In this study, crumb rubber was used to partially replaced fine aggregate in mortar mixture by 5, 10, 15, and 20 volume percentage (vol%) with untreated and NaOH-treated crumb rubber. Thus, the total number of mixtures was 9. The mortars were tested for its flowability, compressive strength, flexural strength and density. Based on the results, increasing the replacement percentage of fine aggregate by crumb rubber reduced the compressive strength, flexural strength and density of rubberized mortar but increased the flowability. Meanwhile, the treatment of crumb rubber using NaOH solution improved the flowability, compressive strength and flexural strength. The treatment has minor effect on the hardened density of the rubberized mortar

Ahmad Nurfaidhi Rizalman

Dhabit Zahin

English

UMS Institutional Repository

IOP Conference Series: Earth and Environmental SciencePAPER • OPEN ACCESSProperties of cement mortar containing NaOH-treated Crumb rubber asfine aggregate replacementTo cite this article: D Z A Tudin and A N Rizalman 2020 IOP Conf. Ser.: Earth Environ. Sci. 476 012030 View the article online for updates and enhancements.This content was downloaded from IP address 175.138.102.103 on 05/09/2020 at 06:39Content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence. Any further distributionof this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.Published under licence by IOP Publishing Ltd2nd International Conference on Civil & Environmental EngineeringIOP Conf. Series: Earth and Environmental Science 476 (2020) 012030IOP Publishingdoi:10.1088/1755-1315/476/1/0120301Properties of cement mortar containing NaOH-treated Crumbrubber as fine aggregate replacementD Z A Tudin and A N RizalmanCivil Engineering Programme, Faculty of Engineering University Malaysia Sabah,88400 Kota Kinabalu, Sabah, MalaysiaEmail: dhabitzahin@gmail.comAbstract. In this study, crumb rubber was used to partially replaced fine aggregate in mortarmixture by 5, 10, 15, and 20 volume percentage (vol%) with untreated and NaOH-treatedcrumb rubber. Thus, the total number of mixtures was 9. The mortars were tested for itsflowability, compressive strength, flexural strength and density. Based on the results,increasing the replacement percentage of fine aggregate by crumb rubber reduced thecompressive strength, flexural strength and density of rubberized mortar but increased theflowability. Meanwhile, the treatment of crumb rubber using NaOH solution improved theflowability, compressive strength and flexural strength. The treatment has minor effect on thehardened density of the rubberized mortar.1. IntroductionDue to the growing number of vehicles, about 1.2 billion tonnes scrap tyres are estimated to produceglobally each year by 2030, with 417 thousand tonnes estimated in Malaysia [1]. Most of scrap tyresare disposed each year and this represents a major concern worldwide. Landfilling of tyres is one ofthe major environmental challenges in Sabah. In fact, the Sabah government has laid out overRM700mil to improve the waste landfilling in the various districts in Sabah. Currently, the research inSabah mainly focused on the application of waste materials such as palm oil fuel ash and rice husk ashin construction materials [2-3]Mohammed B S and Azmi N J [4] reported that higher workability was produced when higherwater to cement ratio was used due to more water available in the rubberized concrete mixes. However,it reduced the density of concrete due to the flocculation of the crumb rubber particles during mixingwhich resulted in the voids formation. The strength was also decreased due to the macro-porosity ofthe rubberized concrete, which associated with large pores and air content [4]. This demonstrates theproperties of crumb rubber that repels and entrap water hence increased the air content.Based on the review of literature by Long et. al. [5], it was established that higher replacementpercentage of fine aggregates with crumb rubber reduced the workability of mortar and concrete. Itwas because of the rough surface of the crumb rubber which entraps the air, consequently, requiremore water to overcome the friction between the crumb rubber and the cement paste. However,Mohammed and Azmi [4] found the opposite with higher replacement percentage of fine aggregate bycrumb rubber increased the workability of the rubberized concrete. The findings were justified by thetendency of the crumb rubber to repel water and entraps air into its surface. Therefore, thejustifications for both reduction and increase of flowability are needed to be confirmed.2nd International Conference on Civil & Environmental EngineeringIOP Conf. Series: Earth and Environmental Science 