üConcrete is made by combining four materials into a mixture of basically two parts: aggregate and Portland cement paste.
üThe paste, composed of Portland cement and water, binds the fine aggregate (sand) and coarse aggregate (gravel or crushed stone) into a rocklike mass when the paste hardens.
üConcrete hardening (setting) results from a chemical reaction (hydration) between Portland cement and water. The Portland cement and fine coarse aggregates used should conform to the requirements of the standards of the American Society for Testing and Materials (ASTM)
üConcrete is often reinforced with steel mesh or rods to increase its tensile strength.
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