The effects of chloride salts on concrete durability have been financially and logistically overwhelming. Current test methods for quantifying diffusivity of chlorides in concrete are time consuming and demanding. A comprehensive electrical resistivity model has been developed to quantify the chloride diffusion coefficient of concrete. The model employs the modified Nernst-Einstein equation along with

Corrosion monitoring of reinforcement is of great importance in evaluating the durability performance of concrete structures, especially under harsh environments. This paper presents a creative approach that combine using innovative electromagnetic monitoring apparatus (EMMA) and digital image correlation (DIC) technique in order to monitor the reinforcement corrosion inside concrete. The new-type

This study explores the development of fibre reinforced structural lightweight aggregate concrete (SLWAC) using sintered fly ash aggregate (SFA) as coarse aggregate. SFA is manufactured from fly ash, an industrial by-product, thus making SLWAC a sustainable building material. SLWAC of density 1800 kg/m3 is developed with and without the addition of synthetic polyolefin (macro and micro) fibres to achieve

The steel fibers were generally used to improve the compressive strength of hybrid fiber reinforced strain hardening cementitious composite (SHCC) due to its higher strength and modulus. It is crucial to rationally design the volume fraction of fibers to maximize the role of different fibers in hybrid fiber reinforced SHCC. In this study, a design philosophy was proposed to guide the synthesis of hybrid

The objective of this study is to clarify optimal conditions for suppressing the expansion of ASR-deteriorated concrete by pressure-injecting a lithium nitrite solution. To investigate the ASR-mitigating effect of lithium nitrite, concrete mixtures with two types of reactive aggregates were impregnated with lithium nitrite by pressurized injection at three steps of ASR. The effects of different timings

This study aims to investigate the influences of different grades of calcined clay on 3D printability, compressive strength (7 days), and hydration of limestone and calcined clay-based cementitious materials. Calcined clays that contained various amounts of metakaolin were achieved by blending low-grade calcined clay (LGCC) and high-grade calcined clay (HGCC) in three different proportions. The results

Experiments were performed to study the mechanism of corrosion of steel in carbonated concrete in cyclic wetting/drying exposure. It was found that the corrosion rate increased during wetting, followed by a decrease during drying. The increase and decrease of the corrosion rate can be explained by changes in electrochemically active steel area as a function of the moisture state of the mortar and its

With the phasing-out of coal power plants in many developed countries, a steep shortage in construction-grade fly ash – a widely used mineral admixture in concrete – seems inevitable. In this study, an eco-admixture prepared from a raw blend of municipal solid waste incineration (MSWI) residues was investigated as a possible cement replacement in concrete. The eco-admixture was synthesized at incineration

Mercury intrusion porosimetry (MIP) is a vital method for assessing the pore structure of cement-based porous materials (CBPMs), but its applicability remains to be clarified. Herein we employed X-ray computed tomography (X-CT) to trace the entrapped mercury in two hardened cement pastes (HCPs) after MIP tests to reassess the method for pore structure characterization. Four different maximum pressures

Corrosion resistance performance of rebars rolled from vanadium micro-alloyed (VMA) steel was evaluated vis-à-vis rebars rolled from steel having similar chemistry to the (VMA) steel without vanadium and subjected to thermomechanical treatment after hot rolling (TMT). Three test environments namely simulated concrete pore solution, mortars, and industrially polluted atmosphere were used to assess the

The “greening effect” refers to hardened concrete containing Granulated Blast-Furnace Slag (GBFS) that displays a vivid blue-green color after removal of formwork. This temporary coloration effect, which fades within a few days to weeks, has raised concerns about its potential impact on the environment. Three types of leaching tests were conducted to assess different potential release scenarios: a

Strain-hardening geopolymer composites (SHGC) exhibit remarkable ductility, crack control and high energy dissipation capacity when subject to quasi-static tensile loading. However, their mechanical performance under dynamic loading has not yet been explored. A comprehensive assessment of possible rate effects is required to facilitate a targeted material design for various practical applications.

