EXPERIMENTAL INVESTIGATION ON LONG TERM STRENGTH OF BLENDED AND O.P.C. CONCRETES- A COMPARISON

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1 EXPERIMENTAL INVESTIGATION ON LONG TERM STRENGTH OF BLENDED AND O.P.C. CONCRETES- A COMPARISON Raghuprasad P.S. Senior Lecturer, Dept. of Civil Engineering, Dr. T.M.A. Pai Polytechnic, Manipal Dr. A.V. Pradeep Kumar Professor & Head of Civil Engg., J.N.N. College of Engg., Shimoga K. Balakrishna Rao Selection Grade Lecturer Muthanna K.M. M.Tech (Structural Engineering) student, Dept. of Civil Engineering, Manipal Institute of Technology, Manipal ABSTRACT The manufacture of Portland cement is environmentally unfriendly because for each ton of cement produced, approximately the same amount of CO 2, in addition to this, CH 4 and NO, which are major green house gases, are released into the atmosphere are also released into the atmosphere. Investigations have revealed that, replacing part of Portland cement by industrial by-products such as blast furnace slag and fly ash in concrete can contribute significantly to the reduce the emission of these green house gases and also save energy. The main objective of the investigation is an attempt to compare the properties of fresh concrete, strength of hardened concrete produced from four different types of cement namely, blended cement (Portland Pozzolana and Portland Slag Cements i.e. PPC & PSC), and 43 & 53 Grade OPC. Investigations are carried out on M30 grade of concrete with a water-cement ratio of The results of the present investigation clearly indicate that the performance of blended cement concrete is better than that observed for 43 and 53 grade OPC concretes. 1. INTRODUCTION: The responsibility of the construction industry is not only to provide quality construction but also to provide a clean environment (Raghuprasad P.S., 2003). With the increase in industrialization and urbanization, the generation of industrial by-products is increasing. This is not only pollutes the environment but also causes a serious ecological and environmental imbalance due to disposal of industrial by- products. Industrial wastes are creating environmental pollution in one or the other way. These industrial wastes if not taken care, can effect human health and rein the peace of society. Many efforts have been made by construction industry to utilize these industrial wastes in construction and thus reducing the environmental pollution load. Many of the industrial wastes like red mud, fly ash, silica fume and foundry sand finding application in the construction industry. The fly ash, which is an industrial waste of the thermal power station where coal is used as a raw material, is causing havoc. Many people are suffering from respiratory diseases near the areas of thermal power station. Slag is one of the industrial wastes obtained from metallurgical industries (foundries). The slag generated in these foundries is presently used for land filling operations. 384

2 It is important for the society to minimize the volume of industrial wastes and especially that part which has to be disposed. This can be achieved by minimizing the production of industrial wastes, cleaner production as well as recycling and reuse of recycled materials in construction. The replacement of Portland cement by fly ash and slag reduces the volumes of Portland cements used, which is a major benefit. Besides fly ash and slag other waste materials like silica fume, rice husk ash and metakaolin may also be used as pozzolanic materials in the manufacture of environmentally friendly blended cement. 2. OBJECTIVES OF THE STUDY The main objective of the this study is to present laboratory investigations relating to concrete produced from four different types of cements namely, blended cements (PPC, PSC), OPC 43 and 53 grade OPC. An attempt has been made to compare different properties like setting time, workability, strength etc. of M30 concrete made with four different types of cement. 3. EXPERIMENTAL PROGRAM The experimental program has been divided in to three phases: Tests on cement and other ingredient materials Tests on fresh concrete Tests on hardened concrete. 3.1 Materials used: Cement: Factory blended, blended cement (PPC), 43 and 53 OPC are used throughout this investigation. The physical properties and compressive strength of concrete is found out as per B.I.S. specifications and listed in Tables 1and Aggregates: Locally available river sand with specific gravity 2.53 and fineness modulus 2.91 and locally available quarried and crushed granite stones of 20 mm and down size with specific gravity 2.61 and fineness modulus 7.91 were used as fine and coarse aggregates respectively through out the investigation in all concrete mix. 3.2 Specimen details: The specimens used for the test included concrete cubes of 150 mm x 150 mm x 150 mm for compression test, concrete cylinders of 150 mm x 300 mm (depth) for split tensile test and prisms of 100 mm x 100 mm x 500 mm for flexural test. Three specimens were tested for the required age and the average value was taken. The tests were conducted for 120, 150 and 180 days. The specimens were designated as AM 30, BM 30, CM 30 and DM 30 for concrete of grade M30 made with PPC, PSC, 43 and 53 grades OPC respectively. 3.3 Tests on fresh concrete: On fresh concrete, the tests related to workability measures such as slump test, compaction factor test and Vee-Bee Consistometer test were conducted as per BIS specifications and the results were tabulated in Table

