*Article*

#### **Impact of Temperature Changes and Freeze—Thaw Cycles on the Behaviour of Asphalt Concrete Submerged in Water with Sodium Chloride**

**Ánge<sup>l</sup> Vega-Zamanillo 1, Luis Juli-Gándara 1,\*, Miguel Ánge<sup>l</sup> Calzada-Pérez 1 and Evelio Teijón-López-Zuazo 2**


Received: 21 January 2020; Accepted: 9 February 2020; Published: 12 February 2020

**Abstract:** One of the main applications of salt in civil engineering is its use as a de-icing agen<sup>t</sup> on roads in cold areas. The purpose of this research is to find out the mechanical behaviour of an asphalt concrete when it is subjected to temperature changes and freeze–thaw cycles. These temperature interactions have been carried out for dry specimens, specimens submerged in distilled water and specimens submerged in salt water (5% of sodium chloride, NaCl). An AC16 Surf D bituminous mixture was evaluated under three types of temperature interaction: three reference series remained at a controlled temperature of 20 ◦C, another three series were subjected to five freeze–thaw cycles and the last three series have been subjected to one year outside in Santander (Spain). The mechanical behaviour of the mixture was determined by Indirect Tensile Strength Test (ITS), Water Sensitivity Test (ITSR) and Wheel Tracking Test, Dynamic Modulus Test and Fatigue Tests. The results of the tests show that, although the temperature changes have a negative effect on the mechanical properties, salt water protects the aggregate-binder adhesive, maintains the mechanical strength, increases the number of load cycles for any strain range and reduces the time that the mixture is in contact with frozen water.

**Keywords:** salt; NaCl; asphalt concrete; freeze–thaw cycles; winter road

**Highlights:** Specimens of hot mix asphalt were evaluated under different temperature changes, including freeze–thaw cycles. Temperature changes have a harmful effect on the behaviour of the mixture, but the amount of time that the mixture is submerged in contact with salt water is the main mechanism of damage. Salt water protects the aggregate-binder adhesive, maintains the mechanical strength, increases the number of load cycles for any strain range and reduces the time that the mixture is in contact with frozen water.
