Tex Sys - Introduction

Introduction

Project Survey

TexSys covers the 4 major HMA types listed in the Department’s 2004 Standard Specification book. The 4 mixture types are:

    • Item 340 and 341 – Dense Graded Mixtures
    • Item 342 - Permeable Friction Course (PFC)
    • Item 344 - Performance Design Mixtures
    • Item 346 - Stone Matrix Asphalt (SMA)

TexSys is intended to provide general recommendations based on the experiences of the engineering staff in the Flexible Pavements Branch of TxDOT’s Construction Division. It is not intended to be used as Department policy. Districts are encouraged to make mixture selection choices based on engineering judgment along with the recommendations provided in this guidance document. A number of factors should be considered when selecting which HMA mixture is most appropriate for the intended application. Some of the factors that should be considered include:

    • previous experience with similar mixture types
    • volume of truck traffic, traffic flow characteristics
    • pavement geometric considerations
    • lift thickness of paving layers
    • condition of underlying pavement
    • availability of local materials
    • climatic and environmental conditions
    • cost (initial as well as life cycle)
    • selected performance grade (P.G.) binder

It is important that the designer select the proper mixture for the intended applications. It is also very important the designer select the appropriate PG binder and aggregate properties for the intended application. These topics will not be covered in this document since most TxDOT districts have guidelines or policies currently in place that address binder and aggregate property selection. Those needing additional assistance should contact their district pavement engineer, district construction engineer, laboratory personnel or the Construction Division.

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