Search results for " Mix design"
showing 6 items of 6 documents
Towards a new mix design method for asphalt mixtures containing rap
2016
Recycling is one of the most important aspects to conceive the new construction or rehabilitation of sustainable road infrastructures. Even if Reclaimed Asphalt Pavement (RAP) is commonly used in the practice, its presence may lead to some critical aspects due to the physical and chemical phenomena occurring during the new mix process. For instance, the formation of RAP clusters during a new mix may inhibit the uniform distribution of the virgin binder as well as cause changes in the design grading curve of the mixture. Indeed, laboratory results demonstrate that small-size RAP particles stick together forming clusters. The amount of clusters depends on different parameters observed: The pe…
Analytical approach for the mix design optimisation of bituminous mixtures with crumb rubber
2018
The present paper provides a basis for defining a mix design method specifically tailored to rubberised asphalt that takes into account the behaviour of crumb rubber. An analytical approach to quantifying the recovered deformation of crumb rubber in the post-compaction phase has been developed in order to adjust the number of gyrations proposed by the Superpave method for compacting specimens of hot mix asphalt using a Superpave gyratory compactor. The maximum allowable amount of rubber has been calculated. Finally, a step-by-step protocol has been proposed in order to fabricate and compact crumb rubber modified mixtures with the gyratory compactor.
Design considerations of high RAP-content asphalt produced at reduced temperatures
2018
In many countries recycling of reclaimed asphalt pavement (RAP) for road surface layers is limited to a maximum of 10–30%. This is due to technical limitation of common asphalt plant but also to specifications that are still restrictive when it comes to increasing RAP in surface courses. The mistrust in this practice is mainly related to uncertainty in performance of these mixes as well as to existing fundamental issues with the mix design, especially when production temperatures are lowered. This paper analyses some of the factors affecting the design of warm asphalt mixtures for surface course layers containing 50% RAP, and suggests a framework to justify the common assumption of full ble…
EXPERIMENTAL INVESTIGATION ON DRY ASPHALT RUBBER FOR SUBBALLAST
2011
The asphalt rubber mixes have a wide application field in the railroad and road superstructures because of their technical and environmental properties. While in many countries the wet process is often used to make bituminous mixtures, the dry process doesn’t have the same degree of application even though a larger recycling of waste tires rubber is allowed than the dry process. This paper focuses on the mix-design of the Dry Asphalt Rubber (DAR) for subballast of the railroad superstructure in order to define a sound laboratory procedure of mix-design with reference to Marshall test and Superpave Gyratory Compactor (SGC) test. The comparison between Marshall test and SGC test highlights th…
Revealing the nature of metakaolin-based concrete materials using artificial intelligence techniques
2022
In this study, a model for the estimation of the compressive strength of concretes incorporating metakaolin is developed and parametrically evaluated, using soft computing techniques. Metakaolin is a component extensively employed in recent decades as a means to reduce the requirement for cement in concrete. For the proposed models, six parameters are accounted for as input data. These are the age at testing, the metakaolin percentage in relation to the total binder, the water-to-binder ratio, the percentage of superplasticizer, the binder to sand ratio and the coarse to fine aggregate ratio. For training and verification of the developed models a database of 867 experimental specimens has …
La qualità fiorisce anche nel piccolo cantiere edile
2013
I calcestruzzi “ad alte prestazioni meccaniche” sono in genere associati a tecnologie di produzione e posa in opera complesse; si cerca spesso di giustificare in tal modo carenze esecutive e prestazionali, anche di opere alle quali si richiedono valori di resistenza che ormai possono considerarsi ordinari; del resto la definizione di conglomerato “ad alta resistenza meccanica” è strettamente legata all’epoca di produzione. La sperimentazione esposta nella presente pubblicazione definisce la composizione di una miscela che raggiunga una resistenza meccanica a compressione quanto più alta possibile, adoperando per il suo confezionamento una comune betoniera a bicchiere e scegliendo opportunam…