This study investigates the effects of carbonation curing and ye'elimite on the physical and chemical properties of ternesite to improve its hardening rate. The results showed that ternesite had a high carbonation activity and the additional benefit of CO2 sequestration. The carbonation products included amorphous calcium carbonate, calcite, aragonite, gypsum, and either C-S-H gel or silica gel. The

Crystallographic defects play a crucial role in cement hydration, with initial dissolution being dominated by the formation of etch pits that rely on the intersection of defects on surfaces. However, the defects present in cement particles have remained a mystery due to the lack of detailed direct observation at the atomic scale. In this study, we used scanning transmission electron microscopy to unravel

C-S-H seeds are highly-efficient in promoting hydration but not compromising the long-term performances of cement. Unfortunately, mechanisms of the C-S-H seeds properties affecting the early-age performances of cement are not very well understood. In this study, the influence of hydrothermal synthetic conditions on the C-S-H seeds properties is firstly investigated, followed by revealing the correlations

Abstract not available

Cementitious materials exposed to marine and saline environments are commonly threatened by a combined attack of sulfate and chloride ions. This study developed a numerical framework to investigate two combined coupling mechanisms of 1) coupled solid-liquid chemical reactions for competitive chloride-sulfate attack and 2) electrostatic multi-ion coupling effect on reactive-transport mechanisms. Various

This study aimed to improve the carbonation efficiency and reduce processing time of recycled concrete aggregates (RCAs). Different liquid mediums were used for wet carbonation and compared with dry carbonation. Reaction kinetics, phase assemblage, microstructure and performance of RCAs and recycled aggregate concrete (RAC) prepared with carbonated RCAs were evaluated. RCAs carbonated under seawater

Decalcification of calcium silicate hydrates (C-S-H) is one of the most important issues for cement-based infrastructures concerning long-term safety performance. While enhanced decalcification of C-S-H in saline solution has been extensively characterized by experimental studies, the underlying microscale mechanisms are not well understood. Using molecular simulations with the metadynamics method

Mixing Portland cement (PC) and calcium sulfoaluminate (CSA) cement can provide several advantages for specific applications. However, the stability of ettringite has a significant impact on ettringite-rich cements properties. This study aims to investigate the impact of calcium nitrate (Ca(NO3)2 = CN) and calcium carbonate (CaCO3 = CC) on the performance evolution and stabilization mechanism of PC-CSA-C$

This study evaluates the effect of ten organic additives belonging to the classes of carbohydrates and sulfonates on the microstructure of portlandite crystals during CaO hydration. Calcium hydroxide modified with selected additives was prepared and characterised in terms of crystal size and habit, platelets abundance, crystallinity, specific surface area, particle size distribution, calcium concentration

The effect of substituting a large amount of silica fume (SF) with nanosilica (NS) on the hydration behavior and mechanical properties of Ultra-High-Performance Concrete (UHPC) was investigated. Derivative thermogravimetric analysis showed that NS had the highest reactivity among the ingredients used in the UHPC mix. As the NS substitution rate increased, the time corresponding to the maximum exothermic

Low-temperature low-field nuclear magnetic resonance was applied to analyze the icing amount in water saturated white cement paste specimens at different temperatures during the freeze–thaw process. An innovative cylindrical specimen shape eliminated temperature gradients and enabled real-time monitoring of icing. The experimental results were compared with the results obtained using classical theory

In this study, functionalized Multi-Walled Carbon Nanotubes (MWCNTs) grafted with a silane coupling agent (MS) at concentrations of 0.1 %, 0.2 %, 0.3 %, and 0.4 % were used as additives to investigate their impact on the reaction kinetics, working performance, mechanical strength, and drying shrinkage of alkali-activated fly ash/slag (AAFS) pastes. Additionally, various micro-structure techniques,

This paper proposes a fractal derivative model with a non-linear distributed-order (DOFM) to describe particle diffusion with multi-scaling behaviors in alkali-activated materials. The distributed derivative order is a power law function of the scaling factor, which generalizes the linear uniform case. The mean squared displacement in terms of the DOFM is derived as a non-linear form with the dilogarithm

Basic oxygen furnace (BOF) slag is an industrial by-product of the steel industry and has recently been investigated intensively for high-end applications other than road load and land fill. However, to be applied as a high-end raw material BOF slag lacks a quick and simple quantitative phase analysis method compared to the Bogue approach applied to ordinary Portland cement. This study presents a method

