What aspect is crucial in determining the fire resistance of a wall built from sand-lightweight concrete?

The thickness of the wall is a crucial factor in determining the fire resistance of a wall constructed from sand-lightweight concrete. Fire resistance is typically measured by the wall's ability to prevent the passage of flames and heat for a certain period. Thicker walls can provide greater mass and insulation against heat, thereby enhancing fire resistance. They can absorb and dissipate heat more effectively than thinner walls, which may allow fire to penetrate more easily.

In the context of wall construction, thicker walls have more material, which means there is a greater distance for heat to travel before it reaches the interior of the wall. This helps in delaying the degradation of the structural components and overall stability during a fire exposure scenario.

Other aspects, while they may contribute to the overall performance and structural integrity of the wall, do not have as direct an impact on fire resistance as wall thickness does. The type of concrete mix, reinforcement method, and surface finish can influence various other properties such as strength, durability, and aesthetics, but they are secondary when it comes to resisting the effects of fire over time.