Geofoam Applications in the Design and Construction of Highway Embankments (2004)

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8-1 CHAPTER 8 GEOFOAM CONSTRUCTION PRACTICES Contents Introduction...................................................................................................................................8-2 Design ...........................................................................................................................................8-2 Block Layout .............................................................................................................................8-2 Longitudinal Geometry .............................................................................................................8-3 Block Layout Design.................................................................................................................8-4 Mechanical Connectors .............................................................................................................8-5 Manufacturing...............................................................................................................................8-5 Introduction ...............................................................................................................................8-5 Flammability .............................................................................................................................8-6 Dimensional Tolerances ............................................................................................................8-8 Manufacturing Quality ..............................................................................................................8-9 Pre-Construction Meeting .........................................................................................................8-9 Construction................................................................................................................................8-10 CQC/CQA ...............................................................................................................................8-10 Site Preparation .......................................................................................................................8-11 Block Shipment, Handling, and Storage .................................................................................8-13 Block Placement......................................................................................................................8-15 Accommodation of Utilities and Road Hardware ...................................................................8-16 Pavement Construction ...........................................................................................................8-16 Post Construction ........................................................................................................................8-18 Summary.....................................................................................................................................8-19 References...................................................................................................................................8-19

8-2 Figures ........................................................................................................................................8-21 ______________________________________________________________________________ INTRODUCTION The focus of this chapter is construction related issues for EPS-block geofoam embankments. However, numerous aspects of both design and manufacturing of EPS-block geofoam for lightweight fill applications, including manufacturing quality control (MQC) and manufacturing quality assurance (MQA), are considered because they interact with and impact construction. Therefore, a discussion of certain design and manufacturing aspects is included in this chapter. Thus, there is some overlap with other chapters in this report, such as Chapter 3 (Design Methodology) and Chapter 9 (Geofoam MQC/MQA) but this overlap allows presentation of a comprehensive chapter on geofoam construction practices. In addition, post-construction activities, including monitoring, are also discussed in this chapter. DESIGN Two construction issues that directly interact and impact the design of an EPS-block geofoam embankment are placement of the blocks and the use of mechanical inter-block connectors. Although a lightweight fill embankment constructed using EPS-block geofoam will consist of a large number of individual blocks, experience indicates that the fill can be analyzed as a single, coherent mass provided the individual EPS blocks are sufficiently interlocked both vertically and horizontally so that they collectively respond as a single, coherent mass when subjected to external loads. This involves consideration of both the overall block layout (which primarily controls interlocking in a vertical direction) and inter-block shear resistance (which primarily controls interlocking in the horizontal direction). Both of these considerations are discussed subsequently. Block Layout Based on a review of the literature, overall guidelines for an appropriate layout of EPS blocks to obtain adequate interlocking in the vertical direction include:

8-3 • Blocks should be placed with their smallest (thickness) dimension oriented vertically. • All blocks should butt tightly against adjacent blocks on all sides. • A minimum of two layers of blocks must always be used for lightweight fills beneath roads. Experience has indicated that a single layer of blocks can shift under traffic loads and lead to premature pavement failure (1). • The blocks must be placed in a pattern such that continuity of the vertical joints between blocks is minimized. The overall objective is to create a layout of blocks that is geometrically interlocked to the greatest extent possible (see Figure 8.1). This is typically accomplished by: ƒ aligning all the blocks within a given layer with their longitudinal axes parallel but offsetting the ends of adjacent lines of blocks, ƒ orienting the longitudinal axes of all blocks in a given layer perpendicular to the longitudinal axes of the blocks within layers placed above and/or below, and ƒ aligning the blocks within the uppermost layer transverse to the longitudinal axis of the road. Figure 8.1. Isometric view of typical EPS block layout for a road embankment. Longitudinal Geometry Two aspects of the geometry of the embankment in the longitudinal direction that need to be considered during design and construction include orientation of the EPS blocks and the transition zone of the geofoam and the non-geofoam sections of the roadway. The top surface of the assemblage of EPS blocks should always be parallel with the final pavement surface (2). Thus, any desired change in elevation (grade) along the road alignment must be accommodated by sloping the foundation soil surface as necessary prior to placement of

