Karakteristike asfaltnih mešavina sa agregatom od recikliranog betona

Abstract

U cilju implementacije i promocije održivog razvoja u oblasti graditeljstva, sprovedena su obimna eksperimentalna ispitivanja kako karakteristika recikliranog agregata (RCA), tako i karakteristika asfaltnih mešavina sa delimičnom zamenom prirodnog agregata recikliranim. Reciklirani agregat koji je korišćen u istraživanju dobijen je drobljenjem originalnog cementnog betona klase čvrstoće C35/45. U cilju poboljšanja kvaliteta recikliranog agregata, krupan RCA (d>4 mm) je izložen tretmanima hlorovodoničnom kiselinom (potapanjem u 0.1 mol/dm3 HCl) i ubrzanoj karbonatizaciji (koncentraciji CO2 od 4%). Pomenutim tretmanima su u manjoj meri poboljšane karakteristike RCA, pa su dalja ispitivanja uticaja RCA na karakteristike asfalt betona sprovedena samo za netretirani RCA. Eksperimentalnim ispitivanjima je obuhvaćeno 10 asfaltnih mešavina. Osim kontrolne mešavine, formirane su tri grupe mešavina sa delimičnom zamenom sitnog (0/4 mm), krupnog (4/22.5 mm) i sitnog i krupnog (0/22.5 mm) prirodnog agregata recikliranim. Svaku grupu su činile mešavine sa tri različita sadržaja RCA: 15%, 30% i 45%. Projektovane su asfaltne mešavine za noseći sloj kolovozne konstrukcije AC 22 BASE sa ciljanim sadržajem šupljina ispunjenih vazduhom od 5.2%. Glavni deo eksperimentalnog rada je obuhvatio ispitivanje modula krutosti i otpornosti asfalntih mešavina na dejstvo vode, trajnu deformaciju, zamor i niske temperature. Dobijeni rezultati su pokazali da je moguća primena kompletnog RCA (i sitan i krupan agregat); da mešavine sa RCA imaju istu ili bolju otpornost na zamor u odnosu na kontrolnu mešavinu; i da je maksimalna količina RCA u manjoj meri ograničena otpornošću na niske temperature. Na osnovu analize dobijenih rezultata razvijena je metodologija za upotrebu RCA kao delimične zamene prirodnog agregata i date su preporuke za dalja istraživanja.

As a part of the implementation and promotion of sustainable construction development, large experimental research was conducted. This research included testing of the recycled concrete aggregate (RCA) and properties of asphalt mixtures in which this aggregate was applied as a partial replacement of the natural aggregate. Recycled concrete aggregate used in the conducted experiments was obtained by crushing of the original cement concrete (strength class C35/45). In order to improve it's quality, coarse RCA was exposed to the treatments with hydrochloric acid (by pre-soaking into 0.1 mol/dm3 HCl) and carbon dioxide (accelerated carbonation with 4% concentration of CO2). Mentioned treatments induced improvements in the properties of RCA, to a lesser extent. Therefore, only untreated RCA was used as a partial replacement of the natural aggregate in production of asphalt mixtures. Experimental research was conducted on the 10 different asphalt mixtures. Three groups of mixtures with RCA were tested in addition to the control mixture. In the first group, only fine aggregate (0/4 mm) was replaced by RCA; in the second group, the replacement was applied only to coarse aggregate (4/22.4 mm), while the third group included mixtures in which both fine and coarse aggregate were replaced by RCA. Each group included three different contents of RCA: 15%, 30%, and 45%. All asphalt mixtures were designed for the base course AC 22 BASE, targeting 5.2% of air entrained voids. Main part of the experiment consisted of different asphalt mixture’s testing, such as measurements of: the stiffness modulus, resistance to water, permanent deformation, fatigue and low temperatures. Obtained results show that application of the total (both fine and coarse) RCA is possible as mixtures with RCA expressed equal or improved fatigue resistance when compared to the referent mixture. Still, the amount of the RCA used should be limited according to its low temperatures resistance. Methodology for the RCA application, when it is used as a partial replacement of the natural aggregate in asphalt mixtures, was developed based on the presented results, together with guidelines for the future research.