Cement pastes made with ternary binders containing Portland cement, calcined smectitic clay and limestone were subjected to chloride migration and diffusion. Microstructural changes due to chloride ingress were studied by mercury intrusion porosimetry and SEM back-scattered electron image analysis, while chemical changes were investigated via chloride binding isotherms complemented by thermogravimetric

Alkaline solid wastes, such as recycled concrete fines, can integrate with CO2 to produce high-purity vaterite CaCO3 via leaching‑carbonation mineralization. This study aims to examine the stability and nucleation effects of the metastable vaterite relative to stable conventional calcite in cement paste systems. To better elucidate the underlying mechanisms, their influence in the pure C3S/C3A phase

This study examines the stability of dolomitic filler (DF), both in isolation and in interaction with supplementary cementitious materials (SCMs), when immersed in water media at different pH at 40 °C. Additionally, the interaction of DF with Portland cement (PC) is analyzed. In the presence of SCMs or PC, results reveal that DF undergoes dedolomitization in alkaline environments, which confirms the

The use of aluminum sulfate (Al2(SO4)3)-based alkali-free accelerators in shotcrete often impeded tricalcium silicate (C3S) hydration, leading to poor ultra-early strength development. To address this, a novel stage-wise kinetic control strategy was proposed to regulate the sequential formation of ettringite and C-S-H gel through the delayed addition of C-S-H nano seeds. The dosage of C-S-H nano seeds

The carbonation of cementitious calcium silicates, specifically tricalcium silicate (C₃S) and dicalcium silicate (C₂S), is crucial for Carbon Capture and Utilization (CCU) in reducing CO₂ emissions in the cement and concrete industry. Controlling these reactions, including the rate and phase evolution necessary for producing desirable carbonated products, poses significant challenges. A lack of continuous

This study explores the regulatory mechanisms of trace calcium phosphate (CaP) in the hydration of Portland cement. The results indicate that incorporating 0.001 wt% CaP extends the induction period by forming a passivation film while simultaneously accelerating the hydration rate during the acceleration phase as a nucleation agent, thereby improving hydration efficiency and uniformity. CaP enhances

Establishing direct relations between alkali-silica reaction (ASR) expansion, crystallization pressure build-up, and phase assemblage changes is a critical step towards predictive modeling of ASR damage. To address this, we propose a strategy that combines thermodynamic modeling with micromechanics. First, we complete the thermodynamic database for ASR products, including nanocrystalline ASR-P1 data

Cold joints in extruded concrete structures form once the exposed surface of a deposited filament dries prematurely and gets sequentially covered by a layer of fresh concrete. This creates a material heterogeneity which lowers the structural durability and shortens the designed service life. Many factors concurrently affect cold joint formation, yet a suitable tool for their categorization is missing

Ettringite forms directly after Portland cement is mixed with water. Polycarboxylate ether-type superplasticizers can stabilize nano-ettringite particles in the pore solution and modify ettringite formation. It was previously impossible to isolate the nano-ettringite from the cement pore solution at commonly used water-to-cement (w/c) ratios of 0.5 and lower. Therefore, the exact morphology of ettringite

The alkali-activation process is known to be rapid and thus challenging to characterize. In this work, we used proton density magnetic resonance imaging (PD-MRI) to observe the water distribution during the alkali-activation process of metakaolin. With the obtained visible brightness changing of the solid phase and the bled water, the setting time of the alkali-activated materials (AAMs) can be determined

Basic magnesium sulfate cement (BMSC) contains excess MgO causing volume instability, limiting its applications. Although forced carbonation stabilizes MgO into carbonates, it compromises strength by transforming strength-contributing phases. This study presents a forced carbonation strategy based on hierarchical pore regulation. We constructed a multi-scale pore network from nano to macro scale, optimizing

Cementitious materials can achieve desirable strength development and reduced cracking potential under moist or immersed conditions. However, in this work, we found that alkali-activated slag (AAS) pastes can crack underwater, with a higher silicate modulus showing more pronounced cracking. Chemically, the C-(N-)A-S-H gel in the paste with a higher silicate modulus showed a higher Na/Si ratio and a

Ultra-high toughness cementitious composites (UHTCC) are increasingly employed to repair and strengthen deteriorated concrete structures, yet the critical microstructural evolution and micromechanical properties of overlay transition zone (OTZ) remain underexplored. We report a comprehensive, curing time-dependent study of OTZ between cast and sprayed UHTCC and concrete substrates (CS). The findings

