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Planned substantial road infrastructure investments emphasize the need for alternative materials that can reduce economic and environmental costs. Alkali-activated materials are one such alternative. These inorganic binders can be produced with fewer CO₂ emissions than asphalt and concrete binders while offering comparable mechanical properties. Alkali-activated materials also develop strength more rapidly, facilitating rapid construction and large-scale repair and maintenance operations.Existing studies suggest that alkali-activated materials would produce fewer CO₂ emissions than conventional cement. However, work to date has not considered availability of the precursors needed to produce alkali-activated materials. Limited availability of raw materials could result in significant additional emissions from transporting materials long distances to market. Researchers at the Georgia Institute of Technology analyzed published life cycle assessment literature to understand whether alkali-activated materials can achieve the same mechanical performance as Portland cement with lower CO₂ emissions, considering the local availability of raw materials. This policy brief summarizes the findings from that analysis and provides policy implications.View the NCST Project Webpage

The capital investment in the U.S. for construction and maintenance of the infrastructure road network is on the order of $100 billion/year. On average, investments in Organization for Economic Cooperation and Development (OECD) countries are likely to stabilize, while China will face an exponential growth of investments for new infrastructures driven by the development of metropolitan cities. Continued “business-as-usual” practice for portland and asphalt cement concrete pavement construction ignores the increasing warning calls for the identification of more sustainable and less energy intensive paving materials. It is therefore important to explore alternative pavement materials, which may have benefits in terms of environmental impact and durability performance over the current technology. Alkali activated materials concrete (AAM) exhibit these beneficial characteristics. AAM compositions have been studied with growing interest during the last three decades, and showing promising results in terms of mechanical performance, while also having a global warming potential impact 30-80% less than that of portland cement concrete. The global warming potential of these material is closely dependent on: 1) the alkali activating solution used to activate the raw material 2) the origin of the raw material. Specifically, the impact of the transport for both of these components has an impact quantifiable around 10% of its global warming potential. Hence, to increase the adoption of AAM for civil applications such as pavements, it is fundamental to analyze the existing literature to clarify the link between environmental and mechanical performance, identifying opportunities for applications that are tailored to the local availability of raw material, reducing transport environmental costs.View the NCST Project Webpage

This report presents the implementation of new design method developed using mechanistic-empirical design approach by University of California Pavement Research Center (UCPRC) through building two test sections at California State University Long Beach (CSULB). The study includes a literature review, pavement design procedure, mix design, construction procedure, instrumentation, and collection of performance data of the permeable asphalt and concrete pavement sections for validation and structural design calibration of the new design approach. Fully permeable pavements are characterized as those in which all layers are porous, and the pavement structure serves as a reservoir to store water and minimize the negative impacts of stormwater spillover. The California Department of Transportation (Caltrans) has shown interest in developing fully permeable pavement design for use in territories that convey substantial truck activity as a potential stormwater management best management practice (BMP) to give low-effect infrastructure and proficient framework operation. A location was selected within CSULB for the construction of the test sections. Pressure cells and strain gages were installed during the construction of pavements for measuring the stress on the top of subgrade on both test sections and the strain at the bottom of surface layer to assess the performance of the fully permeable pavements. In the study, the traffic count was also determined. The data acquisition device CDaq was installed at the site to collect the data. The recorded data was analyzed using the MATLAB program code. The data from pressure cells and strain gages are analyzed, and graphs were plotted to study the pattern in the data sets. The stress and strain measurements and the cracking (both sections) and rutting (asphalt section only) will be used to calibrate the pavement structural design procedure and hydraulic performance will also be monitored.View the NCST Project Webpage

