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In this paper, effects of elevated temperatures on the compressive behaviour of rubber crumb and steelfibre reinforced recycled aggregate concrete (RSRAC) are presented. RSRAC is a new concrete materialproposed by the authors. In the RSRAC, steel fibre is used to improve the performances of concrete beforeexposure (e.g. ductility, cracking) and after exposure (explosive spalling) to evaluated temperature, andthe inclusion of rubber particles is mainly for the consideration of environment protection and reducingthe risk of spalling after exposure to high temperatures. A series of concrete mixes were prepared withOrdinary Portland Cement (OPC), recycled concrete coarse aggregates (RCA) or natural coarse aggregates(NCA), 1% steel fibre (by volume) and rubber particles with different fine aggregate (sand) replacementratios. The compressive properties, including compressive strength, Young’s modulus (stiffness), stressestrain curves and energy absorption capacity (toughness) of the different concrete mixes subjected toelevated temperatures (25 C, 200 C, 400 C and 600 C), were obtained in accordance to ASTM standards.The results of weight loss and failure modes were recorded and presented in this study. The resultsshowed that both the compressive strength and stiffness of concrete mixes decreased after exposure toelevated temperature, with higher replacement of fine aggregate by rubber leading to lower compressivestrength and stiffness magnitude. Nevertheless, rubber crumbs significantly enhanced the energy absorptioncapacity and explosive spalling resistance.

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    Article history:Received 16 September 2013Received in revised form12 February 2014Accepted 15 February 2014

    reducing admixtures (Barbudo et al., 2013). It is also known that theuse of recycled aggregates in concrete decreases its strength andYoungs modulus compared to those of natural aggregate concrete(Miguel and de Brito, 2012). Poon et al. (2002) reported that thereplacement of coarse and ne natural aggregates by RCA (Recycled

    or above) signi-hile an air-driedRCA was optimalRAC) with normal. It is worth notingompensate for theility) of concreteresults have beenat the propertieslitting strength) of

    the self-compacting concretes made from river sand and crushedne recycled concrete aggregates (with 0, 25%, 50%, 75% and 100%replacement rates) showed only slight differencewith the inclusionof y ash, demonstrating the feasibility of utilizing ne and coarserecycled concrete aggregates together with y ash for self-compacting concretes. It has also been shown that the negativeeffect of RCA on durability properties of mixes can be mitigated byincorporating a certain amount of mineral admixtures, such as yash and volcanic ash (Kou and Poon, 2012). These research results

    * Corresponding author. Tel.: 86 20 39322538; fax: 86 20 39322511.

    Contents lists availab

    Journal of Clean

    .e ls

    Journal of Cleaner Production 72 (2014) 193e203E-mail address: guoyc@gdut.edu.cn (Y.-c. Guo).1. Introduction

    Waste concrete, often referred to recycled concrete aggregate(RCA), has been reused as a replacement of the natural aggregatefor new concrete mainly for the consideration of environmentalbenet and effective utilization of resources. Various authors havestudied the properties of concrete preparedwith RCA. However, theincorporation of RCA leads to a signicant loss of uidity of themixture (Mefteh et al., 2013) caused by the attachedmortar contentof the RCA. This reduction certainly can be compensated by water-

    Concrete Aggregate) at higher levels (e.g. 50%cantly reduced the compressive strength; waggregate that contained not more than 50% offor producing the Recycled Aggregate Concrete (strength (less than 60MPa) (Poon et al., 2004a,b)that various methods have been attempted to clower quality (e.g. lower strength, less durabproducts with recycled aggregates and goodachieved. Kou and Poon (2009) pointed out th(mainly the compressive strength and tensile spAvailable online 1 March 2014

    Keywords:Rubber crumbSteel breRecycled concrete aggregateCompressive propertiesHigh temperaturehttp://dx.doi.org/10.1016/j.jclepro.2014.02.0360959-6526/ 2014 Elsevier Ltd. All rights reserved.In this paper, effects of elevated temperatures on the compressive behaviour of rubber crumb and steelbre reinforced recycled aggregate concrete (RSRAC) are presented. RSRAC is a new concrete materialproposed by the authors. In the RSRAC, steel bre is used to improve the performances of concrete beforeexposure (e.g. ductility, cracking) and after exposure (explosive spalling) to evaluated temperature, andthe inclusion of rubber particles is mainly for the consideration of environment protection and reducingthe risk of spalling after exposure to high temperatures. A series of concrete mixes were prepared withOrdinary Portland Cement (OPC), recycled concrete coarse aggregates (RCA) or natural coarse aggregates(NCA), 1% steel bre (by volume) and rubber particles with different ne aggregate (sand) replacementratios. The compressive properties, including compressive strength, Youngs modulus (stiffness), stressestrain curves and energy absorption capacity (toughness) of the different concrete mixes subjected toelevated temperatures (25 C, 200 C, 400 C and 600 C), were obtained in accordance to ASTM stan-dards. The results of weight loss and failure modes were recorded and presented in this study. The resultsshowed that both the compressive strength and stiffness of concrete mixes decreased after exposure toelevated temperature, with higher replacement of ne aggregate by rubber leading to lower compressivestrength and stiffness magnitude. Nevertheless, rubber crumbs signicantly enhanced the energy ab-sorption capacity and explosive spalling resistance.

