Franco Zunino

University of California, Berkeley | UCB · Department of Civil and Environmental Engineering

In some blended cements, the optimum amount of sulfate addition differs from that observed in OPC. This study aims to understand the mechanism behind the impact of two SCMs, namely metakaolin and limestone, on the sulfate balance of blended cements. No significant impact of the aluminum content of these SCMs was observed. Instead, it is observed th...

LC³ is one of the most promising alternatives for a high-performance blended cement with a significantly lower clinker content and with potential for worldwide adoption. For this reason, understanding its long-term performance is relevant to ensure serviceability over its lifespan. In this paper, a detailed study of phase assemblage, porosity evolu...

Using calcined clays as supplementary cementitious materials is one of the main solutions available for a substantial and widespread reduction of the clinker factor in cement. Thus, understanding the phenomena governing their production process and reactivity is crucial for a successful technological deployment. In this study, the mineralogical and...

Limestone calcined clay cement (LC3) is a promising material for producing cement with low CO2 emissions and properties similar to, or superior to, those of Portland cement (PC), but at 50 % clinker content (LC3-50). In many applications, lower strengths than PC are acceptable, opening new opportunities to develop suitable LC3 formulations with cli...

In limestone calcined clay cements (LC3), more hemicarboaluminate and monocarboaluminate is observed, as compared to other blended cements, from the reaction of metakaolin with limestone. In this study, it is shown that the formation of these carboaluminate phases, predominantly occurs during a “third” hydration peak, after the main alite and alumi...

This study investigates the mechanisms behind fluidity loss in superplasticized limestone calcined clay cement (LC3), a sustainable alternative to ordinary Portland cement (OPC). Despite its environmental benefits, in presence of superplasticizers, LC3 experiences significant challenges in maintaining workability, an issue of which this paper exami...

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...

In this review by TC- 282 CCL, a comprehensive examination of various facets of chloride ingress in calcined clay-based concrete in aggressive chloride-rich environments is presented due to its significance in making reinforced concrete structures susceptible to chloride-induced corrosion damages. The review presents a summary of available literatu...

This paper presents a preliminary study of the characterization of the surface energy properties of clinker phases (C3S and C3A), kaolin and metakaolin by Inverse Gas Chromatography (IGC). For this, a reliable measurement methodology was developed. By looking at changes in the whole series of results (dispersive surface energy, specific polar inter...

It has long been known that alkalis favor an increase in the early strength of cementitious materials but have a negative impact on long-term strengths. The reasons for the negative effect on later strengths are not clear. In this paper we investigated the influence of alkali addition on the properties of a white cement and for the first time propo...

Concrete is by a substantial margin the most widely used construction material. Projections indicate that the demand for concrete it will continue to increase to sustain the development of emerging economies. This paper presents a new perspective of low-carbon concrete by refocusing on the actual final product, highlighting the tremendous CO2 savin...

Materials used in concrete construction are highly regulated through national standards that set minimum material reactivity, composition, and performance. Advances have shown that the combination of calcined clay and limestone fines in cementitious systems can have a synergistic reaction that allows for high levels of clinker replacement while mai...

Tomorrow's mineral binders are called on to integrate a growing proportion of mineral powders other than Portland clinker. This impacts most properties of industrial interest including fresh state properties, the focus of this paper. We discuss the physical, physico-chemical and chemical changes that such an evolution in mix design is expected to i...

The adoption of blended cements is the most feasible short-to-mid term strategy to achieve a more sustainable cement and concrete industry. In this regard, reducing the clinker factor, while retaining performance, is the key parameter to address. Limestone calcined clays are a promising technology as they offer similar performance to PC from 7 days...

Concrete is the substance used in largest quantity by mass after water, with an anticipated demand that will continue to increase in decades to come. The ultra-green concrete project aims at developing a new family of concretes to radically reduce the CO2 emissions related to this material, substantially beyond the CO2 savings of any of the technol...

Limestone and calcined kaolinitic clays are unique among supplementary cementitious materials due to their high and widespread availability. Furthermore, their combined reactivity enables substitutions of clinker of 50% (or more), while reaching comparable strength to PC (or pozzolanic cements) and enhanced durability properties. During the last 4...

