Influence of Powder Activated Carbon (PAC) in Fly Ash on the Properties of Concrete

Class C Fly Ash (CFA) is commonly used as supplementary cementitious material (SCM) in producing concrete by ready-mix concrete contractors in Arkansas. However, CFA can be used as a partial replacement of Ordinary Portland Cement (OPC) if it meets certain ASTM requirements. It is believed that the presence of powder activated carbon (PAC) in CFA increases the demand of the air-entraining agent (AEA) to achieve specified air content, and this is a concern to transportation agencies such as the Arkansas Department of Transportation (ARDOT) and concrete producers in recent years. Thus, the main goal of this research is to assess the influence of PAC in fly ash on the properties of concrete. To achieve the goal of this study, a total of 14 mixes (12 laboratory and two plant mixes) were evaluated to determine the fresh concrete properties (e.g., air content, workability, and unit weight) as well as hard concrete properties (e.g., compressive, tensile and flexural strength, modulus of elasticity, and long-term durability). Besides the Pressure Meter method, a Super Air Meter (SAM) and a Miller 400A resistivity meter were used in this study to determine the air quality and electric resistance, respectively, of the prepared fresh concrete. Two CFAs containing the different percent of PAC (i.e., 0%, 0.25%, 0.50%, and 0.75% by the mass of CFA) were used to prepare the mixes where the dosage of AEA was selected based on the manufacture recommendation. Air content measurements of two selected hard concrete mixes were also made in the laboratory. The results showed that the PAC content had a significant effect on the air content of the fresh concrete. The air contents of plant mixes agreed with those of the laboratory mixes. The SAM test was found to be an effective test method to measure the air-void quality of fresh concrete mixes; the air content and quality measurements of fresh concrete were comparable with air voids of hard concrete. The long-term durability (alkali-silica-reactivity and scaling resistance) was found to be influenced by the PAC content as well as the source of CFA. The findings of this study can help to better understand the effect of PAC content in CFAs in producing durable concrete

Edge Aware Anisotropic Diffusion for 3D Scalar Data

Fig. 1: The left half of the figure demonstrates the consistency in smoothing of our method compared to the existing method. The right half of the figure demonstrates the de-noising capabilities of our method. All the images from (a-c) were obtained byrenderingan iso-surface of 153. (a) Diffused with an existing diffusion model proposed by Krissian et al. [20] with k = 40, and100 iterations (b) The original Sheep’s heart data. (c) Diffused with our method with σ = 1 and the same number of iterations. The yellow circle indicates aregionwheretheiso-surfacehasbothhighandmediumrangegradient magnitude, and the blue circle marks a region where the gradient magnitude is much lower. Note the inconsistent smoothing in (a) inside the yellow circle. (d) The tooth data contaminated with Poisson noise (SNR=12.8) (e)Theoriginaltoothdata(f)Diffusedwithourmethod(SNR=25.76) withσ = 1 and 25 iterations. We used the exact same transfer function to render all the images in(d-f). Abstract—Inthispaperwepresentanovelanisotropicdiffusionmodel targeted for 3D scalar field data. Our model preserves material boundaries as well as fine tubular structures while noise is smoothed out. One of the major novelties is the use of the directional second derivative to define material boundaries instead of the gradient magnitude for thresholding. This results in a diffusion model that has much lower sensitivity to the diffusion parameter and smoothes material boundaries consistently compared to gradient magnitude based techniques. We empirically analyze the stability and convergence of the proposed diffusion and demonstrate its de-noising capabilities for both analytic and real data. We also discuss applications in the context of volume rendering

No-tillage Transplanting System of Rice with Controlled Availability Fertilizer in a Nursery Box : Nitrogen Use Efficiency of Controlled Availability Fertilizer of Rice Plant in Three Different Paddy Fields

The fate of polyolefin ^N coated urea (POCU S-100) in a nursery box for the no-tillage transplanting system as compared with ^N ammonium sulfate (AS) in the conventional tillage system had been investigated in light clay alluvial soil, sandy loam alluvial soil, and clay loam soil (Andisol) in 1994 and 1995. Rice (Oryza sativa L. cv. Hitomebore) was used as the test plant. The nitrogen concentration of the leaf blade of the rice plant in the no-tillage without rice straw (NT) and no-tillage with rice straw (NTS) treatments tended to be greater than those of the conventional tillage with rice straw (CTS) treatments in all types of soil at all growth stages, and there was no definite increasing or decreasing tendency in the N concentration of the leaf sheath and stem, and panicles of the rice plant among the treatments in all types of soil. Nitrogen recoveries from POCU S100 in the NT and the NTS systems were 77-79% and 78-83%, 61-73% and 66-78%, and 74-76% and 80-81% for light clay soil, sandy loam soil and clay loam soil, respectively, which is around 65.5-96% of the nitrogen released from POCU S100. Thus, this could reduce the environmental pollution. The straw application in the NT system increased the N recovery of POCU S-100 by 1-5%. On the other hand, nitrogen recoveries from ammonium sulfate applied as basal fertilizer in the CTS system were 35-43%, 20-29% and 23-32% for light clay soil, sandy loam soil and clay loam soil, respectively. Whereas those applied as a top dressing were 50-83%, 49-73% and 40-65%. Nitrogen uptake by the rice plant in the NT system was relatively higher than that in the CT system. The uptake of soil nitrogen by the rice plant in the NT system was lower than that in the CT system

