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Compressive strength, abrasion resistance and energy absorption capacity of rubberized concretes with and without slag
(Springer, 2011) Ozbay, Erdogan; Lachemi, Mohamed; Sevim, Umur Korkut
It has been estimated that around one billion tires are withdrawn from use in the world every year. Therefore, the development of new techniques for recycling waste tires is necessary. A number of innovative solutions that meet the challenge of the tire disposal problem involve using waste as an additive to cement-based materials. In this study, an experimental program was carried out to determine the compressive strength, abrasion resistance, and energy absorption capacity of rubberized concretes with and without ground granulated blast furnace slag (GGBFS). For this purpose, a water-binder ratio (0.4), four designated levels of crumb rubber (CR) contents (0, 5, 15 and 25% by fine aggregate volume), and three levels of GGBFS content (0, 20, and 40%) were considered as experimental parameters. In total, 12 concrete mixtures were cast and tested for compressive strength, abrasion resistance, and energy absorption capacity. Test results indicate that using CR aggregate decreases compressive strength and abrasion resistance of the concretes, but increases energy absorption capacity significantly.
Cost optimization of high strength concretes by soft computing techniques
(Techno-Press, 2010) Ozbay, Erdogan; Oztas, Ahmet; Baykasoglu, Adil
In this study 72 different high strength concrete (HSC) mixes were produced according to the Taguchi design of experiment method. The specimens were divided into four groups based on the range of their compressive strengths 40-60, 60-80, 80-100 and 100-125 MPa. Each group included 18 different concrete mixes. The slump and air-content values of each mix were measured at the production time. The compressive strength, splitting tensile strength and water absorption properties were obtained at 28 days. Using this data the Genetic Programming technique was used to construct models to predict mechanical properties of HSC based on its constituients. These models, together with the cost data, were then used with a Genetic Algorithm to obtain an HSC mix that has minimum cost and at the same time meets all the strength and workability requirements. The paper describes details of the experimental results, model development, and optimization results.
Dual effectiveness of freezing-thawing and sulfate attack on high-volume slag-incorporated ECC
(Elsevier Sci Ltd, 2013) Ozbay, Erdogan; Karahan, Okan; Lachemi, Mohamed; Hossain, Khandaker M. A.; Atis, Cengiz Duran
This study investigated the dual effect of freeze-thaw cycles with sodium sulfate solution on the performance of non-air-entrained Engineering Cementitious Composites (ECCs) with high volumes of slag. ECC specimens containing three different levels of slag content as a replacement for cement (55%, 69% and 81% by weight of total cementitious material) were exposed to aggressive sodium sulfate solution under freezing-thawing cycles. The load-deflection response associated with ultimate mid-span deflection and flexural strength/stiffness was determined, along with crack development behavior. For comparison purposes, the freezing-thawing resistance (in water) of control ECC specimens was also evaluated. Modified point count method air-void parameters, compressive strength, porosity, water absorption and sorptivity tests were also conducted on the virgin ECC specimens (those not exposed to freezing-thawing cycles in water or aggressive sodium sulfate solution). The test results for the virgin specimens revealed that increased slag content (S/PC) improved the ductility, hardened air content, water absorption, porosity and sorptivity of ECC, while marginally decreasing the compressive and flexural strengths. Freeze-thaw cycles in water or sodium sulfate solution showed that the ductility of ECC specimens decreased remarkably, irrespective of slag content and applied freezing-thawing process. Reduction in mass loss was at minimal levels and no significant behavior change was monitored between the specimens undergoing freeze-thaw cycling in water and the aggressive sodium sulfate solution. Moreover, the decrease in flexural stiffness was more evident than the reduction of the flexural strength for all ECC mixtures. Crown Copyright (c) 2012 Published by Elsevier Ltd. All rights reserved.
Effect of Fly Ash and PVA Fiber on Microstructural Damage and Residual Properties of Engineered Cementitious Composites Exposed to High Temperatures
(Asce-Amer Soc Civil Engineers, 2011) Sahmaran, Mustafa; Ozbay, Erdogan; Yucel, Hasan E.; Lachemi, Mohamed; Li, Victor C.
