Questions submitted for the 2010 EPD Competition
Q: What is the ACI definition of "stirrup" that will be used in judging?
A: Per Rule 2b, a stirrup is reinforcement typically bent into a u-shape or box-shape and placed perpendicular to or at an angle to the longitudinal reinforcement, causing it to be used as shear reinforcement running in the transverse direction to the cross section of the EPD. Numerous configurations would be possible.
Q: Is the use of braided reinforcements permitted?
A: Braiding of longitudinal bars is allowed per the current rules; however, the stirrups shall not be braided, as that is considered a form of bundling, which is not allowed per Rule 2b.
Q: It states that no more than 15 stirrups may be used in the EPD. Does this mean that there can only be 15 stirrups total including those used in the columns of the EPD?
A: Yes, per Rule 2b, stirrups are transverse reinforcement, which would include reinforcement placed in the transverse direction in the columns (legs) and no more than 15 total stirrups are allowed.
Q: Would a spiral reinforcement setup for the columns be acceptable?
A: Yes, spiral stirrup reinforcement is permitted. Each full 360-degree turn (or step) is considered one stirrup. For example, if in one leg of the EPD a team has five steps of spiral stirrup reinforcement, 10 stirrups would be left for the rest of the EPD.
Q: Do the reinforcements need to be on a major axis? Can it be curved or skewed?
A: Reinforcements are classified as longitudinal and stirrups (transverse) per Rule 2b. Many different reinforcement arrangements are possible so an exact answer can't be given; however, reinforcement arrangement, which contains curved or skewed reinforcement, are possible. When determining the classification of a particular pile of reinforcement (longitudinal versus stirrup), the judges will consider what function that piece of reinforcement is primarily servicing (that is, flexural resistance, shear resistance, and so on.).
Q: Does the concrete have to have aggregate material or is cement paste sufficient? Additionally, if aggregate is required, is coarse aggregate required or will fine aggregate suffice?
A: Aggregates are not required to be used. Rule 2d covers the aggregate permitted to be used; either fine and/or coarse (up to 3/8" size) aggregate may be used.
Q:

Can we use the figure above for the stirrups of the beam?
A: It appears that you are planning on your stirrup configuration to be a closed stirrup with two crossties, which would be acceptable. However, keep in mind that the method to connect the various pieces of reinforcement making up the stirrup (main stirrup and two crossties) is limited by Rule 2b.
Q: May we use Brazilian cement?
A: Per Rule 2a, the cementitious binder shall meet the ASTM standards listed. It is certainly possible that the Brazilian cement you are planning to use will meet these requirements (a lot of international cements do); however, you should obtain a letter from your cement supplier verifying this.
Q:

Can the loop configuration adopted for the anchoring of the reinforcement longitudinal beam be used?
A: It appears that you are planning to provide a hooked end to your longitudinal reinforcement, which would be acceptable.
Q: May we use other forms of mesh? The rules state the restrictions of wire mesh but not a plastic- or carbon-based material.
A: Mesh is not permitted. "Wire mesh" does not imply what the material is (that is, steel versus fiber reinforced polymer). Also note, the mesh would likely violate the maximum amount of reinforcement for both stirrups and longitudinal reinforcement, as well as the maximum diameter.
Q: How many specimens may we enter in the competition?
A: Per Rule 1f, each school may enter up to two items. Each team submits one EPD for testing.
Q: Does the eight bar/wire limit apply to the maximum amount that can run perpendicular to the plane of the cross section provided in the rules (in and out of the cage)? Can you explain the difference between the direction of the stirrups and longitudinal reinforcement?
A: As indicated in Rule 2b, the eight bar/wire limit applies to the longitudinal reinforcement that generally runs parallel to the length of the member—that is, the length of a beam or the height of a column—but this does not necessarily mean that they are exactly parallel (for example, draped reinforced in a beam). The stirrups are generally normally oriented or at an acute angle to the longitudinal reinforcement and are generally perpendicular to the length of the section but may not be exactly perpendicular (for example, inclined stirrups in a beam). As many different configurations of reinforcement are possible, it is impossible to describe every scenario. However, ACI does define these terms on their Web site under "ACI Concrete Terminology." Please follow the link below to download a PDF version of this document. http://www.concrete.org/Technical/CCT/FlashHelp/ACI_Terminology.htm
Q: Since the rules state that "fibers are not permitted" and that "any type of aggregate may be used," does this mean that aggregates cannot be composed of fibrous materials such as wood or bamboo? Can you explain exactly what "fiber" means?
A: As previously mentioned, ACI defines the term "fiber" in the "ACI Concrete Terminology" section on their Web site. Fibers that may be desirable to use as reinforcement (part of ACI's definition) are not allowed in the EPD. Note that ACI's definition of aggregates indicates that they are granular materials; granular materials are not long and slender like fibers. Fibrous aggregates such as wood or bamboo that will pass through the specified sieve size and that do not meet the definition of fibers—that is, slender and elongated, generally with lengths of more than 100 times their diameter—are acceptable. Teams that attempt to use fibrous aggregates must not allow the aggregates to fibrillate—that is, break down from a granular material and form fibers—at any time. The aggregates also must not be considered a flat plate type of embedment per Rule 2c.
Q: If an air frame has two legs, one at each side of the frame, can we only use four longitudinal bars on each leg or could each leg have eight longitudinal bars?
A: Rule 2b refers to the whole cross section of that portion of the EPD (that is, cutting a plane through both legs in this case). A maximum of eight longitudinal bars may be used per side in the plane cut through the whole specimen. If a team has two legs on a side and desires equal reinforcement in each leg, they would have a maximum of four longitudinal bars in each leg at any given point within the legs.

PLEASE NOTE: The following questions originated from previous competitions. Some questions/answers may not comply with current rules. Be sure to follow the rules for the 2010 EPD competition.
Q: Does the base plate under the EPD specimen always consist of the following materials in the respective order: 1) 13 mm steel plate; 2) 16 mm plywood; 3) 20 mm plywood; and 4) carpeting?
A: No, the base plate under the EPD specimen can vary depending on the differences in testing sites each year. In most cases, the EPD specimen sets on a base plate of various layers consisting of the following materials in the respective order: 1) 1/2 in. steel plate; 2) 3/4 in. plywood; 3) 3/4 in. plywood; 4) 4 MIL plastic sheet; 5) 3/4 in. plywood; 6) 4 MIL plastic sheet; and 7) carpeting or other finish floor surface. However, the ACI Student Activities Committee E 801 reserves the right to change or modify the testing device, including the base plate under the EPD specimen, in any manner it believes is necessary to conduct the EPD Competition in a fair, safe, and timely manner. Reference: Click here to See Egg Protection Device Diagram. (Item #4)
Q: I have a doubt in relation to the diameter and number of bars/wires to be used. The rule says: All reinforcement, longitudinal and stirrups, is not to be greater than 1.6 mm diameter (approx. 16 gages). Longitudinal reinforcement should be limited to 8 bars/wires in a cross section. My question is: If I use bars with lesser diameter than 1.6 mm, will I be able to place more than 8 bars?
A: No, the longitudinal reinforcement should be limited to 8 bars/wires in a cross section as clearly stated in Section 2B of the rules. There are no exceptions stated in the rules allowing for more than 8 longitudinal bars/wires in a cross section if the same bars are less than 1.6 mm diameter. All reinforcement, longitudinal and stirrups, should be used as stated in the rules regardless of whether the reinforcement bars/wires are less than 1.6 mm diameter. Reference: See Section 2B.
Q: Can we use 4 columns to protect the egg?
A: Yes, any design is acceptable including an EPD with 4 columns or supporting legs as long as it is in compliance with all the specified requirements, particularly the Specimen and Testing Configuration requirements listed in Section 4, as clearly stated in the rules.
Reference: See Section 4.
Q: In the Rules Section 4, the specimen and testing configuration (Section E) states that maximum mass allowed is 3500 g. Is this the total weight of the EPD after 28 days curing?
A: The required maximum mass of 3500 g is the maximum allowable mass that the EPD can be when every EPD entry is individually weighed and checked for size and clearances during the Qualification Test procedures at the EPD competition as clearly outlined in Section 5A. Reference: See Section 5A.
Q: Is using spirals permitted? If so, what will be the step of the spiral?
A: What do you mean by the use of spirals and the step of the spiral? If you mean the use of stirrups and the spacing of the stirrups, it is clearly stated in the rules that stirrups are allowed. It also clearly states that the minimum allowed step or spacing of stirrups is 25 mm. Reinforcement in compliance with Section 2B may be used. There is nothing in the rules prohibiting the reinforcement, longitudinal and stirrups, from having a spiral to them as long as there is no bundling, braiding, twisting together, wrapping, or weaving of the reinforcement. Reference: See Section 2B.
Q: Are we permitted to use the longitude reinforcing as shown in the following figure?