Limestone calcined clays are a promising technology as they offer similar performance to OPC from 7 days onwards, while enabling a reduction of the clinker content of 50%. In some regions of the world like South America, pozzolanic cements (i.e., blended cements that combine clinker with natural pozzolans) have been used for decades as an effective...

In this study, a protocol for synthesising β-C 2 S using K 2 SO 4 as a dopant has been reported. Quantitative X-Ray diffraction was used to characterise synthesised samples. It was observed that it is possible to synthesise β-C 2 S with high purity (>96 wt%) and limit the formation of free lime to below 0.5 wt% using this protocol. Unreactive γ-C 2...

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...

Understanding the mechanism controlling the sulfate requirement of blended cements is crucial for a successful deployment of these technologies towards a more sustainable industry. Particularly, clarification regarding the role of alumina content on the sulfate requirement is essential to establish suitable procedures to achieve proper sulfation in...

A comprehensive understanding of hydration kinetics, sulfate requirement and phase assemblage of Portland cement is crucial for further optimization of early-age performance, especially when part of cement is replaced by mineral additions in blended cements. Gypsum is added to PC to control the reaction of the aluminate phase. The addition of gypsu...

The inclusion of high specific surface materials such as calcined clays in cementitious systems enhances the hydration of clinker products at very early ages, but it may also increase water demand; thus, the pursuit of a flowing concrete may demand an increase in the dosage of superplasticizers. The grinding regime can have a major influence on the...

This paper presents selected outputs from the Re-purposed Excavated Arising Loops (REAL) research project, aiming to transform London Clay obtained from excavation operations into construction materials, to enhance circularity in construction and minimize waste disposal. As part of this research, London Clay was calcined using a rotary kiln, for it...

Beta-dicalcium silicate (β-C2S), one of the main phases in Portland cement clinker, offers some promising overviews regarding CO2 and energy savings potential compared to alite. Understanding the crystalline structure and reactive sites on β-C2S surface is critical to enable further optimization of its use. There is a lack of such studies available...

Reducing the carbon footprint of the concrete industry is a priority in the face of global warming. Limestone calcined clay cements (LC 3) provide one of the best options to reduce CO 2 emissions. For optimal implementation, but also to facilitate other low CO 2 solutions, standards that regulate the cement and concrete sector need be adapted quick...

Synopsis: The optimization of the production process and mixture design using blended cements is an important step to achieve a widespread adoption of these new technologies. In particular, grinding is an important step to ensure good reactivity at early ages and adequate flowability. Grinding aids are normally used to reduce the electrostatic forc...

Synopsis: The adoption of blended cements is the most feasible strategy to achieve a more sustainable industry. In this regard, reducing the clinker factor, while retaining performance, is the key parameter to address. Limestone calcined clays are a promising technology as they offer similar performance to OPC from 7 days onwards, while enabling a...

London Clay is a marine geological formation which is relatively abundant in the London Basin area in the United Kingdom with a mineralogy consisting of kaolinite, illite, chlorite, smectite and montmorillonite. London Clay can be highly variable and is generally regarded as a common clay with kaolinite contents ranging between 10 and 30% [1]. As p...

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...

The durability performance of blended cementitious systems with calcined clays is reviewed in this paper by the RILEM TC 282-CCL on calcined clays as supplementary cementititous materials (SCMs) (working group on durability). The impact of metakaolin and other calcined clays on the porosity and pore structure of cementitious systems is discussed, f...

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...

Hemicarbonate is observed in hydrated cement paste even after prolonged hydration and in the presence of calcium carbonate, although monocarbonate is expected to be thermodynamically more stable. In this study, we demonstrate that hemicarbonate is significantly stabilized by the incorporation of foreign anions in its structure, resulting in the for...

Valorisation of locally available clays for producing blended cements is crucial for a widespread adoption of sustainable binders incorporating these materials. In some places, clays can be intermixed with small amounts of iron sulfides, which could eventually expand in the alkaline media of concrete and lead to cracking if clay particles are suffi...

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...