Binders with large portions of carbon-intensive Portland cement replaced by supplementary cementitious materials (e.g. fly ash) are more susceptible to carbonation mainly due to their lower CO2 buffering capacity. This conclusion is usually drawn from accelerated experiments at elevated CO2 levels involving processes that seriously differ from natural carbonation. The resulting presence of H2O reactant

The research paper presents a modified mix design to develop cellular foamed concrete (CFC) using hazardous micro fine in-situ stone sludge waste in the form of marble slurry (MS), as a replacement of fine river sand (FRS) and tap water. To utilize maximum amount of MS, optimization was done through the Box-Behnken design (BBD) of response surface methodology (RSM). The effects of three effective variable

Fibers crossing sliding crack planes have a positive influence on capacity because they can transfer shear load as dowels. Such behavior was evidenced by several researches that investigated the direct shear performance of Fiber-Reinforced Concrete. However, there is limited literature on the direct shear pullout behavior of single fibers, which certainly provides a deeper understanding of the mechanisms

Artificial steel slag aggregates were prepared via carbonating the mixes of steel slag, fly ash and Portland cement, of which the microstructure, property and their impact on the performance of concrete were investigated. Calcium carbonates were the main binders in the aggregates, of which the formation yielded dense microstructures and reduced crushing values. The carbonated artificial steel slag

This study aims at investigating the possibility of using smectite clay waste, generated during the oil bleaching process as an additive for Portland cement. The smectite clay waste consists of montmorillonite, quartz, anorthite, calcium sulfate, and amorphous phase. For the regeneration of this waste, the extraction with hexane and thermal method were chosen. The results showed that the extraction

3D concrete printing has received worldwide attention while the development on new cementitious material compositions for 3D printing is inadequate. This study employed the recycled sand instead of natural sand to achieve 3D concrete printing and investigated the hardened properties of this extrusion-based material. The effect of replacement ratio of recycled sand, curing age, nozzle height and anisotropic

Alkali-silica reaction (ASR) is one of the most damaging problems with chemical alteration causing mechanical and physical changes in the concrete properties. Therefore in order to control concrete durability, a fast, non-destructive method aiming at detecting ASR is needed before an advanced stage (external visible signs) especially in field investigation. This paper focuses on the validation of the

Recent studies have shown that concrete containing Phase Change Materials (PCM) with low transition temperatures may reduce the number of freeze/thaw cycles suffered by the cementitious composite in temperate climates. Nevertheless, the positive influence of such admixtures on the frost resistance of cement-based materials has not been directly shown, nor the negative. In this study, mortars with different

Model construction is a key and indispensable step to understand the internal structure of concrete at the micro-/mesoscale level, which affects its properties in practice. In this paper, a practical and applicable method is proposed for generating the mesoscale structure of plain and fiber reinforced concretes. In this method, cell fracture algorithm was developed to obtain arbitrary-shaped aggregates

Textile reinforced concrete (TRC) composites are generally used to repair and/or reinforce civil engineering structures. In most cases, these reinforced structures are subjected to the weather conditions of the surrounding environment and issues such as thermal variation, humidity, and fire exposure. With consideration for these types of conditions, this study investigates the thermomechanical behaviour

This paper presents a review of the deterioration of concrete under seawater attack with particular interests in field exposure. The research reported in the literature has shown that salinity of seawater in different areas varies considerably but the type of ions and their proportion are similar. Because of this variation, laboratory studies should use specific artificial seawater to simulate on field

In this work, the negative impacts of calcium sulfoaluminate (CSA) cement prehydration on hydration and strength gain are investigated. CSA cement in three different states – virgin, prehydrated, and prehydrated and sieved were tested. Cement paste mixtures were made with three levels of ordinary portland cement (OPC) – 0%, 30%, and 70% (indicating the percentage of OPC in total cementitious material)

