Search

Innovative materials such as Engineered Cementitious Composite (ECC) with inherent crack control and corrosion resistant Glass Fibre-Reinforced Polymer (GFRP) bars are studied for implementation in joint-free bridges with link slab. The GFRP-reinforced ECC link slab is tested experimentally under static monotonic loading and structural performance is compared with its steel-reinforced counterpart. Finite element (FE) models for steel-/GFRP-reinforced link slab are developed taking into consideration of ECC and GFRP material properties and their performance validated based on experimental results. FE models are found to simulate the behaviour of link slabs reasonably well (in terms of predicting load-deformation response, maximum/peak load capacity, concrete or steel/GFRP bar strain development, concrete cracking and failure modes) as the experimental and FE predicted results/response are found to be in good agreement. FE model is then used to conduct a parametric study for the optimization of GFRP-reinforced ECC link slabs design parameters (such as GFRP/ECC modulus of elasticity, GFRP rupture strength, ECC compressive/flexural strength/maximum sand grain size and link slab reinforcement ratio) to study their influence on structural performance. GFRP-reinforced link slab shows higher load and deflection/ductility capacity compared to their steel-reinforced counterparts. Developed FE models are found to reasonably predict load capacity of ECC link slabs within 90% to 97% (for GFFRP reinforced) and 82% to 92% (for steel reinforced) of the experimental values. Both GFRP- and steel-reinforced link slabs exhibited their potential for the construction of joint-free bridges and develop FE models can be used as tools for the optimization of design variables.

Crack repair in concrete is crucial, since cracks are the main cause of decreased service life in concrete structures. An original and promising way to repair cracks is to pre-incorporate healing a...

Alkali-activated binders (AABs) are developed using a dry mixing method under ambient curing incorporating powder-form reagents/activators and industrial waste-based supplementary cementitious materials (SCMs) as precursors. The effects of binary and ternary combinations/proportions of SCMs, two types of powder-form reagents, fundamental chemical ratios (SiO2/Al2O3, Na2O/SiO2, CaO/SiO2, and Na2O/Al2O3), and incorporation of polyvinyl alcohol (PVA) fibers on fresh state and hardened characteristics of 16 AABs were investigated to assess their performance for finding suitable mix compositions. The mix composed of ternary SCM combination (25% fly-ash class C, 35% fly-ash class F, and 40% ground granulated blast furnace slag) with multi-component reagent combination (calcium hydroxide and sodium metasilicate = 1:2.5) was found to be the most optimum binder considering all properties with a 56 day compressive strength of 54 MPa. The addition of 2% v/v PVA fibers to binder compositions did not significantly impact the compressive strengths. However, it facilitated mitigating shrinkage/expansion strains through micro-confinement in both binary and ternary binders. This research bolsters the feasibility of producing ambient cured powder-based cement-free binders and fiber-reinforced, strain-hardening composites incorporating binary/ternary combinations of SCMs with desired fresh and hardened properties.

Ambient cured alkali-activated mortars (AAMs) are developed through the activation of supplementary cementitious materials (SCMs) by powder form reagents with silica sand using a novel dry-mixing method. The fresh state, rheological, compressive strength and microstructural characteristics of eight AAM mixes are comprehensively investigated. The effects of binary/ternary combinations/proportions of SCMs, different combinations/dosages of powder form reagents and the fundamental chemical ratios (SiO2/Al2O3, Na2O/SiO2, CaO/SiO2 and Na2O/Al2O3) present in the precursors and the reagents are investigated. The AAM mixes obtained compressive strengths ranging from 34 to 42.6 MPa with initial and final setting times between 122 and 458 min and 215 and 483 min, respectively. The yield stress and viscosity of the mixes decreased with the increase in the slump flow spread. All the mixes demonstrated pseudoplastic behavior. The microstructural analysis revealed the formation of more longer polymeric chains comprising Si-Al linkages in N-C-A-S-H/N-A-S-H gels for reagent one (calcium hydroxide:sodium metasilicate = 1:2.5) mixes, which resulted in a lower slump flow, higher yield stress, higher plastic viscosity and quicker setting times compared to their reagent two (calcium hydroxide:sodium sulfate = 2.5:1) counterparts.

