An Overview of Geo-Polymer Concrete Including Recycled Aggregate

INTERNATIONAL JOURNAL OF SCIENTIFIC & TECHNOLOGY RESEARCH VOLUME 9, ISSUE 03, MARCH 2020 ISSN 2277-8616 An Overview Of Geo-Polymer Concrete Including Recycled Aggregate

Khaleel H. Younis, Koran A. Salihi, Talib K. Ibrahim

Abstract: In order to mitigate the problem of CO2 emissions into the environment, which is a worldwide recognized issue, the use of natural materials needs to be minimized. Among many solitons to that problem, geopolymer binders and recycled aggregates are considered as environmentally friendly products, they can be utilized to concrete production since geopolymer and recycled aggregates are the part of the sustainable development of concrete, and using them to make concrete addresses the problem of CO2 emissions. And Geopolymer concrete with recycled concrete (RCA) could be an effective method. One of the hardened properties of concrete is compressive strength, which is the most vital properties by having the final say to determine the required quality. As for the rheological properties of any concrete mixture, the workability is counted as the most important characteristics, in this study the use and effect of recycled aggregate (RCA) in geopolymer concrete is presented and reviewed. The main objective of this paper is to discuss compressive strength and workability of geopolymer concrete made with recycled aggregate.

Index Terms: Geo-Polymer concrete, Compressive strength, Recycled aggregate, Review, Workability, Fly Ash, ——————————  ——————————

1 INTRODUCTION It is obvious that water is the most consumed material in the the CDW be a good potential to use as recycled coarse world but second material used in the world mostly is aggregate (RCA) [5]. This theme is not new, but recently there concrete. Over the next few years, the use of concrete is has been a lot of research that refers to the inferior properties expected to increase due to a significant growth in the world of concrete, including recycled aggregate, compared to population and urban development. The reasons which make conventional concrete [8] [5, 9]. concrete being preferred, its exceptional strength properties, Geopolymer is a new binder currently under development. specifically compressive strength, economics, availability, and This is a kind of binder developed to replace the use of its excellent durability. [1, 2]. One of another properties of cement in the production of concrete. The aim is to develop a concrete which makes the concrete most suitable material for sustainable and eco-friendly concrete that contains alternative construction is that, it can be molded to any shape. The main binder to OPC. Initially, the geopolymer was first discovered by ingredient in concrete is OPC (ordinary Portland cement) Davidovits in 1991 [10]. The term geo-polymer is a two-part which is the binder of the aggregate particles in any mixture of term called geo and polymer. The former ―geo‖ is geological or concrete. However, an extreme quantity of energy is required industrial materials such as fly ash (FA), blast furnace slag to product OPC and one ton of CO2 is released to the (BFS), silica fume (SF), and shell ash (RHA) rich in silica (Si) atmosphere for every single ton of OPC production. The and alumina (AL). Means the material derived from by- cement industries in the world are responsible for %8 of the products), the latter "polymer" means a chain of molecules total global greenhouse emission, and CO2 is the main reason produced from the same unit. When alkaline activator is for global warming. [3]. To overcome that concern, most of the bonded with one of these by-products is, a geopolymer binder studies and researches have been focused on finding a is obtained. The total energy required to produce fly ash-based sustainable alternate binder, supplementary cementitious geopolymers is 60% less than cement production and CO2 materials (SCM) to OPC to be used in concrete. In addition, emissions are at least 80% less [11]. There has been a lot of the consumption of natural aggregate (NA) is increasing due research and research on geopolymer concrete and to the continually increasing need for the use of concrete. The composites around the world so far, and in the future result for this is abiotic depletion which is gradually destroys geopolymer concrete may exist in the world as the ultimate the natural resources of the ecosystem. In addition, sustainable building material [12]. In fact, the use of construction and demolition waste (CDW) disposal can be geopolymer concrete can help increase the sustainability of used as a means to encourage many researchers around the concrete technology and the construction industry. This world to find different ways to recycle and reduce pressure on reinforcement can be further developed by mixing recycled scarce landfill spaces available as a means of reducing aggregates to geopolymer concrete, it can be partial or 100% dependence on the current resources of natural aggregates replacement of NA. In the result, the greenhouse gases can and minerals [4] [5] [6, 7]. Depending on the fact of be reduced to minimum and landfills are relieved from the composition of concrete, it is well-known that the percentage pressure of a huge amount of CDW accumulation. of fine and coarse aggregate is 75-80%, so that would make Geopolymer binders are OPC's sustainable alternative ——————————————— composite materials, where recycled aggregates and  Khaleel H. Younis , Assistant Professor at: geopolymers are mixed to produce recycled aggregate - Erbil Polytechnic University-Road Construction Dept. Erbil-Iraq. geopolymer concrete there is a possibility that will provide - Tishk International University, Civil Engineering Dept. Erbil –Iraq. ultimate sustainability in the construction industry in the near E-mail: [email protected] future. The purpose of this study is to present a review on  Koran A. Salihi is a researcher at: -Tishk International University, Civil Engineering Dept. Erbil-Iraq. geopolymer binders and recycled aggregates. Additionally, a E-mail: [email protected] literature review will provide details on the performance of  Talib K. Ibrahim, Professor at: sustainable geopolymer concrete incorporating RCA. This - Knowledge University, College of Engineering, Environment includes the following: Rheological and mechanical properties Dept. of geopolymer concrete mixtures made with RCA. Email: [email protected] 6239 IJSTR©2020 www.ijstr.org INTERNATIONAL JOURNAL OF SCIENTIFIC & TECHNOLOGY RESEARCH VOLUME 9, ISSUE 03, MARCH 2020 ISSN 2277-8616

