Cise Unluer

Cise Unluer
University of Glasgow | UofG

PhD, University of Cambridge

About

95
Publications
27,454
Reads
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2,896
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Introduction
The mission of our team is to contribute to a sustainable built environment through the development of innovative and functional construction products with high performance and durability. Our research involves the use of various experimental and analytical techniques for the advancement of scientific knowledge and applications related to innovations in sustainable concrete materials. In our work, we focus on the use of waste materials, carbon sequestration, recycling, self-healing and 3D printing processes. Within these topics, we are interested in studying the relationship between reaction mechanisms, mechanical performance and microstructural development, as well as the environmental impacts of various binder systems and materials. You can obtain more information about our work by browsing through our website at https://sites.google.com/view/ciseunluer.
Additional affiliations
August 2012 - June 2013
Massachusetts Institute of Technology
Position
  • PostDoc Position
Description
  • Alkali activation of fly ash and examination of the rate controlling step that leads to a better understanding of how to use these materials to produce more sustainable cement mixes.

Publications

Publications (95)
Article
Full-text available
This study proposed the use of hydration agent (HA) and seeds to improve the hydration and carbonation of reactive magnesium cement (RMC)-based concrete formulations. Hydration of RMC was evaluated by isothermal calorimetry. Water absorption and compressive strength results were used to assess the mechanical performance of RMC-based concrete sample...
Article
Full-text available
Reject brine, generated as a waste at the end of the desalination process, presents a useful source for the extraction of valuable resources. This study investigated the recovery of reactive MgO from reject brine obtained from a local desalination plant. This was enabled via the reaction of Mg2 + present within reject brine with an alkali source (N...
Article
This study focuses on the development of a new strain-hardening composite (SHC) involving carbonated reactive MgO cement (RMC) and fly ash (FA) as the main binder. Rheological properties of the developed composites were investigated by varying FA and water contents to achieve desirable fiber dispersion. A suitable mix design, in which polyvinyl alc...
Article
Full-text available
Reactive magnesia-based cement (RMC) is an emerging group of alternative binder to Portland cement. Recently, the first fiber-reinforced RMC-based strain-hardening composites (SHC) have been developed by the authors. The current work investigated the feasibility of the PC-free RMC-based SHC formulations to engage autogenous healing. Results showed...
Article
Due to the harsh environment of Portland cement (PC), bacteria spores are often protected by porous carriers or encapsulated with soft materials before incorporated in PC concrete for self-healing. However, this often leads to strength reduction of concrete and higher cost. This paper investigated the feasibility of direct addition of unprotected b...
Article
The hydration mechanism and strength development of sodium carbonate-activated slag-based systems mainly depend on the additives used. Although the effects of mineral additives in such systems have been extensively investigated, the effects of Mg²⁺, Al³⁺, and Si⁴⁺ ions increasing with the addition of reactive MgO (Mg) and metakaolin (Mk) on the hyd...
Article
Development of alternative binder systems to be used in additive and automated manufacturing technologies is crucial for increasing the sustainability and productivity of the construction process. Advancements in this area facilitate shorter construction durations, enhanced resource efficiency and reduced construction waste; enabling complex, high-...
Article
Inspired by muscle structure, the synergy between basalt fibers (BF) and expansive agent (EA) was revealed and utilized for the development of self-prestressing concrete (SPC). When BF and EA were used together, the restraining action of BF against the autogenous expansion of concrete yielded active confining stress, during which fibers were prestr...
Article
Fly ash (FA)-based geopolymer concrete is considered as an alternative system with potentially lower environmental impact than Portland cement mixes. However, the prediction accuracy of compressive strength still needs to be improved. This study demonstrated the feasibility of predicting the 28-day strength of geopolymer concrete through mix propor...
Chapter
With low calcination temperature of around 750°C–900°C, strength gain via CO2 sequestration, and the ability to be fully recycled, reactive magnesia cement (RMC) is a potential low CO2 binder for construction applications. This chapter presents the recent development of RMC and its applications via nano-modification. Details of research work up to...
