Concave 
Hollow and curved such as the inside of a hollow sphere. 

Concave Joint 
Joint which is made in water-resistant mortar. 

Concealed Hinges 
Invisible hinges when the door is not open. 

Concealed Nail 
Installation of roll roofing method of roofing installation where each course of roll roofing covers the nails in the prior course by overlapping it. Roofing cement holds down the edges of the courses, bonding them to each other. 

Concealed Wiring 
Electric wiring that is inside the walls of a building. 

Concentric 
Having a center in common. A circle within a circle. 

Concentric Zone Theory 
Land development theory that an urban area expands, in rings. The inner ring being the business district; ring 2 has manufacturing, warehousing and some commercial activity; ring 3 is low social economic status housing; ring 4 has middle-income housing; ring 5 has new high social economic status housing. 

Conceptual Design 
Detailed design showing an object in question. 

Concession 
Benefits granted by a seller/lessor to induce a sale/lease. Alternately, right granted by a governmental body, to use property for a particular type of business in a specific area. 

Conclusive Presumption
When evidence cannot be supported to disclaim an obvious claim such as water being wet. 

Concrete 
A mixture of cement, sand and aggregate which is mixed with the proper proportion of water allowing it to solidify into a structural material with good compressive strength. 

Concrete, Aerated 
Concrete that has been altered chemically, with an additive, to disperse air bubbles through the mix. A yard of air-entrained concrete may contain over three trillion bubbles. This mix is easier to work than standard concrete and stands up well in cold weather, resisting salts better than other concrete. While it is good for pouring in cold weather because the bubbles allow the concrete to expand and contract more readily, it is not as strong as regular concrete. Also referred to as Air-entrained Concrete. 

Concrete Block 
Hollow building blocks, which are used in the construction of foundations and outer walls to provide strength and durability. Dimensions are 8"x 8"x 16". 

Concrete Block Segmental Retaining Wall Systems 
Retaining wall, mortarless concrete block made to interlock and can be fastened with fiberglass pins. A wall can be up to 5 ½ feet and withstand being toppled by a combination of the weight of the block and the incline on which it is set. Higher walls need additional support or certain hardware to hold them steady. Heavier than regular block, they weigh about 70 pounds each and also come in varying colors. Walls may be straight or curved. 

Concrete Block Wall 
Wall of concrete blocks cemented with mortar. 

Concrete Brick 
Portland cement and aggregates like sand or cinders mixed into brick-sized, solid masonry blocks. 

Concrete Brick, Solid 
Block made of portland cement, water and various aggregates, they are referred to by the type of aggregate; cinder, concrete, etc. 

Concrete Finishing 
To achieve a final cured surface that is smooth and hard, the concrete must be subjected to screeding, which is the use of a rigid piece of metal or wood to level the concrete and remove excess material; floating, which is the smoothing, with a flat plate, of the new concrete surface; and troweling, which is the use of a hand tool with a flat rectangular metal surface which smoothes and finishes the concrete. 

Concrete Forms 
Molds that are structurally sound enough to hold and shape poured concrete while it sets. 

Concrete, Insulating 
To provide an R-factor, which is a measurement of resistance to temperature transmission, of about 1.1.per inch of thickness concrete must have an expanded mica aggregate of 6 to 1, aggregate to cement. 

Concrete Machine 
Machine used to pour, spread and smooth concrete. 

Concrete Masonry 
Concrete masonry units built into masonry structures. 

Concrete Masonry Unit (CMU) 
Differently shaped and sized concrete bricks. 

Concrete Mix 
Amounts of cement, aggregate and water in certain proportions for the amount of concrete necessary to do a job. 

Concrete Mixer 
Motorized drum, which mixes the components of concrete by use of internal paddles. Also called a Cement Mixer. 

Concrete Nail 
Nail used with set concrete, having a thick-shanked nail with a flat head. 

Concrete Paving 
Concrete used as paving for a road surface. 

Concrete Pipe 
Steel reinforced pipe made of concrete. 

Concrete, Pre-cast Architectural 
Factory manufactured concrete pieces, which can be used as part of structural framework or as siding for certain types of buildings. There are many different types of pre-cast units available with exterior units adding weather resistance as well as decoration. 

Concrete Pumper 
A concrete pumping unit is usually mounted on a truck and powered by an internal combustion engine, which directs the concrete from the mixer to its use location, by moving it from the mixer to the pump intake hopper. To reach the area of use, hoses are run from the outlet of the pumper to the forms to be filled. Booms are used to direct and support the hoses. 

Concrete, Reinforced 
Concrete with steel rod, bars or mesh added to increase strength and resistance to cracking.

Concrete Saw 
Water-cooled power saw which uses a diamond or carborundum blade to cut hardened concrete. 

Concrete Slab 
Concrete pour that is horizontal and flat. 

Concrete Tamper 
Hand tamper, also referred to as a jitterbug, which consists of a metal grill with long handles. It forces large aggregate beneath the wet concrete surface to leave it smooth and finished. 

Concrete Trowel 
Piece of flat metal with a handle that is used to finish cement work. Also called a cement trowel. 

Concrete Tilt-up 
The forming of concrete wall through the process of pouring concrete into forms on the ground. Once the forms are hardened, the material is raided to a vertical position, forming walls. 

Concrete Vibrator, Electric 
Motorized vibrator, which consolidates and eliminates any of the voids in the forms by inserting a long, flexible wand into fresh concrete. 

Concrete Wall, Poured 
Concrete wall that is poured into forms and set-up in the place where it will remain. 

Concrete Workability 
Determination of how well a concrete mix can be placed or finished by assessing its consistency and character. 

Concurrent Heating 
Application of secondary heat sources to the material that is being utilized in welding or thermal cutting.

Concurrent Ownership 
Ownership in a property by two or more owners, simultaneously.