290 American Scientific Research Journal for Engineering, Technology, and Sciences (ASRJETS) ISSN (Print) 2313-4410, ISSN (Online) 2313-4402 © Global Society of Scientific Research and Researchers http://asrjetsjournal.org/ Experimental Research on Natural Pozzolan as Cement Replacement Tin Ni Ni Koa*, Dr. Nilar Ayeb a,bDepartment of Civil Engineering, Mandalay Technological University, Myanmar aEmail: nikoye01@gmail.com bEmail: dnilaraye@gmail.com Abstract This paper presents the properties of motor and concrete with natural pozzolan as partial replacement of cement. In this research, natural pozzolan from Twin Taung, Sagaing Region and local cement (Crown) are used. Firstly, chemical composition of natural pozzolan and Crown cement are analysed. And then the physical properties of local materials used in this research are determined according to ASTM procedure. Partial replacement percentages of pozzolan are considered 10%, 20%, 30% and 40%.The strength of motor and concrete with natural pozzolan (0%,10%, 20%, 30%, and 40%) is tested at 7 days,28 days and 91days. From the trial mix design, the water-cement ratio (0.555) is obtained by using the least square method. To get target strength (4000 psi), by using water cement ratio (0.555) and 68% of maximum aggregate size (20 mm), the concrete mix proportion (1:1.9:3) is obtained.The compressive strength of concrete with various percentages of natural pozzolan at 60 days and 91 days are more than 7 days and 28 days strength. Therefore, it can be concluded that natural pozzolan may be used as cement replacement material when it is not required high strength performance in structures. Keywords: natural pozzolan; physical properties; partial replacement; mortar; concrete; strength. 1. Introduction Cement is the most essential requirement in concrete mix for the constructions of structure all over the world. So, every construction in all countries needs few or much cement. However, rural area in developing countries, because of transportation difficulties and high relative cost is difficult to achieve much cement. ------------------------------------------------------------------------ * Corresponding author. http://asrjetsjournal.org/ American Scientific Research Journal for Engineering, Technology, and Sciences (ASRJETS) (2018) Volume 44, No 1, pp 290-301 291 Pozzolan may often be cheaper than the Portland cement. Their chief advantage lies in slow hydration and therefore low rate of heat development. So, a partial replacement of Portland cement by the pozzolan is used in mass concrete construction. Under the strong contemporary demand for modern and environmentally friendly materials, natural pozzolan can be proved to be such a material and several researchers have focused their research efforts in using it as a partial replacement in the manufacture of mortar and concrete[4]. The objectives of the study are to know the compressive and tensile strength of mortar with different percentages of natural pozzolan as cement replacement and to evaluate experimentally the effects of partial replacement of cement with pozzolan on the compressive strength of concrete. 2. Pozzolan Pozzolan is defined as a siliceous and aluminous materials, which in itself possess little or no cementitious properly, but will in finely divided form and in the present of moisture chemically react with calcium hydroxide at ordinary temperature to form compounds possessing cementitious properties. Pozzolan can be divided into two groups: natural pozzolan such as volcanic ash and diatomite, and artificial pozzolan such as claimed clay, pulverized fuel ash, and ash from burnt agricultural waste. Many plant ashes have high silica content and are therefore suitable as a pozzolan. Natural pozzolan mixed with lime were used in concrete construction long before the invention of Portland cement because of their contribution to the strength of concrete and mortar. Today, natural pozzolan are used with Portland cement not only for strength, but also for economy and beneficial modification of certain properties of fresh and hardened Portland cement concrete. Generally, pozzolans contain 50% to 70% silica (SiO2), 20% to 35% alumina (Al2O3), 3% to 10% hematite (Fe2O3), 2% to 7% lime (CaO), 1% to 7% magnesium oxide (MgO), and 1% to 5% potassium oxide (K2O). Chemical composition of natural pozzolan is shown in Table 1. Fineness value of pozzolan