Stormwater-Pavement Interface in Cold Climates

This project relates to “managing stormwater runoff in cold climates” and addresses the feasibility of low-impact development at a regional demonstration site in eastern Washington. The studies relate to seven large permeable pavement systems. The findings for similar climates and soils are as follows: The draindown times for retention in Palouse or similar clay soils may handle many typical storms. On average, every square foot of a permeable pavement system installed also receives run-on from another square foot of impermeable pavement, doubling its impact on both stormwater quantity reduction and stormwater quality improvement. Most of the clogged sections on various applications were downslope of other areas. Permeable pavements installed in areas targeted for additional stormwater quantity control and quality improvement may be feasible. On average, the cleaning for installations is less frequent than annually. Power washing plus vacuuming appears to be an effective method for pervious concrete. Surface distress was usually where vehicles turned, or from placement activities. Preliminary studies on various surface treatments on pervious concrete show promise for added safety benefits under wintry conditions. Both detention-type and retention-type permeable pavement systems appear to have little negative impact on neighboring soils in the winter under the study conditions. However, further research is needed for different designs of retention-type systems to ensure that water volumes in the aggregate storage bed do not allow for sufficient water flow into neighboring soils that might result in ice lens formation or other negative impacts

Prediction of Thermal Behavior of Pervious Concrete Pavements in Winter

Because application of pervious concrete pavement (PCPs) has extended to cold-climate regions of the United States, the safety and mobility of PCP installations during the winter season need to be maintained. Timely application of salt, anti-icing, and deicing agents for ice/snow control is most effective in providing sufficient surface friction when done at a suitable pavement surface temperature. The aim of this project was to determine the thermal properties of PCP during the winter season, and to develop a theoretical model to predict PCP surface temperature. The project included a laboratory and a field component. In the laboratory, thermal conductivity of pervious concrete was determined. A linear relationship was established between thermal conductivity and porosity for pervious concrete specimens. In the field, the pavement temperature in a PCP sidewalk installation at Washington State University was monitored via in-pavement instrumentation. Based on the field data, the Enhanced Integrated Climatic Model (EICM) was developed and validated for the site, using PCP thermal properties and local climatic data. The EICM-predicted PCP surface temperature during the winter season agreed well with the field temperature. Overall, the predicted number of days that the pavement surface fell below 32°F agreed well with the number based on field data for 85% of the days. Therefore, the developed model is useful in identifying those days to apply deicer agents. Finally, a regression model using climatic indices was developed for PCP surface temperature prediction in the absence of a more advanced temperature model

Establishing Permanent Curl/Warp Temperature Gradient in Jointed Plain Concrete Pavements

The concrete slab in a pavement structure curls due to a temperature gradient and warps in the presence of a drying shrinkage gradient. The curling is upward (downward) when the slab is cooler (warmer) at the top than the bottom. Warping is consistently upward because the slab is more susceptive to drying at the top. Since the slab is not free to curl, tensile stresses form in the slab. These stresses when combined with traffic loadings can result in cracking of the slab. Slabs do not remain flat in the absence of daily gradients. This is because of the temperature/moisture gradient that exists in the slab at zero-stress time. Zero-stress time occurs after the placement of the slab, during curing and following the final set time. These gradients, known as built-in or permanent curl temperature gradients, lock into the slab and either decrease or increase the curling due to the transient gradients. One more factor that influences the future shape of the slab is the permanent warp temperature gradient. A portion of the drying shrinkage in drier seasons can reverse in wet seasons, known as reversible drying shrinkage. Permanent warp is due to the irreversible portion of the drying shrinkage, which progressively increases as the concrete ages and eventually reaches a plateau. This study puts forward a procedure, including three tasks, to establish realistic values for permanent curl/warp in the slab. Task 1 includes identifying the zero-stress time in the slab. This is performed by using the data from four different instrumented pavement structures in Western Pennsylvania. Task 2 focuses on establishing the built-in temperature gradient based on the measured temperature. As part of this task, a computer temperature model is developed to predict the temperature within the pavement based on the ambient conditions and the heat of hydration. Task 3 focuses on estimating the permanent warp in the slab. This is achieved by using long-term strain measurements in two different test sections in Pennsylvania and Minnesota. The drying shrinkage development is also predicted by using a computer relative humidity model. The difference between the predicted and measured drying shrinkage is attributed to the effects of creep and base restraints

Recycled Glass Fiber Reinforced Polymer Composites Incorporated in Mortar for Improved Mechanical Performance

Glass fiber reinforced polymer (GFRP) recycled from retired wind turbines was implemented in mortar as a volumetric replacement of sand during the two phases of this study. In Phase I, the mechanically refined GFRP particle sizes were sieved for four size groups to find the optimum size. In Phase II, the select GFRP size group was incorporated at three different volumetric replacements of sand to identify the optimum replacement content. The mixtures were tested for compressive strength, flexural strength, toughness, and the potential for alkali-silicate reaction. Incorporation of GFRP in mortar proves promising in improving flexural strength and toughness in fiber-like shapes and 1–3% volumetric fractions