This paper discusses the influence of high volumes of fly ash and micro polyvinyl alcohol (PVA) fibers on the fire resistance and microstructure of engineered cementitious composites (ECC). Composites containing two different contents of fly ash as a replacement for cement (55 and 70% by weight of total cementitious materials) are examined. To determine the effects of microfibers and ultrahigh ductility of ECC, ECC matrix mixtures of similar composition except PVA fiber are also produced and tested for the fire resistance. The mixtures are exposed to temperatures up to 800 degrees C for one hour. Fire resistances of the mixtures are then quantified in terms of the residual mechanical properties (strength, stress-strain curve, deflection, and stiffness) and mass loss. The role of PVA fibers and fly ash is discussed through the analysis of microstructure and fiber-matrix interactions as a function of heat treatment. The microstructural characterization is examined before and after exposure to fire deterioration by using scanning electron microscopy and the pore size distribution is obtained by mercury intrusion porosimetry. Results indicate that adding micro PVA fiber to the ECC matrix substantially improves the fire resistance and eliminates the explosive spalling behaviors of the ECC matrix. Fire resistance of ECC mixtures is further improved with the increase of fly ash content. DOI: 10.1061/(ASCE)MT.1943-5533.0000335. (C) 2011 American Society of Civil Engineers.
Effect of kaolin waste content on the properties of normal-weight concretes
(Elsevier Sci Ltd, 2015) Lotfy, Abdurrahmaan; Karahan, Okan; Ozbay, Erdogan; Hossain, Khandaker M. A.; Lachemi, Mohamed
This paper presents the mechanical, transport and drying shrinkage properties of normal-weight kaoline waste (MW) incorporated concretes. Six different concrete mixtures that have a constant water-binder ratio (w/b) of 0.40 and a binder (Portland cement + kaoline waste) content of 400 kg/m(3) were designed with various MW replacement contents (0%, 5%, 10%, 15%, 20% and 25% of Portland cement by weight). Workability, unit weight, compressive and tensile strengths, water absorption, porosity, sorptivity, rapid chloride permeability and drying shrinkage tests were performed on fresh and hardened concretes. Test results were analysed by considering the KW content and it was concluded that use of MW worsened the workability and decreased unit weight irrespective of KW content. MW incorporation affected the compressive strength positively, especially at the 10% and 15% replacement levels beyond 28 days. Replacement of MW up to 15% exhibited virtually identical porosity and water absorption values with the control concrete. Sorptivity values of KW concrete mixtures (at 5% and 10% kaolin waste replacement) were equal or somewhat lower than that of the control mixture. Chloride ion penetration resistance of concretes improved drastically with the increase of MW content. (C) 2015 Elsevier Ltd. All rights reserved.
Effect of metakaolin content on the properties self-consolidating lightweight concrete
(Elsevier Sci Ltd, 2012) Karahan, Okan; Hossain, Khandaker M. A.; Ozbay, Erdogan; Lachemi, Mohamed; Sancak, Emre
This paper presents the fresh, mechanical and transport properties of expanded shale aggregate self-consolidating lightweight concrete (SCLC) containing metakaolin assessed by means of slump flow, flow time, V-funnel, L-box, compressive, flexural/splitting/bond strength, water absorption, porosity, sorptivity and rapid chloride permeability tests. Metakaolin content based SCLC mixtures were developed by incorporating 0%, 20%, 40% and 60% of as a replacement by weight of fly ash while keeping a constant cement and mineral admixture content of 450 kg/m(3) and 150 kg/m(3), respectively. These included four mixtures containing 0%, 5%, 10% and 15% metakaolin content as a partial binder replacement. It was observed that expanded shale aggregates SCLC can be produced with the density lower than 2000 kg/m3 which was increased by the addition of metakaolin. Increases in metakaolin content worsened the filling and passing ability of SCLC and by the addition of metakaolin no positive effect on the strength properties on SCLC was monitored. Replacement of 20%, 40% and 60% of metakaolin with fly ash resulted 3%, 8% and 10% decrease in porosity and water absorption with respect to control mixture, respectively. The initial and secondary sorptivity values of SCLC mixtures with metakaolin replacement were equal or lower than the control mixture without metakaolin. Moreover, increases in metakaolin content showed significant improvement in chloride ion penetration resistance of SCLC. (C) 2012 Elsevier Ltd. All rights reserved.