is 29%. The maximum value for fineness is 34% to be used as cement replacement. The total composition percentages of silica, alumina, ferric oxide, calcium oxide and sulphur trioxide of natural pozzoaln are 89.08%. This test result is within the acceptable range. It conforms to the requirements of ASTM C 618-03 Class N and its appearance is yellowish colour. Therefore, Twin Taung pozzolan can be used as cement replacement. Then, generally the pozzolan content is limited to between 15 and 40 percent by weight of cement. [2] Table 1: Chemical composition of pozzolan (Twin Taung) Oxide Content (%) Class N Acceptable ranges Silica (SiO2) 58.23 Total (%) 89.08 Min: 70 Alumina (Al2O3) 27.98 Ferric Oxide (Fe2O3) 2.87 Calcium Oxide(CaO) 4.28 - Sulphur Trioxide(SO3) 0.32 Max: 4 American Scientific Research Journal for Engineering, Technology, and Sciences (ASRJETS) (2018) Volume 44, No 1, pp 290-301 292 2. Testing of materials used in this research In this study, chemical composition and the physical properties of Crown cement with replacement percentage of pozzolan are tested. Then, the physical properties of fine aggregates and coarse aggregates are tested. Test results are shown in Table 2 to Table 8. The properties of the materials are within the standard limit. Table 2: Chemical composition of local crown cement Oxide Content (%) Approximate Composition Limits of Portland Cement (%) Calcium Oxide (CaO) 61.93% 17-25 Silica (SiO2) 20.08% 3-8 Alumina (Al2O3) 5.26% 0.5-6.0 Ferric Oxide (Fe2O3) 3.15% 60-67 Manganese Oxide (MgO) 3.39% 0.1-4.0 Sulphur Trioxide (SO3) 2.43% 1-3 Others 1.73% 1 Loss 2.03% 2 Total 100 Table 3: Physical properties of local crown cement Sr No. Properties Result Value ASTM Standard range 1 Specific gravity 3.15 3.1 to 3.25 2 Finess Modulus 6.5% <10% 3 Normal Consistency 27% 26% to33% 4 Setting time (min) initial 53 min >45 min final 142 min <375 min 5 Soundness 0.7 mm <10 mm Table 4: Setting time of crown cement with replacement % of pozzolan Replacement % of pozzolan 0% 10% 20% 30% 40% Initial Setting Time (min) 53 72 80 85 97 Final Setting Time (min) 142 152 180 185 192 American Scientific Research Journal for Engineering, Technology, and Sciences (ASRJETS) (2018) Volume 44, No 1, pp 290-301 293 Table 5: Normal consistency of crown cement with different replacement % of pozzolan Replacement Percentage of Pozzolan 0% 10% 20% 30% 40% Normal Consistency 27% 26.5% 26% 25.5% 25.3% Table 6: Soundness of crown cement with different replacement percentages of pozzolan Replacement Percentage of Pozzolan 0% 10% 20% 30% 40% Soundness (mm) 0.7 0.5 0.3 0.2 0.1 Table 7: Physical properties of fine aggregates Sr No. Properties Result Value ASTM Standard range 1 Specific gravity 2.66 2.5 to 2.9 2 Finess Modulus 2.18 2 to 3.1 3 Water Absorption 1.01 <3% Table 8: Physical properties of coarse aggregates Sr No. Properties Result Value ASTM Standard range 1 Specific gravity 2.74 2.5 to 2.9 2 Finess Modulus 7.17 6 to 8 3 Water Absorption 0.73% <3% 3. Testing of mortar Mortar is a mixture of cement and sand in a specified ratio on which the strength of the mortar depends. Mortar is a workable paste used to bind building blocks such as stones, bricks, and concrete masonry units together, fill and seal the irregular gaps between them, and sometimes add decorative colours or patterns in masonry walls. American Scientific Research Journal for Engineering, Technology, and Sciences (ASRJETS) (2018) Volume 44, No 1, pp 290-301 294 Mortar’s adhesive characteristics vary, depending on the amount of water added to the mixture [3]. Strength tests are made to check on the quality of mortar. The following tests are performed. 3.1. Compressive Strength Test For the compressive strength test, water-cement ratio can be determined by using the flow table test. Water content for other cements is that sufficient to obtain a flow of 110 ± 5 % in 25 drops of the flow table [1]. Table 9 shows the flow table test results of Crown cement and with replacement percentage of natural pozzolan. Table 9: Flow of crown cement with different replacement percentages of pozzolan Replacement Percentage of Pozzolan Flow (%) 0% 106 10% 109.2 20% 110.6 30% 112.1 40% 114.6 According to the results of flow table test, the values of normal consistency decreases and the values of slump will be increased with the increase of replacement percentage of pozzolan. For the compressive strength