growth- remains unclear, which is fundamental for optimizing the material performance.

In this study, we have developed the synthesis of AFt in a highly controlled, dilute system with titration-precipitation, enabling in-situ monitoring of physiochemical process using Ca ISE (ion selective electrode), pH, optical and conductivity electrodes every 5 seconds. The time-resolved data from this process is further implemented into a thermodynamic-kinetic model framework based on classical nucleation theory and population balance method, evaluating physically significant parameters such as solubility product, interfacial energies, alongside nucleation kinetics.

The prime focus of this study is to understand the influence of superplasticizers, essential for rheology control, yet reported to be detrimental for cement hydration. Various polycarboxylate ethers (PCEs) were studied in the controlled titration precipitation method, revealing that PCEs not only alter the nucleation, causing delay, but also stabilize in a highly sulfated system the thermodynamically less stable phase, monosulfate (AFm), by altering the nucleation sites. This kinetic inhibition is observed to have a concentration dependence, leading to a shift in the distribution of AFt and AFm phases.

TEM evolution over the solid formation revealed the simultaneous formation of both phases, without intermediate transition, influenced by the local supersaturation. Thermodynamic-kinetic modelling accurately described the early formation stages - nucleation and growth, resulting in reasonable thermodynamic parameters. These results offer crucial insights into early-stage physicochemical process, which could optimize the usage of various superplasticizers and workability in blended cements.

Speaker: Hari Priya Ravindran (PSI, EPFL)

Wednesday 10 June

08:30 Coffee

Ettringitic Systems 2

Conveners: Charles Alt, Frank Winnefeld (Empa)

24 Understanding the strength development of self compacting concrete formulation incorporating calcium aluminates as strength booster

In an increasingly competitive market, the precast industry is constantly looking for ways to ensure a quick turnaround and rapid delivery with an acceptable cost and without harming the quality of the final concrete element. One of the most common levers allowing to boost production cycles is to adopt advanced curing techniques like steam curing or heat curing. These options are not effective in terms of cost and CO2, but still a common practice used when quick formwork removal is needed.
To increase productivity a potential solution that consists in incorporating calcium aluminates as strength boosters is proposed. A complementary study showed that incorporating calcium aluminates in a self-compacting concrete (SCC) formulation for the precast industry led to an improvement of the resistance to chloride and had no significant effect on carbonation. The focus of this study is to investigate the strength development of a self-compacting concrete (SCC) formulation for the precast industry including 50kg/m3 and 100kg/m3 calcium aluminates as Portland cement substitute.
Compressive strength results carried out from 6h and up to 180d show respectively 7.8MPa and 16.7MPa for the system containing 50 and 100kg/m3 at 6h. On the other hand, the reference shows no strength development at 6h. At 180d, the three tested systems have close strength values with no strength decrease for accelerated systems over time. Bound water correlates well with the strength results. XRD-Rietveld quantification shows that in the boosted systems, ettringite is the main crystalline hydrate forming and no conversion products (C3AH6, C2AH8, CAH10) are formed. Mercury Intrusion Porosimetry measurements show that porosity keeps refining between 28d and 180d for the reference mix and the system containing 50kg/m3 of calcium aluminates accelerator. The total porosity is also reduced. This is explained by a further hydration of the silicates phases.

Speaker: Sarra El Housseini (Imerys) (Imerys)

25 Hydration Behavior of Quaternary CAC-OPC-C$-SCM Systems Incorporating Supplementary Cementitious Materials under Variable Curing Temperatures

TThis study investigates the hydration behavior of quaternary binder systems comprising calcium aluminate cement (CAC), ordinary Portland cement (OPC), calcium sulfate (C$), and various supplementary cementitious materials (SCMs) under different curing temperatures. The binder composition was fixed at CAC:OPC:C$:SCM = 53:13:24:10 by mass. SCMs, including ground granulated blast furnace slag (GGBFS) and limestone, were selected to evaluate their influence on hydration kinetics, phase development, and strength progression. Natural gypsum was used as the calcium sulfate source. To assess the temperature sensitivity of each formulation, curing was carried out at 5 °C, 25 °C, and 45 °C. Isothermal calorimetry was used to monitor hydration reactions, while crystalline phase evolution was tracked via X-ray diffraction (XRD) at 1, 3, 7, and 28 days. Additional analyses included thermogravimetric analysis (TGA), setting time (Vicat), and mechanical performance testing at 28 days. Results showed that both the SCM type and curing temperature significantly affected hydration kinetics and product formation. Slag enhanced early-age reactivity and caused earlier setting, particularly at elevated temperatures. In contrast, limestone exhibited delayed hydration, especially at lower temperatures. The interaction between SCMs and temperature also influenced the extent of ettringite formation.