A: No, the reinforcing as shown in this figure would not be permitted as longitudinal reinforcement. By definition, a longitudinal bar is any bar (typically straight) placed in the long direction of the member. The bar as shown in this figure is clearly a continuously coiled bar or a spiral causing the majority of the bar to be placed in the short direction of the member. Also, the spirals appear to be spaced closer than the minimum allowed spacing of 25 mm as required in Section 2B for stirrups. If the reinforcing in this figure is not greater than 1.6 mm diameter and the minimum spacing of the stirrups is 25 mm as required in Section 2B, there should be at least 16 bar diameters of space between the spirals (15.625 bar diameters x 1.6 mm-diameter bars = 25 mm). It is very clear in the picture that 16 bar diameters would not fit in the longitudinal space between the spirals. Therefore, the reinforcement shown in this figure would not be allowed because it is not in compliance with Section 2B for either longitudinal bars and/or stirrups.
Q: What will be the height of the egg up to its top?
A: If you proportionally scale the diagram provided in the rules, the height of a large egg as it sets in the eggcup would be approximately between 75 and 100 mm. However, there is no guarantee how big the large eggs will be. ACI will provide them for the EPD competition. Reference: See Egg Protection Device Diagram.
Q: Are we permitted to use the stirrups with a pin as shown in the following figures?
A: Yes, the use of stirrups with a pin as shown in these figures appears to be in compliance with Section 2B of the rules. There is nothing in the rules prohibiting the use of stirrups with a pin as long as all reinforcement, longitudinal and stirrups, is not greater than 1.6 mm diameter; there is no bundling, braiding, twisting together, wrapping, or weaving of the reinforcement; and the minimum allowed spacing of the stirrup is 25 mm. It is clearly noted that the stirrups in these figures have been enlarged for clarity and therefore may appear to be greater than 1.6 mm diameter when in fact they may be within the minimum requirement for all reinforcement. It also appears that both ends of the stirrups and the pin are only bent in a loop and not wrapped or twisted together.
Q: When the rules state that fibers are not permitted, does it mean that polypropylene fibers are not allowed? We don't understand because the internet page says that "Any type of aggregate may be used, except metal, and must pass through a 9.5 mm sieve." Are you sure that it means that only metal fibers are not permitted?
A: Please note it is our general understanding that fibers are not aggregate. Fibers are hair-like or slender material and all kinds of fibers, including metal and polypropylene, are not permitted. Aggregates are grain-like or granular material and may be used, except metal, and must pass through a 9.5 mm sieve.

For further explanation, please refer to the Appendix in the ACI Certification - Craftsman Workbook Publication CP-10(02) for the following definitions:

Aggregates are used primarily as a bonding agent and are defined as a granular material, such as sand, gravel, crushed stone, crushed hydraulic-cement concrete, iron blast-furnace slag, and similar materials used with a hydraulic cementing medium to form concrete or mortar.

Fibers are used primarily as a reinforcing agent and reinforcement is defined as bars, wires, strands, and other slender members that are embedded in concrete in such a manner that the concrete and reinforcement act together in resisting forces.