8-4 the first layer of EPS blocks. Additionally, the upper surface of the EPS blocks should be horizontal when viewed in cross-section so any crown desired in the cross-section of the final pavement surface should be achieved by varying the thickness of the pavement system (2). The transition zone between geofoam and embankment soil should be gradual to minimize differential settlement. The EPS blocks should be stepped as shown in Figure 8.2 as the embankment transitions from a soft foundation soil that requires geofoam to a stronger foundation soil that can support a soil embankment. However, a minimum of two layers of blocks is recommended to minimize the potential of the blocks to shift under traffic loads. The only exception to this is the final step, which can consist of one block as shown in Figure 8.2. The specific pattern should be determined on a project-specific basis based on calculated differential settlements such as the criteria given in (3) which suggests that the calculated settlement gradient within the transition zone should not exceed 1:200 (vertical: horizontal). Figure 8.2. Typical EPS block transition to a soil foundation (4). Block Layout Design The block layout design can be performed by either the project design engineer or the EPS block molder. Traditionally the block layout design was performed by the design engineer for the project. However, this is appropriate only if the designer knows the exact block dimensions beforehand. In current U.S. practice, there will generally be more than one EPS block molder who could potentially supply a given project. In most cases, block sizes will vary somewhat between molders due to different mold sizes. Therefore, the trend in U.S. practice is to leave the exact block layout design to the molder. The design engineer simply: • shows the desired limits of the EPS mass on the contract drawings, specifying zones of different EPS densities as desired; • includes the above conceptual guidelines in the contract specifications for use by the molder in developing shop drawings; and • reviews the submitted shop drawings during construction.

8-5 Mechanical Connectors If the calculated resistance forces along the nominally horizontal planes between EPS blocks are insufficient to resist the horizontal driving or imposed forces, additional resistance between EPS blocks is required to supplement the inherent inter-block friction. This is generally accomplished by adding mechanical inter-block connectors (typically prefabricated barbed metal plates) along the horizontal interfaces between the EPS blocks. Such connectors provide a pseudo cohesion when viewed from a Mohr-Coulomb strength perspective. At the present time, all such plates available in the U.S.A. are of proprietary designs. Therefore, the resistance provided by such plates and placement location must be obtained from the supplier or via independent testing. Because of the relative costs of these plates, they should only be used where calculations indicate their need. In addition, research and experience indicates that their use is mandatory whenever seismic loads are to be resisted. However, the indiscriminate routine use of mechanical connectors should be avoided because, while not detrimental, they tend to add a significant cost to a project. In addition to their role in resisting horizontal design loads, mechanical connectors have proven useful as a constructability tool to keep EPS blocks in place when subjected to wet, icy, or windy working conditions (5) and to prevent shifting under traffic where relatively few layers of blocks are used (6). Additional information on the use of mechanical connectors can be found in the “Block Interlock” section of Chapter 6. MANUFACTURING Introduction There are three distinct manufacturing issues that impact construction and constructability of EPS-block geofoam embankments: • flammability of the EPS blocks, • dimensional tolerances of the EPS blocks, and • the broad aspect of MQC and MQA.

8-6 Flammability The primary manufacturing issue that impacts construction is flammability. Like most polymeric materials, polystyrene is inherently flammable as is the blowing agent, pentane (butane also has been used but not in the U.S.A.), used in manufacturing EPS. Any residual blowing agent left over from molding EPS blocks outgasses within a few days and is replaced by air. In addition, experience indicates that this inherent flammability of polystyrene ceases to be an issue once EPS is buried in the ground because there is no ignition source and, at least in the long term, there is no oxygen to support combustion, even within the vadose zone. Flammability has been a problem, albeit very rare, during construction when the EPS blocks are exposed to both ample atmospheric oxygen as well as potential ignition sources. As discussed in (1), problems have been encountered from two separate and distinct mechanisms: • Direct ignition of the EPS blocks due to construction activities such as flame cutting or welding that are unrelated to geofoam usage but performed in close proximity of the EPS blocks. • Ignition of residual blowing agent that outgasses after block placement and collects in the joints between blocks (all known EPS blowing agents are heavier than air as thus will not readily disperse into the atmosphere absent positive ventilation). The ignition source is usually some construction activity unrelated to the geofoam. These issues are easily addressed to eliminate the potential for their occurrence in practice. With regard to the direct combustibility of the EPS blocks, specifications, either directly or indirectly, can mandate the use of modified expandable polystyrene as the raw material (a.k.a. bead or resin) for the EPS. The modified resin incorporates an inorganic, bromine-based flame retardant that has proven effective and has no effect on the visual or physical properties of the resulting EPS block. Although the practice in some countries (most notably Norway, the pioneer of EPS-block geofoam as lightweight fill) is to use normal or regular (non-flame-retardant)