Article
This study focuses on the development of carbonated reactive magnesia cement (RMC) concrete formulations involving hydromagnesite (H), magnesite (M) and hydration agent (HA). Partial replacement of RMC by H and M stimulated the formation of hydrate and carbonate phases. Use of H increased the rate and degree of hydration, resulting in the formation...
Article
Chloride ingress is strongly associated with the properties of pores in recycled concrete. To unlock its role in chloride permeability, the pore structures of concrete containing various quantities of recycled coarse (fine) aggregates were analyzed from multi-scales, and the outcomes were further verified by the statistical investigation. The resul...
Article
To achieve the goal of carbon neutrality, carbon capture and storage (CCS) is considered to be an effective approach. This study investigated the microstructural development of reactive magnesia cement-industrial waste (i.e., pulverized fly ash and ground granulated blast-furnace slag) formulations under accelerated carbonation conditions. The dens...
Article
Acid-induced deterioration reduces the service life of concrete and requires high maintenance costs. This study examined the deterioration of graphene oxide (GO)-modified cement pastes exposed to 1 M citric acid (C6H8O7) and 1 M sulfuric acid (H2SO4) environments for two weeks. Changes in the physical and chemical properties of the binder matrix we...
Article
Hydration of reactive magnesia cement (RMC) is limited by the formation of a Mg(OH)2 surface-layer on unreacted MgO particles. This study improved RMC hydration by using magnesium acetate (MA), along with hydromagnesite (H) and magnesite (M) as RMC replacements. While MA accelerated hydration and resulted in the formation of needle-like artinite, i...
Article
The mechanical and thermal properties of a novel 3D-printed macro-encapsulation method for Phase Change Materials (PCMs) was investigated and compared to mixtures that contain commercially available micro-encapsulated PCMs. Two types of cement-based mixtures, a mortar mix with a density of 2,161 kg/m³ and a lightweight mix with a density of 1,351 k...
Article
In this study, the rheo-viscoelastic behaviors of calcium sulphoaluminate (CSA) modified Portland cement (PC) pastes were investigated. The shear stress, apparent viscosity, frequency sweep and time sweep curves of composite pastes with different PC and CSA volume fractions were analyzed, and the minimum apparent viscosity (ηmin) of PC-CSA pastes w...
Article
The calculation of the rheological parameters of fresh cement pastes plays a key role in understanding the rheology of cement‐based mixes. Because cement paste is not a simple Bingham fluid, a suitable nonlinear model must be found for characterizing its flow. A test system in which the rotational speed or shear rate can be changed in multiple step...
Article
The low hydration and carbonation of reactive MgO cement (RMC) under ambient conditions causes prolonged setting and low compressive strengths (~4 MPa). This study proposed a unique technique which led to the enhancement of the hydration and carbonation processes via the synergistic combination of microbial carbonation process (MCP) with a hydratio...
Article
The effect of chloride attack on carbonated reactive MgO cement (RMC) samples containing fly ash (FA) and ground granulated blast-furnace slag (GGBS) under cyclic wetting and drying was studied. Porosity, sorptivity and chloride profile observations were carried out in parallel to the XRD, TGA and SEM analyses performed before and after exposure. I...
Article
Full-text available
This paper presents a new microbial technique for soil improvement through microbially induced carbonate precipitation (MICP) incorporating with reactive magnesia cement (RMC). Through a microbially induced carbonate precipitation (MICP) process, hydrated magnesium carbonates (HMCs) are produced due to biological carbonation of hydrated RMC, which...
Article
Magnesium-silicate-hydrate (M-S-H) cement has emerged as an alternative binder with potentially lower energy requirements and emissions. Due to the intrinsically low pH values of its matrix, however, normal steel reinforcement is not appropriate for M-S-H system. To toughen the matrix and to overcome the brittle nature of the material, a new strain...
Article
This study focused on the development of 3D printed building components incorporating MgO–SiO2 binders. The effects of parameters such as MgO/SiO2 and water/binder ratios and superplasticizer dosage were evaluated to produce 3D printable MgO–SiO2 binders. The assessment of rheological and mechanical properties, which led to an optimum mix that sati...
