Pervious Cylinder Competition Questions

Q: I have encountered difficulties in finding some of the materials specified in the competition instructions. Additionally, I have had difficulty finding detailed information on assembling the permeameter. It seems there are various ways to construct it, or that personal judgment is used to develop it. I would greatly appreciate any audiovisual support or additional materials that could guide me through the assembly process.

A: Substitutes for parts in the permeameter can be made as needed—the parts list is provided with the intention to show what was used to build the ACI Permeameter that will be used to test the specimens at the Student Competition. A walkthrough of the permeameter construction does not currently exist, so visual references would need to be used to construct the permeameter. The committee will aim to rectify this issue for future competitions.

Q: In the Unit Conversion sheet on the official mix design spreadsheet, there are cells for the slump and density of the concrete. However, I don’t see anything on the official submission sheet and looking at the FAQs, filling out the unit conversion sheet is not a requirement. Is there a reason for slump and density on the unit conversions sheet/are slump and a measured mix density requirements for the final submission?

A: The measured slump and density blanks on the units conversion page of the Mix Design Spreadsheet are hold-overs from previous competitions. You are correct that the unit conversion page is not required and is provided as a tool. Only the stated documents are required for the submission.

Q: We would like to know if the product attached can be use as binders for the competition?

A: The committee does not review and approve individual mixture components - mixture materials must meet the Rules section 2.

Q: What are the requirements for the Mixture Design Electronic Report? Should we include photos? Or any analysis?

A: The requirements for the Mix Design Submittal can be found in section 4 of the rules.

Q: I was wondering whether rapid set cement was allowed in the competition. I was looking for the rules and could not find anything that said it could or could not be used.

A: For mixture materials please refer to rules section 2. Cementitious materials are specifically detailed in section 2. c.

Q: Should the mixture design used be that of the American Concrete Institute? Or can we use other kinds of design for the mixture?

A: Any design methodology may be used to generate an accurate pervious mixture design. As stated in Rules Section 2. a.: Only materials listed in the Official Mixture Design spreadsheet and described below shall be used. Mixtures shall be proportioned to result in a pervious concrete material meeting the definition of pervious concrete according to ACI 522R.

Q: Regarding the curing age of the cylinders, in the contest rules, it does not specify what is the minimum age they must have; we would like to know if they could be 14 days for the competition or what is the minimum age (7, 14, or 28 curing days) for the cylinders?

A: The Rules do not require a minimum age for the specimens. It is known that cementitious concrete gains strength over time as the hydration process advances; as such, it is recommended that the specimens be as old as possible to obtain the greatest possible splitting tensile strength at the time of testing. This age will be limited by the completion of the pervious concrete mixture design.

Q: I have a doubt about the specifications on coarse aggregate for the competition. It is mentioned that the aggregate shall not be bigger than 3/4 inch in nominal size. This means that there cannot be particles bigger than that in the aggregate but still fulfill norm C33? For example, aggregate No. 67: in the norm, it is allowed to have 0 to 10% of 3/4-inch aggregate; thus, I can make a mixture without that size. Otherwise, for example, should I use aggregate No. 7, which does not allow particles of that size by any means? (It is still not clear if aggregate No. 67 is legal for the competition.)

A: Yes. As defined in ACI Education Bulletin E1-16, Aggregates for Concrete, a No. 67 stone would have a nominal maximum size of 3/4 inch; however, most production-pervious concretes use aggregates less than 1/2 inch in size (chips). Additionally, in previous student competitions, coarse-graded mixtures with large voids have had difficulty in being sealed in the permeameter test assembly.

Q: Rules 2b and 4bii2 state that an ASTM C136 gradation report is required. Is this something an official company must do or is this to be done by a group of students?

A: The rules state no requirement on the entity performing the test, only that it must be performed, with results included in the submittal.

Q: We are assessing the results of these mixtures, however, we understand how P and S are obtained (from the cylinder performance prize category equation), but for M we are wondering how is it computed? Related to M, is the amount of cement used in the mixture related to this score, or how is it taken into account to decide the best cylinder performance? If we optimize the amount of cement in the mixture, does it give us a higher score in the contest?

A: The Mix Design Score, M, is based on the accuracy and validity of the Pervious mix design as reported on the official mixture design spreadsheet. An accurate design sheet with appropriate volumes, masses, and specific gravities would receive a full score. All entries will be evaluated based on the same criteria stated in the rules. The committee is not able to comment on specific mixtures or approaches to the competition.

Q: Are we restricted to working on pervious concrete or can we also work on pervious geopolymer concrete?

A: While the committee is interested to see creative solutions to the competition, we are afraid that geopolymer concrete is not acceptable in the competition this year. Section 2 of the rules do mention that exceptions to cementitious components can be made on a case-by-case basis; in this case, geopolymer binders are not allowed. However, the rules for the next competition will consider this option seriously.

Q: Is it ok for us to use an amount of cement below 270 kg/m³?

A: Allowable mixture components are detailed in Item 2 of the rules. There are no limits placed on minimum or maximum mixture contents in the rules.

Q: How will the cylinder diameter be measured?

A: The diameter is measured with calipers.

Q: Will the cylinder be wet or dry for splitting tensile test? What condition will the testing cylinder be between infiltration and splitting tensile test? Will it be drying in between (if so, how long), or is splitting tensile testing immediately after infiltration?