The use of carbonated recycled cement paste powder (RCPP) as a mineral admixture affects the properties of the cement paste through multiple effects. This study proposes a model to decouple and quantify these effects based on their contribution to the compactness (1 − porosity) of the paste. Experimental results showed that the filler effect significantly contributed to the increase in compactness

Recently, a hydrous carbonate-containing brucite (HCB) with an approximate composition of MgCO3·35 Mg(OH)2·H2O was postulated as hydration product of binders based on mixtures of reactive magnesia and hydromagnesite (Mg5(CO3)4(OH)2·4H2O). X-ray diffraction showed that the 001 reflection of this phase was split into two reflections at 20 °C, whereas at 60 °C only one reflection occurred. Rietveld refinement

Steel slag blended cement exhibits distinctive exothermic behaviors from cement or fly ash/blast furnace slag blended cement. However, quantitative assessment and prediction are difficult due to the complex interactions between steel slag and cement in time scale, especially at the time when it exceeds the measurement accuracy of isothermal calorimetry. In this study, a quantitative method was proposed

Driven by the need for sustainable construction solutions, there is renewed interest in earth-based materials. Biopolymer stabilizers can enhance the rheological and structural properties of these materials to facilitate their use in 3D printing. This research examined the influence of sodium alginate on the stability, particle interaction, rheology, and 3D printability of kaolinite, a commonly found

It is reported an innovative methodology based on in situ MoKα1 laboratory X-ray powder diffraction (LXRPD) and microtomography (μCT) avoiding any sample conditioning. The pastes are injected in 2.0 mm capillaries and the extremes are just sealed. The measurements take place in the same region of the hydrating paste. Thick capillaries are key to avoiding self-desiccation, which dictates the need of

The extent of utilization of magnesium silicate hydrate (MSH) in construction is limited partly because of insufficient data ascertaining the kinetics of its precipitation. Here, MSH grown homogeneously or heterogeneously in the range of magnesium to silicon solution molar concentration ratios, [Mg]/[Si] = 0.5–1.5, and temperature = 25–80 °C was analyzed for its chemical structure and morphology. Infrared

This study assessed the feasibility of different methods for sulfate optimization of limestone calcined clay cements (LC3). LC3-based pastes were studied with kaolinite and montmorillonite calcined clays and different gypsum contents. Quartz powder was used in reference systems. The sulfate optimization was done using isothermal calorimetry, compressive strength, thermogravimetric analysis, and chemical

Calcium silicate hydrate (C-S-H) is the main binding phase of Portland cement concrete. Though C-S-H is known to be assembled from nanoscale features, there is little experimental study on how C-S-H nano solids interact with each other at the interface, which may hold the key to explain its macroscale strength, creep, and shrinkage behaviour. This work attempts to experimentally quantify the interactions

Limestone (calcite) calcined clay cement (LC3) is a promising low-CO2 binder, but the low activity of calcite cannot compensate the reduction in clinker factor, resulting in low one-day strength and limiting its broad applications. As recent carbon capture and utilization technologies allow scalable production of vaterite, a more reactive CaCO3 polymorph, we overcome the challenge by introducing vaterite

The American Petroleum Institute testing standard (API TR 10TR7) recommends determining the mechanical performance of oil-well cement slurries in an ambient-temperature testing environment. However, with exploration and exploitation resources moving toward deep formations, cement slurries for oil, gas, and geothermal wells are increasingly being utilized in high-temperature and high-pressure (HTHP)

This study presents a reactive transport modelling framework for understanding carbonation processes through pore solution composition, phase assemblage changes in cement-based materials, and pore solution composition changes on steel corrosion. The study emphasizes the significance of considering pore structure changes on mass transport and utilizing a surface complexation model for predicting changes

MgO-based cements have the potential for low carbon binders especially when MgO is sourced from non‑carbonate minerals. Understanding the reaction kinetics and products formed are the keys to pave the way for these binders as construction materials. In this study, the influence of acetate on hydration and subsequent carbonation of reactive MgO is investigated. MgO hydrated in Mg-acetate solution of

Carbonated recycled concrete paste (cRCP) is a unique supplementary cementitious material with pozzolanic properties stemming from the alumina-silica gel. This study reveals that the high early strength of composite cements with cRCP is attributed to its rapid pozzolanic reactivity. 27Al and 29Si NMR investigations show that the alumina-silica gel is consumed after only 7 days of hydration. The rapid