Therefore, the use of the term "aggregate," as stated in Section 2D above, means any type of "granular material only" may be used, except metal, and must pass through a 9.5 mm sieve. Because fibers are not granular material, but instead hair-like or slender members by definition, they are not to be considered as any type of aggregate. Furthermore, the use of the term "fiber," as stated in Section 2B above, means "All kinds of fibers" are not permitted. Reference: See Section 2D and Appendix in the ACI Certification - Craftsman Workbook Publication CP-10(02).
Q: Can we use white portland cement?
A: Yes, white portland cement is made to conform to ASTM C 150, usually Type I or Type III, and therefore will be allowed. ASTM C 150 "Standard Specification for Portland Cement" defines the principal types of portland cement used in the United States. The primary difference between white portland cement and regular cements is that white cement is made with selected raw materials containing very little iron or manganese oxides, which is the substance that gives concrete made from ordinary portland cements the typical gray color depending mainly on the amount of iron in the cement. Type I or normal cement is general-purpose cement used where special properties of the other types are not required. Type III or high early strength cement is similar to Type I except it is more finely ground so that the chemical reaction in cement can be accelerated and thereby develop strength faster. Reference: ASTM C 150 "Standard Specification for Portland Cement" & the ACI Certification - Craftsman Workbook Publication CP-10(02).
Q: In Section 5C of the EPD rules, the failure criteria are described but there is a significant phenomenon that cracks the egg but is not mentioned. What if the EPD falls down due to vibrations of strikes? If it happens, no structural damage occurred; neither did spalling of concrete, but the egg cracks. If the specimen jumps out of the test tool because of the short height of the supports, will it be returned to the test tool again or not? (I know that jumping and falling of the sample is its fault but my sample is falling due to SHORT HEIGHT of the supports).
A: Yes, if the EPD specimen jumps out of the test tool because of the short height of the supports (approximately 13 mm), it will be returned to the test tool again as stated in Section 5C of the rules.

Please be aware that the E 801 Student Activities Committee has carefully developed a testing devise that helps prevent the EPD from jumping out of the testing tool, which is why it was determined that there was no need to mention it in the rules. We have welded to the base plate supports a metal plate with adjustable guides that can be placed around but not touching the EPDs in order to prevent them from jumping or falling over. In fact, there is a greater chance of the egg being cracked by vibrating out of the egg cup than the EPD specimen jumping out of the test tool. Furthermore, we have devised a seat belt-type device that is strapped around the egg to prevent it from jumping out of the egg cup as mentioned.

However, if any of these phenomenon should still occur, the rules clearly state in Section 5C that if the egg is cracked due to vibration and not due to the structural damage of the EPD or spalling of concrete, a new egg will be used and the loading will continue. The judges at the EPD Competition will be advised that this would include the egg being cracked due to the EPDs vibrating out of the testing devise as well as the egg jumping out of the egg cup as noted in the rules.

However, if it is determined by the judges at the EPD competition that a free-standing EPD falls over under its own weight because it has been made unstable due to structural damage or spilling of concrete at the footings and not from the vibrations of the strikes, the cracking of the egg caused by this unstable condition constitutes failure of the EPD. As the rules clearly state in Section 5C, stability checks will be performed by the judges after every impact load and any unstable EPDs will be disqualified.

Please remember that the rules clearly state in Section 7B and 7C that the appointed judges at the EPD competition will make the final determination whether or not the egg has been cracked due to the vibrations of the strike, which is allowed, or by an unstable EPD, which is not allowed. Reference: See Section 5C, 7B, and 7C.
Q: I have a question regarding the rule for the number of longitudinal reinforcements in each member of the frame in the EPD Competition. The rules state that the longitudinal reinforcement is limited to 8 bars in a cross section. Does the cross section mean the cross section of each member? Or does it refer to the cross section of the frame?