A: All teams will be treated with the same conditions. The current plan will be to have all specimens kept in a wet condition with damp towels while they are on deck to test. Split tensile testing is performed immediately following infiltration, but the several-second infiltration time typically results in a bit of a wait at the testing machine.

Q: We'd like to ask you if it is ok to use instead of the regular lime stone aggregates, aggregates made from fly ash we prepare them at our lab.

A:Allowable mixture components are detailed in Item 2 of the rules. The use of any component that does not meet these requirements subjects the team to possible penalty or disqualification.

Q: Is there a problem if the complementary Units Conversion Page is unused?

A:The Units Conversion Page on the Official Mixture Design Spreadsheet is an additional helpful page for non-SI students. It will not be reviewed as part of the judging process and does not need to be populated.

Q: Can you send us all the pieces and sizes of the permeameter (dimensions) that you will use on the competition?

A: McMaster-Carr www.mcmaster.com
3 in. gate valve - 3999K22
12 in. long 4 in. ID acrylic: 8486K577
Quick-release worm clamp: 5588K12
Tire inner tube: 4991T33

Home Depot: www.homedepot.com
4 in. flex coupling
3 in. to 4 in. flex coupling
3 in. street elbow

American Cube Mold: www.americancubemold.com
Rubber bands - These are 1/2 in. in thickness and orange - I believe they are synthetic rubber and have a higher durometer than typical rubber bands
3 in. ACM1K-3
5 in. ACM1K-5

Q: What's the granulometric composition that the permeable concrete must have for the competition?

A: I believe you are asking about the required gradation of the aggregate for pervious concrete. Aggregates shall meet the rules, notably item 2.b., but there are no requirements for the gradation of the material; however, it must be measured and reported. ACI 522 offers guidance on aggregates for previous concrete mixtures.

Q: Can you send us the paper about the design prices?

A: While previous competitions included cost as a portion of the competition, that section has been removed. Please ensure you are using the correct version of the rules — read this PDF.

Q: Is the cylinder cut the day of the competition or do we have to cut before the competition? Also, do you have more information about the permeability test?

A: No, the cylinders should be fully prepared and in a dry condition at check-in the morning of the competition. We will not have equipment available for concrete sawing or cutting at the competition. The permeability test is a falling head infiltration test as described in the rules item 5.c.iii. The chamber is 4 in. ID and flow measured from 9 in. above the specimen until the water level reaches 1 in. above.

Q: I have a question regarding the acceptable mixture materials within the mixture design. The team was considering to use nanoparticles in the mixture. Is this acceptable within the rules? And if so, are there any restrictions within the material because nanoparticles vary in composition?

A: All mix ingredients would need to meet the requirements of section 2 of the rules. The applicable section depends on the use and properties of the material. An inert nanomaterial would need to meet the requirements of an aggregate and be included in the gradation. Pozzolanic nanomaterials such as colloidal silica would need to meet the requirements for cementitious and supplementary cementitious materials.

Q: Our team is considering to use a product called “colloidal nano-silica” as per the attached data sheet. The product has the same chemical composition as liquid silica fume, except that the size of silica particles is smaller. Would using this product be acceptable in the competition?

A: According to the rules, section 2.c., colloidal silica would be acceptable if it meets ASTM C1240.

Q: Are we allowed to use latex for the pervious concrete cylinder competition?

A: Materials used for the pervious concrete mixture must meet the requirements of section 2 of the rules. Section 2.d. lists the acceptable chemical admixtures, so any used would have to meet the requirements of that section.

Q: My admixture (aggregate, fiber) is XXXXXX. Is that acceptable?

A: Allowable mixture components are detailed in Item 2 of the rules. The use of any component that does not meet these requirements subjects the team to possible penalty or disqualification.

Q: What is the loading rate for the splitting tensile strength test at competition?

A: ASTM C496 specifies a load rate of 0.7 to 1.4 MPa per minute; however, this should be considered a minimum rate for the competition. Actual load rate will depend upon the total number of specimens and an estimated total strength to ensure that all specimens can be tested within the competition window on Sunday.

Q: What is on the parts list of the falling-head permeability test for this year's Pervious Concrete Competition?

A: Pervious Infiltrometer parts list – part # and source given for example. Similar parts may need to be sourced differently outside the United States.

3" gate valve - McMaster-Carr part 3999K22

12" long 4" ID acrylic tube - McMaster-Carr part 8486K575

4x Quick-release worm clamp - McMaster-Carr part 5588K12

4" flex coupling (available from home improvement stores)

3" to 4" flex coupling (available from home improvement stores)

3x 3" PVC street elbow (available from home improvement stores)

3" PVC Cleanout Tee (available from home improvement stores)

3" PVC drain plug (available from home improvement stores)

3" Rubber Bands of synthetic rubber - American Cube Mold part ACM-K-3

tire inner tube (to cut up and use to seal specimen into assembly) - McMaster-Carr part 4991T33

Sample suppliers:

McMaster-Carr: https://www.mcmaster.com/

American Cube Mold: https://www.americancubemold.com/

PVC Shrinkwrap film: https://uspackagingandwrapping.com/heat-shrink-wrap/pvc-shrink-wrap/pvc-shrink-wrap-rolls-500-ft.html