This paper investigates the free chloride profiles, diffusion parameters and chloride binding capacity of an alkali activated concrete (AACM) together with a control Portland cement (PC) concrete. Ggbs based AACM concrete specimens with different molarity of activator were exposed to a 5% NaCl solution for 540days to determine their free chloride diffusion properties. The relationships between the

This study reports the development of ultra-high performance geopolymer concrete (UHPGC) and overcoming the brittleness feature of geopolymer matrix by using different steel fibers. Four straight steel fibers with different aspect ratios and two different deformed steel fibers were investigated. Flowability, compressive strength and flexural behavior including strengths and deflection, and energy absorption

A sulfoaluminate high-performance cementitious material (SHCM) was prepared using flue gas desulfurization (FGD)-gypsum, coal gangue, limestone tailings, and aluminum ash as raw materials. The composition of the SHCM clinker, mechanics and hydration properties of the SHCM, and heavy metal leaching characteristics of the SHCM pastes were studied. The results showed that the mineral phases of the SHCM

Modified R3 testing has been used to classify four different SCMs, namely, limestone, pumice, slag, and densified silica fume. Cementitious pastes were prepared by replacing ordinary portland cement with SCMs at different replacement levels – 20%, 40%, and 60% for limestone, pumice, and slag and 5%, 10%, and 15% for silica fume. The influences of SCM replacement level on heat flow, heat release, calcium

Microstructural characteristics and properties of foamed concrete, a cellular lightweight cement paste with entrained air voids, are investigated. The complex 3D microstructures of the foamed concrete with different densities are obtained by micro-CT imaging and binarized as two-phase (pore/solid) materials by image processing. The mechanical responses of the microstructures are evaluated by simulations

In this study, the size effects on tensile properties and compressive strength of engineered cementitious composites (ECC) were investigated via experimental studies. Plane (2-D) and block (3-D) dogbone-shaped specimens were tested under uniaxial tension to study the size effect on tensile properties. Cubes and cylinders of different sizes were tested under uniaxial compression to study the size effect

Extrusion pressure-displacement tests on cementitious pastes with multiple starting materials and differing particle packing, subjected to different extrusion geometries are reported. The steady state extrusion pressure (equivalent to extrusion yield stress) and the deadzone length (static zone of material buildup at die entry) are determined from the pressure-displacement response to characterize

In this work, the effect of mineral admixture type and dosage on the rheological and mechanical behaviors of a newly developed backfilling material, cemented foam backfill (CFB), is comprehensively investigated. Fly ash (FA), ground granulated blast-furnace slag (GGBS) and quicklime are selected as mineral admixtures, while H2O2 and CaCO3 whisker are used as foaming agent and foaming stabilizer respectively

This study investigated the effect of the incorporation of the supplementary cementitious material (SCM) of hydrophobic silica on the mechanical properties and hydration behavior of ordinary Portland cement (OPC), compared to those of silica fume. Silica fume is a well-known SCM owing to its good compatibility with OPC by providing acceleration and pozzolanic reaction. This study revealed that mortars

It is anticipated that the use of fly ash in concrete will be significantly limited in the future due to recent restrictions on coal burning power plants to reduce air pollution. This paper aims to study the compatibility between some natural supplementary cementitious materials (SCMs): including perlite (PL), pumice (PM), and zeolite (ZL) with one type of superplasticizer and two types of air-entraining

In the early 80's, specific high-performance concretes were developed mainly to meet structural and durability requirements. To satisfy these requirements, it was necessary to densify the cementitious matrix by using low water-to-binder ratios, incorporating supplementary cementitious admixtures and using superplasticizer admixtures. However, the incorporation of these materials increase shrinkage

In this paper, adiabatic temperature rise test was used to evaluate the effect of the type and content of accelerator on cement hydration in shotcrete. Two kinds of accelerators, alkaline and alkali-free accelerators were used in the experiments. For each type of accelerator, two different concrete mixture were used, and the dosage of the accelerator was 3% and 7% respectively. The experimental and