Alkali-activated mortars (AAMs) are developed incorporating binary/ternary combinations of industrial wastes comprising of fly ash class C (FA-C), fly ash class F (FA-F) and ground granulated blast furnace slag (GGBFS) with alkaline reagents and silica sand. The use of high calcium precursors, calcium-based powder form reagents, dry mixing method, and ambient curing with performance characterization based on chemical ratios and fracture properties are some novel aspects of the study. The mechanical (dry density, compressive strength, ultrasonic pulse velocity, elastic modulus, fracture/crack tip toughness and fracture energy), durability (shrinkage/expansion and mass change in water and ambient curing conditions, water absorption and freeze-thaw resistance) and microstructural (SEM/EDS and XRD analyses) characteristics of eight AAMs are investigated. The binary (FA-C + GGBFS) mortars obtained higher compressive strengths (between 35 MPa and 42.6 MPa), dry densities (between 2032 kg/m3 and 2088 kg/m3) and ultrasonic pulse velocities (between 3240 m/s and 4049 m/s) than their ternary (FA-C + FA-F + GGBFS) counterparts. The elastic modulus and fracture toughness for mortars incorporating reagent 2 (calcium hydroxide: sodium sulphate = 2.5:1) were up to 1.7 and five times higher than those with reagent 1 (calcium hydroxide: sodium metasilicate = 1:2.5). This can be attributed to the additional formation of C-S-H with C-A-S-H/N-C-A-S-H binding phases in mortars with reagent 2. Ternary mortars exhibited comparatively lower shrinkage/expansion and initial sorptivity indices than their binary counterparts due to the lower geopolymerisation potential of fly ash class F that facilitated the reduction of matrix porosity. All mortar specimens demonstrated 100% or more relative dynamic modulus of elasticity after 60 freeze-thaw cycles, indicating the damage recovery and satisfactory durability due to probable micro-level re-arrangement of the binding phases. This study confirmed the viability of producing cement-free AAMs with satisfactory mechanical and durability characteristics.

An RC shear wall (wall1), a composite shear wall composed of a single external steel plate connected to a concrete panel (wall2), a composite shear wall constructed from two external steel plates connected to an internal concrete panel (wall3) and finally a composite shear wall fabricated with a single internal steel plate embedded within a concrete panel (wall4) are considered in this study and their behavior are assessed and compared under the effect of an in-plane cyclic load. Variation of the three functions include shear load capacity, energy absorption and shear stiffness of the walls are evaluated numerically using the ABAQUS finite element software. The performance of numerical models is validated against to the experimental results. The effects of four parameters consisting of compressive strength of concrete, yield strength of steel plate, height-to-length ratio of the wall and the thickness of the steel plate are investigated on the above-mentioned functions. Obtained results show that the wall4 has the best performance among all four types of shear walls. For instance, the energy absorption capacity of the wall4 is approximately two times greater than that of wall1 and wall2.

In this study, properties of concrete with brick aggregate as internal curing medium has been investigated under adverse curing conditions. Brick aggregates, commonly known as brick chips (BC), have high porosity and absorption capacity. Desorption tests of different sizes of BC revealed that BC could desorb about 90% of its absorbed water. It was also observed that smaller size BC had higher desorption capacity than that of larger ones. Moreover, higher internal relative humidity was observed for all internally cured (IC) samples as compared to control samples made with 100% rock aggregate particles commonly known as stone chips (SC). Internally cured samples with three different percent replacements (15%, 20% and 25%) of SC with BC were prepared and subjected to six simulated adverse curing conditions. The performance of internally cured concrete under different curing conditions was evaluated in terms of compressive strength, rapid chloride permeability test (RCPT) and linear shrinkage test. The internally cured samples exhibited higher strength and less permeability and shrinkage as compared to their control counterparts under all adverse curing conditions considered in the study. Based on the findings of the study, 20% partial replacement of SC with BC of 9.5 mm in size can be recommended as a guideline for producing internally cured concrete under adverse curing conditions.

This paper presents behaviour of normal concrete, ultrahigh-strength concrete, engineered cementitious composite, lightweight concrete, self-consolidating concrete and crumb rubber concrete under confinement. Forty-six circular, square and rectangular concrete-filled steel tube columns with varying slenderness are tested under axial compression. Failure modes, axial load–displacement responses and stress–strain characteristics are analysed as well as concrete confined strengths are determined based on experimental results and existing models. The performance of existing confined strength models is evaluated and modified to accommodate different types of high-performance concretes and column shapes. The modified model improves the prediction of confined concrete strength with a mean predicted-to-experimental ratio of 1.05 as shape and concrete type factors are introduced.

This paper investigates behavior of reinforced concrete (RC) slab–column connection additionally reinforced with punching-shear steel or carbon fiber reinforced polymer (CFRP) bars. Such connection is commonly used in RC flat slab system. However, the absence of supporting beam results in three-dimensional shear stresses with higher hogging moment acting over RC columns which may present internal inclined cracks gradually propagating toward compressive zone leading to sudden brittle punching-shear failure. This research proposes using of steel/CFRP bars intersecting the expected inclined cracks to provide better contribution to punching-shear carrying capacity and obtain ductile failure mode. Nonlinear three-dimensional finite element (FE) analysis was created and validated through simulating the behavior of experimental specimens (with or without steel/CFRP punching-shear reinforcement) tested under static loading to failure. Moreover, further validation was conducted against previous experimental work. Such FE model was employed for parametric study on three groups of slab–column connections with variable parameters: bar type (steel/CFRP), shape and position of additional punching-shear reinforcement. Slab–column connections with additional punching-shear reinforcements showed enhanced performance in terms of higher cracking load, higher pre-cracking elastic stiffness, higher ultimate deflection reflecting ductile failure mode and higher strength.

