Density of early 20th century cinder concrete block? 2

[civg]

Is anyone aware of literature that provides the density of concrete block used in early 20th century "slagblok" construction? I can make a reasonable assumption based on current standards but I would like to try and get as accurate as possible for the purpose of determining existing loads.

Thanks.

 

[concretemasonry]

You will not find a definitive source because of the wide range of slag products used. It is similar to the use of cinders to make "cinder block", which also used a waste product that is uncontrolled.

For almost all of the 20th century the concrete masonry specifications (ASTM C90) provided for different types of block based on the density of the concrete in the units (normal weight over 130 pcf, medium weight, lightweight less than 105 pcf and even very lightweight less than 85 pcf). Since block have some standardized minimum dimensions, the weight of the individual units varied.

Most of the use of early concrete masonry was unsophisticated and the selection of units used was based on economics and local availability. The slag block were common in the areas where steel was produced and cinder block were common in areas where coal was burned for heat. - Generally the east and the steel producing areas.

Some slag block were of very high quality because they used the "foamed" slag that was controlled and expanded to provide light weights and good strengths that offered very high insulation values and fire resistance, while other block using the cold slag had densities slightly higher than normal aggregates.

Unfortunately, the ASTM C90 standards are just minimum standards and few "modern" engineers fail to specify or use the products that can be easily supplied.

The "loads", that you need could be the those based on samples of the units currently in place that show the density and percentage of solids. Normally, the density or weight of the masonry units have little bearing on the load bearing capacity of the wall since modern ultra high strength walls can be built using lighter masonry units that have 2 or 3 times the capacity.

Dick

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

 

[SLTA]

From "The Building Estimator's Reference Book", 1st ed 1915:

"Concrete blocks and partition units are manufactured in two weights of concrete, one weighing approximately 145 lbs per cu. ft. (sand, pebbles, crushed stone or slag aggregates) and another of lighter weight concrete weighing about 100 lbs per cu. ft of burned clay or cinder aggregates."

Scan attached of the table - weights per 100sf of wall area.

cheers!