Performance of Cement Treated Recycled Aggregates Under Wetting-drying Cycles in Pavement Base PDF Download

Author: Saif Bin Salah
Publisher:
ISBN:
Category :
Languages : en
Pages : 116

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Book Description
Resilient Modulus (MR) is one of the most important stiffness parameter to determine the thickness of a pavement layer (AASHTO 2003 pavement design guideline). Recent studies conducted by researchers on the variability of MR with wetting-drying (WD) and freeze-thaw (FT) cycles show that long-term durability is an important criterion to be considered in designing pavement base with recycled materials. At present, the design procedure does not consider the effect of deterioration of pavement layers due to seasonal variations and limited studies have been conducted to evaluate the effect of environmental deterioration on the reclaimed asphalt pavement (RAP) and recycled crushed concrete aggregate (RCCA) mixtures stabilized with cement. The objective of this study is to evaluate the long-term durability of RCCA and RAP mix materials under repeated wetting-drying cycles. Three different combinations of RCCA and RAP materials containing 0%, 30% and 50% RAP content were used in this study. Each of these combinations were then stabilized with 4% and 6% cement content. After curing for 7 days the samples prepared from these material combinations were subjected to 4, 8, 16 and 30 wetting-drying (W-D) cycles. For the purpose of comparison, a different set of samples of the same combinations were prepared, cured for 7 days, and then further cured for 15, 25, 40 and 70 days. Resilient modulus tests were then conducted on all the samples at the end of these specified W-D cycles and curing periods. Environmental tests were also conducted to assess the effect of WD cycles on the washed-out water quality. These tests included total suspended solids (TSS), total dissolved solids (TDS), turbidity, chemical oxygen demand (COD) and pH. MR test results indicated that addition of 50% RAP into the mix reduced the resilient modulus (MR) by about 39%. Increasing the cement content from 4% to 6% increased the MR values by about 20-35% for all material combinations. Higher cement content also resulted in higher durability of the materials containing 30% and 50% of RAP. All the six material combinations used in this study showed adequate strength after 7-days of curing. But the mix containing 30% RAP + 70% RCCA 4% cement (30R_4C) and 50% RAP + 50% RCCA 4% cement (50R_4C) failed to meet the minimum layer coefficient value of 0.13 (AASHTO 2003) for pavement base layer after 8-16 wetting-drying cycles. Results obtained from the environmental tests after 30 WD cycles were found to be within the permissible values provided by EPA guidelines.

Author: Louay Mohammad
Publisher: Springer
ISBN: 331961908X
Category : Science
Languages : en
Pages : 335

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Book Description
This volume on “Advancement in the Design and Performance of Sustainable Asphalt Pavements” includes a collection of research and practical papers from an international research and technology activities on Mixture Design Innovation, Structural Pavement Design, Advancement in Production and Construction, Climate Changes and Effects on Infrastructure, Green Energy, Technology and Integration. The volume constitutes an important contribution in view of the urgent need to develop materials, designs, and practices to ensure the sustainability of transportation infrastructure. This volume is part of the proceedings of the 1st GeoMEast International Congress and Exhibition on Sustainable Civil Infrastructures, Egypt 2017.

Author: W. Spencer Guthrie
Publisher:
ISBN:
Category : Aggregates (Building materials)
Languages : en
Pages : 4

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Book Description

Author: Gregory E. Halsted
Publisher:
ISBN: 9780893122539
Category : Pavements
Languages : en
Pages : 20

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Book Description
Cement-treated base (CTB) is a general term that applies to an mixture of native soils and/or manufactured aggregates with measured amounts of portland cement and water that is compacted and cured to form a strong, durable, frost resistant paving material. Other descriptions such as soil-cement base, cement-treated aggregate base, cement-stabilized base are sometimes used. This document provides a basic guide on the use of cement-treated base (CTB) for pavement applications. This document provides on overview on the design and construction of CTB for both mixed-in-place and central plant mixed operations. A suggested construction specification is also included.