This paper presents the effect of locally available mortar sand (MS) instead of Silica Sand (SS) and high volumes of Class-F fly ash with 55% and 70% cement replacement rates on the properties of engineered cementitious composite (ECC). ECC is a mortar based composite with a strain capacity of 300–500 times higher than normal concrete by using only 2% of fiber content. The ability of ECC to achieve strain hardening behaviour with closely spaced multiple microcracks can enhance the ductility and durability of concrete structures as well as increase their service life. In this study, the performance of ECCs made with MS and SS with high volumes of fly ash (HVFA) was judged based on the heat of hydration, slump flow, flexural and compressive strengths, ultrasonic pulse velocity, linear expansion/drying shrinkage, sorptivity and frost resistance characteristics in an attempt to produce cost-effective, sustainable and greener ECC mixtures (especially with mortar sand) for different construction applications. Replacing the silica sand by mortar sand at the same HVFA content in ECC mixtures, decreased slump flow and flow velocity, did not have a significant influence on strength (compressive and flexural) or bending capacity and reduced drying shrinkage and expansion properties by about 5% and up to 30%, respectively. Overall, the more or less similar fresh state, mechanical and durability properties confirmed the viability of producing ECC mixtures with mortar sand instead of silica sand in combination with high volumes of Class-F fly ash.

This study is primarily centered towards a quantitative evaluation of the corrosion behavior of commonly used masonry chip concrete mixes as an assessor of durability performance of infrastructures. In South Asian regions like Bangladesh, the construction domain is inclined towards using masonry chips as coarse aggregate owing to its low cost and profound availability. However, reinforced concrete structures with brick aggregate impart high susceptibility towards corrosion while putting long-term sustainability at stake. This phenomenon is further prominent in the coastal areas where high saline conditions are prevalent. Meanwhile, there is no significant study available to assess the corrosion behavior of commonly used masonry chips which is relatable to the degree of durability degradation. Hence, a comprehensive study has been designed to infer the corrosion characteristics of concrete mixes made with brick aggregate in saline environment by using an accelerated corrosion technique. Corrosion proneness of different concrete mixes with a variation in water-cement ratio and mix proportion was analyzed within the scope of this study. An overall comparison of the corrosion performance of brick aggregate was also made to the similar behavior of stone aggregate to have a comparative overview of the durability performance of the commonly used aggregates in concrete mixes. Furthermore, an insightful correlation has been obtained between the corrosion potential readings and weight loss of the embedded rebar which can be used as a quantitative basis to deduce the durability of a structure. Thereby, this project suffice as an initial study to provide a clear understanding on the corrosion performance of commonly used concrete mixes and as an aid for an early in-situ evaluation of the health of infrastructures.

This paper presents the bond characteristics of sand-coated, glass-fibre-reinforced polymer bars in ultra-high-strength concrete. A total of 216 pullout specimens were tested with variable parameters: bar diameters of 15·9 and 19·1 mm; bar embedment lengths of three, five and seven times the bar diameter; standard and high bar moduli; and concrete strengths of 129, 145 and 175 MPa. The influences of these parameters on bond strength, load–slip characteristics and failure modes are described. The bond stresses predicted from various North American codes are compared with those obtained from experiments.

The high strain capacity while maintaining small crack width makes flowable fibre-reinforced engineered cementitious composites (ECCs) an ideal durable material for construction. ECCs reinforced wi...

Engineered Cementitious Composites (ECCs) are found to be better replacements for traditional concretes due to their higher damage tolerance under loading, as well as the ability to induce multiple-cracking with a smaller width and potential crack healing capability. This paper presents the development and performance of an effective self-healing concrete system made of ECC and MgO-type expansive agent (MEA) (made of lightly burnt MgO powder). New measures were implemented in examining the performance of ECC-MgO self-healing system based on accelerated autoclave test to simulate the experimental results relevant to the field conditions. Test results suggested the best calcination system to be 900 °C with 2 h of holding time using 45 µm particle size based on higher hydration activity of MEA in a powder state. Low calcium Class-F fly ash was found to be the best supplementary cementing materials (SCMs) to produce ECC-MgO system based on lower expansion effect of MgO. The high volume of fly ash (HVFA) was used to achieve very low expansion within the crack walls just to heal hairline micro-cracks in ECC-MgO self-healing system without jeopardizing the durability. Similar behavior was shown by the MgO in powder state in terms of loss of CO2 content and remaining hydration activity as well as after utilizing it in the ECC-MgO system in water and autoclave linear expansion tests coupled with scanning electron microscope (SEM) and thermogravimetric analyses (TGA). The higher flexural strength recovery of pre-cracked ECC-MgO prismatic specimens cured under accelerated autoclaved conditions compared to their pre-cracked ECC (without MgO) counterparts confirmed the self-healing capability and potential of the proposed ECC-MgO system.

