EFFECT OF MINERAL ADMIXTURES ON PROPERTIES OF CONCRETE WITH TERNARY CEMENT BLENDS

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EFFECT OF MINERAL ADMIXTURES ON PROPERTIES OF CONCRETE WITH TERNARY CEMENT BLENDS Synopsis of PhD Thesis Submitted by KANCHAN MALA (Enrollment No.: 08P05103G) Under the Guidance of Prof. K.K. Jain, JUET, Guna, India Dr.

1 EFFECT OF MINERAL ADMIXTURES ON PROPERTIES OF CONCRETE WITH TERNARY CEMENT BLENDS Synopsis of PhD Thesis Submitted by KANCHAN MALA (Enrollment No.: 08P05103G) Under the Guidance of Prof. K.K. Jain, JUET, Guna, India Dr. A. K. Mullick, Former DG, NCB, India and Prof. P. K. Singh, JUET, Guna, India DEPARTMENT OF CIVIL ENGINEERING JAYPEE UNIVERSITY OF ENGINEERING AND TECHNOLOGY A.B.ROAD, RAGHOGARH, GUNA (MADHYA PRADESH) INDIA January, 2014

2 PREFACE The large scale production of cement is posing environmental problems on one hand and the unrestricted depletion of natural resources on the other hand. This threat to the ecology has led to lots of investigations to utilize industrial by-products as mineral admixtures or supplementary cementitious material in making concrete. It is now well recognized that incorporation of mineral admixtures in blended concrete as a partial replacement of ordinary Portland cement (OPC) in mortar or concrete is an effective means for improving the properties in fresh and hardened state. Any mineral admixture can be used alone with OPC in binary blend cement system and combined with another different mineral admixture in ternary blend cement system. In ternary blend cement system, two mineral admixtures act as complements to each other and improve the strength and durability of resultant concrete many folds. The ternary blend cement is more economical than OPC. From literature review, it was found that lots of researches have been carried out to study mechanical properties and durability of ternary blend concrete of OPC, silica fume (SF) and fly ash (FA). Most of the works are confined to specific percentage replacement level at some specific w/b ratio. Isaia et al.(2012) studied the statistical influence of type and content of mineral admixtures, water/binder ratio and compressive strength of binary and ternary concrete mixtures on microstructure and durability by using data of strength and durability tests of five different projects. Among the dependent variables, the mineral admixture content presented the highest significance followed by water/binder ratio, mineral admixture type and lastly the compressive strength. This highlights the importance of type and content of used mineral admixture in concrete. OBJECTIVES The main objectives of the research work are followings: 1. To know the effect of different replacement levels of SF and FA in their ternary blend cement system on the followings : Mechanical properties of concrete - compressive strength and split tensile strength. Accelerated curing strength of concrete SYNOPSIS 1

3 Durability properties of concrete - sorpitivity, water absorption and chloride penetration depth Resistance of cracked concrete to chloride induced corrosion assessed by half cell potential method. 2. To optimize the quantity of fly ash to replace the quantity of OPC and study the variation in the different properties of concrete containing increasing percentage of fly ash from 0% to 50 %. 3. To study the synergic effect of ternary blend cement system and develop new method to estimate synergic effect. 4. To boost up the confidence of user to use ternary blend cement system by providing more information and additional data. SUMMARY OF THE THESIS The thesis consists of nine chapters. A chapter wise summary of the thesis is given below: Chapter 1: Introduction Production of every one tonne of OPC emits about one tonne of carbon dioxide (CO 2 ) into the atmosphere, causing global warming. Statistics reveal that the Cement industry constitutes about 5 % of the total emission of green house gases (GHG) in India [Ghosh and Roychowdhury (2009)]. Every one tonne of OPC requires 1.2 to 1.5 tonnes of lime stone as raw material and approximately 0.2 tonnes of coal as fuel for burning, causing depletion of natural resources. The energy requirements for manufacturing one kg cement are 750 Kcal (thermal) and 85 Kcal (electrical), which is exacting the energy sources [Mullick (2012)]. Therefore, an effective way to reduce the adverse environmental impacts of concrete without affecting its engineering properties is to reduce the amount of OPC in concrete. Use of mineral admixture with OPC in ternary blend cement system as a binder is an effective and practical way to achieve this objective. SYNOPSIS 2

