Fibre-reinforced polymer (FRP) bars are important replacements for reinforcements made of ordinary steel because the former offer structural durability, electromagnetic neutrality and a high strength/weight ratio, as well as being lightweight and flexible. In the present study, six concrete columns with a diameter of 29·7 cm, a height of 1·5 m but with different percentages of steel and glass FRP bars

Structural health monitoring (SHM) of civil engineering structures has been widely developed to increase safety and to provide cost-effective maintenance programmes. Although the current approaches of SHM systems using traditional single-point sensors – such as electric strain sensors, accelerometers and global positioning system-based sensors – have appropriate measurement precision for SHM purposes

A ternary hardening-accelerating admixture for Portland cement, comprising calcium fluoroaluminate (11CaO.7Al2O3.CaF2), calcium thiocyanate (Ca(SCN)2) and triethanolamine (C6H15NO3), was studied. The cement paste was investigated using compressive strength tests, X-ray diffraction, thermogravimetric analysis, scanning electron microscopy and porous medium surface area analysis. The results showed that

This investigation aims to study the abrasion and impact resistance of fibre-reinforced concrete before and after exposure to salt scaling. Different types of steel fibre and different mixture compositions were used to improve the strength and resistance of the tested mixtures. The variables were the type of steel fibres, surface condition of steel fibres (coated and uncoated), length of steel fibres

The focus of this work was the thermal properties (thermal conductivity, thermal diffusivity, specific heat capacity and linear expansion coefficient) of steel-fibre-reinforced reactive powder concrete (RPC) at elevated temperatures (20–900°C). The thermal properties of RPC, ordinary concrete and high-strength concrete were compared and analysed. The results showed that, with an increase in temperature

Cracking is a common form of damage in reinforced-concrete (RC) beams. Cracks affect the frequency and deflection of RC beams. Although a model for the natural frequencies of RC beams with one or two flexural cracks has been proposed, a study of the effect of numerous initial flexural cracks on RC beams is still lacking. In the present study, the frequency and deflection of a 60-year-old RC box beam

In the present work, textile-reinforced concrete (TRC) specimens were produced using high-performance natural curauá unidirectional fabrics as reinforcement. Portland cement was partially replaced by pozzolanic materials to produce a matrix with low calcium hydroxide content. Composites with different numbers of layers and thicknesses were produced. Their mechanical behaviour was evaluated through

In this work, different cementitious systems were used to investigate the shrinkage of concrete under plastic and drying conditions. Emphasis was placed on Portland limestone cement (type IL) with replacement amounts of 10% of Portland cement. Comparisons were made with a cement type with low Blaine fineness (i.e. coarse ground cement). The results indicated that type IL cement has good shrinkage results

A systematic study on the chloride penetration resistance and binding capacity of cementitious materials containing varying proportions of low-calcium fly ash or blast-furnace slag is presented. The results show that a larger water/binder ratio of cementitious materials can enhance its binding capacity but reduce chloride resistance regardless of binder type. At a given water/binder ratio, the chloride-binding

Pervious concrete needs to have many pores to achieve high water permeability, but excessive porosity may cause a serious reduction in strength. Herein, it is postulated that the interconnected porosity and open porosity, which can be separately measured, do not have the same effects on the performance of pervious concrete. To evaluate how the interconnected porosity and open porosity influence permeability

Past earthquakes show that a large number of existing reinforced-concrete (RC) buildings sustain relatively substantial damage especially at the beam­­–column connections where it is mostly caused by either diagonal shear cracks due to the absence of transverse reinforcement or by bar slippage due to the insufficient bond length of the beam bottom bars. Slip of the beam longitudinal reinforcement in

The pore structure is of great concern to the mechanical properties and durability of concrete. This paper investigated the pore structures of slag-blended cement paste under steam curing using two non-destructive testing (NDT) tools: electrochemical impedance spectroscopy and ultrasonic methods. Four different pastes containing 0, 20, 50 and 70% slag were prepared. For the electrochemical impedance

In this paper, the effect of the partial substitution of cements with limestone powders (LSPs) with different replacement levels and fineness on the fracture and flexural properties of non-oil-coated polyvinyl alcohol (PVA) fibre-reinforced sulfoaluminate cement (SAC) was experimentally investigated. The properties of the matrix, including the pore structure and fracture behaviour, were evaluated by

