Expansive minerals are extensively used to promote the self-healing performance of the cracked concrete. Nonetheless, the expansive minerals will be consumed prematurely by participating in cement hydration. In this study, two types of inorganic capsules based on magnesium oxide expansive agent were developed by the techniques of granulation and encapsulation. The superabsorbent polymer was also embedded

Precast tunnel lining segments manufactured with synthetic macro-fibers and steel fibers as the primary reinforcement were tested under flexural and edge compression loading. Since steel fibers are usually prescribed as the primary reinforcement of tunnel sections, the dosage of synthetic fibers was determined by matching their residual flexural strength. The performance of tunnel segments was verified

Air-entrained recycled concrete aggregate (AE-RCA), with strong frost resistance, cannot be effectively modified using the freeze-thaw modification that combines thermo-drying and freeze-thaw cycles. To address this issue, the modification technique was improved by introducing the pre-treatment of vacuum saturation. Subsequently, experimental investigations were conducted to validate the modified effect

The influence of the expansive site distribution of the alkali-silica reaction (ASR) on the expansion behavior under applied stresses was numerically investigated to verify the mechanical factor of expansion transfer. In the analysis, the aggregate and mortar phases were individually modelled by mesoscale discrete analysis. To reproduce expansive site distribution and time-dependent behavior, expansive

Direct ink writing of cementitious materials can be an alternative way for creating vascular self-healing concrete by intentionally incorporating hollow channels in the cementitious matrix. In this study, a 3D-printable fibre reinforced mortar was first developed. Three groups of specimens were fabricated using direct ink writing, where the two top and bottom printing layers were printed with different

Ferrochrome slag (FCS) is a by-product discharged in the smelting of ferrochrome alloys. This high-volume waste can be effectively valorized by utilizing it as aggregate in ultra-high performance concrete (UHPC), which is beneficial for resolving the environmental issue induced via its buildup and potential risk of chromium leaching. Additionally, it can also compensate for the shortage of natural

This study investigated the effects of mixture proportion on the mechanical and shrinkage behaviors of steel fiber reinforced high strength self-compacting lightweight concrete (SHSLC) mixtures incorporating bottom ash aggregates for internal curing. In this study, different types of fine aggregates, fine aggregate ratios, supplementary materials such as silica fume (SF) and colloidal nano-silica (CNS)

CaO-based expansive agent (CEA) and MgO-based expansive agent (MEA) are commonly used expansive agents to control the shrinkage of concrete. Understanding the effect of CEA and MEA on the structural build-up of cement paste is of significance to their application in 3D printing concrete. This study investigates the effect of CEA and MEA on the structural build-up process of cement paste within 120 min

Aiming to promote applications of carbonated recycled concrete fines (CRCF) as a low-carbon alternative to ordinary Portland cement (OPC), this study explored the effect of CRCF on the early hydration kinetics of OPC paste. The results show that CRCF is not only a highly active pozzolanic material but also an effective accelerator affecting the early hydration kinetics of OPC paste, thereby leading

Self-healing is one of the research hotspots in composite materials, but evaluating healing performance has always been challenging. This study proposed a novel method to distinguish between mechanically healed cracks and unhealed cracks with non-adhesion filling by utilizing in-situ X-ray computed tomography (XCT) and digital volume correlation (DVC). The method utilized DVC to calculate volumetric

This study compares experimentally obtained hardened cement paste microstructures from μCT and virtual microstructures generated by two hydration models, namely CEMHYD3D and HYMOSTRUC. Several microstructural features (phase volume fractions, connectivity, pore size distribution, and two-point correlation functions) were cross-validated among the microstructures on the basis of image analysis. In addition

Understanding cement hydration processes is crucial for achieving the desired properties in concrete. However, the nanoscale mechanism whereby calcium silicate hydrate (C–S–H) transforms, particularly regarding morphology, structure, and composition evolution, remains unclear. Here, we employed multimodal transmission electron microscopy (TEM) to investigate the hydration kinetics of alite at the single

Alkali-silica reaction (ASR)'s destructiveness is governed by the compositions and properties of ASR products, while methods of converting these hygroscopic-expansive gel-like products into innocuous phases remain unexploited. In this study, the influence of magnesium nitrate on the evolutions of phase, molecular structure, hydroscopic and mechanical properties of ASR gels with varying Mg/Si ratios

Industrial applications of carbonation such as self-healing and carbon capture and storage have been limited, due to a lack of reliable predictive models linking the chemistry of carbonation at the molecular scale to microstructure development and macroscopic properties. This work proposes a coarse-grained Kinetic Monte Carlo (KMC) approach to simulate microstructural evolution of a model cement paste

