An admixture that will shorten in setting time of concrete.
A material or chemical other than water, cement and aggregate used to modify ready mix concrete's properties, such as its setting time and slump.
Material such as sand, gravel or crushed stone, which when mixed in conjunction with water and cement becomes concrete.
An admixture that through agitation in production of ready mix concrete causes the development of microscopic bubbles that increase its workability and aid in the freeze/thaw cycle.
Production of a quantity of ready mix concrete base on volume, i.e. cubic yards or cubic meters
The measured amount of sand, stone, cement and water the comprise a batch or load of concrete.
Usually shaped like a cylinder as part of a footing or foundation.
A 32% solution or granular/flake product, when added to concrete acts as a set accelerator.
Also known as Portland Cement, s a hydraulic product, which means it sets and hardens when it chemically interacts with water, and can also do this underwater.
Any ground granular product having cementing properties.
Graded granular material with a nominal maximum size ranging from 1" down to 3/8".
A mixture of sand, cement, stone and water.
A graded granular material entirely passive through a 3/8" sieve.
Is a cementitious material made from an inorganic residue from coal combustion in power plants that is used as a partial replacement for cement in a mix design.
High Range Water Reducer (Superplasticizer):
An admixture that can produce a high slump concrete or produce considerable reduction of water with a minimal effect to set time.
A low density man made aggregate which includes clay and shale that is used in lightweight concrete.
An admixture that will extend the setting time of concrete.
Also known as micro silica is a metallic based substitute for Portland Cement which increases the strength and density of concrete.
Slag (Ground Granulated Blast Furnace Slag):
Is a cementitious iron and silicate base product formed from turning iron ore into iron that can be used to partially replace cement in a mix.
A membrane such as 4 mill plastic placed on grade that when fresh concrete is placed on top, minimizes the transmission of water vapor into and through hardened concrete from the subgrade.
Often used in basements.
Water Reducing Admixtures:
A admixture that allows a decrease in water without changing the slump of fresh concrete, or, allows an increase in slump without an increase in water.
Water Cement Ratio:
The weight of total water relative to the weight of total cement used per cubic yard.
TYPES OF READY MIX CONCRETE:
A ready mix material that usually does not contain coarse aggregate and is used the fill abandon fuel and oil tanks, fill around buried utilities, compacted and used as permanent or temporary subgrade and back fill.
A ready mix concrete which uses a man made coarse and in certain cases fine aggregate which results in concrete the weight approximately 25% lighter than normal concrete mixes.
Normal concrete weighs approximately 145 lbs/cu.ft. compared to 110 lbs/cu.ft.
A sound proofing and insulating lightweight concrete/
High Early Strength Concrete:
A concrete mix that will achieve a certain compressive strength in a minimal amount of time, usually less than 28 days. i.e. a contractor needs to achieve 4000 psi in 2 days on a slab.
Roller Compacted Concrete:
Flowable Fill that is used as a permanent of temporary subgrade.
A mortar cement that is pneumatically projected onto a surface. Commonly used for swimming pools and also is called gunite.
Fiber Reinforced Concrete:
A ready mix concrete that contains Fibermesh , which improve shrinkage crack resistance, improved flexural and compressive strength and improves impact resistance.
CONCRETE SLAB DEFECTS:
The are bumps that appear at a time when bubbles of entrapped air or water rise through the unhardened concrete get trapped under an already sealed, airtight surface. Blisters are usually caused by a) insufficient or over vibrating of concrete b) finishing concrete when it is still spongy c) excessive amount of entrapped air held within the concrete by excessive dosages of air entrainment.
cracks that occur before the concrete hardens are usually the result of shrinkage of the concrete's surface caused by a rapid loss of water while the concrete is still unhardened.
that occur after the concrete is hardened are the result of a) drying shrinking: large increases in the sand content and a large reduction in the size of the coarse aggregate increase shrinkage because total water is increased and because smaller size aggregates provide less internal resistance shrinkage. b) thermal contraction: concrete placed during hot midday temperatures will contract as it cool during the night. c) subgrade settlement: insufficiently compacted subgrades and soils exposed to frost and a freeze/thaw cycle can produce cracks in expansion and contraction.
a network of fine pattern cracks that do not penetrate below the surface, are caused by minor surface shrinkage. Crazing is not structurally serious and does not ordinarily indicate that the will be future deterioration. Low humidity, high temperatures, hot sun and drying winds can cause rapid surface drying that encourages crazing.
is the distortion or rising up of a slabs corners and edges do to a difference in moisture content or temperature between the top and bottom of the slab.
are similar to blisters in that delaminated areas result from the bleed water and bleed air being trapped below a prematurely finished surface. Delamination is very difficult to detect during finishing and become apparent after the concrete surface has dried and the delaminated area is crushed under traffic. The primary cause is finishing the surface for the bleeding has occurred.
factors found to influence discoloration are calcium chloride admixtures, cement alkalies, hard troweled surfaces, inadequate or inappropriate curing, variations of the water cement ratio at the surface (i.e. spraying water on the surface during finishing), changes in the concrete mix and covering the surface of the concrete prematurely. Discoloration from these situations appear very soon after the concrete is placed.
is the development of a fine powdery material that easily rubs off the surface of the hardened concrete. Dusting is the result of a thin, weak layer called laitance, composed of water cement and fine particles. Dusting s caused by a) floating and troweling concrete while the bleed water s still on the surface b) water applied during finishing c) exposure to rainfall during finishing d) spreading dry cement over the surface to accelerate finishing e) low cement content in the concrete mix f) too wet of a mix g) lack of proper curing h) freezing of the surface before the concrete is hardened i) dirty aggregate.
is a conical fragment that breaks out of the surface of the concrete leaving a hole. This is usually caused by a piece of porous rock which absorbs moisture or freezing occurs in moist conditions, as is swelling creates internal pressure sufficient enough to rupture the surface of the concrete. Most popouts appear within the first year of the concrete being placed and are considered cosmetic and usually do not effect the strength or service life of the concrete.
is the loss of surface mortar exposed to the freeze/thaw cycle. The aggregate is usually clearly exposed and often stands out from the concrete. Scaling is primarily a physical action caused by pressure from water freezing within the concrete.
is a deeper surface defect than scaling, often appearing as circular or oval depressions on the surface or as elongated cavities along joints. Spalls are caused by pressure or expansion within the concrete, bond failure when new and old concrete meet, impact load, fire, or weathering. Improperly
installed joints or corroded reinforcing wire can cause spalling.