Preparation and Characterization of Nitrate-Sulfate-Based Concrete Antifreeze Using Cement Kiln Dust: Economic and Performance Analysis

Statement of the problem. Winter concrete construction requires antifreeze admixtures that prevent freezing while maintaining strength development. Conventional nitrite- and chloride-based antifreezes face high costs and corrosion concerns. Industrial by-products like cement kiln dust (CKD) offer potential for sustainable antifreeze production, yet their application in nitrate-sulfate composite systems remains unexplored. A CKD-based nitrate-sulfate composite antifreeze was synthesized by reacting CKD-lime suspension with mixed HNO₃:H₂SO₄ (1:1 ratio) to yield a 40 % solids suspension containing KNO₃, Ca(NO₃)₂, K₂SO₄, CaSO₄, and 0.05 % triethanolamine. Performance was evaluated at three temperature ranges (–4 to –6 °C, –9 to –11 °C, and –14 to –16 °C)against four commercial antifreeze formulations through standardized testing of compressive strength, setting time, water absorption, frost resistance, and outdoor durability. Economic analysis compared production costs with commercial alternatives. Results. At –9 to –11°C, 5—6 % dosage prevented freezing and achieved 28-day strengths of 6.2 MPa, comparable to commercial calcium nitrate-based antifreeze (6.0 MPa) and superior to potassium carbonate-based (5.7 MPa) and calcium chloride-based (5.9 MPa) products. Setting time decreased by 50 %, water absorption reduced by 15 %, and freeze-thaw resistance improved from 28 to 46—47 cycles. Production costs of $95—105 per metric ton represent 78—82 % savings compared to commercial antifreezes ($420—480 per ton), translating to $735 savings per 100 m³ concrete. Conclusions. The CKD-based composite antifreeze demonstrates comparable or superior performance to commercial products while achieving substantial cost reduction through industrial waste valorization. Recommended dosages are 3—5 %, 5—7 %, and 8—10 % by cement weight for –4, –10, and –15 °C environments, respectively.