Geofoam Applications in the Design and Construction of Highway Embankments (2004) / Chapter Skim
Currently Skimming:
Pages 544-592
The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.
From page 544... ...
9-1 CHAPTER 9 GEOFOAM MQC/MQA Contents Introduction...................................................................................................................................9-3 Definitions ....................................................................................................................................9-3 Basis of the Provisional Standard .................................................................................................9-5 Overview..................................................................................................................................9-5 Problems with Current Standards ............................................................................................9-5 Key Technical Attributes of EPS-Block Geofoam Affecting Design......................................9-7 Philosophy Incorporated in the Provisional Standard..............................................................9-8 Proposed EPS Material Designation and Minimum Allowable Values of MQC/MQA Parameters................................................................................................................................9-9 MQC/MQA Test Requirements ..................................................................................................9-12 Overview................................................................................................................................9-12 Relevant Aspects of EPS-Block Geofoam for MQC/MQA Testing......................................9-12 Introduction.......................................................................................................................9-12 Flammability .....................................................................................................................9-12 Density ..............................................................................................................................9-12 Pre-Puff Quality and Fusion During Molding ..................................................................9-13 Seasoning ..........................................................................................................................9-13 Test Protocols .......................................................................................................................9-14 Record Keeping ................................................................................................................9-14 Sampling ...........................................................................................................................9-15 Testing ..............................................................................................................................9-18
|
From page 545... ...
9-2 Basis of the Proposed Manufacturing Quality Control (MQC) and Manufacturing Quality Assurance (MQA)
|
From page 546... ...
9-3 INTRODUCTION One of the overall objectives of NCHRP Project 24-11 was to develop a standard in the American Association of State Highway and Transportation Officials (AASHTO) format to optimize usage and performance for expanded polystyrene (EPS)
|
From page 547... ...
9-4 • Quality control (QC) refers to those actions taken by a product manufacturer or service provider to ensure that the final product or service meets certain minimum criteria.
|
From page 548... ...
9-5 delivery to a project site as opposed to performing MQA once the material is delivered on site. As a simple yet common example to illustrate this, structural steel is generally accepted on site based on mill certificates or similar paperwork.
|
From page 549... ...
9-6 treatment alternatives. The percentage of in-plant regrind and post-consumer recycled material and how it is fused into blocks may have varying affects on the mechanical properties (2,3)
|
From page 550... ...
9-7 within an EPS block. Molders in the U.S.
|
From page 551... ...
9-8 Standards must complement the design methodology so the necessary engineering properties are present in the geofoam. Therefore, in developing standards for future practice, two primary technical attributes included in the design methodology for EPS-block geofoam used as lightweight fill in road construction were considered.
|
From page 552... ...
9-9 methodology is based on maintaining the long-term compressive stresses below the elastic-limit stress (within the elastic range) to keep long-term compressive strains within acceptable levels to limit both creep and plastic deformations.
|
From page 553... ...
9-10 tangent Young's modulus for use in compression calculations is approximately 100 times this value, i.e.
|
From page 554... ...
9-11 elastic limit stress and initial tangent Young's modulus were developed from observed correlations with the minimum density values from individual test specimens also shown in Table 9.2. These values of elastic limit stress and initial tangent Young's modulus in Table 9.2 would be the values used in analysis and design.
|
From page 555... ...
9-12 MQC/MQA TEST REQUIREMENTS Overview The requirements of MQC/MQA testing are somewhat different from those for testing for analysis and design parameters that were discussed in Chapter 2 because explicit testing for certain geotechnically relevant parameters, such as creep, are rarely performed for routine projects. The basis for this is almost 30 years of experience with EPS-block geofoam as lightweight fill for road earthworks has demonstrated that acceptable and cost-effective designs can be developed by correlating EPS density with these engineering parameters.
|
From page 556... ...
9-13 As discussed in Chapter 2, it is generally considered good practice in the U.S.A. to specify flame-retardant EPS for all geofoam applications.
|
From page 557... ...
