Stone Aggregate Research Articles

A GIS Analysis to Evaluate Areas Suitable for Crushed Stone Aggregate Quarries in New England, USA

Aggregate is a low unit-value mineral commodity. Costs to move aggregate from the mine site to the point of use is a large fraction of the resource cost to users. Production sites for aggregate occur where suitable source materials exist and where transportation and market conditions are favorable. The increasing demand for aggregate and the difficulty of developing and permitting new sites and of renewal of permits on existing sites of aggregate production indicates that aggregate will be supplied from sources yet to be developed or delineated in many areas. Site development and permitting for aggregate production is difficult because many land management plans and zoning actions fail to anticipate prospective source areas for aggregate in a way that is consistent with both the source rock quality and the transportation and socioeconomic factors that define the economic viability of the industry. Spatial analysis provides a method to integrate both geology and economic (transportation and marketplace) parameters in a regional model. Weights of evidence (WofE) analysis has been used to measure the spatial correlation of geologic map, transportation network, and population data with current production sites for crushed stone aggregate in the New England region of the northeastern United States. Weighted logistic regression (WLR) is used with the WofE results to rank areas in terms of their relative suitability for production of crushed stone. Spatial analysis indicates that 85% of the 106 crushed stone aggregate quarries in New England are sited within 1.6 km (1 mile) of either a principal highway or rail line in the region. Seventy-eight percent of crushed stone aggregate quarries are sited in census tracts with population densities exceeding 100 people/mile2. These relations illustrate the importance of proximity to both transportation corridors and developing areas where aggregate is predominately used. Only one active crushed stone quarry is located in a census tract with a population density less than 15 people/mile2, reflecting the lack of sufficient market demand in many rural areas to develop an operation there. However, since 1990, almost all new quarries have been developed in census tracts with population densities less than 200 people/mile2, indicating the difficulty of permitting new quarry sites in highly populated areas. Crushed stone aggregate is produced predominately from three hard rock types that are distributed widely in New England; 28% of sites use granitic rock, 25% use carbonate rocks, and 25% use mafic rock types that are categorized as trap rock by the aggregate industry. The other crushed stone aggregate sources include a variety of fine-grained metamorphic rock types. Carbonate rocks and Jurassic basalt (the primary trap rock source) are the most prevalent source rocks on an area-weighted basis. Spatial analysis can be used on a regional scale to rank areas by their relative suitabilityfor crushed stone aggregate production based on geology, transportation, and population parameters. The results of this regional analysis can identify areas for more detailed evaluation. As transportation or population features change, the model can be revised easily to reflect these changes.

A STUDY ON MIX DESIGN PROCEDURE OF LARGE STONE ASPHALT MIXTURE

In this research, a design procedure of large stone asphalt mixture, which is superior in plastic flow resistance, was discussed. The feature points of the design procedure are as follows. 1) Large stone aggregate, top size of 30 mm, was mainly mixed. 2) The mix proportion was decided in focusing matrix structure of the top size coarse aggregate. 3) A gyratory compactor was used for specimen compaction. From the results, it was found that the mix proportion with No. 4-sized and No. 7-sized crushed stone has a good matrix structure of the coarse aggregate. And it was also confirmed that this mixture has high efficiency in flow resistance and abrasion resistance as compared with past large stone mixtures.

Concrete from an agricultural waste-oil palm shell (OPS)

Wastes are produced in large quantities from agro-based industries and the use of these waste materials in construction industry would contribute towards a cleaner environment. It also results in a cost effective construction material. A concrete using oil palm shell (OPS) as coarse aggregate has been found useful as structural concrete. As the bulk density of OPS is much less than stone aggregate OPS concrete becomes a lightweight concrete with a density of about 1850 kg/ m 3 . The compressive strengths of OPS concrete range from 20 to 24 N/ mm 2 for 28 days; this satisfies the strength requirement of structural lightweight concrete. A test on concrete floor slab using OPS concrete is also discussed.

Automated Quality Assessment of Stone Aggregates Based on Laser Imaging and a Neural Network

An automated quality assessment technique is proposed for rapidly detecting excessive size variations during the production of stone aggregates. The system uses a laser profiler to scan collections of aggregate particles and obtain three-dimensional data points on the particle surfaces. For computational efficiency, the resulting data are converted into digital images. Wavelet transforms are then applied to the images to extract features indicative of the material gradation. These wavelet-based features are used as inputs to an artificial neural network, which is trained to classify the aggregate sample. Taken together, these components form a neural network-based classification system that can determine whether or not an aggregate product is in compliance with a given specification. Verification tests show that this approach could potentially help to determine, in an accurate and fast (real-time) manner, when adjustments or repairs to the production equipment are needed.

