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On the following page you will find information pertaining to the installation and maintenance of Aerated Concrete Masonry Unit (AMCU) wall systems. Click the "Turnover Documentation Checklist" link to find all information and documentation associated with AMCUs that should be provided to an owner after construction. The "Process Map" section includes a visual aid intended to clarify the actual construction process when using ACMUs, and when analyzed in combination with the "Resource Allocation" section, which lists the different crews and equipment needed during construction, one can fully understand what is required to build a ACMU wall system. The "Process-Based FMEA" section identifies potential conflicts that could arise from the construction of an ACMU wall, and the associated causes and effects of these problems. Finally, the "Troubleshooting Guide" includes the actions that an owner should take if a defect is detected in the wall.
To achieve functional equivalence for our system comparisons the only components we need to analyze are the actual ACMUs and the mortar used to connect them. The installation of an ACMU wall only requires a few simple tools, most of which are very similar to the tools used in traditional CMU construction. The following is a list of these tools:
Similar to most other wall systems the only components that must be in place prior to ACMU construction are the concrete footings and slabs that the wall will be erected on top of. To ensure that the wall is fully connected to the substructure it is important to form rebar or dowels into the footing or slab so that when the wall is being constructed it can be built over top of these components. After the ACMU walls have been built all other construction can begin, including the installation of the roof and cladding components.
Prior to wall construction some companies-like Safecrete-recommend the use of a thick gauge plastic or felt material to serve as a bond break between the wall and the floor. Regardless of whether a bond breaker is used or not the first step of ACMU construction process is to place a bed of leveling mortar (type S or M) beneath the ACMUs that will form the corners of the wall. Thin bed mortar is applied to the head joints of these corner blocks to ensure that each block adheres to one another. It is of highest importance to lay corner blocks correctly and to make sure that theses blocks are level; this ensures that the rest of the wall construction will be laid out in the correct location and the overall process will continue with very little problem. After the corners have been laid a horizontal string line should be strung across from corner to corner, and the remainder of the base course can now be filled in. For every other course thin bed mortar should be used and each block should be placed in a bed of mortar similar to the one pictured below. The consistency of the mortar should be so that it easily flows through the teeth of a notched trowel leaving the shape of the teeth in the mortar bed. It may be necessary to rasp(sand) the block and brush away any irregularities to ensure a level and clean surface to apply mortar to. When placing each block move it as close to the head joint as possible before lowering it onto the bed joint, because if too much movement occurs along the bed joint full-adhesion will not occur.
When laying the block follow a running bond pattern and keep in mind that some companies, such as E-Crete, recommend that the overlap should be either 4" or 40% of the block's height (whichever is greater). Also, when using a "U" lintel it is important to allow a 24" minimum bearing dimension on each side of the opening, to ensure that the possibility of structural failure is minimized. When cutting channels with a router or circular saw it is important to make sure that the location of these channels does not affect the structural integrity of the wall. Rules of thumb for channel location can be found beneath the process-based FMEA further down the page.
The following is a process-based failure mode and effects analysis (PFMEA) associated with the ACMU wall system. As you can see most failures when installing an ACMU wall originate from either human error or poor design, both of which can be easily avoided through education provided by individual manufacturers or organizations like the Aerated Concrete Corp. of America (http://www.accoaac.com/ACCO_frames.html). The quality of each ACMU wall is a function of the quality of slab or foundation it is built atop, therefore if the substructure is of poor quality and unlevel, similar results can be expected from the ACMU wall. To ensure that a level and structurally-sound wall is built it is especially important to ensure that each AMCU is laid both level and plumb. To ensure that each block is level the installer needs only to us an ordinary mason's level and horizontal string line. In the case that the block is not level there are two options: either tap the block into place using a rubber mallet, or sand the block down using a rasp.
It is also equally important to ensure that the flexible flashing is installed correctly to keep water penetration at a minimum; to be completely sure that flashing has been installed correctly, follow the manufacturer's instructions exactly. If "U" lintels are being used it is of extreme importance to make sure that an adequate amount of reinforcement is used, and is installed correctly. Other safety checkpoints provided by E-Crete are displayed after the PFMEA.
Just like with most concrete masonry units, the ACMU has the same failure modes when it comes to human performance. In the likeness of CMU and according to the FMEA analysis of the human performance parameters, a trouble-shooting checklist for two major failure modes is compiled below.
Uniformity trouble-shooting
Is the product from a single source?
Is transportation of the product an issue? How will it be transported? By unit load?
Is it sound? Void of cracks,chips, and/of defects.
Is the product stored properly? Off-ground, covered, dry location.
Is the product tested for strength and absorption uniformity?
Installation trouble-shooting
Is the layout correctly outlined?
Do the ACMU blocks match? Color, size, shape, bonding, coursing.
Are the mortar installation specifications being followed?
Have openings been made for doorways and windows?
Have proper planning for HVAC, conduits, pipings been calculated?
Missing bullets on top index page. Top page not fixed. For Tech Performance repairs, FMEA page still lacks a narrative at top.
For Human Performance, the top of this page is excellent! Only one example of turnover documentation is provided. No description for other items in bullets. Excellent YouTube video, but no link to source in the text, although you do include it at the bottom of the page – please provide link! Otherwise, best of breed. No narrative provided for resource allocation tables. Always provide a short introductory narrative to explain what the section contains. Rows in table do not match process map tasks as required. Same goes for the FMEA – the rows don’t match the process map, although the narrative for this section is outstanding. Troubleshooting guide is correct although not detailed. Coordination among tasks was essential to do well on this assignment - need to match tasks for the middle three deliverables! Also, please number references and cite in text.
