Vernon R. Schaefer

Pervious Concrete Mixture Proportions for Improved Freeze-Thaw Durability

Recent stormwater management regulations from the Environmental Protection Agency (EPA) and greater emphasis on sustainable development has increased interest in pervious pavement as a method for reducing stormwater runoff and improving stormwater quality. Pervious concrete is one of several pervious pavement systems that can be used to reduce stormwater runoff and treat stormwater on site. Pervious concrete systems have been used and are being proposed for all parts of the United States, including northern climates where severe freezing and thawing can occur. The purpose of the research is to develop pervious concrete mixtures that have sufficient porosity for stormwater infiltration along with desirable porosity, strength, and freeze-thaw durability. In this research, concrete mixtures were developed with single-sized river gravel aggregate (4.75 mm) and constant binder contents, together with high range water reducer. River sand was used as a replacement for up to 7 % coarse aggregate. Two different types of polypropylene fibers (a shorter fibrillated variable-length and a longer fibrillated single-length) were incorporated at several addition rates from 0 to 0.1 % by volume of concrete. The engineering properties of the aggregate were evaluated along with the porosity, permeability, strength, and freeze-thaw durability of selected concrete mixtures. The results indicate that the use of sand and fibers provided beneficial effects on pervious concrete properties, including increased strength, maintained or improved permeability, and enhanced freeze-thaw resistance.

Effect of Coarse Aggregate on the Freeze-Thaw Durability of Pervious Concrete

Pervious concrete is becoming more common as a storm-water management tool in freeze-thaw climates. One of the main concerns or obstacles preventing a more widespread application is the aspect of freeze-thaw durability, whether perceived or actual. This paper describes a series of tests designed to determine the specific role coarse aggregate has on the freeze-thaw durability of pervious concrete using the ASTM C666A procedure. 17 different coarse aggregate samples were obtained from locations across the United States and Canada. Pervious concrete mixtures were placed using a mixture proportion previously determined as freeze-thaw durable. The range of durable aggregate gradations clearly defined a gradation specification and suggestions are made for optimizing the gradation with a small portion of sand. Mixtures with excellent freeze-thaw performance contained either granite or highly durable river gravel. The impact of aggregate angularity on mixture proportions and ultimate yield is also discussed.

Cyclic Heat Island Impacts on Traditional Versus Pervious Concrete Pavement Systems

As the world becomes more urbanized, concerns over the urban heat island (UHI) are more pronounced. Increased urban temperatures have a negative affect on the natural and human environment by producing increased energy usage and smog formation. Pervious concrete pavement is one technology that may help mitigate increased urban temperatures. Temperature data from an instrumented site in Iowa and heat storage phenomena for various weather patterns are presented. The site contains both pervious concrete pavement with a solar reflectance index (SRI) of 14 and traditional concrete pavement with an SRI of 37. Leadership in Energy and Environmental Design (LEED) accepted a high SRI (>29) as one method to characterize a cool surface. Heat capacities of both systems were studied along with a sensitivity analysis of the inputs. The research supports the conclusion that even though pervious concrete may have a much lower SRI than traditional concrete made with similar materials, it can be considered a cool pavement option. In addition, daytime rainfalls combined with the internal high surface area result in significantly more removal of stored heat from the system, with a more rapid mitigation of UHI impacts and reduction in the potential for thermal shock from impervious surface runoff.

Temperature Behavior of Pervious Concrete Systems

To achieve the permitted stormwater effluent limits required by the Clean Water Act, many best management practices (BMPs) are being utilized to reduce the overall stormwater volume and provide initial pretreatment and pollutant removal. One such BMP is use of portland cement pervious concrete (PCPC), which allows stormwater to pass through the pavement into an aggregate base below to infiltrate. Until now, the temperature response of the entire system (concrete, aggregate base, and natural soil) was not known. Since PCPC is an infiltration-based BMP, once a frost line forms under the base the infiltrating capacity is reduced or eliminated. PCPC also is recommended for use in warmer climates as a cooler pavement alternative to conventional concrete or asphalt. To quantify the temperature behavior of a pervious concrete system, a fully monitored parking lot—composed of half traditional concrete and half PCPC—was constructed at Iowa State University as part of the Iowa Pervious Concrete Stormwater Project. Sensors were installed through the profile of both pavements and into the underlying soil. The results show that insulation from the aggregate base underneath the pervious concrete substantially delays the formation of a frost layer and permeability is restored when meltwater is present. It was also observed that in direct sunlight, the pervious pavement became hotter than traditional concrete, whereas the daily low temperature of the two was similar, indicating less heat storage capacity in the pervious concrete.

