Masonry Magazine December 1995 Page. 17
However, many problems and misunderstandings can be avoided if this step is also used to confirm the capability of the mason contractor to provide an acceptable level of workmanship. In this case, the mock-up may include an example of the installation of flashings, weepholes, and other construction details that are required in the project. The mock-up should be retained for reference during construction and not removed from the project until the masonry has been accepted by the owner or his representative. All masons working on the project should review and understand the mock-up.
Scheduling. Coordination of the installation of masonry with the installation of other building elements is required on every project. The mason contractor must work closely with the general contractor or construction manager in advance of the work to assure compatibility of installation schedules and that adequate work areas are available for storing materials and for mixing mortar. Since construction schedules invariably change as a project progresses, communication with respect to the status of various phases of the construction process must be continuous throughout the duration of the project.
Planning must include consideration of special conditions or requirements specific to the project location and schedule. For example, masonry construction scheduled during winter months in northern climates will require use of adequate cold weather construction techniques. On some projects, availability of water and electricity may be limited. Careful planning can assure that provisions are made to handle these circumstances without compromising the quality of the completed masonry.
Storage of Materials
Materials stored at the construction site must be protected from damage by construction equipment, rain, snow, or other adverse environmental conditions.
Units. It is important to keep concrete masonry units dry prior to placement to minimize drying shrinkage of the concrete masonry assembly. Therefore, concrete masonry units should be stored in well drained areas on pallets or other supports such that the units are not in direct contact with the ground. They should be covered with canvas or polyethylene tarpaulins to assure that they are protected from rain or snow. Concrete masonry units should not be wetted immediately before or during placement.
Similar storage requirements are needed for clay masonry units as for concrete masonry units. Although clay masonry units do not exhibit drying shrinkage, brick stored at the job should be covered prior to use to prevent uneven wetting and accumulation of dirt. When using clay masonry units having a high initial rate of absorption (over 30 g/min. 30 sq in. (30 g/min. 194 sq cm)), improved bond can be achieved by wetting the brick before use. If wetting of such brick is required by project specifications, an effective procedure is to uncover pallets of brick the evening of the day prior to use and wet these brick thoroughly (it may be necessary to unband brick cubes and arrange brick in single-layer rows to assure uniform wetting). Overnight exposure to air and shading from direct sunlight the next morning should provide a fairly uniform damp, surface-dry condition needed to optimize the bond between mortar and unit. Alternatively, a row of clay brick units can be immersed in water using a brick tong. After immersion for approximately 1 minute, they should then be allowed to stand exposed to air until surface dry prior to use. It is important that unit surfaces are not saturated when placed in contact with mortar.
Cement. Packaged cementitious materials used for mortar should be protected from breakage and exposure to moisture. When stored for extended periods of time at high humidity and temperatures, a packaged cement may develop "packset" and hard lumps. It is often best to schedule multiple deliveries of packaged cement to the project rather than to risk storage of larger quantities at the job site for extended time periods.
Sand. The unit weight of sand is dependent on the surface moisture. Surface moisture on sand particles causes bulking, which is an increase in volume compared to dry, compacted sand. Maximum bulking can occur when moisture content is approximately 5%. Thus, a cubic foot of damp loose sand typically contains about 80 lb (1280 kg/m³) of sand on a dry basis. A cubic foot of dry sand usually weighs approximately 100 lb (1600 kg/m³). Since sand used in masonry mortar is generally proportioned by volume, the effect of bulking can be significant to the amount of sand batched with cementitious materials to make mortar. Requirements of ASTM C270, the Standard Specification for Mortar for Unit Masonry, are based on the assumption that sand used in construction is damp and loose. Sand should therefore be delivered, stored, and maintained in a damp-loose condition to avoid variations in proportioning. The sand pile should be covered to reduce evaporation and provide protection from rain or snow. In hot, dry weather it may be advisable to periodically spray water on the sand pile to keep it moist. Care should be taken to assure that the sand pile is not contaminated with mud or construction debris. It should be located in an area that is accessible and well drained.