The overall goal of this project was to evaluate with available cores the presence of alkali-silica reaction (ASR) in California bridges and pavements, to develop procedures for evaluation of ASR by Caltrans staff, and, potentially, to investigate several locations suspected of having ASR damage. This report summarizes the creation of an inventory for cores taken from bridges and pavements in previous projects, the results of visual inspection and strength testing to identify the potential presence of ASR, and the development of a draft approach for Caltrans staff to evaluate the potential for ASR in bridges and pavements. A spreadsheet database was prepared for storing inventory data for 265 pavement cores with four inch (100 mm) diameter and 311 bridge cores with two inch (50 mm) diameter. Most of the bridge cores were from the San Francisco Bay Area, while the pavement cores were collected from across the state. Visual inspection was performed on 259 of the pavement cores (including multiple samples from some of the pavement cores) and 80 of the bridge cores (those with lengths greater than the three-inch minimum required for evaluation of ASR) using the Damage Rating Index (DRI) method. None of the cores showed the likelihood of an ASR issue, as defined by a DRI greater than 2,000, although a few cores showed a small number of ASR features. Comparison of the ages of the bridges and the ASR damage rating index for the cores showed almost no trend, and showed no apparent differences between cores from bridges built before and after 1995, approximately when Caltrans changed specifications to reduce the risk of ASR. Most of the pavement cores tested had unconfined compressive strength (UCS) less than 8,700 psi (60 MPa) and the median of the UCS of the pavement cores was approximately 6,100 psi (42 MPa). Most of the pavement cores tested had densities less than 156 pcf (2,500 kg/m3 ) and the median of the UCS of the pavement cores was approximately 147 pcf (2,350 kg/m3 ). No significant correlation was found between the UCS and the density of the pavement cores tested, although the UCS strengths generally increased with increased density. The bridge cores were too small in diameter for strength and density testing. An integrated spreadsheet database was prepared for storing all relevant data for all cores, including test results from all tasks (DRI, UCS, and density). A draft guideline was developed for visual inspection of concrete cores to identify signs of potential ASR-related distresses and to support decisions regarding the need for a further detailed investigation for ASR. The guideline describes step-by-step inspection procedures and selection criteria for a further detailed examination, with relevant example pictures showing different severity levels of potential ASR distresses.

The objectives of the four-year quieter concrete pavement research study presented in this report were to measure noise from tire/pavement interaction, pavement smoothness, and drainability characteristics of concrete pavement surface textures currently used on the California state highway network. This study also was undertaken to develop recommendations for safe, durable, and cost-effective concrete pavement surface textures that minimize noise from tire/pavement interaction. The fourth and final year of this research study included testing on 60 test sections grouped by texture type as follows: 27 diamond ground (DG), 12 diamond grooved (Gr), 19 longitudinally tined (LT), 1 burlap drag (BD), and 1 longitudinally broomed (LB). Five of the 60 test sections were continuously reinforced concrete pavement (CRCP) and the rest were jointed plain concrete pavement (JPCP). This report presents the results of measurements of tire/pavement interaction noise and of the pavement smoothness and surface drainability characteristics of concrete pavement textures commonly used for new construction finishes or pavement preservation and rehabilitation strategies. Tire/pavement interaction noise was measured using the on-board sound intensity (OBSI) method; smoothness was measured in terms of the International Roughness Index (IRI) using a wide-spot (RoLineTM) laser; pavement surface drainability was measured using outflow meter measurements as well as in terms of Mean Profile Depth (MPD) and Mean Texture Depth (MTD). The results indicate that the OBSI levels for the concrete pavement sections evaluated in this study ranged from 100 dBA to 112 dBA, which is the same as the range of OBSI levels for concrete pavement textures measured in other similar studies. The average OBSI levels for the three commonly used texture types in California (DG, Gr, and LT) where the textures were not worn out ranged from 104 to 107 dBA, with DG and Gr sections typically being quieter than LT sections of similar age and texture condition. For comparison, the OBSI levels for the experimental grind-and-groove sections averaged 101 dBA. The average IRI values for the DG, Gr, and LT sections across all three texture conditions (new, aged, or worn out) were 68, 81, and 96 inches/mile, respectively. The results for the outflow meter times and the MPD values indicate that diamond-grooved sections had a greater capacity for allowing water to move out from under the tire. This suggests that diamond-grooved concrete pavements would generally be more effective in reducing the risk of hydroplaning than diamond-ground or longitudinally tined concrete pavements.