Article
Hydrated lime (Ca(OH)2)- and reactive magnesia (MgO)-activated ground granulated blast-furnace slag (GGBS) have shown advantages in geotechnical applications compared with Portland cement (PC). To apply these two novel binders in slurry form to field applications, the properties of their grouts need to be investigated, which is the objective of thi...
Article
This study investigated the mechanical and microstructural changes in reactive MgO cement-based concrete cured under ambient and accelerated carbonation conditions, followed by exposure to high temperatures. The compressive strength of ambient-cured samples increased from 10 to 30 MPa when subjected to up to 200 °C, which was achieved via increased...
Article
With lower calcination temperature, reactive magnesia cement (RMC) can be a potential alternative to the Portland cement. However, RMC concrete requires accelerated carbonation curing from external sources which greatly hinder the wider applications of RMC. This study proposed a bacteria-based method for the strength gain of RMC through internal ca...
Article
This paper investigated the influence of different CO2 concentrations on the microstructural and mechanical development of reactive MgO cement (RMC) concrete. Combination of various analyses revealed the enhancement of hydrated magnesium carbonate (HMC) phases with relatively superior micro-mechanical properties as the CO2 concentration increased f...
Article
When exposed to carbonation, Na2CO3-activated slag (SCAS) concrete demonstrated 53% mass loss and 57% reduction in compressive strength due to the decalcification of C-(A)-S-H. Improvements in the carbonation resistance of SCAS mixes via the inclusion of hydromagnesite seeds (S) and reactive MgO (M) were reported in this study. The conversion of Mg...
Article
This study investigated the hydration, rheology, and diffusion resistance of cement pastes involving up to 0.09 wt% graphene oxide (GO) under constant exposure to hydrochloric (HCl) acid for four weeks. Samples containing 0.09 wt% GO revealed a reduction in mass loss and sectional area loss when compared to the control sample without any GO, highli...
Article
This study focused on the development of reactive MgO (RM) activated-GGBS binders containing fly ash (FA). Performance of these binders was aimed to be improved by enhancing the hydration of RM and dissolution of GGBS and FA via high temperature pre-curing (HTPC); and conversion of unreacted phases into carbonates via carbonation. Spherical FA part...
Article
This study investigated the feasibility of producing reactive MgO cement from reject brine obtained from a desalination plant and evaluated its use as a binder in comparison to a commercial MgO. The mechanical performance of the samples cured under carbonation conditions for up to 28 days were further supported by x-ray diffraction (XRD), thermogra...
Article
This study investigated the healing efficiency and phase formations in pre-cracked reactive magnesiabased binders under CO2/water conditioning. Pre-loaded samples with various crack widths were subjected to a healing regime involving 10% CO2 and water for 10 cycles. The recovery of samples wasassessed by resonance frequency measurements and optical...
Article
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Article
Full-text available
Ground granulated blast-furnace slag (GGBS), activated with olivine (Mg2SiO4) and sodium hydroxide (NaOH), was used to stabilise a clayey soil. Mechanical and microstructural properties of the stabilised soil were assessed through uniaxial compression strength (UCS) tests, X-ray diffraction, scanning electron microscopy and energy-dispersive X-ray...
Article
Use of hydromagnesite as seeds in alkali-activated slag (AAS) blends was studied. Introduction of 2% seeds (by mass) accelerated the hydration kinetics of AAS blends. Seeding led to shorter setting times, higher strengths and denser microstructures. Improvements in performance were in line with increases in hydrate phase formation. Provision of add...
Article
This study investigated the strength and microstructural development of MgO and MgO-microsilica (MS) systems under sealed and carbonated conditions. The influence of hydromagnesite seeds on the performance of each system was also evaluated. The hydration mechanisms were studied via isothermal calorimetry. A correlation between the strength developm...
Article
This study investigated the properties of alkali activated slag (AAS) binders formulated for extrusion-based 3D printing. The fresh properties of AAS mixes were tailored through the use of nanoclay (NC) and nucleation seeds. The printability criteria employed were the ease of extrusion (extrudability) and the stability of the layered structure (bui...
