Low-quality Aggregate Research Articles

A Study on Measurement and Calculation Method for Coefficient of Linear Thermal Expansion of Low-Quality Aggregate

A Study on Measurement and Calculation Method for Coefficient of Linear Thermal Expansion of Low-Quality Aggregate

Using Cement as Filler to Enhance Asphalt Mixes Performance in Hot Climate Regions

This paper investigates the addition of different percentages of ordinary Portland cement as a filler in conventional asphalt concrete for a range of heavy traffic. Road pavement agencies in hot areas face the daunting challenge of preserving their pavements in a fair to good condition to increase their lifespan. This challenge is due to the high occurrence of permanent pavement deformation via rutting, which is one of the major distress factors influencing pavements. This is a particularly serious issue in hot and arid countries which are closely associated with various aggravating factors. These aggravating factors include the choice of bitumen binder viscosity, the type of bitumen, the available low-quality materials, and the high environmental temperatures. Ultimately, poor performance will show within the first few years of service as permanent deformations such as rutting, shoving, and depressions. The examined properties include the resilient modulus and the resistance to rutting. Findings indicate that the resistance to rutting and the rigidity of the asphalt concrete are both substantially increased as the cement content is increased. Moreover, to meet the heavy traffic spectrum requirements, increasing the embedded cement content in the asphalt concrete improves pavement structural capacity. Finally, based on the rigidity expected for different cement levels, design curves are provided for pavement design in hot climates using low quality aggregate materials.

Effect of Mineral Admixtures on the Performance of Low-Quality Recycled Aggregate Concrete

To improve the application of low-quality aggregates in structural concrete, this study investigated the effect of multi-purpose mineral admixtures, such as fly ash and ground granulated blast-furnace slag, on the performance of concrete. Accordingly, the primary performance of low-quality recycled aggregate concrete could be improved by varying the replacement ratio of the recycled aggregate and using appropriate mineral admixtures such as fly ash and ground granulated blast-furnace slag. The results show the potential for the use of low-quality aggregate in structural concrete.

Predicting Aggregate Degradation in Forest Roads in Northwest Oregon

In the Pacific Northwest, forest roads have the potential to cause significant environmental degradation, especially to water resources due to increased sediment production. The goal of this research is to improve the understanding of road degradation during hauling by improving our understanding of the aggregate degradation process. We correlate the wear rates to standard material property tests that may allow for improved prediction of the impacts from forest roads based on the selection of aggregate surfacing. Finally, we determine the changes in stress distribution between the subgrade and aggregate interface. High-, medium-, and low-quality aggregates were used from three quarries in western Oregon for this project. These aggregates are indicative of the range of materials used on forest roads in the region. Two material property tests, namely the Los Angeles (LA) abrasion and micro-Deval tests, were used to determine their ability to predict aggregate performance during hauling by relating values for aggregate wear to these aggregate properties. Eighteen nonwoven geotextile bags were created, measuring 60 cm (two-feet long) and 20 cm (eight inches) in diameter, with a pore size equivalent to a 0.149 mm (# 100) sieve. They were filled with a known quantity and particle size distribution of aggregate and embedded into a newly constructed forest road. Stress gages were installed in the road surface between the aggregate and subgrade levels to record the changes in stress at the subgrade level. Samples were subjected to three levels of traffic (500, 950, and 1500 passes) using a loaded dump-truck that had a steering axle and one tandem drive axle, weighing 25,038 kg or 55,200 lb. The results showed that less breakage occurred with the medium- and high-quality aggregates than the low-quality aggregate. There was a correlation between the material property test (either the micro-Deval or the LA abrasion test) and the fine index, indicating the predictability of these tests in terms of aggregate performance. Finally, the higher quality aggregate was able to better distribute the stresses from the wheel better than the lower quality aggregate and was able to reduce the stress reaching the subgrade. Although the results are limited to the three types of rock used in this study, they indicate the ability of the high-quality aggregate to lessen the environmental impacts from forest roads.

Polishing resistance of polymer concrete pavement using limestone aggregate

ABSTRACTThe purpose of this research was to investigate the polishing resistance of uncoated and resin-coated specimens under polishing and chemical attack. Low-quality aggregate, limestone and orthophthalic unsaturated polyester resin were the main materials. From the analysis, the macrotexture was reduced from the coarser aggregate to finer aggregate mix proportion. Resin-coated specimen was more polishing resistant than the uncoated specimen. Thickness reduction for resin-coated specimen was 1.8% after 9 h polishing, while the thickness reduction for uncoated specimen was 1.9% after 6 h polishing. In comparison with the uncoated specimen, the British pendulum number (BPN) of resin-coated specimen under dry and wet conditions was 8% higher and 16% lower, respectively. For the chemical resistant investigation, the immerging mediums used were water, sulphuric acid, sodium chloride, sodium hydroxide and used engine oil. The uncoated and resin-coated specimens were immersed into the solutions under direct immersion as well as wetting and drying for 24 weeks. Sulphuric acid and sodium hydroxide affected the BPN on both uncoated and resin-coated specimens but not for water and used engine oil, while sodium chloride only affected the BPN of the uncoated specimen.

