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Dr. Aminul Islam Laskar Laxmi Publications PDF



Concrete Mix Design

Proper design of concrete mixtures is intended to obtain such proportioning of ingredients that will produce concrete with high durability performance during the desired designed life of a structure. It is always difficult to develop a theoretical mix design method that can be used universally with any combination of cement, any aggregates because the criteria of all the components are too broad. Moreover, the same properties of fresh and hardened properties of concrete can be achieved in different ways from the same materials. A mix design method only provides a starting mix design that will have to be modified to meet the desired concrete characteristics. In spite of the fact that mix proportioning is an art, it is unquestionable that some scientific principles can be used as a basis for mix calculation.


Most proportioning methods are based on concrete compressive strength. Therefore, it is important to define the exact value of concrete compressive strength that has to be achieved before using any mix design method. Many other engineering properties of concrete appear to be generally related to its compressive strength. Indian Standards such as IS 456: 2000 stipulates concrete compressive strength in terms of grades of concrete. For example, M 20 refers to a concrete mix having characteristics strength 20 MPa. Here M stands for mix and 20 refer to the characteristic strength. Characteristics strength (fck) of concrete is defined as the value of the strength of concrete below which not more than 5% of the test results are expected to fall. The following basic assumptions are made for the design of conventional concrete:

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Dr. Rashmi Tyagi Laxmi Publications PDF





The world depends for its energy requirement upon three major fossil fuels—coal, natural gas and oil, which would become exhausted completely in near future (coal may last for 200 years, natural gas and oil for 40 years). Realizing energy crisis during 1970s when the oil prices increased massively and due to environmental awareness, the scientists are trying to find the alternative non-conventional cleaner sources of energy, like wind, solar, tidal and wave, geothermal and bio-energy. Photosynthetic organisms convert dilute solar energy into more concentrated chemical energy (e.g., carbohydrates) with 3–4% efficiency, making the biomass (2 × 1011 tonnes C fixation/ year). Photosynthetically derived biomass (which does not have much calorific value), like forest, agricultural and animal residues and domestic organic wastes can be converted by fermentation into clean renewable fuels (like alcohol and CH4) possessing quite higher energy value. With time, continuous depletion of fossil fuels is making them increasingly expensive and in such situation biofuels may become more economic. Biofuels can be used for cooking, generation of electricity or in automobile engines. The CO2 released during their combustion is entrapped in the photosynthesis (which also produces O2) for biomass production and, thus, do not damage the environment as the fossil fuels do.

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R. K. Jangda Laxmi Publications PDF




Pointer is a concept, which everybody has been using since childhood. During the schooldays it was often required by the class teacher that all students should stand roll number wise in a line. Believe it or not, you have always executed that order perfectly. Have you ever thought that how could you do that? The key to this success is a pointer you have always maintained in you, which always pointed to the person before you i.e., you remembered the roll number of the person who should come before you. The same is true for all students.


A pointer always point to something, here in our case a student type.

A pointer keeps an information here in our case roll number (address) of the student.

There are many such examples where such pointers are used. Some of these are newspaper or magazines. It is often noticed that when an article is not covered in the current column, then a page and column number is mentioned in the end, i.e., pointing to the location where to continue. In cinema hall booking ticket, the seat numbers are written on the ticket.

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Hari Mohan Pandey Laxmi Publications PDF





Structured programming (sometimes known as modular programming) is a subset of procedural programming that enforces a logical structure in the programming being written to make it more efficient and easier to understand and modify. Structured programming frequently employes a top-down design model, in which developers map out the overall program structure into separate subsections. A defined function or set of similar functions is coded in a separate modules can be reused in other programs. After a module has been tested individually, it is then integrated with other modules into the overall program structure. Program flow follows a simple hierarchical model that employs looping constructs such as �for�, �repeat� and �while�.

Use of the �Go To� statement is discouraged.

Structured programming was first suggested by Corrado Bohm and Guiseppe Jacopini. The two mathematicians demonstrated that any computer program can be written with just three structures : decision, sequences, and loops.

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P.S.Sona Laxmi Publications PDF

238 A Practical Manual of Pharmaceutical Engineering


1. R.H Perry, D. Green, Perry�s chemical engineer�s handbook, 6th edition, Mcgraw-Hill book Company, Singapore, 1984.

2. W.L. Mc- Cabe , J.T.Smith, P.Harriott, Unit operations of chemical enginnering, 5th edition, McGrawHill Book company, Singapore, 1993.

3. M.E Aulton, Pharmaceutics, ELBS Edition, Churchill Livingstone Ltd, Hongkong, 1990.

4. W.L. Badger, J.T Banchero, Introduction to chemical engineering, Mc Graw-Hill Book Company,


5. E.A. Raswlis, Bentley�s Textbook of pharmaceutics, 8th edition, Bailiere Tindal, London, 1977.

6. S.J carter, Cooper and Gunn�s Tutorial pharmacy, 6th edition, Kothari Book Depot, Bombay, 1972.

7. L.Lachman, H.A. Liberman, J.L Kanig, The theory and practice of industrial pharmacy, 3rd edition,Lea&

Febiger, Philadelphia,1985.

8. Martin, J.Swarbrick, A.Cammarata, Physical Pharmacy, 3rd edition, Varghese publishing house,

Bombay, 1991.

9. C.V.S Subramanyam,J.Thimmasetty,Sarasija suresh, V KusumDevi, Textbook of pharmaceutical engineering, Vallabh Prakashan, Delhi, 2000.

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