4 The effect of different replacement levels of mineral admixtures in ternary blend cement system to get optimum benefits of using mineral admixtures has not been investigated vastly, especially with respect to the corrosion resistance of cracked concrete. The cracks present in concrete are the easiest path for entering deteriorating agencies like moisture, chloride ions, oxygen, etc into the concrete. Cracks are responsible for early initiation of corrosion and failure of structures. In the present scenario of fast constructions, the accelerated curing strength is used as a tool for quality control of concrete. If poor concrete is suspected to be poured, remedial measures can be taken at early stage. However, the literature review shows that only a few works have been done to investigate the effect of mineral admixtures on accelerated curing strength. Hence, there is a need to explore this aspect also thoroughly. The aim of this study is to investigate the effect of different replacement levels of OPC by FA / SF in binary blend cement system and by SF + FA in ternary blend cement system (TBCS) on the mechanical properties, accelerated curing strength, durability and corrosion resistance in the presence of artificially induced crack. A new method has been proposed for evaluating the synergic effect of mineral admixtures individually in ternary cement blend system. For achieving the objectives, the research work has been carried out into following two phases: Phase I The study of mechanical properties and accelerated curing strength of concrete on cubical and cylindrical specimens. Phase II The study of durability properties and corrosion resistance of concrete The w/b ratios of 0.3, 0.4 and 0.45 have been selected for the study in phase I. Two w/b ratios of 0.3 and 0.4 have been used for the study in phase II. SYNOPSIS 3

5 Chapter 2: Literature Review Past researches in the field of concrete using ternary blend cement system have been reviewed and the findings of some important papers are presented here in brief. A.K. Mullick (2007) a discussed the main features of an ideal cement composition and the role of mineral admixtures in ideal cement systems. The one way to obtain the ideal cement system can be the use of fly ash, granulated slag or silica fume in requisite amounts as part replacement of OPC i.e. the use of binary and ternary cement blends. Concrete incorporating the industrial wastes like fly ash, slag and silica fume are more durable in aggressive environment. Enhanced durability of concrete results from denser micro-structure, strengthened aggregate-matrix interface, reduction in micro cracking and increased water-tightness [ Mullick (2007) b ]. In ternary blend cement system, due to synergic effects, enhancement of some properties of concrete is more than superposition of the individual contribution for the respective proportions [Isaia et al. (2003)]. The synergic effect is due to physical and chemical effect of mineral admixtures. Isaia et al. (2003) investigated ternary systems incorporating fly ash and silica fume and found that the physical effect was presumably due to a higher content of particles smaller than 5 µm, whereas the chemical effect was associated with higher pozzolanic activity of the ternary system. Both effects were well reflected by increased compressive strength. A number of researches demonstrated that the combined usage of SF and FA in ternary blend cement system resulted in overall improvements in mechanical properties. The combination of silica fume and FA results improvement in ternary blend concrete with early strength and long-term strength development [Thomas et al. (1999)]. Jones et al. (1997) examined the chloride and carbonation durability performance of concrete containing ternary blended binders in comparison to OPC and binary blend of OPC+FA concrete. It has been shown that the chloride resistance of all the ternary binder concrete is significantly higher than corresponding OPC and binary mixes. Other researchers [Elahi et al. (2010), Thomas et al. (1999), Shehata and Thomas (2002), Khan (2012), Hariharan et al. (2011)] also reported that ternary blend of OPC+FA+SF has very high resistance to the ingress of chloride ions. SYNOPSIS 4