Effect of Microcracking on Frost Durability of High-Volume-Fly-Ash- and Slag-Incorporated Engineered Cementitious Composites
(Amer Concrete Inst, 2013) Ozbay, Erdogan; Sahmaran, Mustafa; Lachemi, Mohamed; Yucel, Hasan Erhan
This paper reports the durability performance of high-volume-fly-ash (FA)- and slag (S)-incorporated engineered cementitious composites (ECCs) when subjected to mechanical loading and freezing-and-thawing cycles. Composites containing two different contents of FA and slag as a replacement of cement (55 and 70% by weight of total cementitious materials) are examined. To find out the effect of mechanical preloading on the frost durability of ECCs, prism specimens were preloaded up to a certain deformation level under four-point bending loading to generate rnicrocracks. Then, the preloaded and pristine (sound) specimens were subjected to the freezing-and-thawing test in accordance with ASTM C666/C666M. Experimental tests consisted of measuring the change in mass and ultrasonic pulse velocity (UPV) and residual flexural properties of ECC specimens exposed to the freezing-and-thawing cycles up to 300. Test results revealed that the frost resistance of ECCs was significantly influenced by the mineral admixture type and amount and preloading deformation. The deterioration with an increasing number of freezing-and-thawing cycles was relatively more for ECC mixtures with FA than for slag mixtures at the same replacement level. In addition, an increase in the FA replacement rate was observed to exacerbate the deterioration caused by freezing-and-thawing cycles. Apart from some reduction in flexural properties and UPV and an increase in mass loss and residual crack width, the results presented in this study, however, confirm the durability performance of ECC material under freezing-and-thawing cycles, even in cases where the material experiences mechanical loading that deforms it into the strain-hardening stage prior to exposure. It is important to note that this durability of ECCs under freezing and thawing was achieved without deliberate air entrainment, and contrary to conventional concrete, no relationship of frost resistance was found to the air-void structure of the ECC mixtures.
Effect of Sustained Flexural Loading on Self-Healing of Engineered Cementitious Composites
(Japan Concrete Inst, 2013) Ozbay, Erdogan; Sahmaran, Mustafa; Yucel, Hasan E.; Erdem, Tahir K.; Lachemi, Mohamed; Li, Victor C.
This paper aims to clarify the effects of sustained flexural loading on the self-healing behavior of Engineered Cementitious Composites (ECC). Prismatic specimens of ECC mixtures with two different levels of Class-F fly ash content were cast. Flexural loading was applied to the specimens at 28 days age to generate severe amount of microcracks. The specimens were then stored under continuous water or air exposures with or without sustained mechanical loading, for up to 90 days. For specimens under sustained mechanical loading, the applied sustained load level was 60% of the ultimate flexural strength. The extent of damage was determined as a percentage of loss in mechanical properties. The influences of different exposure regimes and sustained mechanical loading on mechanical properties of ECC mixtures were investigated. Microstructural changes within the microcracks were also analyzed.