A Solitary Wave-Based Sensor to Monitor the Setting of Fresh Concrete

We present a proof-of-principle study about the use of a sensor for the nondestructive monitoring of strength development in hydrating concrete. The nondestructive evaluation technique is based on the propagation of highly nonlinear solitary waves (HNSWs), which are non-dispersive mechanical waves that can form and travel in highly nonlinear systems, such as one-dimensional particle chains. A built-in transducer is adopted to excite and detect the HNSWs. The waves are partially reflected at the transducer/concrete interface and partially transmitted into the concrete. The time-of-flight and the amplitude of the waves reflected at the interface are measured and analyzed with respect to the hydration time, and correlated to the initial and final set times established by the penetration test (ASTM C 403). The results show that certain features of the HNSWs change as the concrete curing progresses indicating that it has the potential of being an efficient, cost-effective tool for monitoring strengths/stiffness development

Identification of Likely Alternative Supplementary Cementitious Materials in California: A Review of Supplies, Technical Performance in Concrete, Economic, and Climatic Considerations

This report is a comprehensive review of natural and human-made materials with the potential to reduce cement content in concrete by partially replacing portland cement or as additives. The review aims to reveal possible source materials as alternative supplementary cementitious materials (ASCMs) to coal-burned fly ash and ground granulated blast furnace slag as these SCMs supplies rapidly decline. Information required to estimate supplies of each ASCM was gathered, and ASCM candidates with enough abundance to support California’s concrete paving sector were identified for further laboratory evaluation. In addition, the required chemical, thermal, and mechanical treatments of the source materials were gathered so the environmental and economic impacts of the processes could be considered. A review of scientific literature on the technical performance of the studied materials in cement paste, mortar, or concrete was also conducted when that information was available.The reviewed feedstock material categories include biomass sources, construction and demolition wastes, natural pozzolans (volcanic and sedimentary materials), and post-consumer waste. As part of the biomass category, biopolymer-based nanomaterials were also included in the review for their promise to reduce cement content from added strength. The following information was included for each material considered in this report: feedstock description, the potential mechanism of performance in concrete, physical and chemical properties, feedstock supplies and processing method, technology readiness level (TRL), a summary of technical performance in cementitious systems based on the scientific literature, environmental impacts of the production phase, and cost considerations.Based on the comprehensive information gathered, several materials present potential as ASCMs, fillers, and admixtures for the California paving industry. However, most materials identified are at TRL 3 or 4, requiring more research and development to move toward implementation. In addition, some of these ASCMs may not fully satisfy the current regulations for SCMs. For example, biomass ash from some sources may contain a high alkaline content and a greater than 6% unburnt carbon content. Furthermore, some natural pozzolans impose a high water demand and have slow strength gain. In addition, the reported performance in the literature for the biobased nanomaterials studied is conflicting and performance data in concrete is scarce. Finally, some reviewed materials were not selected for more advanced laboratory evaluation because a supplier was not found in California. These materials include municipal solid waste ash, wastewater treatment sludge, and seashell waste. In addition, ground glass, harvested coal-burnt fly ash, and fines from carpet recycling were not chosen for laboratory evaluation because they are being investigated in other Caltrans and non-Caltrans research contracts

DEVELOPMENT OF PROTOCOL TO MAINTAIN WINTER MOBILITY OF DIFFERENT CLASSES OF PERVIOUS CONCRETE PAVEMENT BASED ON POROSITY

The main focus of this study was to develop an image-based method to characterize the porosity of in-situ pervious concrete (PC), so this feature can be correlated with ice formation and winter maintenance operations of the pavement. First, a surface imaging-based porosity characterization method was investigated. A total of 27 PC slabs cast at three targeted porosity levels—15 percent, 25 percent, and 35 percent--were used. Images of the top and bottom surfaces of the slabs were used in thresholding techniques, in which the images were binarized and the area of the voids were obtained. The image-based porosity was calculated as the ratio of the area of voids to the total surface area of each slab. The image-based porosity was correlated with the porosity of the PC measured in accordance with ASTM C1754 by submersion. For validation, the distribution of the porosity along the depth of PC cores extracted from the slabs was quantified from images taken by X-ray computed tomography (CT). Analysis of these images revealed that the distribution of pores along the depth were significantly different at intermediate depths than that at the top and bottom 0.5-inch depths because of compaction. Therefore, the developed surface image-based method did not provide a representative porosity value for the full PC layer. More surface imaging, in parallel with X-ray CT scans, are required to develop a correlation between the porosity of the surface layer and overall porosity. Finally, the Gibbs-Thompson equation, a thermodynamic-based model developed in past studies, was recommended to determine the critical temperature at which ice formation initiates inside PC pores. The proposed image-based porosity characterization method and the Gibbs-Thompson equation can be used as a decision support tool for transportation authorities to identify the time of ice formation in PC pavements in order to apply timely winter maintenance treatments.Pacific Northwest Transportation Consortium US Department of Transportatio

