What is Efflorescence in Bricks and Concrete?

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.

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.

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.

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 30oC) 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.

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.

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

Experimental Study On The Ductile Characteristics Of Hybrid Ferrocement Slabs

Research Paper by
A.Dhasarathan1, Dr. R. Thenmozhi2, Mrs. S. Deepa Shree 3
1 PG Scholar, Government College of Technology, Coimbatore
2Associate Professor, Government College of Technology, Coimbatore
3 Assistant Professor, Jansons Institute of Technology, Coimbatore

Ferro cement elements are generally more ductile when compared to conventional reinforced concrete elements but post peak portion of load- deflection curve in bending test of Ferro cement elements reveals that failure occur either due to mortar failure in compression or due to failure of extreme layers of mesh. In this paper a study has been made on the ductility behaviour of hybrid Ferro cement elements by strengthening it in its tension zone by using GFRP layers and by adding polypropylene fibers into concrete. In present study, slab specimens of each 700 mm X 300 mm with varying parameters such as number of layers of mesh (2 & 3 bundled), layers of GFRP sheets (0 & 1) along with and without a specified proportion (0.30%) of polypropylene fibers were cast. Two point loading test was conducted on slabs and parameters such as ultimate moment capacity, ductility ratio and crack pattern were observed. From experimental results it was found that wrapping of GFRP in tension zone of slab increases confinement of bottom zone and using of fibre reinforced concrete has an influence on ductility and flexural capacities of ferrocement slabs.

Keywords: ferrocement slabs, GFRP wrapping, fibre reinforcement, ductility factors
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Behavioural Studies On Hollow Double Skinned Steel Concrete Composite Columns

Research Paper by N.Balasubramanian,R.B.Karthika and Dr.R.Thenmozhi
Government College Of Technology, Coimbatore-641 013, India

This paper comprises of the experimental study of eight double skinned concrete filled steel tubular (DSCFT ) beam columns of concentrically placed circular sections filled with self compacting concrete. Tests on the specimens were made by applying eccentric loads. The main experimental parameters for beam-columns were slenderness ratio and load eccentricity. Testing of specimens investigates the behaviour on load deflection, confinement effect, and the strength of the columns. The experimental observations were shown by load-deflection curves. Various characteristics such as strength, stiffness, ductility and failure mode are discussed. The predicted load versus deformation relationships are in good agreement with beam-column test results. The DSCFT columns in-filled with SCC show good strength and ductility. Modified equations are suggested to find the ultimate compressive strength of DSCFT columns filled with SCC.

Keywords : Composite; Double skinned concrete filled steel tubular columns; D/t thickness, fabrication and casting, load deflection, ductility.

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Durability of Flyash Based Geopolymer Concrete

This paper by SOURADEEP GUPTA (National University of Singapore) is aimed at discussing properties of geopolymer concrete, how these differ from properties of ordinary Portland cement, durability properties of fly ash based geopolymer concrete and its advantage when used as a construction material as well. Also some focus has been made on relevant issues that need to be solved and research needs to make it a better construction material.

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What are Green Buildings?

Er. Kaushal Kishore ,
Materials Engineer, Roorkee

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:

Storey of building

Total houses

Covered area sq.ft.

Ground open area sq.ft.

Persons living in total apartment





















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 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 .

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