Mix Design

The main objective of asphalt mix design is to achieve a mix with economical blending of aggregates with asphalt to achieve the following :

(i) workability to facilitate easy placement of bituminous materials without experiencing segregation;
(ii) sufficient stability so that under traffic loads the pavement will not undergo distortion and displacement;
(iii) durability by having sufficient asphalt;
(iv) sufficient air voids

In asphalt mix design, high durability is usually obtained at the expense of low stability. Hence, a balance has to be stricken between the durability and stability requirements.

This question is taken from book named – A Self Learning Manual – Mastering Different Fields of Civil Engineering Works (VC-Q-A-Method) by Vincent T. H. CHU.

Good quality concrete starts with the quality of materials, cost effective designs is actually a by-product of selecting the best quality material and good construction practices. Following are 10 Things to remember during Concrete Mix Design and Concrete Trials.
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By
Er. Kaushal Kishore ,
Materials Engineer, Roorkee

In India 0.93 kg of CO₂ is emitted in the production of one kg of cement. In the financial year 2009-10 India produces 200 million tonnes of cement. In the production of this cement 186 million tonnes of CO₂ was emitted in the atmosphere during financial year of 2009-10.

The availability of water in India per person per year in 1950 was 5177 cu.m. In the year 2009 it is reduces to 1700 cu.m.

If 50 million tonnes cement in making concrete uses water reducers 7500000 tonnes of cement can be saved. 3750000 kl of potable water will be saved and the saving of Rs. 3300 crores per year to construction industry. This amount is worked out after adjusting the cost of water reducers. Less cement used means less cement required to be produce by the cement factories resulting 6975000 tonnes of CO₂ will be prevented to be emitted to the atmosphere. These are worked out with an average saving of 15% cement and 15% water.

CO₂ emission is word problem, but for India in addition to CO2 it has problems of Air, Water, Soil, Food and Noise pollutions. Less densily populated countries may cope with these problems but for India it is of the top concern. The population figures of 2009 is, India 350 person per sq.km, China 132 person per sq.km and USA only 34 person per sq.km. The figures of 2006 CO¬2 emissions are USA 658.60 tonnes per sq.km, China 611.76 tonnes per sq.km and India 459.35 tonnes per sq.km. Every one should contribute his or her efforts to save the environment from pollution. Those involve in the construction activities can contribute their share by proper design of concrete Mixes. This is best illustrated by the following examples.
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Concrete mix design – M70 grade of concrete provided here is for reference purpose only. Actual site conditions vary and thus this should be adjusted as per the location and other factors.

A. Design Stipulation:
Characteristic comprehensive Strength @ 28 days = 70 N/mm²
Maximum size of aggregate = 20 mm
Degree of workability = Collapsible
Degree of quality control = Good
Type of exposure = Severe
Minimum cement content as per is 456-2000

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Concrete mix design – M60 grade of concrete provided here is for reference purpose only. Actual site conditions vary and thus this should be adjusted as per the location and other factors.

A. Design Stipulation:
Charastaristic comprehensive Strength @ 28 days = 60 N/mm²
Maximum size of aggregate = 20 mm
Degree of workability = Collapsible
Degree of quality control = Good
Type of exposure = Severe
Minimum cement content as per is 456-2000

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