Journal of Building Engineering 34 (2021) 102055 Available online 2 December 2020 2352-7102/© 2020 Elsevier Ltd. All rights reserved. Infuence of binary antifreeze admixtures on strength performance of concrete under cold weather conditions Jeeshan Khan * , Santha Kumar G. CSIR-Central Building Research Institute, Roorkee, 247 667, India A R T I C L E INFO Keywords: Cold weather exposures Mortar Concrete Antifreeze admixtures Freezing and water revitilization ABSTRACT The present research addresses the infuence of using binary antifreeze admixtures on the strength performance of concrete under different curing exposures of cold weather conditions. A comparison with the strength per- formance of controlled concrete under the curing exposures of cold weather conditions is also explored. Calcium nitrate and sodium thiocyanate were the binary antifreeze admixtures used in the present study. Concrete specimens were cured at different cold weather conditions such as, 1) freezing temperature of -5 ◦ C and 10 ◦ C, 2) freezing temperature of -5 ◦ C and 10 ◦ C along with water revitalization, 3) freezing and thawing cycles, 4) freezing and thawing cycles along with water revitalization. The present study inferences that the synergetic use of calcium nitrate and sodium thiocyanate have a great infuence on strength enhancement of concrete under the infuence of various curing exposures of cold weather conditions that would be a constructive solution to pro- mote the concrete applications in cold weather conditions. 1. Introduction ACI 306 states cold weather when following climatic conditions exist for the period of more than three consecutive days: the temperature below 4 ◦ C and air temperature drops below 10 ◦ C for one-half of 24 h [1]. The major drawbacks associated with the cold weather curing exposure of concrete are prolonged setting time, early damage, slow hydration, low strength gain and generation of thermal cracks etc [2,3]. During the exposure of fresh concrete under cold weather conditions, the mixing water inside the concrete tends to become ice, affecting its setting characteristics. It is because, the conversion of hydration product from ettringite to monosulphate is predominantly affected [4,5]. During the exposure of hardened concrete under cold weather conditions, the water inside the concrete pores generally tends to become ice, causing an increase the volume around 9% [6,7]. These effects exert pressure to outward direction, creating high hydraulic pressure to the sorroundings. Therefore, concrete is protected against freezing during plastic and hardened states until achieving suffcient setting and hardening [8–10]. However, cold weather concrete attains substainially inferior perfor- mance due to freezing of water during plastic and hardened states [11] and therefore, it requires to be protected from freezing through: a) using antifreeze admixtures, b) heating of raw materials and c) providing insulation over concrete surface etc [12,13]. Among these methods, the incoroporation of antifreeze admixtures in concrete under the curing exposure of cold weather is economical and also feasible to applicable in wide applications [14]. The use of antifreeze admixtures, such as, sodium chloride, sodium nitrite, alcohol based compounds, carbamide, calcium chloride, calcium nitrate and urea, had tendency to reduce the freezing point of the aqueous solution, causing positive impact on performance enhancement of concrete in cold weather conditions [7,13,15–18]. However, the performance of cold weather concrete improved to full extent is still questionable. Prolonged setting and slow hardening are the pressing issues of cold weather concrete and therefore, the synergetic use of setting and hardening admixtures are essential for developing the desirable performance of cold weather concrete. Calcium nitrate is a multifunctional admixture for concrete which can be used as setting accelerator, antifreeze admixture and corrosion inhibitor etc [19]. So- dium thiocyanate (NaSCN) is a sodium salt of thiocyanic acid (HSCN) and used as hardeneing accelerator [20]. The synergetic use of setting and hardening accelerators on the performance of cold weather concrete is yet to be investigated. In addition to this, there have been insuffucient knowledge on the performance of concrete exposed under various curing exposures of cold weather conditions. Keeping consideration of these concerns, the objective of this present paper is to investigate the infuence of using binary antifreeze admixtures on the performance of * Corresponding author. E-mail addresses: jeeshank@cbri.res.in (J. Khan), santhakumar@cbri.res.in (S.K. G.). Contents lists available at ScienceDirect Journal of Building Engineering journal homepage: http://www.elsevier.com/locate/jobe https://doi.org/10.1016/j.jobe.2020.102055 Received 28 August 2020; Received in revised form 30 November 2020; Accepted 30 November 2020