2 BACKGROUND materials. Recently the studies and researches about cement- There are numerous published studies and papers that tackle less concrete concluded that, there are many factors influence the fresh and mechanical properties, and durability the mechanical properties. Besides, the authors recently characteristics for geopolymer concrete mixed with natural focusing their studies on investigating the reaction aggregate and OPC concrete, there are also studies about mechanisms by using paste and mortar excluding aggregates. OPC concrete incorporated with recycled aggregate. Based on the extensive test results of OPC concrete by Yang Contrariwise, limited number of researchers have studied and et 2008, the development of compressive strength of alkali investigated the mechanical properties and durability of activated mortar was compared with the design formula geopolymer concrete mixed with RCA [13, 14]. specified in ACI 209 and EC 2 [29].

2.1 Recycled coarse aggregate concrete 3 RHEOLOGICAL PROPERTIES OF RECYCLED Compressive strength, bending strength, tensile strength, and AGGREGATE GEO-POLYMER CONCRETE elastic modulus are RAC properties also called hardened (RAGC) properties. These properties depend on many parameters The nature of the geopolymerization process is mainly affected such as the w / b ratio, engineering and physical properties of by the chemical activator and curing periods and types, which RA used in concrete. Not only the fine structure, also the is also, influence the rheological properties, and physical weakness of the bonds between the old mortar and RA leads properties of geopolymers [30, 31]. It was found that the to appearance of diagonal cracks and opening in recycled period of curing for high calcium fly ash geopolymer paste was aggregate during the procedure of recycling and the presence directly proportioned to the NaOH concentration up to 18 of weak porous mortar around RA. The main concern about molarity. At low concentration of NaOH the leakage of Ca 2+ RAC is its inferior mechanical properties, which is a challenge into the pore solution is not considerably interfered, which to accurately validate prior to its use. Additionally, the results in appropriate dissolved Ca 2+ in the reaction, calcium replacement ratio and the moisture content of RAC are the silicate hydrate (C-S-H) and aluminate allow for the formation major parameters influence its mechanical properties. [15, of calcium hydrate (C-A-H) gel. But as the concentration of 16]. Water absorption of RA, free moisture content of NaOH is increased the geopolymerization process dominate aggregate, and amount of attached mortar in RAC, are the curing regime of the paste, compared to to CSH and CAH affected by the w/b ratio so it considered as a critical factor. dependent cement systems, the geopolymerization process However compressive strength of RAC also could be induced occurs at a slower rate, so it leads to a longer curing period. by many aspects, but mainly by replacement ratio, w/b ratio [30]. The study of ground bottom ash (GBA) done by [16, 17] and moisture condition of RA. Mechanical and Sathonsaowaphak et al.[32]. In the study the flow was tested physical properties of RA are also crucial this is because the for geopolymer mortars containing numerous alkaline crush strength and impact strength of the aggregate affect the liquid/ash, ratio and sodium silicate/ sodium hydroxide ratio at resistance to compressive load. Many studies, researchers, different NaOH concentrations. The result in the practical and authors mentioned that the compressive strength of RAC range of liquid alkali / ash ratio was 0.429-0.709. as the liquid is directly proportion to the replacement amount or percentage alkali / ash ratios increased geopolymer mixtures found to be (%) of recycled aggregate (RA) using the same w/b ratio[18] more workable this was because of inferior particle [19], and many papers and researches presented that the interference and greater inter-particle distance. While the compressive strength with %100 replacement with RA is %30 outcome of for the practical range of SS (sodium silicate) / less compared to natural concrete aggregate. [20, 21]. Similar NaOH, ratio and, NaOH concentration was 0.67-1.5-7.5-12.5 cases, also recorded by some other authors, that concluded M respectively. Higher ratio of SS / NaOH and, higher NaOH the decrease in compressive strength is between 12% and concentration caused in a less workable mortar mixture due to %25 with 100% RA replacement ratio [15, 22, 23]. the higher viscosity of sodium silicate and NaOH. Due to economic issues the quantity of sodium silicate in the mortar 2.2 Geo-polymer Binders mixture should be kept as low as possible, but it is also Among