The climate emergency requires the adoption of strategies and technologies that effectively reduce CO 2 emissions in the short to midterm to keep the global temperature rise below 2°C above pre-industrial levels. Concrete is the substance most consumed by humanity after water. The blended cements in which supplementary cementitious materials replac...

It has been well stablished by several studies that LC3 requires an additional amount of gypsum on top of the normal dosage contained in OPC. In this manner, the second (aluminate) peak do not overlap with the first (alite) peak. This required increase of the sulfate content is attributed to the additional aluminate phases introduced to the system...

A correction to this paper has been published: https://doi.org/10.1617/s11527-021-01654-5

Grinding aids are commonly used in cement manufacture to reduce electrostatic forces between powder particles and reduce agglomeration. Alkanolamines are known to also influence the hydration of the aluminate phases in cement. This study assessed the effect of TEA, TIPA and DEIPA addition on the hydration of LC3 systems. It was observed that these...

Understanding the sulfate balance mechanism of cement is needed for an effective use of sustainable blended cements. Pure phase systems allow to study the interaction between sulfate and each of the phases involved in early age hydration separately. This paper explores the effect of different factors on sulfate requirement in C3S/C3A systems. It wa...

The combined use of calcined clays and limestone in the ternary system LC3 enables up to 50% of clinker substitution without affecting the performance. Low grade calcined clays are rich in iron. If calcined in an oxygen rich atmosphere, they turn to red. Cement producers avoid selling cement with a color different to the traditional. This paper pro...

Limestone calcined clay cements (LC3) are blended cements that combine clinker, limestone, calcined clay and gypsum. The availability of the materials required to produce LC3 and the good performance that it achieves, makes LC3 suitable as a sustainable replacement of Portland cement. Significant advances have been made to assess the properties of...

The use of supplementary cementitious materials as a partial replacement for Portland cement is the most effective way to reduce the carbon footprint of the concrete industry. Raw clays containing kaolinite (kaolin) are promising substitute materials. In the field, raw clays are often mixed with calcite and this is thought to affect their behaviour...

The adoption of blended cements to reduce the carbon footprint has increased significantly over the last decades. Clays containing kaolinite are a promising choice due to their widespread availability. Kaolinite content is the major factor controlling the performance of blended cements incorporating calcined clay, for example in LC 3-50 (50% clinke...

Calcined clays provide a promising opportunity to lower clinker levels in cements because of their widespread availability and their excellent reactivity in blended cements. On the other hand, one of the main drawbacks of calcined clay utilization for blended cement manufacture is the negative impact on workability. This project explores the use of...

Calcite impurities in clay form a granular deposit on the surface of kaolinite which reduces surface area and slightly impact reactivity. However, the effect is minor and therefore, calcite contaminated clays can be used as SCMs if the content of impurities is in the range explored in this study. The formation of a Ca-bearing glass phase was observ...

A mechanism linking C-S-H precipitations and gypsum depletion Our results show that the ratio of aluminate and gypsum phases cannot explain the kinetics of reaction observed. On the contrary, the overwhelming driving mechanism is linked to the specific surface area that the mineral additions. This additional surface provides nucleation sites for C-...

This paper details the main factors influencing the performance of limestone calcined clay cements (LC ³ ). The kaolinite content plays a major role in the rheological properties as well as strength development. Even in the presence of secondary phases, kaolinite can be accurately quantified by thermogravimetric analysis. The performance of LC ³ is...

This project explores the influence of different particle size distributions of limestone on the workability and early-age strength development of LC3 materials. To quantify, and subsequently optimize, the packing, the modified Andreasen and Andersen model was used. Different systems were selected and studied using minicone tests and compressive st...

Limestone calcined-clay cements (LC3) take advantage of the synergetic effects of calcium carbonate reaction with the additional aluminium provided by the calcined clay. As temperature decreases, calcium carbonate solubility increase, therefore, the early-age hydration kinetics and the optimal proportioning of the ternary cement system are modified...

This study focused on understanding the influence of different amounts of calcite impurities (0 to 10% by mass) on the optimal parameters for clay dehydroxylation and the reactivity of the final calcined clay. A surface response experimental design was used to study the effect of maximum temperature, residence time and calcite content on different...