Life cycle assessment to evaluate the environmental performance of new construction material from stainless steel slag

Many new opportunities are explored to lower the CO2 emissions of the cement industry. Academic and industrial researches are currently focused on the possibility of recycling steel production residues in the cement industry, in order to produce new “low-carbon” binders for construction materials. The purpose of this paper is to assess the environmental benefits and costs of steel residue valorisation processes to produce a new binder for construction materials. Among other stainless steel slags (SSS), argon oxygen decarburisation (AOD)-slag has the potential to be recovered as a binder during the production of new construction materials. Alkali activation and carbonation processes can, in fact, activate the binding properties of the AOD-slag. However, AOD-slag is today only recycled as low-quality aggregate. For the present study, three different types of construction blocks (called SSS-blocks) were developed starting from the AOD-slag (one block through alkali activation and two blocks through carbonation). The data from the production of the three construction blocks have been collected and used to perform a life cycle assessment (LCA) study, comparing SSS-block production with the production of traditional paver ordinary Portland cement (OPC) concrete. The analysis showed that SSS-block production through alkali activation and carbonation has the potential of lowering some of the environmental impacts of OPC-concrete. The LCA results also show that the main bottleneck in the alkali activation process is the production of the alkali activators required in the process, while the use of electricity and of pure CO2 streams in carbonation lowers the environmental performances of the entire process. The valorisation of AOD-slag to produce new construction materials is a promising route to lower the environmental impacts of cement and concrete industries. This product-level analysis stresses the need of updating the LCI datasets for alkali activators and boric oxide and of widening the scope of the environmental analysis up to system level, including potential economic interactions and market exchanges between steel and construction sectors.

성능개선형 폴리카르본산계 혼화제를 사용한 콘크리트의 성능평가에 관한 실험적 연구

최근 국내에서 천연골재의 고갈, 수급 불균형 등의 이유로 부순모래를 100% 사용하거나, 내륙 지역의 경우 개답사, 마사토 등과 같은 저품질의 골재를 사용하는 경우가 증가하고 있으며, 높은 흡수율과 점성의 증가로 인하여 작업성 확보를 위해 배합수 량이 증가되는 실정이다. 배합수의 증가로 강도 저하, 건조수축 증가, 블리딩 증가 등에 인한 다양한 품질하자를 유발하게 된다. 특히 지하주차장 무근콘크리트의 경우 표면부와 저면의 수축차의 증가로 인한 컬링이 발생하게 되고, 컬링이 발생한 후에 차량이 통과하게 되면 무근 콘크리트에 균열이 발생하게 된다. 지하 최하층의 경우 배수판 사이를 흐르는 지하수의 유입으로 누수현상도 발생하게 되며, 차량 통행에 따른 소음도 발생할 수 있다. 또한 블리딩 증가로 인한 표면 강도 저하로 박리, 박락 등의 하자가 다발적으로 발생하여 매년 민원과 소송이 증가하고 있다. 따라서 본 연구에서는 이러한 문제를 해결하기 위해서 저품질의 골재가 사용되었을 경우 지하주차장 무근콘크리트의 품질하자를 최소화시키기 위한 성능개선형 PC 혼화제를 개발하였으며, 슬럼프 경시변화, 압축강도, 블리딩, 건조수축 길이변화 시험을 실시하여 일반 준PC 혼화제를 사용한 콘크리트와 비교하였다. 그 결과 경시에 의한 슬럼프의 저하를 최소화시킬 수 있음을 확인할 수 있었으며, 추가적인 가수가 필요 없거나 최소화시킬 수 있으므로 일반 준PC 혼화제를 사용한 콘크리트보다 고품질을 확보할 수 있을 것으로 기대된다. 특히 건조수축량이 20% 정도 감소하여 건조수축균열 및 컬링 제어에 효과적일 것으로 판단된다. Because of the supply-demand problem of aggregate, recently, the construction sites using 100% crushed sand are increasing and the use of low quality aggregate such as farmland sand is increasing too. When the low quality aggregate is used, the various quality defect of concrete such as the strength reduction, the increase of shrinkage and bleeding can be occurred. Therefore, in this study, the performance improvement PC admixture was developed to minimize the quality defect of plain concrete of basement parking area, when the low quality aggregate was used at the plain concrete of basement parking area. The slump loss to elapsed time test, the compressive strength test, the bleeding test and the drying shrinkage test were carried out.