Effects of fibre type on the properties of fibre-reinforced self-compacting concretes
(2011) Ozbay, Erdogan; Lachemi, Mohamed; Cassagnebere, Franck; Grant, Kevin; Varavin, George
In the last decade, a number of investigations on fiber-reinforced self-compacting concretes (FRSCC) have been carried out, and the mechanical behaviour and durability characteristics of this type of concrete are now better understood. However, the way in which fiber type affects mechanical and durability properties of this special composite has not been studied as extensively. This paper investigates the effects of three types of fibers - steel (SF), polypropylene (PPF) and polyvinyl alcohol (PVA) - on the compressive and flexural strengths, toughness, water porosity and chloride ion permeability properties of FRSCC, which were designed to contain considerably higher amounts of fiber (1% by volume). In addition, a plain concrete without fiber was produced and used as a control. Test results showed that use of fiber increased the water porosity and chloride ion permeability of the concretes, irrespective of fiber type. Use of SF increased the compressive strength, mid-span deflection, flexural strength and toughness drastically; however, use of PPF worsened those properties compared to the plain concrete.
Fresh, Mechanical, Transport, and Durability Properties of Self-Consolidating Rubberized Concrete
(Amer Concrete Inst, 2012) Karahan, Okan; Ozbay, Erdogan; Hossain, Khandaker M. A.; Lachemi, Mohamed; Atis, Cengiz D.
This paper presents the fresh, mechanical, transport, and durability performances of self-consolidating rubberized concretes (SCRCs). Fresh concrete properties were determined with slump flow, V-funnel, J-ring, and L-box tests. Mechanical, transport, and durability properties were determined by measuring compressive, flexural, and splitting tensile strengths; bond strength characteristics; water porosity; water absorption; water sorptivity; rapid chloride-ion permeability; and freezing-and-thawing and corrosion resistance. SCRC mixtures with a water-binder ratio (w/b) of 0.32; total binder content of 500 kg/m(3) (842 lb/yd(3)); and crumb rubber content of 0, 10, 20, and 30% by fine aggregate volume were produced and tested. Fresh properties testing revealed that the use of crumb rubber as a fine aggregate diminished the filling and passing ability of SCRC. A gradual reduction in mechanical properties was also observed with an increase in crumb rubber content; however, the rate of compressive strength reduction was more evident than that of tensile strength. Despite the fact that water porosity, water absorption, and chloride-ion permeability increased slightly with the use of crumb rubber, a remarkable decrease was observed in the initial and secondary water sorptivity of SCRC. No significant decrease was observed in the freezing-and-thawing and corrosion resistance of SCRC with 10% crumb rubber. Beyond that level, however, durability performance was significantly affected.
Frost resistance and microstructure of Engineered Cementitious Composites: Influence of fly ash and micro poly-vinyl-alcohol fiber
(Elsevier Sci Ltd, 2012) Sahmaran, Mustafa; Ozbay, Erdogan; Yucel, Hasan E.; Lachemi, Mohamed; Li, Victor C.
One of the most damaging environmental conditions to concrete structure is cyclic freezing and thawing. This paper discusses the influence of the high volumes of fly ash (FA) and micro poly-vinyl-alcohol (PVA) fibers on the cyclic freeze-thaw resistance and microstructure of the Engineered Cementitious Composites (ECC). ECC mixtures with two different FA-cement (FA/C) ratios (1.2 and 2.2 by weight), and at constant water-cementitious materials (fly ash and cement) ratio of 0.27 are prepared. To compare the behavior of ECC with ECC matrix, all of the preceding properties are also investigated for ECC matrix mixtures of same composition without PVA fiber. For frost resistance, mixtures are exposed to the freeze and thaw cycles up to 300 cycles in accordance with ASTM C666, Procedure A. Experimental tests consist of measuring the residual mechanical properties (flexural strength, mid-span beam deflection and flexural stress - deflection curve), ultrasonic pulse velocity and mass loss. The roles of PVA fibers and FA are discussed through the analysis of microstructure and fiber-matrix interactions as function of frost exposure. The microstructural characterization by measuring pore size distributions is examined before and after exposure to frost deterioration by using mercury intrusion porosimetry (MIP). The air-void characteristics of mixtures are also studied using linear transverse method. Test results confirm that both ECC mixtures with high volumes of FA remain durable, and show a tensile strain capacity of more than 2% even after 300 freezing and thawing cycles. On the other hand, before completing 300 freezing and thawing cycles, matrix (ECC without fiber) specimens have severely deteriorated, requiring removal from the freezethaw machine. Therefore, results indicate that the addition of micro PVA fiber to the ECC matrix substantially improved the frost resistance. The results of freeze-thaw tests also indicated that the reduction of residual physical and mechanical properties with increasing number of freeze-thaw cycles is relatively more for ECC mixture with FA/C ratio of 2.2 than for ECC mixture with FA/C ratio of 1.2. (C) 2011 Elsevier Ltd. All rights reserved.