In-situ XRD experiments allowed to study the hydration of LC 3 binders in detail during the first 48 hours. The differences observed between OPC (aluminates from calcined clay and OPC) and C 3 S (aluminates only from calcined clay) phase assemblage allowed to attribute the observed third peak of hydration as the reaction of limestone and aluminates...

Reducing the carbon footprint of the cement industry has become one of the main concerns of researchers in the field. This study explores different strategies to reduce the setting retardation effect of high-SO3 fly ash (HSFA) on cement paste. The SO3 phase was found to correspond to hannebachite (CaSO3·0.5H2O). Chemical (calcium chloride), physica...

Strategies to increase early-age strength Calcined kaolinite content is linked with compressive strength of LC 3 systems. However, other design parameters such as limestone fineness can be adjusted to increase performance in scenarios where only low-grade clays are available. The use of fine limestone in combination with a fraction of coarse partic...

Ground calcined clays exhibit a typical bi-modal particle size distribution, which is observed in clays ground in a variety of conditions. Kaolinite, the most reactive mineral present in clays, is concentrated in the finer population of the PSD due to is higher grindability as compared to quartz and other impurities. Therefore, there is an opportun...

Further increasing early-age strength by alkali adjustment Calcined kaolinite content is linked with compressive strength of LC 3 systems. However, other design parameters such as limestone fineness can be adjusted to improve performance in cases where only low-grade clays are available. The inclusion of fine limestone in LC 3-50 mixtures proved to...

Fly ash is frequently used as a replacement for cement in concrete. However, questions remain regarding the influence that fly ash has on the hydration of cement. This paper examines physical aspects (e.g., surface nucleation, cement particle spacing) and chemical aspects (e.g., pozzolanic and hydraulic reactions) of the fly ash and cement in mixtu...

Hardened cement paste in concrete wastes can be a valuable precursor material for the production of recycled cements. In the reported study, X-ray diffraction data of cementitious materials obtained by thermal processing of hardened pastes were quantitatively analyzed using Rietveld refinement to explain the effect of process parameters on their hy...

Limestone calcined-clay cements (LC 3) take advantage of the synergetic effects of calcium carbonate reaction with the additional alumina provided by the calcined clay. As temperature decreases, calcium carbonate solubility increases, therefore, the early-age hydration kinetics are modified. This study explored the reactivity and mechanical perform...

Among supplementary cementitious materials (SCMs), rice husk ash (RHA) is a by-product of the agricultural industry that is recognized by its high reactivity and ability to enhance performance of cement-based materials. The dependence of RHA reactivity on burning conditions and grinding procedures makes it sensitive to uncontrolled combustion/produ...

With the ongoing sustainability movement, the incorporation of limestone powder in cementitious binders for concrete in the U.S. has become a subject of renewed interest. In addition to accelerating the early age hydration reactions of cementitious systems by providing additional surfaces for nucleation and growth of products, limestone powder is a...

Developing functional concrete mixtures with less ordinary portland cement (OPC) has been one of the key objectives of the 21 st century sustainability movement. While the supplies of many alternatives to OPC (such as fly ash or slag) may be limited, those of limestone and silica powders produced by crushing rocks seem virtually endless. The presen...

Cold weather concreting often requires the use of chemical accelerators to speed up the hydration reactions of the cement, so that setting and early-age strength development will occur in a timely manner. While calcium chloride (dihydrate – CaCl2∙2H2O) is the most commonly used chemical accelerator, recent research using fine limestone powders has...

Tetra-ethyl-ortho-silicate (TEOS) consolidation is a promising technique; however, the effects of substrate microstructure and mineralogy on the TEOS performance have not been systematically assessed; which is critical to improve consolidation efficiency. Clay bricks were manufactured in a variety of clay/kaolin proportions, calcination temperature...

High strength lightweight concrete (HSLC) has been studied extensively in the laboratory and used in projects over the last decade. Its lightweight and high strength characteristics are advantageous, but HSLC also presents several challenges. Few studies have focused on the issues associated with the field implementation of HSLC. These issues are e...