Hydrated magnesium carbonate cements prepared from MgO and carbonates such as hydromagnesite (Mg5(CO3)4(OH)2·4H2O) or nesquehonite (MgCO3ˑ3H2O) have potential for carbon sequestration during hardening. This study investigates the hydration of MgO/nesquehonite blends with up to 50 wt% of nesquehonite. Nesquehonite is highly reactive in the presence of MgO and water. The replacement of 50 wt% MgO by

Portland cement (PC) has been used and developed since the early 19th century. Although the compositional ranges of PC clinkers are generally specified in standards, there is a lack of information on the variability of industrial clinkers. Furthermore, with an increase in the use of alternative mineral and fuel feeds, it is important to understand the evolution of clinker chemistry and mineralogy which

An alternative low-energy alinite-chlormayenite clinker was produced and its hydration with different gypsum content was studied. The clinker was produced at 1225 °C using reagent-grade materials in an electric kiln with alinite, larnite, and chlormayenite content of 48, 24, and 16 wt%, respectively. The hydration kinetics of the clinker with different gypsum additions (0,10, 20, and 40 wt%) did not

Alkali-activated materials (AAMs) are a class of potentially eco-friendly construction materials that can contribute to reduce the environmental impact of the construction sector by offering an alternative to Portland cement (PC). With the rapid development of both computational capabilities and theoretical insights into alkali-activation reaction processes, there has been a surge in research activities

The investigations of clinker-free model and synthetic cement systems reveal deeper insight into the behavior of metasmectite during early hydration. The use of metasmectite accelerates the aluminate clinker reaction and influences the degree of hydration of alite. Its chemical reactivity can be demonstrated in clinker-free as well as model cement systems by direct quantification of the metasmectite

Calcium sulfates such as anhydrite, hemihydrate, and gypsum are used extensively in building materials, wall board, and biomaterials. The correlation between nanoscale structure and macroscopic properties, however, remains incompletely understood. We employed molecular dynamics simulations with the Interface Force Field (IFF) to examine sensitive hydration reactions, anisotropic thermal and mechanical

The influence of vegetable oil and steel slag aggregates on the drying shrinkage and carbonation performance of steel slag-based alkali activated materials was investigated. Decrease in carbonation rates by up to 19% attributed to the formation of metal soap phases which strongly reduced the gel and small capillary porosity as well as the specific surface area of the materials. When combined with steel

The formation behaviors of tricalcium silicate (C3S) in modified EAF slag were investigated to assess the feasibility of using EAF slag for cement clinker production. For the formation conditions of C3S, the C3S content in slag exhibits a notable increase with elevating slag basicity and reaction time, while only a slight enhancement with temperature rising from 1400 °C to 1500 °C. The C3S formation

This study explores different methods for precipitating carbonated Mg-Fe3+ layered double hydroxides (LDHs) with Mg/Fe3+ ratios ranging from 2 to 2.5. Two synthesis approaches were investigated: a) CO3-Mg-Fe3+-LDH co-precipitated directly from MgO, Fe(NO3)3 and Na2CO3 and b) NO3-Mg-Fe3+-LDH precipitated by adding NaOH to Mg(NO3)2-Fe(NO3)3 solutions, followed by ion exchange with Na2CO3 to form CO3-Mg-Fe3+-LDH

The cement content in concrete significantly influences critical properties such as durability, permeability, strength, and workability. Traditional methods for estimating the cement content face limitations. These include the need for comprehensive chemical and solubility knowledge, extensive sample preparation, and their time-consuming and destructive nature. This study investigates the application

The demand for accurate characterization of slag-based CEM II concretes is becoming increasingly important as the construction sector shifts towards eco-efficient materials. Here, the basic creep behavior of slag-based CEM II concretes is traced back to mixture-invariant hydrate properties. Therefore, an experimentally validated three-step micro-viscoelastic model for CEM I/OPC-concretes is complemented

Xonotlite forms under hydrothermal conditions and it dehydrates to β-wollastonite between 770 and 800 °C under atmospheric pressure. The solubility of xonotlite is poorly known, as the experimental datasets reported in literature differ by as much as 10 log units. This study investigates the impact of temperature (7, 20, 50 and 80 °C) on the solubility of xonotlite by dissolution experiments from undersaturation

The accelerated mortar bar test (AMBT) for pyrrhotite (Fe1-xS) containing aggregates accelerates expansion using two regimes: Phase I, during which Fe1-xS oxidation to iron hydroxide is accelerated by bleach and storage at 80 °C; Phase II that promotes thaumasite formation with continued bleach soaking and storage at 4 °C. Two bleach concentrations and one aggregate containing 0.5 wt% Fe1-xS are tested