    2014 Elsevier Ltd. All rights reserved.a r t i c l e i n f o a b s t r a c tCompressive behaviour of concrete struconcrete aggregates, rubber crumb andsubjected to elevated temperatures

    Yong-chang Guo a,*, Jian-hong Zhang a, Guang-mina School of Civil and Transportation Engineering, Guangdong University of Technology,b School of Civil Engineering and Transportation, South China University of Technology,

    journal homepage: wwwures incorporating recycledinforced with steel bre,

    hen a, Zhi-hong Xie b

    gzhou, Chinangzhou, China

    le at ScienceDirect

    er Production

    evier .com/locate/ jc lepro

  • Prohave clearly promoted the promising use of RCA in construction. Todate, RAC has been successfully applied in pavements and buildingstructures in China, as shown by Li et al. (2009).

    Steel bre reinforced concrete (SFRC) was recognised to improvethe brittleness and lower tensile capacity of plain concrete. Thestudies showed steel bres inside concrete matrix can increase thetoughness and cracking resistance of concrete mainly due to thebridging/tying effects of steel bres on surrounding concrete, buthave little effect on the compressive behaviour of concrete probablybecause of the reduction/loss of the above effects in concrete undercompression (Atis and Karahan, 2009; Olivito and Zuccarello, 2010).Yang et al. (2006) and Gao et al. (2007) showed that when recycledaggregate concrete is reinforced with a certain amount of steel -bres, its compressive performance is similar or slightly lower thanthe natural aggregate concrete reinforced with equivalent amountof steel bres, but signicantly higher than ordinary plain concrete.This suggests that steel bre reinforced recycled aggregate concretemay be used to replace ordinary concrete in the construction ofstructural members. Furthermore, steel bres have been exten-sively used to improve the ductility of concrete. It has been foundthat steel bres can reduce spalling and cracking and improve theresidual strength of concrete after exposure to elevated tempera-tures (Peng et al., 2006; Poon et al., 2004a,b). In particular, Poonet al. (2004a,b) showed that the energy dissipation capacity(toughness) of SFRC subjected to high temperatures can be almosttwo times that of plain concrete. Existing research also indicatedthat when steel bre content is higher than 1.5% by volume of theconcrete, the increase of steel bre content results in littleimprovement or even reduction of the above performances ofconcrete (e.g. residual strength, toughness) (Lau and Anson, 2006).As a result, many of the current studies of steel bre reinforcedconcrete used around 1.0% steel bres.

    The fast development of automotive industry after the SecondWorld War has led to the rapid accumulation of waste tire rubber.Waste tire rubber is extremely difcult to degrade in landlltreatment. As a result, the treatment of waste tire rubber hasrecently become a world-known environmental problem. Existingstudies showed that concrete performances can be signicantlyimproved by including recycled rubber crumbs obtained fromwaste tires into the basic concrete composition (Hernndez-Olivares and Barluenga, 2004; Lau and Anson, 2006; Hernndez-Olivares et al., 2002; Son et al., 2011; Khaloo et al., 2008)Hernndez-Olivares et al. (2002) showed that a small volumetricfraction of crushed tire rubber crumbs are of great contribution tothe dynamic behaviour of concrete under low-frequency dynamicactions. Mustafa Maher Al-Tayeb et al. (2013) received the similarconclusion that the use of hybrid rubberized concrete beam im-proves exural impact performance of the beam during dynamicloading compared to static loading. Moreover, the addition ofrubber improved the toughness and deformation ability of thenormal concrete. Son et al. (2011) found that the rubber crumbsmay greatly improve the deformation capacity of the concretealthough the compressive strength of concrete may be slightlyreduced. Khaloo et al. (2008) indicated that the brittleness ofconcrete can be signicantly decreased with increasing rubbercontent, with the crack width and crack propagation velocity in therubberized concrete (i.e. concrete with rubber content) beingobviously lower than those of plain concrete. Li et al. (2009) alsoobtained the similar conclusions in their experimental study onhigh strength concrete lled by recycled rubber. Furthermore, it hasbeen found that rubber crumbs can effectively reduce the risk ofexplosive spalling and strength loss rate of concrete after exposureto elevated temperatures (Hernndez-Olivares and Barluenga,2004). This is because rubber crumbs, if burnt after exposure to

    Y.-c. Guo / Journal of Cleaner194evaluated temperatures, can release space for the escaping of watervapour in concrete and thus protect the concrete body fromexplosive spalling (Li et al., 2011). Apparently, the inclusion ofrubber in concrete composition not only reduces the risk ofexplosive spalling and strength loss rate for concrete subjected toelevated temperatures, but also has a signicant environmentadvantage as mentioned above.

    Recently, it has been found that rubber content had no adverseimpact on the bridging and tying effects of steel bres on sur-rounding concrete and the positive synergy between steel bresand rubber particles has the advantage of enhancing the resistanceto shrinkage cracking (Turatsinze et al., 2006) and improving thefracture behaviours even subjected to elevated temperature (Guoet al., 2014).

    Against the above background, rubberized steel bre reinforcedrecycled aggregate concrete (RSRAC) was proposed by the authors(China invention patent No.: ZL. 201010019345.3). This new type ofmat

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