6 Soleymani and Ismail (2004) investigated the corrosion activity of steel embedded in two types of concrete, ordinary and high performance using different corrosion measurement methods like Tafel plot, linear polarization resistance, half-cell potential and chloride content methods. High performance concrete using silica fume showed lower corrosion activity level compared with OPC specimens. Saraswathy and Song (2007) evaluated the corrosion resistance of Portland pozzolana cement (PPC) and fly ash blended cements in pre-cracked reinforced concrete slabs using various electrochemical tests like open circuit potential, linear polarization technique, free chloride measurement, alkalinity and weight loss measurements and concluded that PPC and fly ash replaced concrete showed better corrosion resistance than OPC. Isaia et al. (2012) studied the statistical influence of type and content of mineral admixtures, water/binder ratio and compressive strength of binary and ternary concrete mixtures on microstuctural characteristics and durability. Among the dependent variables, the mineral admixture content presented the highest significance followed by water/binder ratio, mineral admixture type and lastly the compressive strength. So, the effect of different replacement levels of mineral admixtures on different aspects of ternary blend cement system need to be thoroughly investigated to get optimum benefits of using mineral admixtures, as ternary blend concrete are the concrete of the present and future [Kumar and Kaushik (2003)]. Chapter 3: Experimental Planning and Testing In the study of phase I, three w/b ratios - 0.3, 0.4 and 0.45 were used to cover the strength variation from high strength to medium strength. The OPC was replaced with FA by 20, 30, 40 and 50% and with SF by 7 and 10% in binary blend cement system, whereas in ternary blend cement system total replacement of OPC with SF+FA was kept 20, 30, 40 and 50%, either using 7 % or 10% SF. Compressive strength, split tensile strength and accelerated curing strength by using warm water method as per IS: 9013 (1978) were studied for different mixes. In the study of phase II, two w/b ratios 0.3 and 0.4 were selected. Water permeability characteristic of concrete was studied by using water absorption test and sorpitivity test. Ingress of chloride ions in concrete was assessed by chloride penetration depth measurement. SYNOPSIS 5

7 Corrosion resistance of artificially induced cracked concrete (with crack width of 0.1 mm or 0.2 mm) and uncracked concrete was evaluated by half-cell potential (HCP) method using saturated Calomel electrode. In HCP test, specimens were subjected to alternate wetting and drying cycles and measurements were taken at exposure period of 0, 3, 6, 9 and 12 months. Chapter 4: Properties of Concrete in Fresh and Hardened State For a given slump value, the superplasicizer (SP) dose decreases with increase in the percentage replacement level of FA in binary blend cement system of OPC+FA, whereas SP dose increases in binary blend cement system of OPC+SF under similar condition. The SP dose for control mix was lower than OPC+SF mixes and higher than OPC+FA mixes. In ternary blend mixes of OPC+FA+SF, the SP doses were higher than their binary mixes of OPC+FA at respective levels. It is lower than control mix beyond 20% replacement level. The reduction in SP dosage in ternary blend cement system is due to the effect of spherical particles of FA to increase the fluidity; hence, reducing the SP doses for a given slump value. When OPC is replaced with fly ash, the compressive strength of concrete decreases with respect to control mix for all w/b ratios, whereas when OPC is replaced with SF, the strength increases with respect to control mix. As the w/b ratio increases the percentage reduction in strength is more for same replacement level. The results of compressive strength of concrete using ternary cement blends indicate that the compressive strength with respect to control mix is higher up to certain percentage replacement level (optimal replacement level) of OPC with SF+FA for all w/b ratios and then becomes lower with further increase in percentage replacement level. Keeping the cement content of control mixes at each w/b ratio as constant, with decrease in w/b ratio, higher percentage of OPC can be replaced with SF+FA to get strength comparable to respective control mix. Results also indicated that for desired strength to develop at early age, the OPC replacement level in concrete using ternary blend system is limited to 20% with combination of 10% SF and 10% FA. If early strength is not the barrier, it is possible to achieve the same 28-days strength of concrete by adopting a mix with lower w/b ratio and higher replacement level of OPC with SF+FA, instead of adopting a mix with higher w/b ratio and lower replacement level. The split tensile strength also shows similar trend as compressive strength. However, for a given compressive strength level, the split tensile strength of concrete using binary and SYNOPSIS 6

8 ternary blend cement system was higher than control mix due to strengthening of interfacial transition zone due to filler effect and pozzolanic reaction. The relationship between split tensile strength and compressive strength at the age of 7 and 28 days has been proposed by regression analysis using empirical relationship given below: f t = m (f c ) n (4.1) where f t and f c are split tensile strength and compressive strength in MPa respectively, measured on cylinders having diameter of 150 mm and height of 300 mm at 28 days, m and n are constants of regression analysis. The value of n lies in the range of 0.5 to Chapter 5: Accelerated Curing Strength The accelerated curing strength is correlated to normal curing strength by linear relationship as given below: f c, norm = A*f c,acc + B (5.1) where f c, norm and f c, acc are compressive strengths of normal cured concrete (ACS) and accelerated curing strength (NCS) respectively, A and B are constants of regression analysis [Neville (2009)]. Regression analysis was performed on the data of ACS and NCS obtained at three w/b ratios for each type of mix at particular replacement level. The binary mixes of OPC+FA show that the percentage replacement of fly ash does not affect the relationship between ACS and NCS at 7 and 28 days. In other words, a single relationship will be applicable for concrete using OPC+FA up to 50% replacement level. Similar result was obtained for binary mix of OPC+SF. Ternary blended cement concrete behaved differently at early age when the replacement levels were 40% or more. So, two regression equations are required to predict the NCS at 7-day age depending upon percentage replacement level. On the other hand, the 28-day regression equations are almost similar up to 50% replacement levels. Hence a single SYNOPSIS 7

