IJIRST –International Journal for Innovative Research in Science & Technology| Volume 3 | Issue 02 | July 2016 ISSN (online): 2349-6010
Study the Influence of Magnesium Sulphate Attack on SIFCON by Partial Replacement of Cement with Fly Ash Patil Deepesh P PG Student Department of Civil Engineering Trinity College of Engineering & Research, Pisoli, Pune 065, (M.S.), India
Jayant Kanase S Assistant Professor Department of Civil Engineering Trinity College of Engineering & Research, Pisoli, Pune 065, (M.S.), India
Abstract In this experimental investigation study of the influence of magnesium sulphate attack on Slurry Infiltrated Fibrous Concrete (SIFCON) using hooked ended steel fibres is carried out. Similarly the replacement of cement with fly ash in three different proportions as 5%, 10%, 15%, and replacement of fine aggregate with quarry dust in three different proportions of 5%, 15% and 25% was done. The main goal is to improve the compressive strength of concrete. To optimize this serious defect partial incorporation of fibers is practiced. In this study we have induced 5% and 6% fibers of the total volume of the specimen. For the study, the cubes were kept immersed in MgSO4 for 28 days and the attack of Sulphate on concrete was studied. Mechanical test such as compression test was carried out on standard size of cubes28 days. In this investigation it was observed that the compressive strength was decreased of SIFCON and there was no change in dimensions, any gain or loss of weight to the SIFCON specimens which were under sulphate attack after 28 days of acid curing. Keywords: SIFCON, Steel hooked end fibres, Fly Ash, Quarry Dust _______________________________________________________________________________________________________ I.
INTRODUCTION
SIFCON (Slurry Infiltrated Fibrous Reinforced) Concrete is new construction material which has high strength as well as large ductility and excellent potential for structural applications when accidental (or) abnormal loads are encountered during services SIFCON also exhibit new behavioral phenomenon, that of ”Fiber lock” which believed to be responsible for its outstanding stress-strain properties. The matrix in SIFCON has no coarse aggregates, but a high cementitious content. However, it may contain fine (or) coarse sand and additives such as fly ash, micro silica and latex emulsions. The matrix fineness should be designed so as to properly infiltrate the fiber network placed in moulds, or else large pores may form and it will lead to substantial reduction in properties. All steel fiber types namely straight, hooked and crimped can be used. The fibers are subjected to frictional and mechanical interlock in addition to the bond with the matrix. The matrix plays the role of transferring the forces between fibers by shear, but also acts as bearing to keep fibers interlock. Slurry-infiltrated fibrous concrete or mortar (SIFCON) can be considered as a special type of fiber-reinforced concrete (FRC). In two aspects, however namely, fiber content and the method of production of SIFCON is different from normal FRC. The fiber content of FRC generally varies from 1 to 2 percent by volume, but the fiber content of SIFCON varies between 4 to 20 percent. Again, the matrix of SIFCON consists of cement paste or flowing cement mortar as opposed to regular concrete used in FRC. These make the production of SIFCON far different from FRC. Unlike FRC, for which the fibers are added to the wet or dry concrete mix, SIFCON is prepared by infiltrating cement slurry into a bed of fibers preplaced and packed tightly in the molds. In spite of their relatively high cost, high performance fiber reinforced cement-based composites are used more widely all over the world especially in seismic retrofit design and in the structures under explosive and impact effects. The inclusion of adequate fibers improves tensile strength and provides ductility. II. PREPARATION OF SIFCON Analogous to preplaced aggregates concrete, Sifcon is preplaced fibre concrete with the placement of the fibres in a mould, or on a 6 substrate, as the initial construction step. Fibre placement is accomplished by hand, or through the use of commercial fibre dispersing units. The amount of fibres to be incorporated depends on aspect ratio (1/d), fibre geometry, and placement technique. External vibrations can be applied during the fibre placement operation. In most cases, high-range water reducing admixtures are used in order to improve the flow ability of the slurry to ensure complete infiltration without increasing the water- cement ratio (W/C). The dosage of super plasticizers has a great effect on fluidity, cohesiveness and penetrability of cement slurries.