EVALUATION OF RHEOLOGICAL PROPERTIES OF ASPHALT BINDERS FOR PAVEMENT DESIGN APPLICATIONS

More that 90% of the total paved roadways in the U.S. are asphalt concrete (AC) pavements. The annual expenditures for construction and maintenance of these pavements exceed $10 billion. To reduce these maintenance costs, it is crucial to design and construct pavements that perform well during its design life. Even though significant advances have been made in the analysis and design of hot mix asphalt (HMA) during the last two decades, pavement communities are still challenged with evaluating the performance of paving materials, in which the asphalt binder plays a significant role. Such challenges are getting augmented by the introduction on new paving technologies and materials such as warm mix asphalt (WMA) and recycled asphalt pavement (RAP). The main objectives of this study were to evaluate rheological properties of modified binders and predict the performance of the mixes.The current study evaluated the effects of two commonly used anti-stripping (AS) agents (AD-here® HP Plus and Perma-Tac® Plus) on the rheological properties of a PG 64-22 binder. The optimal dosage of either of these AS agents was found to be 0.5%. The current study also evaluated the effects of different dosages two WMA additives (Advera® and Sasobit®) on the rheological properties of the PG 64-22 binder. The optimal dosage of Advera® was found to be 6%, which was not expected to change the PG grade of the base binder. While Advera® was found to be ineffective in reducing the viscosity at production temperatures, 3% Sasobit® was expected to reduce the mixing and compaction temperatures by 16oC and 19oC, respectively. Sasobit® was found to increase the stiffness of the binder. The optimal dosage of Sasobit® was found to be 1.5%. AS agent (AD-here® HP Plus) did not show any adverse impacts on the WMA-modified binder. It was also observed that binders recovered from three local RAP samples were found to be significantly stiffer than their virgin counterparts. The prolonged use of the centrifugal force and heat in the Abson recovery process was also found to harden the recovered binder.The current study also developed an inventory of the mechanistic-empirical pavement design guide (MEPDG) input parameters for three binders collected from three refineries. The viscosity and stiffness of these binders were found to vary significantly from one source to another. The Witczak model, based on dynamic shear rheometer (DSR) test data of the binder, was found to underestimate the dynamic modulus (E*) values of mixes. The rotational viscosity data, however, overestimated the E* values. The Hirsch model, based on frequency sweep test data, was found to be a better-fit than the Witczak model. The estimated E* values of the Sasobit®-modified mix were found to be significantly higher than those of a control HMA mix. Distress factors of a typical pavement section estimated through the MEPDG software, predicted that about 40% of the total rutting would occur in the AC layers, of which 80% would occur in the surface course. It was also predicted that about 39% of total rutting would occur within two years of construction. The AC layers' rut depths were found to vary significantly with changes in binder type and source. Fatigue fracture, thermal cracking, and roughness were not found to be critical distresses in this study. The findings of this study are expected to provide pavement professionals a better understanding of the rheological evaluation of unmodified and modified binders for pavement design applications

Development of Metals Corrosion Maps of Arkansas and Maintenance of Cross-Drains

Corrosion potential of metallic structures in alluvial soils is governed by chemical and electromagnetic properties of the soils. Geotechnical engineers are generally more concerned about different types of soils and their physical and mechanical properties than the chemical aspects. The main objective of this study is to analyze the geotechnical, electrochemical and electromagnetic properties of soils in Arkansas. Important parameters (e.g., soil resistivity) related to corrosion potential of metal culverts have been predicted through neural network (NN) models. The developed NN models have been trained and verified by using laboratory test results of soil samples collected from Arkansas Department of Transportation (ARDOT), and survey data obtained from the United States Department of Agriculture (USDA) and Arkansas Department of Environmental Quality (ADEQ). Finally, the Geographic Information System (GIS) based corrosion risk maps of three different types of metal pipes have been developed based on the available soil properties, metal properties, and water quality data. The developed maps will help ARDOT engineers to assess corrosion potential of metal pipes prior to the new construction and repair projects and use proper culvert and cross drain materials