CONCRETE MIX DESIGN FORMAT FOR COMPUTERS AS PER IS10262-2009
Authors: G Sankara , P V Sivapullaiah 
Published: June 2024

Concrete is one of the most widely used construction material across the globe in various civil infrastructure activities. It is also a material which is difficult to produce consistently to meet the prescribed specifications. Concrete is a composite material consisting of a cementitious paste (cement+ water) and inert aggregate (coarse and fine) filler materials. Properties and quality of locally available component materials, tools and equipment used for proportioning, mixing and vibrating, skills of the workers and supervision involved and exposure conditions etc., affect the properties of the concrete. Quality of concrete is evaluated against its performance in meeting the requirements of strength, durability and serviceability in hardened state and workability in fresh condition. These requirements vary based on the intended functional units like columns, beams, foundations, pre stressed concrete and pavements etc. and also from country to country. Several countries have stipulated standards for these parameters. To achieve these specified properties, suitable constituent materials need to be selected and they should be used in certain proportions. These proportions are arrived at based on experience and some empirical relations. It shall also be done in a cost effective manner. At the initial stage data about proposed constituent materials and the variables that influence the mix design need to be collected. This data includes desired strength of concrete, type of cement-Ordinary Portland/Portland pozzolana, quantity of cement and admixtures, water cement ratio, sizes and properties of aggregates, workability requirements based on location points of placing and transportation of the concrete on the job etc. Durability of concrete both in plastic and hardened state will be influenced by the environmental conditions it will be exposed to like weather, submergence in water, burial under soil and exposure to chemical fumes etc. These conditions can lead to deterioration of concrete. In India the recommendations of IS 10262 for designing concrete mixes are followed. It provides formulas, tables and other information for deciding water cement ratio, water content, quantities of coarse and fine aggregate etc. This code need to be studied in conjunction with IS 456 and other IS codes for relevant data. Preliminary theoretical quantities of the concrete constituents can be obtained by following the steps illustrated in the examples given in the code. These quantities need to be endorsed by conducting tests on laboratory and filed/plant trial mixes. Materials from the same sources need to be used in both trial mixes. Suitable adjustments shall be made to the theoretical quantities to arrive at actual quantities to produce concrete that meets the stipulated specifications. A lot of variables like grade of concrete, specific gravity of materials, zone of sand, shape of aggregate etc., many provisions specified in the codes, multiple steps, several repetitions and numerous calculations are involved in obtaining a reliable concrete mix design. Manually handling these computations is tedious. With the size, complexity and importance of structures, accuracy of procedures and calculations increases further. Computer aided programs and spreadsheets can help a lot in reducing the labour involved in this work. They can be made user friendly by including the provisions of the codes, tables, formulas and other data. The results can be tabulated in the desired format for both one cum of concrete and desired quantity of concrete. Design calculations for alternative constituent materials like fly ash and M-sand that help in conserving nature which may have considerably different properties, are also presented.