Speaker: Özge Demirdogan (Sabanci Technology Center GmbH - Middle East Technical University)

26 Ettringitic Accelerators: An Advancement for Cementitious Foams

Cementitious foam technology, despite being known for decades, has faced limitations in widespread use due to technical challenges. The main issues include slow setting and hardening, low mechanical performance at early age, particularly in low-density foams, as well as shrinkage problems, and limited application range.
To address these challenges, an ettringitic accelerator based on amorphous calcium aluminate is proposed. It has shown promising results in improving foam performance: such as faster structuration and hardening kinetics, enhanced mechanical resistance, reduced shrinkage and lower residual moisture. Various analytical techniques have been employed to understand the mechanisms behind these improvements including rheological measurements under oscillatory conditions, early age dimensional variation measurements (under endogenous and drying conditions), optical and SEM observations, temperature monitoring and mineralogical characterizations. The enhanced cementitious foams show potential for applications in thermal insulation, high-rise construction and to contribute to more efficient and sustainable construction practices.

Speaker: Mr Jean-Noël Bousseau (IMERYS)

27 Fast and stable: Calcium aluminate cements as accelerators in highly heat-insulating mineral foams

In recent years, the increasing requirements for thermal insulation in building construction and society's growing environmental awareness have led to the increased development of highly thermally insulating, recyclable cement-based mineral foams with low thermal conductivities (λ ≤ 0,035 W/(m·K)) and low dry densities (ρ ≤ 70 kg/m³). Their production and application are associated with several challenges. One of the main ones is the stabilization of the pore structure through early and rapid structure formation, which can be solved by using CAC as an accelerator system.

The IAB has developed a patented manufacturing process for mineral foam in which two mineral foams are continuously and controllably mixed together. While the binder of one mineral foam can be an OPC, the second mineral foam is based on a CAC. By combining the two mineral foams in a targeted manner, the start of the structure formation can also be adjusted during the manufacturing process depending on the building materials to be filled and the ambient conditions. The user of this process is free to select the raw materials independently, but this requires specific expertise and suitable methods.

Through extensive research and development work in cooperation with its partners, the IAB investigated different binder combinations of OPC and CAC. It was found that laboratory tests are already sufficient to estimate and monitor the foam stability and setting behavior of industrially produced mineral foams. First and foremost, rheometric measurements to characterize the setting behavior of the binder suspensions and the mineral foams should be mentioned here.

The knowledge gained contributes both to resource efficiency in mineral foam production and to the wider application of this technology, which has the potential to sustainably increase the energy efficiency of buildings.

Speaker: Klemens Laub (IAB – Institut für Angewandte Bauforschung Weimar gGmbH)

Ettringitic Systems 2: Posters

10:40 Break

28 Calcium Aluminate Cement saving potentials in Building Chemistry products

The incorporation of Calcium Aluminate Cements (CACs) into modern building chemistry products enable rapid set, fast hardening and quick drying. Apart from application demands, the CO2 footprint of the products needs to be lowered as well to minimize climate impact. One avenue to reduce CO2 is to decrease the cement content in the product formulation. The patented CAC Flex offers a solution due to its high reactivity. Its key properties are characterized in the first part of this study.
In the second half, the cement saving potentials of CAC Flex are demonstrated by a comparison with CAC 50 and CAC 505 in a Self-Levelling Compound (SLC). The highly efficient CAC 505 offers increased cement fineness when compared to the reference CAC 50. It enables the formulator to decrease cement in the SLC recipe by 10 % without sacrificing performance. The newly developed and patented CAC Flex combines the increased cement fineness with a higher content of the main reactive phase CA. As a result, SLCs containing CAC Flex perform better than the reference even after reducing CAC in the recipe by 20 %. The in-situ XRD and calorimetry investigations presented give insights in SLC phase development and reaction kinetics.

