*Article* **Sti** ff**ness Identification of Foamed Asphalt Mixtures with Cement, Evaluated in Laboratory and In Situ in Road Pavements**

### **Lukasz Skotnicki \*, Jarosław Ku ´zniewski and Antoni Szydlo**

Roads and Airports Department, Faculty of Civil Engineering, Wroclaw University of Science and Technology, 50-370 Wroclaw, Poland; jaroslaw.kuzniewski@pwr.edu.pl (J.K.); antoni.szydlo@pwr.edu.pl (A.S.) **\***Correspondence:lukasz.skotnicki@pwr.edu.pl;Tel.: +48-71-320-45-38

Received: 7 February 2020; Accepted: 2 March 2020; Published: 3 March 2020

**Abstract:** The article presents the possibilities of using foamed asphalt in the recycling process to produce the base layer of road pavement constructions in Polish conditions. Foamed asphalt was combined with reclaimed asphalt pavement (RAP) and hydraulic binder (cement). Foamed asphalt mixtures with cement (FAC) were made, based on these ingredients. To reduce sti ffness and cracking in the base layer, foamed asphalt (FA) was additionally used in the analyzed mixes containing cement. The laboratory analyzes allowed to estimate the sti ffness and fatigue durability of the conglomerate. In the experimental section, measurements of deflections are made, modules of pavement layers are calculated, and their fatigue durability is determined. As a result of the research, new fatigue criteria for FAC mixtures and correlation factors of sti ffness modules and fatigue durability in situ with the results of laboratory tests are developed. It is anticipated that FAC recycling technology will provide durable and safe road pavements.

**Keywords:** recycling; foamed asphalt mixtures with cement (FAC); base layer; reclaimed asphalt pavement (RAP); fatigue durability
