There is not a wall system that is more proven than reinforced concrete
block masonry. TXI has built on that reputation.
When the PMWS is chosen for your next project, you design and employ
concrete block installation methods that are familiar with masonry
installation professionals.
Your chosen block supplier will provide concrete masonry units
manufactured from the same molds and equipment that other units are made
from. The difference is the concrete mix design and its ingredients.
I. The first characteristic of the mix design is the requirement to use
structural-grade TXI Expanded Shale and Clay (ES&C) fine aggregate
as 100% of the lightweight aggregate. Our fine aggregate is a
recycled material
that qualifies for LEED Credit 4.1 and 4.2 Recycled Content.
No other types of lightweight aggregate are allowed.
Note: The replacement of TXI lightweight with heavyweight aggregates complying with ASTM C 33 is allowed. The use of some percentage of heavyweight aggregates is typically done by the block manufacturer. Concrete mass increases result in heavier block. Physical properties such as thermal performance and fire ratings are also affected.
II. The second requirement is that concrete masonry units (CMUs) meet
strength requirements that meet or exceed minimum ASTM requirements.
Although block manufacturers comply with ASTM C 90 minimum strengths
utilizing typical mix designs, the guide specification offers high strength options available to the specifier. This is easily achieved by the block producer
due to the special physical characteristics of ES&C as well as the
benefits of internal curing.
III. The third requirement is that block concrete meets the density
(mass) requirements of Lightweight block per the Standard Specification
for Loadbearing Concrete Masonry Units, ASTM C 90. This specifies that
Lightweight concrete dry density must be less than 105 pcf. With TXI
ES&C, dry concrete density of 85 pcf is achievable.
CONCRETE DENSITY: A range of concrete densities can be specified by the
architect or engineer ranging from 85 pcf to less than 105 pounds per
cubic foot dry density and still comply with the standard for
Lightweight block. (105 pcf or more means the unit is not considered
Lightweight by the standard.) Testing reveals that the PyroTherm Masonry
Wall System will provide for structural support using higher strengths
with less weight.
QUALITY ASSURANCE: You should check with the block producer you are
considering for your next project. Ask what concrete density is used in
the block they typically already produce. The block manufacturer usually
will already produce a concrete block meeting the concrete density
requirement of less than 105 pcf. See our handy block weight checker
for field checking by your own project personnel. Ask if they are using
TXI ESC as the only lightweight aggregate in the mix design. This
information should be included in project submittals. If you choose your
supplier from our list of qualified producers – their sales
professionals can provide this information.
If lighter units are needed as compared to typical blocks inventoried by
the block producer, this can be accomplished by discussing your needs
with the block supplier. Usually, the producer can make a special run of
block meeting your requirements if given enough lead time. This will
assure that your blocks are ready for delivery at the time you need
them.
PyroTherm® Masonry Wall System requirements are not difficult to
meet and assures that engineering expectations are achieved. Other components of the PMWS are:
- Grout: Grout can be either normal weight or lightweight grout meeting ASTM 476, as modified and approved by the project engineer for lightweight grout.
- Mortar: As specified by designer. Treat as typical masonry assembly
using Type M, S or N mortar.
-
Strength of Masonry: While unit strength methods for determining
masonry strength are provided for by code, thus eliminating the need for
testing, these tables are conservative in nature – thus value
engineering is not utilized to the extent possible. If higher masonry
strengths than 1500 psi f’m is required for your masonry, we would
suggest testing masonry prisms according to the Standard Test Method for
Compressive Strength of Masonry Prisms, ASTM C 1314 for actual 28 day
strengths using block, mortar, or grout intended for the project.
For more information visit the online NCMA TEK Manual, Tek 18-1A, "Compressive Strength Evaluation of Concrete Masonry".
Request prism submittals well in advance of project
start date. Masonry strengths of up to 2500 psi are available
with mix adjustments and high-strength block manufacturing techniques.
Allow time for prism testing.
R-values, fire ratings, and other information about wall performance are
available here in our Masonry section. Reduce wall thickness
requirements to comply with fire rating requirements based on mix
designs alone!
Achieve the optimum balance of weight, fire rating, strength, and
thermal performance with the PyroTherm Masonry Wall System.
