EXPERIMENTAL STUDY OF SELF COMPACTING SELF CURING CONCRETE

Transcription

1 International Journal of Civil Engineering and Technology (IJCIET) Volume 8, Issue 4, April 2017, pp Article ID: IJCIET_08_04_072 Available online at ISSN Print: and ISSN Online: IAEME Publication Scopus Indexed EXPERIMENTAL STUDY OF SELF COMPACTING SELF CURING CONCRETE R. Udhayan Post Graduate Student, Department of Civil Engineering, SRM University Chennai Dr. N.P. Rajamane Head CACR, Centre for Advanced Concrete Research Centre, Department of civil engineering, SRM University, Chennai ABSTRACT With advancement in technology, concrete had been subjected to various techniques and modification. In spite of these modifications, it exhibits good mechanical properties. Curing promotes hydration of cement, controls temperature and movement of moisture from and into the concrete. To continue hydration, the relative humidity inside the concrete should be 80%. Self-curing is the process in which the water is retained in the concrete and evaporation of water is also reduced. Self-compacting concrete (SCC) is a concrete that settles by its own weight, even in the presence of congested reinforcement with full compaction. It does not need any external vibrator to compact. Self-compacting concrete is achieved by incorporation of various mineral admixtures like fly ash and silica fume and super plasticizer used at a dosage of 2% by weight of cement. In this paper self-compacting self-curing concrete is done by using polyethylene glycol at a rate of 0%, 1%, and 2%. The mechanical properties like compressive strength and tensile strength is studied. The test results were studied at different temperatures both inside and outside the lab for air curing. It is found that the optimum dosage of 1% of PEG gives higher strength. Key words: Self compacting concrete, self-curing concrete. Polyethylene glycol, Compressive strength, Split tensile strength. Cite this Article: R. Udhayan and Dr. N.P. Rajamane, Experimental Study of Self Compacting Self Curing Concrete. International Journal of Civil Engineering and Technology, 8(4), 2017, pp editor@iaeme.com

2 R. Udhayan and Dr. N.P. Rajamane 1. INTRODUCTION 1.1. Self-compacting concrete During early eighties in Japan, the concrete structures get deteriorated everywhere in the country. The reason for deterioration was found to be inadequate compaction. The quality of construction work gets worse due to the lack of skilled workers in construction industry. So to eradicate these social and technical problems, Prof. Okamura from Tokyo University in 1986 proposed a new technique called self-compacting concrete (SCC). Having high fluidity the selfcompacting concrete fills the moulding board and covers the reinforcement. Due to its high fluidity, it is not isolated. SCC works well with the low water to cement ratio. No air is get trapped inside the concrete. SCC exhibits good mechanical properties and durability. The problems like leakage vibration, over vibration and bar dense are prevented by SCC. Self-Compacting Concrete is proportioned with an optimal aggregate content, low water/cement ratio and high level dosage of super plasticizer. Self-Compacting Concrete has different properties like: Filling ability : It fills the voids in the formwork Passing ability : It passes through congested reinforcements. Segregation resistance : To remain homogeneous in composition during transport and placing Self-Curing concrete Curing is the process of adding water to the concrete externally after the concrete is being mixed, placed and finished. Proper curing of concrete allows hydration of cement and continuous gain of strength. Curing maintains the moisture movement from and into the concrete. Hydration stops when relative humidity within capillary pores drops to 80%.Self curing or internal curing is a technique by which the hydration of cement prevails with the availability of extra internal water which is not the external water. The internal water is maintained by incorporating the self-curing agent polyethylene glycol (PEG 600) which reduces the evaporation of water from the concrete, thereby increasing the water retention capacity of concrete. The advantages of internal curing are increased hydration process and strength development, reduced autogeneous shrinkage and cracking, reduced permeability and increased durability. 2. MATERIALS USED 2.1. Cement Cement is a good binder. The most common type of cement used is ordinary Portland cement. It usually originates from limestone. In this study, OPC of 53 grade is used conforming to IS Grade of cement -53 Table 1 Properties of OPC Physical properties Test results Consistency 30% Specific gravity editor@iaeme.com

