Q&A COLUMN Augercast Grout Q A A Randy Kura, Ready Mix Supplier asked this question of the ACIP Pile Committee: I want to achieve further water reduction in my auger cast grout mix by adding air-entrainment to achieve 4-5% air (currently utilizing a water reducer/retarder and mid range water reducer). Is there any down side to using air-entrainment in auger cast grout? I do intend to monitor air contents for any spikes and adjust accordingly. Andres M. Baquerizo of HJ Foundation Company responded: I would advise you to check your grout porosity due to air- entrainment if you are in a corrosive environment. In addition, your samples and /or cores might have a lower strength when tested. John Anderson with Specrete can be a good contact to help you optimize your mix. John A. Anderson of Specrete-IP Incorporated replied: I will admit that I am biased since my company manufactures a product called a Grout Fluidifier rather than an air- entraining agent. A grout fluidifier will provide water reduction, a small amount of air that actually acts as an expansive agent, and (in some grout fluidifiers) a water retention agent. This is important to keep the grout from losing water at the bottom of the pile. Set retarding admixtures will not help that problem. You should also check that your customer is not already adding a grout fluidifier. If so, you would definitely not want to add additional air. We would be happy to discuss grout auger pile grout designs. It is the core of our business so we are working on them everyday. Please feel free to write me at [email protected] or call 800-245-3407 x2. Pile Heaving in Expansive Soil Q Daniel Tjandra of the Civil Engineering Department, Petra Christian University, asked the Driven Pile Committee: I did a case study at an apartment building in West Surabaya (Indonesia), which is supported by a driven pile foundation (hollow pile) at 30 m (98 ft) in depth. I did an observation on that pile and the results showed that some piles had heaving about 20-30 cm (8- 12 in). As information, I did an observation after all piles foundations were completed and noted that the driven piles were installed in rainy conditions. There was water on the ground level (about 10 cm or 4 in). Since soil on that area is expansive soil, I guessed that one of the reasons for pile heaving was water penetration in the ground. What do you think about this phenomenon? I need some references about this case, especially the effect of drying and wetting on the adhesion factor in the friction capacity of piles. Q&As are selected from the DFI Committee website forum pages. Answers do not necessarily represent the position of the entire committee or the DFI. DEEP FOUNDATIONS • JAN/FEB 2012 • 89 A Garland E. Likins of Pile Dynamics Inc. responded: Another possibility is failed pile splices. If this is a jointed concrete pile, then the joint might fail during installation perhaps due to high tension forces combined with bending. Then during installation of subsequent piles, the displaced soil from the next pile can have an upward net displacement which can heave the previous pile's top section (or multiple sections). I have seen this before on several Asian projects. The Pile Driving Analyzer can test these piles to see if the joint is broken (would see a clear early reflection from the “gap” initially, but after the "gap" has been closed by several hammer blows the top section is reunited with the bottom section. The impact wave then travels further down pile before reflection. Process of closing gaps can be continued until all gaps are closed and reflection then comes from toe. Such gaps can cause settlement issues if not closed, so a restrike program may be needed to reseat all piles. Pile compression capacity after closing gaps would not likely be compromised, but if there is any tension loading or uplift (or lateral loading), then the capacity is likely to be inadequate since top section might be free. If you need assistance finding a consultant with a Pile Driving Analyzer in Indonesia, please contact me. DFI Award, New Deadlines DFI’s Bermingham Innovation Award April 15 is the deadline for nominations for a new award named for C. William Bermingham, DFI’s president 1986-87. The first winner will be announced later this year at the DFI’s 37th Annual October 16-19, 2012 in Houston. The successful candidate will receive $10,000. The Bermingham Award recognizes innovation in deep foundation technology. Nominees can include new practices in mean and methods, design procedures, and innovations in equipment or materials. The nominees should also exhibit sustainability and must have been used in the past three years. The initial commercial application of the innovation can be no more than 10 years prior to the date of the submission. Outstanding Project Award The April 15 deadline also applies to OPA candidate projects. This process is starting earlier than usual to accommodate the jurors and to allow more time for winning project sponsors to prepare the Deep Foundations magazine cover story. For more information and submission forms, please contact [email protected].
