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From page 101... ... 101 chapter five COMPACTION, QUALITY CONTROL, AND FIELD PERFORMANCE INTRODUCTION This chapter presents detailed findings on different approaches used by transportation agencies for compaction testing on laboratory samples, field compaction, QC/QA, and field performance evaluations of constructed UAB/subbase layers. Different aspects of compaction and QC of UAB and subbase construction are discussed by first introducing the theory of compaction along with the objectives behind compacting unbound aggregate pavement layers. Read the entire page →
From page 102... ... 102 densities established in the laboratory. Construction specifications for pavement layers often require the achieved field densities to be higher than a certain specified percentage of this target density value. Read the entire page →
From page 103... ... 103 tive energy leads to an increase in the maximum dry density (MDD) value and a decrease in the OMC. Read the entire page →
From page 104... ... 104 categories: (1) aggregate material and layer characteristics and (2) Read the entire page →
From page 105... ... 105 be varied to achieve the required compactive energy. Sometimes the wheels are mounted slightly out of line with the axle, giving them a weaving action and the name "wobble wheel." This condition improves the kneading action on the layer being compacted. Read the entire page →
From page 106... ... 106 Direct Methods for Measuring Moisture Content The oven dry method, the microwave oven method, the direct heating method, and the calcium carbide gas pressure tester method ("speedy moisture content") are examples of methods used to make gravimetric moisture measurements during pavement construction. Read the entire page →
From page 109... ... 109 Of the previously listed devices, the FWD is the most commonly used device by transportation agencies for indirectly measuring (or backcalculating from measured deflections) the in-service pavement layer moduli. Read the entire page →
From page 110... ... 110 MODULUS-BASED COMPACTION CONTROL Need for Modulus-Based Compaction Control Although the measurement of the dry unit weight and moisture content of constructed UAB/subbase layers is relatively straightforward and practical, it does not provide any direct indication about the layer modulus or shear strength. Moreover, it is important to note that the same density can be obtained for at least two different moisture contents on either side of the compaction (moisture-density) Read the entire page →
From page 111... ... 111 NCHRP Project 21-09, Intelligent Soil Compaction Systems, listed the following as desirable features of an IC system: (1) continuous assessment of mechanistic soil properties (e.g., stiffness, modulus) Read the entire page →
From page 112... ... 112 Synthesis of Past Research and Agency Experience with IC Systems Several research and trial projects have been conducted in the United States evaluating the application of IC systems as QC tools for UAB/subbase layer construction. Most notably, a Transportation Pooled Fund project, TPF-5(128) Read the entire page →
From page 113... ... 113 an instrumented vibratory roller for the QC/QA of HMA mixtures and unbound pavement layers. Through comparison of the IC response output parameters with modulus and density values measured using traditional as well as nondestructive testing devices, it was observed that the IC equipment was successful in detecting areas with significant density differences. Read the entire page →
From page 114... ... 114 increase contractor and agency personnel's confidence in using the IC technology. Details on several other IC implementation projects were provided in Chang et al. Read the entire page →
From page 115... ... 115 the layered base over subgrade. The measured deviator stress (q) Read the entire page →
From page 116... ... 116 CONSIDERATION OF SUCTION EFFECTS IN LAYER MODULUS ESTIMATION Background The modulus (and, correspondingly, the load response linked to performance) of earthwork and unbound aggregates is strongly influenced by the seasonal variation of their moisture content. Read the entire page →
From page 117... ... 117 a wide measurement range, is easily automated, and is not affected by salinity. The limitations include hysteresis, individual sensor calibration, and long equilibrium times. Read the entire page →
From page 118... ... 118 Munoz-Carpena, R., "Field Devices for Monitoring Soil Water Content," University of Florida IFAS Extension, 2009. Nazzal, M., Field Evaluation of In situ Test Technology for QC/QA Procedures during Construction of Pavement Layers and Embankments, MS Thesis, Louisiana State University, Baton Rouge, 2003. Read the entire page →

From page 101...

... 101 chapter five COMPACTION, QUALITY CONTROL, AND FIELD PERFORMANCE INTRODUCTION This chapter presents detailed findings on different approaches used by transportation agencies for compaction testing on laboratory samples, field compaction, QC/QA, and field performance evaluations of constructed UAB/subbase layers. Different aspects of compaction and QC of UAB and subbase construction are discussed by first introducing the theory of compaction along with the objectives behind compacting unbound aggregate pavement layers.