Ground Granulated Pumice-Based Cement Mortars Exposed to Abrasion and Fire
(Springer Heidelberg, 2017) Karahan, Okan; Hossain, Khandaker M. A.; Atis, Cengiz D.; Lachemi, Mohamed; Ozbay, Erdogan
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 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.
Improving the workability and rheological properties of Engineered Cementitious Composites using factorial experimental design
(Elsevier Sci Ltd, 2013) Sahmaran, Mustafa; Bilici, Zafer; Ozbay, Erdogan; Erdem, Tahir K.; Yucel, Hasan E.; Lachemi, Mohamed
In the development of Engineered Cementitious Composites (ECC), micromechanics-based design theory is adopted to properly select the matrix constituents, fiber, and fiber-matrix interface properties to exhibit strain hardening and multiple cracking behaviors. Despite the micromechanics design constraints, practical applications show that the workability and rheological properties of matrix can affect the fiber dispersion uniformity, which have also direct concerns on composite mechanical properties. For this reason, in this research, parameters of micromechanics-based optimized ECC mixture design, which most possibly affecting the workability and rheological properties, are investigated. An experimental program that contains 36 different ECC mixtures was undertaken to quantitatively evaluate the combined effects of the following factors on workability and rheological properties: water-binder (w/b), sand-binder (s/b), superplasticizer-binder (SP/b) ratios and maximum aggregate size (D-max). A mini-slump cone, a Marsh cone and a rotational viscometer were used to evaluate the workability and rheological properties of ECC mixtures. Compressive strength and four point bending tests were used for mechanical characteristics of ECC mixtures at 28 days. The effects of studied parameters (w/b, s/b, SP/b and D-max) were characterized and analyzed using regression models, which can identify the primary factors and their interactions on the measured properties. Statistically significant regression models were developed for all tested parameters as function of w/b, s/b, SP/b and D-max. To find out the best possible ECC mixture under the range of parameters investigated for the desired workability and mechanical characteristics, a multi-objective optimization problem was defined and solved based on the developed regression models. Test results indicate that w/b, s/b and SP/b parameters affect the rheological and workability properties. On the other hand, for the range of studied aggregate sizes, D-max is found to be statistically insignificant on the rheological and workability properties of ECC. (c) 2012 Elsevier Ltd. All rights reserved.
Influence of aggregate size on the mechanical and transport properties of concretes and concrete-equivalent mortars
(Canadian Science Publishing, 2010) Ozbay, Erdogan
La presente etude examine l'influence de la dimension des agregats sur les proprietes mecaniques et de transport du beton et des mortiers de beton equivalent. Un melange de beton a ete dose en utilisant un rapport eau-ciment de 0,45 et un contenu en beton de 450 km/m(3) avec des agregats dont la taille maximale etait de 22,4 mm. Puis, en conservant constant la surface totale des agregats, trois melanges ont ete doses avec le meme rapport eau-ciment mais la dimension maximale des agregats avait diminue de 16 mm, 8 mm et 4 mm en utilisant la methode de mortiers de beton equivalent. Des essais sur les proprietes mecaniques, comprenant la resistance en compression et la resistance a la traction par fendage et les proprietes de transport incluant la permeabilite rapide aux ions chlore, le taux de sorption d'eau, l'absorption d'eau et des essais de permeabilite a l'eau ont ete realises a 7 et a 28 jours. Les resultats des essais indiquent qu'une diminution de la dimension maximale des agregats a augmente la permeabilite a l'eau, la permeabilite rapide aux ions chlore et les valeurs d'absorption et de sorption de l'eau. Toutefois, cette diminution a reduit la resistance en compression et la resistance a la traction par fendage du beton et des mortiers de beton equivalent.