8-7 expandable polystyrene raw material for cost reasons (it can be slightly cheaper), the recommended practice incorporated in the provisional standard in Appendix C of this report is to require the use of flame retardant EPS. As this is already the de facto standard practice in the U.S.A., this should present little, if any adjustment issues for the industry. Specification of flame retardancy is accomplished using the indirect method incorporated in ASTM Standard C 578 (7) by requiring a minimum Oxygen Index (OI) of 24 percent which is above the OI of normal atmospheric air (21 percent). The second issue dealing with outgassing of post-molding residual blowing agent is addressed by requiring an adequate seasoning period prior to delivery of the EPS blocks to the project site. This issue has not been formally studied to date for EPS blocks produced in the U.S.A. because seasoning time is affected by the exact formulation (pentane content) of the expandable polystyrene and block dimensions among other factors. Based on available published information (8) as well as anecdotal information obtained by personal communication with both resin suppliers and block molders in the U.S.A., an interim recommendation of three days (72 hours) of seasoning at normal ambient room temperature is proposed and incorporated into the provisional standard in Appendix C of this report. The recommended seasoning time can be accelerated by temporary storage within a heated room. It is worth noting that the minimum seasoning requirement may create problems on projects that are relatively large in size and/or have tight delivery schedules. For example, there were cases in which lightweight fill projects in the U.S.A. used EPS blocks that were less than one day old. Therefore, project-specific decisions might be required that relaxes this seasoning requirement. Experience indicates that this may be permissible to expedite construction work. However, waiver of this seasoning time should be done only with increased vigilance for fire safety as well as worker safety. This may include a prohibition on personal tobacco smoking near EPS blocks as well as “round-the-clock” security for any unseasoned EPS blocks exposed at the end of a day's construction. Furthermore, unseasoned blocks should never be stored and/or

8-8 shipped in any type of enclosed vehicle as any accumulated outgassed blowing agent will pose a potential explosion hazard when the vehicle is opened. Dimensional Tolerances The dimensional tolerances of EPS blocks for geofoam applications affects construction through the ability of the blocks to fit together with minimal gaps and maintain a planar or horizontal surface as subsequent layers of blocks are placed. Thus, the dimensional tolerances of block-molded EPS involves the following aspects: • the permissible variation, relative to some average value, in dimension in each of the three orthogonal linear dimensions (thickness, width and length) of a block, • the orthogonality (squareness) of all corners of a block and • permissible warp or curvature in any one face of a block. To a significant extent, the physical shape and dimensions of EPS blocks are controlled by various factors during manufacturing, especially with regard to the age and quality of the mold used. Because of the wide range in molding equipment currently in use in the U.S.A., blocks of appropriate quality with regard to shape and dimension can neither be assumed nor taken for granted. Therefore, these items must be included in specifications. The provisional standard included in Appendix C to this report incorporates physical and dimensional tolerances used in Norway which are based on decades of experience. It is worth noting that requirements for physical and dimensional tolerances are known to have been relaxed on a project-specific basis in the U.S.A. for cost reasons. This is caused by molders using older molds and performing some post-molding trimming for EPS blocks to meet the physical and dimensional tolerances normally required for geofoam applications. This trimming adds a cost that can be eliminated by the owner or their representative accepting blocks that do not meet normal specifications. There has been no systematic study of how much deviation from normally accepted practice is acceptable. Thus, owners who, either directly or through their representatives, accept blocks with tolerances that exceed those normally used must

