Browsing by Subject "Properties of materials"
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Item An Experimental Study on the Guidelines for Using Higher Contents of Aggregate Microfines in Portland Cement Concrete(2001-12) Fowler, David W.; Ahn, Nam-ShikThe use of manufactured fine aggregate (MFA) in portland cement concrete becomes more common as sources of natural sands are depleted. There is a great need to utilize MFA better, particularly the minus 75µm sizes. The development of specifications that aid aggregates producers, engineers, and specifying agencies in the utilization of MFA is of interest to many parties. Better utilization of crushed aggregates has both economic and environmental benefits for the construction and materials industry. This report presents some of the effects of high-fines on the properties of cement mortar and concrete. A total of 50 sands were used in this mortar study, 10 of which were included in the concrete research. A summary of aggregate characteristics that affect the properties of mortar and concrete are presented along with the correlations evaluated between these properties.Item Framework for Development of a Classification Procedure for Use of Aggregate Fines in Concrete(2001-10) Zollinger, Dan G. , 1952-; Sarkar, Shondeep L.Although data on use of aggregate fines in portland cement concrete are largely very encouraging, there is a lack of proper definition, and knowledge regarding nature, and characteristics of different aggregate fines, their properties, and effects on portland cement concrete. The focus of this project was to examine the methods and test procedures used in the past to characterize the properties of fines, and develop, on a preliminary basis, a framework to characterize and catalogue the properties of aggregate fines, propose new ones that would eventually complement a set of guidelines for the use of aggregate fines in portland cement concrete. A test run of this classification process is provided as a demonstration of its utility to distinguish aggregate fines possessing different properties and characteristics. Possible applications of aggregate fines, such as in high-performance concrete, controlled low strength materials, and insulated concrete forms are discussed as future directions of research.Item Rapid Test to Establish Grading of Unbound Aggregate Products: Automation of Aggregate Characterization Using Laser Profiling and Digital Image Analysis(2002-06) Haas, Carl T. (Carl Thomas); Rauch, Alan F.; Kim, Hyoungkwan; Browne, CraigThis final project report describes the development of a laser scanning device for measuring the gradation and other morphological characteristics of unbound construction aggregates. The device is called the LASS, for "Laser-based Aggregate Scanning System." The method of characterizing aggregate particles from three-dimensional (3D) laser profiling required the development of particle segmentation algorithms, particle measurement algorithms, and generalized particle descriptions. With the LASS, true 3D data of aggregate particles are obtained by laser profiling. This data is first transformed into digital images. Second, segmentation and particle measurement algorithms separate the particles and process each particle data individually with the aid of various digital image technologies. Finally, in order to provide a generalized, quantitative, and representative way to characterize aggregate particles, 3D particle descriptors were developed using the multi-resolution analysis feature of wavelet transforms. Verification tests show that this approach can characterize various aggregate properties in a fast, accurate, and reliable way. When implemented, this ability to automatically analyze multiple characteristics of an aggregate sample will lead to reduced labor costs in the laboratory, but more importantly, to better control of the quality of aggregate products. ICAT Project 503 was undertaken to study rapid, automated methods of determining the grain size distribution of unbound aggregate products. Automatic measurement of particle size and shape properties has the potential to overcome problems with manual measurements such as subjectivity, labor intensity, and slow speed. Testing machines that rely on 2D digital image analysis were evaluated as described earlier in Report ICAR 503-2.Item Structural Characteristics of Unbound Aggregate Bases to Meet AASHTO 2002 Design Requirements: Interim Report(2001-07) Adu-Osei, Alex; Little, Dallas N.; Lytton, Robert L.This report gives the results of a study of the properties of unbound aggregate base materials using both laboratory testing data from full scale field tests in Illinois, Georgia, and Texas, and a model of cross-anisotropic elastic materials to characterize the behavior of the base materials under traffic loads. Using the cross-anisotropic model, the stress distribution in a base course is more realistic than that developed when the aggregate base is considered to be linear and isotropic. The stress distribution based on cross-anisotropic analysis is not only more correct, but it is also more favorable to the unbound aggregate in that significant tensile stresses are found not to occur. The analogy is presented in this report that the response of the aggregate base to the load is as if the stress distribution directly under the wheel load due to anisotropy acts as a moving column under the wheel in which the aggregate essentially produces its own confinement and does not enter into tension. Other findings in this report include the following: 1) The unbound aggregate base material should be modeled as non-linear and cross-anisotropic to account for stress-sensitivity and the significant differences between vertical and horizontal moduli and Poisson’s ratios. 2) The ICAR laboratory testing protocol is efficient and precise and should be considered as a candidate to model the unbound aggregate base. The protocol uses three stress regimes and ten stress levels within each regime to determine stress sensitivity and cross-anisotropy. A system identification method is used to select the five material properties based on the tests results necessary to properly characterize the aggregate base and to satisfy the requirements of elastic work potential theory. 3) The Fast Industrial Process Controls cell is efficient and should be used to characterize unbound aggregate bases. The ratio of the diameter to the specimen height is 1:1. While testing of such sample sizes is discouraged in the literature, improvements made to the IPC cell minimize frictional development between the sample and loading platens resulting in minimal constraint at the sample ends. This is verified in the report based on comparative triaxial testing and finite element analysis. 4) The ICAR testing protocol is an excellent tool for both unbound aggregate characterization and comparative analysis of materials. A compaction study on two very different aggregates (uncrushed river gravel and crushed limestone) was performed in which the aggregates were subjected to impact, kneading gyratory compaction. The difference in the tendency of the compaction techniques to produce varying levels of particle orientation (which affects anisotropy) was evident in the degree of anisotropy measured.Item Use of High Fines Concrete (HFC) in Insulated Concrete Form (ICF) Construction(2001-09) Zollinger, Dan G. , 1952-This project work consisted of developing technical data to justify, from the standpoint of material properties (of aggregate fines and HFC), construction efficiency, cost competitiveness, and energy performance, a basis for the use of high-fines concrete (HFC) inside ICF wall systems. Although several aspects of the study are listed above, the report primarily concentrates on the material aspects of a limited number of aggregate fines sources and their use in HFC relative to strength development and placeability. Originally, emphasis was planned to be placed upon the use of a controlled low strength material (CLSM) but due to strength requirements currently in force for ICF construction, it was determined that greater benefit would be derived from highlighting the advantages of using aggregate fines in ICF concrete. A framework for developing suitable HFC mixture designs for different ICF wall systems relative to placement and strength characteristics is discussed. These guidelines were based upon results from the construction to two residential structures using HFC and the placement of 4 trial wall systems. One of the structures consisted of a “test model” that was used to investigate methods of construction and the energy efficiency of an ICF wall system.