The use of SCMs as partial substitutes for PC has made C-A-S-H a key binding phase in modern cement, yet its crystallization mechanism remains elusive. This study investigates the early stages of synthetic C-A-S-H formation and compares them with C-S-H using double addition of stoichiometric calcium and silicon amounts at a Ca/Al ratio of 5. Through real-time monitoring of solution parameters—transmittance

Ternesite exhibits significant carbonation reactivity and the resultant carbonation products show favorable effects on the performance of Portland cement. Therefore, this study investigated the effects of semi-dry carbonated ternesite on the hydration and hardening characteristics of Portland cement when utilized as a supplementary cementitious material (SCM). The results indicate that the carbonation

Modelling cement-based materials from the early-age to the hardened state is crucial in numerous applications such as deep well cementing or 3D printing, which require comprehensive modelling of multiphysics couplings. To answer these requirements, a thermodynamically consistent time-dependent constitutive model based on the extent of hydration is developed in the framework of thermoporomechanics of

Magnesium silicate hydrate (M-S-H) binder has been considered a promising alternative binder for engineering application. However, its low pH environment raises concerns for its adoption in steel reinforced concrete structures. To evaluate the corrosion behavior of steel reinforced M-S-H system under ambient and chloride environments, electrochemical tests were conducted. Additionally, phase formation

Deleterious aggregate reactions induced by iron sulfide minerals, especially pyrrhotite and pyrite, have devastated concrete structures across many global regions. While these minerals have been extensively studied under acidic conditions, their behavior in alkaline environments, such as concrete, remains poorly understood. This study investigates the kinetics and mechanisms of iron sulfide dissolution

Understanding of the load-rate dependence of fiber pull-out from concrete has been hindered by the large scatter of test data. Relatively little attention has been given to the statistical nature of single-fiber pull-out under different loading rates. The present study is based on a probabilistic interpretation of the pull-out phenomenon, assessing the statistical fluctuations observed in the common

The heterogeneous nature of the cement clinker, its complex coupled dissolution/re-precipitation process and the complex defect chemistry of the hydrates formed during cement hydration, make that the nucleation and growth mechanisms of cement hydrates are not fully understood. Recent studies have suggested the existence of a disordered precursor prior to the crystallization of C-S-H. Here, a combination

Using industrial by-products as substitutes for Ordinary Portland Cement (OPC) is a promising strategy to reduce its environmental impact. However, heavy metals like Pb strongly interfere with initial kinetics. The dynamic physicochemical environment makes it challenging to identify the key factors. Here, we employed in-situ XRD as a time-dependent method, alongside conventional characterization techniques

Effective, low-cost and simplistic self-healing strategies for cement-based systems are attractive. This work proposed a concept where coarse clinker particles were used to replace cement and acted as the healing agent, and the effectiveness was validated by comprehensive studies. The results showed the high potential of the clinker sizes (40–60 μm, 60–90 μm, 0.5–1 mm) and replacement ratios (20–40%)

This paper reviews the efforts taken towards developing bauxite residue (BR) based blended cements (>30% substitution) contributing to the cement industry's net-zero targets, while utilizing the Bayer-processes by-product. We provide a comprehensive review of physical properties, element composition and mineralogy of Bayer and sintering BR. This defines the main challenges that BR based SCMs have to

Cracks reduce the strength and service life of concrete structures. Although high-performance crack filling materials are available in market, achieving deep infiltration is often difficult. In this work, we propose the utilization of a magnetic approach for enhanced infiltration and examine the mechanisms governing its effectiveness. Our experiments demonstrate that employing magnetic fields in the

Air lime-based mortars and plasters are preferred for the restoration of historic masonry due to their high compatibility, and for modern constructions given their lower environmental impact. However, their slow setting (via carbonation) and their limited strength hinder their widespread use. This study explores the influence of nano- and micro-cellulose additives dosed during lime slaking on the formation

While carbon sequestration with dicalcium silicate (C2S) offers a promising approach, the underlying mechanisms governing the contrasting carbonation efficiencies of different polymorphs remain poorly understood. Taking three C2S polymorphs as a paradigm, this study uses Grand Canonical Monte Carlo simulations to investigate CO2 physisorption within αL-, β-, and γ-C2S mesopores under dry, unhydrated

