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1 International Journal of Advanced Scientific and Technical Research Issue 4 volume 2, March-April 214 AN INVESTIGATION ON FLY ASH BLENDED CEMENT CONCRETE USING SEA WATER P. Krishnam Raju 1, V. Lakshmi 2, S. Bhanu Pravallika 3 1 Research Scholar, Department of Civil Engineering, Jawaharlal Nehru Technological University Kakinada Kakinada, Andhra Pradesh, India M: Assistant Professor of Civil Engineering, Department of Civil Engineering, Jawaharlal Nehru Technological University Kakinada Kakinada, Andhra Pradesh, India M: Post Graduate Student, Department of Civil Engineering, Jawaharlal Nehru Technological University Kakinada Kakinada, Andhra Pradesh, India M: ABSTRACT This investigation was aimed at adoption of sea water both for mixing and curing concrete in the construction works in place of the potable water due to its scarcity on the planet Earth. Two concrete mixes viz, M2 and M25 Grades using Ordinary Portland cement (OPC) of 53 Grade blended with 25% Fly ash were considered. As per the Guide lines of concrete mix proportioning (revised) a slump of 1 to 15mm was adopted for design mixes. The mixes were prepared with Potable water mixing and Sea water curing & Sea water mixing and Sea water curing. A total of 54cube, 54cylinder and 54beam specimen were cast for both the mixes and exposed to 7days, 28days and 9days period of curing in order to study the compressive strength behaviour, modulus of rupture and flexural strength. The reference concrete was prepared with the respective mix proportions using potable water for mixing and also for curing. The study reveals that there was no reduction in compressive strength at 28 days and beyond due to mixing of sea water and also due to mixing and curing with sea water compared to its target strength. Key words:fly ash; compressive strength; target strength. Corresponding Author: P. KrishnamRaju R S. Publication, rspublicationhouse@gmail.com Page 849

2 International Journal of Advanced Scientific and Technical Research Issue 4 volume 2, March-April 214 INTRODUCTION The concrete due to its versatility is famous as an in-situ product for construction. Varieties of cements are available in the market for construction purpose and most common and famous one is Ordinary Portland cement. About one tonne of carbon dioxide emissions would be produced during manufacturing of equivalent quantity of cement. The Fly ash may be one of the replacements to Ordinary Portland cement, not completely, but up to an optimized percentage. Fly ash is produced from Thermal Plants as a waste product and its disposal is one of the issues for environmentalists as dumping causes severe environmental problems. The utilization of Fly ash, instead of disposing it as a waste material, can be utilized as a partial replacement to cement economically and effectively. Fly ash concretes have been known to be chloride resistant than Ordinary Portland cement concretes and hence result in improvement of its strength and durability characteristics. The other important constituent in making concrete is water. It was estimated that world s fresh water bodies are only 2.5 percent and balance constitutes of sea water. UN predicted 5 Billion people will be in short of drinking water. Potable water is a scarce commodity now on the planet earth. Day by day the water levels are in a depleting situation due to its abnormal usage and other environmental effects. A stage may be arrived that potable water may not reach the common man even for drinking purpose. People are habituated procurement of water regularly for their drinking needs as they are not relying upon ground water or well water due to their health consciousness. It is now critical, unless various alternative means to Potable water are explored in the construction. Possibility of usage of sea water in concrete is one and to be studied. Lot of marine infra-structure being established along the coast, where sea water is available at least cost. The types of structures built in marine environment are jetties, berths, break waters and buildings etc., which are directly in contact with or subjected to sea water. Some studies were already done internationally on concrete by mixing and curing of sea water. The results indicated that there is a gain in strength initially and decrease of strength over longer period. Most of the studies were done for nominal concrete mixes with low strength. In the present study, Ordinary Portland cement concrete with 53 Grade replaced with 25% Fly ash was adopted. Concrete grades of M2 and M25 design mixes with a slump in between 1 to 15mm were considered in the study. Two exposure conditions for each of these grades were studied. The exposure conditions are Potable water mixing and sea water curing (PM&SC) and Sea water mixing and sea water curing (SM&SC). A Reference concrete mix for the said two grades was also cast for comparison of the compressive strength behavior, modulus of rupture and flexural strength behavior. The specimens required for the above experimental investigation were cast and cured for 7 days, 28 days and 9 days so as to study the performance of strength. According to IS 456:2, mixing or curing of concrete with sea water is not recommended because of presence of harmful salts. Under unavoidable circumstances sea water may be used for mixing or curing in plain concrete with no embedded steel after having given due consideration to possible disadvantages and precautions including use of appropriate cement system. The same publication also specified the minimum Grades of plain concrete and reinforced concrete to be adopted as M2 and M3 respectively when the concrete is used in sea water or exposed directly along the sea coast. LITERATURE REVIEW Few studies were conducted earlier on effect of mixing and curing of sea water on concrete. Studies conducted by Marthong and Agrawal on effect of fly ash additive on R S. Publication, rspublicationhouse@gmail.com Page 85

