Insulated concrete formwork

An overview of insulated concrete formwork used in construction of buildings.

1. Insulated concrete formwork Presented by, SAFA RIZWANULLA SHERIFF DEPARTMENT OF CIVIL ENGINEERING PRESIDENCY UNIVERSITY

2. CONTENTS Introduction Literature review Types of forms Specifications of ICF’s Advantages Disadvantages Applications Conclusion References

3. Introduction Insulating concrete Forms (ICF) System comprises of a panel of two walls of Expandable Polystyrene (EPS) separated by a nominal distance of 150mm by hard plastic ties . These are assembled on site to hold reinforced concrete. Upper and lower surfaces of the polystyrene panels are castellated and the vertical mating surfaces are tongue-and-groove to form a tight fit when joined together. The forms are open ended hollow polystyrene blocks which fit tightly together to form a shuttering system. Concrete poured into the hollow space to form a continuous wall. This wall supports the structural loads from floors and roofs, and the shuttering provides thermal insulation .

4. INSULATED CONCRETE FORMWORK

5. Literature review [ 1] Andreea-TereziaMircea (2010) carried his research on ICF wall with different parameters. The three various thickness of shear wall was casted and tested for cyclic loading to find the seismic performance. It was concluded that, ICF wall provides, energy efficient green building, high durable, increased strength, maximizes resistance to natural disasters and minimizes temperature fluctuations by absorbing and storing heat.  [2] AfshinHatami (2011) studied the challenges in ICF system like high initial cost and difficulties of pouring concrete at higher elevation. Final remarks made was, usages of flowable concrete (SCC) for walls upto 8ft height will reduce pouring difficulties and reduce construction time.

6. Literature review   [ 3]Peter Dusicka (2010) studied the behavior of ICF wall under seismic loading. 4ft ,12ft ICF wall and conventional wall are casted and tested under cyclic loading. It was concluded that, ICF grid wall system potential exists for the seismically active regions  [4]W. Maref , M.M Amstrong and G. Ganapathy (2012) monitored two IFC wall specimen. ICF walls have the potential to reduce the peak heating requirement of the furnace, and the peak cooling requirement of the air conditioning system. This may have implications for the sizing and cost of mechanical equipment.  [5]Abdullah yildiz and GokhanGurlek (2008) presented a study on environmental analysis of thermal insulation in buildings with different thickness. The result of this paper was increase of thermal insulation decreases the heat loss in the building with increase in the cost of insulation material.

7. Types of forms Standard Forms – These form bulk of the forms and have 50mm EPS panels on both sides with 8 hard plastic ties holding the panels. Dimensions of these forms are 1000 x 250 x 250mm. (See Fig. 2) Lintel Forms – In combination with Half Height forms, these form the top layer of all wall gaps and hold the concrete thus preventing thermal leaks. Dimensions of these forms are 1000 x 125 x 250mm. (See Fig. 3) Half Height Forms – Together with the lintel, these form the top layer of all gaps in the wall and hold the required steel reinforcement. Dimensions of these forms are 1000 x 150 x 250mm. (See Fig. 4)

8. Types of forms Floor Edge Forms – These form the top most layer, where the wall ends and floor begins. This envelopes the floor slab and thus prevents thermal bridging. Dimensions of these forms are 1000 x 375/125 x 250mm. (See Fig. 5) Corner Forms – These constitute 90º corner of the building. The two sides are 50mm EPS panels held together with 8 hard ties. Dimensions of these forms are 750/500 x 250 x 250mm. (See Fig. 6) End Forms – These create wall ending by fitting in inside the Standard or Corner form and provide a smooth and thermal bridge ending to the wall. Dimensions of these forms are 150 x 125 x 50mm. (See Fig. 7)

9. Specifications of ICFs ( i ) Expanded Polystyrene (EPS): Self-extinguishing type EPS shall conform to IS 4671: 1984 having density not less than 25 kg/m3 and valid Restriction of Hazardous Substance (ROHS) test certification. (ii) Polyurethane (PU): Foam Adhesive Shall have Skin Formation of 8 min, Density 25 kg/m³, Sound insulation 58 dB, Insulation factor 35 mW / mK , Shrinkage< 2 %, Insulation factor 35 mW / m.K and Water absorption of 1 % volume. (iii) Plasticizer: Slump retaining super plasticizer for self-compacting plastic concrete shall conform to IS 9103:1999. (iv) Hard Plastic Tie: Shall be made with HDPE (High density polyethylene) (v) Cast-in-place concrete: The ingredients, grade of concrete & slump for walls, floors and roofs shall be used as per IS 456:2000.

10. Advantages 1. Insulation: ICFs provide very good insulation. The R-value (a measure of effectiveness as an insulator) of ICFs is typically rated R-18 to R-35, depending on the thickness of the wall. In comparison, traditional brick walls are usually rated R-10 to R-12. 2. Thermal Mass Effect : The mass of the concrete core of ICFs adds significantly to the thermal efficiency of the structure. The concrete acts as an energy reservoir and EPS sheet act as a energy barrier reducing temperature changes from day to night. 3. Energy Efficiency: Homes built with ICFs typically require less energy to heat and cool than typical wood framed homes . 4 . Sound Proofing: Concrete is a material that tends to reflect noise, while foam insulation absorbs sound. The combination of foam and concrete creates a thick wall that serves as an excellent sound barrier.

