Paper of Efflorescence in Bricks and Efflorescence and Leaching in Concrete by Sir. Kaushal Kishore
Materials Engineer, Roorkee

Efflorescence is the usual terms for deposit of soluble salts, formed in or near the surface of a porous material, as a result of evaporation of water in which they have been dissolved.

EFFLORESCENCE IN BRICKS:
Usually sulphate of magnesium, calcium, sulphate and carbonate (and sometimes chloride and nitrates) of sodium and potassium are found in efflorescence. These salts may be traced to the brick itself, sand used in construction, the foundation soil, ground water, water used in the construction and loose earth left over in contact with brick work. Bricks with magnesium sulphate content higher than 0.05 percent should not be used in construction. Soluble salt content in sand (chloride and sulphate together) should not exceed 0.1 percent.

Water, if it finds access to brick work, moves along its pores by capillary action and carries with it dissolved salts. As the solution evaporates from the exposed surface of the brick work, the salts are left as deposit on the surface or on layers just below it. Disintegration or flaking of the brick surface is caused by the mechanical force exerted by salts as these crystallize just below the exposed surface. Magnesium sulphate, in particular, disintegrates bricks and pushes out plaster.

REMEDIES:
1. Well fired bricks should be used in construction.
2. Sand should be tested for its salt content.
3. Proper D.P.C. should be provided in the building.
4. Efflorescence on brick work traceable to salts in the materials can be removed by dry brushing and washing repeatedly. Such efflorescence may re-appear in dry season but usually are less in intensity. Finally these disappear as the salt content of the bricks is gradually leached out.

TESTING BRICKS FOR EFFLORESCENCE
Distilled water to be filled in a dish of suitable size. The dish should be made of glass, porcelain or glazed stone ware. Place the end of the bricks in the dish, the depth of immersion in water being 25 mm. Place the whole arrangements in a warm (for example, 20 to 30^oC) well ventilated room until all the water in the dish is absorbed by the specimen and the surface water evaporate. Cover the dish with suitable cover, so that excessive evaporation from the dish may not occur. When the water has been absorbed and bricks appear to be dry, place a similar quantity of water in the dish and allow it to evaporate as before. Examine the bricks for efflorescence after the second evaporation and report the results as:

(a) NIL – When there is not perceptible deposit of efflorescence.
(b) SLIGHT- Not more than 10% area of the brick covered with a thin deposit of salt.
(c) MODERATE- Covering upto 50% area of the brick.
(d) HEAVY- Covering 50% or more but unaccompanied by powdering or flacking of the brick surface.
(e) SERIOUS- When, there is a heavy deposit of salts accompanied by powdering and/or flacking of the exposed surfaces.

EFFLORESCENCE AND LEACHING IN CONCRETE:
When water percolates through poorly compacted concrete or through cracks or along badly made joints, the lime compounds with in the concrete leached out which leads to the formation of salt deposits on the surface of concrete, known as efflorescence. This caused primarily by calcium hydroxide Ca(OH)₂ one of the hydration products and slightly soluble in water, migrating to concrete surface through the capillary system. After evaporation, the solid Ca (OH)₂ reacts with the atmospheric carbon dioxide CO₂ to form calcium carbonate CaCO₃, a white deposit on the concrete surface.

Early efflorescence can be removed with a brush and water. Heavy deposits may require acid treatment of the surface of the concrete. The acid used is HCl diluted from the concentrated form in a ration of 1:20 or 1:10. The action of the acid stops when it has been used up by the reaction with lime, but the concrete should be washed in order to remove the salts which have been formed.

Efflorescence and leaching in concrete is harmful. In addition to blemish and ugly appearance, the process of carbonation of concrete is accelerated. In reinforced concrete, the chances of corrosion of steel are increased due to carbonation and higher permeability of concrete. It is therefore necessary the concrete making materials should be of good quality, mineral and chemical admixtures preferably be used, properly proportioned (preferable design mixes) as per required durability and grade of concrete. All the materials should be properly mixed, placed, compacted, finished and cured.

REFERENCES:
1. I.S. : 3495 (Part-III)- 1976 – Method of tests of burnt clay building brick) Part-III, determination of efflorescence (Second Revision)
2. A.M. Neville, Properties of Concrete, Fourth Edition.

We are thankful to Sir Kaushal Kishore for publishing his paper on Efflorescence. This paper will help civil engineers understand what is Efflorescence and how can they get rid of it

By
Er. Kaushal Kishore ,
Materials Engineer, Roorkee

INTRODUCTION:
A green building is that building which is constructed at a well planed location with proper design and sustainable materials. Fitted and painted with eco friendly materials. The building should gives to its occupants healthy and comfortable environment in all climates. It remains cool in summer, warm in winter, inside fully protected from rain, gives natural pollution free air and light through doors, windows and ventilators without any artificial means. For particular requirements it has solar, wind power and eco friendly electrical, mechanical etc. devices.

A green building should have all safety devices. It should be provided with potable water, having proper drainage, severage and rainwater harvesting system. The building should be surrounded with trees, plants and grass to provide natural greenery. Can the above building be possible when day by day the population in India is increasing at a very fast rate? The facts may be found from the following table.

Table: 1 Human population per sq.km of country area:

With the increase in the population the house demand will also increase. For India it is of the top concern as by the year 2049 having the same country area 581 persons sharing recourses of one sq. Km. area against China 141 and USA only 49. From the present day crowd, it can be well imagine what will be the crowd condition of India in 2049. A drastic action is needed otherwise it will be too late to cope with this situation. There will be more slumps. By 2011 India will have 9.31 crore slump dwellers in which 31.63 lakhs people will be living in slumps in Delhi alone.