Containment wall of nuclear power plants is an example of a concrete structure enveloping a steel liner plate. In this research, the situations observed in connection with liner failures were investigated, namely the presence of a piece of wood (foreign matter) and a delamination gap between steel liner and concrete, with the purpose to study and define the corrosion mechanism of the steel liner plate

The performance of cementitious materials made with Recycled Concrete Aggregates (RCA) and exposed to sulfate-laden environments is not yet fully understood. There are few studies on this topic, and for a full description of the mechanisms of external sulfate attack (ESA), several influencing parameters should be considered. The replacement of natural aggregates by RCA modifies the physical and chemical

Microstructures of calcium silicate hydrates (C–S–H) are relevant to the mechanical properties and durability of cement-based materials. Random growth of the microstructures of C–S–H largely compromises the mechanical properties and durability. This paper proposes to utilize cellulose nanocrystals (CNCs) to modify the microstructures of C–S–H. This research investigates the effect of CNCs on the morphological

With the extensively application of electronics at information age, the dielectric property of concrete is one of the worthiest study topics for enhancing the development of smart infrastructure and enabling efficient non-destructive testing and monitoring of concrete structures. In this work, concrete samples with the water-to-cement (w/c) ratios of 0.4 and 0.5 were prepared and cured in saturated

This study investigates the efficacy of post-fire curing using carbonation with a 20% carbon dioxide concentration and a relative humidity cycle set between 40% and 90% for restoring the mechanical properties of thermally damaged high-performance concrete (HPC) specimens containing 0%–40% silica fume. The HPC specimens were exposed to temperatures of 600, 800, and 1000 °C for 1 h, and the compressive

The influences of modifier and carbonation on the phase assemblage of magnesium oxychloride cement (MOC) are little concerned in the literature. A thermodynamic modeling approach is employed to explore the influencing mechanisms of two commonly used modifiers (i.e. FeSO4 and KH2PO4) and phase assemblage of MOC under natural and accelerated carbonation. And quantitatively XRD test of the modified or

Accurate prediction of fracture in concrete depends on the characterization of real meso-structures. Micro X-ray computed tomography (CT) can fulfil this task but is still too expensive and time-consuming to repetitively generate numerical models, also with massive degrees of freedom (DOFs) that prohibit nonlinear computations. To address such problems, we develop a novel computational framework driven

This study investigates the effect of macro synthetic fiber (MSF) volume and crack widths on corrosion of the reinforcing bars and residual flexural behavior of fiber-reinforced super-workable concrete (FR-SWC) beams exposed to accelerated corrosion. FR-SWC beams prepared with 0, 0.33%, and 0.66% MSF were pre-cracked at 0.2-, 0.4-, and 0.75-mm widths before corrosion testing. The controlled crack width

5G signal transmission can be seriously blocked by cement-based materials, so it is very important to improve the electromagnetic transmission performance (ETP) of cement-based materials. Carboxylated nanocrystalline cellulose (NCC) is used to prepare Ordinary Portland cement paste with high ETP. The water-cement ratio and NCC content of the cement paste are 0.5 and 0–4% respectively. The test results

The tricalcium silicate (C3S) paste with high electromagnetic transmission performance is prepared by addition of nanocrystalline cellulose (NCC), and the enhancement mechanism of electromagnetic transmission performance is revealed. The water to cement ratio (W/C) and the contents of NCC are 0.5 and 1 wt%-4wt%, respectively. The results show that the electromagnetic transmissivity of the C3S paste

Recent advances in additive manufacturing have enabled the design and fabrication of auxetic materials with programmable geometries and tailorable properties, but ongoing challenges remain in integrating them for composite design. In this work, we exploit a composite design strategy on cementitious material units embedded with three-dimensional re-entrant (3DR) lattices fabricated by single and dual

The interaction between geopolymer binder and aggregates has a significant impact on thermal performance, which however still lacks sufficient understanding. In this study, a novel approach for designing high temperature resistant geopolymer composites is introduced. The microstructural-thermophysical properties and heat transfer pattern of the developed geopolymer composites are investigated and further

The current study investigates short-term and long-term crack-healing behaviour of mortars embedded with bacteria-based poly-lactic acid (PLA) capsules under both ideal and realistic environmental conditions. Two sets of specimens were prepared and subjected to different healing regimes, with the first set kept in a mist room for varying short durations (i.e., 1 week, 2 weeks, 3 weeks and 8 weeks)

To promote the high-temperature application of alkali-activated fly ash-slag (AAFS), it is vital to thoroughly understand the performance of AAFS at elevated temperatures. This paper presents a systematic study on the multiscale microstructural evolution in AAFS paste in terms of nanostructure, chemical composition and morphology changes characterised using 29Si nuclear magnetic resonance, X-ray diffraction

