Definition, causes and remedies of efflorescence in masonry & other building surfaces

Efflorescence stands for a fine, white or greyish, powdery deposit of water-soluble salts that is present on brick, concrete, stone, stucco or other building surfaces when the water vaporizes. Besides, efflorescence also exists on floors and walls and requires special attention. It is often mentioned as "whiskers”.

These efflorescent salt deposits is found at the worst times, normally about a month as soon as the building is developed, and sometimes as long as a year after finishing of structure.

Efflorescence is found in both indoors and exterior, and it can differ in frequency and intensity because of the existence of moisture and temperature.

The efflorescence happens for the following three factors :-

• Existence of water-soluble
• Salts are converted into a soluble solution because of moisture content.
• The transmission of salts through a material to its surface that leads to vaporization of the moisture and cause the salts to crystallize and thus efflorescence is formed.

Moisture is mainly formed due to water, rain and snow and may affect the extent of efflorescence. Condensation, groundwater tapering and interior activities also may influence the extent of moisture formation.

In several cases it is found that efflorescence may happen throughout home construction. If masonry units are left behind all through the night during construction, they can consume moisture from damp soil and rain. It is recommended that masonry units should be wrapped and left in pallets to reduce the risk of efflorescence during a construction project.

The following installation issues associated with building surface result in creating efflorescence

• Improper application of through-wall flashing
• Utilization of masonry devoid of adequate ventilation
• Utilization of masonry in areas where a perfect moisture barrier does not exist
• Joint material failure
• Imperfect ground storage

How to get rid of efflorescence - The following measures should be taken to avoid efflorescence:

1) Hydrophobic Sealant: Use a saturating hydrophobic sealant to a building material surface to resist the immersion of water. The sealant also will resist water from passing through a building material.

2) Capillary Breaks: Set up capillary breaks like polyethylene sheeting among a building material and soil to reduce the risk of salt penetrating the material.

3) Standard Masonry Construction: Apply overhanging copings, eaves and flashings will help in reducing the risk of entering water into a wall.

4) Better Emphasis on Landscaping and Sprinklers: Give concentration to landscaping and sprinklers will guarantee to avoid water from reaching permeable building materials.

5) Set up Grout with Mechanical Vibration: Compile grout with mechanical vibration will control the occurring of voids in the grout.

6) Apply Dense Tooled Mortar Joints: Provide dense tooled mortar joints to minimize the permeable nature of a wall, making it strong for salts to pass through it.

7) Utilizing Grout Admixtures: Various grout admixtures like chemical additives should be used since they can make flow of a grout mix better and minimize its water content all together to lessen voids in grout.

8) Preserve Masonry Materials Properly: Retain masonry materials off the ground and wrap them with water-resistance materials to safeguard these materials from groundwater and precipitation.

Article Source: www.nitterhousemasonry.com




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Published By
Rajib Dey
www.constructioncost.co
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Some vital methods for concrete curing

METHODS OF CURING :- Based on the type of construction work, the curing of concrete is done with the use of the following processes :-

1) COVERING: Under this method, wet gunny bags or hessian are utilized to wrap the newly developed concrete surface. This process is very effective for horizontal and vertical surface.

2) PONDING: Under this process, the entire surface is segregated into rectangular or square cages with the development of tiny clay bunds and these cages are filled with water occasionally building small ponds. This process is ideal for curing horizontal surfaces like floor, pavements etc.

3) SUBMERGING IN WATER: Pre-cast concrete members are over and over again cured by submerging them under water.

4) STEAM CURING: With this process, steam under pressure is sprinkled over the concrete surface. This process is very useful for pre-cast members.

5) SPRINKLING: Under this process, the water is sprinkled repeatedly over the concrete surface to keep the surface wet.

6) CURING WITH CHEMICAL: Under this process, water is sprayed over the surface as soon as specific amount of hygroscopic salt like NaCI, CaCletc are added. It helps to engross moisture from the atmosphere.

(7) MEMBRANE CURING: Under this process, concrete surface is wrapped with water proof membrane like wax emulsion, bitumen emulsion etc. The membrane stops the vaporization of water from concrete surface.

Article Source: www.civilnoteppt.com

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Published By

Rajib Dey

www.constructioncost.co

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Benefits and uses of Light Weight Concrete

Usually, the traditional concrete is made of a heavy material containing density about 2400kg/m3 and strong thermal conductivity. If, the ordinary concrete is used for building up the structure, it can increate the dead weight of the structure and as a result the structure turns out to be heavy. The cost of the structure is also increased significantly.

