In this study, the early age hydration kinetics of BOF slag is investigated. Isothermal calorimetry and in-situ X-ray diffraction (XRD) are used to examine the effects of K3-citrate concentration and nanosilica addition on slag reactivity. The results reveal that brownmillerite is the most reactive slag phase during the first 24 h of hydration. The kinetics of brownmillerite hydration is controlled

This paper characterises the durability of concrete produced with thermoactivated recycled cement (RC) obtained from waste cement paste or the cementitious fraction of waste concrete. The durability of concrete produced with 5–100% RC and water/binder ratios of 0.35–0.65 was assessed through capillary absorption, oxygen permeability, rapid chloride migration and carbonation resistance tests. Overall

The facile synthesis of hierarchically porous spherical geopolymer beads via pipetting and low-temperature foaming is reported here. The potassium silica solution and metakaolin-slag-based slurries were modified by amorphous fumed silica in order to regulate the SiO2–Al2O3 ratio and to form a porous structure through chemical foaming technique under alkaline conditions. The addition of fumed silica

The corrosion behaviors of partially and fully debonded steel fibers embedded in ultra-high-performance concrete (UHPC) and their impact on the pullout behavior are investigated. For this purpose, pre-loaded dog-bone samples are immersed in a 3.5% standard sodium chloride (NaCl) solution for 4, 10, and 20 weeks and then pull-out tested. The degree of corrosion on the fiber surface is determined by

Geopolymers have attracted attention as green building materials with low carbon dioxide emissions and excellent mechanical properties. Due to their hydrophilicity and porous structure, geopolymers can be infiltrated by water involving harmful ions. In this study, the effects of polydimethylsiloxane (PDMS) as an additive on the wettability, mechanical properties and microstructure of metakaolin-based

Alkali silica reaction (ASR) can significantly affect the service life of concrete. The dissolution of aggregates has a direct impact on gel formation and thus on the macroscopic expansion. The conventional expansion tests and other investigations confirmed ASR reactivity of three aggregates from different locations in Switzerland. The reactive minerals within alpine and composite aggregates were identified

The mechanical and durability properties of recycled aggregate concrete (RAC) are generally inferior to conventional concrete due to the old mortar attached to the surface of original aggregate, which induces more complicated interfacial transition zones (ITZs) in the RAC. The microbial induced carbonate precipitation (MICP) modification is a novel and environmentally-friendly method to improve the

One of the steps to achieve a rational approach to the shear strength of reinforced concrete members is to understand the force transfer mechanisms throughout the critical crack. This subject has been investigated for decades, but its full comprehension has not been achieved, especially in steel fiber reinforced concrete (SFRC). In the present work, an experimental/theoretical investigation on the

Lightweight foam concrete is a cementitious cellular solid with a series of functional properties. Its non-structural applications potentially permit a high-volume inclusion of particles (e.g., recycled fines). However, the particle inclusion tends to alter the foam morphology and diminish the mechanical performance of foam concrete. To promote the acceptance of particle inclusion while minimizing

Capsule-based self-healing of cementitious materials is a promising solution to improve the serviceability and to prolong the longevity of concrete structures. The successful use of mechanical triggering microcapsules to achieve cracks healing is still challenging and is closely dependent on the breakage of capsules upon crack formation. In this study, self-healing microcapsules were synthesized via

Extrusion-based concrete 3D printing is at its infancy and many aspects of this new technology need to be thoroughly investigated to pave the way for its widespread use in construction. Since the inherent drying shrinkage of the hardened cement paste is the source of the drying shrinkage of 3D printed concrete, the shrinkage behavior of cementitious 3D printing materials with very high cement to fine

Drying shrinkage of alkali-activated binders are recognized as one of the most important properties towards quality assurance of the binders. In this study, results of experimental studies and predictive models developed to determine the drying shrinkage of alkali - activated blast furnace-fly ash mortars are presented and discussed. Different parameters were altered in the experimental study such