Evaluation of Motorcyclists' and Bikers' Safety on Wet Pavement Markings

In this study, three different pavement marking material types were evaluated by using a British Pendulum Tester (BPT) in dry, wet, and icy conditions. The frictional properties were recorded as a British Pendulum Number (BPN). Two different rubber sliders on the BPN were used to compare different pavement marking users: a pedestrian slip rubber (PSR) and tire slip rubber (TSR). This study included both laboratory and field testing. The pavement markings evaluated were chosen after a careful review of Washington State Department of Transportation’s specifications and Washington State University’s (WSU) Facilities Services common practices. During laboratory testing, a neat concrete slab surface was compared to waterborne paint, preformed fused thermoplastic, and cold applied pre-formed tape surfaces. Each of the surface types was evaluated under dry, wet, and icy conditions. Laboratory test results showed that the paint and thermoplastics resulted in lower BPN values than the neat concrete surface. However, the centerline striping that was tested did show higher frictional properties than the neat concrete surface because of the contours and surface macrotexture of the tested striping. During field testing, two locations on the WSU Pullman campus were chosen for testing in dry and wet conditions. Each location was evaluated by using the BPT, and then two bicyclists rode over the markings in a variety of ways in dry and wet conditions. The tested locations were painted markings. A safety scale was created for riders to evaluate the field markings. The results showed that riders generally felt safe while riding in a straight line over the pavement markings. Most of the unsafe ratings occurred during wet testing, and as cyclists turned and braked over the pavement markings. In comparing the laboratory and field testing BPN values, the laboratory values were typically higher. This was most likely due to the fact that beads were present on the laboratory markings and not on the field markings. From these results, the authors concluded that centerline striping showed the most promising frictional properties. Although paint and thermoplastics showed lower frictional properties than those of the neat concrete surface, the use of beads helped improve the laboratory values over the field testing values.Pacific Northwest Transportation Consortiu

Smart and Environmentally Friendly Winter Maintenance Solutions for Safe Winter Mobility: Use of a Microwave Method to Prototype Electrically Conductive Concrete

Electrically conductive pavement materials have shown potential as self-deicing pavements under passed electrical current. In this project, a method using microwaves was used to evaluate the electrical conductivity of pavement materials for the purpose of melting snow and ice and reducing the need for sanding and salting in the winter. The preliminary experiments in this study found the potential of the method to detect conductive mixes. The prototyped electrically conductive concrete (ECC) assessed in this study contained 0.2 and 0.3 percent weight of carbon fibers. Concentrations of 0.2 and 0.3 percentage by weight (wt%) resulted in more conductivity than a neat mix, while a decline in conductivity at 28 days was obtained for 0.4 wt%,indicating a potential percolation limit of between 0.3 and 0.4 wt%. The small samples and the quick, nondestructive method of measurement can be used to easily identify the optimum dosage and percolation limits of various conductive fibers for ECC development. Future investigations may include using this method to further determine the best fiber content to optimize electrical-thermal performance with maximum mechanical properties and durability.US Department of Transportation Pacific Northwest Transportation Consortium Washington State Universit

Guidelines for Pervious Concrete Sidewalks, Parking Lots, and Shared-Use Paths to Improve Driver, Biker, and Pedestrian Safety

The surface frictional properties of pervious concrete (PC) slabs were evaluated by using a British Pendulum Tester (BPT) with two different rubber sliders that represented driver and pedestrian users. The volumetric air content at the finished surface of the slabs was quantified by image analysis to identify any possible correlations between the different surface finishes due to varied porosity and the microtexture of the PC slabs. Frictional evaluation for all the PC slabs was compared with that of traditional portland cement concrete (PCC) slabs under three baseline conditions: dry, wet, and iced. The iced condition was then treated with magnesium and calcium chloride (MgCl2 and CaCl2), used once as anti-icing and again as de-icing agents, and then individually tested by using the BPT. Friction values were recorded as the British Pendulum Number (BPN). Minimal correlation was found in this study between porosity and BPN. The PC slabs showed significantly higher BPN values than the PCC slabs in each of the baseline conditions for the mixture tested in this study. For one icing event, the one-time application of anti- and de-icing agents on PC slabs improved the friction of the PC slabs to the allowable BPN level using both MgCl2 and CaCl2.Pacific Northwest Transportation Consortiu