Civil Engineering

Compaction tests (isotropic drained loading) were conducted on randomly packed glass beads that were: 1) uncemented and 2) cemented by epoxy at their contacts. In the latter case, the volume of the epoxy accounted for 10% of the pore space. Intensive crushing of grains was observed in the first case at about 50 MPa. In the second case, the cemented grains stayed intact, the failure being localized within the epoxy. Therefore, even small amounts of cement at contacts prevent the failure of grains. Theoretically, this effect follows from the theory of cemented granular materials: stress concentration is high at the contacts of uncemented grains, whereas even small amounts of relatively soft cement result in a more uniform stress distribution over a larger contact area. (Authors) 951052

The purpose of this study was to assess the mechanical property performance behavior of calcium sulfoaluminate (CSA) cement mortar when cured at ambient laboratory temperature of ~23°C (73°F) and constant 50% relative humidity for an extended period of time. Four CSA cement mortars were tested. Three CSA cement mortars contained equivalent mass amounts of calcium sulfate; whereas, the fourth mortar contained double the amount of calcium sulfate. The three CSA cement mortars containing constant mass amounts of calcium sulfate differed as the specific type of calcium sulfate varied across the three formulations-one mortar containing solely anhydrite, one mortar contained half anhydrite and half gypsum while the other mortar solely contained gypsum. The fourth mortar contained double the amount of calcium sulfate when compared with the others while having a 1/1 blend of anhydrite and gypsum. Specific mortars were either tested for direct tensile strength according to ASTM C307 or for compressive strength according to ASTM C109. All tested mortars displayed statistically significant strength loss trends versus time when cured at constant 50% relative humidity. Cement paste samples were analyzed with TGA/SDT and XRD in an effort to identify microstructure changes corresponding to observed strength loss. Cement paste analysis suggests strength loss within the tested CSA cement mortars occurred as a result of ettringite decomposition.

Atmospheric fluidized bed combustion (CFBC) produces spent bed fly ash and bottom ash consisting primarily of lime (CaO), anhydrite (CaSO 4), calcined clay materials and quartz. These materials have a much larger surface areas than conventional pulverized coal combustion (PCCA) fly ash. But, problems with swelling and strength loss have limited their usefulness. The potential of the CFBC fly ash as a pozzolanic additive to portland cement was investigated. The pre-hydrated CFBC fly ash was tested "as received" and as beneficiated by hydraulic classification or screening to remove the >200 mesh materials. The CFBC was also blended with PCCA fly ash. The mortar bar tests indicated that the CFBC fly ash was dimensionally stable and beneficiating the ash further reduced expansion. The CFBC materials did not lower water demand. The CFBC fly ash initially retarded strength development but by 7 days this was not a major factor. The CFBC materials performed well in concrete.

The utilization of circulating fluidized bed combustion (CFBC) ash to make cement products that provide added value and offset CO2 production is the objective of this research. CFBC burns coal in the presence of a bed of slaked limestone, which effectively absorbs sulfur dioxide (SO2) to form anhydrite (CaSO4). CFBC produces two kinds of spent bed materials, coarse bottom ash and a much finer fly ash. Both of these products are very high in calcium. When properly conditioned, these materials are capable of acting as hydraulic cements, forming both calcium aluminosulfate minerals, most importantly ettringite, as well as calcium-alumina-silica gels, like that formed from Portland cement. The research to generate calcium sulfoaluminate-belite (CSAB) cement was centered on two components. The first was the production of a cement that maximizes the proportion of coal combustion by-products while achieving acceptable strength development. The second component focused on optimizing the lab...

This report presents a user's guide for an expert decision-making system that utilizes findings of an extensive literature search and review conducted as part of this study. The literature search and review were conducted to determine current attitudes and document available technical data relative to the use of recyclable and recoverable materials in highway construction and maintenance activities. Specifically, the literature search focused upon the engineering, economic, and perfonnance aspects of using recyclable and recoverable materials in highway construction and maintenance projects. The effort cantered upon asphan and Portland cement concrete pavement recycling, discarded tire recycling, reuse of pamt removal wastes, fly ash, glass, alternative fuels. and other miscellaneous recycled and recovered materials as related to construction and maintenance of highways. Additionally, regulatory and policy matters assooated with the use of recyclable and recoverable materials in the transportation area were investigated during the review of pertinent literature.

In an effort to reduce rutting in the new Louisa Bypass in Lawrence County, Kentucky, a large-stone asphaltic base mix (Class K) was used in the base layer. A one-inch surface wearing course was used in this project, a polymer-modified asphalt was used in the surface course on half of the project. In order to facilitate subsurface drainage, a free draining subbase (No. 57's) was placed between the large-stone base and a dense-graded aggregate (DGA) layer. The drainage design was further enhanced by edge and median drains. Construction processes were monitored and photographed. Laboratory and field studies were conducted to determine the perfmrnance characteristics of individual pavement components. Performance of the Louisa Bypass project has been and will be monitored.

Large-stone mixes are becoming a very popular means for reducing rutting in flexible pavements. Aggregate interlock in large-stone mixes provides for very efficient dissipation of compressive and shear stresses that are known to be responsible for rutting -and shoving in flexible pavements. This report documents mix design procedures and -laboratory testing for characterization of rutting potential of large-stone asphalt mixes (LSAM) in Kentucky and particularly the Louisa Bypass project.

