Carbonate Rock Pore Size Distribution Determination through Iowa Pore Index Testing, MLR-15-01, 2015

The Iowa Pore Index (IPI) measures the pore system of carbonate (limestone and dolomite) rocks using pressurized water to infiltrate the pore system. This technique provides quantitative results for the primary and capillary (secondary) pores in carbonate rocks. These results are used in conjunction with chemical and mineralogical test results to calculate a quality number, which is used as a predictor of aggregate performance in Portland cement concrete (PCC) leading to the durability classification of the aggregate. This study had two main objectives: to determine the effect different aggregate size has on IPI test results and to establish the precision of IPI test and test apparatus. It was found that smaller aggregate size fractions could be correlated to the standard 1/2”-3/4” size sample. Generally, a particle size decrease was accompanied by a slight decrease in IPI values. The IPI testing also showed fairly good agreement of the secondary pore index number between the 1/2”-3/4”and the 3/8”-1/2” fraction. The #4-3/8” showed a greater difference of the secondary number from the 1/2”-3/4” fraction. The precision of the IPI test was established as a standard deviation (Sr) of 2.85 (Primary) and 0.87 (Secondary) with a repeatability limit (%r) of 8.5% and 14.9% for the primary and secondary values, respectively.

Self-Consolidating Concrete—Applications for Slip-Form Paving: Phase I (Feasibility Study), 2005

Over-consolidation is often visible as longitudinal vibrator trails in the surface of concrete pavements constructed using slip-form paving. Concrete research and practice have shown that concrete material selection and mix design can be tailored to provide a good compaction without the need for vibration. However, a challenge in developing self-consolidating concrete for slip-form paving (SF SCC) is that the new SF SCC needs to possess not only excellent self-compactibility and stability before extrusion, but also sufficient “green” strength after extrusion, while the concrete is still in a plastic state. The SF SCC to be developed will not be as fluid as the conventional SCC, but it will (1) be workable enough for machine placement, (2) be self-compacting with minimum segregation, (3) hold shape after extrusion from a paver, and (4) have performance properties (strength and durability) compatible to current pavement concrete. The overall objective of this project is to develop a new type of SCC for slip-form paving to produce more workable concrete and smoother pavements, better consolidation of the plastic concrete, and higher rates of production. Phase I demonstrated the feasibility of designing a new type of SF SCC that can not only self-consolidate, but also have sufficient green strength. In this phase, a good balance between flowability and shape stability was achieved by adopting and modifying the mix design of self-consolidating concrete to provide a high content of fine materials in the fresh concrete. It was shown that both the addition of fine particles and the modification of the type of plasticizer significantly improve fresh concrete flowability. The mixes used in this phase were also found to have very good shape stability in the fresh state. Phase II will focus on developing a SF SCC mix design in the lab and a performing a trial of the SF SCC in the field. Phase III will include field study, performance monitoring, and technology transfer.

Methods to Increase Durability of Reactive ("D" Cracking) Coarse Aggregate in Portland Cement Concrete, MLR-73-01, 1973

The coarse aggregates used for Portland Cement concrete in southwest Iowa have exhibited a poor serviceability. This early failure is attributed to a characteristic commonly referred as "D" cracking. "D" line cracking is a discolored area of concrete caused by many fine, parallel hairline cracks. "D" line cracking is primarily caused by the movement of water in and through coarse aggregate with a unique pore structure. The presence of the water in the aggregates at the time of freezing causes the "D" cracking to occur and early failure. By making the pore structure less permeable to moisture, it is thought the durability factor of the concrete should increase. By drying the aggregate before mixing and then mixing with the cement, the particles of cement should enter the outer pore structure, and upon hydration make the pore structure less permeable to moisture.

An Investigation of Emulsion Stabilized Limestone Screenings, HR-309, 1989

During the processing of limestone to produce commercial aggregates, a significant amount of waste limestone screenings is produced. This waste material cannot be used in highway construction because it does not meet current highway specifications. The purpose of this research was to determine if a waste limestone screenings/emulsion mix could be used to construct a base capable of supporting local traffic. A 1.27 mile section of roadway in Linn County was selected for this research. The road was divided into seven sections. Six of the sections were used to test 4" and 6" compacted base thicknesses containing 2.5%, 3.5%, and 4.5% residual asphalt contents. The seventh section was a control section containing untreated waste limestone screenings.

