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

Material, manufacturing process, and form are mutually dependent. In formwork-based concrete construction, the reinforcement must be positioned and fixed in the formwork, limiting material efficiency and freedom of form. In Digital Fabrication with Concrete (DFC), the formwork no longer limits the concrete forming process. Furthermore, the reinforcement no longer must be installed in advance, but can

Thousands of homes in County Donegal, Ireland, built from concrete blocks, are damaged by extensive cracks and crumbling that occurred a few years after construction. Recently, research has shown that pyrrhotite oxidation triggering internal sulfate attack (ISA) is the cause. In this study, samples from the strip foundations, the rising blocks, the outer and inner leaf of one undamaged reference home

Understanding the mechanical behaviour of natural soils as mixed with cement for stabilization is crucial for civil engineering developments. The response of cement-soil admixtures when subjected to cyclic loads is a largely unexplored topic, despite the importance of understanding fatigue in these ubiquitous construction materials. We present cyclic loading experiments on Portland cement mixed with

In this study, optical pH imaging was compared to phenolphthalein coloration and mineralogical analyses to enhance the comprehension of carbonation mechanisms in blended cements. Mortar mixes with four different binders were cured both sealed and underwater before being tested at 2 % CO2, 65 % RH for up to 91 days. With its high spatial resolution capability, pH imaging facilitated the quantification

The study of mixed Al3+/Fe3+ nitrate hydrates is gaining increasing interest with the emergence of new hydraulic binders and Supplementary Cementitious Materials (SCMs) containing significant amounts of iron and aluminum oxides that can be activated by nitrate addition. Layered AFm-NO3 hydrates containing varying proportions of trivalent Al3+ and Fe3+ cations were synthesized and characterized. The

This study introduces a novel approach for in-situ CO2 sequestration using recycled concrete fines (RCFs). The method employs heterogeneous dual‑calcium carbonate (Cc) precipitation from wet carbonation and calcium bicarbonate (Ca(HCO3)2) solution to form a Cc binder between RCFs. The results demonstrate that metastable aragonite is significantly promoted and stabilized in wet carbonation by leveraging

Structural build-up in fresh cement paste at rest is characterized by time evolutions of storage modulus and yield stress, which both increase linearly in time during the induction period of hydration, followed by an exponential evolution after entering the acceleration period. Here, we investigate structural build-up by coupling calorimetry and oscillatory shear measurements of Portland Cement at

Mobile robots for 3D printing applications are ready to transition from factory floors to building sites. Their remarkable flexibility and adaptability support a variety of deposition-based 3D printing technologies that utilise materials ranging from concrete and earth for extrusion, spraying, or shotcreting to metals for processes like Wire Arc Additive Manufacturing. Not confined to new constructions

This study describes advances in high-performance construction material development using a minimum of primary resources while enabling simultaneous CO2 sequestration capacities. Two so far unutilized Austrian steel slags were combined with metakaolin and vegetable oil to produce alkali-activated materials exhibiting high compressive and flexural strength of up to 94 MPa and 13 MPa, respectively. This

Moisture sorption and macroscopic deformation of hardened cement pastes (hcps) were studied in the first three drying–resaturation (D–R) cycles using low–field 1H nuclear magnetic resonance relaxometry. Four types of water (interlayer, gel, interhydrate and capillary) were detected in the hcps. In principle, they were sequentially removed from larger to smaller pores during drying with decreasing relative

Calcined clays, combined with limestone, exhibit significant potential as SCMs for achieving high clinker substitution levels. This is partly related to their high aluminum and silicon contents. Binary Portland cement – calcined clay (PC2) blends and ternary blends with limestone (LC3) have been examined using metakaolin (MK) as calcined clay for blends with low and high MK/clinker ratios. The hydration

Microstructural modelling that captures realistic features plays a key role in advancing our knowledge of concrete properties. This paper proposes a computer model based on the level set method to simulate the phase transformation during cement hydration. The model uses the level set function to reconstruct a realistic microstructure of the cement paste, specifically the fibrous form of C-S-H. The

