Water or moisture in different physical states is a major factor that contributes to various forms of damages in asphalt concrete (AC) pavements. For pavement design and maintenance, it is essential to evaluate the AC mixtures with respect to water/ moisture damage susceptibility. In Sweden, this is currently done according to the Swedish standard (TDOK 2017:0650) or alternatively can be done according to the European standard (SS-EN 12697-12). However, these methods are time consuming, and they do not simulate the pumping action of water due to passing wheels. On the other hand, the Moisture Induced Sensitivity Test (MIST) is intended to be a quick method that applies cyclic pore pressure to simulate the repeated pumping action of water. However, it is a relatively new approach that has not yet been properly studied for Swedish conditions and yet to be standardized in Europe. 

In this project, the MIST, TDOK and the EN methods were evaluated using five different AC mixes. Results showed that the MIST with 12,000 cycles and the TDOK method have comparable and the strongest effect on the stiffness properties. MIST with 3,500 and 7,000 cycles and the EN method showed identical and relatively weak impact of water. MIST also indicated the changes of the indirect tensile strengths of the specimens. However, compared to the TDOK or EN methods, the changes in the indirect tensile strengths due to MIST conditioning were smaller. Overall, MIST was concluded to be a quicker, more convenient and a more realistic alternative. Comparing the various mixes with respect to moisture sensitivity, binder content and air voids showed great influences. The specimens with cut surfaces were less affected by moisture conditioning. The addition of amine additives significantly improved the resistance to moisture damage of the mixes. Generally, the results of this study formed the basis for further development of the EN and TDOK method as well as standardizing the MIST conditioning method in Europe.

Vatten och fukt är en av faktorerna som bidrar till olika former av skador i asfaltbeläggningar (AC). Vid val och kvalitetskontroll av beläggning är det viktigt att utvärdera den med avseende på vattenkänslighet. I Sverige görs detta för närvarande enligt den svenska standarden (TDOK 2017: 0650) och i Europa enligt den europeiska standarden (SS-EN 12697-12). Dessa metoder är emellertid tidskrävande och de simulerar inte vattnets dynamiska portryck i beläggningen som uppkommer när hjul passerar över. En ny metod, Moisture Induced Sensitivity Test (MIST) är en snabb metod som inducerar cykliskt portryck i provkroppen för att simulera pumpning av vatten i en beläggning. Metoden har ännu inte studerats ordentligt för svenska förhållanden och den är ännu inte en standardiserad metod i Europa. 

I detta projekt utvärderades MIST-, TDOK- och EN-metoderna med hjälp av fem olika asfaltmassor. Resultaten visade att MIST med 12 000 cykler och TDOK-metoden gav jämförbara och starkaste effekter på styvhetsegenskaperna. MIST med 3 500 och 7 000 cykler och EN-metoden visade identisk och relativt svag inverkan av vattenkonditionering. MIST indikerade också förändringarna av provens indirekta hållfasthet. Men jämfört med TDOK- eller EN-metoderna var förändringarna i indirekt hållfasthet på grund av MIST-konditionering mindre. Sammantaget verkade MIST vara en snabbare, lättare och mer realistisk metod än de övriga metoderna för att utvärdera vattenkänslighet hos asfaltsbeläggningar. Bland asfaltmassorna var de med det mjukare bindemedlet och med lägre bindemedelshalt de mest påverkade. Asfaltmassan med högre hålrum var också mer påverkad än tätare provkroppar. Proverna med sågade ändytor påverkades mindre än de med osågade ändytor. Tillsats av vidhäftningsmedel (amin) förbättrade avsevärt motståndet mot fuktskador hos massorna. Resultaten av denna studie ger underlag för fortsatt utveckling av EN- och TDOK-metoderna samt argument för att standardisera MIST-konditioneringsmetoden i Europa.

This article presents a model for the permanent deformation (PD) behavior of unbound granular materials (UGMs) used in the base and subbase layers of pavement struc- tures. The model was developed based on multistage (MS) repeated load triaxial (RLT) test- ing. This is essentially a modified version of a previously developed model to better suit to field conditions in a simple and effective manner. The model was calibrated for eight com- monly used UGMs using MSRLT tests with a range of moisture contents. For validation, the calibrated models were used to predict the PD behavior of three of the UGMs in MSRLT tests with stress levels and moisture contents different from those used during the calibrations. This model showed better quality of fit when compared with another widely used PD model. The model was further tested successfully for field conditions by capturing the PD behavior of an instrumented pavement test section in a controlled environment using a heavy vehicle simu- lator (HVS) based accelerated pavement testing (APT). Inputs for calibrating the model were based on the readings from the instrumentations. The parameters of the model were adjusted to match the measured data with the predictions. Based on these results for various design conditions, some ranges of values of the material parameters of the model were suggested.

