It is well-established that aqueous carbonation of recycled concrete paste produces calcium carbonate and an amorphous alumina-silica gel as the main products. However, sparse information is available about the structure and composition of the gel. This work focuses on these properties by carbonation of synthesized C-S-H (Ca/Si = 1.75) alone and blended with portlandite and ettringite. Wet carbonation

Superabsorbent polymers (SAPs) are widely studied as internal curing agents in high-performance concrete, but their adverse effects on pore structure remain a challenge. This study introduces an innovative cement-integrated SAP (CiSAP) by modifying the interface, using KH570-modified cement (KMC) as the functional core. By optimizing KMC content, the microstructure was improved, leading to enhanced

This study investigates the role of L-aspartic (L-Asp) in regulating the crystallisation of hydrated magnesium carbonates (HMCs) in carbonation-cured reactive MgO (RM). The effects of L-Asp on hydration kinetics, bulk density, compressive strength, phase composition, carbon sequestration, microstructure and morphology of RM composites were examined to understand its influence on the coupled hydration

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Salt scaling damage peaks at a specific salt concentration, known as the pessimum concentration. However, reported pessimum concentrations vary widely, lacking a theoretical explanation. The microstructure of concrete is an important characteristic influencing the freezing behavior of pore solution, which is often neglected in salt scaling studies. This study investigates the effect of concrete microstructure

The unavoidable challenge of weakened interlayers in 3D Concrete Printing yields diminished mechanical performance due to compromised micro- and macrostructural properties that are a culmination of the material and process parameters, in conjunction with ambient environmental conditions. A bond enhancement technique is proposed that is characterised by the surface treatment of interlayer surfaces with

Electrochemical impedance spectroscopy (EIS) and linear polarization resistance (LPR) are widely adopted to measure steel/concrete corrosion. However, the variation in electrode configurations often lead to inconsistent results. In this study, different reference electrode (RE) and counter electrode (CE) configurations were adopted on the same steel/mortar specimen to investigate their influence on

The diffusion coefficient of unsaturated cementitious materials is a crucial factor in assessing their transport-related properties for durability evaluation. However, predicting the diffusion coefficient of unsaturated cementitious media through mathematical modeling is challenging due to the variability of fitting parameters in existing models. This work explores the impact of pore structure and

Controlling autogenous shrinkage is one of the challenges for alkali-activated slag application. This paper reports a pair of approaches targeting the autogenous shrinkage mitigation: one is to use sodium desulfurization ash (SDA) and calcium carbide residue (CCR) as combined solid activators, rather than using sodium silicate solution; and another is to facilitate the formation of U-phase crystals

The influence of slaking on the properties of natural hydraulic limes (NHL) has been little studied so far. Laboratory-manufactured limes have been produced to investigate the mineralogical changes that occur during the slaking process. Two different hydration methods have been compared: conventional slaking, by adding water in a 1:1 water:CaO ratio, and passive slaking, by exposure of the quicklimes

The velocity properties of concrete are highly sensitive to the changes of concrete structure after high temperatures. Experimental and theoretical data indicate a reduction in velocities and a decrease in the Vp/Vs ratio with temperature. After the heated concrete is saturated with water, the dependence of velocities on temperature shows a different trend compared with the dry specimen. The Vp/Vs

To explore the governing mechanism underlying the tensile fatigue behavior of Ultra-high Performance Fiber Reinforced Cementitious Composites (UHPFRC), this study tested eight specimens using four advanced non-destructive measurement techniques. First, magnetoscopy is conducted on each specimen to determine the local fiber orientation and volume. Afterward, seven specimens are statically preloaded

This study evaluated the mechanical and durability performance of CEM I and CEM I plus limestone blended concrete produced with calcined clays (CC) with a varying meta-kaolinite content (70, 50 or 20 wt%). Results revealed that concrete with >45 MPa can be produced with a CC with only 20 wt% meta-kaolinite. Increased compressive and flexural strengths were obtained using higher meta-kaolinite content