The Effect of Deicing Salt on Aggregate Durability, Progress Report HR-266, 1985

The Iowa DOT has been using rapid freezing in air and thawing in water to evaluate coarse aggregate durability in concrete since 1962. Earlier research had shown that the aggregate pore system was a major factor in susceptibility to D-cracking rapid deterioration. There are cases were service records show rapid deterioration of concrete containing certain aggregates on heavily salted primary roads and relatively good performance with the same aggregate in secondary pavements with limited use of deicing salt. A five-cycle salt treatment of the coarse aggregate prior to durability testing has yielded durability factors that correlate with aggregate service records on heavily salted primary pavements. X-ray fluorescence analyses have shown that sulfur contents correlate well with aggregate durabilities with higher sulfur contents producing poor durability. Trial additives that affect the salt treatment durabilities would indicate that one factor in the rapid deterioration mechanism is an adverse chemical reaction. The objective· of the current research is to develop a simple method of determining aggregate susceptibility to salt related deterioration. This method of evaluation includes analyses of both the pore system and chemical composition.

Investigation of Rapid Thermal Analysis Procedures for Prediction of the Service Life of PCCP Carbonate Coarse Aggregate: Phase I, Progress Report, HR-337, 1992

The major objective of this research project is to utilize thermal analysis techniques in conjunction with x-ray analysis methods to identify and explain chemical reactions that promote aggregate related deterioration in Portland cement concrete. The first year of this project has been spent obtaining and analyzing limestone and dolomite samples that exhibit a wide range of field service performance. Most of the samples chosen for the study also had laboratory durability test information (ASTM C 666, method B) that was readily available. Preliminary test results indicate that a strong relationship exists between the average crystallite size of the limestone (calcite) specimens and their apparent decomposition temperatures as measured by thermogravimetric analysis. Also, premature weight loss in the thermogravimetric analysis tests appeared to be related to the apparent decomposition temperature of the various calcite test specimens.

Ammonium Phosphate/Fly Ash Road Base Construction, HR-294, Construction Report, 1987

The objective of this research project was to evaluate the construction and service performance of ammonium phosphate/fly ash (APFA) treated base courses of crushed fines and/or unprocessed sand. Specific test results related to construction of the test sections were included in the 1987 construction report by Iowa State University. The performance of the experimental sections is dealt with in this final report. This 1986 project demonstrated that in all cases the control sections utilizing a Type B base experienced dramatically less cracking in the surface than the APFA treated base sections. The cost per mix and subsequent surface maintenance costs for the APFA base sections, especially those having a substantial amount of limestone, were higher than the Type B base control sections. This type of construction may prove to be economical only when petroleum product costs escalate.

Granular Base Materials for Flexible Pavements, HR-131, 1970

The coefficients of relative strength (CORS) of base courses for use in the American association state highway officials (AASHO) interim guide for the design of flexible pavements are determined here. Based on (1) volumetric strain--axial strain relationships at minimum volume, and (2) effective stress ratio-cohesion relationships at maximum effective stress ratio, CORS were determined from the results of laboratory triaxial tests on both asphalt-treated and untreated aggregate base course materials. The researchers conclude that volumetric strain-axial strain at minimum volume appear to be appropriate parameters for determining CORS.

The Relationship of Aggregate Durability to Trace Element Content, Interim Report, HR-266, 1984

This report is a brief overview of the recent Iowa Department of Transportation research in the area of durability of Portland cement, concrete under the direction of Wendeli Dubberke. Present plans are to publish a more detailed report on low Portland cement concrete- durability research in January, 1985.

Investigation of PCC Pavement Deterioration: A Few Facts are Worth More than 100 Opinions, Interim Report, HR-2074, 1995

Portland Cement Concrete (PCC) pavement has served the State of Iowa well for many years. The oldest Iowa pavement was placed in LeMars in 1904. Beginning in 1931, many miles of PCC pavement were built to "get out of the mud.” Many of these early pavements provided good performance without deterioration for more than 50 years. In the late 1950's, Iowa was faced with severe PCC pavement deterioration referred to as D cracking. Research identified the cause of this deterioration as crushed limestone containing a bad pore system. Selective quarrying and ledge control has alleviated this problem. In 1990, cracking deterioration was identified on a three year old pavement on us 20 in central Iowa. The coarse aggregate was a crushed limestone with an excellent history of performance in PCC pavement. Examination of cores showed very few cracks through the coarse aggregate particles. The cracks were predominately confined to the matrix. The deterioration was identified as alkali-silica reactivity (ASR) by a consultant.

Absorption of Asphalt by Aggregate, HR-142, Progress Report, 1970

This report summarizes work accomplished under Project HR-142 during the period from January 1, 1969 to December 31, 1969. Pore characteristics of six limestones were studied in relation to their absorption of two asphalt cements. Porosity and pore size distribution were determined by a mercury penetration porosimeter and asphalt absorption was determined by immersion and bulk-impregnated specific gravity methods. A special study was conducted to develop new, simple and more reproducible methods for bulk specific gravity determination. As a result, a new chemical indicator method was developed to determine the saturated surface-dry condition, and a glass mercury pycnometer was designed to determine coarse·and fine aggregates. Asphalt absorption history of one asphalt mixture on campus has been studied since September 1968. Chemical and/or radiation treatments of absorptive aggregates were conducted on four chemicals and two aggregates.

