Xie P.,Missouri University of Science and Technology |
Grant S.,Missouri University of Science and Technology |
Putnam N.,Missouri University of Science and Technology |
Anderson N.,Missouri University of Science and Technology |
Nasseri-Moghaddam A.,Inspec Sol Inc.
2012 14th International Conference on Ground Penetrating Radar, GPR 2012 | Year: 2012
This paper investigates challenges faced by many geophysical algorithms applied to real-world cases such as the Attenuation Analysis of Rayleigh Waves (AARW). AARW shows great promise in terms of detecting shallow underground tunnels. However, in-situ subsurface anomalies, including those due to anisotropy, and instrument sensitivity to natural conditions can significantly degrade the utility of this technique. The first applied measure estimates the confidence level of each detection result. The second processes the recorded data in sub-arrays, acting as a filter to remove false alarms. The third scans all detections and searches the cluster with the highest cumulative confidence level. A case study is presented to demonstrate the effectiveness of AARW along with post-processing quality control measures. This work provides engineering practitioners with a simple and efficient method to reliably determine tunnel locations. ©2012 IEEE.
Bouzoubaa N.,CANMET Energy |
Bilodeau A.,CANMET Energy |
Tamtsia B.,Inspec Sol Inc. |
Foo S.,Public Works and Government Services Canada
Canadian Journal of Civil Engineering | Year: 2010
The present study consists of investigating the carbonation resistance of two series of concrete mixtures designed for three classes of concrete (25, 35, and 45 MPa compressive strength at 28 d) and using American Society for Testing and Materials (ASTM) type I Portland cement and two commercially used fly ashes meeting the ASTM standards at the level of 20%, 35%, and 50% of the total weight of cementitious materials. The carbonation resistance was determined on samples moist cured for 3, 7, and 10 d and exposed to a CO2-enriched environment (3% CO2 at 23 °C and 65% relative humidity) for 140 d to accelerate the carbonation; it was also determined on samples moist cured for 7 d and exposed to an indoor and outdoor natural environments for 4 years. A mathematical model allowing the prediction of the depth of accelerated carbonation of fly ash concrete mixtures is presented.
Nasseri-Moghaddam A.,Inspec Sol Inc. |
Park C.B.,Park Seismic LLC.
Proceedings of the Symposium on the Application of Geophyics to Engineering and Environmental Problems, SAGEEP | Year: 2010
The effect of source offset distance and the geophone array length on the dispersion curves are discussed in this paper. The source offset distance was changed systematically at sites with various subsurface conditions to investigate its effect on quality of data and the corresponding dispersion curves. Further, tests were carried out at same locations with various geophone intervals to evaluate the effect of the array length on the quality of the data and dispersion curves. Active and passive data were collected and the dispersion images were combined for possible improvement in dispersion image with enhanced multimodal delineation over a broadened bandwidth. It is observed that source offsets in the range of 25% to 45% of the array length provide dispersion curves with reasonable quality. Further, collecting data with different geophone intervals (same array mid station) improves the resolution of the obtained dispersion image. Multi geometry technique is suggested to obtain better quality field data. In this approach two (or more) different geophone intervals are used with same mid station. Passive and active data at two or more offset distances are collected for each of the array geometries. Stacking the obtained dispersion images can also result in a better quality dispersion curve.
Khayat K.H.,Université de Sherbrooke |
Hwang S.-D.,Université de Sherbrooke |
Belaid K.,Inspec Sol Inc.
ACI Materials Journal | Year: 2010
Viscosity-enhancing admixtures (VEAs) are water-soluble polymers that increase viscosity and cohesion of cement-based materials. Such enhancement is essential in highly flowable concrete including self-consolidating concrete (SCC) - to control the risk of segregation. For a given mixture composition, the performance of SCC can widely vary with the type and dosage rate of the VEA in use. The main objective of this investigation is to compare the performance of five VEA systems in SCC. More specifically, the investigation seeks to determine the effect of VEA type on key workability and engineering properties of SCC designated for cast-in-place building applications. The concrete is designed with a characteristic compressive strength of 35 MPa (5076 psi) at 28 days. In total, five VEAs incorporated with two compatible high-range water-reducing admixtures (HRWRAs) are investigated. A finely ground limestone filler that can be used as a stabilizer in flowable concrete is also included in the study. Copyright © 2010, American Concrete Institute. All rights reserved.
