Jean-Francois Masson

Viscosity Determination of Hot-Poured Bituminous Sealants

Hot-poured bituminous sealants are typically selected on the basis of empirical standard tests such as penetration, resilience, flow, and bond to cement concrete briquettes (ASTM D3405). Yet there is no indication of the pertinence of these standard tests to predict field performance. To bridge the gap between sealant fundamental properties and field performance, performance-based guidelines for selection of hot-poured crack sealants are currently being developed. A procedure to measure sealant viscosity is proposed as part of that effort. Using a sealant with an appropriate consistency at the recommended installation temperature would provide a better crack filling and would ensure appropriate bond strength. Therefore, to ensure that sealant-crack wall adhesion is achieved and that the sealant penetrates hot-mix asphalt during installation, a testing procedure for bituminous-based crack sealant viscosity at installation temperature is suggested. This paper proposes use of a rotational viscometer to measu...

VISCOELASTIC MODELING OF STRAIGHT RUN AND MODIFIED BINDERS USING THE MATCHING FUNCTION APPROACH

Two models are proposed to describe the rheological behavior of straight run and modified binders in the linear viscoelastic region. These models characterize the absolute value of the complex shear modulus (| G *|) and the phase angle ( i ). They allow for the establishment of master curves based on measurements made at a limited number of loading times and temperatures. A matching function approach was used to develop the models, which were validated experimentally by characterizing the dynamic mechanical properties of polymer-modified and straight run binders at intermediate and high service temperatures. There was good agreement between the measured and predicted values for the complex shear modulus. The phase angle model describes unmodified binders with less than 5% error. Although the model does not simulate the plateau region observed for polymer-modified binders, the error in this case was less than 10%. The models were successfully used to estimate other viscoelastic functions such as the storage and loss shear moduli, and the relaxation spectrum.

Accelerated Aging of Bituminous Sealants: Small Kettle Aging

Bituminous sealants used in the maintenance of roadways are installed hot and heated to 150–200°C during installation. High temperatures can degrade polymers in sealants, but there is no standard method to account for this possible degradation. In an attempt to find such a method, the aging of two sealants in large kettles during field applications was compared to that obtained in the laboratory by heating in a small kettle. The results indicate that 4 h of small kettle aging at the highest suggested sealant application temperature (HiSAT), or about 2 h at HiSAT + 10°C, provided as much copolymer aging as that found in sealants sampled midway through installation.

Low-temperature characterization of hot-poured crack sealant by crack sealant direct tensile tester

The current specifications for selecting crack sealants correlate poorly with actual field performance. To address this issue and assist in predicting the low-temperature properties of hot-poured bituminous crack sealants, a modified direct tensile tester method has been developed. Sample geometry is modified to accommodate testing sealants. A sensitivity analysis considering various loading rates, sample lengths, and cross-section areas was conducted to define both optimized specimen geometry and testing protocol. Two types of sealants, having a wide range of rheological behaviors (one polymer-modified and one having crumb rubber), were tested at low temperature. Results showed that the rich polymer–modified sealant has a high resistance to failure compared with the sealant with crumb rubber–modified. Each sealant was tested at the lowest corresponding expected service temperature. A performance parameter, strain energy density, was proposed to differentiate crack sealant material in the laboratory.

Early Thermodegradation of Bituminous Sealants Resulting from Improper Installation: Field Study

Bituminous sealants used in roadway maintenance often have a short effective service life, in great part as a result of improper installation and heating, in particular. To determine the effect of thermal history on sealant characteristics, sealant samples were collected during an operation that started with reheating of a full kettle of bituminous sealant. Results of Fourier transform infrared spectroscopy, thermogravimetry, gel permeation chromatography, and dynamic shear rheometry showed that the sealant had degraded and that the extent of degradation was greatest early in the operation. Application of degraded sealant throughout installation showed the need for improved material and construction specifications, along with improved field control measures.

Cooling rates in hot-poured bituminous sealants

The performance of bituminous sealants applied to cracks and joints is partly governed by installation. An important installation parameter yet to be investigated is the sealant rate of cooling after it is poured hot. Cooling rates affect sealant microstructure and rheology, adhesion at the sealant-hot-mix asphalt interface, and the time during which traffic must be rerouted. To provide data on sealant cooling rates, the temperature change in three sealants was measured in the field and in the laboratory. Results indicated that sealant bulk temperatures were >50°C lower than the sealant application temperature, typically 180°C, almost immediately after pouring, and that sealant bulk temperatures reached 40°C or less within 15 min. This finding suggests that traffic could be rerouted for less time than the standard 30 min. The instantaneous sealant temperature at the sealant-substrate interface was also measured to be below 100°C immediately after pouring of the sealant. This finding emphasizes the need fo...

Effect of Bituminous Material Rheology on Adhesion

Bituminous materials are used in many civil engineering applications in which adhesion to a substrate is essential for good performance. Yet it is not possible to predict the adhesion of these materials. The particular case of bituminous crack sealants is of interest; the effect of sealant viscosity, aging, test temperature, and loading rates was investigated by means of a blister test. This test provided the bonding characteristics to a model aggregate in relation to interfacial fracture energy (IFE). From testing of several sealants, it was found that pouring viscosity affects adhesion and that higher viscosities help to attain higher IFEs. Temperature was found to play a key role on bonding characteristics and failure mechanism because it affected the viscoelastic properties of the sealant. The glass transition temperature (Tg) was found to have a governing role on bonding characteristics. At temperatures above Tg, bond strength was found to be affected by sealant flow such that failure was flow related; that is, cohesive failure prevailed. At temperatures below the Tg, at which sealants were stiff and bulk deformation was low, stress was directed toward the interface so that failure tended to be adhesive. In taking into account temperature and test rates, an IFE master curve was obtained for a sealant. Such a curve may be used in predicting and comparing sealant IFE.