You may have read in various articles and/or our website that ICF buildings have concrete walls and are therefore very strong. However, now in India, most buildings have concrete frame structure and hence there is confusion regarding comparisons derived from USA & Canada, where comparative analysis is done with wood frame buildings. However, such comparisons may not be valid in the Indian context - that ICF structures and concrete frame buildings are equally strong in disaster conditions. It is my endeavor to explain why this is not so.
ICF structures are much stronger and practically disaster proof when compared to concrete frame structures. The arguments are based on three premises:
1. ICF monolithic wall / roof structural arrangement is stronger
2. The wall concrete inside the stay in place, insulated formwork is stronger
3. Insulated ICF Concrete walls are thermal stress free, crack free; hence stronger
ICF monolithic wall / roof structural arrangement is stronger
From a disaster-resistance perspective, roofs, walls and floors should not be thought of separately, but as integral parts of a box. These should be securely connected in such a way that the entire structure behaves monolithically during natural disaster when lateral forces act on the walls. (Earthquake, Cyclones and tornadoes all cause damages by exerting severe lateral forces of varying degrees on the foundations and walls). In the conventional frame structures (image above, right. Tree for comparison), individual columns and beams face the brunt of such lateral forces and hence fail individually. In contrast, the monolithic box (above, left) structure is designed as a 3D box with tightly connected reinforced concrete floors, roofs and walls. These components act in tandem and are able to face much larger lateral forces without any failure.
Concrete within the stay in place, insulated formwork is stronger
Two beneficial aspects of curing and consequently, higher strength of the concrete poured inside the Insulated Concrete Formwork emerge:
1. 70% strength levels can be reached sooner when concrete cures at higher temperatures. During the concrete pour, the heat of hydration due to reaction of cement with water is generated and retained within the insulated formwork. This results in the higher temperatures and hence, early strength gain of the concrete.
2. 125% of design concrete strength can be achieved on 180 days moist curing. As the formwork in ICF is “Left in Place” after the concrete pour, it provides protection against moisture loss from the formed concrete surface and this continuous moist curing ensures at least 125% of the designed concrete strength.
You can read more about how to strengthen concrete in the PCA (USA) reference article “The Role of Concrete Curing” by Dr. Jerzy Z. Zemaztis.
Alternatively, one could peruse other authoritative references on the internet to arrive at the same aspects. These might include the Mahacement page on concrete curing.
Air-tight Thermal insulation on both sides of ICF walls keeps it uniformly strong
Concrete being a high mass building material is high on specific heat and hence it takes a lot of thermal energy to raise its temperature. Due to seamless thermal bridge free insulation on both sides, this high heat is not forthcoming and hence the concrete inside is free of any thermal stress caused by diurnal heating and cooling cycle. Thermal stress generated crack is the main reason why the Indian Building Codes provides for minimum quantities of steel for concrete even in 3-4 storied buildings. With thermal stress-free concrete inside ICF, we need to research the steel requirement in low rise buildings as the rebar quantity is greatly reduced in ICF walls.
This blog is the first in our series of posts explaining our tagline "Greener, Safer, Stronger, Faster!" in terms of our flagship product, the Insulated Concrete Formwork. To learn more about this revolutionary construction system, please visit the product page for ICF.
Our aim is not just to market our product, but to disseminate information and educate construction professionals as well as the general public on the benefits of insulation, and new, sustainable construction systems. Please feel free to contact us for any queries or for more information (firstname.lastname@example.org , +919818058899)