test, cement and standard sand are taken in ratio of 1:2.75. Two-inch (50-mm) test cubes are compacted by tamping in two layers. The cubes are cured one day in the moulds and stripped and immersed in water until tested. The temperature of the air in the vicinity of the mixing slab, the dry materials, moulds, base plates and mixing bowl, shall be maintained between 73.5 ± 5.5°F. The temperature of the mixing water, moist closet or moist room, and water in the storage tank shall be set at 73.5 ± 3.5°F. The relative humidity of the laboratory shall be not less than 50%[1]. Water-cement ratio for compressive strength test is 0.5.Compressive strength test results of mortar with various replacement percentage of pozzolan are shown in Table 10 and Figure 1 describes the comparison of these results. Table 10: Compressive strength test of mortar with different replacement percentages of pozzolan Replacement % of Pozzolan Compressive Strength, psi 7 days 28 days 91 days 0% 3355 4124 4383 10% 2641 3285 3453 20% 2513 3039 3078 30% 2009 2894 2991 40% 1855 2414 2419 American Scientific Research Journal for Engineering, Technology, and Sciences (ASRJETS) (2018) Volume 44, No 1, pp 290-301 295 Figure 1: Comparison of compressive strengths of mortar with cement replacement percentage of pozzolan 3.2. Tensile Strength Test The objective of this test is to determine the tensile strength of the (1:3) cement-mortar composed of the cement and fine aggregates. The percentage of water is determined by the following equation. Y = 2/3[p/(n+1)] + K (1) Here, Y = water required for the sand mortar, % P = water required for neat cement paste of normal consistency, % N = number of parts of sand to one of cement by weight, K = a constant which for the standard sand has the value 6.5. Water-cement ratio for tensile strength test is 0.44. The cubes are cured one day in the moulds and stripped and immersed in water until tested. The temperature of the mixing water, moist closet or moist room, and water in the storage tank shall be set at 73.5 ± 3.5 °F (23.0 ± 2.0°C) [1]. The relative humidity of the laboratory shall be not less than 50%.The cubes are then tested under a compression testing machine after 7, 28 and 91 days of immersion. At each period interval, three cubes are tested and average tensile strength of the three is taken as the tensile strength. Tensile strength test results of mortar with various replacement percentage of pozzolan are shown in Table 11 and Figure 2 describes the comparison of these results. Table11: Tensile strength test of mortar with different replacement percentages of pozzolan Replacement % of Pozzolan Tensile Strength, psi 7 days 28 days 91days 0% 248 357 360 10% 214 320 343 20% 207 284 302 30% 189 253 283 40% 176 192 209 0 1000 2000 3000 4000 5000 0% 10% 20% 30% 40% co m pr es si ve st re ng th (p si ) replacement % of pozzolan 7 days 28 days 91 days American Scientific Research Journal for Engineering, Technology, and Sciences (ASRJETS) (2018) Volume 44, No 1, pp 290-301 296 Figure 2: Comparison of tensile strengths of mortar with cement replacement percentage of pozzolan 4. Concrete Concrete has been one of the most widely used building materials because of its compressive strength, resistance to water, and its ability to be easily formed and placed according to need, many advanced construction techniques and materials are required. Concrete is any product or mass made by the use of a cementing medium [3]. Generally, this medium is the product of reaction between hydraulic cement and water. The quality of concrete depends on materials, mix design, production, transporting, placing and curing. The main constituents of concrete are cement, fine and coarse aggregates. Nowadays, concrete is made with several types of cement and also containing pozzolan, fly ash, blast-furnace slag, micro-silica, additives, recycled concrete aggregate, admixtures, polymers, fibres and so on. Pozzolan can be used as partial replacement of cement in concrete without compromising strength [3]. 