Civil Engineering Department
College of Engineering \University of Baghdad, held MSc thesis examination titled
Abstract
In recent years, a number of newly constructed asphalt concrete pavements in Iraq and other countries have prematurely failed, having a detrimental effect on both the economy and the safety of the roads. The two most common failure types in recently constructed roads are moisture damage and load-related modes of failure (rutting). One possible action which could be done to enhance the performance of the pavement and ensure that they satisfy the necessary criteria is the use of nanomaterials to modify asphalt concrete for the pavement’s construction.
The aim of this study is to investigate the effect of nanomaterials on the durability of the asphalt concrete mixture thus its resistance to weathering conditions, which are represented by moisture and temperature. So far increasing the operational ability of the road as well as the design life of the pavement throughout the production of more durable mixes is the backbone of this study.
To achieve the objective of this research, a total of 118 asphalt concrete specimens with different geometry and dimension has been prepared and tested following Marshall method to determine the optimum asphalt cement content for the control mixes (with no nanomaterial) as well as to evaluate the effect of nanomaterial on stability, flow and volumetric properties. Also, indirect tensile tests were used to evaluate the moisture susceptibility for the specimens with/without nanometals. Furthermore, repeated load tests were used to assess the resilient modulus as well as permanent deformation properties for the prepared specimen.
In this study, nanomaterials, including nano silica (NS), nano carbonate calcium (NCC), nano clay (NC), nano hydrated lime (HL), and nano platelet hydroxyapatite (NP), were used to examine the prospect of enhancing the durability and resilience of asphalt mixtures. Specifically. The investigated nanomaterial dosages were as follows; NS (1%, 3%, and 5%), NCC (2%, 4%, and 6%), NC (3%, 5%, and 7%), HL wet addition method (0.50%,1%,1.50%), HL dry addition method (1%,2%,3%), and NP (2%, 4%, and 6%), by weight of asphalt cement except those for HL dry was added by weight of aggregate. The results were compared with the control mix (CM), i.e., unmodified mix.
The results revealed that nanomaterials at their optimum content, i.e., 4% NCC, 5% NS, 6% NP, 7% NC, 3% HLdry, and 1.5% HLwet. have the ability to produce mixes with an improved Marshall property, better resistance to permanent deformation and lower moisture damage. The high resilient modulus associated with the use of these nanomaterial produce mixes with higher resilient modulus in comparison with CM, resulted in extending the design life of the pavement structure constructed with the use of asphalt concrete surface course modified with nanomaterials as demonstrated in the results of critical strains, i.e., the tensile strain at the bottom of the asphalt layer and the vertical compressive strain at the top of the subgrade, which is abstracted from the output of KENLAYER software.
In overall, the use of nanomaterials significantly improved the performance of asphalt concrete; also, it provides the possibility of producing more durable mixtures with higher resistance to distress.