In this paper, a precast post-tensioned (PT) concrete beam–column connection, composed of PT composite beams with partially bonded tendons, precast multi-storey columns and cast-in-place (CIP) core region, was developed as an emulative connection. Four full-scale beam–column connections, including an interior and an exterior precast connection and the corresponding CIP control specimens, were tested

In this paper, the stiffness degradation index previously proposed by the authors is used as a seismic performance index for circular concrete-filled steel tubular (CFT) columns. Four performance levels for CFT columns are defined – that is, virtually intact; minor damage; moderate damage; and severe failure. A total of 144 CFT columns are numerically analysed to obtain the stiffness degradation index

This paper presents an experimental investigation on the synergetic effect of magnesium oxide expansion additive (MEA) and superabsorbent polymer (SAP) on the long-term drying shrinkage, autogenous shrinkage, internal humidity and mechanical strength of concrete. Concrete with varying dosages of MEA (0, 4, 6, 8 and 10%) and SAP dosage (0, 0·2, 0·4 and 0·8%) was studied to assess the synergetic effect

Punching tests on continuous concrete slabs are very expensive and elaborate. As a consequence, the majority of the existing punching tests have been performed on isolated specimens representing only the hogging moment region around the considered slab–column connection. Isolated punching tests are valuable in order to analyse the punching shear behaviour systematically. Nevertheless, beneficial effects

Six half-scale, single-storey, one-bay frame specimens were tested to investigate the seismic behaviour of masonry-infilled reinforced concrete (RC) frames subjected to lateral loading. The variables investigated included the type of masonry infill and the types of openings. The crack patterns, failure modes, load–displacement hysteretic loops, stiffness degradation and energy dissipation capacity

In total, 48 cylinders were tested to measure the uniaxial compressive stress–strain relationships of geopolymer concrete composite (GPCC) with fly ash blended with ground granulated blast-furnace slag (GGBFS). Four replica specimens were fabricated for each of the 12 combinations of three parameters: ratio of GGBFS to binder (0·2, 0·3 and 0·4), concentration of sodium hydroxide (8 and 12 M) and curing

To understand the relationship between water permeability and the pore structure of cementitious materials, this paper reviews the literature on both water permeability and pore structure and the correlation between them. Although the majority of this data is for cement paste, mortar, concrete and cemented soil are also included. Based on this study, it is established that the determination coefficient

In sulfate-laden environments, salt weathering presents a serious threat to structures. Numerous explorations have focused on weathering due to partial immersion in a single-sulfate solution, but there are few studies concerning salt weathering attacks due to combined salt weathering. In this work, mortar specimens were partially immersed in a mixed solution of sodium sulfate (Na2SO4) and sodium chloride

The main purpose of this study was to investigate the fracture property of polypropylene fibre (PPF)-reinforced lightweight concrete (LWC) at high temperatures, and also the basic properties including compressive strength, mass loss and relative elastic modulus at different temperatures were investigated. The results showed that adding PPFs into LWC decreased its compressive strength at high temperatures

This research proposes a procedure to retrofit existing structures using self-centring post-tensioned precast concrete (SC-PC) frames. The procedure utilises the initial stiffness of the un-retrofitted structure and predicts the required initial stiffness of the retrofitted one using the N2 method. A modified precast beam-end shape is proposed to double the re-centring moment capacity of the retrofit

The compressive zone of concrete with a circular cross-section is simplified to an equivalent rectangular stress block with a width, height and thickness of the peak concrete strength considering the confinement ratio. The shape factors of the equivalent stress block at any concrete strain level are modelled through selected equations of the ratios of the axial load and moment sustained by compressive

One-phase models of rebar corrosion have been widely used by practising engineers to predict the volume of rust and the time to cracking of the concrete cover, but the models have only considered the deformation of concrete and not the deformation of steel or the rust layer. Neglecting the deformation of the rust layer may result in inaccurate predictions. This study therefore proposes an adjustment

In many cases today, concrete columns do not meet the requirements of current design codes due to a number of deficiencies, including low concrete strength, inadequate transverse rebar and low construction quality. This paper presents the results from an experimental study of a strapping method for retrofitting the axial performance of concrete columns. In the method explored herein, the high-strength

Due to the combined advantages of steel fibre-reinforced (SFR) concrete and self-compacting concrete (SCC), SFRSCC is considered to present good prospects for engineering applications. As SFRSCC has good flowability and does not require vibration, the casting process directly determines the final distribution and orientation of the steel fibres, which inevitably affects the mechanical properties of

