Theodore Hanein

• Professor
• Chair in Construction Materials Science at University of Leeds

A method to synthesize high-purity ternesite is presented and the importance of reaction volume is highlighted; a brief description of the product morphology is also presented. Thermodynamic data for ternesite are derived and the limits of ternesite stability are then explored. An upper temperature stability limit of ≈1290°C at 1 atm is determined;...

Novel cement formulations based on calcium sulfoaluminate clinkers have significantly lower carbon dioxide emissions during production when compared against conventional Portland cement; however, there are no systematic studies of the environmental impact associated in producing these formulations. Previous studies are limited to qualitative eviden...

The proportions of cement clinker phases produced by the pyro-processing of a raw-material mix are often predicted through the Bogue equations, established in the 1930s; however, the Bogue approach is limited in its applicability. This presents a challenge as the cement industry is seeking innovative and more environmentally friendly cement clinker...

The calcination of calcium carbonate (CaCO3) is a major contributor to carbon dioxide (CO2) emissions that are changing our climate. Moreover, the calcination process requires high temperatures (~900°C). A novel low-temperature process for the decarbonisation of CaCO3 is tested whereby the CO2 is directly sequestered/mineralised in sodium carbonate...

The use of calcined clays as supplementary cementitious materials provides the opportunity to significantly reduce the cement industry’s carbon burden; however, use at a global scale requires a deep understanding of the extraction and processing of the clays to be used, which will uncover routes to optimise their reactivity. This will enable increa...

Lime (CaO) and soda ash (Na2CO3) are two foundational chemicals for modern civilization, and the CO2 emissions from their production processes are challenging to reduce. Furthermore, decarbonization of the lime industry could also reduce the CO2 emissions associated with cement production, for which lime is the key precursor. In this paper, we show...

An alternative low-energy alinite-chlormayenite clinker was produced and its hydration with different gypsum content was studied. The clinker was produced at 1225 • C using reagent-grade materials in an electric kiln with alinite, larnite, and chlormayenite content of 48, 24, and 16 wt%, respectively. The hydration kinetics of the clinker with diff...

This review by Working Group 1 of the RILEM TC 309-MCP discusses recent advances in the beneficial carbonation treatment of recycled concrete aggregates (RCA). The impact of carbonation on RCA properties as well as the microstructure and performance of concrete and other construction materials made thereof is critically reviewed. The increasing foc...

Portland cement (PC) has been used and developed since the early 19th century. Although the compositional ranges of PC clinkers are generally specified in standards, there is a lack of information on the variability of industrial clinkers. Furthermore, with an increase in the use of alternative mineral and fuel feeds, it is important to understand...

This study explores the use of Electric Arc Furnace (EAF) slag as a sustainable alternative raw material in cement clinker production. The research demonstrates the synthesis of ferrite-rich clinker using EAF slag, achieving a clinker composition of 47% alite, 32% ferrite, and 20% belite while replacing 20% of clinker raw materials i.e. limestone,...

Taking inspiration from the recent rise in interest on calcined clays, the RILEM technical committee RILEM TC 282-CCL on Calcined Clays as Supplementary Cementitious Materials has been summarising knowledge on a wide variety of topics related to the use of calcined clays in cement and concrete. In this article, the working group 2 of this committee...

Calcium sulfoaluminate (CSA)-containing cements have reported excellent characteristics across both early and later ages; however, there are a number of studies that display poor durability when compared to Portland cement (PC). Durability tests are used as an indicator for service life, and thus the viability of a cement system relies on its perfo...

The fast aging of existing building stock requires effective and sustainable strengthening solutions. Textile-reinforced mortars (TRM) have already proved to be very effective as well as versatile retrofitting solutions for reinforced concrete and masonry structures. TRMs can enhance the load bearing capacity of reinforced concrete structures; howe...

Iron is the fourth most abundant element in the Earth's crust, and cementitious materials are expected to contain iron-bearing phases, either in major or minor quantities. Iron-rich cement clinker is gaining attention because of its lower carbon footprint and higher sulfate resistance, while iron-rich resources are also increasingly being investiga...

