Development of Void Prediction Models for Kansas Concrete Mixes Used in PCC Pavement

AbstractPermeability of the concrete material used in Portland Cement Concrete (PCC) pavement structures is a major factor for long-term durability assessment. To properly characterize the permeability response of a PCC pavement structure, the Kansas Department of Transportation (KDOT) generally runs the Boil Test (BT) to determine the % void response. The BT typically measures the volume of permeable pore space within the concrete samples over a period of five hours at a concrete age of 7, 28, and 56 days. In this study, backpropagation Artificial Neural Network- (ANN) and Regression-based % void response prediction models for the BT are developed by using the database provided by KDOT in order to reduce the duration of the testing period or ultimately eliminating the need to conduct the BT. The noted excellent prediction accuracy of the developed models proved that the ANN and the Regression models have efficiently characterized the BT response. Therefore, they can be considered as effective and applicable models to predict the permeability (% void response) response of concrete mixes used in PCC pavements

Drying shrinkage of ternary blends in mortar and concrete

The work presented in this thesis involves the study of drying shrinkage behavior of mortars and field concrete mixtures made with ternary cementitious blends. The thesis is composed of two papers resulting from the study: (1) Short-Term Drying Shrinkage of Ternary Blends and (2) Drying Shrinkage of Ternary Blends for Use in Transportation Structure. In the former, statistical response surface analysis was employed to develop shrinkage models to better understand the drying shrinkage behavior of mortar mixes made with ternary blends. In the latter, ternary blend concrete mixtures used for pavement and bridge deck structures in different states were selected. Factors affecting drying shrinkage behavior of these ternary blend concretes were also investigated. In Paper 1, shrinkage behavior of mortar mixes made with various ternary blends was studied. Ternary blends consisting of different combinations of portland or blended cement, slag cement, fly ash (Class C and F) and/or silica fume were considered: the amounts of slag cement, fly ash and silica fume ranged between 15-35%, 13-30%, and 3-10% by mass of cementitious, respectively. Mortar bars were made with the ternary blends and subjected to a drying condition (i.e., T = 73 y 3 yF and RH = 50y4%) after standard curing for 28 days. Free shrinkage of the mortar bars was measured up to 28 days. Based on the test results, a response surface analysis was done to examine the effects of blend proportions on shrinkage behavior of the mortars and a statistical model was developed for predicting the mortar shrinkage behavior. Furthermore, to validate the models, shrinkage strains of an independent group of mortar mixes were measured, and the measured values were compared with the predicted values. The results indicated that among the three supplementary cementitious materials in the ternary blends studied, slag cement showed a dominant effect on mortar shrinkage. The contribution of Class C fly ash to the mortar free shrinkage was slightly less than that of slag cement. Increasing silica fume content slightly increased free shrinkage, while an increase in Class F fly ash content slightly decreased free shrinkage of the mortar. There was a good correlation between the measured shrinkage strain and the strain predicted from the shrinkage model developed from the response surface analysis. The work discussed in Paper 2 investigated the drying shrinkage behavior of ternary blend concretes that were used in transportation structures. Factors affecting drying shrinkage behavior of ternary blend concretes were studied. Five concrete mixes, used for either pavement or bridge deck construction, were tested for both restrained and unrestrained shrinkages. The effects of blend materials and mix proportion on the concrete shrinkages were assessed. The results indicated that shrinkage strain rate linearly increased with clay content of fine aggregate, cementitious material content, paste-to-void ratio (by volume), and dosage of water reducer of the concrete mixes. The study demonstrates that the supplementary cementitious materials (SCMs) can be used to develop a statistical model in order to quantitatively predict drying shrinkage strain. The study gives a better understanding on how SCMs affect mortar and concrete drying shrinkage behavior. Both free and restrained shrinkage methodologies provide efficient analyses on interacted drying shrinkage influence factors. The cracking potential derived from restrained ring shrinkage test can be used to predict drying shrinkage cracking potential of ternary blend concrete mixtures

Guide to the Prevention and Restoration of Early Joint Deterioration in Concrete Pavements TR-697, July 2017