Due to the high compressive strength of steel fibre-reinforced reactive powder concrete (SFR-RPC), a higher degree of prestressing is available for SFR-RPC beams. Hence, a more slender structural component can be designed, which can reduce self-weight, usable area and, potentially, costs. However, in comparison with conventional reinforced-concrete beams, there are fewer studies on post-tensioning

Coconut fibre-reinforced concrete (CFRC) is widely used in the construction of house walls, especially in rural areas, but its impact resistance has rarely been studied. This paper investigates the dynamic compressive behaviour of CFRC by conducting high-speed servo-hydraulic tests under different strain rates ranging from 0·2 to 30 s−1. To study the strain rate effects on compressive strength, failure

This study presents the estimation of various strength and toughness properties of the steel – polyester hybrid fiber reinforced concrete performed by artificial neural network techniques. The inpu...

Bugholes, considered as an aesthetical problem, generally appear on concrete surface. Such surface imperfections may accelerate the ingression process of liquids and chlorides. Chloride penetration...

ASTM C 1260 (accelerated mortar bar test (AMBT)) is the most popular and time-effective method to evaluate the alkali–silica reactivity of an aggregate. In this study, the test specimens (mortar bars) of AMBT were prepared with six aggregate groups having six different rock mineralogies (limestone, dolomite, andesite, dacite, basalt and dolomitic limestone) and three dosages of cement alkalis (0·42

When concrete is placed in harsh conditions where aggressive chemicals are present, high-performance concrete that provides the highest levels of durability and technical performance is required. At the same time, locally available construction materials must be used so that the cost of concrete production is minimised. Deserts, which generally receive less than 250 mm of precipitation each year, take

This paper aims to provide guidelines for selecting the correct type of carbon nanotube (CNT) to improve the mechanical properties of cementitious materials. Previous researchers have discussed the effect of CNT characteristics on their dispersion quality. However, the effect of these characteristics on the mechanical properties of CNT-reinforced cementitious materials is not fully understood. To clarify

In this study, hydrogen fluoride (HF) was used to generate perforated holes in cenospheres. The cavities of the cenospheres were then filled with coagulants (calcium chloride (CaCl2)) and encapsulated in polyvinyl alcohol to obtain cenosphere microcapsules. The release curve of the cenosphere microcapsules in deionised water was tested using ethylenediaminetetraacetic acid titrimetry, and the corresponding

Digital fabrication of concrete elements requires a better understanding of the rheological behavior of the cementitious material used. Fresh concrete is known to be a thixotropic material having t...

Fly ash (FA) is used as supplementary cementitious material to Ordinary Portland cement (PC) to reduce environmental impact and improve long-term properties of concrete. However, the replacement le...

This study examines the effect of different arrangements of transverse reinforcement in the jacket section on the axial performance of full-scale reinforced-concrete columns strengthened with a seismic section enlargement approach. For the jacket section with seismic details, overlapped channel-shape bars and prefabricated bar units were designed as the closed peripheral hoops, and V-ties or segmented

Although high-strength concrete (HSC) has higher compressive strength than normal-strength concrete (NSC), its application in column construction is often limited by its brittleness and limited post-peak ductility. In this preliminary study, hybrid fibre engineered cementitious composite (ECC) is proposed as a potential encasement material to confine the HSC core and to increase the column's ductility

The restrained volume expansion of expansive agents during hydration is often used to offset strains caused by the shrinkage of cement-based materials (CBMs). The hydration and expansion process of a laboratory-prepared calcium-oxide (CaO)-type expansive agent (CEA) in CBMs and modelling of the same are discussed in this paper. Based on isothermal calorimetry and thermogravimetry/differential thermal

The chloride diffusion coefficient is directly related to the property of concrete to resist the ingress of chloride ions and it is a decisive factor for the durability of reinforced concrete subjected to the chloride environment. The conventional chloride diffusion test requires considerable time to attain a steady-state chloride flow across the specimen. Therefore, the rapid chloride migration test

The bond response of deformed bars in structural concrete is a phenomenon governed to a large extent by the rib-to-concrete contact and interaction, with contact forces depending both on material p...

The random packing of aggregate particles is an important factor affecting the mechanical properties of concrete in the mesoscopic scale. In the current study, a meso-mechanical pre-treatment algor...

The use of natural hemp fabric for strengthening existing concrete columns was investigated in this work. The results presented in this paper were based on an experimental setup analysing the effic...

In order to improve the performance of wet joints in prefabricated ultra-high-performance concrete (UHPC) bridges, a comparative study is conducted to investigate the flexural behavior of the UHPC ...