Research into thermodynamic modelling allows for product and process optimisation of Portland cement clinkers. Due to the magnitude and chemistry of clinker production, there is a great challenge in modelling such a complex system. The CALPHAD (CALculation of PHAse Diagrams) approach provides a method in overcoming this challenge, by constructing a...

Alternative low-carbon cements can provide a short-term solution for emissions reduction but those cements gaining the most attention cannot achieve the highly desirable (and often necessary) early strength. Belitic calcium sulfoaluminate cement (BCSA) is a standalone cement that can provide this early strength, and that is its current unique selli...

Belitic calcium sulfoaluminate (BCSA) cement has been successfully used for the rapid rehabilitation of large concrete infrastructure such as runway or highway pavements. Typically, such projects require specifying rapid-strength concretes because pavement must be returned to service within a few hours of closure. For these applications, the compre...

M-S-H gels were synthesised via reaction of Mg(OH)2 with silica fume, cured at 35 C for up to 112 days, and their chemical and nanostructural evolution was examined. M-S-H gels with structural similarity to the thermodynamically stable serpentine group mineral lizardite were formed. Quantification of 25Mg and 29Si MAS and 1H 29Si CPMAS NMR, electro...

The use of calcined clays in construction materials has attracted significant attention in the last few years. Based on the continued need for sustainable construction materials to meet global development...

Many of the foundation industries are acting to tackle climate change in the UK and on a global level. The UKRI Foundation Industries Future Leaders Group explores how there are increased opportunities to share resources to move towards an industrial circular economy.

Reducing the CO2 burden of cement manufacturing can be achieved by increasing the ferrite content in cement as ferrite requires less calcium than other major clinker phases and thus reducing CO2 emission from limestone (mainly CaCO3) calcination. The steel industry produces vast and increasing amounts of EAF (electric arc furnace) slag that consist...

From materials for fusion reactors, photovoltaics and caloric materials, to new alloys for aerospace, there is no shortage of exciting challenges for materials scientists. Despite this surge of activity, materials research into experimental thermodynamics has been in steady decline for at least 30 years, and is under threat. An international team o...

The ongoing Syrian civil war began in 2011 and has left more than 130,000 buildings destroyed, 70% of which are RC buildings. When the war is over, it is estimated that the millions of displaced refugees will return within 8 years, thus requiring a rapid urban redevelopment of the country. This study examined the feasibility of reusing concrete fro...

The CO2 released upon calcination of limestone accounts for the largest portion of the emissions from the cement, lime, and slaked lime manufacturing industries. Our previous works highlighted the possibility for a no-combustion decarbonisation of CaCO3 through reaction with NaOH solutions to produce Ca(OH)2 at ambient conditions, while sequestrati...

The RILEM technical committee 282-CCL: Calcined Clays as Supplementary Cemen-titious Materials, investigates all the aspects related to calcined clays, from clay exploration and characterization to calcination process, hydration reactions and concrete properties. This white paper focuses on the hydration mechanisms of calcined clay-blended Port-lan...

The thermal treatment of limestone (mainly CaCO3) to produce lime (CaO) is a major contributor to CO2 emissions and the literature on decarbonising the lime industry is scarce. Subsequent hydration of lime would lead to the synthesis of slaked/hydrated lime Ca(OH)2; the production of a tonne of Ca(OH)2 emits ∼1.2 tonnes of CO2 arising mainly from t...

A background on non-Portland cementitious binders is presented, followed by a review of the key alternative binders that are currently of interest. The mineralogy of these cements is described, along with phases present in the reacted/hardened materials. The similarities and differences between the setting processes, as controlled by reactions at t...

Chemical precipitation is one of the most widely known methods for treatment of industrial wastewaters with high sulphate content, where sulphate can be precipitated as practically insoluble ettringite (Ca6Al2(SO4)3(OH)12·26H2O). This treatment method is also widely recognised for solidifying hazardous components and toxic elements e.g. arsenic in...

Burning of limestone is responsible of bulk of CO2 emissions from cement manufacture. Replacement of limestone with alternative raw materials could be a way to reduce CO2 burden. In conventional cement manufacture, iron is added to cement raw meal to enhance burnability during firing. The increase of iron in cement raw mix can lead to lower CO2 foo...