Quantitative phase analysis of cementitious materials is crucial for understanding and predicting their performance. For anhydrous Portland cements, a variety of techniques based on microscopy, spectroscopy, and diffraction exist. Here, we employ two highly diverse techniques (X-ray Diffraction and Raman Imaging) to a common sample (ASTM Type I/II OPC). We find that, firstly, the two methods are highly

Fe-rich cementitious phases, such as tetracalcium aluminate (C4AF), are likely the least characterized and understood components of ordinary cements, in terms of their reactivity and early-age reactions. In this study, we provided the first in-situ measurements of C4AF's absolute dissolution rates in water and aqueous sulfate solutions (Na2SO4, MgSO4 and CaSO4) along with its early-age hydration characterization

The mechanisms responsible for the compromised or lost dispersing capability of polycarboxylate ether (PCE) superplasticizers in two-part alkali-activated slag (AAS) have been extensively studied, but limited scientific understanding is available on how PCEs function or lose their dispersing efficiency in one-part AAS systems, particularly those prepared using greener carbonate -based solid activators

This study compares, for the first time, MgO-based (MB) cement and Portland-based (PB) cement for stabilizing earth mortars. While MB and PB earth mortars reach similar strength, MB cement stabilization demonstrates superior early-age performance. Thermogravimetric analysis, X-ray diffraction, 29Si and 31P NMR spectroscopies show that the cement reacts in both systems and allow to establish the phase

Digital fabrication technologies, such as 3D concrete printing, are currently making their way into the construction industry. The primary focus in this field is often on the depositing processes, such as extrusion 3D concrete printing, where material is typically applied in horizontal planar layers. This area has seen substantial progress in recent years. However, numerous research and development

Additive Construction has increased dramatically within the United States in the last few years. Efforts to develop acceptance criteria have increased since 2020 and are being developed through integration of research efforts and early engagement with partners across academia, industry, and government. This review paper builds on the work by Bos et al. (2022) through addressing gaps identified and

Recently, the widespread use of high‑potassium limestone has led to a sharp increase in the K2O content in clinker, resulting in high‑potassium cement clinker. When mixed with water, high‑potassium cement clinker releases a significant amount of K+ ions in a short period, adversely affecting the performance of cement. Changes in the silica modulus can modify the proportion of silicate minerals and

Amorphous calcium (alumino) silicates are the main component of industrial byproducts (e.g., blast furnace slag and fly ash) and can be generated by grinding silicate minerals that are abundant in steel slag and carbonated calcium silicate binders. To promote the production of CO2-activated building material from diverse materials, this study investigated the carbonation of synthetic calcium silicate

Accelerated impressed current testing is the most common experimental method for assessing the susceptibility to corrosion-induced cracking, the most prominent challenge to the durability of reinforced concrete structures. Although it is well known that accelerated impressed current tests lead to slower propagation of cracks (with respect to corrosion penetration) than in natural conditions, which

Damping cementitious materials have been widely used in engineering structures for vibration control. However, achieving a balance between the mechanical strength and damping capacity of cementitious materials remains a challenge. Herein, we utilized an initiator (APS) to initiate the self-crosslinking reaction of PVA molecules in CS paste, then successfully introduced the viscoelastic PVA membranes

Fluid transport in cementitious matrices and materials is fundamental for many engineering and environmental applications. However, observing and measuring transport processes inside opaque porous solids, such as cement, is technically challenging. We tested the feasibility of using Positron Emission Tomography (PET) for in-situ tracking of fluid being spontaneously imbibed into cementitious matrices

The relative slow carbonation efficiency for conventional wet and dry carbonation of recycled concrete fines (RCF) limits its resource industrial utilization. In this study, an innovative mechanochemical carbonation (MC) method was developed. The carbonation kinetics, phase assemblage and microstructure evolution of RCF during the MC process were extensively examined. The results exhibited a substantial