Author: Mohammad Faysal
Publisher:
ISBN:
Category : Concrete
Languages : en
Pages : 233

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Book Description
Aggregates, which are derived from natural resources, are the most important raw materials used in pavement construction; however, depletion of the natural resources, increasing labor costs, and environmental concerns have led us to look for alternatives. Recycled materials, such as recycled crushed concrete aggregate (RCCA) and reclaimed asphalt pavement (RAP), can be used as an alternative to natural aggregates and can be obtained from construction of newer structures and demolition of existing structures, such as buildings, bridges, pavement, etc. Recycled materials can reduce the cost, depletion of natural resources, and construction debris. The properties of recycled materials are source-dependent, which limit their utility to a great extent. Considering these factors, this experimental program was designed to evaluate the strength, stiffness, durability, and environmental impacts of using recycled materials in the pavement base. Different combinations of recycled crushed concrete aggregates (RCCA) and reclaimed asphalt pavement (RAP) aggregates, under cement-treated or untreated conditions, were utilized to evaluate the applicability of these available materials to a flexible pavement base layer. It was found that RAP materials are relatively weaker than the RCCA materials due to the asphalt coating on its surface, but RAP materials can be mixed with RCCA to increase strength. According to this study, RAP can be mixed with RCCA up to a ratio of 50/50, but it must be treated with 4% to 6% cement to fulfill the compressive strength requirement of 300 psi specified in the Texas Department of Transportation's guidelines. The effect of the asphalt content on the strength and stiffness was also determined with the inclusion of additional asphalt to the RAP materials. Durability tests were performed with wetting and drying cycles on the weakest combinations of RCCA and RAP materials. These materials were found to be durable even after 30 wetting and drying cycles. Environmental tests were administered, such as pH, total and volatile dissolved solids, total and volatile suspended solids, turbidity, and chemical oxygen demand (COD). Test results were compared with the requirements of various environmental protection agencies and indicated that the recycled base materials are an environmentally-sound alternative to virgin aggregates and can be used in pavement bases or sub-base layers. The most important stiffness parameter used in pavement design is resilient modulus; however, the resilient modulus test is too complicated and costly to perform on a regular basis. The unconfined compressive strength test is easier to administer. In this study, a multiple linear regression model was developed to determine the resilient modulus value from the parameters obtained from the unconfined compressive strength tests. It is believed that the statistical model can be useful in determining the stiffness parameter of cement-treated base materials.

Author: Susan E. Burns
Publisher:
ISBN:
Category : Aggregates (Building materials)
Languages : en
Pages : 28

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Book Description
Cement-treated aggregate (CTA) is commonly used to provide a stable base for pavements that are placed over weak soil subgrades. Because CTA reduces the thickness of the aggregate required to provide a durable base by approximately one-half, using it as a bearing layer for pavement can limit the quantity of unsuitable soil that must be excavated and removed, and can reduce the erodability of the stabilized soils. However, the field performance of CTA is variable, even when prepared according to set standards. This laboratory-based investigation explored the effects of fines content, cement content, mineralogy, and freeze/thaw cycling on the unconfined compressive strength of cement-treated aggregate. The mineralogy of the base aggregate was found to make a significant difference in the strength of the CTA, with strength increasing in the following order: mica, limestone, and diabase. The granite aggregate yielded variable results, but the strengths were generally on the order of those determined for the diabase aggregate. The pH of the samples also correlated well, with the measured strengths increasing as the pH increased. As was anticipated, increasing the cement content increased the measured unconfined compressive strength of cylinders that were not subjected to freeze/thaw cycling. The same basic trend was observed in cylinders that were subjected to freeze/thaw cycling; however, the increase was less pronounced in the cylinders that were subjected to physical abrasion during thaw cycles. The fines content did not significantly influence the unconfined compressive strength of the cylinders that were not subjected to freeze/thaw cycling; however, the fines content appeared to confer a protective effect to the durability of the cylinders that were subjected to freeze/thaw. For the freeze/thaw test conditions, the unconfined compressive strength increased as the fines content was increased.

Author: Jorge de Brito
Publisher: MDPI
ISBN: 3039211404
Category : Technology & Engineering
Languages : en
Pages : 280

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Book Description
This book is the result of a Special Issue published in Applied Sciences, entitled “New Trends in Recycled Aggregate Concrete". It identifies emerging research areas within the field of recycled aggregate concrete and contributes to the increased use of this eco-efficient material. Its contents are organised in the following sections: Upscaling the use of recycled aggregate concrete in structural design; Large scale applications of recycled aggregate concrete; Long-term behaviour of recycled aggregate concrete; Performance of recycled aggregate concrete in very aggressive environments; Reliability of recycled aggregate concrete structures; Life cycle assessment of recycled aggregate concrete; New applications of recycled aggregate concrete.

