Faculty Publications

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Air-cured Alkali activated binders for concrete pavements
(Chinese Society of Pavement Engineering, 2015) Palankar, N.; Ravi Shankar, A.U.; Mithun, B.M.
The present study focuses on the possibility of use of alkali activatedbinders for use in concrete pavements. Alkali Activated Slag Concrete (AASC) and Alkali Activated Slag Fly ash Concrete (AASFC) are prepared and the properties are compared with Ordinary Portland Cement Concrete (OPCC). The Ground Granulated Blast FurnaceSlag (GGBFS) and Fly Ash (FA) are blended in the ratios 100:0, 75:25, 50:50 and 25:75 as binder and activated using strong alkaline solution. Trial mixes are carried out to identify the optimal Activator Modulus (Ms) for each combination of GGBFS and FA. The mix design for the optimal activator modulus is optimised to achieve sufficient strength for Pavement Quality Concrete (PQC) and the fresh and mechanical properties are studied in detail. The results indicate the properties of AASC and AASFC are similar or slightly better than conventional OPCC and satisfy the minimum strength requirements for concrete pavements. The application of alkali activated binders will minimise the environmental hazards occurring from augmented OPC production, along with effective utilisation of industrial waste materials and conservation of natural resources. © Chinese Society of Pavement Engineering.
Experimental Investigation on FACA and FACACRETE — An Innovative Building Material
(Springer Verlag service@springer.de, 2019) Muhammed, A.; Palanisamy, P.
Recently, many studies are put forward by researchers to utilize waste materials like fly ash, GGBS, etc. in the construction industry due to the problems arise in the disposal of these materials. A novel study on incorporating the FACA (fly ash artificial coarse aggregate) in concrete is illustrated in this paper by comparing fly ash artificial coarse aggregate concrete (FACACRETE) with normal concrete. Different mixtures of geo-polymers were prepared using different molarities of NaOH solution and varying alkaline solution to fly ash ratio. These mixtures were cast to form a hard mass and cured. It is then pulverized in to fly ash artificial coarse aggregates (FACA). The properties of FACA were determined and are compared with conventional coarse aggregates. From the experiment, it is found that the FACA is a lightweight aggregate. It can be used for wearing as well as non - wearing surfaces as per IS: 383 - 2016. It is found that 8MA1 (8 Molar NaOH solution and 0.4 is the alkaline solution to fly ash ratio) is economical and can be used for further research as NaOH needed is less. This mix (8MA1) of FACA is used to prepare fly ash artificial coarse aggregate concrete (FACACRETE). The mechanical properties of both normal concrete and FACACRETE are compared and the results suggest that the compressive, splitting tensile, flexural strengths and the stress - strain relationship of FACACRETE is comparable with conventional concrete of same grade as per IS 456. The compressive toughness and compressive index of the FACACRETE is found to be more than the conventional concrete. The failure pattern of FACACRETE is associated with multiple cracking and that of normal concrete is localized failure. On considering the experimental investigations conducted here, it is found that the FACA can be used to replace conventional coarse aggregate in concrete. © 2019, Korean Society of Civil Engineers.
Bond strength characteristics of fly-ash admixed selfcompacting alkali activated concrete mixes
(Associated Cement Companies Ltd. priti.saldanha@acclimited.com, 2020) Manjunath, R.; Narasimhan, M.C.; Suryanarayana, L.R.
Bonding in any type of concrete plays a crucial role in the performance of reinforced concrete structures, which are profoundly determined by many factors such as concrete compressive strength, diameter, type and size of the bar along with length of embedment and confinement of concrete. Herein, an attempt has been made to develop fly-ash admixed self-compacting alkali activated slag concrete mixes cured under laboratory ambient conditions and to evaluate the bond strength characteristics using direct pull out test along with their bond stress-slip behaviour at the age of 28 and 56 days. These self-compacting alkali activated slag concrete mixes were developed using Fly-ash and GGBFS as the major principal binder. Naturally available river sand was used as the fine aggregate; 12.5 mm down size crushed granite chips (Jelly) constituted the coarse aggregate fractions in all these mixes. The alkaline solutions basically consisted of mixtures of sodium hydroxide flakes dissolved in the calculated quantity of water and mixed with the liquid sodium silicate solution. The experiments were planned based on Taguchi’s design of experiments methodology. A total of fifteen mixes were developed and evaluated for their flow ability characteristics as per the requirements of EFNARC guidelines along with compressive strength values at the age of 7, 14, 28 and 56 days. In an initial, calibration phase, bond strength characteristics of a set of nine mixes were utilized for performance evaluation purposes. Strength prediction equations were then derived on the basis of such results, whose predictive capacity was then evaluated and ascertained in the prediction phase with actual results of experiments on a set of three new mixes. Test results indicated higher flow ability characteristics for all the mixes satisfying the requirements as per the EFNARC guidelines. Higher compressive strengths values in the range of 46 – 85 MPa were obtained at the age of 56 days. Further acceptable bond strength values were obtained varying in the range of 8.0 – 14.5 MPa as compared to control OPC based reference concrete mix. © 2020, Associated Cement Companies Ltd.. All rights reserved.

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