Decarbonizing calcium carbonate (CaCO3) is a crucial step for a wide range of major industrial processes and materials, including Portland cement (PC) production. Apart from the carbon footprint linked to fuel combustion, the process CO2 embodied within CaCO3 represents the main concern for the sustainability of production. Our recent works demonst...

The bulk of the cement industry's environmental burden is from the calcareous source. Calcium is mostly available naturally as limestone (CaCO3), where almost half of the mass is eventually released as CO2 during clinker manufacture. Iron (Fe) is the fourth most common element in the Earth's crust surpassed only by oxygen, silicon, and aluminium; t...

The decarbonisation of CaCO3 is essential for the production of lime (Ca(OH)2 and CaO), which is a commodity required in several large industries and the main precursor for cement production. CaCO3 is usually decarbonised at high temperatures, generating gaseous CO2 which will require post-process capture to minimise its release into the environmen...

The use of clays as resource of supplementary cementitious materials (SCMs) for a new generation of low-carbon cements and concretes is currently the subject of intense research efforts. To this purpose, a large number of clay resources have been explored, characterized and evaluated. This paper introduces the basic knowledge and concepts on clay o...

To respond to the rapid introduction and development of calcined clays as supplementary cementitious material (SCM), the toolbox of characterization methods for cementitious materials requires extension to raw clay characterization. Borrowing concepts and methods developed in the field of clay mineralogy, this paper outlines the merits and limits o...

Large quantities of concrete wastes are generated worldwide, and majority of them are currently land-filled. Nuclear industry is no exception - for instance in the UK, the decommissioning of Magnox reac-tors on 11 sites have already produced more than 1.3 million tonnes of concrete wastes. Storage of these wastes is challenging, not only because so...

The CO 2 released upon calcination of limestone (process CO 2 and combustion CO 2 ) accounts for the largest portion of the emissions from the cement manufacturing industry. Our previous works highlighted the possibility for a no-combustion decarbonisation of CaCO 3 through reaction with NaOH solutions to produce Ca(OH) 2 at ambient conditions, whi...

The acceleration impacts of calcium sulfoaluminate belite ferrite (CSABF)—a cement produced from industrial side streams—on the hydration and strength development of Portland cement (PC) paste cured at −5 °C with and without pre-curing at room temperature were investigated. The impacts of eco-friendly CSABF cement content and pre-curing on the sett...

The production of ferrite-rich calcium sulfoaluminate belite (CSABF) cement clinker, also containing MgO, from ladle slag, Fe-slag, and phosphogypsum was translated from a lab-scale to a pilot demonstration in a 7-metre kiln at 1260C. An account of the pilot trials/manufacturing is presented, and the process was robust. Laboratory tests prior to sc...

Cementation of radioactive waste arising from nuclear facility operation and decommissioning is a common approach for its encapsulation, solidification, and disposal. Cementation offers significant advantages over other waste conditioning routes, such as thermal conversion of the waste to form ceramics or glasses including simplicity, relatively hi...

Alite–ye’elimite–ferrite (AYF) cement is a more sustainable alternative to Portland cement (PC) that may offer improved mechanical, rheological, and chemical performance. Using traditional raw materials and conventional clinker processing conditions, alite (C3S) and ye’elimite (C4A3$), the major phases in PC and calcium sulfoaluminate (CSA) cements...

The cement industry is carbon-intensive, and the valorisation of industrial side-streams/residuals for use as alternative raw materials can enable the cement industry to reduce its carbon footprint as well as promote resource efficiency. Apart from key clinker ingredients such as CaO, Al2O3, and SiO2, industrial residues can also contain MgO, CaCl2...

Practical routes to immediately valorize the millions of tons of demolition waste/rubble in Syria are established in the title study. Construction and demolition waste are used as a replacement for virgin aggregate in concrete. Properties of fresh and hardened concrete with 0%, 50%, and 100% replacement were investigated. Tests conducted include: d...

The valorisation of cement kiln bypass dust (CBPD) is explored for sustainable production of cementitious clinker phases. CBPD can replace the calcareous component in cement manufacture and allow for a reduction in CO2 emissions as the calcium component in CBPD is mostly decarbonised. CBPD was heated with/out the addition of alumina or silica at te...