The light weight concrete is defined as the concrete whose density differs from 300 to 1800 kg/m3.The following methods are applied to build up light weight concrete:

1) By cellular construction.
2) By generating huge quantities of air
3) With the use of no fines concrete
4) With the use of light weight aggregates like expanded clay, shale and slate , fly ash, blast furnace slag etc.

Advantage: The light weight concrete is beneficial for the following reasons :-

a) Because of its low density , it can minimize dead load, enhances the advancement of building and reduces the handling cost.
b) The light weight concrete contains low thermal conductivity. Therefore, in severe atmospheric condition, the type of concrete is mostly recommended.
c) When light weight concrete is used, it provides an opening for industrial wastes like fly ash , slag etc, to get rid of the issue for disposal.
d) It has good resistance capacity against fire.
e) The process for slicing , cutting, drilling or nailing becomes easier for light weight product. It can simplify the construction and repair work.

Uses: Given below, various applications of light weight concrete :-

a) It is extensively utilized as insulator to exterior walls of different types of buildings.
b) It is suitable for erecting load bearing walls, filler wall and partition wall.
c) It is effective for producing pre-cast floor and roof panels and composite walls.
d)It can also be applied for building up in situ composite roof and floor slabs.



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Published By
Rajib Dey
www.constructioncost.co
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Waterproofing of Concrete, Walls and Floors

Construction of any building is not easy and it doesn’t end after completing the building; as there are so many other little things that need to look after before making a building.

One of those is waterproofing the building, a building must be guarded from water, heat, heavy sunrays and dust; if any of them is not properly followed during the construction then the building is not safe actually. Waterproofing is done at the time of concrete and sometimes a badly made concrete can’t guard the building from water for the discrimination of water by any admixtures.

A concrete is called waterproof when a dense concrete is made with right amount of total non-porous material and low water ratio; which will create a minimum of air blanks. As all concretes are porous so these holes need to be reduced for making the concrete so far tight to water.

It is sometime good to use a little extreme proportion of fines to make a good concrete; also a little increment in cement content over normal concrete is also beneficial as more cement needs less water for the same amount of work.

This thing need to describe a little more, here some methods is discussed for waterproofing:

a) Concrete and masonry grains are made waterproof with the use of three substitute layers of alum and soap mixtures, at first a hot alum solution is prepared with hot water, applied and worked in with a firm brush after pouring the hot soap mixture. The solutions are used with a gap of about 24 hours between the alternate coats; soap mixtures act like lubricants and also form difficult fillers by response with cement and may be applied while the concrete remains green.

b) When a fully hydrated white lime is added with the following mixtures it gives more proof from water; this mixture acts good as the lime paste absorbs about double the volume of paste when it mixed with equal weight of cement. It is also very effective in faulty filing but the mixture should be of thick concrete; the hydrated lime actually grows ability of work that gives a slight decrease in water content and reduces penetrability. Concrete must be made rich where the excess cement should be 15-20% over sand and 20% excess mortar over rough aggregate; a ratio mixture of 1:1.5:3 with water/cement ratio of about 0.40 will make the concrete really water-proof.

c) After the practicable work, the form-work has to be removed and the concrete exterior should be rubbed smooth and washed. To fill the holes, a mixture of cement and sand in the ratio of 1:1.5 with water-proofing compound is applied over the whole exterior without leaving any material on the concrete face.

d) Work on concrete floors are done at the time of cementing with dry cement which is sprayed over the exterior and worked in with a steel trowel on the first set of the concrete.

e) The method of water-proofing on the surfaces depend on the quality of concrete and the smallest holes can be filled with slit or fine clay, boiled linseed oil, paraffin or varnish then brushed over the exterior after the concrete has dried well. Nearly two or three layers are applied and dried before the next application; one or two layer of coal tar makes the exterior waterproof, concrete must be dry and free of dust and a thin bituminous coat can also be given for more firmness.

f) Generally Bituminous Putties are laid on horizontal exteriors and also mopped on vertical exteriors when they are either hot or cold.

g) Proprietary compounds like Pudlo, Medusa etc. are used as per the instructions of manufacturers. Insert materials which are of the finest particles can be used to dense the concrete especially when the total is in fines.

h) Silicate or soda also works well in water-proofing; whereas the mixture of 1 kg of washing soda and water will make a cement mortar water-proof.

For more information, go through the following construction article theconstructioncivil.org



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Published By
Rajib Dey
www.constructioncost.co
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