9 regression equation can be used for all replacement levels up to 50% to predict the NCS from ACS at 28-day age. However, a single regression equation at each age can predict fairly the normal cured strength from the accelerated curing strength for all types of mixes, when the strength of all types of binary and ternary mixes were considered together to get a best fit line. It shows that type of binders and replacement levels do not affect significantly the relationships between accelerated curing strength and 7-day and 28-day normal cured strength of concrete. However, it is recommended to develop regression equation for each type of concrete mix for better accuracy in strength prediction. Chapter 6: Durability and Corrosion Résistance Many aspects of durability can be improved by reducing the permeability of concrete. A permeable concrete allows ingress of the moisture, oxygen, chloride ions and other aggressive agents into the concrete. Therefore, it is desirable to make the concrete impermeable to improve the resistance of concrete to weathering agents. The results indicate that as percentage replacement level increases the value of percentage water absorption, sorpitivity coefficient and chloride penetration depth measurement decreases up to certain replacement level and then increases. However, they were lower than their respective control mixes in the most cases. In HCP test, change in moisture content affects the HCP reading and shifts it towards more negative values in wetted areas. Therefore, all measurements were taken at the end of wet cycles in saturated condition to eliminate the variation in readings due to change in moisture content. A correction factor of 95 mv was found to correlate the HCP readings in wet and dry condition. HCP tests also showed similar trend that as percentage replacement level increases, HCP values decreases up to certain replacement level and then increases. As crack width increases, the HCP readings tend to be more negative, indicating higher probability of corrosion activity. The variation in HCP value with crack width was not very high. SYNOPSIS 8

10 Chapter 7: Synergic Effect of Mineral Admixtures If the efficiency factor k is known for a mineral admixture (MA), the strength of a mix containing MA can be determined by modifying the Bolomey s equation given below [Bharatkumar et al. (2001)] : f c = A 1 (C/W) + A 2 for no MA mix (7.1) f c = A 1 (C+kP)/W + A 2 for MA mix (7.2) where f c is compressive strength of concrete in MPa, C is the cement content in kg/m 3,W is the water content in kg/m 3 and A 1, A 2 are constants influenced by ingredients, curing conditions and age of concrete [Bharatkumar et al. (2001)]. Equation 7.2 can be used to find efficiency factor of a single type of MA or combined efficiency of different types of MA. This equation has been further modified to find the synergic effect factor and efficiency factor of SF and FA individually in ternary blend cement system. The proposed method assessed reasonably well the synergic effect and efficiency factor of FA and SF individually in concrete using ternary blend cement system. This method can also be used to predict the compressive strength of concrete using TBCS for a given mix proportion. Chapter8: Statistical Analysis Statistical analysis of experimental data has been carried out using 2k factorial method and response surface method using software Minitab 16. The mechanical and durability properties can be predicted by quadratic fit response surface model. The strength of concrete is affected most by w/b ratio followed by age of concrete, percentage FA and then percentage SF. The interaction of percentage FA and SF, percentage SF and w/b ratio, w/b ratio and age of concrete significantly affect the strength. HCP value is affected most by exposure period followed by crack width, w/b ratio, percentage of SF and then percentage of FA. The interaction of percentage of FA and SF, percentage SF and exposure period, w/b ratio and exposure period, crack width and exposure period significantly affect the HCP value. SYNOPSIS 9