Author: Sita Timsina
Publisher:
ISBN:
Category :
Languages : en
Pages : 118

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Book Description
The recycled materials such as, Recycled Crushed Concrete Aggregates (RCCA) and Reclaimed Asphalt Pavement (RAP) treated with cement has been widely used as the alternative granular base in pavement construction in different states in USA due to the depletion of natural resources of virgin aggregates. While a number of factors drive the use of these recycled materials, the two primary factors are economic savings and environmental benefits. In the flexible pavement systems, the base layer contributes to the structural capacity of the pavement systems, so, the quality performance of this layer is essential. However, presence of fine particles in the pavement system promotes the contamination of coarse granular material due to migration of fines from the subgrade which might adversely affect the strength and stiffness of flex-base. As such, the main purpose of this study was to examine the effect of fine contents in granular base materials in terms of strength and stiffness. In this research, a comprehensive experimental program was designed to characterize resilient and compressive behavior of recycled materials in the presence of soil in both natural and stabilized forms. For this study, RAP and RCCA were mixed at different proportions from 0% to 100% with different amount of soil mixture varying between 0% and 24% with cement content ranging from 0% to 6% at 2% interval. Different laboratory tests were conducted to determine the Optimum Moisture Content (OMC), Maximum Dry Density (MDD), Unconfined Compressive Strength (UCS) and Resilient Modulus (MR) of the mixes of RAP, RCCA, soil and Ordinary Portland Cement (Type I/II). Based on the preliminary data, it was found that with the intrusion of fines in cement treated as well as untreated recycled granular bases, both the strength and stiffness decrease as compared with the same specimens without fine particles. With the addition of 12% and 24% of soil in the combination of 30% RAP + 70% RCCA and 50% RAP + 50% RCCA, the value of resilient modulus decreased in the range of 30 -55% in the cement stabilized as well as natural forms. For example,the Mr value of (30/70) RAP/RCCA with 2% cement ranged between 10,000 psi and 45,000 psi, it was reduced to a range of 10,000-30,000 psi with 12% soil intrusion. Similarly, at 6% cement content the Mr value of (30/70) RAP/RCCA the highest value of resilient modulus of 75,000 psi was observed whereas with the 12% soil, the moduli value was reduced to 38,000 psi at the given maximum confining pressure of 20psi.

Author: Inge Hoff
Publisher: CRC Press
ISBN: 1000533336
Category : Technology & Engineering
Languages : en
Pages : 501

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Book Description
Innovations in Road, Railway and Airfield Bearing Capacity – Volume 1 comprises the first part of contributions to the 11th International Conference on Bearing Capacity of Roads, Railways and Airfields (2022). In anticipation of the event, it unveils state-of-the-art information and research on the latest policies, traffic loading measurements, in-situ measurements and condition surveys, functional testing, deflection measurement evaluation, structural performance prediction for pavements and tracks, new construction and rehabilitation design systems, frost affected areas, drainage and environmental effects, reinforcement, traditional and recycled materials, full scale testing and on case histories of road, railways and airfields. This edited work is intended for a global audience of road, railway and airfield engineers, researchers and consultants, as well as building and maintenance companies looking to further upgrade their practices in the field.

Author: Lillian Gonzalez
Publisher:
ISBN:
Category : Aggregates (Building materials)
Languages : en
Pages : 156

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Book Description
Long term durability is a major concern for wide-scale use of recycled aggregate materials in civil engineering construction. The purpose of this study is to provide an insight into the damaging effects of combined wet-dry cycles and repeated mechanical loading in a recycled aggregate concrete (RAC) base course material made from recycled crushed concrete aggregate and cement. A coordinated experimental program followed by a mechanistic pavement modeling and life cycle analysis was conducted as part of this research study. This laboratory investigation was divided into three phases each consisting of both wet-dry exposed specimens (WD), and control or non wet-dry exposed specimens (NWD). Phase I experiments involved monotonic loading tests under compression and flexure to evaluate the strength properties. Phase II involved testing a total of 108 cylindrical specimens in cyclic compressive loading at three different stress ratios. After each regime of cyclic loading, residual compressive strengths were determined. In addition, the load-deformation hysteresis loops and the accumulated plastic deformation were continuously monitored through all loading cycles. Phase III included a flexural fatigue test program on 39 beam specimens, and fracture testing program on 6 notched beam specimens, each one having 19-mm initial notch. Traditional SR-N curves, relating the Stress Ratio (SR) with the number of cycles to failure (N or Nf), were developed. Fatigue crack growth rate and changes in Stress Intensity Factors were obtained to determine Paris Law constants and fracture toughness. A mechanistic analysis of a typical highway pavement incorporating RAC base was performed with KENPAVE program, followed by a Life Cycle Analysis (LCA) using the GaBi software. It was found that the specimens subjected to wet-dry cycles suffered significantly higher damage expressed in terms of accumulated plastic deformation, and loss of residual compressive strength, modulus, fatigue endurance limit, and design life, compared to specimens not exposed to wet-dry cycles. Although such degradation in material properties are important considerations in pavement design, a concurrent Life Cycle Analysis demonstrated that recycled aggregate concrete base course still holds promise as an alternative construction material from environmental stand point.