Speaker: Alexandra Gerz (Calucem d.o.o)

Biogenic Corrosion

Convener: Robert Fetter (IAB – Institut für Angewandte Bauforschung Weimar gGmbH)

29 Performance Based Assessment of Novel Cementitious Materials for Sewer Infrastructure

Civil infrastructure assets such as underground pipes, manholes, access chambers, and pumping stations are frequently exposed to aggressive environments including sulphates, chlorides, and biogenic sulphuric acid. Traditional general-purpose (GP) and blended (GB) cements often lack the chemical resistance needed, leading to shorter service life and higher maintenance costs. This study evaluates commercially available specialty binders—calcium aluminate cements (CAC) and geopolymers—as durable, cost-effective alternatives for precast sewer infrastructure.
Assessment followed Australian standards AS 4198, AS 3600, WSAA codes WSA 160 and WSA 161, and Holcim’s casting requirements. Durability was evaluated through in-situ exposure in operational sewers with varying corrosion severity and accelerated laboratory corrosion testing. For casting suitability, high-performing binders were used in concrete mixes with natural coarse sand from Clarence Quarry and granite aggregates from Lynwood Quarry. These mixes were tested for workability, early strength development, and other key production and performance properties critical for efficient casting, demoulding, and safe handling.
Key durability factors were grouped as chemical stability (binder convertibility and phase development), microstructural characteristics (porosity and aggregate compatibility), mechanical performance (compressive strength), and acid resistance capacity.
Results demonstrate that select specialty binders meet both durability and casting requirements, supporting their use in wastewater infrastructure. While long-term field validation continues, current data provide a strong foundation for integrating high-performance, commercially available binders into Australian sewer networks.

Speaker: Marjorie Valix (The University of Sydney)

30 Modeling CAC Mortar Degradation under Acetic Acid Exposure

The degradation of concrete due to acid attack is commonly assessed by the depth of deterioration from the original surface. This study evaluates the applicability of a simple diffusion-based model to determine the apparent diffusion coefficient (D_app), comparing it to an empirically modified square-root-of-time approach from the fib Model Code 2020. Model calibration was based on accelerated laboratory experiments in which calcium aluminate cement (CAC) mortar specimens were immersed in 1.0 M or 0.10 M acetic acid solutions for two consecutive 22-day periods, with solution replenishment between phases. Degradation was monitored through pH changes, mass loss, and microstructural/chemical deterioration depth analyses. Elemental concentration profiles, obtained via electron probe microanalysis (EPMA) and processed through a newly developed image analysis algorithm, quantified decalcification and dealumination across the degradation front. These data enabled calibration of model parameters, supporting a robust comparison of modeling approaches for predicting acid-induced CAC mortar degradation.

Speaker: Neven Ukrainczyk (TU Darmstadt)

31 Understanding biodeterioration mechanisms of a calcium aluminate–based coating affected by substrate cracking

Calcium aluminate cement (CAC)-based coatings have demonstrated superior resistance to microbially-induced concrete deterioration (MICD) in wastewater infrastructures and are widely used to protect Portland cement-based concrete The key factor in the resistance of CAC lies in its chemical and microstructural nature. However, in the penalizing case of crack initiation within the underlying substrate, cracks might propagate into the coating and act as pathways for aggressive agents. This study investigates the behavior of a thin sprayed CAC-based coating, applied to new wastewater infrastructures, in the presence of cracks to understand the mechanisms that govern the coupled effect of cracks and biodeterioration. Representative cracks were generated in coated mortar specimens using a displacement controlled three-point bending test, producing different crack width ranges: 150-200 µm (complying the Eurocode 2 recommendations), 400-500 µm and beyond than 700 µm. These specimens were exposed to different campaigns of the BAC test, which reproduces the aggressive conditions encountered in sewer networks. During the exposure period, the leaching solutions collected from the exposed surfaces were analyzed followed by microstructural and chemical analyses of the structure using coupled SEM-EDS analysis. Coated specimens with crack widths > 400 µm showed a slight increase in Ca and Al leaching, yet leaching remained lower than in uncoated specimens. Moreover, SEM-EDS observations revealed the formation of newly precipitated phases within crack openings, composed mainly of calcium, aluminum and sulfur with molar ratios close to those of ettringite. These phases are suggested as a potential physical barriers, limiting the penetration of aggressive agents and contributing to the crack sealing of the coating in the stated conditions of exposure. This study not only provides insights into the performance of calcium aluminate-based coatings under biodeterioration in presence of cracks but also opens new perspectives on the crack healing potential of these materials in wastewater environments.

