Civil Engineering and Architecture 13(3A): 2657-2669, 2025 http://www.hrpub.org DOI: 10.13189/cea.2025.131333 Optimization of Reinforced Concrete for Cold Storage Facilities: An Experimental Analysis of the Influence of Polypropylene Fibers on Slabs under Low Temperature Melissa A. Pungtilan 1,* , Gilford B. Estores 2 1 School of Graduate Studies, Mapua University, Philippines 2 School of Civil, Environmental, and Geological Engineering, Mapua University, Philippines Received February 22, 2025; Revised April 30, 2025; Accepted May 27, 2025 Cite This Paper in the Following Citation Styles (a): [1] Melissa A. Pungtilan, Gilford B. Estores , "Optimization of Reinforced Concrete for Cold Storage Facilities: An Experimental Analysis of the Influence of Polypropylene Fibers on Slabs under Low Temperature," Civil Engineering and Architecture, Vol. 13, No. 3A, pp. 2657 - 2669, 2025. DOI: 10.13189/cea.2025.131333. (b): Melissa A. Pungtilan, Gilford B. Estores (2025). Optimization of Reinforced Concrete for Cold Storage Facilities: An Experimental Analysis of the Influence of Polypropylene Fibers on Slabs under Low Temperature. Civil Engineering and Architecture, 13(3A), 2657 - 2669. DOI: 10.13189/cea.2025.131333. Copyright©2025 by authors, all rights reserved. Authors agree that this article remains permanently open access under the terms of the Creative Commons Attribution License 4.0 International License Abstract With the present method adopted in the construction of cold storage in the Philippines, the introduction of fibers to slabs is limited, together with the suitable maximum aggregate size to attain the maximum compressive strength of concrete and prevent unwanted cracks. This study examined the effects of using 12.5 mm, 19 mm, and 25 mm maximum coarse aggregate sizes with 0%, 0.35%, 0.65%, and 1.00% polypropylene fiber (PPF) content. The average compressive strength on the 28 th day showed consistent improvement and was highest on the 19 mm coarse aggregate from 0%, 0.35%, and 0.65% fiber content. The Multiple Response Prediction model identified that a mix of 20 mm coarse aggregate size and 0.45% polypropylene fiber content can significantly enhance concrete’s compressive strength to 26.814 MPa on the 28 th day. Additionally, five slabs were fabricated to assess crack development at -25°C. Initial assessments showed gradual crack development within 14 days on slabs with 0% fibers. In contrast, slabs with 0.35%, 0.65%, and 1.00% fibers exhibited maximum crack widths of 0.256 mm, 0.085 mm, and 0.075 mm, respectively. The findings demonstrated that incorporating polypropylene fibers significantly reduces cracks in concrete slabs, thus enhancing their durability and performance in cold storage applications. Keywords Cold Storage, Compressive Strength, Low Temperature, Maximum Coarse Aggregate, Polypropylene Fiber 1. Introduction A cold storage facility is a thermal system designed to preserve and utilize perishable products. Items such as fruits, vegetables, meat, fish, and pharmaceutical products are stored under optimum low temperatures. It is made up of designed building space with refrigeration units, material handling provisions, and power generation units. According to Cold Chain Innovation Hub Philippines in 2020, there is a major shortage of post-harvest cold storage infrastructure for the country’s agriculture, fishery, and livestock sectors. The need and the situation worsened by the Coronavirus disease 2019 (COVID-19) pandemic and the insecurity of the food supply and its over-reliance on imports and exports have been brought to the forefront. A structure's thermal envelope consists of the exterior elements and systems that shield the interior of the facility from the outdoor environment. It shields the structure from moisture, helps withstand mechanical loads, and keeps the inside safe from dangers or outside pressure. Essential elements of a thermal envelope are the foundation, concrete slab, wall and roofing assemblies, doors, and other components, such as vents and insulation. The structural