Kuldeep Singh - Answers
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Why are fly ash bricks not used so frequently as compared to red bricks?
Kuldeep Singh
There is no doubt that in comparison with red bricks, fly ash bricks are structurally stronger, more durable, better insulators, water-resistant, etc. But not using them so usually has, especially in India, a whole lot of reasons : Firstly, though fly ash bricks save the cost of the project as a whoRead more
There is no doubt that in comparison with red bricks, fly ash bricks are structurally stronger, more durable, better insulators, water-resistant, etc. But not using them so usually has, especially in India, a whole lot of reasons :
Firstly, though fly ash bricks save the cost of the project as a whole, they are still more expensive than red bricks, and the poor majority doesn’t like the idea. Secondly, flay ash bricks are not easily available everywhere, and red bricks are. Getting fly ash bricks transported adds to their cost, which already was higher.
Thirdly, only modular sizes are feasible. Larger bricks are very brittle. The outer surface is harder as compared to the inner core, which can lead to cracking in the future if a few bricks are cut out to allow running of pipes, wiring, etc.
Fourthly, laborers aren’t very familiar here with fly ash. Many builders, therefore, consider it a bad choice.
Fifthly, fly ash bricks buildings get quite cold in winter since it doesn’t absorb much heat.
Sixthly, fly ash bricks are only good if care for quality in production has been taken.
Seventhly, they require cement to be produced, increasing the demand for cement. Cement production, in turn, is not environment-friendly.
Lastly, fly ash is a health hazard. It has got substances that can reach in and stick in your lungs, causing long term damage. Crystalline silica, a component in fly ash, is a known carcinogen.
See lessWhat are the functions of Arches and Lintels?
Kuldeep Singh
It depends a bit on what you mean by arches and lintels. In truth, they both are very different, but often arches are used for the same purpose as lintels. Arches are curved structures fixed joined to either the ground or another structural member. They only carry compressive forces; however, they mRead more
It depends a bit on what you mean by arches and lintels. In truth, they both are very different, but often arches are used for the same purpose as lintels.
Arches are curved structures fixed joined to either the ground or another structural member. They only carry compressive forces; however, they may be loaded because of their shape and orientation. Their first use actually dates back to the Roman Empire times. Back then, they didn’t know how to handle tensile loads. So they came up with this brilliant thing called an arch that converts all loads to compressive loads against which stones etc. were fairly good.
Lintels are a type of structural member placed like a beam just above an opening (door, window, ventilator) so as to carry the load of the wall above the opening.
Now, coming back to your question, arches are also often used for the same purpose as lintels. But I think for that, lintels are a better option because :
But, arches could have their own advantages :
In which type of soil ‘Floating foundation’ can be used?
Kuldeep Singh
When the soil strata is so soft that even pile friction is not enough for handling the load generally for tall buildings. When there is a presence of expansive soils from the surface down to a considerable depth. Like the depth of the floating foundation itself. Other cases when there is a good sheaRead more
Which is best material for G+12 building, RCC or Composite of RCC & Steel?
Kuldeep Singh
Short answer : Composite. Composite structures are generally preferred for buildings with at least ten floors when looked upon from a cost point of view. But just generalizing this would be too vague. A lot should depend on the particular project at hand. Though, composite wins hands down in terms oRead more
Short answer : Composite. Composite structures are generally preferred for buildings with at least ten floors when looked upon from a cost point of view. But just generalizing this would be too vague. A lot should depend on the particular project at hand. Though, composite wins hands down in terms of project completion time.
Long answer : You can do a short analysis yourself. Since a slight difference in cost can also be an important factor, one can do some calculations by first modeling the building in ETABS or SAP. Then, you can calculate the quantity of materials needed for both approaches. You can multiply by the rates to get your material cost. Usually, composite beams and slabs are cut cheaper than RCC, and the columns are at par in both the methods. Then, you can use project time calculation software and henceforth deduce labor, machinery, electricity costs, etc. Also, composite buildings save both time and material on foundations. You can add up to find out simple total costs. If the difference is huge, you need not care about miscellaneous costs generalizing them to come within the difference, and you have your cheaper method.
I once read that for a simple B+G+20 tower, the composite method must take only 45% the time and around 80% of the materials as compared to the RCC method. The paper had carried out an exhaustive cost analysis, as mentioned above.
See lessCan Infrared thermography be used to inspect cracks in a building?