476 (2020) 012030IOP Publishingdoi:10.1088/1755-1315/476/1/0120302Previous study has shown that the increased of fine aggregate replacement with rubber reduced thedensity of concrete [4]. This is because when rubber was added to the concrete mixes, it increased thepores size and number due to its hydrophobicity properties [4]. High number of pores reduced thedensity since it was later filled with air in dry hardened state, hence lowering the density.Similarly, the strength of rubberized mortar or concrete also reduced when higher replacementpercentage was used. This was due to the lack adhesion or poor bond between crumb rubber and thebinder caused by the surface of crumb rubber [6-9]. This leads to the increase distance of interfacialtransition zone (ITZ) between crumb rubber and the matrix, thus promoting micro-cracks whichincreased in size during strength test [10]. In addition, due to low value of specific gravity, strength,stiffness and load carrying capacity of crumb rubber compared with natural sand, the strength ofrubberized mortar or concrete reduced [1][7][11].Su et al. [12] stated that smaller size crumb rubber reduced the workability due to higher waterabsorption of the rubber particles compared to sand, with values ranging from 4.49% to 10.70%. Thus,it reduced the free water availability for the workability. However, Bisht and Ramana [8] recordedlower water absorption with only 0.3% and claimed that the reduced workability was due to the roughsurface of crumb rubber which increased the friction and high surface area. Therefore, thecontradicting statements by the two authors on the causes of reduction in workability due to crumbrubber as replacement for fine aggregates needed to be investigated.Kashani et al. [13] studied five different treatments for crumb rubber including Cement coating,Silica Fume coating, Sodium Hydroxide, Potassium Permanganate and Sulphuric acid soaking. Alltypes of treatment had minor effect on the workability except for silica fume due to high waterabsorption of silica fume, consequently reduced the workability. Meanwhile, it was found that alltreated crumb rubber had improved the strength of rubberized concrete. For coating method, thestrength was increased due to the formation of additional calcium-silica gel [13]. On the other hand,the treatment using chemical solutions provided better contact surface between crumb rubber and thecement paste, thus increase the strength of the concrete. Kashani et al. [13] only study one replacementpercentage which was 10% of fine aggregate by weight. Hence, the effect of different replacementpercentage of fine aggregate using treated crumb rubber needed to be investigate.Based on the aforementioned previous studies, there are research gaps that needed to be addressed.First, the effects and causes on the fresh and hardened properties of mortar when the percentagereplacement of fine aggregates by crumb rubber is increased should be investigated. Second, toinvestigate on how the treatment of crumb rubber at different replacement percentage improved thefresh and hardened properties of mortar. This paper is, therefore aimed to investigate the abovematters for 5%, 10%, 15% and 20% crumb rubber replacement level treated in Sodium Hydroxidesolution.2. Experiment details2.1. MaterialsThe material used for the mortar mixture Ordinary Portland Cement (ASTM Type 1). Table 1 showsthe physical properties of fine aggregate and crumb rubber. The crumb rubber was treated by soakingin 10 wt% (2.5 molarity) of Sodium Hydroxide (NaOH) solution for 2 hours, washed with water thendried for 24 hours. The pH value of the crumb rubber must be within range of 6 to 8 pH.Table 1. Physical properties of fine aggregate and crumb rubber.Material Fine aggregate Crumb rubberSize, mm 0.6 – 1 0.8 – 1Specific gravity 2.6 0.75Water absorption, % 5 0.022nd International Conference on Civil & Environmental EngineeringIOP Conf. Series: Earth and Environmental Science 476 (2020) 012030IOP Publishingdoi:10.1088/1755-1315/476/1/01203032.2. Mix proportionsThe control design mix used was based on ASTM C109. The water to cement ratio used was 0.45. Thefine aggregate was partially replaced by volume using untreated (as received) and treated crumbrubber with 5 vol.%, 10 vol.%, 15 vol.% and 20 vol.