Corrosion of reinforcing bars is a dominant cause of degradation of reinforced concrete (RC) structures. Over time, expansive products of corrosion build up tensile stresses within the concrete, leading to cracks on the exterior surface and spalling of concrete cover. To extend the service life of RC structures, a reliable non-destructive inspection method is required to detect and evaluate corrosion-induced

In this study, lithium slag was utilised as a supplementary cementitious material (SCM) to develop pozzolanic activity and reduce CO2 emissions related to cement production, with a focus on comprehensive chemical tests and microstructural assessments. Lithium slag was primarily characterised through laser particle size analyser, X-ray fluorescence, X-ray diffraction, scanning transmission electron

A novel modified Rapid Iodide Migration (RIM) test method was used to determine the influence of LC2 and FA on iodide ion diffusion coefficient of seawater and sea sand concrete (SSC). A 0.1 mol/L AgNO3 solution was selected as the indicator to develop the colour of iodide in SSC, and a lowered mass fraction of NaI solution was selected to improve the RIM test. An X-Ray Fluorescence (XRF) test was

Wastewater treatment plants (WWTPs) around the world are mainly built using concrete. The continuous exposure to wastewater affects the durability of concrete structures and requires costly maintenance or replacement. Concrete production and repair represents ∼8% of the global anthropogenic CO2 emissions due to the use of cement, thus contributing to climate change. Developing a more sustainable cementitious

Although the high efficiency of coupled lithium and saturated metakaolin in alkali-silica reaction mitigation has been documented, its influence on cement hydration remains uninvestigated. In this study, saturated metakaolin with varying degrees of saturation and its combined influence with lithium on the hydration kinetics, phase evolution, and development of microstructure and molecular structures

Reactive MgO cement (RMC) has an ability to gain strength by carbonation. One of the main concerns in RMC systems is the potential corrosion of reinforcing steel in structural applications. This study evaluated the feasibility of replacing small proportions of RMC with Portland cement (PC) to promote the passivation of reinforcing steel. Reinforcing steels embedded in RMC with different proportions

The rising demand for green construction materials has led to tremendous research efforts towards the development of low-carbon cements, although their carbonation resistance is expected to be lower than that of ordinary Portland cement (OPC). This study aims to assess the carbonation resistance of various cements by thoroughly investigating the changes in the microstructure and mineralogy under accelerated

Magnesium potassium phosphate (MKP) cements maybe used in various service conditions. The long-term behavior, compressive strength and hydrates formed under different environments was investigated using diluted nitric acid, water and simplified Portland cement pore solution. The main hydrate K-struvite in MKP cements is destabilized to bobierrite if exposed to solutions with pH ≤ 7, and to brucite

In cold regions, concrete structures suffer from low temperatures, where damage will initiate due to the expansion of ice formation and accumulate with water supply to keep penetrating into the pores and cracks. Meanwhile, it is found that the mechanical properties of cementitious materials can be enhanced owing to the pores filled by ice. Therefore, it is important to evaluate the freezing process

Significant research efforts have been made recently to broaden the selection of precursors for alkali-activated binders, especially to utilize the locally available resources. This study presents the experimental investigation of utilizing sedimentary rocks rich in silica and alumina excavated during the construction of Jurong Rock Caverns in Singapore for alkali-activated binders. The precursors

In recent decades, waste production from biomass-fuelled power plants, as well as from building and civil engineering works construction and demolition, has increased considerably. The possibility of recovering this waste type as supplementary cementitious material (SCM) in manufacturing cement is a strategic tool for achieving the objective of reducing CO2 emissions by at least 55% (“Fit for 55″ by

In this study, the functionalized MWCNTs grafted with silane coupling agent are obtained by means of successive chemical modification methods. The structure and dispersity of the functionalized MWCNTs are characterized using the FT-IR, XPS and HR-TEM, respectively. Then the reaction kinetics, mineralogical phases, morphology and elemental components of modified geopolymer incorporated with the functionalized

Corrosion rate (i.e., corrosion current density), a crucial kinetic parameter for predicting and modeling service-life performance of reinforced concrete structures, can be estimated using empirical and physics-based models. However, existing corrosion rate predictive models have limited applicability and lowered accuracy to complex scenarios when the material composition and corrosion conditions are

The rusting and cracking of reinforced concrete structures cost billions of dollars around the world every year, and there is a lack of targeted repair methods. In this study, we first put forward an electrophoretic deposition repair method using a high-performance colloid solution containing water-based cationic epoxy resin. The effect of electrophoretic deposition on rust-cracked reinforced concrete