Incorporating aluminum dihydrogen phosphate into magnesium phosphate cement (MPC), including magnesium ammonium phosphate cement (AMAPC) and magnesium potassium phosphate cement (AMKPC), significantly enhances both compressive strength and water resistance. The results show that AMAPC-3 exhibited a remarkable increase in compressive strength, maintaining a compressive strength retention ratio of 0

Calcium silicate hydrate (C-S-H) is a crucial cement hydration product for the strength and durability of concrete. While previous studies have extensively investigated the structural and compositional characteristics of C-S-H, they mostly focused on average properties within ensemble systems. In this work, we use electron energy loss spectroscopy (EELS), electron nano-tomography, and other spectroscopies

One of the most significant challenges facing extrusion-based 3D concrete printing (3DCP) is the anisotropy present in the printed material: under load, the observed performance is typically lower than a cast equivalent and significantly so in certain directions. In addition, the performance is also more variable than cast material. These observations are, in part, due to surface moisture evaporation

X-ray powder diffraction (XRD) was used to characterize and quantify nano-crystalline C-S-H in hydrated tricalcium silicate (C3S), Portland cement, and siliceous fly ash blended cement using Rietveld analysis with partial or no known crystal structure (PONKCS) coupled with thermalgravimetric analysis (TGA). Calibration of the C-S-H profile was carried out by minimizing bound water content detected

With the aim to identify the mechanisms governing nonlinear basic creep of concrete under uniaxial compression, a micromechanics model is presented. Extending the affinity concept for nonlinear creep, it describes that every microcrack incrementally increases the damage of concrete, leading to a step-wise increase of its compliance. Experimental data are taken from the literature. Strain and acoustic

The diffusion of chloride critically affects the durability of reinforced concrete in exposure environments. Hydrocalumite-like (AFm) phases can bind chlorides to form Friedel's salts, retarding chloride ingress. However, the stability and structural parameters of Friedel's salts with mixed-anion interlayers are not fully understood. First principles computation was performed to provide the energy-minimum

As carbon dioxide (CO2) sequestration technology begins to emerge in the construction and building materials sectors, industry stakeholders require quantifiable assurance mineralized CO2 content of emerging carbonated products. This study adapts a Digestion-Titration Method (DTM) for the determination of mineralized CO2 content in cementitious materials based on tests that were originally developed

Limestone powder (LS) with large particle sizes is widely used, but its effect on water migration behavior remains unclear. This study investigates the influence of LS and viscosity-enhancing admixtures (VEAs) on the water migration behavior and water distribution in fresh cement paste using 1H low-field nuclear magnetic resonance (LF-NMR). Results indicate that LS increases the size of water migration

Aerated concrete exhibits anomalous water transport, similar to mortar and concrete. Several factors, including water sensitivity, air entrapment, and gravity, are considered to be the causes; however, they are currently not quantitatively understood. This study aimed to clarify the mechanisms underlying the anomalous absorption of aerated concrete through liquid absorption experiments and numerical

The overall effect of wet carbonation recycled concrete fines (RCF) on the chloride binding capacity of cement paste was quantitatively decoupled into the effect of paste pH reduction, and the contribution of each component (uncarbonated phase, CaCO3, silica gel) in the wet carbonated RCF. Results indicate that incorporating wet carbonated RCF decreases both the chemical and physical chloride binding

Concrete suffers significant performance degradation when exposed to high temperatures. This study explored the beneficial role of waste glass powder (WGP) in mitigating thermal damage and ultra-high performance concrete (UHPC) after elevated temperature exposure. The mechanism was elucidated through the chemical and microstructure changes, the composition of hydrates after exposure to elevated temperatures

In cementitious materials, continuous hydration of mineral phases and creep always coexist, making it difficult to decouple the effect of hydration on creep measurements, which are invariably time-dependent. This study compares a real hydration (aging) system with an equivalent hydration (non-aging) system. In the non-aging system, the unhydrated phase was replaced with inert quartz at specific ages

To reduce cement's carbon footprint, there is growing interest in commercial adoption of sustainable SCMs such as calcined clays. However, the existing ASTM standard (R3 test, C1897) to test the reactivity of such clays takes up to 7 days and cannot be used for real-time quality control in an industrial setting. We address this issue by introducing a 5-min Ultra-Rapid Reactivity (UR2) test. By dissolving

The challenge of compatibility between polycarboxylate superplasticizer (PCE) and β-naphthalene sulfonate superplasticizer (BNS) remains an enduring puzzle, requiring a comprehensive understanding of their interaction mechanism. In our study, the macroscopic properties, microscopic interfacial adsorption, and intermolecular forces are investigated in detail to elucidate the interaction between PCE