3 Experimental Study of Self Compacting Self Curing Concrete 2.2. Fine aggregate Sand is a naturally occurring granular material composed of finely divided rock and mineral particles and having particle size less than 4.75 mm. River Sand conforming to IS is used in this study. Table 2 Properties of Fine aggregate Physical properties Test results Fineness modulus 3.17 Specific gravity Coarse aggregate Gravel is composed of unconsolidated rock fragments and having particle size greater than 4.75 mm. As per EFNARC Specifications, the maximum size of gravel to be used in SCC is 20 mm. Hence Gravel of 12.5mm Size is used in this study Table 3 Properties of Coarse aggregate Physical properties Test results Fineness modulus 7.3 Specific gravity Water Water plays a vital role in concrete mix. It forms paste after mixing with cement that helps in binding with the aggregate. The chemical reaction between water and cement is called Hydration. Thus hydrates or hydration products are formed during hydration by the formation of chemical bond between cement and water. Hardening of concrete is caused by water during hydration Polyethylene glycol The condensed polymer of ethylene oxide and water is polyethylene glycol. PEG 600 is used in this study where 600 is the molecular weight. It has general formula H (OCH2CH2) noh. They soluble in water. It is nontoxic, odourless, non-volatile and non-irritating. It has wide variety of uses in medicine Super plasticizer Super plasticizer reduces the water 3 to 4 times in the concrete mixes. So they are known as high range water reducing admixture. When they are added to cement particles, they emit a strong negative charge, which helps in lowering the surface tension of the surrounding water.by which the fluidity of the concrete mix is increased. They can be added to a certain limit of 2% of cement to the concrete mix so as to stop bleeding and segregation. The strength of concrete increases as water cement ratio decreases. Workability is greatly achieved by adding super plasticizer. In this study, Cera plast 300 is used as super plasticizer at a dosage of 2% by weight of cement Fly ash Fly ash (or) pulverized fly ash is a result of combustion of coal. They are obtained from the thermal power plant. It may be high calcium (15-35%) or low calcium (<10%) depending upon calcium oxide CaO present in it. The unburnt carbon content in fly ash should be less than 5%. The fly ash is of spherical size particles ranging from 0.5 to 300 micron in diameter editor@iaeme.com

4 R. Udhayan and Dr. N.P. Rajamane 2.8. Silica fume It is by product from the Ferro silicon industry. It is also known as micro silica. It is a very fine non crystalline powder silicon dioxide It is made at a temperature of C. Its size is about 0.1millimicron.It acts as an excellent pore filling material. It can be added at a proportion of 5-30% by weight of cement. It gives good cohesion, improved resistance to segregation. It is also effective in reducing bleeding. 3. MIX PROPORTION FOR SCC There is no standard mix design for self-compacting concrete (SCC).Using IS: (2009) the mix design for M30 grade is achieved. SCC is achieved by taking 55% of total aggregate as fine aggregate as per EFNARC specification. In this design water to powder ratio is taken as 0.35 and super plasticizer is added at dosage of 2% by weight of cement. The admixtures fly ash is added at 15% and silica fume at 10% by weight of cement to the mixture. Cement Fly Ash Table 4 Mix proportion for M30 grade of concrete for 1m 3 Silica Fume Fine Aggregate Coarse Aggregate Water (lit/m 3 ) Super plasticizer (%) TEST RESULTS Various test results for SCC have been done to check the workability properties. Table 5 Test results of SCC Methods Result Slump flow test 660 mm T50 5 sec L box test(h2/h1) 0.84 V funnel test 7 sec 4.1. Compressive strength and split tensile strength result Compression test and tensile strength is carried out in the cube of size 150mmx150mmx150mm and cylinder of size 200mmx300mm. The specimen with self-curing agent PEG at a dosage of 0%,1%,2% by weight of cement is added. The test results are taken for 3 days, 7 days, 28 days. The test results of the specimen are observed for both water curing (WC) and air curing (AC) at different temperature like inside and outside the lab (ie internal storage-is & external storage- ES). Compression test and tensile strength was carried out by 400 tonne HIECO compressing testing machine. Table 6 Compressive strength test results Specimen Details Compressive strength(n/mm 2 ) 3 Days 7 Days 28 Days PEG 0% Conventional (WC) PEG 0% Conventional (AC) PEG 0% SCC(WC) PEG 1% SCC(AC-IS) PEG 1% SCC(AC-ES) PEG 2% SCC(AC-IS) PEG 2% SCC(AC-ES) editor@iaeme.com