8-9 accept a greater, but incalculable, uncertainty with regard to overall final performance of the EPS embankment. Manufacturing Quality MQC/MQA is discussed fully in Chapter 9. However, an overview of the MQC/MQA procedure incorporated in the provisional standard in Appendix C is presented herein. The procedures to be followed once the blocks arrive at the construction site are considered to be part of construction quality assurance (CQA) and thus are considered in the following section. Construction is also when Phase II of MQA is executed by the owner’s CQA agent. The primary components of the provisional standard include the product MQC requirements, product MQA requirements, product shipment, and construction quality requirements to include construction quality control (CQC) and CQA requirements. The provisional standard includes the proposed EPS material designation system shown in Table 9.1 and the minimum allowable values of MQC/MQA parameters shown in Table 9.2. A new sampling protocol shown in Figure 9.4 and a two-phased MQA procedure were developed in this study. Phase I of the MQA procedure is to be performed prior to shipment of EPS blocks to the project site and Phase II is to be performed as the EPS blocks are delivered to the project site. Another key aspect of the proposed MQA procedure is the implementation of a two-tier MQA system, one for molders with third-party certification and the other for those without. Table 9.3 provides a summary of the MQA procedure. Pre-Construction Meeting Once project construction begins, a meeting should be held at the project site prior to the delivery and installation of the EPS blocks. This meeting should, as a minimum, involve the construction contractor and owner's agent who will perform the quality assurance for both the EPS manufacturing (MQA) as well as construction (CQA). Ideally, the design engineer, EPS molder, and EPS supplier (if different from the molder) should also be present. The purpose of this meeting is to review all details relative to the manufacturing and placement of the EPS-block

8-10 geofoam. This is important as the use of EPS-block geofoam in road embankments is still a relatively new technology in many parts of the U.S.A. and thus it is important that all project participants be aware of the key issues for a successful application of this technology. CONSTRUCTION CQC/CQA CQC is a series of internal actions taken by the construction contractor to meet the specifications that comprise part of the contract documents. These specifications are prepared by the design engineer and frequently establish criteria for acceptance based on reference to standards. For traditional earthwork projects, CQC is almost always limited to following a set of procedures for compaction that have been established on past projects of a similar nature. It is important to recognize that many contractors in the U.S.A. are unfamiliar with EPS-block geofoam. Not only must they handle and place it properly, but on most projects they will be the purchaser of the geofoam. Thus the construction contractor must be aware of the pre-delivery aspects of MQA that are discussed in Chapter 9. This means that specifications must be particularly clear and detailed. In addition, a pre-construction conference to review the unique issues and aspects of working with EPS-block geofoam (at which a representative of the EPS molder should also be present) is highly recommended. The contractor shall be directly responsible for all CQC tasks. Items covered by CQC include all earthwork and related activities other than manufacturing and shipment of the EPS- block geofoam. Items of particular relevance include site preparation, block handling and storage, block placement, and pavement construction. In addition to CQC tasks, CQA tasks must be continuous and particularly vigilant and performed by an organization other than the contractor. The CQA agent is either a part of the owner's organization (as is the case with many state DOTs) or an independent materials testing laboratory or consulting engineer (who may or may not be the original designer) retained by the owner. In either case, it is likely for the near future that the CQA agent will also be unfamiliar