The cement industry is partially responsible for the rise of atmospheric CO2 levels and associated global warming. The emissions coming from the calcination of limestone represent the main portion of CO2 from the manufacturing process of Portland Cement (PC). Calcium sulfoaluminate (C$A) and alinite cements have lower CO2 emissions than PC as the f...

It is not straightforward to experimentally measure the standard molar entropy of cement hydrates or clinker minerals. This is further compounded by the controversies surrounding the entropy values reported in established thermodynamic datasets for cements. The purpose of this study is to assess the reliability of standard entropies compiled in tho...

Alkali-activated calcined clay is a type of Alkali-activated materials which are generally activated with caustic chemicals such as NaOH, KOH, or alkali-silicate solutions. These chemicals are expensive and chemically aggressive; but, moderately alkaline Ca(OH)2/Na2CO3 solutions may offer an alternative to overcome the cost and aggressive nature of...

Alinite cement was firstly patented in the USSR in 1970s and their performance is comparable to that of Portland cement. Interest in alinite cement for general use has since waned due to the inclusion of chloride which is known to exacerbate corrosion in reinforced concrete; however, alinite cement may have roles as application-specific cements. Al...

Practical application of magnesium silicate hydrate (M-S-H) cements is hindered due to their relatively slow setting time and low early strength development. Our previous study showed that the formation of the M-S-H binders can be accelerated by the addition of sodium bicarbonate (NaHCO3). To further understand the effect of carbonate additives on...

Magnesium silicate hydrate (M-S-H) cement is an alternative to Portland cement (PC) that can have a lower carbon footprint. M-S-H cements can also have specialist applications such as the stabilization of heavy metals. The development of M-S-H gel is relatively slow, but our recent work has allowed for its accelerated development through the additi...

Blast furnace slag from the steel industry is commercially utilized as a cement replacement material without major processing requirements; however, there are many unutilized steel production slags which differ considerably from the blast furnace slag in chemical and physical properties. In this study, calcium sulfoaluminate belite (CSAB) cement cl...

The varied properties of different cements enable the cement industry to shift towards the manufacture of application-specific cements rather than a general-purpose binder. M-S-H cements could offer a good alternative for specialist application, and could potentially have a lower carbon footprint as they require much lower temperatures for their pr...

Processing of contaminated water in Fukushima Daiichi Power Plant results in various aqueous secondary wastes. A significant strontium (90 Sr) contamination represents one of the key challenges for their management, and we have been developing a new cementing matrix based on calcium aluminate phosphate (CAP) system with reduced water content for su...

Calcium sulfoaluminate belite (CSAB) cement clinkers were produced using two industrial by-products: ladle slag and phosphogypsum. The phase composition of the produced clinkers was identified using quantitative XRD analyses, and the chemical composition of the clinker phases produced from phosphogypsum was established using FESEM-EDS. We demonstra...

Calcium sulfoaluminate (C$A) cement is a binder of increasing interest to the cement industry and is undergoing rapid development. Current formulations do not contain alite; however, alite calcium sulfoaluminate (a-C$A) cements can combine the favourable characteristics of Portland cement (PC) with those of C$A cement while also having a lower carb...

Cement is the most manufactured product on earth. Unfortunately, the manufacture of cement is accompanied by the emission of carbon dioxide gas. Among all manufacturing industry sectors in the UK, the cement industry is the largest CO 2 emitter and these emissions are damaging our planet. The sustainable development of cement will allow future gene...

Producing compounds related to cement in a molten salt flux system offers a reduction in CO2 emissions from the cement industry by allowing target compounds to be produced at lower temperatures than those in their respective conventional manufacturing processes. A thermodynamic study presented here provides the theoretical minimum formation tempera...

Calcium sulfoaluminate clinkers containing ye’elimite (Ca4Al6O12(SO4)) and ternesite (Ca5(SiO4)2SO4) are being widely investigated as components of calcium sulfoaluminate cement clinkers. These may become low energy replacements for Portland cement. Conditional thermodynamic data for ye’elimite and ternesite (enthalpy of formation) have been determ...