Influence of cracking and healing on the gas permeability of cementitious composites
(Elsevier Sci Ltd, 2015) Yildirim, Gurkan; Sahmaran, Mustafa; Balcikanli, Muzeyyen; Ozbay, Erdogan; Lachemi, Mohamed
The main objective of the study presented in this paper was to investigate the influence of cracking and self-healing on the gas permeability of Engineered Cementitious Composites (ECC). To deliberately introduce microcracks, specimens were pre-loaded to different deformation levels under splitting tensile loading and exposed to different environmental conditionings for the assessment of self-healing. Gas permeability (GP) and resonant frequency (RF) tests, crack characteristics observation and microstructural analysis were conducted to analyze the effect of cracking and healing on the properties of cementitious composites. Test results indicate that the self-healing effect determined through GP and RF tests was strongly influenced by changes in the chemical compositions of the mixtures. Application of pre-loading led to significant increases in GP results, so that even microcracks of less than 50 mu m caused a GP coefficient fifty times higher than that of sound specimens. However, the recovery in GP results could be escalated up to 96% after only a month through proper material design and conditioning. It therefore appears that microcracking and subsequent healing is influential on the GP recovery rates of specimens, but not on RF recovery rates. (C) 2015 Elsevier Ltd. All rights reserved.
Permeation Properties of Self-Consolidating Concretes with Mineral Admixtures
(Amer Concrete Inst, 2011) Guneyisi, Erhan; Gesoglu, Mehmet; Ozbay, Erdogan
This paper addresses the permeation properties of self-consolidating concretes (SCCs) with different types and amounts of mineral admixtures. Portland cement (PC), metakaolin (MK), fly ash (FA), and ground-granulated blast-furnace slag (GGBFS) were used in binary, ternary, and quaternary cementitious blends to improve the durability characteristics of SCCs. For this, a total of 22 SCCs were designed that have a constant water-binder ratio (w/b) of 0.32 and a cementitious materials content of 926.75 lb/yd(3) (550 kg/m(3)). In addition to compressive strength and ultrasonic pulse velocity the permeation resistance of SCCs was determined by means of chloride ion permeability water permeability, and sorptivity tests. The test results indicated that the permeation properties of SCCs appeared to be very dependent on the type and amount of the mineral admixture used; the SCC mixtures containing MK were found to have considerably higher permeability resistance than the control mixture.
Properties of Mortars with Natural Pozzolana and Limestone-Based Blended Cements
(Amer Concrete Inst, 2011) Guneyisi, Erhan; Gesoglu, Mehmet; Ozturan, Turan; Mermerdas, Kasim; Ozbay, Erdogan
This paper presents the results of an experimental investigation on the consistency, compressive strength, water sorptivity, chloride ion permeability, electrical resistivity, and sulfate resistance of mortars made with plain and blended cements. Plain (CEM I 42.5 R) and blended cements, including portland pozzolana cements (CEM II A-P 42.5 R and CEM II B-P 32.5 R) and portland limestone cements (CEM II A-LL 42.5 and CEM II B-LL 32.5 R), were used in this study. Mortars with three different water-cement ratios (w/c) of 0.420, 0.485, and 0.550 were produced by using the plain and blended cements. In all the mixtures, the cement:sand ratio was kept constant at 1:2.75 by weight. The compressive strengths of the mortar specimens were tested at 1, 3, 7, 28, 90, and 180 days. Moreover, the water sorptivity, chloride ion permeability, and electrical resistivity of the mortar specimens were measured at 7, 28, 90, and 180 days. The sulfate resistance of the mortars was evaluated by the length change of the mortar specimens up to 30 weeks of exposure. The test results revealed that the use of blended cements decreased the water sorptivity and chloride ion permeability while increasing the electrical resistivity and sulfate resistance of the mortars at later ages compared to the normal portland cements.
