© Copyright IPJ 2003 Volume # Number # May 2003 Page 1 STIFFNESS MODULUS AND PHASE ANGLE PREDICTION MODELS FOR HIGH M ODULUS ASPHALT CONCRETE Luís Picado -Santos * Assistant Professor, Department of Civil Engineering, FCT, University of Coimbra, Portugal * DEC-FCT, Pólo II, Universidade de Coimbra, 3000 Coimbra, Portugal [email protected] Silvino D. Capitão Assistant Professor, Department of Civil Engineering of the Polytechnic of Coimbra, Coimbra, Portugal Jorge C. Pais Assistant Professor, Department of Civil Engineering of the University of Minho, Guimarães, Portugal ABSTRACT: To improve the service life of pavements, innovative materials have to be used to produce asphalt concrete layers that can better withstand distress phenomena. The rehabilitation of a structural layer on the EN14 (Portuguese national highway 14) using high modulus asphalt concrete (HMAC) has been studied. The project workplan involved the laboratory design of the mixture by undertaking performance tests and constructing trial sections to observe the effectiveness of the mixture. Prismatic specimens were extracted from these trial sections and similar specimens have been produced in the laboratory. Fundamental tests, namely, repetitive four-point bending, were performed on both specimens for several temperatures and loading conditions. This made it pos- sible to determine their mechanical properties, stiffness modulus and phase angle. The values for these parame- ters enable prediction models to be developed for those characteristics, and these can be used to help design HMAC. KEY WORDS: Asphalt concrete, high modulus, performance tests, stiffness, phase angle, prediction. 1. INTRODUCTION Following the development of hard grade paving asphalts (i.e. having penetration of less than 25/10 mm at 25 o C), High Modulus Asphalt Concrete (HMAC) began to be used in France in the 1980s [1]. These materials had a better mechanical behavior than traditional asphalt concretes relative to the distress mechanisms often consid- ered in pavement design (cracking and permanent deformation). HMAC was first used to reinforce old pave- ments. It was subsequently used in the base layers of new pavements to obtain economic benefits by reducing thickness, especially where local aggregates had a low crushing index, or when traffic was intense, slow or channeled. HMAC were introduced into Portugal in early 1990s by the road administration who laid the mixture at a very busy access to a major bridge in Lisbon. It was the first attempt to use a stronger asphalt concrete to solve sup- port capacity problems. The technique was repeated in 1996 and 1997 with similar objectives, namely, to gain experience in HMAC production, paving operations and service behavior. The 16 km length of the EN14 (Portu- guese national highway 14) being rehabilitated near Porto has supported the research described in this paper. According to the standardization process being developed in Europe, HMAC is asphalt concrete that incorpo- rates continuously graded aggregates, typically having 32 to 35 % of material less than 2 mm and 7 to 8 % less than 0.075 mm. The maximum aggregate size is 10, 14 or 20 mm, respectively for layers whose thickness varies from 6 to 10 cm, 7 to 12 cm and 10 to 15 cm. French standard NF P 98-140 [2] distinguishes two classes of pe r- formance for HMAC: type 1 HMAC and type 2 HMAC (more often used). Asphalt content is about 5% or less in the first case, and usually varies between 5.5 and 6 % in the second case. This paper focuses on the evaluation of the mechanical characteristics of HMAC ( the stiffness modulus and phase angle) established [3] to build a structural layer. The material was first characterized by submitting pris- matic specimens (50x8x8 cm 3 ) extracted from trial sections to fundamental tests (strain controlled four-point
STIFFNESS MODULUS AND PHASE ANGLE PREDICTION MODELS FOR HIGH MODULUS ASPHALT CONCRETE
Jun 24, 2023
Welcome message from author
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Related Documents
