Institute of Fundamental Technological Research

Salt solutions are used on pavement surfaces during wintry weather events to guarantee safe driving conditions. In addition to sodium chloride (NaCl) which continues to be traditionally used as deicer, the usage of solutions of calcium chloride (CaCl2) and magnesium chloride (MgCl2) is on the increase due to need provide a more consistent ice and snow control and thus ensure safety of the travelling public. This paper assesses the effects of three different salt solutions (NaCl, CaCl2, and MgCl2) on several physical and mechanical properties of pavement concretes. These deicing solutions were used under simulated wetting-drying (WD) and freezing-thawing (FT) exposure regimes with total ion concentration of the deicers was 10.5 molal for WD exposure and 5.5 molal for FT exposure.
Two types of concretes were used in the study; the ordinary portland cement concrete and the fly ash concrete (20% of cement replacement by mass). The prismatic and cylindrical specimens were used to monitor physical changes due to these exposure regimes. The physical changes of cylindrical specimens subjected to the WD regime were monitored by taking ultrasonic pulse velocity (UPV) measurements after every 2 weeks of exposure and crushing these cylinders at the end to obtain the compressive strength. The effects on prismatic specimens were monitored by measuring mass and resonant frequencies after every 2 weeks of exposure and using these data to calculate changes in the relative dynamic modulus of elasticity (RDME). The test results obtained from the RDME and UPV measurements, combined with visual observations were used to assess the effects of deicers on concretes. It was observed that CaCl2 solution is more harmful as compared to MgCl2 solution for both plain and fly ash modified concretes.

Deicing Salt Solutions, Pavement Concretes

Salt solutions are employed on pavement surfaces throughout wintry weather environment to guarantee safe driving conditions. Recently, deicing solutions of CaCl2 or MgCl2 (or sometimes rock salt (NaCl) pretreated with CaCl2 or MgCl2 brines,) are used to provide a more consistent ice and snow control. This paper assesses the effects of more prevalently used salt solutions on the microstructure and physical parameters (strength, expansion and mass) of pavement concretes. Deicing solutions of NaCl, CaCl2, and MgCl2 were used for wetting-drying (WD) and freezing-thawing (FT) conditions with total ion molality of 10.5 and 5.5 respectively.
The prismatic and cylindrical specimens were used to monitor physical changes due to these regimes and later on microstructural analysis was performed on them after the completion of exposure. The changes on cylindrical specimens due to WD regime were monitored by taking UPV measurements and crushing these cylinders at the end for compressive strength. The effects on prismatic specimens were monitored by measuring mass and resonant frequencies after every 2 weeks and used for calculating relative dynamic modulus of elasticity.
To study unidirectional penetration of deicers, several 3 in. (76 mm) diameter concrete cylinders were ponded with the deicing solutions in WD environment. These cylindrical specimens were used for SEM analysis and chloride profile grinding after end of the exposure. The microstructure of prismatic concretes specimens exposed to 350 FT cycles was observed using personnel SEM from two locations (one from the center and other from the edge) of the after conclusion of the both exposure conditions.

Physical Parameters, Pavement Concretes, Salt Solutions

The deicing/anti-icing chemicals are routinely used during cold weather to ensure safe driving conditions. Traditionally, solid rock salt (NaCl) or NaCl brines have been used for these purposes but their efficiency is reduced at lower temperatures. In order to provide a more reliable means of ice and snow control, chemicals with lower freezing points, such as CaCl2 or MgCl2 (or sometimes rock salts pretreated with CaCl2 or MgCl2 brines) are increasingly being applied. The extent and magnitude of chemical reactions of these “new-generation” deicers with pavement concrete is still somewhat unclear. This paper presents the results of investigation of the physicochemical changes in the microstructure of pavement concrete exposed to different deicers and subjected to both wetting/drying (W/D) and freezing/thawing (F/T) regimes.
Plain concretes (PC) and fly ash modified concretes (20% mass replacement of cement) with water-to-cementitious materials ratio of 0.42 were exposed to three different types of deicing solutions, with total ion molality of, respectively, 10.5 for W/D and 5.5 for F/T regimes. For comparison purposes, additional set of specimens was kept in deionized water under similar exposure regimes. The companion controlled specimens were kept in saturated limewater at 23oC. The physical changes taking place in the prismatic (3” x 3” x 11.5”) specimens were monitored weekly and included measurements of dynamic modulus of elasticity (RDME) and mass changes. After 154 W/D cycles prismatic specimens exposed to 28% CaCl2 solution exhibited considerable visual distress, reduction in mass, and reduction in DME. The same deicer also caused reduction in mass and in DME after only 35 F/T cycles. The performance of fly ash modified concretes was better than that of PC in all deicing solutions under both W/D and F/T regimes.
To ensure a unidirectional penetration of deicers, several 3–in. diameter concrete cylinders were ponded with the same deicing solutions as the prismatic beams while being exposed to W/D cycles. These cylinders were used to prepare the SEM analysis samples.

plain concrete, fly ash concrete, deicing salts, pavement concrete