Indian Concrete Journal

Development of concrete mix design using android application as per Indian standard 10262:2019 Dhruvin Gandhi, Tejas Joshi, Urmil Dave

This paper focuses on developing concrete mix design using the android application as per the Indian Standard IS: 10262 (2019). Concrete mix design is an essential parameter for constructing any reinforced concrete (RC) structures. Recently IS: 10262 (2019) has come up with significant changes in the concrete mix design. IS: 10262 (2019) has added the mix design of different types of concrete such as ordinary concrete (M30 to M60), selfcompacted concrete, high strength concrete (M65 to M100), and mass concrete. Currently, on the Google play store, such an application is not available, covering all types of concrete mix design according to IS: 10262 (2019). Concrete mix design android application has been developed for all types of concrete using all the provisions mentioned in IS: 10262 (2019). This android application covers the mix design of ordinary concrete, self-compacted concrete, high-strength concrete, and mass concrete. The android studio was used to develop a concrete mix design for the android application. This concrete mix design application also provides detailed guidelines for mixing proportions specified in IS: 10262 (2019). Experimental work was carried out to validate android application results for concrete mix design. Compressive strength result at 7 days and 28 days was measured and compared with a target mean strength for different types of concrete. A slump test was carried out to check the workability of different types of concrete. From the compressive strength result, it can be concluded that the concrete mix proportioning result obtained from the android application will be helpful for field applications. This android application has excellent benefits to the students, academicians, and practicing engineers working on concrete mix design.

Design of pier caps using existing methods: a comparative study Indu Geevar, Bijily Balakrishnan

Reinforced concrete bridge pier caps are the flared top portion of the pier provided to safely transmit the heavy loads from the deck to the substructure. These members may be considered as disturbed regions owing to their short shear span-to-depth (‘a/d’) ratios. Traditional sectional methods are sometimes used to design these members even though these are strictly not applicable due to nonlinear strain distribution. Alternatively, semi-empirical methods developed for corbels with ‘a/d’ ratio less than 1 may be used to design these members. Strut-and-tie method shall be effectively adopted for design of disturbed regions and hence may be adopted for pier caps. In the current study, pier caps with shear span-to-depth ratios 0.5, 1.0, 1.5 and 2 are designed using sectional, semi empirical and strut-and-tie methods, and are compared in terms of amount of reinforcement. The study suggests that for pier caps with ‘a/d’ ratio lesser than 1, the strut-and-method is more appropriate.

High strain rate characterization of concrete using split Hopkinson pressure bar Kavita Ganorkar, Ketan Arora, Lekhani Gaur, M. D. Goel, Tanusree Chakraborty

Dynamic characterization of concrete using 76 mm diameter compressive split Hopkinson pressure bar is carried out in the present study for M20, M25, M30, M35, and M40 grades of concrete. The behavior of concrete at strain rates varying from 241/s to 635/s is investigated. It is observed that the strength of concrete increases with the increase in strain rates. Effect of geometry is considered by incorporating two slenderness ratios of 0.3 and 0.5 for 70 mm diameter specimens. The correlation equations are proposed for computing the DIF (Dynamic Increase Factor) for the M40 grade of concrete considered herein under high strain rates.

Development of empirical equations for prediction of flexural and split tensile strengths for normal and high strength concrete with granite and calc-granulite aggregate Brijesh Singh, P. N. Ojha, Amit Trivedi, Vikas Patel, V. V. Arora

The concrete commonly used in engineering structures is a material having high compressive strength but low tensile strength. High strength concrete is being now widely used and is being incorporated in the Indian Standard Code for design (IS: 456). With addition of High strength concrete in the design code, it is important to develop the design parameters for effective use and considerations. The current Indian Standard has the equation for prediction of flexural strength but it is valid for normal strength concrete only. Flexural strength depends on the properties of the aggregates, cement paste and their interactions at the interfacial transition zone. There are numbers of equations to evaluate the flexural strength and split tensile strength by various International codes and literatures. This paper aims in developing an empirical equation to evaluate the flexural strength and split tensile strength for both Normal and High Strength Concrete (HSC) considering the indigenous aggregates and materials. The analysis considers test results with a wide range of compressive strength of concrete from 10 to 100 MP_a with a total of about 51 test results (17 samples) for flexural strength and about 27 test results (9 samples) for split tensile strength. Based on the experimental results for granite and calc-granulite aggregate an empirical equation is proposed for the prediction of flexural strength and split tensile strength and is compared with the empirical equations available in the different International standards.