Some builders have a novel way to attract the client for the apartments they are going to build or already build. They gives big advertisement in green colour showing apartment surrounded by tall green trees. When you go to such site you will not found the trees of your dream. The other misleading advertisement is that the apartment has 70% open lush green area. The facts will be known when you calculate the actual open area for one house you will be going to live. See the following table:

Table 2: Actual open area shared by number of people:

From the above table it can be seen that in a single storey apartment of 24 houses for 96 persons the open area is 25200 sq.ft., whereas for a 15 storey apartment of 360 houses for 1440 persons the open area is again same only 25200 sq.ft. Accordingly if a builder claim that his 15 storey apartment has 70% open area of covered area then the open area should be 378000 sq.ft. and not 25200 sq.ft.

Suppose per house there is one car, then a single storey apartment will have 24 cars and a 15 storey apartment will have 360 cars. In a 15 storey apartment where is the open space will be left for trees. To maintain our natural environment there must be one tree for each house. Accordingly in a 15 storey apartment having 360 houses there should be 360 tall trees. Have we such greenery in any of the apartment in our cities. How then they may be called green houses and claiming 70% lush green open area. The fact is we are living in congested places where we can never feel comfortable and enjoy the life of natural environment.

URBAN HEAT ISLAND MITIGATION
Urban areas have been found to have air temperature 2⁰C to 5⁰C warmer than the surrounding country side. This phenomenon known as the URBAN HEAT ISLAND EFFECT. There are number of ways one can fight the urban heat island at home and around the city.

1. Planting Trees: Trees are one of our most important allies in the fight against the urban heat island effect. Air temperatures directly under trees can be as much as 10⁰C cooler than temperature over unshaded blacktop. Trees can be sited stragically to shade roofs, pavement, walls, and other surfaces, keeping them cooler and reducing energy bills. Trees also provided a cooling effect through evapotranspiration. Other vegetation, including grass etc. also provides cooling effects, though not usually as significant as trees.

2. Green Roofs: Green roofs are roofs planted with grasses, flowers, or other vegetation. Like trees planted at ground level, the vegetation shades the surface, keeping it cooler. Reducing the urban heat island effect, isn’t the only benefit of green roofs- they can also be used to grow fresh local products in the city, and they significantly reduce storm water run off as well. Local birds will be attracted on the roof greenery and make their nest upon it.

3. Permeable Pavement: Many types of permeable pavement reduces the urban heat island effect in one or more ways. For example, many grid or block pavers incorporate grass or other ground covers, which help shade the surface of the pavement and increase local evapotranspiration. Porous pavements often have much lower total mass than asphalt or concrete, reducing the amount of heat they absorb and many permeable pavements are lighter colored than traditional pavement as well.

4. Building Walls: The walls of building should be painted with solar reflective paints.

5. Roofs: The roof of house remain expose to direct sun rays most of the day time. The traditional methods of keeping roof surface cool are lime terracing, mud phuska and brick bat coba treatment. These methods are not only time consuming, costly but also increases the dead load on roof. The new and very convenient method is to paint the roof surface white with solar reflective paint/coating.
Solar reflective coating is an acrylic based coating which provides weather proofing and heat insulation to the exposed roof. This can be used for coating RB, RCC roof top surface, asbestos cement roofing sheets, galvanized zinc sheets as well as aluminium sheets. With such coating temperature may be lower upto 10⁰C thus giving cooling comfort to the occupants of house and also reduces the load on Air Conditioner.

We are thankful to Sir Kaushal Kishore for publishing his unpublished research paper here on the website. This would be of great use to all the civil engineers who work are looking for information regarding Green Buildings .

By
Er. Kaushal Kishore ,
Materials Engineer, Roorkee

INTRODUCTION
Concrete can be converted into precast masonry units such as Hollow and Solid normal and light weight concrete blocks of suitable size to be used for load and non-load bearing units for wallings. Use of such concrete blocks are more appropriate in region where soil bricks are costly, poor in strength and are not available. Depending upon the structural requirements of masonry unit, concrete mixes can be designed using ingredients available locally or if not found suitable then with in the most economical distance. The concrete mix used for normal hollow and solid blocks shall not be richer than one part by volume of cement to 6 parts by volume of combined room dry aggregates before mixing. Hollow concrete blocks for normal work used in masonry when reinforced is used shall not be leaner than 1 part cement to 8 parts room dry sand by volume. The mixes are designed with the available materials to give overall economy and the required properties of the products. The hollow load bearing concrete blocks of the standard size 400 x 200 x 200 mm will weight between 17 and 26 kg (1063 to 1625 kg/m3) when made with normal weight aggregates. Normal weight blocks are made with cement, sand, gravel, crushed stone and air-cooled slag. The grading for sand used in Hollow concrete block shall be as given below:
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We are pleased to announce that Sir Kaushal Kishore who has been helping engineering students all over the world with his useful research and project paper submissions here at engineeringcivil.com has been awarded Vishwa Karma Award 2011 by CONSTRUCTION INDUSTRY DECELOPMENT COUNCIL (CIDC Set up by Planning Commission Govt of India) for Category Academician/Technologist/Scientist/Innovator on 7th March 2011 at New Delhi.

We wish him heartiest congratulations and hope he will win more and more awards and show us the way to make this Civil Engineering Portal a great learning website for civil engineers.

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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