Mix Design and Pumped Concrete

Materials Engineer, Roorkee

A simple method of concrete mix design for pumpable concrete based on an estimated weight of the concrete per unit volume is described in the paper. The tables and figures presented are worked out by the author from a wide range of Indian materials. The method is suitable for normal weight concrete with admixture.

Pumped concrete may be defined as concrete that is conveyed by pressure through either rigid pipe or flexible hose and discharged directly into the desired area. Pumping may be used for most all concrete construction, but is especially useful where space or access for construction equipment is limited.
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Concrete Mix Design – ITS Acceptance

Materials Engineer, Roorkee

Concrete mix design is the process of choosing suitable ingredient of concrete and determining their relative quantities with the object of producing as economically as possible concrete of certain minimum properties, notable workability, strength and durability. It should be explained that an exact determination of mix proportions by means of table or computer data is generally not possible. The materials used are essentially variable and many of their properties cannot be assessed truly quantitatively. A Laboratory trial mix does not provide the final answer even when the moisture condition of aggregates are taken into account. Only a mix made and used on the site can guarantee that all properties of the concrete are satisfactory in every detail for the particular job in hand. In fact mix selection requires a knowledge of the properties of concrete and experimental data, and above all the experience of the expert who conduct the mix design. The selection of mix proportions is an art as much as a science. It is not enough to select a suitable concrete mix; it is also necessary to ensure a proper execution of all the operation involved in concreting. It cannot be stated too strongly that, competently used, concrete is a very successful construction material but, in the literal service of the word, concrete is not fool proof. The mix proportions once chosen, cannot expected to remain entirely immutable because the properties of the ingredients (cement, sand, aggregate, water and admixture) may vary from time to time.
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Concrete Mix Design with Fly Ash and Superplasticizer

Materials Engineer, Roorkee

Fly ash or pulverished fuel ash (pfa) is a finely divided powder thrown out as a waste material at the thermal power plants using pulverized coal for raising steam in the boilers. In the building industry, the use of fly ash a part replacement of cement in mortar and concrete at the construction site has been made all over the world including India and is well known. The important building materials which can be produced from fly ash are:

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M-80 Grade Pumpable Concrete

Kaushal Kishore
Materials Engineer, Roorkee

A mix of M-80 Grade suitable for pumped concrete is to be designed with the following materials and detail.

1. OPC 53 Grade, 7-day strength 52.5 N/mm2, Spgr 3.15

2. Silica Fume Specific Gravity 2.20

3. Standard deviation for the mix 5.0 N/mm2

4. Grading and properties of river sand and 12.5 mm crushed aggregate are given in Table-1

5. Superplasticizer based on modified Polycarboxylate, specific gravity 1.06, liquid pH 6.0. With the given set of materials, it was found that at a dosages of 2.5 % bwc it gives a reduction of 30% of water for the required slump of 100 mm after one hour at the average day site temperature of 37 degree C.
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Mix Design For Concrete Roads As Per IRC:15-2011

Kaushal Kishore, Materials Engineer, Roorkee

The stresses induced in concrete pavements are mainly flexural. Therefore flexural strength is more often specified than compressive strength in the design of concrete mixes for pavement construction. A simple method of concrete mix design based on flexural strength for normal weight concrete mixes is described in the paper.

Usual criterion for the strength of concrete in the building industry is the compressive strength, which is considered as a measure of quality concrete. However, in pavement constructions, such as highway and airport runway, the flexural strength of concrete is considered more important, as the stresses induced in concrete pavements are mainly flexural. Therefore, flexural strength is more often specified than compressive strength in the design of concrete mixes for pavement construction. It is not perfectly reliable to predict flexural strength from compressive strength. Further, various codes of the world specified that the paving concrete mixes should preferably be designed in the laboratory and controlled in the field on the basis of its flexural strength. Therefore, there is a need to design concrete mixes based on flexural strength.
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