Speaker: Dr Reem Hoballah (INSA Toulouse)

32 A Framework for Classifying Sewer Gas-Phase Corrosivity Based on Material Response

Concrete, protective coatings, and other construction materials deteriorate under biologically induced corrosive conditions commonly found in sewer systems. Understanding "corrosivity"—the severity of corrosion in a given environment—is essential for selecting appropriate materials, designing mitigation strategies, and estimating service life and lifecycle costs.

This study focuses on sewer-related corrosion of concrete infrastructure, including large-diameter pipes, access chambers, and wet wells. Degradation is primarily driven by microbial activity that produces sulphuric acid under specific environmental conditions.

A quantitative classification of sewer gas-phase corrosivity was developed using field data from ordinary Portland cement (OPC) assets in service for 17 to 81 years across Australian utilities. The classification was based on the relative depth of corrosion observed as a function of measured environmental parameters—specifically H₂S, CO₂, temperature, and relative humidity. These environmental conditions were used as surrogate indicators of corrosivity.

To validate the classification and assess its application to material selection, a range of commercially available materials—including calcium aluminate and geopolymer cement-based systems—were installed in sewers with different corrosivity classifications. Comparative observations across these environments demonstrated meaningful differences in material performance, confirming the classification’s practical relevance.

The findings show that environmental conditions can be effectively used to predict relative corrosivity in sewer networks, and that material performance varies significantly with exposure severity. The proposed classification offers engineers and asset managers a robust tool for aligning material selection with environmental conditions, improving durability, optimising lifecycle costs, and supporting resilient wastewater infrastructure.

Speaker: Marjorie Valix (The University of Sydney)

33 Study of the durability of calcium aluminate cement on wastewater treatment plant

Urbanisation is leading to the installation of increasingly efficient wastewater treatment systems to limit discharges into the natural environment. To date, concrete biodeterioration in relation to wastewater treatment systems has been studied mainly in sewer networks, where it has been linked to biological activity in the presence of hydrogen sulphide, leading to irreversible damage. However, new types of degradation of concrete structures have been observed in wastewater treatment plants, mainly in nitrifying and denitrifying units that treat wastewater containing nitrogen compounds (ammonium and nitrate). This treatment permit to transform ammonium to nitrite and then nitrate by bacteria in aerobic condition. The second treatment permit to transform nitrate to nitrogen in anaerobic condition by bacteria. In contrast to sewer networks, the exact causes of these degradations are not yet known.
In order to understand these biodeterioration mechanisms and the durability of binders, samples of mortars based on two different binders (CEM I and CAC) were exposed in 6 different nitrogen pollution treatment basins within the SIAAP. These tanks differ in terms of process: nitrification or denitrification and the presence or absence of biomass support (free or fixed culture). The samples were monitored macroscopically (photos, mass, diameter and surface pH) for 3 years. Each 6 months, the samples were sawed and then analysed by SEM-EDS and micro-raman.
The results showed that decalcification of the cement matrix was exacerbated in the nitrification fixed culture tanks. After more 3 years of exposure, the CAC mortars are more resistant to this biological attack in the presence of nitrifying bacteria than Portland cement-based mortars.

Speaker: Marielle Guéguen Minerbe (Université Gustave Eiffel)

13:05 Lunch

Carbon Footprint

Conveners: Kimberly Kurtis (Georgia Institute of Technology), Matthew Adams (New Jersey Institute of Technology)

34 Sustainable Calcium Aluminate Cement Formulations: Partial Clinker Replacement with Activated Chemicals

Reducing the clinker content in calcium aluminate cement (CAC) is crucial for improving environmental sustainability. This study investigates the partial replacement of CAC clinker with activated pumice to optimize setting time and mechanical strength. Experiments were conducted by gradually decreasing the clinker content and replacing it with varying proportions of activated pumice. The hydration kinetics, setting behavior, compressive strength, and microstructural evolution were analyzed.