There is a compelling economic incentive to develop concrete materials that can repair its own damage, increase durability and prevent structural failure. This research investigated the potential of adding two different mineral producing bacteria into two types of cementitious mortar matrix to enhance self-healing ability for autonomous crack repair. In this study, zeolite was used as a carrier material to protect bacteria in high pH environment normally exists in concrete. The spore forming ability and ureolytic activity of zeolite-immobilized bacteria were investigated in order to examine potential for producing healing compounds. The self-healing ability of bacteria incorporated normal and fiber reinforced mortars was judged based on the development of compressive strength and permeation properties of cracked specimens with age as well as micro-structural characterization of crack healing compounds using scanning electron microscopy (SEM), energy dispersive spectrometer (EDS) and X-ray diffraction.

This paper presents the performance of engineered cementitious composites (ECCs) produced with MgO utilized as expansive self-healing agent to heal micro cracks. ECCs capability to keep small crack width of less than 60 µm even under ultimate loads can stimulate the autogenous crack healing and thus, improving the mechanical properties of structural elements. Different test schemes were adopted to quantify the long-term self-healing capability of proposed ECC-MgO system (made of 5% MgO expansive agent ‘MEA’ as fly ash replacement in ECC matrix) through studying the development and recovery of strength (compressive and flexural) and Ultrasonic Pulse Velocity (UPV) of pre-loaded multiple damaged (cracked) cubic and prismatic specimens subjected to long term water and natural curing conditions. Test results indicated that preloaded cracked ECC-MgO specimens had high tendency to recover original mechanical properties of virgin (un-cracked) specimens through healing of micro-cracks. This study confirmed the self-healing capability of proposed ECC-MgO system.

This paper presents the behavior of a new form of composite walling system consisting of two skins of profiled steel sheeting and an infill of concrete subjected to in-plane impact loading. Composite wall specimens with overall dimensions of 1626 mm high by 720 mm wide were tested under impact shear loading in two phases, namely Phase I and Phase II (in addition to ones tested under in-plane monotonic shear). In Phase I, impact energy of the projectile was kept low intentionally to capture dynamic characteristics of wall. In Phase II, the impact test was performed with maximum speed of the projectile, which the impact apparatus could produce. The performance of composite walls was judged based on the development of acceleration and top displacement during impact as well as post-impact shear-displacement response, strength/stiffness, energy absorbing capacity, stress development and failure modes. The post-impact shear strength of walls was found to be not reduced (compared to control wall tested under static monotonic loading without impact) after the application of impact energy. The stiffness degradation of the wall after impact was around 8% compared to the control wall. This was an indication of better strength/stiffness retaining capacity of the walls after subjected to impact. Theoretically predicted maximum displacement at the top of the wall at impact was also found to be in good agreement with those obtained from experiments. This research confirmed the suitability of proposed profiled double skin composite wall (DSCW) to be used as impact shear resisting element in framed buildings.

This study investigates the effect of ground granulated pumice (GGP) on workability, compressive/flexural strength and abrasion/fire resistance of mortars. Mortar mixture was prepared by replacing cement with GGP at five different replacement ratios (0, 5, 10, 15 and 20%). The sand-to-binder and water-to-binder ratios of the produced mortars were 3.0 and 0.50, respectively. Compressive/flexural strength and horizontal Bohme abrasion tests were conducted on mortar specimens at 28 days. Mortar specimens were also exposed to elevated temperatures of 300, 600 and 900 $$^{\circ }\hbox {C}$$ for a duration of 1 h to measure residual compressive strength. Test results showed that the use of GGP reduced the flow/workability of fresh mortars. It was also observed that the use of 10% GGP content slightly improved strength, abrasion and fire resistance of mortars compared to control normal Portland cement mortar.

This paper presents the results of an experimental investigation on the mechanical property of different types of fiber reinforced lightweight self-consolidating concrete (FRLWSCC) with three different types of fiber: High-Density Poly Ethylene (HDPE), Crumb Rubber (CR) and Polyvinyl Alcohol (PVA). Three developed mixes were compared in terms of compressive strength, flexural strength, stress-strain development, splitting tensile capacity, ductility, energy absorption capacity and stiffness with the lightweight self-consolidating concrete (LWSCC) without any fiber. For each category of tests, 20 samples were produced and tested. The results of the performed tests showed that the addition of fibers reduced compressive strength. In case of lightweight mixes with HDPE and PVA fibers, the reduction of compressive strength was more than 15%. However, all the fibers increased the flexural strength capacity with higher deflection at failure, meanwhile all type of fibers increased the number of cracks and reduced crack width at failure stage. Additionally, the splitting tensile capacities of FRLWSCC mixes were higher than LWSCC without fiber. All the FRLWSCCs showed a higher ability to absorb more energy. All FRLWSCC samples had a higher ductility capacity and exhibited a relatively lower stiffness.