Ultra-early mechanical properties are critical for shotcrete performance, significantly influenced by ettringite and calcium silicate hydrate (C-S-H) formed during the initial hydration stage and free water. This study investigates the individual and synergistic effects of these phases on mechanical behavior using equivalent cement pastes. In this system, cement was entirely replaced with dolomite

The toughening efficiency of liquid polymers (LP) for cement-based materials is usually constrained by their agglomeration and discontinuous dispersion in matrix. In this study, a novel hydrogel-guided dispersion strategy was developed, in which the incorporation of 3.0 wt% hydrogel enabled the uniform distribution of 10.0 wt% LP within cement matrix as a continuous network. Accordingly, the flexural

Magnesium salts are key components of liquid alkali-free accelerator; however, their influence on the setting and hardening of accelerated cement pastes remains unclear. This study systematically investigates the role of different magnesium salts by preparing and examining aluminum sulfate (AS)-based accelerators at different dosages. The effects of the accelerators on the setting and early age mechanical

Basaltic fines (BF) are a promising source of supplementary cementitious materials (SCMs) due to their worldwide availability, low cost, and adequate chemistry. However, they need to be processed to be used as SCMs, as they are otherwise inert. We explore mechanochemical activation (MCA), where raw materials are exposed to high-energy grinding, which increases powder fineness and amorphous content

Efflorescence is a significant aesthetic and structural issue for alkali-activated materials (AAMs). This study addressed this issue at the aggregate level for the first time. The results indicated that substituting sand with aluminosilicate-based lightweight fine aggregate (LWFA) by 20 % or 50 % in volume reduced the efflorescence of alkali-activated slag (AAS) mortars by 14.6 % or 43 %, respectively

Hydroxyethyl methyl cellulose ethers (HEMCs) are of increasing interest for their ability to modify rheology and workability of cementitious systems and most importantly with the increase in automation in cement industry. In this paper, the effect of two HEMCs - with similar molecular masses but different degrees of substitution (DS) and molar substitution (MS) - on the hydration of tricalcium silicate

This study investigates the Alkali-Silica Reaction (ASR) behavior of non-traditional alkali-activated materials (NAAMs) utilizing unconventional precursors, including calcined clays (CC), volcanic ashes (VA), ground bottom ashes (GBA), and fluidized bed combustion ashes (FBC). Using ASTM-based accelerated and non-accelerated methods, ASR expansions were assessed across aggregates with varying reactivity

This study investigated the evolution of water content and carbonation in OPC cement paste under low, intermediate, and high relative humidity (RH) conditions, emphasizing the role of water in accelerated carbonation and microstructural modifications. Under high RH, the carbonation suppressed after 28 days owing to calcium ion accumulation at the surface, precipitating as calcite. This calcite formation

The high-gravity (higee) carbonation process has emerged as a promising method for enhancing the carbonation efficiency of basic oxygen furnace slag (BOFS). While this process has proven effective in carbonating BOFS, the underlying mechanisms are not yet fully understood. To investigate this, we selected two types of BOFS: calcium hydroxide-rich (CH-rich) and calcium silicate-rich (CS-rich) BOFS,

In this study, the carbonation behaviour and mechanisms of the ferrite (C4AF) phase in cement were investigated for the first time through enforced wet carbonation. The results confirm that ferrite carbonation is a spontaneous chemical reaction, the kinetics of which are predominantly controlled by monocarbonate precipitation. The carbonation process involved the initial precipitation of hemi/monocarbonate

Carbonated aerated concrete (CAC) is recognized as a low-energy alternative to conventional aerated concrete. In this study, the effects of curing methods and binder design on CAC performance, microstructure, and phase evolution are examined. A key contribution is the identification of the balance between pre-hydration and carbonation, a critical yet underexplored factor in strength development. It

Understanding the structure and polymerization behavior of Fe-bearing alkali-activated slags (AASs) is crucial for optimizing their macroscopic properties and expanding their applications in sustainable construction materials, radioactive waste storage, carbon sequestration, and other environmental technologies. This paper investigates the effect of iron oxidation state in precursor slags on the polymerization

