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. Unreinforced, reinforced, or prestressed.Grouted, partially grouted or surface bonded.The provisions of this TEK apply to both specialty units manufactured specifically for dry-stack construction and conventional concrete masonry units with the following system types: This TEK describes the construction and engineering design of such mortarless wall systems. 16) With the use of specially fabricated concrete masonry units known as “dry-stack units,” construction of these mortarless systems is simple, easy and cost effective. The use of standard CMU units laid dry and subsequently surface bonded with fiber reinforced surfaced bonding cement has been well documented in the past. Construction of masonry wall systems is possible without the use of mortar.

Laying concrete blocks without mortar