Concrete mix proportions pdf

Mix ratios are decided based upon the type of construction structures and mix designs. Different Grades of Concrete denotes its strength for required construction. For example if the concrete mix is of M20 Grade then the compressive strength will be 20 MPa.

So, What is 20 MPa here?? Concrete mix design is process of preparation of concrete with suitable proportion of ingredients to meet the required strength and durability of concrete structure. Every ingredient of concrete consists different properties so, it is not an easy task to get economical and good concrete mix.

The types and advantages of concrete mix design are discussed below. Previously the specification for concrete was proportion of Cement, Sand and Course Aggregates. The fixed ratio of these was to ensure the strength to the structure. Nominal concrete mix are low grade concrete mixes which are used for small and unimportant works. In this method, fine aggregate quantity is fixed irrespective of cement and coarse aggregate proportions.

Hence, the quality of concrete mix will be varied and required strength may not be obtained. In Nominal mix design water-cement ratio also not specified. Grades of concrete M20 and below are prepared by the Nominal mix design. For higher grade designed concrete mix is preferred. As per Indian Standards IS — concrete mixes are segregated into different grades.

It starts from M5 and goes up to M The proportion of the material is determined by the concrete mix expert in this method. In design mix the concrete production is with appropriate properties. In Design mix there is no guide for right mix proportions it follows the economical method as per the requirement. It is followed by standard mixes — quantities of dry materials per cubic meter and by plunge. SSD aggregate neither absorbs water from nor contributes water to the concrete mixture.

This is typically only achieved in laboratory conditions. Specific gravity — The SG of any material is the unit weight of that material divided by the unit weight of water at room temperature. An aggregate with an SG of 2. To understand this concept, consider an iron anvil being dropped into a tub of water and quickly sinking to the bottom.

The anvil sinks because the SG of the iron is greater than that of water. Now, if the tub was filled with mercury instead of water, the iron anvil would float because the SG of the iron is less than that of mercury.

Absolute volume — The AV of a granular material is the volume comprised by only the solid matter in a given space. It does not include the volume of the voids between the particles. The AV of a material is computed as follows:. For example, the SG of a certain oven-dry coarse aggregate is 2. The unit weight of water is The absolute volume of a pound sample of the aggregate would be:. The AV of a concrete mix can be determined if the weight and SG of the components are known.

For a concrete sample mix containing 90 pounds of coarse aggregate with an SG of 2. ACI If you design concrete mixtures, it is definitely required reading. This standard provides a starting point, which is a basic design that would need to be tested and adjusted for your specific materials. Most precast plants have a long history with their materials and understand how they perform in concrete.

When it comes to adjusting fine and coarse aggregate ratios, approval can only be confirmed through in-plant testing with all of your other local raw materials. You typically use around 1, pounds of coarse aggregate. With these materials and to reach an adequate stripping strength within 15 hours, you need to have a maximum water-cementitious ratio of 0. First, we need to know the SG of each material. Also, we will need to calculate the volume of the entrained air in the mix. After calculating the volume of each material, we must add them up.

Frank Bowen right and Paul Ramsburg experiment in the laboratory to find the optimum proportions for their concrete mix design examples.

In our example, the total volume of all materials except sand is Since there are 27 ft. This results in 8. The complete design consists of pounds of cement, pounds of fly ash, pounds of water, 1, pounds of coarse aggregate and 1, pounds of sand. How did we get pounds of water from 0. Civil Lead. It is the process of determination or selection of the relative proportion of concrete ingredients that means cement, sand , coarse aggregate, and water to obtain concrete of desired quality.

From the strength point of view and economy, the main objective to select the fine and coarse aggregate in such a ratio to get a dense mix with minimum voids using the least amount of cement.

The choice of a concrete mix depends upon the types and quality of work; it also depends upon the load coming on the structure formed and climatic conditions. In a nominal mix quantity of cement , sand and aggregate are fixed. This mix offers simplicity under normal circumstances. It provides a margin of strength above that specified.

The strength of nominal mix concrete varied widely for given workability due to the variation of mix ingredients. M 15 , M 20 The nominal concrete mix of a fixed proportion of cement, sand and aggregate provide considerable variation in strength resulting in the poor or over-rich mix. Hence minimum compressive strength has been assigned in many proportions and termed as the standard mix.

In design mix proportion of cement, coarse aggregate, fine aggregate and water are determined to get a mix of given strength, proper workability and durability with the economy. Determining the proportion of cement, fine aggregate, and coarse aggregate for concrete mix is known as the proportioning of concrete. The principle of proportioning aggregate is that the smaller particle will fill up the voids between large particles.

A well proportioned concrete mix requires a minimum amount of cement per unit volume. By this method such mixes as Concrete of varying strength and denseness due to the deficiency of proper control of the quantity of water that goes into a concrete batch.