Pilot scale trials were successfully performed on the production of novel calcium sulfoaluminate (CSA) cement clinker in a direct natural gas heated rotary kiln at the IBU-tec facility in Germany. A raw meal throughput of ∼25 kg/h was fed to the rotary kiln heated by co-combustion of natural gas and elemental sulfur, with the latter serving as both...

This paper follows on from previously published work where elemental sulfur was used as both a fuel and a source of clinker SO3 to produce calcium sulfoaluminate clinkers. In this work, the process is optimised to produce clinker containing minimal amounts of intrinsic anhydrite and gehlenite. Two pilot kiln trials, designed via thermodynamic model...

The thermal energy required for cement manufacture is primarily utilised within the rotary kiln where clinkerization occurs. To optimise this key stage in cement production, accurate kiln process models are required. In this work, a simple yet powerful one-dimensional kiln model is presented. The thermal aspects of the presented kiln model have pre...

The reduction of process temperature is of interest for cement production as it would reduce not only the energy required but also the corresponding CO2 emissions. Our thermodynamic assessment indicates that cement phases can be produced, in theory, at much lower temperatures, suggesting that the current energy intensive high temperature process is...

A new method for producing calcium sulfoaluminate (CS-A) clinkers is described. Sulfur is introduced from the gas phase as sulfur dioxide and oxygen and reacts with solids during clinkerisation. In this paper, the laboratory experiments are described and thermodynamic calculations are presented. The sulfur-containing phases ye'elimite and ternesite...

Rotary kilns are used extensively in the cement industry to convert raw meal into cement clinker. In order to optimise the operation of cement kilns, computationally efficient thermal models are required. In this work, the development of a one-dimensional thermal model for kilns is explored. To simplify the model, the kiln is assumed to be well mix...

The compatibility of phases within the CaO–SiO2–Al2O3–SO3–Fe2O3 system is revisited. The influence of the SO2 partial pressure on the formation of phases and the stability of phase assemblages is addressed by means of new experimental methods (performed under controlled atmospheres) and thermodynamic calculations. Existing data from the literature...

The compatibility of phases within the CaO-SiO2-Al2O3-SO3-Fe2O3 system is revisited. The influence of the SO2 partial pressure on the formation of phases and the stability of phase assemblages is addressed by means of new experimental methods (performed under controlled atmospheres) and thermodynamic calculations. Existing data from the literature...

The development of novel clinker production processes is typically a slow and incremental process. This work demonstrates that the pace of change can be greatly accelerated using computational tools. The single-stage production of C$A and C$A-Ternesite cements via a novel elemental-sulfur combustion process is examined here. This work collects a th...

A pilot-scale trial was undertaken in a 74 m kiln to demonstrate the production of belite calcium sulfoaluminate cement clinker using sulfur as a raw feed. The sulfur was introduced in its elemental form as fuel to the burner, thus partially offsetting fuel costs while providing sulfur trioxide which is incorporated in the clinker. The study demons...

The useful properties of cement arise from the assemblage of solid phases present within the cement clinker. The phase proportions produced from a given feedstock are often predicted using well-established stoichiometric relations, such as the Bogue equations. These approaches are based on a single estimation of the stable phases produced under sta...

New thermodynamic data for ye’elimite is derived from published vapour pressure measurements and presented in a standard polynomial form for compatibility with existing thermodynamic databases and software. The derived formulas are then used to calculate the stability of ye’elimite under conventional cement kiln operating conditions.

A 1D heat transfer model is described which accurately predicts gas, solid, wall, and outer-shell temperatures simultaneously along the length of a rotary kiln. The novelty of the model presented is its use of a full mass and energy balance for all the species of gas and solid in the kiln, taking into account their temperature-dependent thermodynam...

Cobalt supported on mesoporous silica SBA-15 (0.75, 1.5 and 3 wt% Co) were used as catalysts for the oxidation of carbon black. Catalysts were characterized by N2 sorption, XRD, TEM and TPR. The catalytic activity in CB oxidation was measured. It has been shown that only small cobalt domains (less than 5 nm) are present on all samples. A homogeneou...