Reactive MgO (rMgO) is considered a promising alternative to Portland cement (PC), because its capacity to mineralize carbon dioxide (CO2) can be used to reduce the life cycle global warming intensity (GWI) of concrete. However, the greenhouse gases (GHG) emitted during the manufacture of rMgO may outshine its environmental benefits of CO2 mineralization. The objective of this study is to compare the

This paper presents a systematic study on the feasibility of using recycled tyre polymer (RTP) fibres for mitigating the damage of concrete induced by elevated temperatures. A series of tests were conducted to investigate the effect of RTP fibres on mechanical and thermal behaviour, pore pressure build-up and microstructural evolution of concrete exposed to elevated temperatures (20, 105, 250, 400

Carbonated MgO-based Engineered Cementitious Composite (ECC) has ultrahigh tensile ductility and tight crack width control behavior. However, the expectation of improved fire-resistant has not been confirmed. This study explored the alterations to mechanical and microstructure characteristics of this material after exposure to temperatures up to 500 °C. Material mass loss, compressive strength, tensile

A significant amount of work has focused on the development of concrete mixtures for digital manufacturing (3D printing), and their rheological and mechanical properties. However, for extrusion-based layered manufacturing, it is also important to select the appropriate printing parameters that have the potential to impact the performance of 3D printed elements. Among the many such parameters, this

In this study, three types of surfactants, as anionic (mainly SDS), cationic (DTAB) and nonionic (AEO-9), were selected as the air-entraining agent (AEA). Air void size distributions of air-entrained mortars with or without fly ash were measured. The surface tension, the zeta potential of solid particles, and rheological properties were examined. The zeta potential alteration is used to characterize

The moisture transport and drying shrinkage properties of a certain type of Strain-Hardening Cement-Based Composite (SHCC) are investigated. This material is characterized by the usage of short high-modulus polymeric fibers as reinforcement of a cementitious mortar matrix with comparatively small grain sizes. The drying-induced mass loss and length change of circular cylindrical specimens with a radius

Ultra-high performance concrete (UHPC) has been accepted rapidly attributed to its superior mechanical performance and the split Hopkinson pressure bar (SHPB) is being widely utilized to evaluate the dynamic compressive properties of UHPC. Numerous studies have been performed on the dynamic behaviour of UHPC, however, a systematic summary and analysis on the dynamic compressive properties of UHPC tested

This paper presents a constitutive model for the simulation of temperature and relative humidity effects on concrete expansion due to Alkali–Silica Reaction (ASR). The model was formulated within the multiphysics framework of the Lattice Discrete Particle Model (LDPM). LDPM simulates concrete internal structure at the mesoscale defined as the length scale of coarse aggregate pieces. As such it accounts

This paper focuses on the effect of chelating crystalline admixtures (CA) on mechanical, self-healing and transport properties of engineered cementitious composite (ECC). Four ECC with varying CA contents were prepared. The effect of CA on the mechanical properties of ECC was evaluated by compressive and tensile tests. The self-healing behavior was investigated by sorptivity test and crack closure

Acid-induced deterioration reduces the service life of concrete and requires high maintenance costs. This study examined the deterioration of graphene oxide (GO)-modified cement pastes exposed to 1 M citric acid (C6H8O7) and 1 M sulfuric acid (H2SO4) environments for two weeks. Changes in the physical and chemical properties of the binder matrix were determined by the assessment of fresh and hardened

A highly efficient mixture design should have a good balance among workability, strength, durability, economic efficiency, and sustainability. Ultra-high-performance concrete (UHPC) is a relatively novel composite material with ultra-high strength, high toughness, and superior durability, although new solutions are constantly being developed. Previous mixture design methods for normal concrete and

This study investigates the high performance of feldspathic solid solution-based geopolymer composites. The results show that a feldspathic solid solution with incongruent dissolution in an alkaline medium produces a differential amount of N-A-S-H+ polysialate geopolymer, depending on the mineral nature of the raw solid precursor. In turn, the presence of both N-A-S-H and polysialate geopolymer reduced