Performance Evaluation of Automated Machines for Measuring Gradation of Aggregates

Abstract Several automated devices are commercially available for measuring the gradation of stone aggregates. These computerized machines, which provide a rapid alternative to manual sieving, capture and process two-dimensional digital images of aggregate particles to determine grain size distribution. Five of these automated gradation devices were evaluated for accuracy using fifteen aggregate test samples. To quantify how well the machine results compare with data from standard sieve analyses, the CANWE (Cumulative And Normalized Weighted Error) statistic was developed and used. While the machine data did not match the sieve data exactly, the evaluated devices were found to provide good measures of particle gradation for most samples. These tests also indicate that some machines will give more repeatable results in multiple tests of a given material, while others yield better results when testing different materials. The methodology used in this study is suitable for objectively evaluating the accuracy of other rapid gradation machines for various applications.

Application of Construction and Building Debris as Base and Subbase Materials in Rigid Pavement

This research presents the test results of a laboratory and field study performed to investigate the characteristics and performance of dry and wet recycled concrete aggregate (RCA) as base and subbase materials for concrete pavement. The physical properties of the RCA were investigated in terms of the moisture-density relationship, particle index, and fine aggregate angularity. Performance concerns have focused on compactibility, stability, shear resistance, and particle breakage of the RCA. These were evaluated in the laboratory using the U.S. Army Corps of Engineers Gyratory Testing Machine. The falling weight deflectometer was used to measure the deflection of pavement sections constructed with RCA base and subbase in the subbase material and may be comparable to crushed stone aggregate.

3D Image Segmentation of Aggregates from Laser Profiling

Abstract: In digital imaging of discrete particles, such as stone aggregates, segmentation is one of the most important processes. Automated scanners of different designs use cameras or lasers to obtain digital images of groups of aggregate particles. To accurately determine particle size and shape parameters, each particle region in the image must be isolated and processed individually. Here, a method for segmenting a particle image acquired from laser profiling is developed using a Canny edge detector and a watershed transformation. Canny edges with rigorous and liberal threshold values are used to outline particle boundaries on a binary image and to check the validity of watersheds, respectively. To find appropriate regional minima in the watershed transformation, a varying search window method is used, where the number of neighboring pixels being compared with the pixel of interest is determined from the height value of the pixel. Test results with this method are promising. When implemented in automated systems that are designed to rapidly assess size and shape characteristics of stone particles, this technique can not only reduce the amount of time required for aggregate preparation, but also increase the accuracy of analysis results.

Soil recovery from human disturbance in tropical woodlands in Hong Kong

Villages in the countryside hinterland of Hong Kong traditionally preserve small remnant woodlands for utilitarian and spiritual reasons. In the territory, these remnants often furnish the most natural ecosystems with rich biodiversity. Some sites have been preserved, whereas others have been subject to different uses, and subsequently secondary woodland has reestablished. This study evaluates woodland and human influences on soil properties, and soil recovery after woodland rejuvenation. At nine sites, four classified as less disturbed (LD) and five as more disturbed (MD), physical and chemical properties are similar to those of impoverished humid-tropical soils. However, the MD samples have greater stone content and aggregate stability than the LD. MD samples also have higher pH, lower C/N ratios, more exchangeable Ca and Mg, and higher base saturation. The MD soil properties are attributed to tree felling in the 1940s and short-lived conversion to farmland or orchard, followed by secondary woodland succession dominated by native broadleaf trees. Two MD sites, one converted to an urban park in 1970 and the other burnt by a severe hill fire in 1999, have soil imprints of drastic disturbance. The nutrient content of MD soils at this early stage of ecosystem succession suggests rapid accumulation of nutrients. Five decades of secondary succession at three of the MD sites have resulted in natural soil rehabilitation. Conservation of these ecologically valuable woodlands should avoid unnecessary silvicultural inputs such as planting exotic species and soil disturbance, and conversion to unnatural uses such as recreational sites. In addition, the soils should be managed for improvement to help ecosystem recuperation.