In recent years, premature joint deterioration has occurred in concrete pavements in snowbelt states. Research has found two primary mechanisms behind the deterioration: (1) Certain deicing/anti-icing salts—calcium chloride and magnesium chloride— react with cement paste to form calcium oxychloride, an expansive material that is detrimental to concrete pavement performance (sodium chloride is not as reactive). (2) Freeze-thaw damage occurs in joints when a critical degree of saturation is reached or exceeded; salts can exacerbate the problem by keeping joints in a high state of saturation. As a result of these findings, the Iowa Highway Research Board commissioned the National Concrete Pavement Technology Center to write this guide. The primary goal is to help Iowa’s concrete pavement engineers understand the causes of premature joint deterioration, focusing on deterioration due to salt reactivity and joint saturation. The guide also discusses strategies for preventing or limiting such deterioration. One strategy is to limit applications of calcium chloride and magnesium chloride in order to mitigate the formation of calcium oxychloride. Another critical strategy is to keep the saturation level of the concrete below approximately 85 percent. This can be accomplished by designing a durable concrete that includes an adequate air-void system, supplementary cementitious materials, and a low water-to-cementitious-materials ratio, as well as by providing good drainage to the pavement system and following other best practices in concrete pavement design, construction, and maintenance. This guide also provides a summary of joint repair and restoration strategies, including a decision flow chart. Finally, the guide offers guidelines for developing project specifications, with appropriate references to Iowa DOT Standard Road Plans, Standard Specifications, and Instructional Memoranda

Material and Construction Optimization for Prevention of Premature Pavement Distress in PCC Pavements, Phase III Final Report, 2008

Mixture materials, mix design, and pavement construction are not isolated steps in the concrete paving process. Each affects the other in ways that determine overall pavement quality and long-term performance. However, equipment and procedures commonly used to test concrete materials and concrete pavements have not changed in decades, leaving gaps in our ability to understand and control the factors that determine concrete durability. The concrete paving community needs tests that will adequately characterize the materials, predict interactions, and monitor the properties of the concrete. The overall objectives of this study are (1) to evaluate conventional and new methods for testing concrete and concrete materials to prevent material and construction problems that could lead to premature concrete pavement distress and (2) to examine and refine a suite of tests that can accurately evaluate concrete pavement properties. The project included three phases. In Phase I, the research team contacted each of 16 participating states to gather information about concrete and concrete material tests. A preliminary suite of tests to ensure long-term pavement performance was developed. The tests were selected to provide useful and easy-to-interpret results that can be performed reasonably and routinely in terms of time, expertise, training, and cost. The tests examine concrete pavement properties in five focal areas critical to the long life and durability of concrete pavements: (1) workability, (2) strength development, (3) air system, (4) permeability, and (5) shrinkage. The tests were relevant at three stages in the concrete paving process: mix design, preconstruction verification, and construction quality control. In Phase II, the research team conducted field testing in each participating state to evaluate the preliminary suite of tests and demonstrate the testing technologies and procedures using local materials. A Mobile Concrete Research Lab was designed and equipped to facilitate the demonstrations. This report documents the results of the 16 state projects. Phase III refined and finalized lab and field tests based on state project test data. The results of the overall project are detailed herein. The final suite of tests is detailed in the accompanying testing guide

Developing a Simple and Rapid Test for Monitoring the Heat Evolution of Concrete Mixtures for Both Laboratory and Field Applications

Recently, activities and interest in monitoring the heat evolution of cement hydration in concrete have increased. This is because the development of early-age concrete properties (such as workability, setting time, strength gain, and thermal cracking resistance) is predominantly influenced by the kinetics of cement hydration. Various test methods are currently available for measuring heat of cement hydration; however, most existing methods require expensive equipment, complex testing procedures, and/or extensive time, thus making them unsuitable for field application. Although ASTM C 186 is used for determining the heat of hydration of cement, there is no standard test method for concrete. The overall object of this three-phase study is to identify, develop, and evaluate a standard test procedure for monitoring pavement concrete using a calorimetry technique. It is envisioned that the newly developed calorimetry test method will be able to verify appropriate concrete proportions, to identify potentially incompatible materials and conditions, and to predict concrete performance. The primary objective of Phase II (presented in this report) is to establish a standard test procedure as well as the methods for interpreting the calorimeter test results. The newly developed calorimeter test is completed more quickly than ASTM C 186, in approximately 24 hours. Among a number of uses, the test can be utilized as a quality control measure for prescreening concrete materials and a prediction tool for early-age cracking. The Phase II results demonstrate that the new calorimetry test method has a high potential for detecting concrete incompatibility problems, predicting fresh concrete properties (such as set time), and assessing hardened concrete performance characteristics (such as strength gain and thermal cracking)

