Concrete and paving glossary - R
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Radius (steel) forms
Metal forms used forming radius shapes such as islands, serpentine
sidewalks, curved curbs, parking lot turnouts, and similar applications.
See flexible forms.
Reactive aggregate
Aggregate containing substances capable of reacting chemically with
the products of solution or hydration of the Portland cement in concrete
or mortar, under ordinary conditions of exposure, resulting in harmful
expansion, cracking, or staining.
Ready-mixed concrete
Concrete that is batched or mixed at a central plant before it is delivered
to a construction site and delivered ready for placement. It is also
known as transit-mixed concrete since it is often transported in an
agitator truck. See agitator
truck.
Rebar
The reinforcing bar-ribbed steel bars installed in foundation concrete
walls, footers, and poured in place concrete structures designed to
strengthen concrete. Rebar comes in various thickness' and strength
grade. The term rebar is short for reinforcing bar.
Refractory concrete
Concrete having refractory properties, suitable for use at high temperatures.
Calcium-aluminate cement and refractory aggregates are normally used
for the manufacture of this product.
Rehab forms
Light-weight extend angle-iron-shaped metal forms, often 10' long with
a 2' top rail and no bottom rail, used to replace sections of sidewalk
without extensive excavation of surrounding soil. Rehab forms slip into
place and are anchored into place with stakes after removal of the damaged
concrete.
Reinforced concrete
Concrete reinforced by the addition of steel bars making it more able
to tolerate tension and stress. See pre-stressed
concrete.
Release agent
Material used to prevent bonding of concrete to a surface, such as
to forms. See bond breaker,
form release agent.
Retempering
The addition of water and remixing of concrete which has started to
stiffen. This is usually not allowed as it may affect the ultimate strength.
Reversible forms
A formed metal channel that is a combination of two sizes of straight
forms. A 90° angle is formed which each leg having a different height.
This type of form is used when a concrete contractor needs to pour two
slabs of different heights. One side of the form might have a height
of 10" and the other side might have a height of 14". This variation
allows the one set of forms to be used to pour two different slabs.
See straight forms.
Revibration
Delayed vibration of concrete that has already been placed and consolidated.
This is most effective when done at the latest time a running vibrator
will sink of its own weight into the concrete and make it plastic and
workable again.
Road base
An aggregate mixture of sand and stone. See aggregate.
Road forms
Heavy duty 3/16" or 1/4" metal paving forms capable of supporting large
screed machines. The screed machines ride on the top rails of the paving
forms to level the concrete.
Rock pocket
Area or portion of hardened concrete which is deficient in mortar and
consisting primarily of coarse aggregate and open voids; caused by insufficient
consolidation or separation during placement, or both; by leakage from
form. See aggregate.
Rod (tamping)
A round, straight steel rod, 5/8"
in diameter and approximately 24" in length, having the tamping end
rounded into a hemispherical tip, with a tip diameter of 5/8".
Rodding
Compaction of concrete or the like by means of a tamping rod. See compaction.
Roll
Producing a concrete curb by hand shaping or hand rolling the curb
without the use of face forms. See face
forms.
Rotary float (power float)
Motor-driven revolving blades that smooth, flatten, and compact the
surface of concrete slabs or floor toppings. See screed,
float, floating,
trowel, and darby.
Runway
Decking over an area of concrete placement, usually of movable panels
and supports, on which buggies of concrete travel to points of placement.
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