Towards the development of a standard test protocol : application of the MMLS3 for evaluating the performance of surfacing seals

Abrahams, Mohammad Shafee (2015-12)

Thesis (MSc)--Stellenbosch University, 2015.

Thesis

ENGLISH ABSTRACT: For a road to perform optimally, both functionally and structurally; a durable, waterproof, skid-resistant, all-weather and dust-free surfacing is required to provide the road user with an acceptable level of service. Surfacing seals serve to protect the structural layers of the pavement from the abrasive forces of traffic and from the detrimental effects of the environment especially moisture. Surfacing seal design, in South Africa, and many parts of the world is governed mainly by empirical rules and experience guided practices. There is thus a need for a performance related seal design method, with a more scientific foundation. This study aims to address this challenge by investigating the failure mechanisms of seals with the aim of simulating its manifestation using an accelerated pavement tester, the Model Mobile Load Simulator (MMLS3). Based on this investigation, seal stone embedment was identified as the target failure mechanism. Key seal variables were identified which are thought to directly influence the embedment of the stones in a seal. This research project was then centred around this failure mechanism and an experimental seal testing setup was developed along with an analysis procedure to measure and quantify the embedment of the stones in a seal. Based on the literature study the factors influencing the performance of seals were identified along with the capabilities of the MMLS3 for application on seals. The following key seal design parameters were identified and selected for comparison: - Tack coat binder type - Aggregate spread rate configuration - Aggregate size A seal construction method was developed along with a software aided embedment calculation method for use with the Laser Texture Meter (LTM). This integral part of this study allowed for the processing of large amounts of data obtained from the LTM and subsequent analysis of the processed data. Based on the analysis of the data it was established that more than 70% of the total embedment observed over 100 000 load cycles occurred during the initial embedment period i.e. the first 10 000 load cycles. The statistical analysis also provided an idea as to the level of influence of the variables on the embedment measured. The following was noted: - Aggregate configuration showed the lowest influence - Binder type showed an intermediate influence - Aggregate size showed the highest influence This study shows that with an effective testing setup and an efficient analysis procedure, the application of the MMLS3 can successfully be used for evaluating the performance of surfacing seals. Through further research and refinement the development of an effective accelerated seal testing protocol would be possible. Such a protocol should able to quantify and analyse the performance of seals. The major recommendations for the improvement of similar research include: - The inclusion of more testing variables allowing a greater comparative scope. - The use of more precise laser measurement technology with capabilities extending beyond the LTM used in this study. - The establishment of performance index parameters to quantify and rank the variables investigated from which an acceptable protocol can be developed.

AFRIKAANSE OPSOMMING: Vir 'n pad om optimaal te presteer , beide funksioneel en struktureel ; 'n duursame , waterdigte , slip bestand, alweerstand en stof-vry oppervlak is nodig om die padgebruiker te voorsien met 'n aanvaarbare vlak van diens. Oppervlakseël dien om die strukturele lae van die plaveisel te beskerm teen die skuur kragte van die verkeer en die nadelige gevolge van die omgewing Oppervlakseël ontwerp, in Suid-Afrika , en baie dele van die wêreld word hoofsaaklik beheer deur empiriese reëls en ervaring geleide praktyke . Daar is dus 'n behoefte aan 'n prestasie -verwante oppervlakseëlontwerpmetode, met 'n meer wetenskaplike grondslag . Hierdie studie het ten doel om hierdie uitdaging aan te spreek deur die ondersoek na die mislukking meganismes van oppervlakseël met die doel van sy manifestasie simuleer met behulp van 'n versnelde plaveisel toetser, die Model Mobile Lassimulator ( MMLS3 ) . Op grond van hierdie ondersoek, is oppervlakseëlklip ingebedheid geïdentifiseer as die teiken mislukking meganisme. Sleutel oppervlakseël veranderlikes was geïdentifiseer wat gedink is, is die direkte ïnvloed op die ingebedheid van die klippe in 'n oppervlakseël. Hierdie navorsingsprojek is toe gesentreer rondom hierdie mislukking meganisme en 'n eksperimentele Oppervlakseël toets opstel, ontwikkel saam met 'n ontleding prosedure te meet en te kwantifiseer in die ingebedheid van die klippe in 'n oppervlakseël. Gebaseer op die literatuurstudie, die faktore wat die prestasie van oppervlakseël was geïdentifiseer saam met die vermoëns van die MMLS3 vir toepassing op oppervlakseëls. Die volgende sleutel oppervlakseël ontwerp parameters is geïdentifiseer en gekies vir vergelyking : - Seëlbindmiddel tipe - Oppervlakseëlklip verspreiding koers opset - Oppervlakseëlklip grootte ‘n Oppervlakseël konstruksie metode was ontwikkel saam met 'n sagteware aangehelpte ingebedheid berekening metode met die gebruik van die Laser Tekstuur Meter ( LTM ). Die integrale deel van hierdie studie is toegelaat vir die verwerking van groot hoeveelhede data verkry is uit die LTM en daaropvolgende ontleding van die verwerkte data. Gebaseer op die ontleding van die data is vasgestel dat meer as 70 % van die totale ingebedheid waargeneem, van die 100 000 vrag siklusse wat plaasgevind het tydens die aanvanklike ingebedheid tydperk dws die eerste 10 000 vrag siklusse. Die statistiese analise ook voorsien 'n idee as die vlak van die invloed van die veranderlikes op die ingebedheid gemeet . Die volgende is opgemerk : - Oppervlakseëlklip opset het die laagste invloed - Seëlbindmiddel tipe het 'n intermediêre invloed - Oppervlakseëlklip grootte het die hoogste invloed Hierdie studie toon dat met 'n effektiewe toets opstel en 'n doeltreffende ontleding prosedure , die toepassing van die MMLS3 kan suksesvol gebruik word vir die evaluering van die prestasie van oppervlakseëls. Deur verdere navorsing en verfyning van die ontwikkeling van 'n doeltreffende versnelde oppervlakseël toets protokol moontlik sou wees. So 'n protokol moet in staat wees om te kwantifiseer en die prestasie van oppervlakseël te ontleed. Die groot aanbevelings vir die verbetering van soortgelyke navorsing sluit in: - Die insluiting van meer toets veranderlikes sodat 'n groter vergelykende omvang. - Die gebruik van meer akkurate lasermetingtegnologie met vermoëns om buite die LTM gebruik in hierdie studie, uit te brei. - Die vestiging van prestasie-indeks parameters om te kwantifiseer en die veranderlikes te gradeer wat ondersoek was, waaruit 'n aanvaarbare protokol ontwikkel kan word.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/97943
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