8-11 working with EPS-block geofoam. Therefore, both the designer as well as the CQA agent should also be present at the pre-construction conference to review necessary tasks. Site Preparation Experience indicates that proper site preparation prior to placing the EPS blocks is an important factor in both internal stability of the embankment as well as overall constructability. The need to adhere closely to the criteria itemized and discussed below tends to increase with thickness of the geofoam portion of the fill because site preparation has a greater effect as more layers of EPS blocks are placed. If sufficient attention has not been given to site preparation, it becomes increasingly difficult to keep subsequent layers of EPS blocks level or horizontal. Site preparation details to be included in construction specifications are as follows: • Ideally, there should be no standing water or accumulated ice or snow within the area where EPS blocks are to be placed. The presence of water inhibits assuring that the soil subgrade is sufficiently level and free of material that could damage the blocks. However, from a practical perspective EPS-block geofoam is often used at sites where the soil conditions are poor and ground water is inherently at the surface. Experience indicates that some amount of standing water can be accommodated and still have an EPS fill that performs acceptably. It appears desirable to develop a specification that calls for no standing water then relax this requirement on a project-specific basis based on field decisions. However, the potential for hydrostatic uplift of the blocks during construction must be considered if the no standing water requirement is relaxed. Adequate drainage should be maintained of the site during construction to minimize water accumulation along the EPS embankment from heavy rainfall, which can result in hydrostatic uplift of the EPS blocks. • EPS blocks should not be placed on frozen soil subgrade except in the case of intentional construction over continuous or discontinuous permafrost terrain

8-12 where the consequences of eventual ground thawing beneath the fill have been explicitly considered by the designer. • There should be no debris on or large pieces of vegetation protruding from the subgrade on which the EPS blocks are to be placed. Furthermore, the soil particles exposed at the subgrade level should be no larger than coarse sand to fine gravel (2 to 19 mm (0.08 to 0.8 in.)). The objective of these requirements is to prevent physical damage such as puncturing, gouging, broken corners, etc. to the EPS blocks as the first layer is placed on the foundation soil. It is difficult to quantify the effects of this damage so it is considered prudent to take all reasonable steps to make sure the damage does not occur. In some cases, it may be necessary to specify that a bed of sand 12 to 25 millimeters thick (approximately 0.5 to 1 in.) be placed over the existing foundation soil surface. This serves both to cover the coarser in-situ material as well as allow for the necessary leveling of the first layer of blocks (this issue is discussed next). When a sand bed is placed it may be desirable if not necessary to first place a geotextile over the existing ground surface to function as a separator to prevent intermixing of the sand bedding and natural soil (which will be wet and soft in many cases). • Regardless of the foundation soil material (natural soils or sand bed), the surface must be reasonably planar ("smooth") prior to the placement of the first block layer. The required smoothness is a vertical deviation of no more than ±10 mm (0.4 in.) over any 3 meters (9.8 ft) distance. This criterion was developed in Norway over decades of experience (9). Typically, this cannot be achieved by mechanical equipment alone so some manual labor will be required. Note that on many projects the required finished subgrade may not necessarily be horizontal in the direction parallel to the road alignment. This is because the top of the

8-13 assemblage of EPS blocks (and, therefore, the bottom as well) should always be parallel with the grade of the finished road surface in the longitudinal direction (as noted previously, any crown of the road in the transverse direction is, however, achieved by varying material thickness within the pavement system). Therefore, if the road grade is non-horizontal the subgrade on which the EPS blocks will be placed must be non-horizontal along the road alignment as well. This is noted here as it will not always be possible to use a large carpenter's level to check for subgrade smoothness. After the site subgrade has been properly prepared, installation of the EPS blocks can commence. Block Shipment, Handling, and Storage There is one additional issue that straddles the boundary between manufacturing and construction quality. It is primarily the responsibility of the molder (hence discussed in Chapter 9 as an MQC issue) but is enforced by the construction inspection agent (so is also included here as part of CQA). This is the issue of damage of EPS blocks during shipping. Construction damage is generally considered to be physical damage to a geosynthetic product during its shipment to the project site; its placement on site; or during subsequent placement of other materials above it. Typically, the selection of trucks used to ship EPS blocks (almost always a tractor-pulled trailer, but the trailer may either be flat bed or a closed box), the loading of these trucks and the manner in which the load is secured (important when flat-bed trailers are utilized) are all under the control of the EPS molder. Thus, responsibility for the as-delivered condition of the EPS blocks is largely controlled by the molder. This is an important issue to address and incorporate into manufacturing specifications as recent, anecdotal evidence provided by unpublished, confidential sources indicates that block damage on EPS-block geofoam projects within the U.S.A. is not uncommon and is the source of on-site problems over block acceptance. The reason for the damage appears to be the preferred use of flat-bed trucks to transport EPS blocks because the