4.1. Calculation of Trial Mixes Design The required properties of hardened concrete are specified by the designer of the structure and the properties of fresh concrete are governed by the type of construction and by the techniques of placing and transporting. These two sets of requirements make it possible to determine the composition of the mix, taking also account of the degree of control exercised on site. Mix design can, therefore, be defined as the process of selecting suitable ingredients of concrete and determining their relative quantities with the purpose of producing an economical concrete which has certain minimum properties, notably workability, strength and durability [6]. In order to obtain a satisfactory mix, the estimated proportions of the mix must be checked by making trial mixes and, if necessary, make appropriate adjustments to the proportions until a satisfactory mix has been obtained. The American (ACI-C211) method of mix design for normal weight aggregate concrete is used. ACI-C211 also covers heavy weight and mass concrete. In this study, calculation of trial mix design will be considered with two cases. They are 73% of max: aggregate size (25mm) and 68% of max: aggregate size (20mm) with three water- cement ratio. Batch weight per cubic yard of fresh concrete of trial mix design for desired strength 3000psi is shown in Table 12. 0 50 100 150 200 250 300 350 400 0% 10% 20% 30% 40% Te ns ile st re ng th (p si ) replacement % of pozzolan 7 days 28 days 91 days American Scientific Research Journal for Engineering, Technology, and Sciences (ASRJETS) (2018) Volume 44, No 1, pp 290-301 297 Table 12: Batch weight per cubic yard of fresh concrete Item Coarse Aggregate 73% Coarse Aggregate 68% Max agg;size 25mm 20mm Water-cement ratio 0.55 0.6 0.5 0.55 0.6 0.5 Water(lb/yd3) 350 350.5 349.5 361.5 362.5 361.5 Cement(lb/yd3) 591 542 650 613.6 562.5 675 Sand, (lb/yd3) 1098 1146.5 1039.6 1156.8 1207 1096 Aggregate(lb/yd3) 1971 1971 1971 1836 1836 1836 Total Weight (lb/yd3) 4010 4010 4010 3968.3 3968 3968.5 Unit Weight of Concrete (lb/ft3) 148.5 148.5 148.5 147 147 147 Slump of fresh concrete are determined. Strength tests are made to check on the quality of concrete. The average compressive strength of each trial mix design is tested at 7 and 28 days. The specimens are tested under a compressive axial load. The test results are shown in Table 13 and illustrated in Figure 3. Table 13: Compressive strength of trial mix Aggregate volume % Water –cement ratio Compressive strength(psi) 7 days 28 days 73%(max 1in size) 0.5 2807 4140 0.55 2637 3743 0.6 2161 3232 68%(3/4 in size) 0.5 3828 4905 0.55 3119 3828 0.6 2570 3516 Figure 3: Compressive strength of concrete (by using method of least square) 0 2000 4000 6000 0.4 0.45 0.5 0.55 0.6 0.65 C om pr es si ve S tre ng th , p si water-cement ratio 7 days (agg : 68% ) American Scientific Research Journal for Engineering, Technology, and Sciences (ASRJETS) (2018) Volume 44, No 1, pp 290-301 298 The relation between compressive strength and water to cement ratio is calculated by using least square method and shown in Figure 3. From the trial mix design results, it is found that the 7 days and 28 days concrete strength of 68% aggregate volume is higher than 73% aggregate volume. According to Table 13, the maximum compressive strength is obtained from trial mix design with water-cement ratio 0.5 and maximum aggregate volume 68%. 4.2. Calculation of Field Mix Design By using trial mix design data, the optimum value of w/c (0.555) and 68% of maximum aggregate size (20mm) is obtained for the target compressive strength (4000 psi) from figure 3. And then the field mix design is calculated and batch weight per cubic yard of fresh concrete for field mix design is shown in Table14 and slump test of fresh concrete are presented in Table 15. And then, compressive strength test results are described in Table16 and Figure 4. Table 14: Batch weight per cubic yard of fresh concrete for field mix design Replacment % of Pozzolan Wt: of Unit (lb/yd3) Water-cement ratio Cement (lb) Pozzolan (lb) Sand (lb) Aggregates (lb) Water (lb) 0% 608 - 1162.36 1836 362 0.555 10% 547.2 60.8 1162.36 1836 20% 486.4 121.6 1162.36 1836 30% 426.5 182.4 1162.36 1836 40% 364.8 243.2 1162.36 1836 Table 15: Slump test result of fresh concrete for field mix design Replacement Percentages of Pozzolan 0% 10% 20% 30% 40% Value of Slump (in) 3.15 3.35 3.74 3.86 3.94 American Scientific Research Journal for Engineering, Technology, and Sciences (ASRJETS) (2018) Volume 44, No 1, pp 290-301 299 Table 16: Compressive strength test result of concrete with replacement percentages of pozzolan Replacement Percentages of Pozzolan Compressive Strength, psi 7 days 28 days 60 days 91 days 0% 3317 4083 4154 4310 10% 2297 2637 3020 