Article
Full-text available
This study is the first in the literature to systematically assess the environmental impacts of magnesium oxychloride cement (MOC) samples, which are regarded as a more eco-friendly construction material than Portland cement. The environmental impacts of MOC samples prepared with various molar ratios of MgO/MgCl 2 ·6H2O and sources of reactive magn...
Article
This study aimed to accelerate the reaction kinetics and improve the performance of Na2CO3-activated ground granulated blast-furnace slag (GGBS) via the use of reactive MgO and hydromagnesite seeds. The effect of 3–10% MgO and 0.5–1% seeds on the reaction mechanisms of Na2CO3-activated pastes was evaluated by pH, isothermal calorimetry and setting...
Article
MgO cement (RMC)-based mixes are known to gain strength via carbonation. While the strength gain mechanism of RMC mixes has been studied, their durability under aggressive environments is relatively unknown. This study investigated the changes in the performance and microstructure of two concrete formulations, whose binder component was made up of...
Article
This study investigated the performance of carbonated reactive MgO cement (RMC) and sealed MgO-SiO2 (RMS) concrete formulations. Fly ash (FA) and ground granulated blast-furnace slag (GGBS) replaced half of the binder component in each system. The assessment of hydration mechanisms via isothermal calorimetry was supported by performance evaluation...
Article
Recently, the mineral carbonation via the reaction of CO2 with saline aquafers received much attention as one of the most promising ways for geologic CO2 storage. This paper reports microstructure and carbon storage capacity of hydrated magnesium carbonates (HMCs) synthesized from different sources, i.e., reject brine and commercial Mg(OH)2 slurry,...
Article
This study investigated the formation of different phases and their influence on the microstructural and mechanical development of carbonated reactive MgO cement formulations. Hydrated magnesium carbonates (HMCs) were identified and quantified via XRD, TG-DTG and SEM. Visual observations of the 3D internal structure at different depths were perform...
Article
This study focused on the suitability of geopolymer mixes for extrusion-based additive manufacturing applications. Geopolymer mixes including alkaline potassium silicate activator with different molar ratios were prepared and evaluated for their rheological responses (e.g. yield stress, viscosity and thixotropy) that influenced their extrudability...
Article
The strength gain of reactive MgO cement (RMC) samples depends on carbonation, which is limited by the formation of an initial carbonate layer and the low dissolution of CO 2 . This study investigates the use of seeds and NaHCO 3 (SBC) to extend the surface area for carbonation and increase CO 2 dissolution, respectively. The influence of seeds and...
Article
Full-text available
Interest in innovative construction processes such as 3D concrete printing (i.e. digital construction), is growing rapidly both in academia and industry. Processing conventional geopolymer mixes, in which alkaline solutions are used for activation, could be troublesome in concrete printing due to the high viscosity of the alkaline solution. One-par...
Article
This study investigated the changes in the performance and microstructure of carbonated MgO samples subjected to 40°C-550°C in water, oven, and furnace conditions. Although sample strength remained relatively stable until 80°C, an obvious reduction was observed in higher temperatures. This performance decline was attributed to the changes in the co...
Article
This study investigated the durability of carbonated reactive MgO cement (RMC) concrete containing fly ash (FA) and ground granulated blast-furnace slag (GGBS) under conditions involving exposure to sodium chloride, sodium sulfate, freeze-thaw cycling and seawater for up to 6 months. RMC samples were compared in terms of their performance to Portla...
Article
The performance of reactive MgO cement (RMC)-based concrete formulations is determined by the carbonation process, which is hindered by the inadequate CO2 dissolution in the pore solution. This study addresses the improvement of carbonation and associated performance of carbonated RMC-based concrete samples via the introduction of sodium bicarbonat...
Article
Rice husk ash (RHA) is a waste material obtained from the combustion of rice hulls. The properties of RHA, such as its crystallinity and reactivity, depend on the combustion conditions. This study investigated the use of RHA as a silica source in MgO–SiO2 samples. Two different RHA sources (crystalline and amorphous) were used in comparison to micr...
