Masonry Magazine February 1997 Page. 23
ment with the opposite compartment charged with cementitious material. Before delivery, the chambers are filled with the appropriate proportions of sand and cement. At the site, the batching system is activated allowing metering screws to supply an auger-type mixer. To adjust the ratios of the materials (sand, cement and water) a meter can be regulated during the job to achieve the desired plasticity.
Silo and Bulk Bag Systems.
The silo and bulk bag style mortar as specified, to meet either the proportion or property requirements of ASTM C-270. Upon architectural approval, admixtures such as pigments for colored mortar are pre-blended at the factory for complete quality control.
Advantages of Silo Systems:
Consistency and Quality
When proportioning mortar in the field, using portland cement and lime, or blended cements and masons' sand, many variables are SPEC MIX
Increased Efficiency and Productivity on Job Sites
On most masonry job sites, the mortar tenders and lift operator control the pace of the contractors' crew. Without mortar in the tubs or on the boards, it is difficult for a mason to maintain productivity at a pace that generates profit. When breaking bags and shoveling damp sand to make a batch of mortar, it takes a typical mixer operator approximately nine to ten minutes once the first pail of water is added. In comparison, some silo systems have the ability to make mortar at 50% less time while meeting ASTM C-270 mix time requirements. Pyramid Masonry Contractors Inc., of Georgia uses the silo system to maximize the available manpower. "Because time is saved by using the silo, a sawing station is set up next to the mixing area which allows the laborer to make mortar and cut units. Our lift operators can also assume the mixing responsibilities by keeping a batch ready in the mixer at all times. Once the mixer is emptied, the operator will quickly start another batch before delivering the first," says Keith Sommer, Regional Vice President.
delivery method is unique in that the specified material is factory produced by a computer-controlled batching process that fills 3,000 pound bulk bags to load the silo. When the project starts, one or more silos are delivered to the site with a shipment of bags that are loaded into the silo. A gravity controlled slide gate allows the laborer to mix the amount of mortar needed with exact consistency from batch to batch throughout the job. The simplicity of this system enables the mason contractor the flexibility to move their mixing station with the scaffolding and masons as the project progresses.
The silo and bulk bag system was patented in the U.S. by Spec Mix in 1990. Today, this system is distributed and supported by one of the nation's 43 licensed manufacturers through their trained sales teams. Mix designs are custom formulated for portland cement and lime, masonry cement or mortar cement, present that will effect the integrity and performance of the final product. Once the recipe is altered, consistency is lost. The amount of damp, loose sand shoveled into a mixer can vary in every batch based on moisture content and the particular individual (s) mixing that day. As the volume of sand in the mix changes, so will the ratios of the material. These variations effect the performance of the material. Designed to meet applicable ASTM specifications, preblended mixes are pretested for approval to eliminate job site proportioning and inconsistencies. Quality and consistency are the main reasons why Kevin Ryan of Masonry Developers in Michigan uses the bulk bag silo system. "Premixed mortar guarantees me and the owner that the right mix is being used to build the wall. The quality control gained from this type of system assures me, as a contractor, that I am providing a good product for a good price."
Silos that can be moved about the site offer mason contractors more flexibility and control when working in a limited space. If the mixing station must be moved, the silo and mixer can be relocated without