8-14 blocks have gotten longer with newer molding equipment placed on line during the 1990s. Because the lightweight EPS blocks must be securely strapped to prevent their movement during shipment, it is not uncommon for EPS blocks to arrive at the job site with numerous indentations of the edges along the sides of the blocks from the strapping as well with breakage at the end corners of the blocks. One shipping method that may be considered to minimize damage to the blocks is to use structural angles along the top edge of the exterior blocks that would accommodate the strapping. At all stages of construction the EPS blocks should be handled in a manner so as to minimize physical damage to the blocks. Lifting or transporting the blocks in any way that creates dents or holes in the block surfaces is strongly discouraged. Careful handling is recommended because it is impossible to quantify when block damage starts to impair performance of the final EPS mass. Therefore, it is recommended that damage to the blocks be discouraged and avoided. Experience indicates that damage during shipping, on-site handling, and temporary on-site storage of EPS blocks can be easily avoidable and thus is unnecessary. However, project specifications must contain appropriate language to the effect that EPS blocks with indentations and pieces broken off will be rejected by the owner's agent on site to encourage careful handling. If blocks are to be stockpiled until placement, a secure storage area should be designated for this purpose. The blocks should not be trafficked upon, especially by any vehicle or equipment. The storage area should be away from any heat source or construction activity that produces heat or flame because of block flammability. Tobacco smoking should also be prohibited in the storage area. Blocks should be secured with sandbags and similar "soft" weights as necessary to prevent their being dislodged by wind. Protection against ultraviolet (UV) damage in the relatively short term exposure of temporary storage is generally not required. Overall, it is generally unnecessary and, in fact, even undesirable to cover the EPS blocks in any way. There is anecdotal project experience from unpublished, confidential sources that EPS that was covered

8-15 temporarily with a dark-colored geomembrane built up sufficient heat to locally melt and distort some of the EPS. EPS is not an inherently dangerous or toxic material (other than the flammability issues discussed previously) so there are no additional explicit safety issues to be observed other than normal construction safety. However, extra caution is required during wet or cold weather. The surfaces of the EPS blocks tend to be more slippery wet than dry. When air temperatures approach or go below freezing, a thin layer of ice can readily develop on the exposed surfaces of EPS blocks if the dewpoint is sufficiently high. Thus, the surfaces of the EPS blocks can pose handling difficulties and slip hazards in this condition. The air temperature does not have to go below freezing for this phenomenon to occur (it is basically the same phenomenon that can cause differential icing of the final pavement surface). In addition to the safety issue, EPS blocks should not be placed above blocks in which ice has developed on the surface because of the potential for the blocks to slide due to water, wind, or other horizontal loads while the ice is still present between the blocks. Block Placement Blocks should be placed according to the pattern specified in the design drawings or approved contractor-submitted shop drawings. Particular care is required if EPS blocks of different density are to be used on the project. Blocks should be placed tight against adjacent blocks on all sides. Every effort should be made to eliminate gaps at the vertical joints between the blocks. If the blocks meet the specified dimensional tolerances and are placed carefully starting with a planar subgrade as discussed previously, the surface of a given layer of blocks should provide a reasonably planar surface for the next layer of blocks. However, in cases where the block surface may become irregular, the most common solution is to place a thin layer of unreinforced portland cement concrete (PCC) as a "mud slab" or working surface that is leveled for placing subsequent block layers. However, such a slab must not be placed without prior