11 Chapter 9: Conclusions The overall conclusion drawn from this study is that ternary blend cement system of OPC+FA+SF comprise a better choice than OPC concrete due to economic reasons, better resistance to chloride ions induced corrosion even in cracked condition and being environmental friendly. If early strength is not the barrier, it is possible to achieve the same 28-days strength of concrete by adopting a mix with lower w/b ratio and higher replacement level of OPC with SF+FA, instead of adopting a mix with higher w/b ratio and lower replacement level. The resultant concrete also have better corrosion resistance due to ingress of chloride ions and lower permeability than OPC concrete even at replacement level of 50%. REFERENCES 1. Bharatkumar, B. H., Narayanan, R., Raghuprasad, B. K. and Ramchandramurthy, D. S., (2001), Mix proportioning of high performance concrete. Cement and Concrete Composites, Vol. 23, No.1, pp Elahi, A., Basheer, P.A.M., Nanukuttan, S.V. and Khan, Q.U.Z.,(2010), Mechanical and durability properties of high performance concretes containing supplementary cementitious materials, Construction and Building Materials, Vol.24, pp Ghosh, S. P. and Roychowdhury, K. K., (2009), The sustainability chain: climate change global warming clean development mechanism (CDM) energy efficiency carbon trading Indian cement industry, NCB CMA special publication, 11 th NCB international seminar on cement and building materials, New Delhi, India, November 17-20, pp Hariharan, A. R., Santhi, A. S.and Mohan, Ganesh.,(2011), Effect of ternary cementitious system on compressive strength and resistance to Chloride ion penetration, International Journal of Civil and Structural Engineering, Vol.1, No. 4, pp SYNOPSIS 10

12 5. Isaia, G.C., Furquim, P. and Gastaldini,A.L.G., (2012), A statistical approach of binary and ternary concrete mixtures with mineral additions, Construction and Building Materials, Vol. 36, pp Isaia, G.C., Gastaldini, A.L.G. and Moraes R., (2003), Physical and pozzolanic action of mineral additions on the mechanical strength of high-performance concrete, Cement and Concrete Composites, Vol. 25, pp IS: , Indian standard method of making, curing and determining compressive strength of accelerated-cured concrete test specimens, Re-affirmed 1999, Bureau of Indian Standards, New Delhi. 8. Jones, M.R., Dhir, R.K. and Magee, B.J., (1997), Concrete containing ternary blended binders: resistance to chloride ingress and carbonation, Cement and Concrete Research, Vol.27, No.6, pp Khan,M. I., (2012), Comparison of Chloride Ion Penetration and Diffusion of High- Performance Concrete, KSCE Journal of Civil Engineering, Vol.16, No.5, pp Kumar, Praveen and Kaushik, S. K.,(2003), Some trends in the use of concrete : Indian scenario. Indian Concrete Journal, Vol.77, No.12, pp Mullick, A.K., (2007) a, Performance of Concrete with binary and ternary cement blends, ICJ, Indian Concrete Journal, Vol. 81, No. 1, pp Mullick, A.K., (2007) b, Use of industrial wastes for sustainable cement and concrete construction, Indian Concrete Journal, Vol. 81, No.12,pp Mullick, A.K., (2012), Green options for binder system and aggregates in sustainable concrete, Indian Concrete Journal, Vol. 85,Vol. 6, pp Neville, A.M., (2009), Properties of concrete, Pearson Education, Inc. and Dorling Kindersley Publishing, Inc, New Delhi, India. SYNOPSIS 11

13 15. Saraswathy, V. and Song, Ha-Won, (2007), Evaluation of corrosion resistance of Portland pozzolana cement and fly ash blended cements in pre-cracked reinforced concrete slabs under accelerated testing conditions, Material Chemistry and Physics, Vol. 104, pp Shehata, M. H. and Thomas, M. D.A., (2002), Use of ternary blends containing silica fume and f ly ash to suppress expansion due to alkali silica reaction in concrete, Cement and Concrete Research, Vol.32, pp Soleymani, H. R. and Ismail, M. E., (2004), Comparing corrosion measurement methods to assess the corrosion activity of laboratory OPC and HPC concrete specimens, Cement and Concrete Research, Vol. 34, No.11, pp Thomas, M.D.A., Shehata, M.H., Shashiprakash, S.G., Hopkins, D.S., and Cail, K., (1999), Use of ternary cementitious systems containing silica fume and fly ash in concrete, Cement and Concrete Research, Vol. 29, pp SYNOPSIS 12

Effect of silica fume on the resistance to chloride ion penetration in high performance concrete

American Journal of Engineering Research (AJER) e-issn : 2320-0847 p-issn : 2320-0936 Volume-2 pp-01-05 www.ajer.org Research Paper Open Access Effect of silica fume on the resistance to chloride ion penetration