Measuring carbonation is increasingly important, especially for developing novel low-CO2 cements and carbon-capture technologies. This study shows for the first time, the feasibility and advantages of confocal Raman microscopy (CRM) for measuring carbonation depth in cement-based materials, providing high spatial resolution (down to <100 μm), by mapping CaCO3 and Ca(OH)2. Pastes and mortars of different

This research sheds light on the two origins of C3A hydration in structural build-up of cement paste. The largest critical strain is associated with colloidal interaction, whereas the smallest critical strain originates from the cohesion between calcium sulfoaluminate hydrate (CA$H) particles. Interestingly, we have found that the structural build-up primarily relies on the total colloidal interaction

Energy storage provides a greener path of efficient energy utilization. Recent trends of research suggest concrete as a potential thermal energy storage (TES) material. Its cheap commercial availability makes it one of the most deserving candidates. Cement paste is the key glue of concrete, hence performance of its major components in thermal conduction seeks thorough scientific study. Portlandite

The existing commercial superabsorbent polymer (SAP) products have the intrinsic defects of low internal curing efficiency and weakening strength. In this paper, a novel type of organic-inorganic composite SAP (SAPN) modified by nano SiO2 was designed and synthesized. The absorption-desorption kinetics of SAP-N in alkali pore solution were measured to evaluate the structural stability and water retention

Model cement systems form the basis for investigating the influence and behavior of three calcined phyllosilicates during early hydration. Metamuscovite acts as pure filler, accelerates alite hydration and leads to an increased degree of hydration of alite compared to the reference. A different picture emerges for metaillite and metakaolinite. They influence in addition the alite hydration which reaches

This paper reviews the historic developments and provides some perspectives of carbonate binders. Various carbonatable materials have been used to produce carbonate binders using different carbonation techniques. The carbonate binders are mainly composed of calcium/magnesium carbonate and silica/alumina gels. Three crystalline polymorphs, namely calcite, aragonite and vaterite can be formed. The properties

Achieving desired yield stress is crucial for various construction processes, especially in the emerging 3D concrete printing. In this paper, we present the possibility of enhancing yield stress of cement paste through in-situ polymerization and uncover the mechanisms of in-situ polymerized polymers. We investigate the effects of two types of in-situ polymerized polymer, sodium polyacrylate (PAAS)

Ettringite, as the dominant hydration product in cement materials, plays a significant role in the solidification/stabilization of heavy metals. However, the combination and immobilization mechanism of heavy metal ions in ettringite crystals have yet to be fully understood. In this study, ettringite crystals were synthesized using the solution reaction method to investigate the adsorption and chemical

The hardening of cementitious suspensions at early stages of hydration is determined by the kinetics of the binder, which can be characterized by measuring the viscoelastic changes in the elastic storage modulus (G′) using oscillatory rheometry. This study aims to propose a new model that takes into account the physical-colloidal properties of suspensions and the transformations caused by hydration

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 propose a plausible mechanism for the late strength reduction

This paper studies the effect of temperature on the phase assemblages of belite-ye'elimite cement. A comparison is made between thermodynamic modelling and experimental data at 28 and 180 days of hydration at 5, 20, 40, and 60 °C. The fast reaction of ye'elimite and anhydrite resulted in the formation of ettringite, monosulfate and Al(OH)3 during the first day. The slow reaction of belite led to important

The first hours' hydration of fast-setting binder is difficult to monitor due to the limited temporal resolution of common micro-structure-chemistry probes and the complicated product compositions. This study explored using T2 relaxation time distribution data from in-situ 1H nuclear magnetic resonance (NMR) measurement to quantify the early-hydration kinetics of two OPC/CAC/calcium sulfate ternary

The premelted films between cement and ice observed at freezing temperatures play a role in the freeze-thaw damage of cement-based materials, as they play a role in cryo-suction. However, their properties are poorly understood. In this work, we unveil the dynamics and local structure of the premelted film using molecular simulations. Combining those results with a thermodynamic analytical derivation

Recycled concrete fines (RCFs, 0.3 mm ≪ 2.36 mm) are the fine fractions of waste concrete generated during the recycling process. RCFs contain less natural aggregate and more residual cement paste than their coarser counterparts, thus more prone to carbonation. Although carbonation is beneficial for the microstructure and reactivity of RCFs by refining the pores and changing the phase compositions

Relating the empirical slump test to yield stress facilitates the capture of fresh state concrete performance in fundamental quantitative terms whilst avoiding the requirement for expensive rheological equipment. This paper proposes a novel method to predict yield stress from slump by directly measuring the height of the unyielded region, via a 3D reconstruction approach. The efficacy of the proposed