The biodeterioration of concrete elements in sewer systems and their repair is of significant economic and societal concern. However, the available test methods to assess the performance of cementitious materials under the relevant conditions are insufficiently validated. In the present study, two biological test methods and a standardised chemical test were applied to two sewer repair mortars and

Flowing effect on concrete deterioration caused by sulfate attack at varying flow rates was studied. It was found that an increased flow rate can expedite the weakening of the concrete's elastic modulus in the short term, thus causing an earlier onset of this weakening. However, the long-term deterioration of the elastic modulus remains unaffected by the flow rate due to the limited amount of products

This study focuses on the numerical modeling of the reaction and microstructure development of a one-part granite-based geopolymer, which is often used for carbon capture and storage (CCS) applications. This work extends the capabilities of GeoMicro3D to model one-part geopolymers containing different precursors and activators (solid and in solution). The model considers the particle size distribution

The evolution of early mechanical properties of 3D-printed concrete (3DPC) plays a crucial role in early constructability, while current methods face challenges on the tradeoff between the accuracy and feasibility of mechanical properties characterization. In this paper, we designed a sheet-like indenter configuration to quantitatively obtain the yield stress of fresh 3DPC. First, we show the typical

While extensive evidence indicates that the porous microstructure of the steel-concrete interface (SCI) is the key factor contributing to early depassivation and expedited corrosion propagation of steel rebar, there remains a lack of quantitative relationship between the SCI microstructural parameters and corrosion rate of steel, particularly under unsaturated conditions. In this work, the effects

Foam concrete encounters a fundamental challenge in balancing lightweight and high strength. Pore optimization is the key to address this problem. This study starts with rheology control to optimize the pore structure of foam concretes, thereby designing high-performance foam concrete (HPFC). X-ray computed tomography was employed to explore the relationship between rheology and pore characteristics

Rheology control is the most critical determinant of success in 3D concrete printing (3DCP), typically achieved through the hydration control of cement. However, this inevitably leads to overdesign of printed concrete featuring a low water-to-binder ratio (w/b), which is incompatible with its non-load bearing purpose and raises a series of environmental and durability problems, such as high carbon

Autogenous self-healing can close cracks in water-retaining concrete structures. However, its inconsistent efficiency in building practice indicates that the underlying processes are not fully understood. Therefore, this study characterizes reactive transport through cracked concrete and models it using PHREEQC to develop a comprehensive understanding of chemical processes promoting autogenous self-healing

In recycling and reusing construction waste, carbonation of recycled concrete fine (RCF) has been successfully applied to produce value-added products, such as silica nanoparticles, via the breaking of calcium silicate hydrate (C-S-H) structure and condensation of silicate chains. However, the intricacies of carbonation of RCF with varying calcium to silicon (C/S) ratios and their implications on the

The interfacial transition zone (ITZ), located between aggregate and cement paste, has the features of high porosity, low unhydrated cement content, and enrichment of calcium hydroxide crystals (CH) and is often regarded as the weak link in cement-based materials. The present study is devoted to investigating the influence of multiple mechanisms or factors on ITZ formation, including the wall effect

Static yield stress is crucial for concrete, especially for 3D printed concrete, as it determines whether the bottom layer can support the load of the subsequent layers or withstand any potential impulses. A better understanding of the evolution of the static yield stress and its changing mechanism is therefore needed. Under the assumption that hydrate formation follows fractal patterns, this work

This study presents a homogenization approach to understand and simulate the heterogeneous expansion of irregularly shaped aggregate induced by alkali-silica reaction (ASR). The analysis employs a cubic representative volume element (RVE) containing a single reactive aggregate with an arbitrary shape embedded in a mortar matrix. At the aggregate level, ASR expansion is characterized by applying a homogeneous

Establishing a realistic three-dimensional (3D) microstructure is a crucial step for studying microstructure development of hardened cement pastes. However, acquiring 3D microstructural images for cement often involves high costs and quality compromises. This paper proposes a generative adversarial networks-based method for generating 3D microstructures from a single two-dimensional (2D) image, capable

This study assessed 40 industrial clinkers from 16 cement plants, determining their physical, chemical, and mineralogical properties and the corresponding cements' strength development and hydration kinetics. Pearson's statistical analysis identified key factors influencing clinker and cement properties. Clinker composition ranged within 56.5–73.9% C₃S, 4.1–24.5% C₂S, 0.8–8.4% C₃A, and 7.4–13.9% C₄AF

