STUDENT SPOTLIGHT: Each month, or every other month, a student will provide a 1-page illustrated abstract of the research they are currently conducting. This is a wonderful opportunity for the student, for our International Society for Concrete Pavements (ISCP) Members, and for the transferring and sharing technology/research through our concrete paving industry.
The ISCP “STUDENT RESEARCH SPOTLIGHT” for November 2024 is Salman Amin, a MSE student in Civil and Environmental Engineering at Youngstown State University (Youngstown, USA).
BIO:
Salman Amin is a 2nd year MSE student in Civil / Environmental Engineering at Youngstown State University. His primary area of research is within transportation with a thesis focusing on quantifying the properties of recycled concrete for use as base/sub-base pavement material. This work is being overseen by his thesis advisor and ISCP board member, Dr. John W. DeSantis. Salman is a professional architect specializing in building services and project management. He has worked for Cushman and Wakefield, and the Indiana Department of Transportation (INDOT) apart from having extensive teaching and research experience of about 8 years at Jamia Millia Islamia, New Delhi which is a top ranking central government university in India, where he is from. His research interests include climate change, energy efficiency and conservation, and sustainable design approaches among others.
TITLE:
Exploring the Utility of Recycled Concrete as a Substitute for Crushed Stone Aggregate in Pavement Design
Granular materials such as crushed stone and aggregate are used as the primary material for base and sub-base layers in pavement design. The design parameter used to relate the stiffness of these layers is the Resilient modulus (MR). Granular material exhibits a stress hardening behaviour, which means that as the material experiences an increase in load, the MR also increases. In contrast to this, fine materials such as cohesive soils exhibit stress softening. Figure 1(a) and (b) demonstrate the behaviour of the two material types, illustrating bulk stress vs MR.
This study examines the effect of different parameters (e.g., nature of material, deviator and confining stress, and moisture content) on the MR. Deviator stresses are those that the pavement experiences due to traffic loading. It is a top-down stress, and in the concerned layer, it would be stress (σ1), as shown in Figure 2(a). Confining stresses are the stresses (σ3) experienced due to the surrounding material. To measure MR in the lab, Repeated Load Triaxial (RLT) testing is carried out on a cylindrical sample. The dimensions of the cylinder for granular material – the type selected for the study – and the change in the stresses acting due to the cylindrical form are shown in Figure 2(b). The bulk stress, Ɵ (shown in Figure 1) considers the effect of both the deviator and confinement stress and is given by: Bulk Stress, Ɵ (psi) = σ1 + 3*(σ3)
In this study, a sample of crushed stone aggregate and recycled concrete were subjected to MR testing. The procedure is important and follows AASHTO T307. The salient steps are described hereinafter. The sample is prepared in five equal layers with 1-minute vibratory compaction after each of the first four layers and 4-minute vibratory compaction after the 5th layer. After the cylinder has been prepared it is tested in the RLT machine. One test consists of 16 sequences. An initial conditioning sequence is conducted and has 1,000 cycles. One cycle consists of 0.1 second of loading and 0.9 second of rest, totalling a 1 second cycle, and therefore the total duration of the conditioning sequence is 1,000 seconds. After the conditioning sequence, there are 15 sequences of 100 cycles each with varying amounts of stresses. The different stresses and sequences are detailed out sequence-wise in Table 1. For MR calculation, the measurements of the last 5 cycles of each sequence except the conditioning sequence are averaged together, respectively.
Both the crushed stone aggregate sample and the recycled concrete sample were tested multiple times at different moisture contents – 0%, 3% and 5%. The MR results of the 0% moisture content is included below in Figure 3. Additionally, the samples were compared for the following parameters: MR at different stresses, % compaction of samples, and gradations of the samples before and after testing.
The test results indicate that with every passing test, the stress hardening property of recycled concrete reduces towards the higher stress values, and the standard deviation increases. This can be due to the disintegration of the material over time, supported by the before and after testing gradations of the recycled concrete. Conversely, in the lower stress range, recycled concrete exhibits higher MR values consistently over each incremental test.