This work examines the micromechanical properties of AFm phases formed in seawater and deionized water. As the interlayer SO42− in the AFm phase is gradually replaced by Cl− in seawater, the basal spacing of the AFm crystal narrows, which promotes the packing density of nanocrystals and their indentation modulus and hardness, i.e., Cl-AFm (Friedel's salt) > SO4-Cl-AFm (Kuzel's salt) > SO4-AFm (monosulphate)

The solubility of relevant phases in the calcium aluminate cements with limestone and in calcium sulfoaluminate cements with gypsum indicate several potential phase assemblages which might be formed during hydration. Thermodynamic calculations and pore solution data indicate that initially the solution is oversaturated with respect to several phases and thermodynamically metastable phase combinations

This work focuses on the investigation of ongoing processes in the pre- and postnucleation stage of C-S-H precipitation at pH 12 and pH 13. Calcium induces the condensation of smaller silicate species to bigger oligomers in the prenucleation stage. By titration in combination with ion-selective electrodes, the effects of additives on the formation of C-S-H can be monitored and quantified in terms of

Recent progress in methods used in the multiscale characterization of cementitious systems is reviewed, focusing on advances in imaging, scattering, and spectroscopy. The review includes relevant applications and developments in machine learning and other data analytics approaches to enhance characterization. Developments in imaging using light and electron microscopy as well as x-ray (i.e., from synchrotron)

Abstract not available

This study examined the effect of silica fume contents on the rheological behavior of slag-fly ash-silica fume-based geopolymer pastes by packing density measurement, low-field NMR, zeta potential, dynamic light scattering and FTIR analyses. Incorporating silica fume into sodium hydroxide (SH)-activated geopolymer pastes resulted in the decrease of packing density and the increases of yield stress

Optimising the hydration of cementitious materials is crucial to leverage their full potential and avoid wasting resources, embodied energy and CO2. Understanding the fundamental mechanisms is key to reach these objectives. In this paper, we review progress in understanding hydration kinetics. We highlight how our practical understanding of cementitious materials is linked to the more fundamental field

Recycling concrete (RC) produced with recycled aggregates (RA) obtained from demolished concrete structures bears the risk of an alkali-silica reaction (ASR). In this study, the interplay between aggregate reactivity and alkalis contributed by the cement and the RA is investigated. Three sets of concrete mixtures are produced using RA and natural aggregates, both reactive and non-reactive ones. Caesium

Water distribution in hardened paste and its dynamics determine many properties related to durability. Moisture distribution was determined by thermoporometry combined with vacuum drying. Dynamics of confined water were measured by broadband dielectric spectroscopy. Water in pores <2.4 nm cannot form tetrahedral ice structure due to geometrical constraints. The volume of unfrozen water (in interlayer

Abstract not available

This study characterizes the hygrothermal and microstructural properties of cement composites containing aluminosilicate cenospheres. It involved the preparation of six mortar mixtures based on CEM I 42.5R cement, in which cenospheres accounted for 0 to 100 % of the aggregate content. The research included measurements of thermal properties, compressive and bending strength tests, density tests on

A promising approach to accelerate cement hydration has been discovered, wherein superfine particles are utilized to introduce additional nucleation sites for the growth of hydration products. This study investigated the effects of synthetic amorphous aluminum hydroxide (AH3), bayerite, and boehmite on SCGM properties. The results show that amorphous AH3 acted as nucleation sites for the growth of

We study the conductive heat transport through calcium silicate hydrate (C-S-H) and organically cross-linked C-S-H via experiments, micromechanical homogenization theory, and molecular simulations. We find that C-S-H's intrinsic thermal conductivity falls below its amorphous limit when cross-linked with short-chain organosilanes. The observed reduction correlates with the alkyl chain length of the

Alkali-activated slags (AASs) are often reported to exhibit fast settings, undermining their utilisation as sustainable binders from a technological point of view. Although gypsum was shown in previous studies to change the setting time of AASs, understanding the mechanism behind the changes in the reactivity and microstructure of the AASs in the presence of gypsum remains unclear which limits its

Progress in understanding the use of SCMs in blended Portland cement and related effects is reviewed. An optimized use of cement components will avoid wasting unreacted particles that do not contribute to the mechanical and durability performances. The reactivity of cement components increases with fineness and by controlled production processes. Clinker may become a minor component in the cementitious