Results show that, despite a significant reduction in clinker content, early and long-term strength values were maintained when using properly activated pumice. The reactivity of pumice influenced the formation of hydration products, particularly promoting the development of phases such as CAH₁₀ (calcium aluminate hydrate) and C₂ASH₈ (stratlingite). Additionally, the setting time was found to depend on the surface activity and chemical composition of the pumice.

This study demonstrates that clinker substitution in CAC-based systems is feasible, and mechanical performance can be preserved using activated pumice as a supplementary material. The findings provide a foundation for developing low-carbon cement formulations. Future research should explore the effects of different activators and curing conditions.

Speaker: Buket Polat (Cimsa Cement)

35 Beyond Pozzolanicity: Metakaolin is key to the Surface Aspect of Sustainable Flooring Mortars based on Ternary binders

Specialty binders for premium drymix products commonly consist of a “ternary” blend of calcium aluminate, calcium sulfate and Portland cement. Target performance for each application is achieved by carefully tuning the relative proportions of these constituents together as well as the type & dosage of several set regulators. Simple substitution of CEM I by a blended Portland cement to lower carbon footprint therefore perturbs this balance and can be counterproductive — altering paste rheology, surface appearance and early strength that are critical for drymix formulations — unless the mix design is re-optimized.

Because the clinker content of the overall drymix largely governs its carbon footprint, we present several low-clinker mix designs that preserve or improve key functional properties while reducing footprint by 35%–40% relative to reference formulations.

We further investigate the effect of metakaolin (MK) on these mix-designs, beyond its pozzolanic contribution, and demonstrate a direct beneficial effect of MK on surface quality and abrasion resistance of self-leveling compounds formulated with these designs. Microstructural and phase analyses combined with rheological characterization elucidate the role of MK and its influence on early-age properties, workability and strength development. The results indicate viable pathways to substantially lower clinker content in premium drymix products, while improving the set of performance of the ternary binders.

Speaker: Alexandre Franceschini (Imerys)

36 Panel: Embodied CO2, Sustainability - Producers

Speakers: Kimberly Kurtis (Georgia Institute of Technology), Matthew Adams (New Jersey Institute of Technology)

18:30 Gala Dinner

Thursday 11 June

08:30 Coffee

Durability 1

Conveners: Marjorie Valix (The University of Sydney), Thano Drimalas (University of Texas at Austin)

37 Calcium Aluminate Cements in Context: Comparative Performance for Conventional Concrete Applications

Calcium aluminate cements (CACs) are often treated as specialty binders, but recent work suggests their performance merits broader consideration. Drawing on testing funded by the U.S. Federal Highway Administration and recently published in a comprehensive report (FHWA-HRT-24-012), we compare CACs to portland cement, calcium sulfoaluminate (CSA), magnesium phosphate cements, chemically activated binders and other alternative binders across key metrics: mechanical property development, chemical resistance, and long-term durability. CACs are known to offer clear advantages—especially where early strength, sulfate resistance, or performance under elevated temperatures is critical. This research also demonstrated that CACs can also offer excellent resistance to chloride ingress, potential to limit ASR expansion of reactive aggregate, low shrinkage and flexibility in set time when used with appropriate chemical admixtures. Still, the data reinforce that no single binder is universally superior, with the demands of the application necessitating weighing of different performance measures. This presentation outlines the performance envelope of CACs relative to other systems and identifies where their use may offer the greatest benefit in cast-in-place and other conventional concrete construction.

Speaker: Kimberly Kurtis

38 Ultra-Rapid Hardening Repair Mortar with Amorphous Calcium Aluminates for Freezer Floor Applications at -25°C

Repairing damaged flooring inside commercial freezer warehouses presents significant challenges due to the extremely low temperature conditions, often below -25°C. This study presents the development of a self-leveling, ultra-rapid hardening mortar designed specifically for subzero applications. The binder system is based on amorphous calcium aluminates (ACA), which exhibit high reactivity and excellent early-age performance under low-temperature environments. The formulation was optimized to ensure flowability and high early strength without the need for external heating.

