Type III Cement (High Early Strength) 1

[CivilStructural07]

Does anyone know any disadvantages of using type III cement (cracking, etc.)? I'm about to be in a time crunch and I don't think I'll be able to wait the 28 days to gain the strength I want.

 

[civilperson]

Cure at elevated temperature for early high strength. Precast factories get 5500 psi in twelve hours every placement with steam cure.

 

[rconner]

I think traditionally there has been some level of increased shrinkage of Type III, and maybe also at least a slight trade-off in ultimate strength level -- like you I will watch for more knowledgeable and complete responses.

 

[Lion06]

Can you just use a typical concrete with a higher f'c?

 

[bpattengale]

Well this is info from PCA Design of and Control of Concrete mixtures.
High-early-sterntg can be obtained by using one or a combination of the following, depending on the age at which specified strength must be achieved and on job conditions:
1. Type III or HE high-early-strength cement
2. High cement content (675 to 1000 lb/yd^3)
3. Low water-cementing materials ration (0.20 to 0.45 by mass)
4. Higher freshly mixed concrete temperature
5. Higher curing temperature
6. Chemical admixtures
7. Silica fume (or other supplementary cementing materials)
8. Steam or autoclave curing
9. Insulation to retain heat of hydration
10. Special rapid hardening cements

I know Type III cement costs more than Type I so you might want to look at some of these other options depending on how much you need to move the schedule up. Also the working time on these early strength mixes can be significantly shorter than regular concrete mixes.

 

[hokie66]

Type III is the same chemically as Type I, but it has been ground finer. So the concrete will harden quicker and strength gain will be faster. Other than workability problems, especially in hot weather, I am not aware of any adverse properties.

 

[projectinspector]

What is causing the time constraint? Depending on the application, you may be able to achieve enough strength for service before the typical f'c, or 28 day strength.

 

[CivilStructural07]

Thanks for all the info guys. And the application is actually a bridge bent that is being constructed to test on our seismic shake table. We just didn't want to wait the 28 days for the bent cap to cure if we don't have to.