Xie P.,Intel Corporation |
Grant S.L.,Missouri University of Science and Technology |
Putnam N.H.,U.S. Department of Defense |
Anderson N.L.,Missouri University of Science and Technology |
Nasseri-Mohgaddam A.,Inspec Sol Inc.
IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing | Year: 2014
This paper investigates challenges faced by many geophysical algorithms applied to real-world cases such as the Attenuation Analysis of Rayleigh Waves (AARW). AARW shows great promise in terms of detecting shallow underground tunnels. However, in-situ subsurface anomalies, including those due to anisotropy, and instrument sensitivity to natural conditions can significantly degrade the utility of this technique. To address this problem, this work proposes a data acquisition scheme and develops a new post-processing approach. The first applied measure estimates the confidence level of each detection result. The second processes the data in sub-arrays, and filters out false alarms. The third scans all detections and searches the cluster with the highest cumulative confidence level. This paper provides engineering practitioners with a simple and efficient method to reliably determine tunnel locations. Experimental results derived from data recorded in various testing sites and surface conditions verify the effectiveness of this work. © 2014 IEEE.
Kandasamy S.,Inspec Sol Inc. |
Shehata M.H.,Ryerson University
Cement and Concrete Composites | Year: 2014
The efficiency of ternary blends containing high-calcium fly ash and slag in mitigating alkali-silica reaction (ASR) was evaluated. The concrete prism expansions showed that the ternary blends did not offer significant advantage over binary blends of portland cement and either of the individual material at the same total SCM content. The ability of a particular blend to mitigate ASR was related to its capacity to retain alkalis in its hydration products, as evaluated by an alkali leaching test. For the slag and fly ash used in this study, the capacity to retain alkalis increased with the ability of the blend to consume Ca(OH)2 during its pozzolanic reaction. For the blends investigated here, the alkali leaching test was more realistic than the accelerated mortar bar test in predicting the 2-year expansion of concrete prisms. The adopted alkali leaching test is proposed to be used as a tool to compare the efficacy of different cementing blends to mitigate ASR. © 2013 Elsevier Ltd. All rights reserved.
Kandasamy S.,Inspec Sol Inc. |
Shehata M.H.,Ryerson University
Construction and Building Materials | Year: 2014
Cementing blends containing high-calcium fly ash (HCFA) is known to have low resistance to sulphate attack. This paper presents the results of an experimental program that focuses on attempts to enhance the performance of HCFA through the incorporation of granulated blast furnace slag in the mix. The expansions of various blends were evaluated using the mortar bar test according to ASTM C1012. Mortar bars were made with 100% Portland cement (control mix), binary blends of either HCFA or slag, and ternary blends of HCFA/slag. The expansions were measured up to two years. The addition of slag was found to improve the resistance to sulphate. When the level of combined HCFA and slag reached 60% of the total cementing materials, there was a significant reduction in the expansion regardless of the level of each of the individual material. In addition to expansion results, the paper evaluates the role of chemical and mineralogical composition of the cementing blend, the ion diffusion of the mixtures, and the calcium hydroxide consumption on the sulphate resistance of the different blends. © 2013 Elsevier Ltd. All rights reserved.
Nasseri-Moghaddam A.,Inspec Sol Inc. |
Bennett J.,Inspec Sol Inc. |
Polan B.,Inspec Sol Inc.
9th US National and 10th Canadian Conference on Earthquake Engineering 2010, Including Papers from the 4th International Tsunami Symposium | Year: 2010
NBCC(2005) and IBC (2006) seismic provisions emphasize that a quantitative approach is required for the determination of seismic site class for construction projects. According to these Codes the preferred method for proper site class assessment is the measurement of shear wave velocities within the upper 30 m of the underlying soil/rock profile (V S30). In some cases, other methods such as SPT test are allowed to be utilized for this purpose; however, these methods are generally time consuming, costly and provide localized information at the site. Multi channel analysis of surface waves (MASW) method is used to measure shear wave velocities within the underlying soil/rock profile at three sites for seismic site class determination. The MASW test results are compared to the information obtained from deep boreholes. The results show that in some cases seismic site class determination using different methods may end up with different results. Two cases are presented in which the measured V S30 at different locations at the Site resulted in different site classes. Suggestions are made to clarify the site class determination procedure provided in the Codes. Copyright © (2010) by Earthquake Engineering Research Institute.