Quality Concrete Flashcards
For concrete to set quickly, Type ___ concrete should be used to produce high early strength
Type III
What is the result of too much water in a concrete mix?
High slump, lower strength
Which is a characteristic of air-entrainment concrete?
increases workability
When can fly ash be used in the calculation of minimum cement content for a concrete mix?
When allowed by the specifier
Which type of foundation would generally be specified when the allowable bearable capacity of the soil is very low to great depths?
mat, raft or floating
The maximum delivery time for ready mix concrete is
1.5 hours
The safety factor for form tiles is
2:1 ratio
What would reduce the lateral pressure on concrete forms?
slower placement
The main purpose for steel reinforcement is to resist what type of force?
Tensile forces
A #5 bar has what characteristics?
.625” diameter, .31 in2, 1.043 lbs/ft
What is the effect of lowering the top bar or raising the lower bar by 1/2” more than specified in a 6” slab?
Reduce carrying load by 20%
What are the most effective types of water stops made of?
PVC polyvinylchloride
Control joint cuts in a slab should be to a depth of ____ the slab thickness
1/4
Within how many hours after placement should concrete joints be sawn?
4 to 12 hours
Which type of joint is used to control cracks where placement of concrete is interrupted?
Construction
In a mat slab, generally, where below the top is the steel located?
2” below the top
Welded wire fabric is located where and for what reason?
upper part to prevent cracks
To facilitate handling and workability, most specifications will allow the job-site addition of water to the concrete mix to an amount that ____
water to cement ratio is not exceeded
To pump through a 5” line, a mix design should consist of a well-graded mix of ____
4” slump with air and fly ash
If lightweight aggregate to be pumped is not presoaked so that it consistently contains 70-80% of total absorption, the aggregate may ____
become more difficult to pump
A vibrator should not remain at one location in the concrete for more than _____ seconds
10-15 seconds
Air entrainment increases the probability of which type of concrete field problems?
Blistering
A non-slip surface on the concrete is obtained by what means?
Broom finish