3445 20% 2042 2510 2807 2878 30% 1730 2382 2396 2453 40% 1446 1510 2056 2183 Figure 4: comparison of compressive strengths of concrete with replacement percentage of pozzolan 5. Discussion Local product Crown cement and local materials such as fine aggregates and course aggregates are used in this research. Local available pozzolan (Twin Taung ) is considered as cement replacement material. Physical properties of materials are tested according to the ASTM procedures and the result values are within the allowable limit. According to Table 4, the initial and final setting time of pozzolan as cement replacement are slower than that of cement alone. Therefore, pozzolan can be used as the retarder. In Table 5, it is found that the more percentage of pozzolan as cement replacement, the less value of normal consistency. So, percentages of flow and slump values are high and then water to cement ratio can reduce for mix design. From Table 6, the percentage of pozzolan as cement replacement is increased, the value of soundness is decreased. Therefore, expansion can decrease with the aid of pozzolan. According to the test results, the compressive strength of the mortar with replacement percentages of natural pozzolan 0%, 10% and 20% reaches to the standard limit at 7 days strength 2500 psi of mortar with pure cement and then gradually decreases at other percentages. It is found that 28 days and 91 days strength are not different obviously. In this research, the tensile strength of mortar with 0 1000 2000 3000 4000 5000 0% 10% 20% 30% 40% C om pr es si ve s tre ng th (p si ) Replacement % of pozzolan 7 Days 28 Days 60 Days 91 Days American Scientific Research Journal for Engineering, Technology, and Sciences (ASRJETS) (2018) Volume 44, No 1, pp 290-301 300 replacement 10%, 20% and 30% are within the 5% to 10% of the compressive strength of cement alone. Moreover, it is observed that 10% pozzolan replacement in concrete 28 days compressive strength is nearly 65.9% of pure cement concrete strength. Compressive strength of concrete with various percentages of natural pozzolan at 60 days and 91 days are more than 7 days and 28 days strength. 6. Conclusions The following conclusions may be drawn from the research. 1. The more percentage of pozzolan as cement replacement, the higher the value of slump and the more workable. 2. Pozzolan may be used as the retarder because of increasing of setting time with various percentages of pozzolan as cement replacement. 3. The more percent of pozzolan as cement replacement, the less value of soundness. Therefore, expansion will be decreased. 4. The pozzolan may be used as the cement replacement up to 30% by weight of cement for mortar. 5. It is observed that (10%) pozzolan replacement in concrete at 28 days compressive strength is nearly 65% of pure cement concrete strength. 6. The natural pozzolan is suitable for low cost building construction and large concrete project when it is not required high strength performance in structures. Acknowledgements The author would like to acknowledge the support and encouragement of Dr. Sint Soe, Rector of the Mandalay Technological University. The author would like to express her heartfelt thanks to her head of department Dr. Nilar Aye, Professor and Head of Civil Engineering Department, Mandalay Technological University, for her kind support, guidance and help. The author would like to express her heartfelt gratitude to all staffs for their supports in this reserch. Finally, the author wishes to express her heartfelt thanks to her family, especially her parents and all other persons for their supports and encouragements to attain her destination without any trouble. References [1]. ASTM, 1975. Annual Book of ASTM Standards. [2]. M. R., Rixom, 1978. Chemical Admixtures for Concrete. American Scientific Research Journal for Engineering, Technology, and Sciences (ASRJETS) (2018) Volume 44, No 1, pp 290-301 301 [3]. A. M Nevile and Brooks. J. J., 1990. Concrete Technology [4]. Mohan Kaila, 1996. Civil Engineering Materials, Sixth Editions. [5]. Irving Kett, “Engineering Concrete: Mix Design and Test Methods”, Concrete Technology Series, (1999) [6]. U Nyi Hla Nge, “Essential of Concrete Inspection, Mix Designs and Quality Control”, Refresher Course for Engineers and Technicians, 1st Edition (2008) [7]. Thwe Thwe Win, (2016), Experimental Research on Natural Pozzolan on Concrete Production