To explain the difference, assume that our concrete frame has 4 legs, two of which are located at each side of the frame. If it is allowed to use 8 longitudinal bars in each element, we will be able to use a total of 32 bars in the four legs. However, if the limitation of 8 bars is for each section of the frame, it seems that we will not be able to use more than 16 bars for the four legs (i.e., 4 bars for each leg). The same question arises if there is more than one element for the top part of the frame.
A: If there is more than one element for the top part of the frame and more than one leg at each side of the frame, you cannot use 8 bars in each element. The limitation of 8 longitudinal bars in a "cross section" is referring to the cross section of the entire frame and not each element of the frame. No matter how many elements there may be in the frame, the longitudinal reinforcement is limited to 8 bars/wires in a cross section of the entire frame.
Q: The rules state that all reinforcement, longitudinal and stirrups, is not to be greater than 1.6 mm diameter, but it does not indicate if there is a limitation to the type of material that can be used. Therefore, my question is simple—can any material be used for the reinforcement bar, including, but not limited to, titanium, carbon steel, etc.?
A: Yes, any material can be used for the reinforcement bars that is not specifically prohibited in the rules.
Q: Can we bend 2 of the 8 longitudinal bars/wires into a continuous loop at both end joints or corners of the EPD, as shown in the following diagram?

The longitudinal reinforcement consists of 8 bars/wires, 2 of them are bent as shown in the above diagram. Can we do this?
A: Yes, the longitudinal bars/wires can be bent into a continuous, stirrup- shaped loop as shown in the diagram at both end joints or corners of the EPD as long as you follow the requirements specified in the rules for all reinforcement, longitudinal and stirrups. Because these 2 longitudinal bars/wires are bent into a continuous, stirrup-shaped loop that could provide some resistance to cracking produced by diagonal tension, they could be considered the same as stirrups located at the end joint or corner and their vertical members would need to be spaced a minimum of 25 mm apart from each other in both the width and length of the EPD to comply with the required minimum allowed spacing of 25 mm for stirrups, as clearly stated in Section 2b) of the rules.
Q: Is 1.6 mm aircraft cable, which is manufactured and sold in a wound state, allowed for reinforcement? My interpretation of the rules would allow us to use it even though it comes wound; and that as long as we didn't physically windthe wired together ourselves, it would be ok. Is this correct?
A: No, the rules clearly state in Section 2b that "No bundling, braiding, twisting together, wrapping, or weaving of reinforcement is allowed." This would prohibit any reinforcement which is manufactured and sold in a wound state such as 1.6 mm aircraft cable. Your interpretation of the rules is not correct since there are no exclusions given for any material being used contrary to what is stated in the rules as long as it is manufactured and sold that way or that you didn’t do physically yourself.
Q: In the rules concerning the use of reinforcement materials, can we use cable that is twisted to the size of 1.5 mm diameter from smaller cable? We do not want to twist two 1.6 mm bars to make larger reinforcement. Is this okay since the reinforcement would not be greater than 1.6 mm diameter or is there no twisting allowed period?
A: No, reinforcement made from smaller cables twisted together is not permitted. The rules clearly state in Section 2b that "No bundling, braiding, twisting together, wrapping, or weaving of reinforcement is allowed."
Q: In the rules concerning the use of reinforcement materials, would Fiber Reinforced Polymer bars (FRP) be acceptable? FRP comes in a stiff matrix of carbon and kevlar fibers that are fashioned together and then covered in an epoxy by the manufacture. We would not actually be the ones "bundling, braiding, twisting together, wrapping, or weaving" the reinforcement, but these could very well be steps in the manufacturing process. The clause "Fibers are not permitted," does this mean that no fibers can be added to the concrete as a secondary reinforcement to make Fiber Reinforced Concrete; or does it pertain to using some sort of "fiber" or cable to create a pre-stressed concrete structure?
A: No, Fiber Reinforced Polymer bars (FRP) are not an acceptable reinforcement material since it would involve the use of "Fibers" and a finished method of "bundling, braiding, twisting together, wrapping, or weaving" the reinforcement which are both prohibited in Section 2b of the rules. Also, these "woven fibers" would be coated in an "Epoxy" resin that serves as a binder which is also prohibited in Section 2a of the rules. Plus, it is important to note that the rules specify that "all reinforcement, longitudinal and stirrups, is not to be greater than 1.6 mm diameter (approx. 16 gauge)" and that the smallest common stock size for Fiber Reinforced Polymer bars (FRP) used in concrete / masonry construction is typically #2 pencil rod or 6.4 mm diameter which would be prohibited in Section 2b of the rules.
Q: Are we allowed to use Glass Fiber for the concrete mix?
A: Per rule 2b, fibers are not allowed.