ICPI Foundation for Education & Research
Summer - 2018
New Projects Funded
Life-cycle cost studies for interlocking concrete pavements
Applied Research Associates, Inc. won a $53,500 grant to provide 10 LCCA studies. This is in response to the ICPI Commercial Technical Promotion Team requesting life cycle costs from a range of regions. This proposal will focus on interlocking concrete pavements (ICP)rather than the permeable version (PICP). Staff will survey CTP for possible candidate projects. Project completion is aiming for fall 2019.
Permeable Design Pro – Upgrade software program to UC Davis subbase thickness tables method
Applied Research Associates, Inc won a $48,430 grant to upgrades the current software program to include these cost-efficient subbase thickness tables. The program will also include an operation that automatically finds the number of days per year rainfall exceeds the 24-hour infiltration depth from a given site soil subgrade, a key design input to determine the subbase thickness. These upgrades will align the program with the 5th Edition of the ICPI PICP Manual and the coming ASCE/ANSI PICP standard. This project will be completed by the end of November 2018.
Status of Existing Projects
Permeable Pavement Road Map Conference – The Foundation funded $15,000 in support of an invitation-only national conference November 14-15, 2017 for 57 stakeholders to develop a road map for permeable pavements. The National Ready-Mix Concrete Association committed $15,000 towards this conference as well as $10,000 from National Asphalt Pavement Association. The final report is available on http://www.ucprc.ucdavis.edu/pdf/UCPRC-RR-2018-01.pdf and provides ways to overcome institutional barriers to wider acceptance. The results of the conference breakout sessions are on www.ucprc.ucdavis.edu/permPvmt.
Wisconsin Department of Natural Resources – The Foundation funded a proposal at $79,918 to provide two-year support of laboratory water quality analyses of outflows from a full-scale PICP using a no-infiltration (impermeable liner) design. This project has received about a half-million dollars of previous investment in construction, monitoring and pollutant analyses over the past several years from individual ICPI members and Foundation contributors. A report on previous monitoring is available on https://pubs.usgs.gov/sir/2018/5037/sir20185037.pdf.
The first year of water quality monitoring is complete and the second year will conclude this winter. A PowerPoint presentation was provided to staff a few months ago on the status of pollutant reductions and surface cleaning results. The pollutant reduction data is surprisingly high and substantiates the benefits of a no-infiltration designs. As an unexpected benefit, the surface infiltration rate is being monitored as well as infiltration before and after various cleaning methods are applied. PICP appears to outshine porous asphalt and pervious concrete in its ability to recover infiltration rates after vacuuming. We expect a final report in the second quarter of 2019. The monitoring will establish performance criteria, enabling wider use in stormwater management and green infrastructure, and specifically in combined sewer overflow reduction.
ICP Road Project Monitoring – The Foundation funded this proposal at $10,000 to Applied Research Associates, Inc. for a three-years of condition surveys and falling weight deflectometer testing of Howard Road, a 1-mile, truck-intensive stretch in Westley, CA. The Stanislaus County Public Works Department will contribute an additional $10,000. Non-destructive structural testing using a falling weight deflectometer will be conducted during the wet (winter) season. The timing of this project is important as the County is considering the use of 3.5 million sf of concrete pavers for roads in an industrial park. The outcome of this study will likely influence the use of concrete pavers on these roads.
Sidewalk Surface Smoothness Evaluation ($22,000 Pathvu) – Pathvu has completed measuring the roughness of 103 ICP and PICP sites in Washington, DC, Pittsburgh and Philadelphia areas. The research demonstrates chamfer sizes and joint widths that meet the (non-mandatory) roughness criteria published by the US Access Board in https://www.access-board.gov/attachments/article/1680/surface-roughness.pdf. A final report is expected in the fourth quarter of 2018. This work is being done in anticipation of mandatory guidance on wheelchair-pavement interaction being published by the U.S. Access Board in the next few years. The data should better position the industry by using the same ASTM test methods for roughness in this study as referenced by the U.S. Access Board.
Landscape Architecture Foundation Performance Series Case Studies ($75,000) – This project includes curation of case studies on performance of projects using ICP and PICP. This was completed last year. See https://landscapeperformance.org/collections/segmental-pavement for an ICPI-curated collection of concrete paver projects published by the LA Foundation. The final deliverable, a learning module on performance of segmental concrete paving was presented as a webinar on February 27, 2018 and is posted on https://landscapeperformance.org/training/segmental-concrete-pavements.