Comparison of properties of steel slag and crushed limestone aggregate concretes

Steel slag is produced as a by-product during the oxidation of steel pellets in an electric arc furnace. This by-product that mainly consists of calcium carbonate is broken down to smaller sizes to be used as aggregates in asphalt and concrete. They are particularly useful in areas where good-quality aggregate is scarce. This research study was conducted to evaluate the mechanical properties and durability characteristics of steel slag aggregate concrete in comparison with the crushed limestone stone aggregate concrete. The durability performance of both steel slag and crushed limestone aggregate concretes was evaluated by assessing water permeability, pulse velocity, dimensional stability and reinforcement corrosion. The results indicated that the durability characteristics of steel slag cement concretes were better than those of crushed limestone aggregate concrete. Similarly, some of the physical properties of steel slag aggregate concrete were better than those of crushed limestone aggregate concrete, though the unit weight of the former was more than that of the latter.

Influence of grout proportions on modulus of elasticity of two-stage concrete

The modulus of elasticity value is important from the design point of view but it is time-consuming in direct measurement. For normal concrete, it is found that the modulus of elasticity can be satisfactorily predicted from the compressive strength value, which is obtained very easily. In the case of two-stage concrete (TSC) there is no background information for evaluating its elastic modulus. The TSC differs from the conventional concrete in a higher percentage content of the stone aggregate. The aggregate is deposited directly into the moulds with point-to-point contact and a high flow grout is then introduced into the bottom of the mould. The contact stresses are transferred first through the stone skeleton and then after deformations of grains, also through the hardened grout. Therefore the properties of the TSC are more dependent upon the stone aggregate. Thus, the characteristics of the TSC in failure conditions are different from the normal concrete. The objective of this research was to present the influence of the grout proportions on the elastic modulus of the TSC observed during compressive tests.

Influence of grout proportions on modulus of elasticity of two-stage concrete

The modulus of elasticity value is important from the design point of view but it is time-consuming in direct measurement. For normal concrete, it is found that the modulus of elasticity can be satisfactorily predicted from the compressive strength value, which is obtained very easily. In the case of two-stage concrete (TSC) there is no background information for evaluating its elastic modulus. The TSC differs from the conventional concrete in a higher percentage content of the stone aggregate. The aggregate is deposited directly into the moulds with point-to-point contact and a high flow grout is then introduced into the bottom of the mould. The contact stresses are transferred first through the stone skeleton and then after deformations of grains, also through the hardened grout. Therefore the properties of the TSC are more dependent upon the stone aggregate. Thus, the characteristics of the TSC in failure conditions are different from the normal concrete. The objective of this research was to present the influence of the grout proportions on the elastic modulus of the TSC observed during compressive tests.

Dimensional Ratios for Stone Aggregates from Three-Dimensional Laser Scans

The ''laser-based aggregate scanning system'' ~LASS! was developed to rapidly and accurately characterize the three- dimensional shape properties of unbound stone aggregates. A linear motion slide, a laser line scanner, and an integrated computer constitute the hardware of the LASS. Using profile data obtained from laser scans of aggregate particles spread out on a platform, the LASS software virtually rotates each irregularly shaped particle to determine the three principal dimensions used to characterize particle shape. The computational method employed can rapidly process the scanned data without losing critical information. Two hundred randomly selected particles, which have variable material and shape characteristics, were manually measured to obtain data that were then used to verify the accuracy of the LASS results. Good correlation with the manual measurements demonstrates that laser profiling has the potential to be a powerful tool for rapidly analyzing the dimensions of irregularly shaped objects, and could be used for quality-control testing and performance-related characterization of stone aggregate materials.

Extracorporeal shock wave lithotripsy of pancreatic duct stones using the Healthtronics LithoTron lithotriptor and the Dornier HM3 lithotripsy machine.

Pancreatic duct stones, which are most often a result of alcohol induced chronic pancreatitis, can lead to chronic abdominal pain, pseudocysts, and exocrine and endocrine failure of the pancreas. Others have reported success using extracorporeal shock wave lithotripsy (ESWL) (Dornier Medical Systems, Inc., Marietta, Georgia) for pancreatic stones. We report our experience with pancreatic ESWL using the LithoTron (Healthtronics, Marietta, Georgia) and HM3 (Dornier) lithotripsy machines. We performed pancreatic ESWL in 23 patients in 4 years, including in 12 with the LithoTron and in 11 with the HM3. After ESWL endoscopic retrograde cholangio-pancreatography (ERCP) was performed in all cases. Stone-free status was defined as no stone fragments visualized or the elimination of all post-ESWL stones by ERCP. Stone-free status was documented in 83% and 82% of patients treated with the LithoTron and HM3, respectively, and 2 per group later required open surgical intervention. There were no changes in pancreatic enzymes and no cases of sepsis or fever after ERCP. In association with post-procedure ERCP pancreatic ESWL is an effective and safe procedure that enables patients with obstructing pancreatic duct stones recalcitrant to primary endoscopic extraction to avoid a potentially morbid open procedure. The HM3 and LithoTron have comparable efficacy and safety. This modality is particularly effective for a stone aggregate of less than 20 mm., while a larger stone burden of greater than 20 mm. in aggregate and multiple stones are clear risk factors for treatment failure.