Shear Strength of Granular Materials, 1967

A theory was developed to allow the separate determination of the effects of the interparticle friction and interlocking of particles on the shearing resistance and deformational behavior of granular materials. The derived parameter, angle of solid friction, is independent of the type of shear test, stress history, porosity and the level of confining pressure, and depends solely upon the nature of the particle surface. The theory was tested against published data concerning the performance of plane strain, triaxial compression and extension tests on cohesionless soils. The theory also was applied to isotropically consolidated undrained triaxial tests on three crushed limestones prepared by the authors using vibratory compaction. The authors concluded that, (1) the theory allowed the determination of solid friction between particles which was found to depend solely on the nature of the particle surface, (2) the separation of frictional and volume change components of shear strength of granular materials qualitatively corroborated the postulated mechanism of deformation (sliding and rolling of groups of particles over other similar groups with resulting dilatancy of specimen), (3) the influence of void ratio, gradation confining pressure, stress history and type of shear test on shear strength is reflected in values of the omega parameter, and (4) calculation of the coefficient of solid friction allows the establishment of the lower limit of the shear strength of a granular material.

General Aggregate Source Information, 1979

Only those aggregate sources which have been sampled or tested within the last ten years are listed. This listing additionally ranks sources in accordance with a skid resistance classification as defined herein for aggregates used in asphalt construction. The rankings are based on the ledges used in the past for asphalt aggregates. Upon request, new sources or different combinations of beds within an existing source will be evaluated as to their skid resistance classification. This ranking refers only to the skid resistant properties and does not waive the normal quality requirements for the particular type of aggregate indicated in the contract documents.

Influence of aggregates grading and water/cement ratio in workability and hardened properties of mortars

Mortar is the material responsible for the distribution of stresses in masonry structures. The knowledge about the fresh and hardened properties of mortar is fundamental to ensure a good performance of masonry walls. Water/cement ratio and aggregates grading are among several variables that influence physical and mechanical behaviour of mortars. An experimental program is presented in order to evaluate the influence of aggregates grading and water/cement ratio in workability and hardened properties of mortars. Eighteen compositions of mortar are prepared using three relations cement:lime:sand, two types of sand and three water/cement ratios. Specimens are analyzed through flow table test, compressive and flexural strength tests. Results indicate that the increase of water/cement ratio reduces the values of hardened properties and increases the workability. Besides, sands grading has no influence in compressive strength. On the other hand, significant differences in deformation capacity of mortars were verified with the variation of the type of sand. Finally, some correlations are presented among hardened properties and the compressive strength. (C) 2010 Elsevier Ltd. All rights reserved.

Evaluation of the performance and cost-effectiveness of pavement sections containing open-graded base courses

Moisture induced distresses have been the prevalent distress type affecting the deterioration of both asphalt and concrete pavement sections. While various surface techniques have been employed over the years to minimize the ingress of moisture into the pavement structural sections, subsurface drainage components like open-graded base courses remain the best alternative in minimizing the time the pavement structural sections are exposed to saturated conditions. This research therefore focuses on assessing the performance and cost-effectiveness of pavement sections containing both treated and untreated open-graded aggregate base materials. Three common roadway aggregates comprising of two virgin aggregates and one recycled aggregate were investigated using four open-ended gradations and two binder types. Laboratory tests were conducted to determine the hydraulic, mechanical and durability characteristics of treated and untreated open-graded mixes made from these three aggregate types. Results of the experimental program show that for the same gradation and mix design types, limestone samples have the greatest drainage capacity, stability to traffic loads and resistance to degradation from environmental conditions like freeze-thaw. However, depending on the gradation and mix design used, all three aggregate types namely limestone, natural gravel and recycled concrete can meet the minimum coefficient of hydraulic conductivity required for good drainage in most pavements. Tests results for both asphalt and cement treated open-graded samples indicate that a percent air void content within the range of 15-25 will produce a treated open-graded base course with sufficient drainage capacity and also long term stability under both traffic and environmental loads. Using the new Mechanistic and Empirical Design Guide software, computer simulations of pavement performance were conducted on pavement sections containing these open-graded base aggregate base materials to determine how the MEPDG predicted pavement performance is sensitive to drainage. Using three truck traffic levels and four climatic regions, results of the computer simulations indicate that the predicted performance was not sensitive to the drainage characteristics of the open-graded base course. Based on the result of the MEPDG predicted pavement performance, the cost-effectiveness of the pavement sections with open-graded base was computed on the assumption that the increase service life experienced by these sections was attributed to the positive effects of subsurface drainage. The two cost analyses used gave two contrasting results with the one indicating that the inclusion of open-graded base courses can lead to substantial savings.