Cement is a fine powder that, mixed with water, sand, and gravel (aggregate), hardens into concrete, a material strong under compression but weak under tension, which is why steel reinforcement bars (rebar) are embedded inside concrete columns, beams, and slabs to give the structure tensile strength as well. Sandcrete blocks, made from cement, sand, and water cast into molds, are the dominant walling material in much of West African construction because they are relatively low-cost and widely available compared to fired clay bricks. Timber is valued for being lightweight, workable with simple tools, and renewable, but is vulnerable to termites, moisture, and fire without treatment, while steel offers high strength and consistency but costs more and requires protection against corrosion in humid climates. Choosing the right material for a given job depends on balancing cost, availability, required strength, and the local climate.