ISCP would like to feature a “STUDENT RESEARCH SPOTLIGHT” each month, or every other month. If you would like to nominate a student, or if you are a student and would like to nominate yourself or a colleague, please send ISCP an email to: newsletter@concretepavements.org
ALL SPOTLIGHTS:
DECEMBER 2021—Inaugural: Katelyn Kosar, PhD Student-Department of Civil and Environmental Engineering, University of Pittsburgh (Pitt): www.concretepavements.org/2021/12/14/new-at-iscp-student-research-spotlight/
JANUARY 2022: Aniruddha Baral, Ph.D. Candidate-Department of Civil and Environmental Engineering, University of Illinois-Urbana-Champaign: www.concretepavements.org/2022/01/15/student-research-spotlight-jan-2022/
FEBRUARY 2022: Jordan Ouellet, Tech, BEng, MASc, PhD Candidate, Teaching and Research Assistant, University of Illinois at Urbana-Champaign: www.concretepavements.org/2022/02/26/student-research-spotlight-february-2022/
MARCH 2022: Sampath Kumar Pasupunuri, Ph.D. candidate, Pavement Engineering-School of Civil Engineering, University of Nottingham, UK: https://www.concretepavements.org/2022/03/31/student-research-spotlight-march-2022/
APRIL 2022: Anupam B R, Pursuing his doctorate-Indian Institute of Technology Bhubaneswar, India: https://www.concretepavements.org/2022/04/15/student-research-spotlight-april-2022
MAY 2022: Andréia Posser Cargnin, Ph.D. Candidate, Polytechnic School, University of São Paulo (São Paulo, Brazil): https://www.concretepavements.org/2022/05/09/student-research-spotlight-may-2022/
JUNE 2022: Charles Donnelly, Ph.D. Candidate, Department of Civil and Environmental Engineering, University of Pittsburgh (Pittsburgh, USA): https://www.concretepavements.org/2022/06/24/student-research-spotlight-june-2022/
JULY 2022: Amir Malakooti, Ph.D. Candidate, Department of Civil and Environmental Engineering, Iowa State University (Ames, Iowa, USA): https://www.concretepavements.org/2022/07/30/student-research-spotlight-july-2022/
AUGUST 2022: Haoran Li, Ph.D. Candidate, Department of Civil and Environmental Engineering, University of Pittsburgh (Pittsburgh, USA): https://www.concretepavements.org/2022/08/24/student-research-spotlight-august-2022/
SEPTEMBER 2022: Sumit Nandi, Ph.D. Candidate, Department of Civil Engineering, Indian Institute of Technology Roorkee (Roorkee, India): https://www.concretepavements.org/2022/09/18/student-research-spotlight-september-2022/
OCTOBER 2022: Eric Ribeiro da Silva, Ph.D. Candidate, Department of Civil Engineering, Polytechnic School of the University of São Paulo (São Paulo, Brazil): https://www.concretepavements.org/2022/10/20/student-research-spotlight-october-2022/
NOVEMBER 2022: Zachary Brody, Ph.D. Candidate, Department of Civil and Environmental Engineering, University of Pittsburgh (Pittsburgh, USA): https://www.concretepavements.org/2022/11/18/student-research-spotlight-november-2022/
DECEMBER 2022: Jesús Castro Pérez, Ph.D. Candidate, Department of Civil and Environmental Engineering, University of Illinois at Urbana-Champaign (Urbana, USA): https://www.concretepavements.org/2022/12/17/student-research-spotlight-december-2022/
JANUARY 2023: Dan King, Ph.D. Candidate, Department of Civil and Environmental Engineering, Iowa State University (Ames, USA): https://www.concretepavements.org/2023/01/26/student-research-spotlight-january-2023/
FEBRUARY 2023: Kathryn Kennebeck, Ph.D. Candidate, Department of Civil and Environmental Engineering, University of Pittsburgh (Pittsburgh, USA): https://www.concretepavements.org/2023/02/28/student-research-spotlight-february-2023/
MARCH 2023: Sinan Kefeli, Ph.D. Candidate, Department of Civil and Environmental Engineering, Iowa State University (Ames, USA): https://www.concretepavements.org/2023/03/13/student-research-spotlight-march-2023/