Laboratory tests evaluated the hydration kinetics, setting time, and mechanical properties of the mortar at -25°C conditions. Results demonstrated that the ACA-based system achieved initial set within 10 minutes and compressive strength exceeding 30 MPa after 3 hours, even under freezing conditions. The product has been successfully applied in a real-world industrial freezer setting, confirming its practical utility and performance.

This paper highlights the potential of ACA as a next-generation binder for cold-environment infrastructure repair and contributes to expanding the scope of high-performance calcium aluminate-based materials.

Speaker: Dr Tomoki Katagiri (MU MATEX Co., Ltd.)

39 Durability of concrete containing calcium aluminate-based mineral accelerator

Abstract

Speaker: Barbara Benevenuti (Imerys)

40 Poster Pitches

10:20 Break

41 Mathematical Modeling of Thermal Effects in Calcium Aluminate Cement

This paper presents a mathematical model developed to investigate the thermal modeling of calcium aluminate cement (CAC). A control volume is employed to simulate the heat balance behavior in CAC blocks with dimensions of 16 cm × 4 cm × 4 cm. These blocks were exposed to a constant temperature of 1450 °C to analyze the thermal effects during times.

Figure 1- The one-dimension control volume

Applying a heat balance approach to the control volume leads to the temperature distribution formula shown in Equation (1)

(1)

This partial differential equation is solved using an explicit finite difference method, assuming uniform boundary and initial temperatures

(2)

The CAC used in this study contains 50% Al₂O₃. The mixtures consist of 150 g of calcium aluminate cement with 450 g of silica sand and 75 cc of water are cured in a chamber maintained at 20 ± 1 °C and 90% relative humidity for 24 hours. The blocks were then exposed to uniform heat at 1450 °C for different time intervals.
Figure 2 illustrates the temperature distribution across the x-direction of the blocks over time. After 8 hours, the temperature becomes uniform.

Figure 2- Variation of temperature inside CAC blocks

Mechanical strength of different blocks (σc) is measured and the following empirical exponential decay formula is developed. Where, σ0 is initial mechanical strength (MPa), φ is porosity and m is constant (here is 0.55 to yield the best fit for experimental data, see Figure 3)

(3)

Porosity is calculated using a straightforward approach.

(4)

Figure 3- Mechanical strength prediction

The mechanical strength degradation is attributed to phase decomposition, porosity increase, cracks, and loss of ceramic bindings.
Effects of changing the physical parameters of the CAC like conductivity, density, and heat capacity can be investigated simply by changing them in the model.

Speaker: Hamidreza Karami (Quality Control Manager, Modalal Cement Co. Kermanshah, Iran)

42 Utilization of Granulated Slag as Aggregate and Alumina-Bearing SCM in Cementitious Systems

This study explores the valorization of a water-granulated platinum slag (GPS) as both a fine aggregate replacement and a supplementary cementitious material (SCM) in mortar formulations. The slag, a byproduct of platinum smelting operations, contains high amorphous content and elevated MgO and Al₂O₃ levels—making it a potential contributor to cement chemistry when properly processed.
The GPS was tested in two ways. First, as a sand substitute (0-100%) sand replacement, and second, ground to make ground granulated platinum slag (GGPS) as a 30% Ordinary Portland Cement (OPC) replacement. Three mortar systems were developed: (i) OPC-only, (ii) OPC with 30% fly ash, and (iii) OPC with 30% GGPS. Mixes were evaluated for workability, compressive strength, alkali-silica reactivity (ASR), and autoclave expansion.
ASR testing showed that GPS used as sand replacement resulted in excessive expansion (>0.2%), but this was effectively mitigated with the addition of fly ash, enabling up to 100% sand replacement without compromising performance. Autoclave expansion remained within acceptable limits in all cases, indicating mineralogical stability despite high MgO content. The GGPS exhibited a Blaine fineness of 441 m²/kg and was found to be chemically active, with favorable ASR suppression and strength comparable to control mixes.
These results support the use of alumina-bearing GPS and GGPS as promising, industrially sourced SCMs that can help cement manufacturers reach their sustainability and decarbonization goals. Ongoing work is focused on optimizing hybrid binder systems (e.g., fly ash + GGPS) for improved performance in durable and resource-efficient calcium aluminate-based systems.