EXTRACORPOREAL SHOCK WAVE LITHOTRIPSY OF PANCREATIC DUCT STONES USING THE HEALTHTRONICS LITHOTRON LITHOTRIPTOR AND THE DORNIER HM3 LITHOTRIPSY MACHINE

Pancreatic duct stones, which are most often a result of alcohol induced chronic pancreatitis, can lead to chronic abdominal pain, pseudocysts, and exocrine and endocrine failure of the pancreas. Others have reported success using extracorporeal shock wave lithotripsy (ESWL) (Dornier Medical Systems, Inc., Marietta, Georgia) for pancreatic stones. We report our experience with pancreatic ESWL using the LithoTron (Healthtronics, Marietta, Georgia) and HM3 (Dornier) lithotripsy machines. We performed pancreatic ESWL in 23 patients in 4 years, including in 12 with the LithoTron and in 11 with the HM3. After ESWL endoscopic retrograde cholangio-pancreatography (ERCP) was performed in all cases. Stone-free status was defined as no stone fragments visualized or the elimination of all post-ESWL stones by ERCP. Stone-free status was documented in 83% and 82% of patients treated with the LithoTron and HM3, respectively, and 2 per group later required open surgical intervention. There were no changes in pancreatic enzymes and no cases of sepsis or fever after ERCP. In association with post-procedure ERCP pancreatic ESWL is an effective and safe procedure that enables patients with obstructing pancreatic duct stones recalcitrant to primary endoscopic extraction to avoid a potentially morbid open procedure. The HM3 and LithoTron have comparable efficacy and safety. This modality is particularly effective for a stone aggregate of less than 20 mm., while a larger stone burden of greater than 20 mm. in aggregate and multiple stones are clear risk factors for treatment failure.

Flank position ureterorenoscopy: new positional approach to aid in retrograde caliceal stone treatment.

Clearance of lower pole stones and complex maneuvers such as basket repositioning remain challenging in ureteroscopic treatment of caliceal stone burdens. We describe the initial use of flank position ureteroscopy (FPU) with modifications to aid in the treatment of complex caliceal urolithiasis. We hypothesized that gravitational force acting on caliceal stones and fragments during holmium laser treatment would result in fragments being repositioned into the dependent renal pelvis, allowing enhanced treatment. Eleven patients with complex upper tract stone disease (aggregate stone burden 1.5-5 cm) were treated using FPU. Patients were positioned with the stone-containing side superior. Flexible cystoscopy followed by flexible ureterorenoscopy and intracorporeal lithotripsy were performed. We utilized several modifications of the technique, including a radiolucent table and rotational C-arm fluoroscopy unit. Once all stones and particles fell into the dependent renal pelvis, additional laser fragmentation was simple. We observed the expected advantage of gravitational drainage of particles and stone into the renal pelvis during procedures. In many cases, fragments passed partially down the ureter during treatment. Basket repositioning of stones was not necessary. One complication, collecting system perforation during access, was treated with stent placement and successful delayed FPU. Seven patients were stone free at follow-up. Four patients with stone burdens >3 cm had approximately 80% stone burden reduction, but residual asymptomatic lower-pole particles (2-6 mm) remained, with several clearing with a secondary procedure. The use of FPU for the performance of complex renal stone treatment is a useful aid. Further refinement and comparison with standard technique is ongoing.