The effects of CO2 exposure on sodium sulfate-activated blast furnace slag cement paste have been characterised by X-ray (attenuation) computed tomography revealing changes in micron-scale pore structure, and X-ray diffraction computed tomography (XRD-CT) elucidating changes in the spatial distribution of crystalline and semi-crystalline phases. Accelerated carbonation reduced ettringite volumes and

Alkali-activated Fe-rich non-ferrous metallurgical slags (AA-NFMS) emerge as a novel, sustainable cementitious binder, but durability performance is one of the crucial parameters to assess their success. This paper investigates the degradation mechanisms of AA-NFMS in 4 wt% acetic acid (AcH) solutions, commonly found in agricultural industries. The results indicated that upon AcH exposure, the amorphous

A reactive transport model was employed to investigate the influence of multiple hydrate phases during acetic acid attack on Portland cement paste. The simulation accounted for the dissolution of primary cement hydrates like Ettringite, Portlandite and C-S-H, along with the formation of silica gel products impacting diffusivity. The simulations primarily utilized independent material parameters, though

This work studies the autogenous self-healing of ultra-high performance concrete (UHPC) incorporating two ultra-fine pozzolanic materials, silica fume (USF) and ultra-fine fly ash (UFFA), under carbonation conditioning. Both ultra-fine pozzolanic materials stimulate the healing of cracks by promoting the secondary hydration of the cement matrix. USF and UFFA form healing products primarily consisting

In this study, hourly three-minute creep testing is used to elucidate the evolution of the viscoelastic behavior of cement pastes produced with ordinary Portland cement (OPC), limestone Portland cement (LPC), and limestone calcined clay cement (LC3), from 1 to 7 days after production. An innovative test evaluation protocol, accounting for shrinkage, is used to identify values of the elastic modulus

The impact of carbonation, induced at different CO2 concentrations (0.04 or 1 %), in the phase assemblages and compressive strength of Na2SO4-activated slag materials was determined. Carbonation led to Ca-bearing phases' decalcification (mainly C-(A)-S-H type gel and ettringite) forming different CaCO3 polymorphs, independent of the slag composition or carbonation conditions adopted. In specimens exposed

A general-purpose formal charge polarizable force field for cementitious systems, CementFF4, is presented. The force field includes the following species: Ca, Si, O, H, Al, Zn, OH− and H2O. The force field is a significant extension of previous force fields and is validated by comparison of structural features, elastic constants, reaction enthalpies, and vibrational density of states to experimental

Strength and toughness are destined conflicts in traditional inorganic materials. Herein, we prepared a high-performance calcium-silicate-hydrate (C-S-H) based organic-inorganic composites, with a trace of sodium alginate (about 8 wt%). A 1.9-fold increase in flexural strength and a nearly 6.8-fold enhancement for work of fracture are achieved in the composites, and importantly, the elastic modulus

Drying shrinkage of cement pastes (CPs) facilitating superficial cracking deserves primary concern when evaluating durability performance. To clarify shrinkage mechanism, the changes of mass, length and pore-scale water allocation of two mature CPs were monitored non-destructively through low-field NMR relaxometry. Experimental results indicated that, heat treatment under hot water slightly coarsens

The analysis of the impact of Recycled Concrete Aggregates (RCA) on chloride ingress is of prime importance for the development of Recycled Aggregates Concrete. A coupled chemo-hydraulic multiscale model, using the Finite Element squared (FE2) method, has been developed, validated and calibrated. The constitutive equations using intrinsic parameters derived from laboratory experiments on concrete samples

Nanosilica (NS) has the potential to enhance the performance of cement-based materials through improvements in pore structure, hydration product content, and the properties of calcium–(aluminum)–silicate–hydrate (C–(A)–S–H) gel, ultimately increasing resistance to sulfate attack. However, the underlying mechanisms of these enhancements remain incompletely understood, particularly with respect to the

Lightweight porous composites have been widely explored to improve their acoustic and thermal performances. Hempcrete can serve as thermal insulating or soundproofing material by utilising its high porosity. However, the rigorous correlation between hempcrete thermal and acoustic performance and its pore structure remains poorly understood due to its different pore types. In this study, three hempcrete

Previously, the lack of a thermodynamic database for N-(C-)A-S-H gel limited the application of thermodynamic modeling to alkali-activated fly ash (AAFA). This study pioneers thermodynamic modeling of AAFA using a recently developed thermodynamic dataset for N-(C-)A-S-H gel. The reaction products, pore solutions and reaction kinetics of AAFA pastes were experimentally determined. Based on the reaction