This research report presents the results of tire/pavement noise, friction, drainability, and profile measurements performed on conventional diamond grind (CDG) and grind and groove (GnG) concrete pavement surface textures as a part of the California Department of Transportation (Caltrans) Quieter Pavement Research (QPR) study to investigate tire/pavement noise on concrete pavements. The On-board Sound Intensity (OBSI) method (AASHTO TP 76) was used to measure tire/pavement noise. Longitudinal profile data were collected at the same time as the OBSI data using an inertial profiler (ASTM E950) and were used to calculate the International Roughness Index (IRI). Friction was measured using the Towed Skid Trailer (ASTM E274) and the California Portable Skid Tester (CT 342), and estimated using the Circular Track Meter (ASTM E2157) and Dynamic Friction Tester (ASTM E1911). Drainability was measured using the Outflow Meter (ASTM E2380). Seven pilot projects scheduled for CDG were selected for this research study. They include one each in San Diego, San Joaquin, and Yolo counties, and four in Sacramento County. At these seven sites, measurements were made before and after construction, and in between construction phases when possible. The GnG surface texture was found to be quieter than the CDG, with lane average OBSI values on the GnG texture ranging from 99.5 dBA to 101.7 dBA, with an average of 100.8 dBA, compared with a range of 100.6 dBA to 104.7 dBA, and an average of 102.8 dBA measured on the CDG surface texture. The average OBSI level for all GnG sections was 100.8 dBA compared with an average of 102.8 for all CDG sections. OBSI values on the CDG texture on the San Diego 5 project decreased by 0.5 dBA over 1.3 years where OBSI was measured several times after initial construction. This reduction was attributed to flattening of the “fins” produced by CDG during construction. The average OBSI for all sections prior to treatment was 104.4 dBA, although not all sections had measurements of both CDG and GnG. The IRI measurements showed that both CDG and GnG texturing treatments improved smoothness substantially compared with the pretreatment values. The average IRI was reduced from 142 in./mi for the preconstruction surface textures to 64 in./mi on average after the CDG treatment and to 49 in./mi on average after the GnG texture treatment. Both the OBSI and IRI are improved by CDG and even more so by the GnG texturing. Both CDG and GnG remove sealant overbanding and reduce or eliminate faulting at joints and cracks. Both processes also remove imperfections in the slabs caused by curling, warping, and most of whatever roughness was introduced during initial construction. All of these changes that result from CDG and GnG are likely to contribute to reductions in both noise and roughness. In this study, however, the individual contributions of removal of faulting and overbanding to noise and roughness reductions were not measured. The few friction measurements on the GnG texture using CT 342 were not sufficient to draw conclusions, indicating that further attention should be given to use of this test on this texture if Caltrans continues to use the test. The skid tests using ASTM E 274 indicated that both the CDG and GnG textures passed specifications used by most state highway departments.

This research report presents the results of tire/pavement noise measurements performed on concrete pavements as a part of the California Department of Transportation (Caltrans) Quieter Pavement Research (QPR) study to investigate tire/pavement noise characteristics on concrete pavements. The On-board Sound Intensity (OBSI) method was used to measure tire/pavement noise. In this third year of the study, a total of 83 pavement sections were tested at 35 different sites, which was reduced from the original 120 sections in the experiment for various reasons. Twenty-four of the 35 sites were divided into three test sections each, while the remaining eleven sites had one test section each that were used for analyses shown in this report. The third-year test sections were comprised of five texture types, with the following distribution of sections used in the analyses: 31 burlap drag, 23 diamond ground, 7 diamond grooved, 4 longitudinally broomed, and 18 longitudinally tined. At this time no single concrete pavement texture type can be considered definitively quieter than the others. Each pavement type has a demonstrated range of noise levels that largely overlap. The difference between the lowest and highest OBSI levels for the same nominal texture type is up to 6 dBA, indicating a large variability within a given texture type when sampled over a wide range of ages. The contributions of joint width, faulting, and sealant overbanding to this variance have not been rigorously investigated, and the results to date include these effects, which are part of the total noise generated by concrete pavements in the state. Taking into account all sections, the OBSI level on existing concrete pavements in California varies from about 101.1 dBA to about 107.6 dBA. The ranking of texture types for the sections with new and aged textures evaluated in this research project from quietest to loudest is: longitudinally broomed, burlap drag, diamond ground, diamond grooved, and longitudinally tined, although the differences between the means of each of these textures is not statistically significant, except for the longitudinally broomed sections. The report includes results from the Mojave test sections on Kern 58 which were all constructed at the same time in 2003. Based on these observations and the conclusions to date, recommendations are made for the fourth and final year of large-scale data collection and analysis on concrete pavement noise to change the experiment to focus on the following textures: diamond ground, diamond grooved and longitudinally tined. Recommendations are also made to obtain more detailed data regarding texture characteristics, joint cross-sectional area, faulting, and sealant overbanding to try and better explain differences within each texture type.

This report provides a critical review of existing literature and modeling tools related to life-cycle assessment (LCA) applied to pavements. The review finds that pavement LCA is an expanding but still limited research topic in the literature, and that the existing body of work exhibits methodological deficiencies and incompatibilities that serve as barriers to the widespread utilization of LCA by pavement engineers and policy makers. This review identifies five key issues in the current body of work: inconsistent functional units, improper system boundaries, imbalanced data for asphalt and cement, use of limited inventory and impact assessment categories, and poor overall utility. This review also identifies common data and modeling gaps in pavement LCAs that should be addressed in future work. These gaps include: the use phase (rolling resistance, albedo, carbonation, lighting, leachate, and tire wear and emissions), asphalt fumes, feedstock energy of bitumen, traffic delay, the maintenance phase, and the end-of-life phase. This review concludes with a comprehensive list of recommendations for future research, which shed light on where improvements in knowledge can be made that will benefit the accuracy and comprehensiveness of pavement LCAs moving forward.