Municipal Interlocking Concrete Pavement Performance Modeling – This project consists of two contracts now initiated for $108,700 with Applied Research Associates, Inc. and another for $22,000 with Pavement Technical Solutions, Inc. Both consultants will model the impacts of interlocking concrete pavement (ICP) within municipal pavement management systems. This will help determine total life performance costs under various maintenance cost scenarios, and comparing them to that for asphalt and concrete. This study should indicate if there is a compelling life-cycle cost case for municipalities to switch from asphalt or concrete pavements to ICP.
The municipal pavement management systems examined will include networks and typical pavement sections from low or medium volume streets in Nashville, Tennessee, Boston, Massachusetts, and Leesburg, Virginia. PTS, Inc. has provided an initial report for roads in Leesburg, Virginia. The results point to the long-term economies of using ICP in major urban roads. Deliverables include PowerPoint presentations for use by ICPI members. ICP cost data has been provided to PTS which they will process and provide by June. Deliverables by the end of the year have been requested from ARA.
Full-scale Load Testing of Paving Slabs and Planks ($35,000 budget plus paving slabs and planks donated by ICPI members) – This is partial validation of selected slab and plank shapes, base materials and thicknesses developed by previous finite element modeling funded by the ICPI Foundation. Loading has begun at Nicolock’s manufacturing facility in Frederick, MD. To date the pavement has been exposed to about 2300 standard axles. The goal is 75,000 to assess paving slab and plank performance, per the finite element modeling. Donated paving units donated from Oaks Concrete Products, Pavestone and Armtec.
PICP Life Cycle Cost Analyses (LCCA), Tools and Training ($85,955 Applied Research Associates, Inc.) – This is a survey of PICP LCCAs, influencing factors, and monetization of PICP lifetime benefits, as well as development of an Excel tool for calculating LCCAs, training materials for ICPI member sales force, and a training workshop. Rather than develop case studies first, an LCCA Excel tool which compares costs of PICP to ICP, asphalt and concrete pavements has been delivered. This is accompanied by a report that provides rationale on accounting for costs not directly related to the PICP. Among several factors, the LCCA accounts for land not used for detention and reduced expenses to process stormwater and sanitary sewage from older combined sewer systems. A webinar was provided on May 29 on the Excel tool.
Developing the Excel tool first enables LCCAs of various PICP case studies. A list of potential PICP projects for LCCA has been provided for review. These are in the process of being converted to case studies with training materials for ICPI commercial sales representatives.
Winter Operational and Maintenance Best Management Practices (BMPs) for Permeable Interlocking Concrete Pavers (Cdn $105,500 - University of Toronto) – Construction of two adjacent PICP test areas is completed at the Toronto and Region Conservation Authority in Vaughan, Ontario. Construction of the test areas was by ICPI member Ross Yantzi’s Pavestone Plus. Oaks Concrete Products donated permeable pavers and Lafarge donated ready-mix concrete and aggregates for the PICP. This project evaluates the effectiveness of different cleaning equipment and winter deicer use compared to conventional pavement. The deicer use study is underway on the PICP and asphalt surfaces this winter to determine the extent to which deicers use can be reduced on PICP. The cleaning study will be conducted in the fall of 2018.
Status of Completed Projects
Paving Slab Structural Design is First in the U.S. and Canada
Segmental Paving Slab Modeling/Structural Analysis – Concrete paving slabs are units that require two or more hands to install. These units are seeing increased use in residential, commercial and municipal applications especially with some exposure to vehicular traffic. Applied Research Associates, Inc. will develop pavement thickness recommendations for paving slabs, thin paving units and paving planks. The recommendations will be developed for various bedding, base and soil types. The project reviewed international research and design literature, and then conducted finite element modeling. Delivery is expected in the fourth quarter of 2015. The charts will be included in an ICPI Tech Spec on paving slabs structural design.
Designer Confidence Raised with Validation of PICP Subbase Thickness Design Charts
Full-scale accelerated load testing at UC Davis developed more cost-effective subbase designs for PICPUniversity of California Davis PICP Full-Scale, Accelerated Load Tests.