Micro-crystalline to crypto-crystalline quartz exists always in dolomitic limestones. When the dolomitic limestones are used as aggregates of concrete, pore solutions mainly composed of K+, Na+, Ca2+ and OH− ions may interacts simultaneously with dolomite and micro-crystalline to crypto-crystalline quartz. To understand mechanisms of alkali-silica-dolomite reactions in concrete, chemical reaction products

To understand the microstructural changes in the hardened cement paste during the drying, hardened white Portland cement pastes were D-dried or dried under 11, 33, 40, and 75% relative humidity, and then, pastes were impregnated with 2-propanol or water under vacuum. Measurement of 1H NMR relaxometry was employed for the pastes before and after impregnation, and the full-scale microstructural changes

Due to increasing interest in reducing CO2 emissions, new hydraulic binders are emerging, many of which contain significant amounts of iron and aluminum oxides. The reactivity of such binders can be activated using CaCl2. It thus appears essential to investigate mixed Al/Fe-Cl hydrates to better characterize the hydration products and hydration processes of these new hydraulic binders. AFm-Cl phases

This study aims to establish relationship between carbonation regimes and the early pozzolanic reactivity of carbonated recycled concrete powder (CRCP) by comparing the composition, structure and surface properties of the carbonation products. The surface of dry CRCP was characterized by a silica-rich layer and contains low-polymerized silica phases along with over 18 % of unstable calcium carbonate

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Understanding the interactions between calcium silicate hydrate (C-S-H) and heavy metals is vital for optimizing the use of solid waste in cementitious materials. This paper introduces an innovative approach to elucidate the immobilization mechanism of Cu2+, a representative heavy metal. The roles of Ca2+ and OH− in Cu2+ immobilization were comprehensively investigated through being treated by C-S-H

Alkali-silica reaction (ASR), a detrimental process causing volume expansion and cracking in concrete by forming hygroscopic and swellable gel-like products, has been a long-standing challenge faced by concrete structures across the world. Understanding the underlying mechanisms of formation, moisture uptake and swelling of ASR gels requires thorough characterizations, where an appropriate drying method

In this paper, basic creep mechanism of ambient cured one-part alkali activated slag-fly ash (AASF) paste is examined at the microscopic level. A special mini creep rig is constructed enabling in-situ monitoring of water redistribution over time between high- and low-density (HD, LD) gel pores within the loaded paste specimens using 1H NMR relaxometry. The results suggest that the contraction of C-(N)-A-S-H

This study investigates the influence of CO2 concentration on the carbonation process in cementitious paste, focusing on water content distribution in ordinary Portlandite cement and limestone-calcined clay cement (LC3). Employing single-sided nuclear magnetic resonance spectroscopy for water profiling, we revealed that under accelerated carbonation of 5 % and 1 %, the water content in fine pores (interlayer

Adsorption effect on particle surfaces and complexation effect with free Ca2+ mostly determine the retarding performance of organic admixtures on cement hydration. However, it is difficult to identify which effect plays a more important role in retarding hydration by experimental methods. Here, a theoretical model was developed to investigate the retarding mechanisms of sodium gluconate (SG) on hydration

The molecular-scale mechanical properties of calcium silicate hydrates are crucial to the macro performance of cementitious materials, while achieving coincidence between accuracy and efficiency in computational simulations still remains a challenge. This study utilizes a deep-learning potential, specifically developed for calcium silicate hydrates based on artificial neural network, to achieve molecular

This paper introduces three major recommendations for the assessment of the maximum packing fraction of mineral powders through compressive rheology. First, our results show that a minimum compressive stress is required for the measured solid volume fraction to tend towards a constant jamming fraction. Second, we show that the modification of the particles surface properties, especially their friction

In this paper, multi-ion transference numbers were determined throughout the chloride migration testing of low clinker cement-based materials. For this purpose, five cement pastes were studied: pure Portland paste (as a reference) and four other pastes, based on limestone filler, fly ash, slag or silica fume. The transference numbers were calculated from the concentration evolution in the three zones

Understanding the drying shrinkage of low Ca/Si ratio cement pastes is crucial for promoting the use of low-clinker ratio cementitious materials and reducing the environmental impact of cement production. We prepared well-hydrated cement paste samples with various fly ash replacement and water-to-cement ratios. The long-term drying shrinkage was measured by 1 mm-thick samples. Results showed that fly

Understanding the tensile strength and failure mechanism of rock–cement interfacial transition zone (ITZ) is of vital significance to the sealing integrity of cement sheath under downhole condition. Taking advantage of multiple techniques, i.e., digital image correlation (DIC), nano-indentation, XRD-Rietveld analysis, 29Si MAS solid NMR, and SEM-EDX, this study is devoted to investigating the impacts