Alkali-activated binders (AABs) are developed through the activation of aluminosilicate-rich materials using alkaline reagents. The characteristics of AABs developed using a novel dry-mixing technique incorporating powder-based reagents/activators are extensively explored. A total of forty-four binder mixes are assessed in terms of their fresh and hardened state properties. The influence of mono/binary/ternary combinations of supplementary cementitious materials (SCMs)/precursors and different types/combinations/dosages of powder-based reagents on the strength and workability properties of different binder mixes are assessed to determine the optimum composition of precursors and the reagents. The binary (55% fly ash class C and 45% ground granulated blast furnace slag) and ternary (25% fly ash class C, 35% fly ash class F and 40% ground granulated blast furnace slag) binders with reagent-2 (calcium hydroxide and sodium sulfate = 2.5:1) exhibited desired workability and 28-day compressive strengths of 56 and 52 MPa, respectively. Microstructural analyses (in terms of SEM/EDS and XRD) revealed the formation of additional calcium aluminosilicate hydrate with sodium or mixed Ca/Na compounds in binary and ternary binders incorporating reagent-2, resulting in higher compressive strength. This research confirms the potential of producing powder-based cement-free green AABs incorporating binary/ternary combinations of SCMs having the desired fresh and hardened state properties under ambient curing conditions.

Discovering new cement based materials characterised with self-healing capability is essential for sustainable infrastructure with longer service life. Engineered cementitious composite (ECC) with high potential of micro-crack healing can enhance ductility and durability of concrete structures. MgO-type expansive agent (MEA) having low water demand and with the ability of densification of concrete microstructure was utilized in this research to develop ECC-MgO self-healing system. The effect of dosages of MEA and fly ash of different types as cement replacements was investigated based on lower expansion characteristics of ECC-MgO bar specimens through both water and autoclave linear expansion tests. The performance of ECC-MgO self-healing system was examined based on compressive strength recovery of pre-cracked cubic specimens and matrix micro-structural densification through Scanning Electron Microscope (SEM). Test results indicated that 5% lightly burnt MgO in combination with high volume of Class-F fly ash with 55% cement replacement should be used to design ECC-MgO self-healing system just to heal micro-cracks without affecting the durability. The higher compressive strength of 50% and 80% pre-cracked ECC-MgO cubic specimens cured under accelerated autoclaved conditions compared to ECC-control (without MEA) confirmed the self-healing capability and potential of the proposed ECC-MgO system.

This paper presents the finite element (FE) modeling of a new form of composite walling system consisting of two skins of profiled steel sheeting and an infill of concrete subjected to in-plane impact loading. Composite wall specimen tested under impact shear loading in two phases, namely Phase I and Phase II was used to develop the FE model. In Phase I, the impact test was performed repeatedly keeping the impact energy of the projectile low intentionally to capture dynamic characteristics of the wall. In Phase II, the impact test was performed once with high impact energy (using maximum projectile speed the apparatus could produce). The developed FE model was used to simulate acceleration/displacement at the top of the wall during impact, impact energy dissipation, fundamental period, stress-strain development/concentration, shear strain/rate evolution, impact duration and bounce back impact time. The FE model predicted values/responses were found to be in good agreement with those obtained from experiments. Extensive parametric studies were conducted to study the influence of varying geometric, material and sheet-concrete interface parameters governing the composite wall performance under impact loading using the developed FE model.

This paper describes the development of regression and artificial neural network (ANN) models to determine the 28-day compressive and tensile strength of engineered cementitious composite (ECC) based on the mix design parameters. One hundred eighty ECC mixtures having variable mix designs were obtained from pervious experiments. Factors influencing the strengths were examined to determine the appropriate parameters for the ANN models. The optimized input parameters using training and development of ANN models were used to formulate the regression models. The ANN and regression models were tested with new sets of data for performance validation. Based on the good agreement and other statistical performance parameters, optimized ANN and regression models capable of predicting the strengths of ECC mixtures (using arbitrary mix design parameters) were developed and suggested for practical applications. ANN and regression models demonstrated excellent predictive ability showing predicted experimental strength ratio ranging between 0.95 and 1.00.

This paper presents an approach for the prediction of the shear strength of steel fiber-reinforced concrete (SFRC) beams using artificial neural network (ANN) model developed based on existing experimental results. Experimental database containing 173 SFRC beams without stirrups (having concrete compressive strength ranging from 20.6 to 175 MPa, classified as medium-strength, high-strength and ultra-high-strength concrete beams) and steel fiber of various shapes (hooked, crimped and straight/plain) is used to develop an ANN model. The influence of various factors affecting the shear strength of SFRC beams is also analyzed based on experimental data. The developed ANN model is validated and tested with additional data from 36 experimental beams. The shear strengths predicted based on ANN model are found to be in good agreement with the experimental values. The results show that ANN model has strong potential as a feasible design tool for predicting the shear strength of SFRC beams without transverse reinforcement/stirrups within the range of input parameters considered in this study. The developed ANN model is also found to be more accurate in predicting the shear strength compared with existing empirical equations especially for high- to ultra-high-strength SFRC beams.