Utförandet av en vägbeläggning har stor betydelse för hållbarheten. Separation i massabeläggningar leder till kortare livslängd på asfaltbeläggningar och för tidigt uppkomna skador har ofta ett direkt samband med hur väl utfört beläggningsarbetet är. Svårigheten med separationsproblemet ligger i att det saknas lätthanterliga och objektiva praktiska metoder för bestämning av separationsgrad och dess effekt på hållbarheten. Under senare år har vägytemätbilar använts för mätning av makrotextur med måttet MPD (Mean Profile Depth). Korrelationen mellan MPD-värden och styvhetsmodul antyder att MPD-mätvärden skulle kunna vara en praktisk och snabb metod för utvärdering av kvaliteten hos utfört arbete. Ett begränsat antal fallviktsmätningar utfördes på positioner med olika separationsgrad i AG-lagret (Asfaltbundet Grus). Det konstaterades en tendens till inverkan av separation i AG-lagret på fallviktsdata även om det fanns en variation i data. I denna studie presenteras ett tillvägagångssätt för detektering av ytor med hög makrostruktur. Fast MPD-värden bara beskriver ytans textur, kan det användas för en snabb skanning av separerade ytor i det översta beläggningslagret. Begränsad och riktad provtagning kan därefter utvärderas för mer exakt bestämning av separationsgrad och dess effekt på livslängden/ hållbarheten.

Non-destructive testing in quantifying the asphalt pavement layers homogeneity can be used for the quality assurance in paving contracts. This paper summarizes the findings from a field study on segregation in bituminous pavement mixes that relates pavement layer surface texture to the homogeneity of the paved bituminous layer by distinguishing mix segregated area. The mean profile depth (MPD) values of paved layer were measured. Based on these values three locations on the road were identified having low, intermediate and high MPD values. Thereafter, cored samples were tested for stiffness modulus before and after moisture conditioning by performing the moisture induced sensitivity test (MIST). Results clearly showed that the samples from the locations with high MPD values were mostly affected by the moisture conditioning for which the stiffness moduli were significantly reduced. The samples with high MPD values had the highest air voids as well. Thus, this study demonstrated that construction quality described by segregation in the paved asphalt mix has a significant impact on the moisture sensitive performance of pavements. A limited number of falling weight deflectometer (FWD) measurements were performed at positions with different degree of separation in the road base layer. There was a tendency for the effect of separation in the road base layer on FWD even though there was a variation in data. The strong correlation between the MPD values and change in stiffness modulus also suggests that the measurements of the MPD values can be a reliable and non-destructive method for evaluating the construction quality of a pavement and in developing the quality assurance criteria based on pavement performance that can be used in paving contracts.

The unbound granular layers (UGM's) and the subgrade of a pavement structure provide a significant support for the structure as a whole. Hence the mechanical properties of these materials are important for the overall performance of the structure. These materials exhibit both non-linear stress dependency and their mechanical properties are highly affected by their moisture content. This paper describes two of the most important material properties of the unbound layers of the pavements, i.e. the resilient and the permanent deformation properties. The stress dependency of UGMs can be captured by the universal model or the enhanced model by Cary and Zapata (2011) for materials with high fine content. The Bishop's effective stress approach can be used for high fine content materials for estimating the effect of suction. UGMs and subgrade materials are further highly dependent on moisture content. Either the AASHTO sigmoidal model can be used to describe the moisture dependency or the simple exponential model described in this paper. The paper further discusses four models to characterize the accumulation of permanent deformation with the number of load repetitions in repeated load triaxial (RLT) testing. The models are all developed to fit single stage (SS) RLT test results but have been extended to fit multi-stage (MS) RLT test results with the aid of the time hardening scheme. The advantage of the MS RLT tests over the SS RLT tests is that it applies a range of stress paths on a single specimen, thus taking into account the effect of stress history and reducing the time and effort required to test a separate specimen for each stress path.