Rate-dependent mechanical response of fly ash cenospheres polyurethane syntactic foams (CPSFs) with hierarchical cell structure was examined through dynamic compression tests. Quasi-static compression strength and specific energy absorption varied in the range of 9.5–29.5 MPa and 4.8–13.0 MJ/m3 within the density of 0.5–0.7 g/cm3. The thermal conductivity coefficient of CPSFs increased from 0.08 W/m/K

Corrosion of rebars is one of the main issues affecting the service life of Reinforced Concrete (RC) structures. It is well-known that the use of fibers enhances the mechanical behavior of RC structures at both Serviceability Limit States (SLS) and Ultimate Limit States (ULS). In the former, fibers mainly influence the cracking pattern, leading to narrower and more closely spaced cracks. The crack

This study aims to elucidate the effect of different mixing speeds on microencapsulated phase change material (mPCM) and examine the associated degradation mechanism of compressive strength of cement-paste. Experimental results showed that moderate to high mixing speed led to the damage of mPCM particles and consequently the PCM leakage. The PCM leakage was evidenced by changes in the rheological properties

The durability and functionality of concrete overlay repairs are highly dependent on the extent of cracking and crack widths, which are difficult to predict. This article presents an experimental and analytical investigation on restrained shrinkage of overlays made with rapid hardening mortar mixes reinforced with recycled fibres. The investigated parameters include cement type (calcium sulfoaluminate

In this study, the effects of limestone powder on the rheological behavior, pore solution chemistry, mechanical properties and microstructure of alkali-activated cements have been investigated. The results exhibit that, with the increasing content of limestone powder in the ternary alkali-activated system, the structural build-up of the mixture increases earlier. It was observed that flow curves of

Nowadays, concrete industry uses viscosity-modifying admixtures (VMA) for the production and placement of special construction applications such as underwater or self-consolidating concrete. VMAs can decrease the movement of water and fines, and maintain the underwater concrete's homogeneity. Self-consolidating concrete requires high stability since the material shows a high slump-flow, but high viscosity

The ASTM C311 strength activity index test is a potentially flawed test because inert materials are known to be able to pass the test. The early age of testing, low fly ash replacement levels, variable water-to-cementitious materials ratio, and low strength limits all contribute to the inability of the test to successfully distinguish inert and reactive materials. Test modifications utilizing higher

In this study, a highly flowable, rapid set crack repair grout powder (CRG) was used to facilitate mix design of 3D printing mortar. Various mortar mixtures with different amounts of CRG were evaluated for setting time, flowability, and printability. For the first time, pore/micro-structures of printed filaments and their bonds were examined in detail. The results have provided a better understanding

This investigation reports on the mechanisms of reaction, microstructure, hydration products, compressive strength and environmental impact of supersulfated cements based on pumice (SSC-PM), using 10–20%wt of quicklime (CaO) as the alkaline activator and 5–15%wt of sulfatic activators of anhydrite or hemihydrate; three different initial curing temperature (ICT) regimes were used for 24 h, of 20, 40

Pumping changes the rheological properties, workability and construction performance of fresh concrete. However, there were limited knowledges on influences of discharge rates and pumping distances on the fresh properties of concrete. In this paper, effects of various discharge rates and pipeline lengths on rheological properties of self-consolidating concrete (SCC) after pumping were studied. A total

Microbial self-healing concrete (SHC) is a biomimetic smart material with microbial carriers to repair microcracks. This paper investigates the mechanism of Cl− transport and the repair performance of SHC based on recycled coarse aggregate (RCA) as microbial carriers. To assess the repair effectiveness to hinder Cl− corrosion, it is necessary to understand the ionic interactions and mechanism that