This study focuses on the influence of pH, aqueous phase composition and superplasticizers on the particle interactions in pure metakaolin suspensions. It was found increasing pH up to 11 led to the decrease of the particle agglomeration due to the higher OH− adsorption onto metakaolin particles, which increased the absolute zeta potential and generates higher electrostatic repulsive forces. Above

Ultra-high performance seawater sea-sand concrete (UHP-SSC) exhibits outstanding mechanical properties, but the high cracking potential of UHP-SSC under restrained conditions should not be neglected. As steel fibers pose a corrosion risk when used in UHP-SSC, this study investigated and assessed the crack resistance of UHP-SSCs reinforced with non-metallic fibers. Cracking experiments were conducted

Interface between calcium silicate hydrate (CSH) and polymers is crucial for the mechanical properties and durability. However, direct experimental determination of interfacial mechanics at nanoscale has not been reported. Herein, atomic force microscopy (AFM) with grafted Poly (1-vinylpyrrolidone-co-acrylic acid) (PVP-co-PAA) on AFM tips were utilized to measure interfacial properties between CSH

A detailed microstructural investigation of a concrete expanding due to alkali‑carbonate reaction (ACR) shows that the cement paste adjacent to reactive aggregate particles is carbonated, which leads to a sulfur redistribution resembling internal sulfate attack. Simultaneously to dedolomitization, partial dissolution of illite occurs in aggregate particles leading to the formation of brucite, hydrotalcite

Organic additives play important roles in enhancing the formation of Mg‑carbonates and reaction kinetics in MgO-based cements. However, little is known about the influences of organics on the formation pathways of carbonate phases and whether organo-modified Mg‑carbonates exist. We found that acetate can be involved in the formation of a new hydrated magnesium carbonate phase containing acetate: [Mg5(CO3)3

This study presents an in-depth examination of the sensitivity of highly nonlinear solitary waves (HNSWs) to variations in the curing period, the water-to-cement (w/c) ratio, and the mechanical properties of cement. Experimental results verify that the travel times and amplitude ratios of the HNSWs are highly sensitive to changes in curing time of 1 to 28 days, the w/c ratio of 0.3 to 0.6, the elastic

This study investigated microstructural changes in hardened cement paste with and without a water-dispersible polyurethane (PU) ether compound under varying relative humidity (RH) levels. The small-angle X-ray scattering technique was used to analyse the agglomeration, piling, and densification of calcium silicate hydrate (C-S-H) units. Mercury intrusion porosimetry and water vapour sorption isotherms

This research investigates the influence of alkaline concentration and calcium content on the shrinkage mechanisms, carbonation resistance and reinforcement corrosion of alkali-activated concrete system composed of calcined clay and ground granulated blast furnace slag (GGBFS). An increase in Na2O% led to an improvement in the mechanical performance, pore structure refinement, reducing both accelerated

An automated experimental system enables precise evaluation of cement dispersant performance through rheological measurements of 230 mL mortar samples. Analysis of 129 mortar samples demonstrated comprehensive characterization of dispersant effects beyond traditional manual testing capabilities. Principal component analysis revealed distinct patterns in torque measurements, explaining the variance

The significant global CO2 emissions from the cement industry coerces the development of alternative, low-carbon cement. Reactive MgO cement is a promising candidate, reacting with CO2 to form hydrated magnesium carbonates. This high-pressure X-ray diffraction study investigates the intrinsic mechanical properties of artinite, a binding phase in reactive MgO cement. Artinite remains structurally resolved

Cements based on hydrated magnesium carbonates are an alternative binder system with high CO2 sequestration ability. The present study examines the effect of silica, a by-product of MgO production from magnesium-silicate rocks, in MgO/nesquehonite binders. A high Mg/Si ratio of 3 was used to allow the formation of both the hydrous carbonate-containing brucite (HCB) phase and the magnesium silicate

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