3 3.4 Tests on Hardened concrete: On hardened concrete, compression test, split tensile test and flexural test were conducted as per BIS specifications and results were listed in Tables RESULTS AND DISCUSSIONS: 4.1 Setting time of cement: The setting time of cement both initial and final is reported in Table 1. From the above information it is evident that, the setting time both initial and final of blended cement gets delayed as compared to 43 and 53 grade OPC. This delayed time is due to the addition of supplementary cementing materials (SCM s) in blended cement. 4.2 Workability of concrete: The results of workability tests are reported in Table 3. From the observed values it is evident that the workability performance of blended cement concretes is better than that of 43 and 53 grade OPC concretes. Mortars and concrete (Kameswara Rao, 2000) with fly ash addition shows improved workability. This is due to the increased fineness of fly ash particles acting as ball bearings for moving the ingredients. Literature (Owens, 1979 & 1980) cites that the workability of OPC concrete can be improved when part of the OPC is replaced by fly ash. The extent of improvement depends on the fineness and carbon content of the fly ash as well as on the original mixes proportions. According to Owens, the finer the fly ash the more be the workability. 4.3 Compressive strength of concrete: The results of compressive strengths are reported in Table 4 and variation with age is shown in Fig. 1. It has been observed that the compressive strength of blended cement concretes at later ages, that is 120, 150 and 180 days there is a considerable increase in compressive strength of blended cement concretes compared to that of other two types of conventional concretes. It is quoted in the literature (Kaushik, 2000) that the increase in compressive strength in the case of blended cement is higher at longer periods. However, further investigation in this regard is needed as far as the blended cements is concerned used in the present study. 4.4 Split tensile strength of concrete: The results of split tensile strength are listed in Table 5 and variation with age is shown in Fig. 2. From the results it is noted that the split tensile strength of blended cement concretes at 120, 150 and 180 days, the variation in split tensile strength of all the four types of concrete is marginal. 4.5 Flexural strength of concrete: The results of flexural strength of concrete are presented in Table 6 and variation with age is shown in Fig. 3. It has been observed that the flexural strength of blended cement concrete at 386

4 120, 150 and 180 days there is an increase in flexural strength of blended cement concrete than that of other two types of conventional concretes. 5. CONCLUSIONS Based on the present study the following conclusions are drawn. REFERENCE Setting time both initial and final of blended cement is generally gets delayed. This may be attributed to the slow pozzolanic reaction. This delayed setting time can be of benefit during concreting, especially in hot weather concreting. For a given slump, concrete with blended cement/ SCM s are easier to place and compact when compared to OPC concrete. Workability is maintained relatively longer. The initial rate of gain of strength of blended cement concrete is lower which is mainly due to the slow pozzolanic reaction, but the strength development continues for longer periods beyond 28 days. From the test results it is evident that the gain in compressive strength of blended cement concrete is more than that of other two types of conventional concrete at later ages i.e., 120,150 and 180 days. However, further investigations beyond 180 days are needed to arrive at a definite conclusion as far as this increase in strength is concerned. 1. Muthanna.K.M. An Experimental Investigation Different Type of Blended and OPC Comparison, M.Tech Dissertation Work, submitted to MAHE, for the award of M.Tech Degree, Kameswara Rao B. Characteristics of fly ash and its use in different concrete works in different environments, Proceedings of Seminar on Eco-friendly Blended Cement for Economical and Durable in the New Millennium, 18 th -19 th Feb., 2000, Mumbai. 3. Owens P.L. Fly ash and its usage in concrete, CONCRETE, Vol.13, No. 7, Oct.1979, pp Owens P.L. Pulverised fuel ash-part 2, CONCRETE, Vol.14, No. 10, Oct.1980, pp Yamamoto Y. and Kobyashi Use of mineral fines in high strength concrete-water requirement and strength, International, Vol. 4, No. 7, July 1982, pp Kaushik S. K., Composite cements for economic and durable concrete in the new millennium, Proceedings of Seminar on Eco-friendly Blended Cement for Economical and Durable in the New Millennium, 18 th -19 th Feb. 2000, Mumbai. 7. Reddi S.A., Blended cements and SCM in construction, Proceedings of Seminar on Eco-friendly Blended Cement for Economical and Durable in the New Millennium, 18 th -19 th Feb. 2000, Mumbai. 8. Mukherji M.K. and Aithal D.D., An Environment friendly approach by way of blended cement A Review, Proceedings of Seminar on Eco-friendly Blended Cement for Economical and Durable in the New Millennium, 18 th -19 th Feb., 2000, Mumbai. 387

5 Table 1 Properties of cement Sl.No. Particulars Normal consistency Specific gravity Setting time (min.) Fineness (cm 2 /gm) % Initial Final 1 PPC PSC Gr OPC Gr OPC Table 2 Compressive strength of cement mortar Compressive Strength, MPa Sl.No. Particulars 3 Days 7Days 28 days 1 PPC PSC Gr OPC Gr OPC Table 3 Results of workability tests Sl.No. Type of Slump, mm Compaction Factor Vee-Bee degrees 1 AM BM CM DM Table 4 Average cube compressive strength Sl.No. Type of 120 Days 150 Days 180 Days 1 AM BM CM DM Table 5 Average split tensile strength of concrete cylinders Sl.No. Type of 120 Days 150 Days 180 Days 1 AM BM CM DM

6 Table 6: Average flexural strength on concrete prisms Sl.No. Type of 120 Days 150 Days 180 Days 1 AM BM CM DM Compressive strength(mpa) Compressive strength, MPa AM30 BM30 CM30 DM30 Aging (Days) Fig 1. Average compressive strength Flextural strength(mpa) Flextural strength, MPa AM30 BM30 CM30 DM30 Aging(DAYS) Fig 2. Average Splitting Tensile Strength 389

7 Flextural strength(mpa) Flextural strength, MPa AM30 BM30 CM30 DM30 Aging(DAYS) Fig 3. Average Flexural Strength 390