Relative Compressive Strength of Concretes under Elevated Temperatures
(Amer Concrete Inst, 2012) Ozbay, Erdogan; Lachemi, Mohamed
The effects of aggregate type (AT), test type (TT), maximum exposure temperature (MET), and compressive strength before fire (CSBF) on the relative strength (RS) of concrete have been thoroughly explored. For this purpose, the worldwide database of experimental research results of temperature-dependent properties of unreinforced concrete compiled by Knaack et al. was used to generate training and testing data sets to construct closed-form solutions for the neural network (NN). The AT, TT, MET, and CSBF were used as input parameters and relative compressive strength was used as the output parameter of the NN model. The results were used to develop predictive relationships for compressive strength loss under fire and for comparison with the models proposed by ACI 216.1-07 and Knaack et al. A sensitivity study of the parameters was also carried out, and the underlying complex nonlinear relationships among these parameters were investigated. Through the results of modeling and simulation studies, it was demonstrated that a single NN-based explicit equation can be obtained and used to define the RS of concrete exposed to fire.
Repeatability and Pervasiveness of Self-Healing in Engineered Cementitious Composites
(Amer Concrete Inst, 2015) Sahmaran, Mustafa; Yildirim, Gurkan; Noori, Rezhin; Ozbay, Erdogan; Lachemi, Mohamed
This paper investigates the intrinsic self-healing ability of engineered cementitious composites (ECCs) coupled with multiple microcrack formation under mechanical loading based on two robustness criteria: repeatability and pervasiveness. To this end, two different composites containing Class F fly ash and slag were investigated To generate microcracks, specimens were repeatedly preloaded up to 70% of their deformation capacities under mechanical loading at the end of each specified cyclic wet/dry conditioning period Resonant frequency (RP) a,id rapid chloride permeability tests (RCPT) were used to assess the extent of damage and self-healing, and final results were supported by microscope observations. RF measurements were recorded from two different parts of each specimen (the top and middle portions) to monitor whether self-healing takes place in certain regions or whether it is pervasive over the entire specimen. Results of the experimental study show that depending on the type of mineral admixture used and the duration of initial curing before deterioration, ECC specimens can recover up to 85% of their initial RF measurements, even after six repetitive preloading applications. The recovery rates observed in the middle portion are similar to those in the top portion for both ECC mixtures (to a slightly lesser extent), which implies that self-healing is quite pervasive. Furthermore, after repeated application of severe preloading, RCPT results for both mixtures selfish) low or moderate chloride ion penetrability levels in accordance with ASTM C1202. Due to the enhanced self-healing capability of specimens, maximum crack width observed over the specimen surfaces was restricted to 190 mu m (0.008 in), even after nine preloadings. These findings suggest that under certain conditions, the ECC materials produced in this study may significantly enhance the functionality of structures by reducing the need for repair and/or maintenance.
Self-healing ability of cementitious composites: effect of addition of pre-soaked expanded perlite
(Ice Publishing, 2014) Sahmaran, Mustafa; Yildirim, Gurkan; Ozbay, Erdogan; Ahmed, Karwan; Lachemi, Mohamed
This study assessed the use of pre-soaked expanded perlite aggregate (PS-EPA) on the self-healing of cementitious composites by replacing a proportion of normal aggregate with PS-EPA at different replacement rates. Specimens with and without PS-EPA were stored in water for 28 d and then mechanical loading was applied to produce specimen deterioration. At the age of 28 d, pre-loaded and sound specimens were exposed to continuous air (CA) exposure for 30 d. The degree of deterioration as a result of mechanical pre-loading and the degree of self-healing were determined via characterisation of crack numbers and widths, transport (chloride ion permeability) and mechanical properties (splitting tensile strength), and specimens with and without PS-EPA were compared. The test results revealed that increased PS-EPA content significantly improved the compressive strength and chloride ion permeability of specimens, and that it further enhanced the hydration and healing capability of specimens under CA exposure after pre-loading.

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