A rational asphalt concrete (AC) mix design and analysis methodology was developed. The term "rational" meant that the material properties evaluated in the mixture design and analysis could be used with a layered-elastic pavement model and mechanistic-empirical formulations that relate to pavement performance. The procedures proposed in this study were intended to be used in conjunction with the current Texas State Department of Highways and Public Transportation method of mix design in a complementary fashion. Three major modes of pavement distress--(a) rutting, (b) flexural fatigue, and (c) low-temperature cracking--were addressed. In addition to mixture properties, structural arrangement of pavement layers and environmental factors have significant effects on the performance of AC mixtures. Therefore, a comprehensive mix design should not be performed independent of pavement structural design. Asphalt mix design and pavement structural design parameters were brought tog...

─────────────────────────────────────────────────────── Abstract: Concrete joint failure is a major distress mode in rigid pavements. Improving the joint performance in concrete pavements could yield substantial savings in terms of reduced maintenance and rehabilitation costs. The newly developed Hinged Dowel System (HDS) is a means for transferring loads across the concrete pavement joints. The HDS was patented as a new invention by the United States Patent and Trademark Office, and it is envisioned that it could significantly reduce the potential for joint failure in concrete pavements. The HDS assembly comprises a number of dowel bars and a collective hinge provided at the mid-length of the dowel bars. A finite element analysis showed that the application of HDS reduces the shear stress in concrete pavement joints by approximately 15% when compared to the conventional dowel bars. This amount of reduction in shear stress could translate into a significant reduction in shear-induce...

The NCHRP Mechanistic–Empirical Pavement Design Guide (MEPDG) is a powerful tool for the design and analysis of highway pavements. Currently, the designer uses an iterative process to select design parameters and predict performance. If performance is unacceptable, the designer must change the design parameters until acceptable performance is achieved. A procedure outlined here used multiple adaptive regression splines (MARS) to develop predictive models obtained from a series of actual pavement design solutions from MEPDG software. Two model structures were developed: a series of models to predict individual pavement distress (rutting, fatigue cracking, and roughness) and a forward solution to predict pavement thickness from a desired level of distress. This model can be used to determine a starting thickness, which then can be used with the MEPDG software to obtain a refined design, potentially with fewer iterations to define an acceptable design thickness. These thickness predict...

The mechanistic–empirical pavement design guide (MEPDG), developed under the recently completed NCHRP Project 1–37A, is a complex tool. Sensitivity analyses typically vary a single input parameter while holding other parameters constant. A pilot project is outlined to identify the feasibility of a global sensitivity analysis of the design process by using random sampling techniques over the entire input parameter space. This study sampled the following flexible pavement input variables: hot-mix asphalt (HMA) base nominal aggregate size, climate location, HMA thickness, annual average daily truck traffic (AADTT), subgrade strength, truck traffic category, construction season, and binder grade “bump.” A total of 100 design sections were randomly sampled from these input parameters. The resulting predicted performance of longitudinal and alligator cracking, HMA and total rutting, and international roughness index were analyzed by using the Pearson's and Spearman's correlation c...

h i g h l i g h t s Utilization potential of Spray Dryer Absorber Material (SDAM) as an additive in concrete was determined. A 20 wt% replacement of OPC with SDAM yielded a concrete that met the desirable 28-day performance criteria. The results provide evidence against the stigma of poor durability when using SDAM in concrete.

Concrete joint failure is a major distress mode in rigid pavements. Improving the joint performance in concrete pavements could yield substantial savings in terms of reduced maintenance and rehabilitation costs. The newly developed Hinged Dowel System (HDS) is a means for transferring loads across the concrete pavement joints. The HDS was patented as a new invention by the United States Patent and Trademark Office, and it is envisioned that it could significantly reduce the potential for joint failure in concrete pavements. The HDS assembly comprises a number of dowel bars and a collective hinge provided at the mid-length of the dowel bars. A finite element analysis showed that the application of HDS reduces the shear stress in concrete pavement joints by approximately 15% when compared to the conventional dowel bars. This amount of reduction in shear stress could translate into a significant reduction in shear-induced failures in concrete pavements. The HDS includes mechanisms whic...

Concrete joint failure is a major distress mode in rigid pavements. Improving the joint performance in concrete pavements could yield substantial savings in terms of reduced maintenance and rehabilitation costs. The newly developed Hinged Dowel System (HDS) is a means for transferring loads across the concrete pavement joints. The HDS was patented as a new invention by the United States Patent and Trademark Office, and it is envisioned that it could significantly reduce the potential for joint failure in concrete pavements. The HDS assembly comprises a number of dowel bars and a collective hinge provided at the mid-length of the dowel bars. A finite element analysis showed that the application of HDS reduces the shear stress in concrete pavement joints by approximately 15% when compared to the conventional dowel bars. This amount of reduction in shear stress could translate into a significant reduction in shear-induced failures in concrete pavements. The HDS includes mechanisms whic...

This report addresses issues related to transferring the responsibility for quality control from the Kentucky Transportation Cabinet (KyTC) to construction contractors. Surveys of the KyTC, other state departments of transportation, and Kentucky highway contractors were done to identify the advantages, concerns, and modifications of the Contractor Performed Quality Control (CPQC) program. An advisory committee of experienced KyTC engineers, Federal Highway Administration representatives, and contractor representatives met periodically to identify approaches for handling key issues of the program. Several key topics related to CPQC are presented in this report, with emphasis on quality control/quality assurance (QC/QA) administration, QC/QA procedures, quality acceptance and verification testing, and CPQC training. Specific issues related to CPQC pay items in Kentucky are also discussed. Several recommendations have been proposed to enhance the program. If properly implemented, CPQC ...