Regulating the resistivity of ultra-high-performance concrete (UHPC) infrastructure is crucial for endowing UHPC with intelligence and multifunctionality. In this study, we proposed a new approach to enhance the electrical conductivity of UHPC via high-temperature electric induction. When the temperature of electric-cured UHPC was heated to 90–130 °C, the resistivity dropped sharply. After electric

The combined effects of water pressure and water penetration on the mechanical behavior of concrete under hydraulic loading were investigated. When concrete is subjected to water pressure, a saturated zone forms near the surface and gradually progresses toward the interior over time, resulting in a non-homogeneous hybrid state with a saturated envelope and humid core (hybrid saturated state) during

Concrete features significant microstructural heterogeneity which affects its mechanical behavior. Strain localization in the matrix phase of concrete has received significant attention due to its relation to microcracking and our ability to quantify it with X-ray computed tomography (XRCT). In contrast, stresses in sand and aggregates remain largely unmeasured but remain critical for micromechanics-based

Hydrophobic-modified silica fume (HSF) with superior dispersion was synthesized by coating silane onto SF surface. Its influence on cement hydration, microstructure and properties of cement pastes was investigated. Results indicated that the silane on SF surface visibly depressed pozzolanic reaction at early ages. HSF retarded cement hydration by adsorbing on cement surface and more importantly, by

Transformation of C-S-H is crucial in the deterioration of concrete at high temperatures. This study investigates the composition, structure, and morphology of C-S-H from 30 °C to 1000 °C using in-situ heating XRD, TGA/TG-IR, in-situ heating XPS, and in-situ heating TEM combined with image recognition. The results reveal that during heating, C-S-H undergoes weakly and strongly bound water loss, dehydroxylation

Alkali-Silica Reaction (ASR) is a long-term chemical degradation induced in concrete by the difference in pH between the aggregate and the cement paste. ASR advancement is thus driven by the combination of the ionic species diffusion and the dissolution of reactive silica. In this paper, the reactive transport model is based on the principal sequence of the ASR-mechanisms: hydroxide, alkali and calcium

Severe scaling and spalling are commonly observed on tunnel lining surfaces in sulfate-rich environments. Due to humidity gradients, sulfate solution in rock fissures migrates through capillary action to the concrete exposed face, leading to physical crystallization precipitation at free-face zone and chemical sulfate attack at soil-facing zone, resulting in concrete expansion and crack. Existing models

A new insight into self-antifoaming effect of CO2 bubble was proposed by exploring the evolution of entrained CO2 bubbles in fresh cement paste. The disappearance process of CO2 bubbles was observed, resulting in the reduction of air content. The evolution of CO2 bubbles eventually formed two kinds of pore structures: hollow spherical shell structure (HSS) and interior filled spherical shell structure

Recent findings indicate that the effect of superplasticizers on decreasing the yield stress of cementitious suspensions is attributed to the modification of percolation threshold in addition to interparticle force. These dual effects complicate the assessment of yield stress dependence on the superplasticizer type and dosage, as yield stress can no longer be expressed as a separable function of interparticle

The rheological properties of cement-based materials made with manufactured sand vary with the content and physio-chemical properties of microfines in the sand. However, the evaluation of rheological properties regarding the structural build-up at early-age hydration remains challenging for the cementitious materials prepared with different manufactured sands, due to complicated underlying structuration

This paper investigates the autogenous shrinkage of alkali-activated slag (AAS) under thermal curing using a tailored corrugated tube system. The results reveal that thermal curing decreases the total deformation of AAS mortar due to thermal expansion while increasing autogenous shrinkage. This enhanced autogenous shrinkage results from the interaction of multiple factors, with the dominant influences

This study quantitatively examines the impact of aluminum (Al) in C–A–S–H gel2In cement notation for oxides, C = CaO, S = SiO2, A = Al2O3, H = H2O, and F = Fe2O3. C–(A)–S–H gel represents both calcium–silicate–hydrate (C–S–H) and aluminum-incorporated calcium–silicate–hydrate (C–A–S–H) gels in this study.2 on the chloride binding capacity of blended cement paste containing supplementary cementitious

Characterising steel corrosion at the steel-concrete interface and linking it to concrete damage is challenging due to limitations of current non-destructive techniques. This study combines electrical resistance measurements, full-field image-based analyses and analytical techniques to comprehensively characterise steel corrosion and damage in small-scale specimens.