Article
Full-text available
The effect of nano-attapulgite clay (NC) addition on the fresh, hardened and microstructural properties of high volume fly ash (HVFA) mixes designed for 3D printing was investigated in this study. Experimental results showed that the addition of 0.1–0.5% (i.e. by mass of binder) NC increased the static yield stress of HVFA mortars without significa...
Article
Full-text available
This study presents the development of fly ash-based geopolymer mixtures for 3D concrete printing. The influence of up to 10% ground granulated blast-furnace slag (GGBS) and silica fume (SF) inclusion within geopolymer blends cured under ambient conditions was investigated in terms of fresh and hardened properties. Evolution of yield stress and thi...
Article
This study investigated the changes in the performance and microstructure of MgO-SiO2 concrete under exposure to different environments involving carbonation, NaCl, MgCl2 and MgSO4 solutions for up to 180 days. Compressive strength results were compared to Portland cement (PC)-based concrete samples subjected to the same environments. Microstructur...
Conference Paper
This study presents the first steps of a novel synergy between simulations and experiments, linking multiple scales of the geopolymerisation process. The thermodynamic and kinetic quantities specific to the dissolution reaction of metakaolin (i.e. the activation energy, equilibrium constants and water-cement interfacial energy) were computed. The n...
Conference Paper
Strength and stability at high temperature are essential properties for cementitious materials in the energy sector. As a more sustainable alternative to ordinary portland cement, the potential of geopolymer cements, made by alkaline activation of fly ash or metakaolin, has been acknowledged. However, it is still poorly understood how the chemistry...
Article
This study compared two binder systems composed of reactive magnesite cement (RMC) and calcined dolomite (D800), which were produced via the calcination of magnesite and dolomite at 800°C, respectively. The environmental impacts of the production of both binders were supported with an investigation of their strengths and microstructural development...
Article
In addition to its use in various applications such as those in the agriculture, pharmaceutical and refractory industries, MgO is being investigated as a cement binder due to the low calcination temperatures used during its production and its ability to gain strength by absorbing CO2 in construction products. Similar to the dry-route, the reactivit...
Article
Carbonation governs the microstructure and the overall mechanical performance of mixes involving MgO cements as the main binder. Aggregate grading has a significant influence on the carbonation process due to the different particle arrangements that determine the porosity and permeability of the resulting formulations. This work investigates the ef...
Article
This study investigates the performance and microstructural development of reactive MgO and calcined dolomite-based concrete samples subjected to carbonation curing for up to 28 days. The performance of each sample is assessed via compressive strength testing, which is linked with the hydration and carbonation mechanisms studied via isothermal calo...
Article
This study investigated the recycling potential of carbonated reactive MgO cement (RMC)-based concrete systems. Calcination conditions controlled the performance of recycled samples, which were fully decomposed at 700 °C. Recycled samples demonstrated 15–20% lower strengths than original samples, attributed to changes in MgO reactivity, aggregate p...
Article
This study investigated the strength and microstructural development of reactive MgO-SiO2 binder systems under different curing conditions. Rapid strength development associated with accelerated dissolution and hydration involving magnesium silicate hydrate (M-S-H) formation was observed at early ages under elevated temperatures (60°C). Although sa...
Article
The continuation of the hydration and carbonation reactions within reactive MgO cement formulations is inhibited by the formation of hydrate and carbonate phases around MgO particles, resulting in a low MgO utility and limited mechanical performance. This study introduces carbonate seeds into the pore space of MgO-based concrete mixes to enable the...
Article
This study assesses the influence of mix design on the hydration and carbonation of reactive MgO cement (RMC)-based concrete formulations by varying the water and cement contents. Samples were subjected to accelerated carbonation under 10% CO2 for up to 28 days and compared with corresponding PC-based samples. Their performance was analyzed by comp...
Article
Strength development of reactive MgO cement-based concrete is limited by the low hydration and carbonation of MgO. This study aims to improve the hydration and mechanical performance of carbonated MgO mixes with the introduction of various hydration agents (HAs) at different concentrations. Influence of these HAs on the hydration and carbonation me...