APRIL 2023: Niwesh Koirala, Ph.D. Candidate, Department of Civil and Environmental Engineering, Texas Tech University (Lubbock, USA): https://www.concretepavements.org/2023/04/07/student-research-spotlight-april-2023/
MAY 2023: Christian A. Sabillon, Ph.D. Candidate, The University of Texas at Austin (Austin, Texas, USA): https://www.concretepavements.org/2023/05/05/student-research-spotlight-may-2023/
JUNE 2023: Saima Yaqoob, Ph.D. Candidate, KTH (the Royal Institutes of Technology) (Stockholm, Sweden): https://www.concretepavements.org/2023/06/15/student-research-spotlight-june-2023/
JULY 2023: Ricardo Hungria, Ph.D. Candidate, Louisiana State University (Baton Rouge, USA): https://www.concretepavements.org/2023/07/11/student-research-spotlight-july-2023/
AUGUST 2023: Megan Darnell, Ph.D. Candidate, University of Pittsburgh (Pittsburgh, USA): https://www.concretepavements.org/2023/08/07/student-research-spotlight-august-2023/
SEPTEMBER 2023: Jitendra Patel, Ph.D. Candidate, Alma Mater Studiorum – Università di Bologna (Italy): https://www.concretepavements.org/2023/09/05/student-research-spotlight-september-2023/
OCTOBER 2023: Omar K. Omar, Ph.D. Candidate, Louisiana State University (Baton Rouge, USA): https://www.concretepavements.org/2023/10/05/student-research-spotlight-october-2023/
NOVEMBER 2023: Mason Smetana, Ph.D. Candidate, University of Pittsburgh (Pittsburgh, USA): https://www.concretepavements.org/2023/11/07/student-research-spotlight-november-2023/
DECEMBER 2023: Avinash Jha, M.Tech Student, Indian Institute of Technology Gandhinagar (India): https://www.concretepavements.org/2023/12/10/student-research-spotlight-december-2023/
JANUARY 2024: Matthew Sheffield, Ph.D candidate, University of North Carolina at Charlotte (Charlotte, USA): https://www.concretepavements.org/2024/01/13/student-research-spotlight-january-2024/
FEBRUARY 2024: Chintada Chandrasekhar, Ph.D candidate, Indian Institute of Technology Roorkee (Roorkee, India): https://www.concretepavements.org/2024/02/08/student-research-spotlight-february-2024/
MARCH 2024: Subham Jain, Ph.D candidate, Indian Institute of Technology Kanpur (Kanpur, India): https://www.concretepavements.org/2024/03/08/student-research-spotlight-march-2024/
APRIL 2024: Etienne Beya Nkongolo, Ph.D candidate, University of Missouri Kansas-City (Kansas City, USA): https://www.concretepavements.org/2024/04/11/student-research-spotlight-april-2024/
MAY 2024: Shivani Sharma, Ph.D candidate, Indian Institute of Technology Gandhinagar (Gandhinagar, India): https://www.concretepavements.org/2024/05/14/student-research-spotlight-may-2024/
JUNE 2024: Isaac Oyawoye, Ph.D candidate, University of North Carolina at Charlotte (Charlotte, USA): https://www.concretepavements.org/2024/06/16/student-research-spotlight-june-2024/
JULY 2024: Tianzhen Li, Ph.D candidate, Xi’an Jiaotong-Liverpool University and the University of Liverpool (Suzhou, China): https://www.concretepavements.org/2024/07/04/student-research-spotlight-july-2024/
AUGUST 2024: Andrés Gabriel César Torres, Ph.D candidate, Polytechnic School of the University of São Paulo (São Paulo, Brazil): https://www.concretepavements.org/2024/08/06/student-research-spotlight-august-2024/
SEPTEMBER 2024: Bhabya Thakur, Masters student, Indian Institute of Technology Gandhinagar (Gandhinagar, India): https://www.concretepavements.org/2024/09/21/student-research-spotlight-september-2024/
OCTOBER 2024: Alberto Castillo, PhD student, Purdue University (West Lafayette, USA): https://www.concretepavements.org/2024/10/22/student-research-spotlight-october-2024/