Electromagnetic field aligning steel fibre technology mainly focuses on the properties of ultra-high performance concrete (UHPC) without considering the interference of reinforcement. In this study, an electromagnetic field was used to align steel fibres in UHPC reinforced beams, which verified the feasibility of this method for reinforced structures. The results indicated that the steel fibres could

A multiscale creep model of concrete is proposed from C–S–H gel scale to mesoscale considering the effects of ITZ and aggregates with irregular-shaped aggregates. A novel averaged Eshelby tensor-based homogenization method is devised to obtain the effective creep of concrete with realistic-shaped aggregates covering from ellipsoidal-like gravels, polyhedral-like crushed stones, to arbitrary concave

A crack monitoring strategy using parallelly-arranged multiple conductive cement composites for reinforced concrete was verified through a series of experiments and simulations. First, the electrical resistances of various locations of the mortar embedding the CNT-CF/composites were measured along with changes in humidity. Then, shear and flexural cracks were generated through a bending test of the

The application of Raman spectroscopy in the study of the corrosion of steel reinforcement in concrete is critically reviewed. The Raman effects of all the possible products formed during passivation and corrosion are individually reviewed first with an attempt to identify the characteristic peaks and corresponding assignments, which could potentially be a useful reference for future application. The

Increasing the aggregate proportion usually reduce the chloride diffusivity of concrete, but may also increase the chloride diffusivity as more interfacial transition zone (ITZ) is introduced with increased surface area of aggregate. Since both packing density and surface area of aggregate varied simultaneously with its particle size distribution (PSD), effects of volume proportion and surface area

Ultra High-Performance Concrete (UHPC) is widely acknowledged for its remarkable mechanical properties, owing to its compact microstructure. The response of UHPC to impact forces plays a vital role in ensuring the safety and longevity of structures, specifically in protective buildings, high-performance pavements and offshore concrete structures. In this context, this paper reports on an experimental

This study intends to advance the poor knowledge on the ability of an ettringite-based binder to obtain autogenous self-healing and its relevant mechanism. We developed a high-performance polypropylene fiber-reinforced cementitious composite using a slag-based ettringite binder and investigated its autogenous healing property under water-saturated conditions. Cracks were created via four-point bending

The dispersion of recycled glass fiber reinforced plastic (rGFRP) fibers in cement mortars has a significant impact on both the workability and mechanical properties of the composites. In this study, the dispersity of three types of rGFRP fibers was improved in two methods: Method 1: the dispersant (Sodium Hexametaphosphate, SHMP) was directly added into the mortar, and Method 2: the rGFRP fibers were

Compared with the ordinary Portland cement extract solution (OPC solution), the passivation capability and chloride-induced corrosion behavior of carbon steel (Q235) and 316 stainless steel (316ss) in fly ash modified cement extract solution (FA solution) were intensively investigated in this study. The composition and electrochemical properties of steel passive films were studied using XPS technique

To enhance the bonding capability between recycled concrete aggregate (RCA) and paste, an innovative carbonation method was developed to modify the surface characteristic of RCA by promoting the formation of needle-like aragonite using accelerated carbonation in Mg(NO3)2 solution under an elevated temperature (75 °C). The evolution of surface microstructure, phases and reaction kinetics was investigated

Although the conventional engineered/strain-hardened cementitious composites (ECC/SHCC) have excellent static performance, their performance under the high-speed impact effect is less satisfactory. This paper develops a dynamic impact tensile testing system that can be used for various cementitious composites. The dynamic impact tensile properties of PE-SHCC with four different steel fiber incorporations

Quick Nozzle Mixing is a technique to overcome the contradictory rheological requirements of buildability and pumpability in 3D concrete printing. The challenge is to achieve a uniform mix in a short mix time. This work presents the mechanism of the mixing process in concrete and investigates the properties of mixing water containing five surfactants. The fresh and hardened properties of concretes

Measuring pore pressure build-up in concrete during heating is quite challenging due to a number of adverse factors that includes lack of instrumentation, test conditions, and interdependency of factors. This paper presents an experimental program undertaken to investigate different parameters that affect pore pressure measurements. A total of 21 specimens of varying shapes and sizes were made with

Rapid global industrial growth is causing an increase in the generation of large-scale by-products and waste materials, which can be recycled in the construction industry to decrease both the environmental impact of the sector and the impact of these waste materials, to ultimately contribute to the circular economy. In the current study, electric arc furnace stainless steel slag (EAFSS) as a potential

Despite the enhancement of amorphous silica on Ultra-High Performance Concrete (UHPC), the influence of amorphous silicas on the mechanical contribution of coarse aggregates (CA) in UHPC from the perspective of multiscale is still unclear. Herein, the mechanical contribution of CA owing to the incorporation of silica with different morphology (i.e. nano-silica and silica fume) is studied from micromechanics