%. The mix proportions are shown in Table 2. Thesample designation is as follows:T-Pr-WC (1)where;T stands for the type of treatment for mortar (M = untreated crumb rubber; T = treated crumbrubber), Pr stands for percentage of replacement (0%, 5%, 10%, 15% and 20% by volume), and WCstands for the water to cement ratio (0.45). For instance, specimen M-5-0.45 stands for mortarcontaining untreated crumb rubber, replacing 5% of fine aggregate by volume and 0.45 water tocement ratio.Table 2.Mix proportion of mortar cube.Specimen w/c Crumbrubber, %Crumbrubber, gCement, g Fineaggregate, gWater, g Additionalwater, gM-0-0.45 0.45 0 0 500 1375 225 68.8M-5-0.45 0.45 5 19.8 500 1306.3 225 65.3M-10-0.45 0.45 10 39.6 500 1237.5 225 61.9M-15-0.45 0.45 15 59.4 500 1168.8 225 58.4M-20-0.45 0.45 20 79.3 500 1010 225 50.5T-5-0.45 0.45 5 19.8 500 1306.3 225 65.3T-10-0.45 0.45 10 39.6 500 1237.5 225 61.9T-15-0.45 0.45 15 59.4 500 1168.8 225 58.4T-20-0.45 0.45 20 79.3 500 1010 225 50.52.3 Test methodsAll specimens were mixed according to ASTM C305 and tested for flowability using ASTM C1437.They were casted in 50mm x 50mm x 50mm mould, demoulded after 24 hours then cured in watercuring tank for 28 days. The cured specimens were tested for compressive strength using ASTM C109,flexural strength using ASTM C348 and measured for hardened density using BS EN 1015-10.3. Results and discussionsTable 3 below shows the results of the flowability, compressive strength, flexural strength andhardened density of the mortar. The increased in results compare to conventional mixture forcorresponding water cement ratio indicated by positive (+) sign in percentage while the decreased inresults indicated by negative (-) sign in percentage.Table 3. Results of flowability, compressive strength, flexural strength and hardened density.MixnumberFlowability,mm+/-,%Compressivestrength,MPa+/-,%Flexuralstrength,MPa+/-,%HardenedDensity,Kg/m3+/-,%M-0-0.45 109 - 32.7 - 6.2 - 2027.2 -M-5-0.45 115 +5.5 31.8 -2.8 6.0 -3.2 2016.8 -0.51M-10-0.45 117 +7.3 30.8 -5.8 5.8 -6.5 2007.2 -0.99M-15-0.45 124 +13.7 29.5 -9.8 5.5 -11.3 1985.6 -2.05M-20-0.45 130 +19.3 27.3 -16.5 5.1 -17.7 1968.8 -2.88T-5-0.45 116 +6.4 34.2 +4.6 6.2 - 2017.1 -0.5T-10-0.45 120 +10.9 33.1 +1.2 6.1 -1.6 2008.2 -0.94T-15-0.45 126 +15.5 32 -2.1 5.7 -8.1 1986 -2.03T-20-0.45 133 +22 29.1 -11 5.2 -16.1 1968.9 -2.882nd International Conference on Civil & Environmental EngineeringIOP Conf. Series: Earth and Environmental Science 476 (2020) 012030IOP Publishingdoi:10.1088/1755-1315/476/1/01203043.1. Flowability of Rubberized MortarFigure 1 shows the flow value of mortar mixes for treated and untreated rubberized mortar. Theflowability of rubberized mixture increased with increasing crumb rubber replacement percentage.This result agreed with research by Mohammed and Azmi [4]. This is due to low water absorption ofcrumb rubber which is 0.02% compared to fine aggregate with 5% (as shown in Table 1). Therefore,there were more water available for the flow in the mixture of the rubberized mortar than the cementmortar.The results also show that the treatment of crumb rubber increases the flowability of the mortar forall level of fine aggregate replacement. The treatment had smoothened the surface of the crumb rubberas shown in Figure 2, thus allowing the mixture to move easier on the surface of crumb rubber. It alsoshows that the structure of treated crumb rubber is similar with the river sand.3.2. Compressive Strength of Rubberized MortarFigure 3 shows the compressive strength results for treated and untreated rubberized mortar. Whenhigher replacement percentage is used, the strength is reduced due to weak bonding between rubberparticles and cement matrix producing micro-cracks as shown in Figure 4. Thus, when thecompressive load was applied, the crack distribution occurred very fast around the rubber particles.On the other hand, it was also observed that the treatment of crumb rubber using NaOH increasedthe strength for all different percentage of replacement. The treatment provides better contact surfacebetween the crumb rubber and the cement matrix. This is due to better bond between the treated crumbrubber and the cement matrix compared with untreated crumb rubber as shown in Figure 4. It showsthat the interfacial transition zone (ITZ) is better for the treated crumb rubber because the distancebetween the rubber particle and the cement matrix is smaller than the untreated crumb rubber. 