Wavelet-Based Three-Dimensional Descriptors of Aggregate Particles

Morphological characteristics of stone aggregates, including particle shape, angularity, and surface texture, have a significant impact on the performance of hot-mix asphalt materials. To accurately identify and quantify these critical aggregate characteristics, well-defined particle descriptors are essential. Moreover, because a large number of irregular particles must be assessed to adequately characterize an aggregate material, descriptors that can be quantified with automated machines are preferred. In processing true three-dimensional (3-D) data from a laser scanner, wavelet-based 3-D particle descriptors are proposed as a way to characterize individual stone particles. Aided by the multiresolution analysis feature of the wavelet transform, these descriptors provide a generalized, comprehensive, and objective way of describing aggregates. This approach was implemented in conjunction with an automated laser-profiling device built for rapidly characterizing the size and shape properties of aggregate samples. Tests with this equipment have produced data that show strong correlations between the wavelet-based particle descriptors and visual perceptions of the aggregate morphological properties. These results demonstrate that the wavelet-based approach is a promising method for quantifying these important aggregate properties.

Mix design for oil palm shell concrete

The mix design of lightweight concrete using oil palm shell (OPS) as aggregate differs widely from the procedure of mix proportioning for conventional concrete with crushed stone aggregate. The mix design depends on the properties of aggregates. The 28-day compressive strengths of OPS concrete designed according to the ACI method for conventional concrete and methods mentioned in references [A. Short, W. Kinniburgh, Lightweight Concrete, third ed., Applied Science Publishers, London, 1978; M.S. Shetty, Concrete Technology, S. Chand, India, 1993] for lightweight aggregate concrete have been found to be very much less than the targeted design strength of OPS concrete. It is confirmed that the mix design method of ACI and methods mentioned in the above references fail for the design of mix for OPS aggregates. A trial mix design for concrete with OPS as coarse aggregate has resulted in acceptable strength of 24 N/mm 2 for 28-day. Fly ash as mineral admixture and calcium chloride as an accelerator have also been used to study the improvement in strength.

Mechanical properties of steel fibre reinforced lightweight concrete with pumice stone or expanded clay aggregates

This paper presents basic information on the mechanical properties of steel fibre-reinforced light-weight concrete, manufactured using pumice stone or expanded clay aggregates. Results are presented for standard compressive tests and indirect tensile tests (splitting tests on cylinder specimens and flexure tests on prismatic beams using a three-point loading arrangement) under monotonically increasing or cyclically varying loads. The influence of steel fibres and aggregate types on modulus of elasticity, compressive and tensile strength and post-peak behaviour is evaluated. Test results show that compressive strength does not change for pumice stone aggregates, while an increase is observed for expanded clay; tensile strength and fracture toughness are significantly improved for both pumice stone and expanded clay. The results also show that with both expanded clay and pumice stone lightweight aggregates a suitable content of fibres allows one to obtain performances comparable with those expected from normal weight concrete, the important advantage of lower structural weight being maintained.

In Situ Measurement and Empirical Modeling of Base Infiltration in Highway Pavement Systems

Free-drainage lysimeters, commonly used in agriculture to monitor evapotranspiration and solute transport, were installed at three highway test sites in Tennessee. The lysimeters were installed below flexible pavement systems just beneath the coarse-graded asphalt stabilized base. The lysimeters collect water infiltrating the unbound aggregate (stone base) and monitor the quantity of infiltration by diverting the flow into tipping bucket rain gauges. One test site indicated infiltration beneath the longitudinal joint in the first several months of monitoring. A second test site, where the dense surface layer was not in place, indicated infiltration correlating with rainfall. Data from this site were used to develop a model to predict the measured infiltration based on the recorded rainfall. The monitoring method and modeling approach may be applicable in the investigation of pavement permeability, drainage system efficiency, and the role of infiltration in the seasonal variation of water content of unbound pavement layers.

The densification of granular soils using vibro methods

The method of densifying in-situ sandy soils using deep vibration (vibro) was first developed in Germany over 60 years ago. Since then the technique has been extended to improve a wide range of soil types for structures of up to 30 storeys in height. A major development in the vibro market worldwide over the last 25 years has been the treatment of soils to resist the effects of liquefaction during seismic events. It is well known that the presence of silt and clay fines inhibits the physical in-situ densification of sandy soils. Experience has shown that a maximum fines content of about 15% would normally permit the performance of vibro compaction methods without the addition of stone aggregate. However, the development of new vibrators and modified construction techniques has enabled sands with significantly higher fines content to be treated. The paper describes how densification of granular soils has progressed with the development of new equipment, the greater appreciation in the manner in which soils respond to both vibration and displacement, and the importance of workmanship during treatment. A number of case histories including in-situ test results, long-term monitoring of ageing effects and references to treated sites already subjected to earthquakes are presented.