5 Experimental Study of Self Compacting Self Curing Concrete Compressive strength (N/mm 2 ) conventional(wc) conventional (ac) SCC(wc) 3 days 7 days 28 days PEG 0% PEG 0% PEG 0% PEG1% PEG1% PEG2% PEG2% Figure 1 Graphical representation for Compressive strength test results Table 7 Split tensile strength test results Specimen Details Split tensile strength(n/mm 2 ) 3 Days 7 Days 28 Days PEG 0% Conventional (WC) PEG 0% Conventional (AC) PEG 0% SCC(WC) PEG 1% SCC(AC-IS) PEG 1% SCC(AC-ES) PEG 2% SCC(AC-IS) PEG 2% SCC(AC-ES) split tensile strength (N/mm 2 ) conventional(wc) conventional (ac) SCC(wc) 3 days 7 days 28 days PEG 0% PEG 0% PEG 0% PEG1% PEG1% PEG2% PEG2% Figure 2 Graphical representation for Split tensile strength test results editor@iaeme.com

6 R. Udhayan and Dr. N.P. Rajamane 4.3. Weight loss test The specimen of different size was cast and their weight loss is taken for first 3 consecutive days and for 14 th and 28 th days. The optimum of PEG 1% is studied. The loss of weight is less in specimen with PEG than the normal concrete. From observation, the PEG prevents the water from evaporation and helps in internal curing. The presence of moisture eliminates the additional supply of water. This promotes the strength PEG 0% 1% Table 8 Weight loss test WEIGHT OF DIFFERENT SPECIMEN(Kg) Days 100x100x x150x x75 200x100 (mm) (mm) (mm) (mm) CONCLUSION The following conclusion was drawn from this study It was observed that 2% PEG gives lower compressive strength and spilt tensile strength compared to 1% PEG. Thus it is found that addition of PEG in high dose over 1% of cement would not give expected results in strength and those cannot be used practically. 1% PEG gives higher compressive strength and spilt tensile strength compared to the normally used water cured specimens without self-curing chemicals. It is observed that the specimen with PEG when placed outside the lab gives same result as that of normal water cured specimen. The usage of PEG gives better strength than the water cured conventional concrete when stored inside the lab. So self-curing agent (PEG) works well in a controlled environment. Self-Curing Chemical Admixture (SCCA) ie. PEG can promote effective hydration of cement without any externally applied curing procedure REFERENCE [1] Ambily P S and Rajamane N P (2007), Self curing concrete an introduction Part 1, Masterbuilder, Vol. 9, pp [2] Ambily P S and Rajamane N P (2007), Self curing concrete an introduction Part 2, Masterbuilder, Vol. 9, pp [3] Ambily P S and Rajamane N P (2007), Self curing concrete an introduction, New Building Materials and Construction World, Vol. 13, pp [4] Bentz, D.P., and Stutzman, P.E., Curing, Hydration, and Microstructure of Cement Paste, ACI Materials Journal, 103 (5), , editor@iaeme.com

7 Experimental Study of Self Compacting Self Curing Concrete [5] Magda I. Mousa, Mohamed G. Mahdy, Ahmed H. AbdelReheem, Akram Z. Yehia, Physical properties of selfcuring concrete (SCUC), HBRC Journal. [6] Neville A. M. (2004), Properties of Concrete, 5th Edn, Addison Wesley Longman, England, pp [7] SRM thesis of Experimental study of self curing concrete by Sathish kumar A.P,2014 [8] Shuhua LIU, Key Techniques of Self Compacting Concrete, Advanced Materials Research Vols (2011) pp [9] Rahul Dubey The effect of dosages of super plasticizer on compressive strength of self compacting concrete, Construction and the Building Materials 40 (2010)