5% and10% NaOH-treated rubberized mortar have better strength than the control specimen. However, at15% and 20% of NaOH-treated crumb rubber, the strength was lower than the control specimen.Figure 1. Flow value of mortar mixes for treated and untreated rubberized mortar.2nd International Conference on Civil & Environmental EngineeringIOP Conf. Series: Earth and Environmental Science 476 (2020) 012030IOP Publishingdoi:10.1088/1755-1315/476/1/0120305(a) (b)(c)Figure 2. SEM of (a) river sand, (b) treated and (c) untreated crumb rubber particles.Figure 3. Compressive strength results for treated and untreated rubberized mortar.2nd International Conference on Civil & Environmental EngineeringIOP Conf. Series: Earth and Environmental Science 476 (2020) 012030IOP Publishingdoi:10.1088/1755-1315/476/1/0120306(a) (b)Figure 4. SEM of (a) untreated and (b) treated rubberized mortar at 5% of replacement level.3.3. Flexural Strength of Rubberized MortarFigure 5 shows the flexural strength results for treated and untreated rubberized mortar. Similar withthe compressive strength results, the flexural strength decreases as the replacement with crumb rubberincreases. The NaOH-treated crumb rubber improved the flexural strength of the rubberized mortar forall percentages of fine aggregate replacements than untreated crumb rubber. For 5% replacement ofNaOH-treated crumb rubber, the flexural strength is the same as the control specimen.Figure 5. Flexural strength of treated and untreated rubberized mortar.3.4. Hardened Density of Rubberized MortarFigure 6 shows the hardened density results for treated and untreated rubberized mortar. Higherreplacement percentage reduced the hardened density of the mortar. This is due to the lower specificgravity of crumb rubber to be compared with the fine aggregate as shown in Table 1.The treatment of crumb rubber slightly increased the density compared with the untreated crumbrubber. This is due to the better bond produced by the NaOH-treated crumb rubber as shownpreviously in Figure 4.Cement MatrixTreated Crumb RubberUntreated Crumb RubberCement MatrixITZITZ2nd International Conference on Civil & Environmental EngineeringIOP Conf. Series: Earth and Environmental Science 476 (2020) 012030IOP Publishingdoi:10.1088/1755-1315/476/1/0120307Figure 6. Hardened density results for treated and untreated rubberized mortar.4. ConclusionsThe following conclusions have been drawn from this research:1. The flowability of rubberized mortar is increased when the replacement percentage of crumbrubber is increased, for both untreated and treated rubber. The replacement of fine aggregate usingcrumb rubber enhanced the workability in terms of handling, placement and finishing for thetreated and untreated crumb rubber compared with the control mixture.2. However, the density of rubberized mortar is decreased when the replacement percentage of crumbrubber is increase. This is due to the lower specific gravity of crumb rubber to be compared withthe fine aggregate. The treatment did not do much in terms of density. The reduction of density canreduce the load applied in structures.3. Lastly, the strength of rubberized mortar is reduced when higher replacement percentage of crumbrubber is used. However, the treatment of crumb rubber with NaOH improved the strength of themortar, when compared with mortar containing untreated crumb rubber. The application ofrubberized mortar can be used in low strength demand structures. \AcknowledgementThe authors would like to thank University Malaysia Sabah (UMS) for granting this project undercode UMSGreat GUGO346-1/2019.References[1] Mohammed B S, Adamu M and Shafiq N 2017 International Journal of Civil Engineering andTechnology 8(9) 599–615[2] Alias Tudin D Z, Rizalman A N, and Asrah H 2018 E3S Web Conferences 65 InternationalConference on Civil and Environmental Engineering (ICCEE 2018)[3] Arif A, Asrah H, Rizalman A N Dullah S 2019 IOP Conference Series: Materials Science andEngineering[4] Mohammed B S and Azmi N J 2014 Frontiers of Structural and Civil Engineering 8(3) 270–81[5] Long W, Li H, Wei J, Xing F Han N 2018 Journal of Cleaner Production 204 1004–15[6] Yahya Z, Abdullah M M A B, Ramli S N H, Minciuna M G and Abd Razak R 2018 IOPConference Series: Materials Science and Engineering 374(1)[7] Alsaif A, Bernal S A, Guadagnini M and Pilakoutas K 2019 Construction and BuildingMaterials 195 450–58[8] Bisht K and Ramana P V 2019 Construction and Building Materials 194 276–86[9] Ramdani S Guettala A Benmalek M L and Aguiar J B 2019 Journal of Building Engineering 21302–112nd International Conference on Civil & Environmental EngineeringIOP Conf. Series: Earth and Environmental Science 476 (2020) 012030IOP Publishingdoi:10.1088/1755-1315/476/1/0120308[10] Rashad A M 2015 Sustainable Built Environment 47–79[11] Yu Y and Zhu H 2016Materials 9 1–12[12] Su H, Yang J, Ling T, Ghataora G S and Dirar S 2015 Journal of Cleaner Production 91 288–96[13] Kashani A, Ngo T D, Hemachandra P and Haji Mohammadi A 2018 Construction and BuildingMaterials 171 467–73

Properties of cement mortar containing NaOH-treated Crumb rubber as fine aggregate replacement

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Properties of cement mortar containing NaOH-treated Crumb rubber as fine aggregate replacement

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