Real-Time Compaction Monitoring in Cohesive Soils from Machine Response

Recent developments for measurement and analysis of machine power response caused by changes in physical soil properties have the potential to change completely the future of earthwork construction. A technique in which a self-propelled sheepsfoot roller was used to compact cohesive soils was developed; field pilot studies were then conducted. Results from field tests using conventional testing techniques (nuclear moisture–density gauge, dynamic cone penetrometer, drive core, and Clegg impact hammer) showed strong correlations to machine power (r2 > 0.9) when data were averaged over a 20-m test strip. These developments related to measurement and analysis of machine energy as a function of changes in physical soil properties and provide the benefit of 100% coverage combined with a differential Global Positioning System and ruggidized touchscreen computer monitor showing spatial information on cumulative number of passes and machine power output. Results can be transmitted in real time to an on-site computer for review via a wireless Internet system.

The Effect of Curing Regime on Pervious Concrete Abrasion Resistance

The current method of curing pervious concrete is to cover with plastic for 7 days, although no studies have been performed to determine if that is sufficient or even required. This paper presents results of combinations of four different pervious concrete mixtures cured using six common curing methods. The surface abrasion of the concrete was tested using a rotary cutter device according to ASTM C944. The results show that the concrete abrasion resistance was improved with a majority surface-applied curing compounds; however the surfaces covered with plastic sheets produced the lowest abrasion levels. A majority of the curing regimes also produced higher flexural strength than the control concrete. There was no significant difference observed in the strength between curing under plastic sheets for 7 or 28 days. Of the surface-applied curing compounds, the best abrasion resistance and highest strength concrete was that applied with soybean oil. The best abrasion resistance and highest strength overall was the mixture containing fly ash and cured under plastic for 28 days.

Mixture Proportion Development and Performance Evaluation of Pervious Concrete for Overlay Applications

The results of studies to develop pervious concrete for use as an overlay material over traditional concrete to reduce noise, minimize splash and spray, and improve friction as a surface wearing course are described in this paper. Workability and compaction density testing methods were developed in order to ensure constructability and placement consistency. The mixture testing matrix consisted of evaluating aggregate type and gradation, cementitious material amounts and composition, and various admixtures. Selected mixtures were tested for permeability, strength, workability, overlay bond strength, and freezing-and-thawing durability. The selected mixture was self-consolidating and slip-formable and was placed at the MnROAD testing facility during late October 2008. The test results indicate that pervious concrete mixtures can be designed to be highly workable, sufficiently strong, permeable, and have excellent freezing-and-thawing durability, thus being suitable for pavement overlays.

Construction and Performance of Pervious Concrete Overlay at Minnesota Road Research Project

Portland cement pervious concrete (PCPC) has shown great potential to reduce roadway noise, improve splash and spray, and improve friction as a surface wearing course. A study is under way at Iowa State University and the National Concrete Pavement Technology Center to develop mix designs and procedures for PCPC overlays for highway applications. A report is produced on the construction and performance of a PCPC overlay constructed at the Minnesota Road Research Project low-volume roadway test facility to determine the effectiveness of pervious concrete as an overlay. Issues related to construction of the overlay are described, as are results of field tests to characterize the condition of the pavement 7 months following construction, to determine flow characteristics of the overlay, and to characterize the tire–pavement noise of the overlay. Results of these studies show that effective PCPC overlays can be designed for wearing course applications.

Part 4: Geotechnical Engineering: Compaction, Nontraditional Computing Methods, and Other Issues: Real-Time Compaction Monitoring in Cohesive Soils from Machine Response

Recent developments for measurement and analysis of machine power response caused by changes in physical soil properties have the potential to change completely the future of earthwork construction. A technique in which a self-propelled sheepsfoot roller was used to compact cohesive soils was developed; field pilot studies were then conducted. Results from field tests using conventional testing techniques (nuclear moisture-density gauge, dynamic conepenetrometer, drive core, and Clegg impact hammer) showed strong correlations to machine power (r2 > 0.9) when data were averaged over a 20-m test strip. These developments related to measurement and analysis of machine energy as a function of changes in physical soil properties and provide the benefit of 100% coverage combined with a differential Global Positioning System and ruggidized touchscreen computer monitor showing spatial information on cumulative number of passes and machine power output. Results can be transmitted in real time to an on-site compute...

Resistance of Portland Cement Pervious Concrete to Deicing Chemicals

The damaging impact of deicing chemicals on portland cement pervious concrete materials was investigated. Two concrete mixes (with and without latex modification) were subjected to three deicing chemicals (sodium chloride, calcium chloride, and calcium-magnesium acetate) under a freezing–thawing or drying–wetting condition. Two deicing chemical application methods (saturated and drained) were employed. The impact of deicing chemicals on the concrete was evaluated based on concrete mass and strength losses. Of the deicing chemicals studied, the calcium chloride solution caused the most damage, while the calcium magnesium acetate caused the least. The saturated scaling test method, followed according to ASTM C672, provided much higher mass loss of tested concrete samples when compared with a modified, more realistic drained test method.