In corroded reinforced concrete (RC) structures, there is a need to understand the degree of internal corrosion of the reinforcing bars in order to evaluate residual performance and ensure a rational maintenance regime. The authors have developed a computational approach for estimating the distribution of corrosion along the length of a reinforcing bar from the observed surface crack widths. The approach

Calcium-silicate-hydrate (C–S–H) represents a key microstructural phase that governs the mechanical properties of concrete at a large scale. Defects in the C–S–H phase are also responsible for the poor ductility and low tensile strength of concrete. Manipulating the microstructure of C–S–H can lead to new cementitious materials with improved structural performance. This paper presents an experimental

The need to improve the understanding of the properties of cement-based materials calls for the development of tools for visualizing and quantifying chemical reactions and flows of fluids within them. In this paper, we report the results of an experimental study where a sample of fractured cement-paste was subjected to injection of fluids (krypton, CO2 and water) and imaged simultaneously by X-ray

The advancement of concrete technology such as 3D concrete printing has rekindled research interest in the early-age mechanical properties of concrete. However, the non-adaptability of early-age (plastic) concrete to classical mechanical measurements causes the quest for alternative approaches. This study is a new and unique approach, using rheological methods, aimed at investigating the early development

An experimental investigation was carried out to evaluate the performance of (к)-carrageenan as a novel viscosity-modifying admixture (VMA) in cement-based materials. The effect of different dosages of (к)-carrageenan and their combinations with two different high-range water-reducer (HRWR) types on rheology, forced bleeding, hydration kinetics, and compressive strength of cement suspensions was evaluated

Water extraction method has been widely applied to determine the free chloride content in cement-based materials. This paper studies the effects of different extraction time, curing ages and w/b ratios on the obtained free chloride content of seawater cement paste with low water-binder ratio by water extraction method. An appropriate testing process of water extraction method for pore solution acquisition

Using graphite tailings (GT) to replace part of sand to prepare graphite tailings concrete (GTC) is an effective way to reduce the environmental hazards. At present, there is still unclear issues on the durability of GTC. Resistivity is an important index to characterize the durability of concrete, and the effect of influencing factors (e.g. applied voltage, measuring electrode) on the measurement

Ultra-high-performance concrete (UHPC) shows high tensile strength, compressive strength, and durability compared to normal strength concrete (NSC). However, high compactness, low permeability, and absence of capillary pores might reduce the spalling resistance of UHPC under elevated temperatures and fire conditions compared to NSC and high strength concrete (HSC). There are limited studies on the

This paper investigates the quantification of ettringite (Ca6Al2(SO4)3(OH)12.26H2O, AFt), gypsum (CaSO4.2H2O, Gy) and Friedel's salt (Ca4Al2(OH)12Cl2.4H2O, Fs) formed for binary, ternary and quaternary blended cementitious mortar mixes that were exposed to acid (H2SO4), alkali (Na2SO4) and chloride (NaCl) solutions. Quantification was carried out through a thermogravimetric analyzer by characterizing

Variability of concrete properties has strong influences on design and conformity assessment. However, variability of residual flexural strengths of steel fiber-reinforced concrete (SFRC) has yet been statistically investigated. In this study, a large number of SFRC specimens was sampled from a central mix concrete plant manufacturing precast SFRC elements for a real civil infrastructure project. Variability

The freeze-thawing (F-T) action-induced evolution of shotcrete pore-structure is the potential cause of resistance degradation of chloride ion diffusion in cold regions. To study the degradation mechanisms, a combined multiscale experimental characterization and numerical modeling study is conducted, considering the pore-structure evolution characterized with micro-computed tomography (micro-CT). The

This study examined bleeding in cement paste as affected by cellulose nanofibres prepared with varying the content of carboxyl groups that were grafted onto the fibre surface. Alongside the conventional ASTM test method, bleeding was further evaluated using a turbidity scanner. A linear correlation was obtained between the bleeding heights as found from the two techniques. The results demonstrate that