several by-product waste materials which are recommended not to compromise the workability and strength produced and generated in different industrial fields, some of of the geopolymer mortar. In palm oil fuel ash (POFA) it was them could be suitable to substitute OPC binder, and can be found that by increasing the solid/liquid ratio, and decreasing as the source for geo-polymer. It is challenging to discard the SS/SH ratio in samples of geopolymer paste, higher those extreme amounts of wastes in the environment so it can amounts of efflorescence occurred [34]. As the source material be the potential alternative for OPC. Fly ash also known as for geopolymer concrete Fly ash class F ASTM, is the material PFA pulverized fuel ash is one of the waste materials that used the most [25, 35, 36]. One of the disadvantages of the could be source for geo-polymer, FA is industrial waste from aforementioned ash material, is the heat curing requirements, power plants generated from coal combustion, accounting for due to the extra energy which is needed to produce 75-80% of the world's annual ash production. [24]. Fly ash geopolymer concrete if compared to conventional concrete, compared to OPC concrete have better mechanical and this heating is required to obtain faster setting time and high durability properties [25, 26]. By increasing the fineness of the early strength for the geopolymer pastes. However angular fly ash, the properties of fly ash based geopolymer concrete shape, high water absorption and the roughness the recycled can be improved. In case of increment of surface area of the aggregate, influence the fresh properties of concrete [37]. fly ash the geopolymerization process also increase, which Generally, the porosity of RCA aggregate is higher than the leads to more reactive fly ash. [27, 28]. Concrete is a multi- natural aggregate, this is because of the adhered mortar of faceted, heterogeneous material, and the mechanical RCA. There are some solutions to the mixing methods properties related to stress are affected by the behavior of developed recently to overcome the workability concerns, each component material and the interface between these such as adding the super-plasticizer, increasing the water 6240 IJSTR©2020 www.ijstr.org INTERNATIONAL JOURNAL OF SCIENTIFIC & TECHNOLOGY RESEARCH VOLUME 9, ISSUE 03, MARCH 2020 ISSN 2277-8616 content, and using pre-saturation RCA, or increasing, cement natural aggregate mixes. Additionally, due to the fineness and amount in the concrete composition. It was recorded by angular shapes of the metakaolin which plays the major role in Mathias et al. that the RCA with higher water absorption affect the workability, thus by increasing the percentage of the MK the mixing water [38] and results in a unavoidable variations in the slump flow is decreased [44]. Replacement ratios for 0%, the workability of concrete. Since the water content in the mix 10%, 20% and 30% of metakaolin (MK) the slump flows for affects the workability and the final strength of the mixture, RAGC are 697, 609, 546, and 473 mm, separately. However therefore it is necessary to calculate the water required and for the NAGC at the same percentage of MK the slump flows the water absorbed by the RCA, the estimation of the mixing are reduced by 17%, 20% and 16%. time also shouldn‘t be avoided. Moreover, it was concluded by Padmini et al. [39] that 10 minute of absorbing water by RCA 4 MECHANICAL PROPERTIES OF RECYCLED is sufficient to occur suitable workability performance of concrete. In another method conducted by Etxeberria et al. AGGREGATE GEO-POLYMER CONCRETE [40], in the study higher quantities of super-plasticizer than to (RAGC) the natural mix were used in samples containing RCA Many authors have published numerous studies about the aggregate to attain the required slump and w/b ratio. The mechanical performance of geopolymer concrete incorporating authors Gonzalez-Fonteboa and Martinez-Abella [41] used recycled aggregate, the results and outcomes of selected 50% of coarse recycled aggregate, in their study to obtain the studies are reviewed in the following section, Anuar et al. slump similar to conventional concrete, they increased the (2011) [14], investigated the effects of recycled aggregate from amount of the cement by 6.2%.Nuaklong et al, [33], published concrete wastes on compressive strength of geopolymer a paper investigating the influence of recycled coarse concrete, and using fly ash and slag used paper sludge ash as aggregate on fly ash based geopolymer concrete, in their fresh the geopolymer binder. The compressive strength was th th properties result, slump for geopolymer concrete mixed with increased by 10% at 28 day in accordance with 7 day %100 recycled