COMPLETELY RECYCLABLE CONCRETE OF AGGREGATE-RECOVERY TYPE BY A NEW TECHNIQUE USING AGGREGATE COATING

To build up a recyclable society, the environmental issue of concrete is approached comprehensively with a new technique using aggregate coating. The increase of concrete strength is achieved by 1.2 times using improved coating agent mixed properly with silica-fume and by-product powder. A similar effect is also affirmed even if applied to low-quality aggregate. A recycling performance shows that over 90% of aggregate can be recycled. In conclusion, the technique developed by this study is effective for the use of low-quality aggregate and the recycle of coarse aggregate as well as the solution of the environmental problem of concrete.

Manufacture of High Softening Waxy Asphalt for Use in Road Paving

This research aims to manufacture a special type of high softening waxy asphalt of penetration grade 60/70 to be used as a suitable binder in production of a hot mix asphalt (HMA) consisting of low quality aggregate (high absorptive type). This type of aggregate is found in Egypt on a large scale, especially in Sharkia governate. To achieve this aim, crude microcrystalline wax, which is characterized by its high congealing point, kinematic viscosity, and its low penetration, was mixed with the normal penetration grade asphalt 60/70 in percentage ranging from 2 to 6% by weight. The resultant asphalt samples were found to have high softening point ranging from 58°C to 75°C and penetration values within the current specifications. The produced waxy asphalt samples were used in preparing the HMA using the high absorptive aggregate. The mixes were evaluated using the Marshall method and tested for rutting resistance. The laboratory results show that the prepared mixes are suitable for use as a wearing or base course for the medium and low traffic roads.

Statistical Modeling of Accelerated Pavement Failure Using Response Surface Methodology

Rutting is one of the major load-related distresses in airport flexible pavements. Rutting in paving materials develop gradually with an increasing number of load applications, usually appearing as longitudinal depressions in the wheel paths and it may be accompanied by small upheavals to the sides. Significant research has been conducted to determine the factors which affect rutting and how they can be controlled. Using the experimental design concepts, a series of tests can be conducted while varying levels of different parameters, which could be the cause for rutting in airport flexible pavements. If proper experimental design is done, the results obtained from these tests can give a better insight into the causes of rutting and the presence of interactions and synergisms among the system variables which have influence on rutting. Although traditionally, laboratory experiments are conducted in a controlled fashion to understand the statistical interaction of variables in such situations, this study is an attempt to identify the critical system variables influencing airport flexible pavement rut depth from a statistical DoE perspective using real field data from a full-scale test facility. The test results do strongly indicate that the response (rut depth) has too much noise in it and it would not allow determination of a good model. From a statistical DoE perspective, two major changes proposed for this experiment are: (1) actual replication of the tests is definitely required, (2) nuisance variables need to be identified and blocked properly. Further investigation is necessary to determine possible sources of noise in the experiment. Keywords—Airport Pavement, Design of Experiments, Rutting, NAPTF. the relative strength of the pavement layers, a significant portion of the total rutting can occur in the pavement foundation due to weak subgrade or the use of a low quality aggregate base (4). Significant rutting can lead to major structural failure of the pavement. Rutting in paving materials develop gradually with an increasing number of load applications, usually appearing as longitudinal depressions in the wheel paths accompanied by small upheavals to the sides (5). To limit pavement surface rutting to acceptable levels, the various paving layers and the subgrade must be given careful attention during the design process. Rutting makes it difficult to steer the wheels as the wheels would tend to follow the rutted path. This becomes dangerous in case of airport runways if the runway has even slight amount of rutting due to the large size and high speeds of the airplanes. A rut depth of 1 inch in airport pavements is considered to indicate functional failure due to the ponding it can cause in the presence of water resulting in hydroplaning of the aircraft wheels. Significant research has been conducted to determine the factors which affect rutting and how they can be controlled. Design of Experiments (DoE) refers to experimental methods used to quantify indeterminate measurements of factors and interactions between factors statistically through observance of forced changes made methodically as directed by mathematically systematic tables. Thus, it is a structured, organized method for determining the relationship between factors (Xs) affecting a process and the output of that process (Y). Using the experimental design concepts, a series of tests can be conducted while varying levels of different parameters, which could be the cause for rutting in airport flexible pavements. If proper experimental design is done, the results obtained from these tests can give a better insight into the causes of rutting and the presence of interactions and synergisms among the system variables which have influence on rutting. This paper reports findings from a preliminary investigatory study conducted to quantify the effect of some of the critical system variables on airport pavement rutting performance using design of experiments.

BASIC STUDY ON ADEQUATE METHODS OF USING LOW QUALITY AGGREGATE

It is very important for the concrete industry to find adequate methods of using low quality aggregate, because the quality of aggregate has become lower and recently it is not easy to obtain proper aggregate for concrete. In this experiment, it is examined whether low quality aggregate can be effectively used by the following two methods. One method is to adjust mix proportion of concrete in order to cover the defect of using low quality aggregate. In another method, good quality aggregate is mixed with low quality aggregate in order to improve the average characteristics of aggregate. Although the problem is not solved completely by these methods, there seems to be the possibility of using the low quality aggregate by properly adapting these methods according to the required properties of concrete.