Official source for masonry weights/densities?

[Structuralengineer4]

What is the official source for masonry weights/densities? What I mean by this is there a list that spells out the weights/densities for 8" partially grouted, 10" fully grouted, etc. In the past I have often cited the PCI handbook 6th edition design aid 11.1.1. Is there a more official source than this? I didn't find this information in ACI 530.

 

[msquared48]

Amrhein

Mike McCann
MMC Engineering

 

[flight7]

ASCE 7 commentary Table C3-1.

 

[Structuralengineer4]

Thank you very much! I don't have access to that textbook but the ASCE 7 reference is exactly what I was looking for.

 

[concretemasonry]

Structuralengineer4 -

Generally, for CMUs, according to ASTM C90 for loadbearing concrete masonry units, there are 3 categories based on density - normal weight(over 125 pcf density concrete), medium weight (105 to 125 pcf) and lightweight (under 105 pcf). The choice of densities is usually in the specifications for the project.

The actual weight of the wall will depend on the CMU density AND the shape/configuration and wall thickness for the units used. Most suppliers will have general information on the specific units manufactured locally.

This is the basics for wall weights and densities. If you have a question about the structural strength, the same specification requires a strength of 1900 psi based on the net area of the individual units. Usually, the strengths exceed the minimal strength requirement by 25-35% based on economics of manufacture, but net strengths up to 8000 psi can be made if specified. Engineered masonry may require prism tests (2-block high and mortared) and not the ASTM for the normal block testing.

Dick

Engineer and international traveler interested in construction techniques, problems and proper design.

 

[concretemasonry]

Structuralengineer4 -

An extra note -

For more detailed information on concrete masonry applications, codes, standards and similar items(even for international uses) go to the home site of the NCMA (National Concrete Masonry Association)site. They have over 100 different TEK Notes that are constantly being upgraded. The staff of engineers are active in most code and standards documents (ACI, ASTM, TMS, IBC, state and government standards/codes, etc.) and chair many committees that go through. Jim Amrhein worked with them in past, but Jim's orientation was toward a local geographic region. - In the end, the NCMA has become the pattern for much of the concrete masonry information in North America and in most counties I have been been involved for masonry.

Dick

Engineer and international traveler interested in construction techniques, problems and proper design.

 

[Hokie93]

I investigated this very issue about three years ago and did a comparison of published wall weights for 8" and 10" CMU, both lightweight (105 PCF) and normal weight (135 PCF) for each size. The comparison included grout spacings that varied from 8" to 48". The references included in the comparison were:

1.) ASCE 7-05
2.) ASCE 7-93
3.) Reinforced Masonry Design, third edition, by Schneider and Dickey
4.) Reinforced Masonry Engineering Handbook, 5th edition, by James Amrhein
5.) NCMA Concrete Masonry Design Tables (TR 121)
6.) NCMA TEK Note 14-13B (2008)

The results indicated lots of "scatter" between the published wall weights, particularly for the normal weight walls. In that case, the maximum difference between published values was 15 psf for both the 8" and 10" walls. The published weights for the 10" lightweight walls showed the least scatter.

For what it is worth, the values in the NCMA Concrete Masonry Design Tables (TR 121) are very close to the average of the published values. The bottom line in my opinion is to be cognizant that CMU wall weights can vary significantly depending on the cited source and that depending on the application (gravity or resistance to uplift/overturning, for example), the wall weight from your favorite reference may not be conservative.

 

[concretemasonry]

A real official, reliable source does not exist since most just give some average numbers.

Consider that lightweight block can be made in densities between 85 and 105 pcf. Medium weights run into a range of 105 to about 125 pcf and normal weight between 1030 to 145 pcf. These are generally the ASTM C90 definitions by concrete type.

There is no specific configuration for CMUs according to ASTM C90. Block can have 1,2 or 3 cores and the face shell can vary since ASTM only gives minimums, but producers are generally slightly in excess due to contractors desire for different core shapes, flared webs and face shells to facilitate handling and ease of spreading mortar.

Dick

Engineer and international traveler interested in construction techniques, problems and proper design.