Kuldeep Singh
Yes, absolutely. In fact, not just cracks, infrared thermography can also detect surface defects, changes in density and porosity, delamination, and concrete reinforcement corrosion in addition to cracks. It is done actively as well as passively. In the active approach, an inmate temperature differeRead more
Yes, absolutely. In fact, not just cracks, infrared thermography can also detect surface defects, changes in density and porosity, delamination, and concrete reinforcement corrosion in addition to cracks.
It is done actively as well as passively. In the active approach, an inmate temperature difference in the defects and it’s surrounding is detected by sensors. In the passive way, energy as light is exposed to the surface, and then infrared cameras read out any abnormality in the release of that energy from various directions. For cracks in concrete passive inspection is usually done.
The surface cracks are generally spotted within a second, but it may take a few minutes to reach the deep cracks.
See lessWhat is Contour Farming?In which type of soil contour farming is suitable?
Kuldeep Singh
Contour farming is an agricultural practice where steps are cut out on a sloped field so as to provide steps of flat land (same contour) for cultivation. The potential benefits are a check on erosion, better rainfall usage, more infiltration, and reduction in the need for irrigation. It is feasibleRead more
Contour farming is an agricultural practice where steps are cut out on a sloped field so as to provide steps of flat land (same contour) for cultivation. The potential benefits are a check on erosion, better rainfall usage, more infiltration, and reduction in the need for irrigation.
It is feasible on all slopy regions to accept on those with highly erodible soils and soils that allow little infiltration.
See lessWhen is scarification needed for road work?
Kuldeep Singh
I assume you are talking about flexible (asphalt) pavements. Sacrification is needed when the cuts, potholes and all deformations are such that : The optimum moisture content required for proper binding can no longer be met. The filler material won't bend properly if just put judging by the conditioRead more
I assume you are talking about flexible (asphalt) pavements. Sacrification is needed when the cuts, potholes and all deformations are such that :
The entire bituminous layer until the depth of the craters is scraped off, and a new layer with fresh material is then applied to reconstruct the road.
See lessForm work stripping time Vs Compressive strength of Concrete
Kuldeep Singh
Hello there Me. Chamarhy! I read the complete thread and I understand that you haven't exactly got the answer you are looking for. Well, that's partly because you are slightly misinterpreting cl. 11.3 of IS 456 (2000). It says that formwork must not be removed until concrete gains at least twice theRead more
Hello there Me. Chamarhy! I read the complete thread and I understand that you haven’t exactly got the answer you are looking for. Well, that’s partly because you are slightly misinterpreting cl. 11.3 of IS 456 (2000). It says that formwork must not be removed until concrete gains at least twice the strength it needs to stand the stresses it will experience during formwork removal. Now, if you look carefully, this doesn’t mean that the code has given this advice with concrete’s final compressive strength in view. It is solely there for the safety of the structural member during formwork removal.
The table within that clause, says that for ordinary conditions (OPC is used, ambient temperatures >= 15°C, adequate curing is done), these stripping times for the concrete to reach that above mentioned strength will be so and so for so and so types of formwork. It is not talking about the compressive strength of concrete.
Apparently there is indeed no specific mathematical relationship between the formwork stripping time and the final (28 days) compressive strength. This guideline is solely for the protection of concrete during formwork removal. Obviously concrete gains strength the better the better it’s cured. So, if someone wishes to strip early and begin curing early, the code is trying to advice against it. Furthermore, concrete indeed attains strength in direct proportionality with the quality control in production, the quality of the materials and the adequacy of curing. As far as I think, there could be only a little implication that concrete gains strength well if it retains heat in very early age and formwork does insulate the concrete. But that’s not much important because you can’t wail too long to strip formwork so that you can start curing when it’s the right time.
Now, the next point is the theoretical or experimental evidence that you are seeking. I’d like to humbly tell you that the table in 11.3 which claims that these are the times for achieving double the strength requirement for formwork stripping must indeed be based on experimental data. It is easy to model the stresses induced at the time of stripping. Now, the strength of concrete within formwork can also be estimated via pull out test and a few non destructive tests. You can Google ‘concrete strength tests during maturity period’ and it’ll pop up with a number of papers and articles. The pull out test for instance, corellates the compressive strength to the force required to pull out a core of specific shape and size, in a specific way from the maturing concrete.
To conclude, the code is not talking about a relationship between removal time and the compressive strength. It’s only talking about the corelation between removal time and the strength at that very time of formwork removal, for which, experimental evidence has long been found.
Sorry for a long explanation. But, I’ll be more than pleased if it clears your doubt. Thank you!
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