Proportioning for performance-based concrete pavement mixtures

The work presented in this dissertation involves an effort to develop a mix proportioning tool that can be used to determine the required type and amount of concrete components in a mixture based on the desired fresh and hardened concrete properties. Concrete performance is affected by the quantity and quality of the paste, and aggregate systems. Therefore, this study analyzed the effect of binder systems with different types and content; the paste quality; and size, shape, texture and gradation of different aggregate systems on various fresh and hardened concrete properties. In this experimental program, a total of 178 mixtures were prepared with 7 different gradation systems, 12 binder systems, 25 binder contents, 6 different water-to-binder ratio (w/b), and 3 different nominal air content. Fresh properties of slump, air content, air-void system, setting time, unit weight, and temperature were tested. Hardened properties of compressive strength, rapid chloride penetration, surface resistivity, air permeability, and shrinkage were tested at various ages. However, to develop such a tool, this study overall focused on the assessment of workability, compressive strength, and durability as these three properties are commonly used as indicators of concrete performance. Durability was assessed by testing the rapid chloride penetration, and surface resistivity at 28-days. As part of this study, an artificial neural network (ANN) approach has been used for concrete mix proportion design to analyze the complexity between concrete properties and concrete components. Results have shown that development of a performance-based mix proportioning tool is possible for mixtures when aggregate gradation is not varied. Development of a mix proportioning tool with addition of the various aggregates systems generally was not as successful due to the increased variability of the mix design parameters such as size, shape, texture, and gradation of aggregates. The proposed mix proportioning tool is promising and achievable in terms of predicting the values of the tested properties based on the mix design variables. Although the proposed mix proportioning tool is not completely ready for prime time, the findings of this study can be implemented in real time when this approach is used with a larger data set

Characterizing the permeability of concrete mixes used in transportation applications: a neuronet approach

Master of ScienceDepartment of Civil EngineeringYacoub M. NajjarReliable and economical design of Portland Cement Concrete (PCC) pavement structural systems relies on various factors, among which is the proper characterization of the expected permeability response of the concrete mixes. Permeability is a highly important factor which strongly relates the durability of concrete structures and pavement systems to changing environmental conditions. One of the most common environmental attacks which cause the deterioration of concrete structures is the corrosion of reinforcing steel due to chloride penetration. On an annual basis, corrosion-related structural repairs typically cost millions of dollars. This durability problem has gotten widespread interest in recent years due to its incidence rate and the associated high repair costs. For this reason, material characterization is one of the best methods to reduce repair costs. To properly characterize the permeability response of PCC pavement structure, the Kansas Department of Transportation (KDOT) generally runs the Rapid Chloride Permeability test to determine the resistance of concrete to penetration of chloride ions as well as the Boil test to determine the percent voids in hardened concrete. Rapid Chloride test typically measures the number of coulombs passing through a concrete sample over a period of six hours at a concrete age of 7, 28, and 56 days. Boil Test measures the volume of permeable pore space of the concrete sample over a period of five hours at a concrete age of 7, 28, and 56 days. In this research, backpropagation Artificial Neural Network (ANN)-based and Regression-based permeability response prediction models for Rapid Chloride and Boil tests are developed by using the databases provided by KDOT in order to reduce or eliminate the duration of the testing period. Moreover, another set of ANN- and Regression-based permeability prediction models, based on mix-design parameters, are developed using datasets obtained from the literature. The backpropagation ANN learning technique proved to be an efficient methodology to produce a relatively accurate permeability response prediction models. Comparison of the prediction accuracy of the developed ANN models and regression models proved that ANN models have outperformed their counterpart regression-based models. Overall, it can be inferred that the developed ANN-Based permeability prediction models are effective and applicable in characterizing the permeability response of concrete mixes used in transportation applications

Investigation of the Load-Induced Cracking and Rutting Performance of Specialty Hot Mix Asphalt Overlay Mixtures

This study was initiated with the aim of investigating the cracking performance, rutting performance, and cost effectiveness of specialty and composite HMA mixtures utilized in New Jersey to rehabilitate deteriorated rigid pavements. As such, four, plant-produced, specialty HMA overlay mixtures currently used in New Jersey were evaluated in this study. These overlay mixtures included: a dense-graded, 9.5-SP mixture, a gap-graded, 12.5-SMA mixture, a dense graded, 4.75-HPTO mixture, and a uniformly graded, 4.75-BRIC mixture. The 9.5-SP, 12.5-SMA, and 4.75-HPTO mixtures were produced using PG 76-22 binder while the 4.75-BRIC was contained a PG 70-28 binder. The laboratory cracking and rutting performance of the mixtures were assessed using the overlay test, the dynamic modulus test, uniaxial cyclic fatigue test, bending beam fatigue test, and asphalt pavement analyzer test. The field reflection cracking performance of the HMA overlay mixtures were assessed by performing accelerated pavement testing on six full-scale, field sections. The field sections contained a similar substructure. However, the overlays utilized on the field sections consisted of a 9.5-SP, 12.5-SMA, 4.75-HPTO, 9.5-SP & 4.75-BRIC, 12.5-SMA & 4.75-BRIC overlay, and 4.75-HPTO & 4.75BRIC. Based on the results of the study it was determined that the use of a 4.75-BRIC interlayer generally improved the reflection cracking performance and overall cost effectiveness of the conventional and specialty overlay mixtures