coarse aggregate, was between 550-660. results, while the higher molarity of the activator solution According to EFNARC (2005),[42] this result was clearly a resulted in higher compressive strength. The mechanical proof of the geopolymer of this study is class SF1 self- properties of geopolymer concrete was recorded in another compacting concrete, and this is because of high viscosity of study by Shuang et al. (2012) [45], they investigated geopolymer concrete. Moreover, in another practical study geopolymer concrete mixed with two different quantities of conducted by Nuaklong et al,[1], it was found that the 50% and 100% RCA as a replacement of NCA and compared workability and slump flows of geopolymer concrete the result with those of normal concrete. The results show that incorporated with recycled coarse aggregate (RCA), and geopolymer concrete containing RCA has a lower compressive replacing different percentages of metakaolin (MK) as additive strength and elastic modulus than comparable virgin concrete to the mixes, was higher than required, without using any containing RCA, and the mechanical properties decrease as super-plasticizer. In the Figure 1 the slump flow for the the RCA content increases. In the same study it was found geopolymer concrete mixed with various ratio of metakaolin that the ITZ of geopolymer concrete is more enhanced (MK) is presented. As for the results for Natural Aggregate compare to conventional concrete. Recently, Posi et al. (2013) Geopolymer Concrete (NAGC) and RAGC the range is published a study about the mechanical properties of between 398–510 mm and 473–697 mm, separately. Clearly geopolymer concrete, mixed with, recycled lightweight this shows that the slump flow for RAGC is almost 16.0–26.8% aggregate and recycled coarse aggregate, in the result it was higher than that for NAGC. These results are resembled with discovered that the compressive strength is decreasing with studies done by [40,41] on the use of RCA in OPC concrete. increasing the quantity of recycled lightweight aggregate [46]. Sata et al. (2013), [13] instead of natural coarse aggregate (NCA), they studied crushed concrete and crushed bricks in a geopolymer permeable concrete test with different concentrations of sodium hydroxide solution (NaOH). The results showed that the compressibility and indirect tensile strength of geopolymer permeable concrete, including ground concrete and ground brick, is lower because recycled coarse aggregate is less than natural coarse aggregate. it was also found that, higher concentration of sodium hydroxide solution resulted in higher compression and indirect tensile strength of all three geopolymer concrete. Recently another paper was published by Nuakalong et al. (2016), in their research they studied about geopolymer concrete made from crushed concrete as coarse aggregate, they observed clear decrease FIG. 1. Workability of geopolymer concrete of NCA from lime in compressive strength due to the addition of recycled stone (L) and RCA from crushed concrete specimen (C)[1]. crushed concrete as coarse aggregate [33]. In this study, there were a comparison between two types of coarse aggregate, Poon et al.[43] published a paper about the effect of moisture natural crushed limestone and recycled coarse aggregate, in condition of natural (NA) and recycled aggregates (RA), on the results, the strength of RCA mixes were 76-93% same, in slump flow and compressive strength of concrete, in the study accordance with the mixes with natural crushed limestoneIn their recommendation was to add a big amount of free water another study by Shaikh, F. U. A. (2016) [47] about mechanical to the RAG batches to attain SSD condition, this leaded to and durability of fly ash based geopolymer concrete, mixed release the trapped water particles due to cracking while with recycled coarse aggregate from local demolition and mixing, so the result was higher workability compare with waste. The results show that when 50% of RCA is partially 6241 IJSTR©2020 www.ijstr.org INTERNATIONAL JOURNAL OF SCIENTIFIC & TECHNOLOGY RESEARCH VOLUME 9, ISSUE 03, MARCH 2020 ISSN 2277-8616 replaced by NCA, the compression strength is reduced by In his paper, Khater [58] investigated the impact of silica fume 15% in 7 days compared to 100% NCA geopolymer concrete, on concrete waste and metakaolin and recorded a significant and there is a difference in 28 days as shown in Figure 2. It increase at 90 days of age as long as the material hardened at shows that there is. The indirect tensile strength was almost room temperature 25 C and 100% RH. Ahmari et al. [59] the same. studied the impact of mixing concrete wastes with fly ash using 60 solution of sodium silicate, and sodium hydroxide as activator,