Speaker: Ms Kelly Lau (Insight R&D)

43 Comparison of Durability of Calcium Aluminate and Sulphoaluminate Cements (CAC, CSA and HB-CSA) for Aggressive Environment

Concrete made from traditional Portland cement in the sewer system faces severe corrosion. This leads to deterioration of Portland cement, causing a reduction in sewer pipes and an increase in maintenance and repair costs. This research addresses a pertinent issue by evaluating three types of specialty cements: calcium aluminate cement (CAC), calcium sulphoaluminate cement (CSA), and high-belite calcium sulphoaluminate cement (HB-CSA). These materials underwent durability tests under conditions that simulate the environment of sewer systems, utilising laboratory-based methodologies. The findings were unexpectedly significant; in the accelerated corrosion tests conducted in the laboratory, CAC demonstrated superior performance compared to the other types. The results indicate that CAC exhibits enhanced durability in acidic environments, significantly surpassing the performance of Portland cement. CAC offers the densest and most chemically inert matrix, making it particularly suitable for the most challenging conditions. In comparison, HB-CSA provides a moderate level of acid resistance. In addition to this test, sorptivity, compressive strength tests, alkali-silica reactivity (ASR-AMBT), and water absorption were also measured. In CAC and HB-CSA, water absorption was around 5%, whereas for CSA it was slightly higher, around 7%. For sorptivity, all three binder systems were within the range of <6mm/√h. Strength development for this study was recorded at 1 and 28 days for mortar and concrete samples.

Speaker: Mr Bishwjeet Binwal (School of Chemical and Biomolecular Engineering, The University of Sydney)

CAC 2026 Extended Abstract_V1 (1)_MV.docx

44 The durability of CAC compared to Portland cements in cases of biodegradation

The biodeterioration of cementitious materials in the wastewater treatment cycle is caused by the biological acid produced by microorganisms. In the case of sewage systems in presence of H2S, sulfuric acid was produced by sulfo-oxidizing bacteria, and in the case of nitrogen pollution treatment in water treatment plants, is nitric acid produced by bacteria. The literature shows that cementitious materials based on calcium aluminate cement (CAC) have better durability than ordinary Portland cement (OPC). However, few studies attempt to explain this improved durability. Thus, mortar samples (CEM I, CEM V, and CAC) were exposed in both networks and wastewater treatment plants. Mineralogical analyses (µ-Raman, XRD, SEM) and physical parameters of the materials (water porosity, BET, mercury porosimetry) were carried out on the samples, before and after different exposure times. Results shows that CAC-type materials initially have finer and more tortuous porosity and microporosity than OPC cements. Furthermore, during biogenic attack on the materials, the calcium in the OPC phases is more easily leached than in the CAC phases, particularly due to the reprecipitation of AH3.These different parameters with the bacteriostatic effect of aluminum may explain the better durability of CAC.

Speaker: Dr Tony Pons (Université Gustave Eiffel)

Durability 2

Conveners: Barbara Benevenuti (Imerys), Sibel Sönmez (Çimsa Çimento)

45 Long-term Evaluation of Rapid Concrete Repair Systems

This study presents long-term durability findings for various rapid repair concrete systems subjected to over a decade of outdoor exposure in diverse environmental conditions. The systems evaluated include Calcium Aluminate Cement (CAC), blended CAC–Portland cement systems, and Calcium Sulfoaluminate (CSA) cement, benchmarked against conventional Portland cement concrete. Key durability mechanisms monitored were Alkali-Silica Reaction (ASR), External and Physical Sulfate Attack, Delayed Ettringite Formation (DEF), steel reinforcement Corrosion, and Carbonation. Results demonstrate that each alternative binder system exhibited distinct performance advantages under specific conditions. Overall, the findings highlight the potential of alternative cementitious systems to outperform traditional Portland cement in targeted repair applications, emphasizing the importance of selecting repair materials based on anticipated environmental exposures.

