GAF WeatherSide Purity Wavy 12 in. x 24 in. Fiber-Cement Siding Shingle (18-Bundle)

Twelve or 12 may refer to:

• 12 (number)
• December, the twelfth and final month of the year
• Dozen, a group of twelve.

Eighteen or 18 may refer to:

• 18 (number)
• One of the years 18 BC, AD 18, 1918, 2018

Bundle or Bundling may refer to:

• Bundling (packaging), the process of using straps to bundle up items

A cement is a binder, a chemical substance used for construction that sets, hardens, and adheres to other materials to bind them together. Cement is seldom used on its own, but rather to bind sand and gravel (aggregate) together. Cement mixed with fine aggregate produces mortar for masonry, or with sand and gravel, produces concrete. Concrete is the most widely used material in existence and is behind only water as the planet's most-consumed resource.

Cements used in construction are usually inorganic, often lime- or calcium silicate-based, and are either hydraulic or less commonly non-hydraulic, depending on the ability of the cement to set in the presence of water (see hydraulic and non-hydraulic lime plaster).

Hydraulic cements (e.g., Portland cement) set and become adhesive through a chemical reaction between the dry ingredients and water. The chemical reaction results in mineral hydrates that are not very water-soluble. This allows setting in wet conditions or under water and further protects the hardened material from chemical attack. The chemical process for hydraulic cement was found by ancient Romans who used volcanic ash (pozzolana) with added lime (calcium oxide).

Non-hydraulic cement (less common) does not set in wet conditions or under water. Rather, it sets as it dries and reacts with carbon dioxide in the air. It is resistant to attack by chemicals after setting.

The word "cement" can be traced back to the Ancient Roman term opus caementicium, used to describe masonry resembling modern concrete that was made from crushed rock with burnt lime as binder. The volcanic ash and pulverized brick supplements that were added to the burnt lime, to obtain a hydraulic binder, were later referred to as cementum, cimentum, cäment, and cement. In modern times, organic polymers are sometimes used as cements in concrete.

World production of cement is about 4.4 billion tonnes per year (2021, estimation), of which about half is made in China, followed by India and Vietnam.

The cement production process is responsible for nearly 8% (2018) of global CO₂ emissions, which includes heating raw materials in a cement kiln by fuel combustion and release of CO₂ stored in the calcium carbonate (calcination process). Its hydrated products, such as concrete, gradually reabsorb atmospheric CO₂ (carbonation process), compensating for approximately 30% of the initial CO₂ emissions.

Fiber (also spelled fibre in British English; from Latin: fibra) is a natural or artificial substance that is significantly longer than it is wide. Fibers are often used in the manufacture of other materials. The strongest engineering materials often incorporate fibers, for example carbon fiber and ultra-high-molecular-weight polyethylene.

Synthetic fibers can often be produced very cheaply and in large amounts compared to natural fibers, but for clothing natural fibers have some benefits, such as comfort, over their synthetic counterparts.

Siding may refer to:

• Siding (construction), the outer covering or cladding of a house
• Siding (rail), a track section

Wavy may refer to:

• "Wavy" (Ty Dolla Sign song), 2016
• "Wavy" (Muroki song), 2021
• WAVY-TV, a TV station located in Portsmouth, Virginia, United States
• Wavy Gravy (born 1936), an American entertainer and activist
• Waviness, the measurement of the more widely spaced component of surface texture
• Wavy the Creator, recording artist
• Deschampsia flexuosa, commonly known as wavy hair-grass

X, or x, is the twenty-fourth letter of the Latin alphabet, used in the modern English alphabet, the alphabets of other western European languages and others worldwide. Its name in English is ex (pronounced ), plural exes.