The effect of the combination of fly ash and silica fume on the water resistance of Magnesium–Potassium Phosphate Cement (MKPC) was investigated, and the improvement mechanism was discussed based on the micro-analysis of XRD, FSEM and pore structure. The results indicate that, the physical effect of the combination of fly ash and silica fume on MKPC is dominated compared with the chemical effect because of the optimization of pore structure. The combination of fly ash and silica fume leads to higher density and later-age compressive strength of MKPCs compared to those without fly ash and silica fume under air curing and water curing, respectively. The strength retention ratios (namely water resistance) of MKPCs with the combination of fly ash and silica fume at 56 days are found to be significantly higher than those without fly ash and silica fume.

This paper presents the behaviour of a composite walling system consisting of two skins of profiled steel sheeting and an infill of concrete under in-plane cyclic shear loading. Double skin composite wall (DSCW) specimens with overall wall dimensions of 1626 mm high by 720 mm wide were tested. Steel sheet–concrete connections were provided by intermediate fasteners along the height and width of the wall to generate composite action. Two types of concrete namely self-consolidating concrete (SCC) and highly ductile engineered cementitious composite (ECC) as well as cold formed profiled steel sheet having same geometry but with two different yield strengths were incorporated to investigate their influence on the composite wall behaviour. The benefit of using mild over high strength steel was demonstrated through more ductile failure. Overall, ECC wall showed better performance showing lower stiffness degradation and higher displacement ductility as well as higher energy ductility (based on hysteretic loop) compared to its SCC counterpart.

Glass Fibre Reinforced Polymer (GFRP) bars have been used in the Province of Ontario as top layer of bridge deck reinforcement near surfaces exposed to de-icing chemicals. The intent of replacing deck reinforcements with GFRP is to mitigate negative effects of conventional steel rebar corrosion. Furthermore, the development of Engineered Cementitious Composite (ECC) with inherent crack width control and strain-hardening tensile behaviour for link slab application provides design engineers with a new effective way to construct joint-free bridge decks with improved durability. This paper presents experimental investigation of ECC-link slabs reinforced with sand-coated GFRP bars. The link slab specimens were subjected to variable mean fatigue stress levels of up to 55% load capacity and fatigue cycles of up to 1 million, followed by post-fatigue monotonic loading to failure. Link slab load–deflection, stiffness degradation, end rotation, GFRP and ECC strains, crack development, failure modes, energy absorbing capacity, and ductility were determined. Results were then compared with companion steel-reinforced ECC link slabs in the literature to quantify benefits of using GFRP bars. Experimental results showed that GFRP-reinforced link slabs failure by concrete crushing due to high rupture strength of GFRP, whereas steel-reinforced link slabs failed by rebar yielding. Besides exhibiting improved overall strength, the GFRP reinforced ECC link slabs showed greater post-fatigue residual rotational capacity, lower rate of stiffness degradation, enhanced post-fatigue retention of energy absorbing capacity.

In this study, effect of Engineered Cementitious Composite (ECC) covering and wrapping on corrosion resistance and structural performance of un-corroded and corroded shear beams made of self-consolidating concrete (SCC) and light weight SCC (LWSCC) has been extensively investigated. An accelerated corrosion test on beams has been performed to reach the required high degrees of corrosion (30–40% of rebar mass loss). Both corrosion and structural performance of corroded beams has been assessed and analysed. The structural performance of un-corroded and corroded beams has also been compared. The corrosion performance has been evaluated in terms of current flow, half cell potential, actual rebar mass loss, reduction in diameter etc. The structural performance has been assessed and compared in terms of load–deflection behaviour, 1st flexure/diagonal cracking load, ultimate failure load, post cracking shear resistance, ductility and energy absorption capacity, failure load and failure modes. Composite beams with ECC covering exhibited superior corrosion resistance and post-corrosion structural performance as compared to full depth SCC or LWSCC counterparts. The performance of ECC wrapped composite beams has been found to be better than those with covering. Overall, ECC can be used as covering or wrapping in conventional SCC/LWSCC beams to enhance their corrosion resistance performance significantly.

