Chapter 5 Test Review(concrete)
4 concrete characteristics that can be produced with the reduced water content and water-cement ratio(2)
(4 concrete characteristics that can be produced with the reduced water content and water-cement ratio) Increased early strength gain
4 concrete characteristics that can be produced with the reduced water content and water-cement ratio(4)
(4 concrete characteristics that can be produced with the reduced water content and water-cement ratio) Other beneficial properties associated with low water-cement ratio concrete
4 concrete characteristics that can be produced with the reduced water content and water-cement ratio(1)
(4 concrete characteristics that can be produced with the reduced water content and water-cement ratio) Ultimate compressive strengths in excess of 70 MPa
4 concrete characteristics that can be produced with the reduced water content and water-cement ratio(3)
(4 concrete characteristics that can be produced with the reduced water content and water-cement ratio)Reduced chloride-ion penetration
4 major reasons for using chemical admixtures (4)
(4 major reasons for using chemical admixture)Economy
4 major reasons for using chemical admixtures(2)
(4 major reasons for using chemical admixture)Maintain the quality of concrete during the stages of mixing, transporting, placing, finishing, and curing
4 major reasons for using chemical admixtures (1)
(4 major reasons for using chemical admixture)To achieve certain properties in concrete more effectively than by other means
4 major reasons for using chemical admixtures (3)
(4 major reasons for using chemical admixture)To overcome certain emergencies during concrete operations
List 4 methods that can be applicable to solve incompatibility issue between cement-admixture or admixtures. (2)
(4 methods that can be applicable to solve incompatibility issue between cement-admixture or admixtures.) Changing the sequence of addition to the mixture
List 4 methods that can be applicable to solve incompatibility issue between cement-admixture or admixtures. (3)
(4 methods that can be applicable to solve incompatibility issue between cement-admixture or admixtures.) Modifying composition of the cement
List 4 methods that can be applicable to solve incompatibility issue between cement-admixture or admixtures. (4)
(4 methods that can be applicable to solve incompatibility issue between cement-admixture or admixtures.) Modifying the content of the admixture
Difference between a water reducer and plasticizer?(water reducer)
(Difference between a water reducer and plasticizer?)Water content is reduced while maintaining the slump which in return reduces water-cement ratio of the concrete and increases strength and durability
Difference between water reducer and plasticizer? (plasticizer)
(Difference between a water reducer and plasticizer?)Workability is increased while water content is kept constant?
List 4 methods that can be applicable to solve incompatibility issue between cement-admixture or admixtures. (1)
(List 4 methods that can be applicable to solve incompatibility issue between cement-admixture or admixtures. ) Changing the admixture dosage rate
Typical percentage of high range water reducer
(Typical % water reducer)12%-40%
Typical percentage of normal water reducer
(Typical % water reducer)5%-10%
Typical percentage of midrange water reducer
(Typical % water reducer)6%-12%
Typical values of slump when using normal water reducer
(Typical values of slump)100m or 125mm(4 or 5 inches)
List 4 methods that can accelerate the stringent development of concrete besides the use of set accelerating admixtures. (4)
(methods that can accelerate the stringent development of concrete besides set accelerating mixtures) Curing at high temperature
List 4 methods that can accelerate the stringent development of concrete besides the use of set accelerating admixtures. (2)
(methods that can accelerate the stringent development of concrete besides set accelerating mixtures) Lowering the water-cement ratio by adding 60 kg/m3 to 120 kg/m3 or additional cement to the concrete
List 4 methods that can accelerate the stringent development of concrete besides the use of set accelerating admixtures(1).
(methods that can accelerate the stringent development of concrete besides set accelerating mixtures) Using Type III or Type HE high-early-strength content
List 4 methods that can accelerate the stringent development of concrete besides the use of set accelerating admixtures.(3)
(methods that can accelerate the stringent development of concrete besides set accelerating mixtures) Using water reducer
Typical values of slump when using mid-range water reducer
(typical values of slump)125mm to 200mm(5 in. to 8 inch)
Typical values of slump when using high range water reducer
(typical values of slump)Greater than 150mm (6 in.)
6 applications where flowing concrete is used
- Thin section placements -Areas of closely spaced and congested reinforced steel -tremie pipe -pumped concrete to reduce pump pressure, thereby increasing lift and distance capacity -areas where conventional consolidation methods are impractical or can not be used -reducing handling cost
How much strength reduction generally occurs with increase in air content?
1% increase in strength reduction is accompanied by 5-6% reduction in strength
Match admixture & desired effect(anti-washout admixtures)
Cohesive concrete for underwater placement
2 part chemical systems of hydration controlling admixture
A stabilizier or retarder that essentially stops hydration of cementing materials, and an activator that reestablishes normal hydration and setting once added to the stabilzied concrete
Two primary mechanisms that water enter concrete through?(2)
Direct ingress of water under pressure
Match admixture & desired effect(PRAN)
Water-repellent surface, reduced water absorption
Common purpose of PRAH
Waterproofs, materials that act to block pores and capillaries in concrete
Major benefit of using air-entraining admixtures in concrete?
dramatic improvement of the durability of concrete exposed to cycles of freezing and thawing and deicer chemicals
Common purpose of PRAN
non-hydrostatic, "damp-proofers", give concrete a water repellent property and provide reduced absoprtion
Type E chemical admixture per ASTM C494
provides water reduction and accelerated setting
Why is set accelerating admixture used?
used with low-to-normal slump and water-cement ratio to make high-slump flowing concrete)
Type D chemical admixture per ASTM C494
usually retards the setting time of concrete from one to four hours
Match admixture & desired effect(Air-entraining mixtures)
Improve durability in freeze-thaw, deicer, sulfate, and alkali-reactive environments and improve workability
Match admixture & desired effect(Super plasticizers)
Incrase flowability of concrete and reduce water-cement ratio
Detrimental effect of using air-entraining admixtures in concrete?
Increase in air content results in a decrease in the strength of concrete
When the same chemicals used for high-range water reducers are used to make flowing concrete, how are they called?
Plasticizers or superplasticizers meeting ASTM C1017
Match admixture & desired effect(PRAH)
Reduced permeability, increased resistance to water penetration under pressure
2 major forces that water reducers and plasticizers function as cement dispersants?
Result in equal or reduced compressive strength, can increase slump loss by a factor of 2 or more
Match admixture & desired effect(dampproofing admixtures)
Retard moisture penetration into dry concrete
When air content is maintained constant, how does strength vary with water-cement ratio?
Strength varies inversely with water-cement ratio.
Match admixture & desired effect(hydration control admixtures)
Suspend and reactivate cement hydration with stabilizer and activator
Most common material used as set accelerating mixture, and its maximum dosage?
Calcium chloride (CaCl2), Limited to 2% dosage or less for non-reinforced concrete
Two primary mechanisms that water enter concrete through?(1)
Capillary absorption under non-hydrostatic conditions
Match admixture & desired effect(Gas formers)
Cause expansion before settings
What can be done when entrained air is excessive?
Use Defoaming agent(tributyl phosphate, dibutyl phthalate, octyl alcohol, water-insoluble esters of carbonic acid and boric acid, and silicon.)
