Design criteria for controlled low strength materials

Controlled Low Strength Materials (CLSM) is now available under Department of Transportation specifications. Although a widely used material, some of its properties are not clearly studied and developed. Most of its properties are studied from field experience with exclusive usage, hence it may not be suitable in other applications. This study explores the properties of CLSM to develop better mix design. They are important to design CLSM mixes with consistent mix designs, workable and more flowable mixes, optimum utilization of waste materials, controlled density and strength, and suitability to specific applications. Although most CLSM applications are designed not to resist freeze and thaw deterioration, some specific applications are susceptible to deterioration. There are two ways to improve durability of CLSM. They are: (a) provide more air bubbles, and (b) increase strength. Selection methods are based on the application. Two important properties of CLSM are settings and strength development at early age. These are important to mixing, placing, and transporting CLSM, and to construction procedures. When time is a major concern, settings and strength development are important so a structure or facility can resume operation several hours after placement. Based on settings in concrete, two stages are defined: (a) Stiffening-stage, and (b) Hardening-stage. Stiffening-stage indicates a beginning of cohesion while Hardening-stage indicates hardening which load can be sustained. Some advantages of using CLSM as back-fill are: self-leveling, self-consolidation or self-compacted, and low long term settlement. The CLSM should easily flow and fill voids, hence flowability is important. There are two ways to improve the flowability: (a) increasing water content, and (b) increasing fly ash content. However, increasing water content is not encouraged due to segregation of particles. CLSM can be designed to meet Resilient modulus values rather than strength. This would enable its use in locations around structures to match the adjacent soil or to act as a transition between the high modulus of a structure and the relatively low modulus value of the soil. In addition, suitability of CLSM as subgrade material is better evaluated using resilient modulus

Performance Related Specifications (PRS) for Concrete Pavements in Indiana, Volume 1: Executive Summary

Performance-Related Specifications (PRS) are specifications that base pavement acceptance and pay adjustment on the projected performance and predicted life-cycle cost (LCC) for a specific pavement. PRS relate measurable quality characteristics with pavement performance through computer simulations that incorporate physical distress models. Previously, work at ERES consultants by Darter and co-workers developed prototype PRS for jointed plain portland cement concrete pavements (PCC) through Federal Highway Administration (FHWA) through a series of research projects. However, before this research program began, pavements have not been constructed using these specifications. This report describes the Indiana Department of Transportation’s (INDOT) experience with developing and implementing the first and second Level 1 PRS projects during the re-construction of a portion of I-465 east of Indianapolis and I-65 north of Clarksville, respectively. This report includes an overview of the concepts behind PRS, the process of developing a Level 1 PRS, lessons learned from implementing the first PRS in the construction of the pavement outside Indianapolis during the summer of 2000, lessons learned from implementing the second PRS in the construction of the pavement outside Clarksville during the summer of 2002, the use of non-destructive testing procedures to obtain measures of pavement quality, sample specifications, and conclusions and recommendations. In general, this specification was well received by both the agency and the contractors. It is believed that lessons learned on these projects will enable future modifications to the development of performance related specifications with the hope that these specifications will enable longer lasting, more cost effective pavements to be constructed

Performance Related Specifications (PRS) for Concrete Pavements in Indiana, Volume 2: Technical Report

Performance-Related Specifications (PRS) are specifications that base pavement acceptance and pay adjustment on the projected performance and predicted life-cycle cost (LCC) for a specific pavement. PRS relate measurable quality characteristics with pavement performance through computer simulations that incorporate physical distress models. Previously, work at ERES consultants by Darter and co-workers developed prototype PRS for jointed plain portland cement concrete pavements (PCC) through Federal Highway Administration (FHWA) through a series of research projects. However, before this research program began, pavements have not been constructed using these specifications. This report describes the Indiana Department of Transportation’s (INDOT) experience with developing and implementing the first and second Level 1 PRS projects during the re-construction of a portion of I-465 east of Indianapolis and I-65 north of Clarksville, respectively. This report includes an overview of the concepts behind PRS, the process of developing a Level 1 PRS, lessons learned from implementing the first PRS in the construction of the pavement outside Indianapolis during the summer of 2000, lessons learned from implementing the second PRS in the construction of the pavement outside Clarksville during the summer of 2002, the use of non-destructive testing procedures to obtain measures of pavement quality, sample specifications, and conclusions and recommendations. In general, this specification was well received by both the agency and the contractors. It is believed that lessons learned on these projects will enable future modifications to the development of performance related specifications with the hope that these specifications will enable longer lasting, more cost effective pavements to be constructed