Alternating ultrahigh temperature (AUHT) method for curing cement paste was established to investigate the effects of dry and steam conditions on the compressive strength of the cement paste. X-ray diffraction, thermogravimetry, scanning electron microscopy, and nitrogen adsorption were used to test the phases, chemical structure, microstructure, and pore structure of the cement paste in order to elucidate

A new probe, which does not use a confinement ring, has been developed to assess the corrosion state of reinforced concrete structures. Galvanostatic polarization is performed and the rebar corrosion potential, concrete resistivity and rebar corrosion rate are evaluated using an iterative calculation algorithm. The surface linear polarization resistance (RP,s = ΔEP/jPI) of the rebar/concrete interface

This paper explores the potential of using optical fiber Raman spectroscopy for continuously monitoring the early hydration of cement thanks to its superb capacities for characterizing wet samples and poorly-structured calcium-silicate-hydrate (C-S-H) as well as its excellent remote sensing competence. A bespoke optical fiber excitation Raman spectrometer with a 632.8 nm laser wavelength under an “optical

This paper presents comprehensive investigation on the microstructure and micromechanical properties of the hydration products in alkali-activated slag by adopting the coupled techniques of nanoindentation, optical microscopy, backscattering electron (BSE) imaging and energy dispersive X-ray spectroscopy (EDS), aiming to provide insight into the formation mechanism of the dark rim in AAS. It is found

In this study, the effect of the water film thickness (WFT) on unary, binary, and ternary mixtures containing cement, basalt powder (BP), and zeolite powder (ZP) were investigated. The correlations between the WFT and the flow parameters, rheological parameters, cohesiveness, and bleeding rate were investigated using statistical methods. The experimental results showed that the addition of ZP or BP

This study develops a slip-hardening straight steel fiber in ultra-high-performance concrete (UHPC). For this, a surface treatment using sandpaper with various grits was adopted in both parallel and perpendicular directions to the fiber axis. Surface roughness was assessed by atomic force microscopy (AFM), and its correlation with the pullout resistance was evaluated. Test results indicate that although

This paper presents the microstructural properties of KOH-activated slag pastes produced with natural seawater under different salinity levels. The seawater-mixed samples exhibit higher 91-day strength compared to the control sample produced with deionized water. Their reduced total porosity and decrease in average pore size are closely related to the strength improvement. The dense microstructure

Ductility of fiber reinforced cement-based materials is closely related to the interfacial bond of fiber/matrix, especially for the fiber with surface chemical inertness. In this study, graphene oxide (GO) was coated on polyethylene (PE) fiber to strengthen its bond to matrix. Firstly, the effect of PE fiber with and without GO coating on the microstructure and tensile properties of cement mortar was

Nanomodification of concrete has a promising potential to allow engineering concrete properties for specific applications. This study shows how nanoscale cellulose filaments (CF) can be used as a novel tool for tailoring the properties of strain-hardening cementitious composites (SHCC) incorporating high-volume ground-glass pozzolans (HVGP) towards improved strength and ductility. CF was introduced

This study investigates the effects of steel fiber and silica fume on the mechanical and fracture properties of ultra-high performance geopolymer concrete (UHPGC). Four volume fractions of steel fiber (0%, 1%, 2% and 3%) and four contents of silica fume by the mass of total binders (5%, 10%, 20% and 30%) were used. The mechanical and fracture properties evaluated include the compressive, splitting

Piezoresistivity of smart carbon nanotube/cementitious composite has been experimentally investigated, but the piezoresistive performance had been rarely studied when exposed to elevated temperatures. In this study, the physicochemical and mechanical properties, and piezoresistive behaviours of multi-walled carbon nanotube (MWCNT) reinforced smart cementitious composite were investigated under heat

