Somayeh Nassiri

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.

Evaluation of the effects of Canadian climate conditions on the MEPDG predictions for flexible pavement performance

This study aims to investigate the quality of the recently developed Canadian climatic database and the effect of climatic factors on flexible pavement performance using the mechanistic-empirical pavement design guide (MEPDG). Two hundred and six Canadian climatic files were used to carry out the analysis. Freezing index and frost depth from the MEPDG were compared with the data available in Canadian databases. The sensitivity of pavement performance to climate conditions, predicted using the MEPDG, was also studied. The pavement performance predicted using the virtual weather station and existing weather station data was compared. From the pavement performance sensitivity study, it was found that the asphalt concrete, total pavement rutting and international roughness index show sensitivity to climate changes. It was also found that differences in the quality and duration of data for close-by stations can result in variation in the predicted performance. Overall, the study assists with facilitating the implementation of the MEPDG in Canada.

Evaluating the continuously reinforced concrete pavement performance models of the mechanistic-empirical pavement design guide

The reasonableness of the models in the Mechanistic-empirical Pavement Design Guide (MEPDG) used to predict the performance of the continuously reinforced concrete pavements (CRCPs) was evaluated in this study. The MEPDG punchout, crack width and spacing and load transfer efficiency (LTE) models were evaluated through a factorial sensitivity study. The input matrix was defined to reflect ‘real-world’ design situations. It was found that, contrary to the 1993 American Association of State Highways and Transportation Officials (AASHTO) Design Guide, crack width must be below 0.5 mm to maintain adequate performance. Additionally, based on the performance predictions from the MEPDG, a crack spacing of less than 1.8 m ensures a crack width of less than 0.5 mm, which is another contradiction with the approach in the 1993 Guide.

Investigation of tire derived aggregate as a fill material for highway embankment

Abstract This study investigates the compression behavior and performance of tire derived aggregate (TDA) used to construct an 80-m long embankment for a highway test road in Edmonton, AB, Canada. The road contained four test sections made from passenger and light truck tires (PLTT), off-the-road (OTR) truck tires, TDA–soil mixture, and native soil. A total of 30 temperature probes and 25 settlement plates were embedded into the road to monitor the embankment. Falling Weight Deflectometer (FWD) test was also conducted under different load levels to determine the embankment material’s deflection behavior after the placement of the soil cover. Through observation, field data, and FWD testing, it was determined that PLTT is more compressible than OTR and the TDA–soil mixture, and TDA–soil mix section showed equivalent performance with the control section. Additionally, all the temperature probes revealed no internal heating during the 8-month monitoring period.

Using Field Data to Evaluate Bottom Ash as Pavement Insulation Layer

A common problem in cold regions is the penetration of frost into susceptible subgrade soils. This study investigated the application of bottom ash in comparison with polystyrene boards as an insulation layer at a test road in Edmonton, Alberta, Canada. The adjacent normal section was used as the control section. All sections were instrumented at various depths to monitor temperature variation. On the basis of temperature measurements in the base and subgrade layers from October 2012 to June 2013, frost depth and freezing and thawing periods were analyzed for each section. R-values for thermal resistivity were calculated for each layer, considering its thickness and thermal properties, and were used for justifying and comparing the temperature trends. R-values were established at 1.4 and 16.7 m2 • °C/W for the bottom ash and polystyrene board, respectively. The base layer in the polystyrene section experienced higher temperatures in the summer and lower temperatures in the winter in relation to the bottom ash and control sections. On the basis of temperature measurements at depths of 1.61 to 3.27 m, the subgrade in the polystyrene section showed the lowest variation in temperature with respect to time and depth, followed by the bottom ash and then the control section. This behavior indicated that the insulation layers obstructed the heat transfer between the surface and the lower layers. The use of polystyrene boards and bottom ash as insulation materials decreased the frost depth by at least 40% and 28%, respectively, compared with the control section.

