Evaluation Study of Pit Run Gravel Asphalt Treated Base Mixtures with Various Percentages of Crushed Limestone, R-217, 1968

In November of 1966, an investigation of the rigid Class I asphalt treated base specification, requiring 70 per cent crushed limestone, was initiated. It was felt that it might be possible to modify the need for crushed particles, in the construction of basis on heavy duty roads, at a savings, by using more local materials, without sacrificing strength and/or durability. This is a short study on typical sources of pit run gravel, with various percentages of limestone. It is conducted with an eye open to the possibility that our specifications may be modified. The possibility that further investigation may be desirable is not ignored.

Evaluation of Cohesion and Swell Characteristics of Asphalt Treated Base Mixtures, R-223, 1968

This study was undertaken to evaluate the suitability of various stones which play an important role in the properties of compacted mixtures in asphalt treated bases. The determination of the effect of water temperature on the cohesion of the mixes is investigated. A number of stones were prepared for the test. Attention is paid to the particular source of stone with the corresponding test results. A preliminary study of the effect of lime when added to mixed aggregate was also conducted. The purpose of this study is to provide needed information on the cohesive characteristics of asphalt treated bases using a wide range of stones. This study is also to evaluate the suitability of the various stone sources.

Determination of the Optimum Base Characteristics for Pavements, TR-482, 2004

In recent years, it has become apparent that the design and maintenance of pavement drainage extends the service life of pavements. Most pavement structures now incorporate subsurface layers. Part of the function of these subsurface layers is to drain away excess water, which can be extremely deleterious to the life of the pavement. To assure the effectiveness of such drainage layers after they have been spread and compacted, simple, rapid, in-situ permeability and stability testing and end-result specification are needed. This report includes conclusions and recommendations related to four main study objectives: (1) Determine the optimal range for in-place stability and in-place permeability based on Iowa aggregate sources; (2) Evaluate the feasibility of an air permeameter for determining the permeability of open and well-graded drainage layers in situ; (3) Develop reliable end-result quality control/quality assurance specifications for stability and permeability; and (4) Refine aggregate placement and construction methods to optimize uniformity.

Factors Influencing Stability of Granular Base Course Mixes, Progress Report, HR-99, 1965

The problems of laboratory compaction procedures, the effect of gradation and mineralogy on shearing strength, and effect of stabilizing agents on shearing strength of granular base course mixes are discussed. For the materials tested, a suitable laboratory compaction procedure was developed which involves the use of a vibratory table to prepare triaxial test specimens. A computer program has been developed to facilitate the analysis of the test data of the effect of gradation and mineralogy on shearing strength of soils. The effects of the following materials have been selected for evaluation as stabilizing agents’ portland cement, sodium and calcium chloride, lime organic cationic waterproofer, and asphaltic materials.

Factors Influencing Stability of Granular Base Course Mixes, Progress Report, HR-99, 1964 (April)

The problems of laboratory compaction procedures, the effect of gradation and mineralogy on shearing strength, and effect of stabilizing agents on shearing strength of granular base course mixes are discussed. For the materials tested, a suitable laboratory compaction procedure was developed which involves the use of a vibratory table to prepare triaxial test specimens. A computer program has been developed to facilitate the analysis of the test data of the effect of gradation and mineralogy on shearing strength of soils. The effects of the following materials have been selected for evaluation as stabilizing agents’ portland cement, sodium and calcium chloride, lime organic cationic waterproofer, and asphaltic materials.

Factors Influencing Stability of Granular Base Course Mixes, Progress Report, HR-99, 1964 (November)

The problems of laboratory compaction procedures, the effect of gradation and mineralogy on shearing strength, and effect of stabilizing agents on shearing strength of granular base course mixes are discussed. For the materials tested, a suitable laboratory compaction procedure was developed which involves the use of a vibratory table to prepare triaxial test specimens. A computer program has been developed to facilitate the analysis of the test data of the effect of gradation and mineralogy on shearing strength of soils. The effects of the following materials have been selected for evaluation as stabilizing agents’ portland cement, sodium and calcium chloride, lime organic cationic waterproofer, and asphaltic materials.

Lime or Chloride Treatment of Granular Base Course Materials, HR-99

Results are presented of triaxial testing of three crushed limestones to which either hydrated high-calcium lime, sodium chloride or calcium chloride had been added. Lime was added at rates of 1, 3, 10 and 16 percent, chlorides were added at 0.5 percent rate only. Speciments were compacted using vibratory compaction apparatus and were tested in triaxial compression using lateral pressures from 10 to 100 psi. Triaxial test results indicate that: (1) sodium chloride slightly decreased the angle of internal friction and increased cohesion, (2) calcium chloride slightly increased the angle of internal friction and decreased cohesion, and (3) lime had no appreciable effect on angle of internal friction but increased cohesion, decreased density and increased pore water pressure.

Improvement of Granular Base Course Materials with Portland Cement, Special Report, HR-99

A highway base course may be defined as a layer of granular material which lies immediately below the wearing surface of a pavement and must possess high resistance to deformation in order to withstand pressures imposed by traffic. A material commonly used for base course construction is crushed limestone. Sources of limestone, acceptable for highway bases in the state of Iowa, occur almost entirely in the Pennsylvanian, Mississippian and Devonian strata. Performance records of the latter two have been quite good, while material from the Pennsylvanian stratum has failed on numerous occasions. The study reported herein is one segment of an extensive research program on compacted crushed limestone used for flexible highway base courses. The primary goals of the total study are: 1. Determination of a suitable and realistic laboratory method of compaction. 2. Effect of gradation, and mineralogy of the fines, on shearing strength. 3. Possible improvement of the shear strength with organic and inorganic chemical stabilization additives. Although the study reported herein deals primarily with the third goal, information gathered from work on the first two was required for this investigation. The primary goal of this study was the evaluation of various factors of stability of three crushed limestones when treated with small amounts of type I Portland cement. Investigation of the untreated materials has indicated that shear strength alone is not the controlling factor for stability of crushed stone bases. Thus the following observations were made in addition to shear strength parameters, to more adequately ascertain the stability of the cement treated materials: 1. Volume change during consolidation and shear testing. 2. Pore pressure during shear. The consolidated-undrained triaxial shear test was used for determination of the above factors.