Article
The use of magnesium oxide (MgO) as the key reactive component within hydraulic binder systems has been reported in many studies. This study investigated the strength and microstructural development of MgO and MgO-SiO2 binder systems under different curing conditions. Concrete samples, whose binder component consisted of only MgO or MgO-SiO2 were s...
Article
Carbonation plays a key role in the strength gain of reactive MgO cement (RMC)-based concrete formulations. Low hydration of MgO limits the subsequent carbonation and associated strength gain. This study improves the mechanical performance of carbonated RMC concrete mixes with the introduction of a hydration agent (HA) and high temperature pre-curi...
Article
This paper investigated the performance and environmental impacts of reactive magnesia cement (RMC)-based formulations containing pulverized fuel ash (PFA) and ground granulated blast furnace slag (GGBS). Concrete samples, whose binder component was composed of RMC with 0–50% PFA and GGBS replacement were subjected to carbonation curing for up to 2...
Article
Full-text available
Reactive magnesia (MgO) with a high purity and reactivity is used in several high-end applications. This study reports the feasibility of synthesizing high reactivity MgO from reject brine with the use of NH4OH. The molar amount of NH4OH was optimized at a NH4OH/Mg2+ molar ratio of 6 to provide maximum magnesium oxide yield and purity. This led to...
Article
This study investigated the influence of air-entraining agents (AEA) on the performance and microstructure of reactive MgO cement (RMC) samples in comparison with Portland cement (PC) samples under different water contents and curing conditions. Porosity, density, workability, strength, pH and thermal conductivity measurements were supported with X...
Article
This paper reports for the first time the stabilization of soil using olivine and the application of novel techniques utilizing alkaline activation and carbonation. A rigorous study addressed the effect of carbon dioxide pressure and alkali concentration (10-M sodium hydroxide soil additions from 5 to 20%) between 7 and 90 days. Microstructural and...
Article
Full-text available
MgO cements have great potential for carbon sequestration as they have the ability to carbonate and gain strength over time. The hydration of reactive MgO occurs at a similar rate as ordinary Portland cement (PC) and forms brucite (Mg(OH)2, magnesium hydroxide), which reacts with CO2 to form a range of hydrated magnesium carbonates (HMCs). However,...
Article
Indoor carbon dioxide (CO2) levels serve as an indicator of ventilation sufficiency in relation to metabolic effluents. Recent evidence suggests that elevated CO2 exposure (with or without other bioeffluents) may cause adverse cognitive effects. In shelter-in-place (SIP) facilities, indoor CO2 levels may become particularly elevated. This study eva...
Article
This paper investigates the carbonation potential, strength gain and microstructural development of magnesium oxide (MgO) blocks and provides a comparison with Portland cement (PC) blocks. Performance was evaluated in terms of density, porosity, compressive strength and microstructure at different depths along sample cross-sections. Scanning electr...
Article
Reactive magnesia (MgO) cements are proposed as a potentially sustainable binder due to their lower production temperatures (~800 vs. 1450°C) than Portland cement (PC) and ability to fully carbonate and gain strength during setting. Reactive MgO is mainly produced via the calcination of magnesite. Environmental implications of reactive MgO producti...
Article
This paper is a reply to the discussion by S.A. Walling and J.L. Provis on our papers "Impact of hydrated magnesium carbonate additives on the carbonation of reactive MgO cements" and "Enhancing the carbonation of MgO cement porous blocks through improved curing conditions". Walling and Provis discuss the assignment of X-ray diffraction patterns, t...
Article
This study focuses on the enhancement of the technical and environmental performance of MgO cements through the inclusion of brucite, GGBS, talc and serpentine as partial MgO substitutes in concrete blocks. The influence of these additives on the microstructure, hydration, carbonation, and mechanical performance of blocks cured under natural and el...
Conference Paper
Full-text available
Portland cement (PC), the most widely used construction material in the world, is currently produced at a rate of 3 Bt/year, and is responsible for 5-7% of anthropogenic CO2 emissions. This production rate is expected to double by the middle of the century, placing global pressures on the cement industry to reduce its emissions. Reactive magnesia (...