Increasing the gypsum and slag contents in the blended cements containing slag is conducive to promote its green degree. The blended cement was prepared by mixing slag, gypsum and Portland clinker. Contour maps were designed to determine the optimal proportion of slag, gypsum and clinker by comprehensive considerations of strength, expansion, hydration, microstructure and crystallization stress. The

Inclusion of a blend of soda-lime glass powder and sodium hydroxide as an alternative dry activator (DA) powder in fly ash/slag-based one-part alkali-activated materials (AAMs) was investigated. The reactivity of the DA was studied and the properties of DA-based AAMs were compared with both one-part and two-part AAMs activated by solid sodium silicate (NS) and sodium hydroxide/sodium silicate solution

Field investigations were conducted to assess the corrosion status of reinforcements in the underground metro tunnels built between 1980 and 2006. The carbonation depth, half-cell potential, and concrete resistivity were measured on-site, and the chloride profile of cored specimens was analyzed in the laboratory. A theoretical analysis was conducted based on Nernst equation and Butler-Volmer equation

This paper presents the initial results of a two-phase research project for developing re-centring self-sensing cementitious composites. The focus here is on fresh, mechanical, and electrical properties of the developed cementitious composites. Shape memory alloy (SMA) fibres and carbon fibres were used in this study. The performance of composites was studied based on the slump test, four-point bending

This work studied the passivation of steel bar in cement pastes prepared with and without nano-silica by using electrochemical measurements and surface characterization methods. The results showed that the passivation of steel bar in cement paste was dominated by the chemistry of the pore solution and the evolution over time, which are closely associated with the hydration process of the cement. The

Moisture transport properties have an important part in the durability of cement-based materials, because water plays a major role in the majority of degradation mechanisms and can carry other agents that are detrimental. One of the key transport properties is the permeability, or saturated hydraulic conductivity (SHC), which is a function of porosity, pore size distribution, and pore connectivity

The risk of cracking/debonding of a cement overlay used to repair or strengthen an existing structure is still a key issue. Current bond test methods are not designed to measure the combined effect of peeling (mode I) and shear (mode II) on the interface. A few existing models propose theoretical approaches to predict that, but they were fitted on specific cases and lack in generality. In addition

Deicing salts have long been known to cause deterioration in concrete pavements. Freeze/thaw, surface scaling, and reinforcement corrosion are well documented deterioration mechanisms. However, another mechanism exists causing severe concrete damage that is much less understood. This deterioration is due to the formation of calcium oxychloride, from chemical interactions between the cementitious paste

Waste glass recycling helps mitigating the problem of shortage of landfilling space, and it is especially of great importance for cities like Hong Kong where a local glass manufacturing industry is not available. This paper presents an innovative way of using recycled glass cullet (GC) in Alkali-activated cement (AAC) based mortars. Both mono-sized and mix-sized recycled GC were used as aggregates

To improve its bonding behaviour with cementitious materials, the surface of carbon fibre (CF) yarn was modified by depositing a SiOx-coating using a plasma-enhanced, chemical vapour deposition (PECVD) process with hexamethyldisiloxane (HMDSO) as precursor material. After applying the SiOx coating, the fibre was impregnated with a fine-grained cement suspension to process mineral-impregnated carbon

In this study, aggregate pumices are used to produce new construction materials with low density. Pumices are grinded and then classified according to their maximum grain diameter, namely dmax ≤ 5 mm, dmax ≤ 10 mm and dmax ≤ 20 mm. The cement is added into each group as the binder material. The pumice ratios in the specimens are estimated to be 20, 40, 60 and 80% of the total volume. Moreover, pine

Sufficient bonding between Strain-Hardening Cementitious Composites (SHCC) and steel rebars is required to guarantee the stress transfer in structural applications. Although the bond between medium-strength SHCC and rebars has been extensively studied, the present understanding of this property for high-strength SHCC is very limited. Moreover, the previous pullout or bending test methods have some