Difference between IS 10262-1982 Vs IS 10262-2009

Difference between IS 10262-1982 Vs IS 10262-2009

IS 10262-1982 Vs IS 10262-2009:                 IS:10262 is the code specified by Bureau of Indian Standards for Concrete Mix Design. The code came to existence in the year 1982. Keeping pace with the advancing technology the code has been revised in December 2009. Significant changes have been made in the revised version and a brief discussion is presented in this paper comparing the two versions of IS:10262. The basic points where the guidelines have been modified are discussed. Besides one numerical example has been solved using guidelines of both the versions to understand the differences. Though the 2009 version encourages mixing of mineral admixtures to meet greater challenges of modern concreting, a simple example is considered with use of no additives. Introduction Mix Design of Concrete is the process of deciding the proportions of the ingredients of concrete so as to be produced most economically, that would satisfy the desired properties of fresh and hardened concrete as well. In simpler words, the concrete should be well workable when fresh and the designed compressive strength as well as durability should be achieved at hardening. The wide use of concrete as the basic construction material may be due to its adaptability for a wide range of strength and workability. To achieve different strength requirements, it is the “Mix-design process” that makes the difference as the basic ingredients are same all the way. Very likely to other methods of Concrete Mix Design, Guidelines recommended by Bureau of Indian Standards for concrete mix design is based on certain empirical relations established through vast number of experiments conducted upon materials used in Indian conditions. IS: 10262 is the specified code to serve the purpose. This code came to being in the year 1982. So IS: 10262-1982 had been evolved to guide the concreting technology being followed at that period. But at present due to demand in high strength concrete and for economic production, use of supplementary materials has become essential. With the advanced technology a number of additives have been identified and are being used extensively now-a –days. These additives are not only enhancing the quality of concreting but also make the process economic and eco-friendly too. So keeping these in view the necessary modifications were felt essential and the revised version of the code as IS: 10262-2009-“Concrete Mix Design-Guidelines” has met this in time. The revised version encourages use of supplementary cementitious materials and water reducing additives. Besides, being consistent with specifications of IS: 456-2000, necessary modifications have been made. IS: 10262-1982 Vs IS: 10262-2009-The key modifications i. Title of the Code The modified title of the code itself makes the designer feel little flexible. i.e. “IS 10262-1982-Recommended guidelines for concrete mix design” modified as “IS 10262-2009-Concrete Mix proportioning Guidelines.” ii. Strength & Durability The 1982 version considers strength as the governing criteria for durability and so also for the mix design process. But according to the revised one strength may be a factor for acceptance but may not assures durability. iii. Air Content IS: 10262-1982 considers expected air content of 1% to 3% in the design process depending on the nominal maximum size of aggregates. IS: 10262-2009 eliminates consideration of air content in the mix proportion calculation as it’s not of much significance. iv. Water Cement Ratio The old version suggested that selection of preliminary free w/c ratio may be adopted from established relationships presented in form of graph as generalized w/c ratio curves for different cement strengths. Accordingly six ready reference curves were there namely A to F for a wide range of cement strengths from 325kg/cm2 to 625kg/cm2. This selected w/c ratio is to be checked against limiting w/c ratio for durability. The revised version encourages establishing the relationships for actually used material. Otherwise it suggests to consider it from the specified table (Table-5) of IS: 456 for desired exposure condition as preliminary w/c ratio that has to be further checked for limiting value ensuring durability. v. Measure of Workability IS: 10262-1982 considers compaction factor as the measure of workability. In revised one, slump is considered as the measure of workability. Measurement of workability as slump is more convenient, widely used at sites and is better acceptable. vi. Mineral Additives The revised code provides guidelines for addition of supplementary cementitious additives. So additives like fly ash, silica fume, ground granulated blast furnace slag, rice husk ash etc. can be used in concrete mix provided the strength and durability requirement are met with. So as per the revised code the concrete is no longer a four component system (cement, sand, coarse aggregates & water) as considered in the previous version, but it is much more. vii. Calculation of water content The quantity of water to be used plays a vital role in concrete mix design. Agreeing with the old guidelines, values of water content have been specified in terms of kg per cubic meter of concrete depending upon the nominal maximum size of aggregates which can be considered as starting selection point of water content. IS: 10262-2009 allows use of water reducers/ super plasticizers and also specifies the alteration in water content accordingly. Further water adjustment was specified in terms of variation of compaction factor in the older version whereas the same has been remoulded in terms of slump variation (+3% for every 25mm slump over 50mm) in the revised one. viii. Estimations of Coarse and Fine Aggregates The 1982 publication specifies ratio of fine aggregates to all-in-aggregates from which coarse aggregates content can be derived. In revised one the volume of coarse aggregates per unit volume of total aggregates for different zones of fine aggregates and different maximum nominal size of aggregates has been tabulated from which the fine aggregates content has to be derived. Further in the earlier guidelines necessary adjustments in sand content has been suggested depending on its grading zone, whereas the recent guidelines allow reduction in coarse aggregates content for better workability, provided other desired properties are satisfied. ix. Miscellaneous Besides the other points to be bolded are • The standard is applicable for ordinary and standard grades of concrete. • Various requirements have been modified in line with the requirements of IS: 456-2000-Plain and reinforced concrete-Code of practice. • Other illustrations like trial mixes, numerical example etc have been reviewed and modified. • An example illustrating mix proportioning with supplementary cementitious additive (fly ash) has been included.