Lightweight self-compacting concrete (LWSCC) is gaining popularity since it inherits the best properties of both the lightweight concrete (LWC) and SCC. Addition of fibers to LWSCC can further enhance its performance by improving ductility, crack bridging and energy absorption capacity. However, fiber reinforced LWSCC (FRLWSCC) could have durability issues due to its relative high permeability resulting from porous lightweight aggregates (LWA). Hence, proper investigation on durability performance of FRLWSCC is essential for its long term sustainable application. Despite such importance, no significant research findings are available in literature on durability of FRLWSCC. In this study, the durability of FRLWSCC beams were investigated through accelerated corrosion testing. Both corrosion resistance and structural performance of FRLWSCC beams were evaluated. The structural response of un-corroded beams was also assessed and compared with their corroded counterparts. The FRLWSCC was prepared using three types of fibers; i.e., Polyvinyl Alcohol (PVA), Crumb Rubber (CR) and High Density Poly Ethylene (HDPE) fibers. The LWSCC-HDPE beam exhibited superior corrosion resistance as compared to LWSCC-PVA and LWSCC-CR beams. The LWSCC-HDPE beam experienced a lesser amount of mass loss of reinforcement, fewer cracks and less spalling. Moreover, it sustained the maximum residual peak load and showed higher post-cracking shear resistance.

Shear performances of hybrid composite beams, a combination of two different layers of self-consolidating concrete (SCC) and engineered cementitious composites (ECC) were investigated. Composite beams were made with two different ECC to SCC depth ratios. Full depth beams, consisting of a single layer of either SCC or ECC, were also made and tested to compare their performance with respect to that of hybrid composite beams. Both full depth and composite beams were made with and without shear reinforcement. The performance of shear beams was evaluated in terms of load-deflection response, first diagonal crack load, post-cracking shear resistance, energy absorption, and ductility index. Compared to the full depth SCC and full depth ECC beams, non-shear reinforced hybrid composite beams showed higher ductility and energy absorption capacity which indicates suitability of hybrid composite to be used in earthquake resisting elements. Hybrid composite beams also showed higher number of cracks with lower crack width. Code based equations and other design specifications were found to be conservative in predicting shear strength of hybrid composite beams. However, the theoretical capacity was found to be higher than that of experimental shear resistance in case of full depth ECC beams.

This study evaluated the self-healing capability of engineered cementitious composite (ECC) produced with 5% MgO expansive agent (MEA) compared with standard ECC counterparts. The efficienc...

The use of brick aggregates is very common in Bangladesh and nearby regions as artificial aggregate replacing natural stone. To ensure sustainable construction, finding a way to enhance its durability is extremely necessary. Microbiologically Induced Calcite Precipitation (MICP) using indigenous urease positive bacteria collected from soil showed promising results in initial research, hence further investigation has been carried out for comprehensive understanding on the effectiveness of this method. Two incubation periods of 24 hours and 48 hours were considered for bacterial culture. Absorptiometric method was used to examine population growth of bacteria due to varying incubation period. Both Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS) were used to identify the presence of CaCO3 due to bio-treatment. In addition to Rapid Migration Test (RMT), Rapid Chloride Penetration Test (RCPT) was conducted to evaluate reduction of concrete permeability due to application of treated brick aggregate. It has been found that 48 hours incubation was more effective than 24 hours incubation. The longer incubation resulted in almost twofold reduction in aggregate absorption test. Compressive Strength, RCPT and RMT of brick aggregate concrete resulting from 48 hours incubation showed 14%, 27% and 43% improvement over untreated brick concrete, respectively. Keywords: Brick aggregates, Durability, Incubation, Bacteria, MICP

Infrastructures which are constructed with inadequate quality control and design requirements or are later being subjected to different usage away from its intended purpose are vulnerable to premature structural failure. A proper detailed engineering assessment (DEA) becomes immensely important when a structure falls in this hazard category in order to determine possible modes of retrofitting. Evaluation of in-situ concrete strength through drilling cores is considered as a relatively precise and reliable mean of obtaining material property for DEA. However, the negative impact of extracting cores on structural components has seldom been addressed in previous studies, thereby causing concerns for engineers. The effect is more prominent for low-strength structures which are usually the case for vulnerable structures requiring assessment. Hence, a study has been undertaken to obtain a quantitative evaluation of parameters affecting the capacity of columns subjected to core extraction. Several parameters, such as column size, compressive strength, lateral tie spacing, core dimension and location have been considered within the study. Finite element models, being validated by comparison with capacities of lab-scale core drilled columns, have been used to analyse the effect of these parameters on column strength. The obtained significant influence of each parameter on column performance has been utilized in developing quantitative generalized graphical guidelines. The graphical guidelines will aid practicing engineers in selecting specific core sizes coherent with other structural parameters obtained from drawings or site visit while abiding by the determined safety limit.

