![]() Grout cores can also be reinforced to increase flexural strength. Grout cores also interlace units placed in running bond and thus provide resistance to in-plane shear forces beyond that provided by friction developed along horizontal joints. Flexural tensile stresses due to out-of-plane bending are resisted by the grout cores. With each construction type, walls are built by first stacking concrete masonry units.įor unreinforced construction as shown in Figure 2a, grouting provides flexural and shear strength to a wall system. More information on design and construction of dry-stack masonry can be found in Reference 5.ĭry-stack concrete masonry units can be used to construct walls that are grouted or partially grouted unreinforced, reinforced or prestressed or surface bonded. Dry-stack masonry construction can prove to be a cost-effective solution for residential and low-rise commercial applications because of it’s speed and ease of construction, strength and stability even in zones of moderate and high seismicity. Typical applications for mortarless concrete masonry include basement walls, foundation walls, retaining walls, exterior above-grade walls, internal bearing walls and partitions. Strength of grouted dry-stack walls may also be enhanced by traditional reinforcement, prestressing, post-tensioning or with external fiber-reinforced surface coatings (surface bonding) as described in the next section. Grouting is necessary to develop flexural tensile stress normal to the bed joints, which is resisted through unit-mortar bond for traditional masonry construction. Vertical alignment of webs ensures a continuous grout column even when the adjacent cell is left ungrouted. Wall strength and stability are greatly enhanced with grouting which provides the necessary integrity to resist forces applied parallel, and transverse to, the wall plane. ![]() Floor and roof systems can be supported by mortarless walls with a bond beam at the top of the wall which expedites the construction process. The interlocking features of dry-stack units improve alignment and leveling, reduce the need for skilled labor and reduce construction time. The first of these two interlocking mechanisms also ensures vertical alignment of blocks. Interlocking units placed in running bond resist flexural and shear stresses resulting from out-of-plane loads as a result of the keying action: (a) at the top of a web with the recess in the web of the unit above, (b) at two levels of bearing surface along each face shell at the bed joint, and (c) between adjacent blocks along the head joint. (1.58 mm.) which precludes the need for mortaring, grinding of face shell surfaces or shimming to even out courses during construction. Physical tolerances of dry-stack concrete units are limited to ± 1/ 16 in. Other units are fabricated with a combination of keys, tabs or slots along both horizontal and vertical faces as shown in Figure 1 so that they may interlock easily when placed. The latest and most sophisticated designs incorporate face shell alignment features that make units easier and faster to stack plumb and level. Specially designed units for dry-stack construction are available in many different conÞ gurations as shown in Figure 1. ![]() The provisions of this TEK do not apply to such systems due to a difference in design section properties (ref 8). Note that dry-stacked prestressed systems are available that do not contain grout or surface bonding.
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