Speaker: Racheal Lute (University of Texas at Austin)

46 The effect of carbonation on calcium aluminate cement with the addition of slag and calcined clay

The durability of calcium aluminate cement in aggressive environments is considered one of its competitive advantages. A property that is attracting additional attention in concrete research today is resistance to carbonation, as cement-based materials play a role as carbon sinks in the carbon neutrality strategy. Previous studies have shown that CAC concrete has a faster carbonation rate compared to OPC concrete. However, there are no consistent conclusions on the effects of carbonation on the properties of CAC and limited knowledge on how SCMs affect the carbonation process when mixed with CAC. The present study focuses on the evaluation of the carbonation resistance of mortar based on CAC without and with the addition of slag and calcined clay. The influence of carbonation was investigated on non-conversion-promoted (cured at 20°C) and conversion-promoted samples (cured at 38°C). The experimental results show that accelerated carbonation has different effects on the microstructure and mechanical properties of CAC without and with the addition of slag or calcined clay.

Speaker: Marijana Serdar (University of Zagreb Faculty of Civil Engineering)

47 Freeze–Thaw Durability of CAC Assessed by Synchrotron Microtomography

The long-term performance of calcium aluminate cement (CAC) in cold environments depends critically on its resistance to freeze–thaw (F–T) cycles. This study evaluates the microstructural evolution and damage mechanisms in CAC mortars exposed to repeated F–T cycling. A combined analytical approach was applied to assess both phase changes and internal degradation.
Microstructural characterization was conducted using Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and scanning electron microscopy (SEM) to monitor hydration products, phase transformations, and surface-level microcracking. In parallel, high-resolution synchrotron X-ray microtomography was performed at the ALBA light source, enabling non-destructive 3D quantification of internal microporosity and crack formation.
The study reveals that freeze–thaw degradation in CAC is driven by phase instability and pore network evolution, with synchrotron microtomography exposing early-stage internal damage undetectable by conventional methods. These findings highlight the role of microstructural dynamics in durability and support the design of more resilient CAC formulations.

Speaker: Lucía Fernandez (universitat Politècnica de Catalunya)

48 Deep-sea Performance of High-alumina Calcium Aluminate Cement: Durability under 1000-2000 m In-situ Exposure

The advancement of deep-sea technologies, including subsea carbon storage, offshore wind energy, and seabed resource extraction, requires durable cementitious materials capable of supporting infrastructure exposed to extreme environmental stressors. This study investigates the durability and physicochemical stability of high-alumina calcium aluminate cement (AC) pastes under in-situ deep-sea oceanic conditions. Prismatic specimens (40 mm × 40 × 160 mm) of AC and Portland cement (PC) were submerged for one year at depths of approximately 1000 and 2000 meters in the Nankai Trough, Japan, where the water temperature (approximately 2 °C) and salinity (35 PSU) remained stable. Replicate specimens were exposed to laboratory immersion in seawater under ambient pressure and temperature to serve as a reference. Post-exposure analysis was conducted using scanning electron microscopy with energy-dispersive X-ray spectroscopy, electron probe microanalysis, and X-ray diffraction. PC paste specimens showed full-depth chloride ingress and severe surface degradation with alkali dissolution and extensive ettringite formation. In contrast, AC specimens exhibited minimal deterioration. Chloride ingress in AC was limited to approximately 10 mm from the specimen surface, while sulfate ingress was confined to the outer surface region. The primary hydrate phase, i.e., amorphous aluminum hydroxide, remained stable due to its low solubility in low temperature seawater. Slight expansion and cracking were observed. Fluorescence imaging confirmed that pressurized seawater fully infiltrated the AC specimen within one month, accelerating ion transport compared to ambient pressure conditions. However, strong chemical binding of chloride ions into calcium aluminate hydrates restricted chloride ingress. Furthermore, AC mortar was successfully applied in a pioneering deep-sea construction demonstration, connecting precast components at approximately 1000 m depth using a two-component injection system operated by a manned submersible. This study demonstrates that high-alumina AC exhibits exceptional chemical resistance, stability, and structural resilience under deep-sea exposure, offering a viable material for subsea infrastructure applications.

Speaker: Prof. Keisuke Takahashi (Kagawa University)

49 Conference Closing

Speakers: Elsa Qoku, Jason Ideker (Oregon State University), Matthew Adams (New Jersey Institute of Technology)

12:30 Farewell Lunch