3 International Journal of Advanced Scientific and Technical Research Issue 4 volume 2, March-April 214 concrete properties reported that the compressive strength of concrete increases with the Grade of cement used and by using 2% fly ash content is closer to OPC concrete at the age of 9 days. A study conducted by SuvarnaLathaet. al. on estimation of GGBS and HVFA strength efficiencies in concrete with age reported that there is an increase in the compressive strength for different concrete mixes made with GGBS and HVFA replacement mixes. Falah M. Wegian (21) investigated the effects of mixing and curing concrete with sea water on the compressive, tensile, flexural and bond strengths and reported that there are increases of strengths of concrete mixed and cured in sea water at early ages and a definite decrease for ages more than 28 days and up to 9 days. Moinul Islam et al (212) reported that the compressive strength loss of about 1% when the concrete specimens made and cured with sea water compared to plain water mixed and cured concrete. An investigation of salinity effect was conducted by AkinsolaOlufemi Emmanuel et al (212) on compressive strength of reinforced concrete and reported that the sample cast and cured with ocean and lagoon water slowly increases in its strength but lower when compared with fresh water reinforced concrete element and recommended rich mix other than 1:3:6 and 1:3:5. Influence of salt water on compressive strength of concrete was studied by Akinkurolere et al (27) and reported that the mixing and curing concrete with salt water increases the compressive strength rapidly and the strength was still increasing at 28 days. E. M. Mbadike et al (211) investigated the effect of salt water in the production of concrete and reported 8% strength reduction. RetnoSusilorini et al (25) reported on the performance of early age concrete with sea water curing of 7days and 14 days is higher than those cured by plain water in respect of its compressive strength. EXPERIMENTAL WORK Two design mixes viz M2 & M25 using Ordinary Portland cement with 25% replacement of Fly ash were carried out for the study as per Concrete mix proportioning Guidelines. Specimens cast using potable water and also sea water was cured in sea water for a period of 7, 28 and 9 days before testing its compressive strength, split tensile strength and flexural strength. Concrete cubes of mm³ of standard size were used for compressive strength (ffc) study. Concrete cylinders of 15 X 3mm² and concrete beams of mm³ were adopted for the study of split tensile strength (ffs) and flexural strength (ffb) respectively. Ordinary Portland cement, with 53 Grade standard brands confirming to IS: 12269:1987 with a specific gravity of 3.15 and at normal consistency of 29% was used for the study. The fine aggregate used in the study was of natural river sand conforming to grading zone-ii of IS: 383:197. Graded granite metal coarse aggregate of nominal maximum size of 2mm was adopted in the study. Potable water or drinking water as available in the laboratory and sea water obtained nearby source in Kakinada were taken in the study. An admixture of standard make conforming to IS: 913:1999 was used in order to make concrete to achieve required slump. A standard deviation value of 4 was assumed to calculate target mean strength at 28 days. Necessary trail mixes were carried out to achieve the required slumps etc. The concrete mix proportions as adopted are tabulated in Table-1. The same mix proportions were used for concrete cast with sea water also since the specific gravity of sea water is very close to the potable water. The mix designations and number of specimens cast for various strengths are presented in Table-2. The chemical composition of Fly ash obtained from the source is given in the Table-3. R S. Publication, rspublicationhouse@gmail.com Page 851