9-14 by personal communication with both resin suppliers and block molders in the U.S.A., the tentative recommendation for the seasoning time is a minimum of three days at normal ambient room temperature although this time might be shortened by storage at elevated temperatures (not all block molders are equipped for this)
|
From page 558... ...
9-15 are to be supplied, the use of no marking shall be considered an acceptable marking for one of the densities as long as it is used for the lower (lowest) density EPS blocks supplied to the project.
|
From page 559... ...
9-16 • Compressive strength is linked primarily to EPS density, which is correct. • Density of block-molded EPS is always the least at the corners, edges, and sides of a block, which is now known not to be always correct.
|
From page 560... ...
9-17 An assessment of the test protocols used to date indicates that current sampling and testing protocols are not keeping pace with the current state of knowledge. The specific reasons are: • The stiffness parameters of elastic limit stress and initial tangent Young's modulus must be tested.
|
From page 561... ...
9-18 all necessary parameters (listed below) tested at each of the three locations (A.
|
From page 562... ...
9-19 Manufacturing quality control (MQC) is internal actions taken by the manufacturer of a product (EPS block molder in this case)
|
From page 563... ...
9-20 • The MQA agent may be a company (typically a materials testing laboratory or geotechnical consulting firm in the case of EPS-block geofoam) hired by the purchaser of the product (generally a construction contractor in the case of EPSblock geofoam)
|
From page 564... ...
9-21 block delivered for a given project must equal or exceed the specified minimum allowable given in Table 9.1; (5) The density of any test specimen prepared from a sample cut from a production block for a given project must equal or exceed the specified minimum allowable given in Table 9.2 (which will generally be approximately 10 percent less than the overall allowable minimum for an entire block)
|
From page 565... ...
9-22 PRODUCT MANUFACTURING QUALITY CONTROL (MQC) REQUIREMENTS Overview There are numerous factors that affect the final quality of block-molded EPS, beginning with the source and age of the expandable polystyrene raw material used and ending with numerous aspects of the molding process.
|
From page 566... ...
9-23 dependent on there being adequate air circulation between stored blocks and adequate positive exhaust ventilation within the area used to store blocks during post-molding seasoning. There is one issue that straddles the boundary between manufacturing and construction quality.
|
From page 567... ...
9-24 MQC Parameters To Be Measured Table 9.2 indicates the proposed material designations and the minimum allowable values of MQC/MQA parameters for individual test specimens. Allowable Raw Material The EPS-block geofoam shall consist entirely of expanded polystyrene.
|
From page 568... ...
9-25 accelerated by temporary storage within a heated room) is proposed prior to shipment and incorporated into the provisional standards.
|
From page 569... ...
9-26 PRODUCT MANUFACTURING QUALITY ASSURANCE (MQA) REQUIREMENTS Overview The traditional approach taken for MQA of EPS-block geofoam in lightweight fill applications is to rely solely on post-delivery block sampling and testing by the owner's testing laboratory or engineer.
|
From page 570... ...
9-27 for block-molded EPS may not be sufficiently stringent for lightweight fill applications. • There is recent project experience in the U.S.A.
|
From page 571... ...
9-28 Resolution of the above issues and problems with both pre- and post-delivery MQA practice as they currently exist to develop an MQA strategy that balances both the technical need to verify product quality and the associated cost will require an evolutionary process that includes input from and dialog between both EPS molders, their customers (usually a construction contractor) , the design engineer, and the ultimate owner.
|
From page 572... ...
9-29 Phase I Phase I consists of pre-certification of the molder and is performed prior to shipment of EPS blocks to the project site. The purpose of the pre-certification procedure is to verify that the molder has the ability to provide EPS-block geofoam of the desired quality.
|
From page 573... ...
9-30 when multiple densities are to be used on the same project, an easily visible color marking system should be used to distinguish between blocks of different density (no marking can be used as one of the requisite "markings" but it must always be for the lower/lowest density)
|
From page 574... ...