The final report is on http://www.ucprc.ucdavis.edu/PDF/UCPRC-RR-2014-04.pdf. The deliverables include PICP subbase thickness design charts that validate those published by ICPI in 2011 based on AASHTO 1993 flexible pavement design method. A benefit of the UC Davis design charts is that they provide thinner and more economical subbases in semi-arid climates since the thicknesses are based on the number days the subbase has water in it. The research report was presented to Caltrans on July 29, 2015 and Caltrans agreed to include the UC Davis design charts in their Pervious Pavements Design Guide. The design charts are also in the draft ASCE PICP national design standard which will likely be completed in 2016. The UC Davis work is being published and presented at various conferences including ASCE, the 2015 International Conference on Concrete Block Paving in Dresden, and at the Transportation Research Board meeting in 2016.
PICP Works in Low-Infiltration Clay Soils
This small PICP in Durham, NC demonstrated PICP’s ability to work in low infiltration clay soils
North Carolina State University PICP Monitoring Research – Multiple studies have shown PICP is an effective tool to improve stormwater runoff hydrology and water quality when sited over high infiltration soils. This project research PICP efficacy over nearly impermeable soils (approximately 0.01 in./hr or 0.254 mm/hr) or in Durham, NC from March 2014 through April 2015. Four parking stalls (540 ft2 or 50 m2) were retrofitted with permeable interlocking concrete pavement (PICP) with a very small contributing impervious area. PICP design followed design guidelines outlined in Chapter 18 of the North Carolina Department of Environment and Natural Resources (NCDENR) BMP manual.
Results through 13 months of monitoring indicated 22% volume reduction via subgrade infiltration and evaporation. Inter-event drawdown of the 150 mm thick subbase created storage to capture over 70% of the runoff volume from storm events less than 0.30 inches, and peak flows were significantly reduced by a median of 84%. The site exhibited exceptional pollutant removal efficiency, with influent and effluent pollutant concentrations significantly reduced for TSS (99%), TN (68%), and TP (96%). The median effluent concentrations of TN (0.52 mg/L) and TP (0.02 mg/L) were below “excellent” ambient water quality thresholds for the North Carolina piedmont regions. The median TSS effluent concentration was also very low (6.99 mg/L) and approaching irreducible concentrations.
Additional sampling of the various nitrogen forms 12, 36, 60, and 84 hours post-rainfall was conducted to better understand mechanisms of nitrogen removal in permeable pavement; results from one storm event indicated denitrification is likely occurring in the internal water storage of the pavement. Significant event mean concentration reductions for the metals Cu (79%), Pb (92%) and Zn (88%) were also observed. Cumulative loading reduction for the watershed was excellent with loading removal efficiencies of 98%, 73% and 95% for TSS, TN, and TP, respectively. These results show permeable pavements built over low-infiltration, clay soils provide considerable improvement of water quality and moderate hydrologic mitigation.
Monitored data were also used to calibrate DRAINMOD, a widely-accepted agricultural drainage model, to predict the cumulative and event-by-event hydrologic performance of the study site. DRAINMOD accurately predicted runoff volumes from the impervious drainage area; NSEs exceeded 0.98 for the prediction of inflow during calibration and validation of the site. Good agreement between predicted and measured drainage was also observed. Cumulative predicted drainage volume was within 6% of what was measured during the monitoring period. These results indicate DRAINMOD can be applied to predict the water balance of permeable pavements built over low-infiltration, clay soils on a long-term, continuous basis.
Supporting Landscape Architects Need for Landscape Performance Instruction at Universities
Landscape Architecture Foundation (LAF) mini-grants to teach landscape performance – Ten university landscape architecture programs were granted money to teach landscape performance, document the syllabus, class/studio assignments, student deliverables and reflections. This project accelerates awareness and practice of evaluating the performance of landscape designs as landscape architecture professional practice is using this approach in selling services and in the design process. These deliverables are posted on the LAF landscape performance website at http://landscapeperformance.org/resources-for-educators. LAF hosted a webinar on these deliverables and recording is available for review. The material includes some performance evaluations of PICP and ICP. Overall, there is a wide range of models used by students to characterize landscape performance by practicing landscape architects, academics and students.
Articulating Landscape Performance of Segmental Concrete Paving Systems
Enhancing the LAF Landscape Performance Series Website with Performance of Segmental Concrete Pavements – A three-year grant supports expansion of this website to include information and instruction on measuring performance of segmental pavements. This includes providing case study ideas, curating case study collections, providing input on social media and blogs, and development of online learning modules for on measuring performance of segmental paving products. Click here to vist the curated case study collections.