In concrete, which component acts as the primary binder that glues the aggregates when it hydrates?

In concrete, which component acts as the primary binder that glues the aggregates when it hydrates?

• A. Portland cement
• B. Water
• C. Sand
• D. Gravel

Answer: (A)

The binding action in concrete comes from the cement paste formed when cement hydrates. Portland cement is the common binder used; when water is added, the cement chemically reacts to form hydration products, mainly calcium silicate hydrate (C-S-H) and calcium hydroxide. This glue-like cement paste coats and glues the aggregates—sand and gravel—together, giving the concrete its strength. Water enables the reaction but isn’t the binder itself, and the aggregates provide bulk and structure rather than bind. In specialty mixes other binders can be used, but in standard concrete the primary binder is Portland cement.

The binding action in concrete comes from the cement paste formed when cement hydrates. Portland cement is the common binder used; when water is added, the cement chemically reacts to form hydration products, mainly calcium silicate hydrate (C-S-H) and calcium hydroxide. This glue-like cement paste coats and glues the aggregates—sand and gravel—together, giving the concrete its strength. Water enables the reaction but isn’t the binder itself, and the aggregates provide bulk and structure rather than bind. In specialty mixes other binders can be used, but in standard concrete the primary binder is Portland cement.