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Study the Influence of Magnesium Sulphate Attack on SIFCON by Partial Replacement of Cement with Fly Ash (IJIRST/ Volume 3 / Issue 02/ 053)
Material Used: Ordinary Portland cement, 53 Grade conforming to IS 12269-1987 was used to prepare SIFCON. Other materials used were Steel Fibers, River sand, Quarry Dust and Fly Ash. The steel fibres were with aspect ratio of 60. Locally available quarry dust and river sand passing through 1.18mm sieve were taken. Concrete Mix Preparation: The slurry was prepared by using cement to sand ratio of 1:1 and the water content being 0.4 which was determinedon the basis of flow ability of the slurry. Steel fibers were preplaced in the mold with different proportions of 5% and 6%. Each proportion of steel fiber consisted of cement being partially replaced with Fly Ash in different proportions of 5%, 10% and 15%, and fine aggregate being partially replaced with Quarry Dust in different proportion of 5%, 15% and 25%. III. EXPERIMENTAL PROGRAM The most aggressive environmental agent that affects the long term durability of field concrete structure are the chlorides(marine environment deicing salt) and the sulphates(soil, ground water, sea water). Sulphates are found in the form of sodium sulphate (Na2SO4), potassium sulphate (K2SO4), magnesium sulphate (MgSO4) and calcium sulphate (CaSO4), and these salts are highly soluble. When sulphates are present above a certain thresh hold level (>1000ppm), they are known to be detrimental to the concrete. Well-known researchers ion the area of durability of concrete reported that the US Bureau of reclenation warned that the concentration of soluble sulphates>0.1% in the soil(150 mg/lit SO4 in water) endanger concrete and more than 0.5% soluble sulphate in soil(over 2000mg/lit SO4 in water) may have a serious effect. Furthermore, the ACI 318 requirements for concrete exposed to sulphate attack classified the severity of sulphate environment as follows: Table – 1 ACI 318 Requirements for Concrete Exposure concentration of soluble sulphates expressed as SO4 In soil (%) In water (ppm) <150 Mild<0.1 Moderate 0.10 to 0.20 150 to 1500 Severe 0.20 to 2.0 1500 to 10000
A magnesium sulphate hydrate dissolved in water with a content of 5 % by weight of total water required for curing of the specimens was used in the study as a salt. All the specimens that were subjected to sulphate attack were initially cured in water for 28 days after remoulding. They were then again immersed in the magnesium sulphate solution for 28 days. The sulphate solution was replaced every 7 days. The concrete specimens were attacked by the liquids with pH value less than 6.5. Hence the pH value was maintained at a value of 5.5 or below it. At pH value less than 4.5 the attack is very severe. The length and mass changes were monitored on three concrete cube specimens of 150 × 150 × 150 mm. For length change measurements, four readings were taken from each specimen at the end of each immersion cycle. The average length was then recorded and the results were expressed as a percentage with respect to the length changes. If the sulphates or the salt solution are able to reach the reinforcing steel through the minor cracks or the porosity of the concrete, corrosion can occur which will cause severe cracking.
Fig. 1: Magnesium Sulphates
IV. RESULTS The compressive strength without subjecting to sulphate attack and compressive strength subjecting to sulphate attack for 28 days of curing by partial replacement of cement with Fly ash (5%,10% and 15%) and steel fibres varying 5% and 6% are listed in Table–2.