11. A dvantages 5. Disaster Resistance: ICF walls provide good resistance to storms, strong winds and seismic effects. According to tests performed at Texas Tech University, ICF walls were less likely to suffer damage in high winds than conventional houses .. 6. Less Maintenance : ICFs are resistant to rot and termite infestation, problems that is common in wood homes and costly to repair. 7 . Simplicity: ICF homes combine framing, installation of insulation, and sheathing into one step. An experienced contractor can construct an ICF home in less time than it would take to construct a wood conventional brick house, thus creating labor cost savings. 8. Flexibility: ICFs can be used with most conventional finishes or designs. Moreover, ICFs can easily be cut with a saw, so curves and odd angles are usually not a problem.  

12. D isadvantages Cost One major disadvantage to insulated concrete forms is the cost. You should expect to pay 5 to 10 percent more in construction costs than you would for a traditional wood-frame house. Difficult Remodeling Another problem with ICF homes is that they are difficult to remodel. We must think carefully about the design and anticipate changes that we might want to make in the future. It is also important to account for all of the electrical and plumbing chases that are required, because adding them after construction may require cutting into concrete.

13. D isadvantages Takes up Floor Space ICF walls consist of several inches of rigid foam insulation and reinforced concrete, which means they take up more space than traditional wood frame walls. Insect and Water Problems If polystyrene forms are used for ICF construction, that exterior foam insulation may actually provide a route for insects and groundwater to enter the walls. To address this problem, we can choose foam blocks that are treated with an insecticide and designed to be waterproof. However, these blocks are usually more costly than untreated options, which may drive construction costs a bit higher. Humidity Immediately following construction, an ICF home may experience problems with humidity. The rise in interior humidity occurs because the concrete is still in the process of curing. Once it is fully cured, the air's moisture level should return to normal.

14. Case study It was selected for the building of cottage to Passive house standards in an Area of Outstanding Natural Beauty with additional planning development restrictions in West Sussex. The Curly House a home designed and build to minimise energy consumption and carbon footprint. It is designedto be an affordable and very low energy building on a highly exposed site that is subjected to bitingly cold winters and very hot summers. ICF (insulated concrete formwork) for the walls and OP-Deck (thermally broken super insulated deck system) for the floors and roof. ICFs are highly suited for ease of build for both complex and curved structures, and the same system can be used for below and above grade walls.

15. Case study In total, 340m3of concrete was required to complete the project. The Op-Deck was specified to take a load of 5kN/m 2 . The heavier construction option was chosen to provide thermal mass in order to balance the heating gains and losses due to the large areas of glazing. The insulating element of ICF acts as a buffer to the thermal mass allowing the slow release of heat into the building to ensure a constant internal temperature throughout the year. The semi subterranean nature of the design also meant that materials susceptible to damp could not be considered, so no timber was used in the construction of the building envelope.

16. Applications Floors and Foundations ICF walls are conventionally placed on a  monolithic slab  with embedded rebar  dowels  connecting the walls to the foundation. ICF decking is becoming an increasingly popular addition to general ICF wall construction . ICF decking weighs up to 40% less than standard concrete flooring and provides superior insulation . ICF decking can also be designed in conjunction with ICF walls to form a continuous monolithic structure joined together by rebar.

17. Applications Walls ICF walls are constructed one row at a time, usually starting at the corners and working toward the middle of the walls . End blocks are then cut to fit so as to waste the least material possible. Interior and exterior finishes and facades are affixed directly to the ICF surface or tie ends, depending on the type of ICF.

18. Applications Plumbing and Electrical Plumbing and electrical conduit  can be placed inside the forms and poured into place, though settling problems could cause pipes to break, creating costly repairs. A hot knife or electric chainsaw is commonly used to create openings in the foam to lay piping and cabling . Electrical cables are inserted into the ICF using a Cable Punch.

19. C onclusion Concrete specimen with EPS sheets exhibit, no cracking or zero disintegration of EPS sheets even after complete failure of concrete core When compared to normal plain concrete and ICF model there is no much change in the load carrying capacity, but after attaining peak load sudden failure occur in the plain concrete but ICF shows ductile failure. Curing process is not required, since the concrete is covered by EPS sheets. Due to the ductile behaviour its use may protect the structure from natural disasters like earthquake. From the analytical and experimental investigation it concluded that thickness of 75mm EPS sheet with concrete core gives maximum strength & ductility.

20. REFERENCES [ 1] Andreea-TereziaMircea and RuxandraCrutescu (2010), Research Contributions to the Seismic Performance of ICF Technology Wall Systems, WSEAS Transactions on Information Science and Applications, pp 1240-1250 . [2] AfshinHatami and George Morcous (2011), Job-Built Insulated Concrete Forms (ICF) for Building Construction, 47th ASC Annual International Conference Proceedings. [3]Peter Dusicka , Thomas Kay, Carl Werner and Max Stephens (2010), Seismic Evaluation of Green Building Structural System: ICF Grid Walls, IStar Laboratory infrastructure Testing and Applied Research . [4]W . Maref , M. M. Armstrong, H. Saber, M. Rousseau, G. Ganapathy , M. Nicholls and M.C. Swinton, (2012), “Field Energy Performance of an Insulating Concrete Form (ICF) Wall”, National Research Council, Canada . [5]Abdullah Yildiz , GolahanGurlek , Mehmet Erkek , (2008), “Economic and environmental analysis of thermal insulation thickness in buildings”, Journal of thermal science and technology, Turkey.

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