9-31 The procedures to be followed once the blocks arrive at the construction site are considered part of CQA and thus are considered in Chapter 8. However, construction is also when Phase II of MQA is executed by the owner's CQA agent.
|
From page 575... ...
9-32 specified requirements with respect to the elastic limit stress, initial tangent Young's modulus, compressive strength, and flexural strength. Figure 9.4 provides a basic plan for sampling location.
|
From page 576... ...
9-33 For molders with previously approved third-party certification, the following process is recommended for the subphases of Phase II MQA: • Phase IIa should be applied to each truckload. • Phase IIb should be applied to each truckload.
|
From page 577... ...
9-34 Molders Without Third-Party Certification For EPS molders without third-party certification, the on-site (Phase II) MQA is more critical than for those molders with third-party certification: • Phase IIa should be applied to each truckload.
|
From page 578... ...
9-35 PRODUCT SHIPMENT Prior to delivery of any EPS-block geofoam to the project site, a meeting shall be held between, as a minimum, the owner's agent and contractor. The supplier and/or molder of the EPSblock geofoam may also attend at the contractor's discretion to facilitate answering any questions.
|
From page 579... ...
9-36 requirements, product shipment, and construction quality requirements to include construction quality control (CQC) and construction quality assurance (CQA)
|
From page 580... ...
9-37 However, there are issues and problems, both real and perceived, with both pre- and post-delivery MQA practice as they currently exist. Resolution of these issues and problems will require an evolutionary process that includes input from and dialog between both EPS molders, their customers (usually a construction contractor)
|
From page 581... ...
FIGURE 9.1 PROJ 24-11.doc 9-38
|
From page 582... ...
FIGURE 9.2A PROJ 24-11.doc 9-39
|
From page 583... ...
FIGURE 9.2B PROJ 24-11.doc 9-40
|
From page 584... ...
FIGURE 9.3 PROJ 24-11.doc 9-41
|
From page 585... ...
FIGURE 9.4 PROJ 24-11.doc 9-42
|
From page 586... ...
TABLE 9.1 PROJ 24-11.doc Material Designation Minimum Allowable Density, kg/m3 (lbf/ft3) AASHTO (proposed)
|
From page 587... ...
TABLE 9.2 PROJ 24-11.doc Material Designation Dry Density, kg/m3 (lbf/ft3) Compressive Strength, kPa (lbs/in²)
|
From page 588... ...
TABLE 9.3 PROJ 24-11.doc Phase Subphase Start of Phase Description Requirements Possible Actions I None Prior to shipment to the project site Precertification of the molder Approved third-party certification: Molder will • Identify the organization providing this service. • Provide detailed information as to the procedure and tests used by this organization to verify the molder's compliance with the specific requirements of this specification.
|
From page 589... ...
TABLE 9.3 PROJ 24-11.doc II IIa As the EPS blocks are delivered to the project site On-site visual inspection of each block delivered to the project site to check for damage as well as visually verify the labeled information on each block Approved third-party certification: • Each truckload. Owner's agent should inventory each and every block.
|
From page 590... ...
TABLE 9.3 PROJ 24-11.doc II IIb As the EPS blocks are delivered to the project site On-site verification that the minimum block dry density as well as the physical tolerances meet specificatio ns Approved third-party certification: • Each truckload. Initially, only one block per load.
|
From page 591... ...
TABLE 9.3 PROJ 24-11.doc II IIc As the EPS blocks are delivered to the project site Confirming the EPS engineering design parameters related to stiffness as well as the quality control strength parameters Approved third-party certification: • Discretion of owner's CQA agent. For example, can be omitted entirely on a small project, can perform testing only at the beginning of a project, or can be done on an ongoing basis.
|
From page 592... ...
TABLE 9.3 PROJ 24-11.doc II IId As the EPS blocks are placed As-built drawing(s) • Owner's agent with the cooperation of the contractor will prepare as-built drawing(s)
|
Key Terms
This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More
information on Chapter Skim is available.