4 International Journal of Advanced Scientific and Technical Research Issue 4 volume 2, March-April 214 Design Mix W/C ratio Table1.Concrete Mix Proportions (per Cu.m) Water (lit) Cement (Kg) Fly ash (Kg) Fine aggregate (Kg) Coarse aggregate (Kg) Admixture (lit) M M Table 2.Mix Designations Mix Mixing Curing No. of specimens for Designation water water fc fs fb M2(PM & PC) Potable Potable M2(PM & SC) Potable Sea M2(SM & SC) Sea Sea M25(PM & PC) Potable Potable M25(PM & SC) Potable Sea M25(SM & SC) Sea Sea Table 3.Chemical Composition of Fly ash Constituents Values (% by weight) Loss on Ignition.87 Silica as Sio Iron Oxide as Fe 2 O Alumina as Al 2 O Manganese as Mn.14 Titanium Oxide as TiO 2.53 Calcium Oxide as CaO 4.58 Magnesium Oxide as MgO.6 Sodium Oxide as Na 2 O.89 Potassium Oxide as K 2 O 1.74 Phosphorus as P.32 Sulphate as SO Courtesy: Dr NTPPS, VIJAYAWADA RESULTS AND DISCUSSION Before casting the concrete specimens, the slump and compaction factors were observed for various mixes and same are reported in Table-4. The degree of workability is high for the observed slumps or compaction factors and the same is suitable for pumping and tremie placing as in the case of installation of marine piles and diaphragm walls and other structures. R S. Publication, rspublicationhouse@gmail.com Page 852

5 International Journal of Advanced Scientific and Technical Research Issue 4 volume 2, March-April 214 Table 4.Slump & compaction factor observations Mix Designation Slump(mm) Compaction Factor M2(PM & PC) M2(PM & SC) M2(SM & SC) M25(PM & PC) M25(PM & SC) M25(SM & SC) The specimens were cured for 7, 28 and 9 days period in potable water and sea water containers and tested for various strengths after elapsed period of curing. The test results of compressive strength, split tensile strength and flexural strength are tabulated in Table-5, 6 and 7 respectively. Table 5.Compressive strength test results Mix Designation Compressive Strength (N/mm²) 7 days 28 days 9 days M2(PM & PC) M2(PM & SC) M2(SM & SC) M25(PM & PC) M25(PM & SC) M25(SM & SC) Table 6.Split tensile strength test results Mix Designation Split Tensile Strength (N/mm²) 7 days 28 days 9 days M2(PM & PC) M2(PM & SC) M2(SM & SC) M25(PM & PC) M25(PM & SC) M25(SM & SC) Table 7.Flexural strength test results Mix Flexural Strength (N/mm²) Designation 7 days 28 days 9 days M2(PM & PC) M2(PM & SC) M2(SM & SC) M25(PM & PC) M25(PM & SC) M25(SM & SC) R S. Publication, rspublicationhouse@gmail.com Page 853

6 STRENGTH IN N/mm2 STRENGTH IN N/mm2 International Journal of Advanced Scientific and Technical Research Issue 4 volume 2, March-April 214 COMPRESSIVE STRENGTH The compressive strength of both the concretes i.e., M2 and M25 are higher than the target strength for 28 days and 9 days period of curing in all the exposure conditions i.e., potable water mixing and potable water curing (PM&PC), potable water mixing and sea water curing (PM&SC) and sea water mixing and sea water curing (SM&SC). However the compressive strengths reduced by about 6% and 18% compared to the 28 days of M2 Reference concrete in PM&SC and SM&SC respectively. Similarly the compressive strengths were reduced by 8% and 22% in case of 9 days period of curing. In respect of M25 concrete, about 11% and 14% reduction in strengths were noticed compared to the Reference concrete at 28 days period of curing and 5% and 2% reduction in strengths in case of 9 days. Fig 1 & 2 shows the comparison of results in respect of compressive strengths. COMPRESSIVE STRENGTH(M2) DAYS 28 DAYS 9 DAYS FA FB FC Fig. 1: Compressive strength of M2 Grade concrete and Age in number of days COMPRESSIVE STRENGTH(M25) DAYS 28DAYS 9DAYS FD FE FF Fig. 2: Compressive strength of M25 Grade concrete and Age in number of days SPLIT TENSILE STRENGTH The split tensile strength was observed to increase as the period of curing increases in both M2 and M25 grades of concrete. The reduction in split tensile strength for PW&SW concrete is marginal compared to the Reference concrete and quantitatively showing by about 1.8% and 3.5% in respect of M2 and 6.% and 3.1% for M25 concretes at 28 days and 9 days curing periods. It was also observed that the tensile strength is in increasing trend when period of curing increases. The results of split tensile strength are shown in Fig 3 & 4. R S. Publication, rspublicationhouse@gmail.com Page 854

