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48 aggregate sample, but it cannot be used for measuring angu- characteristics can be used to detect changes in these charac- larity or texture. teristics and make appropriate adjustments. This will ensure A methodology that uses direct measurements of shape the supply of aggregates with the desired characteristics, (three dimensions), angularity, and texture was developed to thus leading to good performance and cost savings. classify aggregates based on the distribution of their charac- · Evaluation of crushing methods: crushing methods can teristics. It unifies the methods used to measure the charac- be evaluated by measuring aggregate shape characteristics teristics of fine and coarse aggregates. The analysis methods produced using these methods. This evaluation will help are simple, and the results have physical meanings that can be identify crushing methods that could produce aggregates interpreted easily. The classification ranges were found to be with the desirable characteristics. similar for the different aggregate sizes. This finding simplified · Evaluation of changes in aggregate texture: the proposed the methodology, as one set of ranges is needed irrespective imaging systems can be used to measure the aggregate tex- of aggregate sizes. This classification methodology is valuable ture and its change due to polishing which can be indicative for the interpretation of the results and in order to facilitate of change in frictional characteristics. implementation. The classification results are presented in terms of the dis- The following research projects are recommended to enhance tribution of shape properties within an aggregate sample. This the study findings and their implementation: feature gives capabilities to (1) explore the influence of differ- ent processes such as crushing and blending on aggregate 1. Research to further evaluate the ruggedness of the recom- shape, (2) conduct quality control activities to detect changes in mended test methods. This work is essential to evaluate the distribution of any of the aggregate characteristics, (3) relate the ability of each test method to provide repeatable and the distribution of different characteristics to performance, reproducible results. and (4) develop specifications based on the distribution of 2. Research to develop methods for incorporating aggregate aggregate characteristics rather than average indices. physical properties in the design of pavement materials. Generally, each of the paving mixtures (unbound aggregate layers and layers bound and/or stabilized with asphalt, Applicability and Suggested Research hydraulic cement or other stabilizing material) does not This study provides the pavement community with practical, consider aggregate characteristics, making it difficult to reliable, and accurate methods for rapidly measuring aggregate relate aggregate characteristics on performance. Although characteristics. The recommended methods can be used in the several studies have evaluated the relationship between design of pavement layers, in Quality Control (QC) and Qual- physical characteristics and mixture performance, these ity Assurance (QA) programs, and for problem diagnosis based studies have not developed adaptable specifications that on understanding of the effects of aggregates on performance accommodate variations in aggregate characteristics. of pavement structures. In addition, these methods will help the 3. Research to develop methods for optimizing the design of industry set criteria for providing aggregates with the desired paving mixtures based on the physical properties of aggre- characteristics. gates. This study did not specify performance-based limits The recommended methods can be implemented in the for shape, angularity, and texture that should be used in the following aspects of pavement engineering: mixtures of the different pavement layers. Such research will provide means to allow highway agencies and the industry · QA and QC procedures during aggregate production: to efficiently utilize the available sources of aggregates and statistical parameters based on the distribution of aggregate reduce construction costs.