8-16 review by the project designer because the mud slab will induce an additional permanent vertical stress on the foundation soil which needs to be evaluated. If necessary to field cut blocks, the most precise cutting can be done with a portable hot- wire device that the EPS molder can provide or at least provide assistance with assembling. A wire saw or chain saw can also be used. In particular, a chain saw appears to be the most commonly used cutting tool in U.S. practice when a smooth, precise final surface is not required. Hot-wire cutting devices made for cutting EPS typically do not cause the EPS to ignite. However, consideration should be given to having a fire extinguisher available during any hot-wire cutting of EPS blocks. At all times when the EPS blocks are exposed, extreme care must be exercised to keep all sources of heat or open flame away from the blocks. Even tobacco smoking should be discouraged for safety reasons. The surfaces of the EPS blocks shall not be directly traversed by any vehicle or construction equipment during or after placement of the blocks. The final surface of the EPS blocks shall be covered as shown on the contract drawings. Care shall be exercised during placement of the cover material so as not to cause any damage to the EPS blocks. Accommodation of Utilities and Road Hardware The alternatives for accommodating shallow utilities and road hardware (barriers and dividers, light poles, signage) is to provide a sufficient thickness of the pavement system to allow conventional burial or embedment within soil or, in the case of appurtenant elements, provide for anchorage to a PCC slab or footing that is constructed within the pavement section. Pavement Construction The pavement system is defined for the purposes of the standard in Appendix C as all material placed above the EPS blocks within the limits of the roadway, including any shoulders. Care must be exercised when constructing the pavement system so the separation layer (if one is used) and/or EPS blocks are not damaged. If a separation layer is to be placed on the top surface of the final layer of EPS blocks, this surface must be reasonably clean and dry prior to placement.

8-17 In addition, care must be exercised during placement of the separation material so that the EPS blocks are not damaged, unleveled, or moved so that gaps occur between the blocks. In general, the pavement system can be constructed in the normal manner with only a few cautions related to the presence of the EPS blocks. The most critical phase is the placement and compaction of the initial lift or layer of soil on the separation layer or EPS blocks. Vehicles and construction equipment such as earthmoving equipment must not directly traffic on the EPS blocks or separation layer (even if a PCC slab is used as it is still possible to overstress the underlying EPS). The only construction guideline that provides maximum construction equipment loads is in the United Kingdom guidelines where it is recommended that the maximum weight of compaction equipment be limited to 58.8 kN/m width (4 kips/ft) of roll and that construction equipment be limited to a maximum applied pressure of 20 kPa (400 lb/ft2) (10). However, the type and size of construction equipment should be limited to wheel, track, or roller loads that produce maximum applied stresses that do not exceed the elastic limit stress of the EPS, i.e., in no case should vehicle loads exceed the elastic limit stress of the EPS. One construction procedure that can be used to minimize damage to the EPS blocks is to use relatively lightweight equipment to push approximately 300 mm (12 in.) (minimum) of soil or aggregate onto the EPS blocks or separation layer before compacting the material. Typically placement of the first lift of unbound material is accomplished by pushing the material ahead using a relatively small bulldozer or front-end loader. Placement of additional unbound and bound layers of the pavement system can then be placed in the normal manner although trafficking of the surface by trucks or heavy equipment of all types should be minimized or avoided altogether until the pavement is completed. If necessary, temporary mats should be provided to distribute vehicle loads. Stockpiling of construction materials on the geofoam must be conducted with care to minimize overstressing of the EPS blocks. After completion of the pavement system, vehicle loads should not exceed the design vehicle load.

8-18 The most effective type of compaction equipment to utilize to meet the desired compaction requirements will depend on the characteristics of the material to be compacted. For example, in (11) it was observed that a plate vibrator was the most suitable equipment for compaction of unbound material in a pavement structure over EPS blocks. The static roller was found to be less efficient than the plate vibrator and the compaction requirements could not be achieved with a vibratory roller. Therefore, consideration can be given to observing and testing a test area or strip with the actual materials that will be placed and compacted to determine the most suitable type of compaction equipment needed to achieve the required compaction requirements. When verifying compaction of the unbound pavement material, nuclear moisture-density gauges have sometimes yielded incorrect results. This is caused by the water content of the soil being inferred from a count of radioactive scattering caused by hydrogen atoms. In normal soil, hydrogen atoms only occur in water. However, EPS contains hydrogen and thus spurious water content results can be produced from nuclear density gauges. It is suggested that this issue be discussed with the manufacturer of the nuclear moisture-density gauges to determine if this is a potential problem. It is often desirable to check the initial readings obtained with such gauges using a traditional mechanical procedure such as a sand cone apparatus to obtain the total (damp) unit weight or density of the unbound material followed by oven or other traditional methods for drying of a soil specimen to determine its water content. POST CONSTRUCTION On routine projects, no instrumentation and post-construction monitoring or testing of EPS-block geofoam is required. However, because EPS-block geofoam is still considered a novel construction material in some states the owner and designer may elect to instrument and monitor various parameters. There is no "standard practice" for this so any instrumentation and observation program would have to be developed on a case-by-case basis. Discussions of instrumentation for post-construction monitoring can be found in (12,13).

