Brick with high absorption, if laid dry, will absorb water from the mortar before bond develops. Absorptive brick must be thoroughly wetted before laying to obtain good masonry. There should be no free water on the brick surface when laid.
Masonry work can be done success fully in cold weather, if the necessary precautions are taken when temperatures fall below 40°F. Masonry should be protected from freezing for at least 48 hours to avoid impairment of both bond and strength. It is also very important to prevent the masonry from drying too rapidly during this early period. The amount of protection needed depends upon the temperature. Be tween 40°F. And 32 °F. All materials should be covered and properly stored to keep them dry.
Mixing water should be heated but not above 160°F. The mortar temperature should be kept above 50°F. Mortar temperature should not become high enough to cause quick stiffening. In cold weather, it is particularly important that concrete
units be stock piled off the ground; and kept dry and covered. Since most sand contains moisture it must be free of ice before using. Heating sand above 50°F. Is seldom necessary and scorching the sand should be avoided.
On dry, windy days, especially when it is hot, and there is direct sunlight, mortar batches tend to dry out more quickly. In such weather, mortar should be kept covered if possible, to protect it from premature loss of workability. It is also more important to pre-wet absorptive brick in such weather just before using, but concrete block should not be pre-wet. It is also good practice under hot, dry weather conditions to mix smaller batches than usual.
Mortar for bed joints should be spread thickly and uniformly.
(Above) The head of the brick is well buttered with mortar before being "shoved" into a full bed. (Right) Brick being placed should be thickly buttered on the end and "shoved" into place. Both the head and bed joints should be completely filled so that excess mortar is squeezed out. (Below) Before placing the closure brick, mortar should be buttered on the ends of brick already in place. Mortar is also placed on both ends of the closure brick. (Bottom) The closure brick is then pressed into place.
The first rule of good workmanship in brick masonry construction is to fill all head joints and bed joints completely with mortar. Expert bricklayers "shove" brick into a full bed of mortar so that excess mortar is squeezed out on both sides of the head and bed joints. This assures full vertical and horizontal joints and helps establish a good bond between the brick and mortar. Bed joints should not be "furrowed." With Adas Mortar Cement
, the mortar for the bed joints can usually be spread over several bricks, but care should be taken to gauge this length to the weather conditions so that the mortar is still soft and plastic when the bricks are bedded. It is a good idea occasionally to lift a brick that has just been bedded to see whether the mortar is properly sticking to the brick. (Below) Simple Test for Good Bonding-A quick field check to determine if the mortar is bonding properly to the brick can be made (left) by placing mortar on a brick and pressing another brick onto it until the joint Is full and mortar squeezed out. Then (right) pull apart. Mortar should adhere well to both brick as shown. If not, the brick may require wetting or the mortar consistency should be adjusted.
A most important factor in determining the water-tightness of a wall, provided that the wall has been properly designed and good mortar is used
FULL FACE-SHELL BEDDING FOR BLOCK
Face-shell bedding should be used in laying up concrete block except where good practice calls for full bedding. For the first course on the foundation, for pilasters* and where maximum strength is required, full mortar bedding should be used, that is, mortar is spread on the cross webs of the block as well as the face shells. In face-shell bedding, mortar should be spread fully to cover both the face shells of the block so that excess mortar will be squeezed out of the joints on both sides of the face shells when a block is laid in position. With block walls, face-shell bedding is preferred because it improves the ability of the wall to resist the passage of water. Head joints for block should be full of mortar on both the inner and outer edges.
Enough mortar should be used so that excess mortar will be squeezed out on both sides of the face shells. In placing a closure block, butter mortar generously on inside and outside edges of the blocks in place. Face shells of the bed should also be full of mortar. All edges of the closure block should be buttered before It is lowered into position.
Once a brick has been placed, any tapping into alignment with the trowel must be done while the mortar is still fresh and soft. Once the mortar begins to stiffen, any attempt to realign the brick may break the bond between the brick and mortar and destroy the water tightness of the wall at this point. If it should become necessary to shift the position of a brick after the mortar begins to set, both the brick and mortar should be removed from the wall and the brick relaid with fresh mortar.
Tooling of the mortar joints is an excellent practice to help assure weather-tight walls. When paring or plastering is not done, tooling is essential, and it is an excellent added precaution against water penetration even where the wall is plastered. Tooling is best done with a rounded tool
that will make a concave joint — this packs the mortar tightly against both masonry units, thereby producing joints highly resistant to passage of water.
See Also: BrickWork
Cement Plastering Brick