7 STRENGTH IN N/mm2 STRENGTH IN N/mm2 STRENGTH IN N/mm2 International Journal of Advanced Scientific and Technical Research Issue 4 volume 2, March-April 214 SPLIT TENSILE STRENGTH(M2) DAYS 28 DAYS 9 DAYS FA FB FC Fig. 3: Tensile strength of M2 Grade concrete and Age in number of days 3 SPLIT TENSILE STRENGTH(M25) DAYS 28 DAYS 9 DAYS FD FE FF Fig. 4: Tensile strength of M25 Grade concrete and Age in number of days FLEXURAL STRENGTH Flexural strengths are in increasing trend as the period of curing increases in all the concretes i.e., PM&PC, PM&SC and SM&SC. A reduction in strength of about 1.45% and 1.3% was observed for PM&SC compared to PM&PC at curing periods 28 days and 9 days respectively in case of M2 concrete. Similarly, a reduction of 6.1% and 4.95% for PM&SC compared to PM&PC at 28 days and 9 days period of curing. The Flexural strength results are plotted in Fig 5 & 6. FLEXURAL STRENGTH(M2) DAYS 28 DAYS 9 DAYS FA FB FC Fig. 5: Flexural strength of M2 Grade concrete and Age in number of days R S. Publication, rspublicationhouse@gmail.com Page 855

8 STRENGTH IN N/mm2 International Journal of Advanced Scientific and Technical Research Issue 4 volume 2, March-April 214 FLEXURAL STRENGTH(M25) DAYS 28 DAYS 9 DAYS FD FE FC Fig. 6: Flexural strength of M25 Grade concrete and Age in number of days CONCLUSION From the above study, the following conclusions may be drawn: The blended concretes of M2 and M25 Grades with 25% Fly ash prepared with potable water mixing and sea water curing and sea water mixing and sea water curing exceeded their target strengths at 28 days and show increasing trend even at 9 days. The split tensile strength for M2 & M25 Grades for the specimens mixed with potable water and cured with sea water shows close values of strengths compared to the Reference concrete i.e., PM&PC. Similarly, the flexural strength for M2 & M25 Grades for the specimens mixed with potable water and cured with sea water shows close values of strengths compared to the Reference concrete i.e., PM&PC. The study may be carried out for higher grades of concrete i.e. M3 and above. The studies can be extended to use of other types of blended cements such as ground granulated blast furnace slag etc. REFERENCE [1] C. Marthong., et al (212): Effect of Fly ash additive on concrete properties, International Journal of Engineering Research and Applications (IJERA); Vol. 2, Issue 4, July August 212, pp [2] K. SuvarnaLatha., et al (212): Estimation of GGBS and HVFA strength efficiencies in concrete with age, International Journal of Engineering and Advanced Technology (IJEAT); Vol. 2, Issue 2, December 212. [3] AkinsolaOlufemi Emmanuel., et al (212): Investigation of salinity effect on compressive strength of reinforced concrete, Journal of Sustainable Development; Vol. 5, No. 6; 212. Published by Canadian Center of Science and Education. [4] E. M. Mbadike., et al (211):Effect of salt water in the production of concrete, Nigerian Journal of Technology, Vol. 3, No. 2, June 211. [5] Falah M. Wegian; (21): Effects of sea water for mixing and curing on structural concrete Studies, The IES Journal Part A: Civil & Structural Engineering, Vol.3, No.4, November 21, [6] M. I. RetnoSusilorini., et al (25):The performance of early age concrete with sea water curing, Journal of Coastal Department, Vol. 8, No. 2, February 25, R S. Publication, rspublicationhouse@gmail.com Page 856

9 International Journal of Advanced Scientific and Technical Research Issue 4 volume 2, March-April 214 [7] Md. Moinual Islam., et al (211):Suitability of sea water on curing and compressive strength of structural concrete, Journal of Civil Engineering (IEB), 4(I) (212) [8] O. O. Akinkurolere; et al (27): The influence of salt water on the Compressive strength of concrete, Journal of Engineering and Applied Science 2(2) , 27. R S. Publication, rspublicationhouse@gmail.com Page 857