Survey of Practice and Literature Review on Municipal Road Winter Maintenance in Canada

AbstractEfficiency of winter operations is essential for cities in cold regions because fiscal budgets are limited and excessive amounts of street sand and salt can negatively impact the environment. A review of winter maintenance policies in major Canadian cities has shown that freeways, business areas, and routes to transit and emergency venues are treated as priority. On these routes, snow is piled on the roadsides until it narrows the road width and decreases drivers’ visibility. At such time, the snow piles are hauled to specific snow storage or eliminator locations. In cities with relatively warmer climatic conditions, such as Ottawa, Toronto, and Montreal, high amounts of street salt are used annually. In cities with extremely cold winters, such as Edmonton, Calgary, and Winnipeg, Canada, sanding is more common. Friction measurement devices, which have been developed in a number of diverse models, can provide data to compare and improve winter maintenance operations. Road friction measuring devices...

Highly nonlinear solitary waves-based sensor for monitoring concrete

This paper describes the application of a novel actuator/sensor technology for monitoring concrete at early age. A device is designed to generate and detect highly nonlinear solitary waves (HNSWs) in a chain of steel beads. Two experiments were conducted. In the first experiment, the propagation of the HNSWs in the chain was recorded. In particular, the reflections at the interface between the chain and a composite layer consisting of a thin aluminum plate and the concrete were observed. It was found that the travelling time of HNSWs of the reflected pulses depend on the boundary conditions of the chain, so it changes as the stiffness and strength of concrete develop during the hydration process. In the second experiment, a similar actuator was used to transmit mechanical waves inside concrete. These waves were then detected by an embedded commercial transducer. The change of frequency components of the stress waves in the fresh concrete was monitored and used to interpret the initial set of the concrete. The results of these two experiments were compared to outcomes of the penetration resistance test (ASTM C403) conventionally used to determine the time of setting. We found that the proposed nondestructive evaluation method can be used in fresh concrete although more tests are needed to prove repeatability under various concrete mixtures.

Enhancing Mechanical Properties of Pervious Concrete Using Carbon Fiber Composite Reinforcement

AbstractCured carbon fiber composite material (CCFCM) is available from manufacturing lines; however, excess CCFCM has no reuse applications at present. Postindustrial CCFCM was mechanically refine...

Comparison of response for three different composite pavement sections to environmental loads

Abstract Composite pavement structures are constructed mainly either as Portland cement concrete (PCC)-over-PCC or hot mix asphalt (HMA)-over-PCC. Several successful in-service projects have been reported in Europe. The design and construction of these sections in the United States, however, still require effort. The current study includes the analysis of the response of three different composite pavement sections to the environmental loads. These sections were constructed in May of 2010 at the Minnesota Road Research Facility. The sections are constructed in three individual cells, Cell 70, a HMA-over-PCC with recycled concrete aggregate (RCA), Cell 71, exposed aggregate concrete (EAC)-over-RCA and Cell 72, EAC-over-economical concrete. All cells were heavily instrumented with thermocouples, moisture sensors, and static and dynamic strain gauges. This study characterises the structural response of HMA-over-PCC pavements and also PCC-over-PCC to the environmental loads.

Winter temperature prediction for near-surface depth of pervious concrete pavement

ABSTRACT Pervious concrete pavement (PCP) consists of a highly porous concrete slab, placed on a permeable base layer. This permeable pavement system allows storm water runoff to infiltrate through the pavement and percolate into the subdrainage system or directly into the subgrade soil. PCP is gaining popularity in municipal applications across the United States, including the cold climate regions. The focus of this study was to investigate frost durations at PCP near-surface depths for use in winter maintenance operations. Also, tools are recommended for predicting the near-surface temperature of PCP during winter months. A PCP sidewalk was placed and instrumented on Washington State University’s campus in Pullman, WA. First, temperature measurements at various depths of the PCP sidewalk and frost periods at the respective depths were presented during one winter season. Second, the Enhanced Integrated Climatic Model (EICM) was used to predict the PCP’s near-surface temperature during the winter. Using each layer’s thermal properties, the EICM estimates the heat transfer between the pavement and the surroundings. Heat conductivity and capacity were defined for the PCP using the parallel model, based on PCP porosity and the volumetric proportions of the mixture constituents. Meteorological indices for the model were obtained from a local weather station and an on-site pyranometer for solar radiation. Comparison of the predicted temperature for the top three-inch (76 mm) depth of the pervious concrete layer showed agreements with the field data during the winter. A multiple linear regression model was developed to predict PCP’s temperature at 0.5 inch (13 mm) depth.