Micro-structures of fibre reinforced composites play a pivotal role in their damage, fracture and failure mechanisms. This study first carried out ex-situ micro X-ray Computed Tomography (μXCT) tests of three small ultra-high-performance fibre reinforced concrete (UHPFRC) beams under progressive three-point bending. The first two beams were continuously loaded until failure and their central regions

This paper presents a new scalar plastic damage constitutive model in tension for steel fiber reinforced concrete. It considers the coupled mechanism of matrix bridging and fiber bridging using the Helmholtz free energy. A total of 27 steel fiber reinforced concrete specimens with three concrete matrix strengths and three fiber volume fractions were subjected to three-point bending tests. The acoustic

It is a challenge to isolate the ITZ effect on the mass transport from several concurrent factors. This study designed a systematical experimental work to assess the relatively importance of ITZ to gas permeability, capillary water absorption and chloride migration, considering the effect of preconditioning regime, aggregate volume content and size. The ratio of mass transport between ITZ and bulk

In this study, superabsorbent polymers (SAPs) and two expansive additives (a MgO-based expansion agent and gypsum) were studied to possibly mitigate the shrinkage of AAS (alkali-activated slag) systems. To this end, an experimental study was carried out to evaluate the effect of SAPs and the expansive additives on the setting time, compressive strength, autogenous shrinkage, and total shrinkage of

This paper assesses the feasibility of 3D concrete printing of lightweight elements by the extrusion of hollow-core filaments. Two different filament shapes of rectangular hollow shape and U-shape were printed by using customised print nozzles. The primary challenge in hollow-core 3D printing is the extrudability and the stability of the overhang of the filament at fresh state. The stability of the

High-strength engineered cementitious composite (HS-ECC) reinforced with polyethylene (PE) fiber typically features larger crack width compared with conventional polyvinyl alcohol fiber-reinforced engineered cementitious composite (PVA-ECC), diminishing the self-healing potential of HS-ECC. This larger crack width is attributed to the high matrix fracture toughness and the weak interfacial property

This work aims to propose a novel method to treat the defects of delayed hydration and low early-age strength of cementitious composites blended with high-volume fly ash (HVFA). The influence of calcined layered double hydroxide (CLDH) on mechanical properties, hydration process and microstructure of HVFA cementitious composites have been explored. Assessed properties of HVFA cementious composites

Microbially induced corrosion (MIC) is a serious issue for sewer structures worldwide. Many studies have been carried out to develop more durable cement-based materials under the MIC attack. Due to a lack of a standard, various methods have been tried in the evaluation of resistance of different cement-based materials against MIC. A review of existing evaluation methods is needed to summarize these

Clays have emerged as potential partial replacements for cement, allowing for a reduction in global CO2 emissions without sacrificing strength. However, smectite clay minerals such as montmorillonite (MMT) have dramatic shrink and swell properties, which hampers the consistency of cement paste and generates micro cracks at the interface. In addition, MMT shows strong adsorption and intercalation of

Hybrid fiber reinforced concrete (HFRC) has been proposed to improve the mechanical properties of concrete, especially the tensile behavior and ductility. To better understand the mechanisms of such enhancements, a series of macro-scale and micro-scale tests have been performed and combined to analyze the relationships between microstructural characteristics and mechanical properties of HFRC. The X-ray

High strength engineered cementitious composites (ECC) that fracture under tensile stress present cracks with the width over 100 μm, which may not be easily repaired by autogenous healing. Herein, this study investigated the healing efficiency of high strength ECC after being immersed in bacteria-free medium which is waste medium during spore cultivation. During incubation of bacteria, concentration

Typical ECC mix design omits normal aggregates and adopts only fine micro silica sands. Few studies report the possibility of using river sands in ECC mix design. While the resulting ECC is more economical with improved time-dependent properties, a very different tensile strain-hardening behavior is also observed. The current study reveals the fundamental mechanisms by investigating the matrix cracking