days days the maximum compressive strength obtained was 35 MPa, 50 28 28 45.3 where they used the ratio of sodium silicate to sodium 41.8 40 37.6 36.8 hydroxide of 2, with molarity of 10M. In another research the effect of silica fume and metakaolin on geopolymer concrete 30 (MPa) mixed with concrete waste, were investigated by Yang et al. [60], the geopolymer concrete based on a blended mixture of 20 concrete waste and metakaolin (5–25%) recycled aggregates 10 percentage is 40%. They concluded that after addition of Compressive strength at at strength Compressive metakaolin and silica fume the final compressive strength 0 GPC0 GPC15 GPC30 GPC50 increases significantly. the results of some of the researches Type of Concrete Mix that inspected the performance of the geopolymer concrete incorporated with recycled coarse aggregate, are abridged FIG. 2. Effect of RCA content on the compressive strength on and presented in Table 1. The table illustrates the percentage geopolymer concrete (47) of the RCA, binder type, percentage of the alkaline solution and its molarity, curing type and time, the compressive Krishnan et al. (2017) [48], studied different factors that affect strength at different ages and the main finding of these the strength of geopolymer concrete, they used 100% RCA, in studies. their study, they showed that in their results that, compressive strength of RCA mixes was increased by 3%, with specific TABLE 1. period of curing and temperature. Aly et al. (2019),[49] in his Effects of replacement ratios of RCA on compressive strength research recently studied the effects of recycled rubber on of geopolymer concrete mixtures. performance of slag based geopolymer concrete, the authors have reported that there is a significant enhancement of compressive strength by inclusion of recycled rubber by 10%.Nuaklong et al. (2018), in their study concluded the compressive strength can be increased by 37% compare with 100% natural coarse aggregate by addition of 15% OPC to the 100% recycled aggregate geopolymer mixes [1]. Allahverdi and Kani [50] in their paper, obtained 40 MPa compressive strength by using brick wastes from construction fragments at 28 days of curing, in their research they used sodium hydroxide (NaOH) in a proportion of 8% Na2O, as alkali activator. Their strength result was up to 50 MPa in a following study, using a blend of concrete wastes and brick wastes with amount of 60% and %40, and activated with a solution of sodium hydroxide (NaOH) and sodium silicate (Na2SiO3) [51, 52]. Another study done by Sun et al. [53], mixed ceramic urban waste with geopolymer, as activator they used KOH and NaOH the result of compressive strength was 71.1 MPa at 28 days for the curing method of 60 C. In a similar study by, Reig et al. [54] in his research he used clay brick waste with 7 M of sodium hydroxide (NaOH) as activator, as the result in they obtained a compressive strength of 30 MPa at 7 days of curing at 65 C. Another study achieved by Lampris et al. [55] they use alkali-activated microwaste (663 lm) of construction waste built in a recycling plant, compressive strength is 18.7 MPa in 7 days, curing is 105 ° C, 20% for 24 hours at room temperature, As a result of adding metakaolin, the soluble alumina source increased the strength of the geopolymer by 112% and 63%.Komnitsas et al. [56] published a study aiming to find out the potential of different materials from construction wastes, such as tiles, bricks and concrete, to be used in geopolymer concrete, as for the activator they used NaOH of 14 M as and the curing was at 90 C for 7 days, the result showed that a compressive strength of 49.5 and 57.8 MPa for bricks and tiles were obtained, but for the concrete waste, the compressive strength was just 13 MPa, which is as a result is 43% higher than the research done by Pathak and Kumar [57]. 6242 IJSTR©2020 www.ijstr.org INTERNATIONAL JOURNAL OF SCIENTIFIC & TECHNOLOGY RESEARCH VOLUME 9, ISSUE 03, MARCH 2020 ISSN 2277-8616

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