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Study the Influence of Magnesium Sulphate Attack on SIFCON by Partial Replacement of Cement with Fly Ash (IJIRST/ Volume 3 / Issue 02/ 053)
Table – 2 Comparison of SIFCON Specimen Before and After Sulphate Attack Under Compression Test Description Compressive Strength without subjecting to sulphate Compressive Strength subjecting to sulphate (Age of Curing of specimen is 28 attack attack days) (N/mm2) (N/mm2) F.A.(5%) 5% 54.22 52.82 F.A.(10%)5% 56.79 53.14 F.A.(15%) 5% 53.37 49.93 F.A.(5%) 6% 57.94 54.61 F.A.(10%) 6% 59.38 55.75 F.A.(15%) 6% 55.62 51.06
Fig. 2: Comparison of SIFCON Specimen Before and After Sulphate Attack under Compression test for Fly Ash
The compressive strength without subjecting to sulphate attack and compressive strength subjecting to sulphate attack for 28 days of curing by partial replacement of Fine Aggregate with Quarry Dust (5%,15% and 25%) and steel fibres varying 5% and 6% are listed in Table–3 Table – 3 Comparison of SIFCON Specimen before and After Sulphate Attack under Compression Test Description Compressive Strength without subjecting to sulphate Compressive Strength subjecting to sulphate (Age of Curing of specimen is 28 attack attack days) (N/mm2) (N/mm2) Q.D.(5%) 5% 50.22 47.68 Q.D.(15%) 5% 47.65 45.93 Q.D.(25%) 5% 45.36 43.05 Q.D.(5%) 6% 54.23 52.29 Q.D.(15%) 6% 52.06 50.74 Q.D.(25%) 6% 51.68 49.52
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Study the Influence of Magnesium Sulphate Attack on SIFCON by Partial Replacement of Cement with Fly Ash (IJIRST/ Volume 3 / Issue 02/ 053)
Fig. 3: Comparison of SIFCON Specimen Before and After Sulphate Attack under Compression test for Quarry Dust
V. CONCLUSION In Compression test, SIFCON specimens of Fly ash (5%, 10%, and 15%) with 2 %, 3 %, 5% and 6% steel fiber. The specimen of 6% steel fibres and Fly ash of 10% with replacement of cement showed higher compressive strength in Comparison with 2 %, 3 % and 5% steel fibres of SIFCON specimen at the age of 28 days curing. Similarly, when fine aggregate was replaced with Quarry dust (5% 15% 25%) with 5% and 6% fibers, compressive strength was decreased at the age of 28 days curing. SIFCON specimen which was kept under sulphate attack curing of MgSO4for 28 days and was tested under compressive testing machine and it was observed that maximum 6% of compressive strength was decreased when cement was replaced by fly ash, It was also observed that Compressive strength was decreased to almost 5% when fine aggregates were replaced by quarry dust. It was also observed that there was no change in dimensions, no gain or loss of weight to the SIFCON specimens which were under sulphate attack after 28 days of acid curing. ACKNOWLEDGMENT The writers are thankful to Prof. V.S. Shingade sir (HOD Civil Dept. KJTCOE&R, Pune) for his guidance and support till end. REFERENCES [1] [2] [3] [4] [5] [6] [7] [8] [9]
S.Balaji and G.S. Thirugnanam, “Flexural Strengthening of reinforced concrete beams using precast SIFCON laminates” Journal of structural Engineering, Vol.40, Issue No. 3, pp.262-267, 2013. Lankard, D.R., “Preparation, Applications: Slurry Infiltrated Fiber Concrete (SIFCON)”, Concrete International, Vol.6, Issue No.12, pp. 44-47, 1984. Naaman, A.E., Otter, D., and Najm, H., “Elastic Modulus of SIFCON in Tension and Compression”, ACI Materials Journal, Vol. 88, Issue No.6, pp. 603612, 1991. Naaman, A.E., and Baccouche, M.R., “Shear Response of Dowel Reinforced SIFCON”, ACI Structural Journal, Vol. 92, Issue No.5, pp. 587-569, 1995. Naaman, A.E., Reinhardt, H.W., and Fritz, C., “Reinforced Concrete Beams with a SIFCON Matrix”, ACI Structural Journal, Vol. 89, Issue No.1, pp. 7988, 1992. Naaman, A.E., and Homrich, J.R., “Tensile Stress-Strain Properties of SIFCON”, ACI Materials Journal, Vol. 86, Issue No.3, pp. 244-251, 1989. Hamza, A.M., and Naaman, A.E., “Bond Characteristics of Deformed Reinforcing Steel Bars Embedded in SIFCON”, ACI Materials Journal, Vol. 93, Issue No.6, pp. 578-588, 1996. Lankard, D.R., “Factors Affecting the Selection and Performance of Steel Fiber Reinforced Monolithic Refractories”, American Ceramic Society Bulletin, Vol. 63, Issue No.7, pp. 919-925, 1984. Zhang, J., and Li, V.C., “Influences of Fibers on Drying Shrinkage of Fiber-reinfoced Cementituous Composites”, ASCE Journal of Engineering Mechanics, Vol.127, Issue No. 1, pp. 37-44, 2001.
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