as by research and experience we can say that clay bricks are good than the concrete blocks in respect of porosity....

Girish s, Deshmukh

M.E. Structure

Govt. Engg. College Aurangabad

Mr. Girish Deshmukh

Sir,

When we reduce the porosity of concrete blocks by using better machinary i.e having vibrators & more pressure like Columbia block making machine. Also if flyash is used which is a waste product & environmental friendly if we use it in blocks.

That is can we make dense blocks to reduce porosity thus the possibilty of leakage

Regards

Sandeep Hirani

Shamik Enterprises Pvt Ltd

Well your email does not indicate the leakage problem clearly. If you are using concrete blocks for works below ground such as basement and water is entering into the building then you can use some water proofing system ranging from simple clay to expansive membranes depending upon your budget. If there is problem of rain then brick is certainly better than concrete porous blocks. Most of brick buildings in UK are using cavitywall construction. Major purpose of external wall is to keep water away from the building.

I hope this may be a little help.

In the US housing industry, virtually all cases where concrete block is used below grade (below ground level) the walls are coated with a tarry substance to act as a barrier against water penetration.

dear sir

please give the details of coating given to concrete block below ground level.

pkmohapatra

Hi Sandeep,

Do you make your own Blocks?. "Siporex" Pune are pioneers in making such Blocks. If use thier Blocks and do good quality plastering then leakage problem can be avoided. In Mumbai due to heavy rains during monsoon this is common problem as builders try to finish the job faster. Also exterior good quality paint mfd. by "Asian Paints" or "Snowcem" can avoid such leakages.

Suresh Sharma.

All cementiferous materials are in reality small granules held together with cement, plaster or similar and they are all porous to a greater or lesser extent. The porosity can decrease with smaller particle size and thickness however water in molecular form can move through them. Water will pass through many substances in this way (semi-permeable membranes) many paints and plastics will allow this and the search goes on in the packaging industry to find non permeable films and coating to give the most cost effective answer. Film thickness plays a role. The most cost effective coating is bituminous (tar) and in some cases plastic barriers are used in place of or in addition to.

Bricks or concrete you are going to need to seal the surface with such a product. There are many on the market.

I am not Civil Engineer but have build many block walls and if there is water behind they will leak unless the water is allowed to drain without or with minimum contact with the wall. Even a block wall with the holes filled with loose concrete tend to leak. Solution is to add a barrier and good drainage at footing to take the water away. This even applies to poured walls however leakes in poured walls can be injected for excellent results. Bottom line is let the water drain away from the wall as best you can.

Dear Sandip,

The leakage is due to porosity of concrete blocks, moreover the conventional red burnt bricks absorb water thus preventing its ingress. So in my opinion for a place like Mumbai or any in Konkan region it would be better if you go in for Red burnt bricks instead of Concrete blocks.

regards,

V. A. Patil

Concrete or brick - they are both porous to a greater or lesser extent.

In India why not try the old UK farmer finish of Cow Dung and lime. They react together to form calcium proteinate but will still peobably be porous. Bitumin is the best answer - as long as you are happy with black.

If you are fluent in English, this summary of the various current materials and techniques will be of interest to you:
http://www.concretenetwork.com/concrete/waterproofing_concrete_foundations/

IF you are in need of fully insulated walls for energy efficiency in a building located where heating or cooling will be used during most of the year, you may also look at alternative construction using ICF's or 3D-Panels. These systems use solid insulation foam as a part of the wall construction, with high-strength concrete that is nearly water impermeable due to additives and density.

ICF's come in various sizes by manufacturer, but are generally a system of hollow styrofoam blocks that you "stack" one layer at a time, and insert or lay-in steel reinforcing. When finished, you call the concrete supplier who pumps high-strength/density concrete into the hollow cavity of the walls, filling it up. The result is highly efficient, sound-proof, pest-proof, and nearly impenetrable by water. Most types of exterior and interior finish materials can be anchored with screws directly into the rigid plastic ribs that are part of the blocks.
You should have access to several producers of such as system, such as these:
amvicsystem.com
tfinsulatedconcreteforms.com

3D-Panels are a specialized product from one of a few fabricators with rights to make them (process is still under patent, but licensed around the world). The fabricator closest to us here in the midwest USA is more oriented toward industrial applications and is PMR, who you can research here: pmri95.com/id2.html.
This is approximately the "inverse" of the above ICF system, with some advantages. A rigid foam panel is fed through a custom machine so that the finished panel has large-gage structural-wire welded in a truss reinforced manner at the appropriate angle through the foam. The result is a strong structural panel typically 4 feet wide by a selected height for the final wall. Here is a pic I found of the process: pmri95.com/id8.html

These are assembled vertically by placing them on top of the rebar standing up from foundation/slab edge, and then a gunnite/shotcrete team "sprays" between 2-inches and 4-inches (5-10cm) or so of high-strength concrete into the wire mesh, with a following worker working a trowel for final appearance. Flyash can be added for cost savings so long as the other additives are appropriate for the mix. The building goes up faster than you can imagine, and the roof structure can be dropped onto it almost immediately. When cured, it can be directly painted - no need to install bricks or exterior panels, it is a structural 'stucco' finish. Where below grade, a tar or tar-based roll product is applied on the exterior side. Where above grade, a concrete sealant primer goes on first, followed by any exterior grade paint or finish like stucco.
After plumbing piping (typically pex tubing) and electrical cabling or flex-tubing conduit with backboxes are installed into the wire mesh, the interior side is also sprayed similarly with shotcrete. The final finish can be customized for final appearance by rolling, smoothing, or as desired, and NO further materials like drywall need to be installed, saving costs.
Where below grade, a latex concrete sealant is first painted on the interior concrete once cured, prior to the finish paint.
Try to find one of these locally:
xypex.com/products/products.php
seal-krete.com/heavyduty.htm
penetron.com/en/index.php
ThoroSeal Foundation: thoroproducts.com/pdf_info/INF_FOUN_3.06.pdf

The result is completely airtight, energy efficient, soundproof, hurricane-rated, seismic rated, pest proof, water proof (assuming the bottom edge joint between walls and floor remains intact), and is already finished with a customizable stucco appearance inside and out with no need for further materials.