8-19 SUMMARY Various aspects of both design and manufacturing of EPS-block geofoam for lightweight fill applications interact with and impact construction. Two construction issues that directly impact the design of an EPS-block geofoam embankment is placement of blocks and mechanical connectors. Three manufacturing issues that impact construction and constructability include the flammability of the EPS blocks, dimensional tolerances of the EPS blocks, and the broad aspect of MQC and MQA. Items covered by CQC/CQA include all earthwork and related activities other than manufacturing and shipment of the EPS-block geofoam. Items of particular relevance include site preparation, block handling and storage, block placement, and pavement construction all of which are discussed in this chapter. REFERENCES 1. Horvath, J. S., “Lessons Learned from Failures Involving Geofoam in Roads and Embankments.” Research Report No. CE/GE-99-1, Manhattan College, Bronx, NY (1999) 18 pp. 2. “Matériaux Légers pour Remblais/Lightweight Filling Materials.” Document No. 12.02.B, PIARC-World Road Association, La Defense, France (1997) 287 pp. 3. Briaud, J.-L., James, R. W., and Hoffman, S. B., “Settlement of Bridge Approaches (The Bump at the End of the Bridge).” NCHRP Synthesis 234, Transportation Research Board, Washington, D.C. (1997) 75 pp. 4. Horvath, J. S., Geofoam Geosynthetic, , Horvath Engineering, P.C., Scarsdale, NY (1995) 229 pp. 5. Horvath, J. S., “A Concept for an Improved Inter-Block Mechanical Connector for EPS- Block Geofoam Lightweight Fill Applications: 'The Ring's the Thing',” In Manhattan College-School of Engineering, Center for Geotechnolgy [web site]. [updated 8 September 2001; cited 20 September2001]. Available from http://www.engineering.manhattan.edu/civil/CGT/T2olrgeomat2.html; INTERNET. 6. Duskov, M., “EPS as a Light Weight Sub-base Material in Pavement Structures; Final Report.” Report Number 7-94-211-6, Delft University of Technology, Delft, The Netherlands (1994) . 7. ASTM D 578-95, “Standard Specification for Rigid, Cellular Polystyrene Thermal Insulation.” Vol. 04.06, American Society for Testing and Materials, West Conshohocken, PA (1999) . 8. Coughanour, R. B., “Pentane Issue.” Presentation at the 16th Annual SPI Expanded Polystyrene Division Conference, San Diego, CA, (1988). 9. “Guidelines on the Use of Plastic Foam in Road Embankment.” Public Roads Administration, Road Research Laboratory, Oslo, Norway (1980) 2 pp. 10. Sanders, R. L., and Seedhouse, R. L., “The Use of Polystyrene for Embankment Construction.” Contractor Report 356, Transport Research Laboratory, Crowthorne, Berkshire, U.K. (1994) 55 pp.

8-20 11. Duskov, M., “EPS as a Light-Weight Sub-Base Material in Pavement Structures,” Doctor of Engineering thesis, Delft University of Technology, Delft, The Netherlands (1998). 12. Dunnicliff, J., “Geotechnical Instrumentation for Monitoring Field Performance.” NCHRP Synthesis of Highway Practice 89, Transportation Research Board, Washington, D.C. (1982) 46 pp. 13. Dunnicliff, J., Geotechnical Instrumentation for Monitoring Field Performance, , Wiley- Interscience, New York (1988) 577 pp.

FIGURE 8.1 PROJ 24-11.doc 8-21

FIGURE 8.2 PROJ 24-11.doc 8-22