What might happen on a hot day if expansion joints were not used?

On a hot day, materials like concrete and metal expand due to increased temperatures. Without expansion joints, this expansion can lead to significant stress and pressure within structures, causing cracks, buckling, or even structural failure. Additionally, the lack of expansion joints can hinder the movement of materials, resulting in misalignment and compromised integrity over time. Overall, the absence of these joints can lead to costly repairs and safety hazards.