High-volume fly ash (HVFA) Engineered Cementitious Composites (ECC) show reduced strength and physical properties, especially at early curing ages. The goal of this study was to improve their strength characteristics by incorporating recycled glass powder (RGP) for enhanced material sustainability. Composites containing 15, 30, 45 and 60% RGP as a replacement for FA, with FA to cement ratio of 2.2, were studied in HVFA-ECC. Standard ECC mixtures with FA to Portland cement (FA/PC) ratio of 1.2, and HVFA-ECC with FA/C ratio of 2.2 without RGP were also produced as control mixtures. The experimental results confirmed that incorporating RGP into HVFA-ECC significantly improves compressive and flexural strengths, chloride ion resistance and electrical resistivity, and results in a comparable ductility to standard ECC, based on FA to cement ratio of 1.2. Furthermore, self-healing of HVFA-ECC was accelerated and final recovery rate of strength and physical properties improved. Microstructural analysis showed high portlandite consumption and the formation of low Ca/Si ratio in new C-S-H structures near C-Na-Al-S-H as the main outcome of the binary admixture in ECC.

This paper presents a study on the bond characteristics of glass fiber reinforced polymer (GFRP) bars in engineered cementitious composite (ECC). Ninety beam specimens having variable parameters namely bar diameter, GFRP bar types (standard low modulus ‘LM’ and high modulus ‘HM’), two concrete types (ECC and normal concrete ‘NC’) and embedded length (5, 7 and 10 times bar diameter) were tested as per RILEM specifications. Bond stress–slip characteristics and failure modes of specimens as well as influence of variable parameters on bond strength are described. The performance of various Codes and other existing equations in predicting bond strength of both low/high modulus GFRP bars embedded in ECC compared to NC is described based on experimental results. The bond strength decreased with the increase of embedment length—maximum bond strength reduction of 36% was observed. For both ECC and NC, bond strength reduced with the increase of bar size and ECC produced maximum 1.6 times higher bond strength compared to NC. Code based and other existing equations were found conservative in predicting bond strength of GFRP bars embedded in ECC.

This paper presents the development of lightweight self-consolidating concrete (LWSCC) using three types of lightweight aggregates, namely furnace slag, expanded clay, and expanded shale. Fresh properties of LWSCCs were evaluated by slump flow/J-ring flow diameter, V-funnel flow time, J-ring height difference, L-box ratio, filling capacity, and sieve segregation. Besides fresh/28-day air/oven dry unit weights, the mechanical properties such as 7-, 28-, and 91-day compressive/flexural/tensile strength and bond strength were also evaluated. The flowability and workability improved and the segregation resistance increased with the increase in packing density of aggregates. The quality, size, and volume of coarse aggregate affected the flexural strength while quality of interfacial transition zone and paste-aggregate bonding affected the split tensile strength. Bond strength was affected by the fresh properties, paste quality, compressive strength, and aggregate type. Correlations between strength and bond pr...

This paper presents the influence of silica sand, local crushed sand and different supplementary cementing materials (SCMs) to Portland cement (C) ratio (SCM/C) on the flexural fatigue performance of engineered cementitious composites (ECCs). ECC is a micromechanically-based designed high-performance polymer fiber reinforced concrete with high ductility which exhibits strain-hardening and micro-cracking behavior in tension and flexure. The relative high cost remains an obstacle for wider commercial use of ECC. The replacement of cement by SCMs, and the use of local sand aggregates can lower cost and enhance greenness of the ECC. The main variables of this study were: type and size of aggregates (local crushed or standard silica sand), type of SCMs (fly ash “FA” or slag), SCM/cement ratio of 1.2 or 2.2, three fatigue stress levels and number of fatigue cycles up to 1 million. The study showed that ECC mixtures produced with crushed sand (with high volume of fly ash and slag) exhibited strain hardening behavior (under static loading) with deformation capacities comparable with those made with silica sand. Class F-fly ash combined with crushed sand was the best choice (compared to class CI fly ash and slag) in order to enhance the ECC ductility with slag–ECC mixtures producing lowest deflection capacity. FA–ECC mixtures with silica sand developed more damage under fatigue loading due to higher deflection evolution than FA–ECC mixtures with crushed sand.

This paper presents the results of experimental and theoretical investigations on a novel form of pierced double skin composite wall (DSCW) system consisting of two skins of profiled steel sheeting with an in-fill of concrete. Nineteen composite walls are tested to failure under axial loading. The test variables include: types of profiled steel sheeting, types of load transfer device, size/orientation of opening/holes, wall height and types of strength enhancement devices around holes. The effects of each of these variables on axial load–deformation response, axial strength, steel–sheet concrete interaction, failure modes (including concrete core cracking and steel sheet buckling) and stress–strain development are critically evaluated. Strengthening of hole boundaries is found to be essential in enhancing the axial strength of the walls. The performance of strength enhancement devices installed in the walls is found satisfactory based on axial strength–deformation characteristics and failure modes of walls. Theoretical model for the prediction of axial strength of both pierced and non-pierced composite walls is developed taking into consideration the reduction of concrete capacity due to profiling and buckling of steel sheeting. The performance of the model is validated through comparisons with experimental results.