To address issues related to fast setting time of high-calcium-based alkali-activated binders and low-calcium-based alkali-activated binders' need for curing at elevated temperatures, this study aimed to develop hybrid low-calcium- and high-calcium-based binders with satisfactory fresh and hardened properties. This study was divided into two main phases: (i) production of alkali-activated natural pozzolan/slag

The influences of temperature, relative humidity (RH) and carbon dioxide (CO2) concentration on concrete carbonation in a simulated environment were investigated. The carbonation depth, compressive strength and surface strain of concrete under different simulated environments were tested. The results showed that the effects of temperature, RH and carbon dioxide concentration on carbonation depth and

As the depth of mines increases, the in situ stress increases gradually, resulting in increasingly demanding requirements for the support strength of coal-mine roadways and making it more difficult to provide this support. For this reason, more effective forms of support are needed. Concrete is a typical support form, but ordinary concrete has low support strength, cracks easily and is prone to brittle

In this study the reinforcement correction factor of concrete core testing was investigated in more detail to prepare appropriate outlines for the interpretation of results in order to minimise the uncertainties involved. For this purpose, an extensive experimental programme was undertaken, considering different concrete strength levels, moisture conditions, core size, length-to-diameter ratios of

This study investigated the effect of silicate modulus (M = silicon dioxide (SiO2)/sodium oxide (Na2O) by mass) and activator content S (mass proportion of sodium oxide and silicon dioxide to groun...

The behaviour of concrete under sudden impact loads is complex. Moreover, very little is known about the impact behaviour of high-performance fibre-reinforced concretes (HPFRCs). To account for this, nanomodified deflection-hardening HPFRC mixtures incorporating coarse aggregates were produced with three ratios of fly ash to Portland cement (0·0, 0·2 and 0·4), three nanomaterials (nanosilica, nano-alumina

In order to study the size effect in concrete fracture, three-point bending tests are performed on five groups of geometrically similar concrete beams. The electronic speckle pattern interferometry (ESPI) technique is used to measure the full-field deformation of concrete beams. Crack opening displacement data, which is crucial for understanding crack initiation and the evolution mechanism, but which

In this paper, the performance degradation of reinforced-concrete (RC) columns with corroded longitudinal steel bars was experimentally investigated. Ten large-scale RC column specimens were constructed, and the longitudinal steel bars were corroded, to simulate the real severe environmental condition that concrete structures may encounter during their long-term service life, using a hybrid method

Autogenous crack healing was quantified in mortar specimens under various exposure conditions. Specimens were cracked at 28 days and then exposed to one type of environment: submersion in freshwate...

Concrete is a highly complex and heterogeneous three-phase composite composed of aggregates, matrix and the interfacial transition zone (ITZ) between them. As the weakest structure of concrete, the ITZ is often ignored due to difficulty in its modelling using the finite-element method. In this paper, concrete models with high-volume fractions of aggregates are established, in which the ITZ structure

Ultra-high-performance fibre-reinforced concrete (UHPFRC) is a relatively newly developed construction material that not only has high compressive strength (greater than 150 MPa), but also high tensile strength (10–20 MPa). The use of UHPFRC enables the design of slender structural members; hence, instability could become a major governing failure mode. However, the estimation of buckling strength

The process of determining crack extension resistance curves (KR curves) associated with the cohesive stress distribution for the complete fracture process of a three-point bending concrete beam at low temperatures from 20°C to −40°C is presented in this paper. A total of 32 concrete beams were divided into two groups, based on different ages, 28 d and 120 d. The KR curves were calculated from curves

By having the potential to remove nitrogen oxide (NOx) air pollutants generated by vehicles and other anthropogenic combustion processes, particularly in urban areas, photocatalytic concrete has attracted significant commercial interests all over the world. In contrast to typical photocatalyst applications in concrete, in which titanium dioxide (TiO2) – the most utilised photocatalyst – is dispersed

This paper investigates and compares the effect of steel fibres obtained through recycling waste tyres (known as RTSF), and a commercially available hooked steel fibre (HSF), on plastic shrinkage c ...

This paper reports an investigation into the effect of a severe chloride environment on the flexural behaviour and microstructure of concrete composites combining normal- or high-strength concrete and ultra-high-performance fibre-reinforced concrete (UHPFRC). The normal- or high-strength concrete layers were used in the compression area while the UHPFRC, with three different fibre contents (1, 1·5