J. N. TUTT Jenkins & Potter, Consulting Engineers
The designers’ requirements for mortar (in the specification and drawings) may relate to compressive and/or flexural strength of masonry, resistance to chemical and frost attack, to abrasion and rain penetration, and accommodation of movement. The bricklayer is primarily concerned with workability and his efforts to achieve it may be at variance with the needs of the designer. Poor site practice has become the norm and re-education is needed to avoid problems of durability. Improved site supervision may be the first step.
Preliminary testing of mortar can be carried out. When disputes arise, site cube test results are not available until 28 days have elapsed. Chemical analyses are expensive and unreliable. Bond wrench tests are unproven. Codes contain well meaning but often unenforcible guidance. If progress is to be made, site mortar manufacture must comply with realistic and enforcible specifications. Simple and economic site methods must be developed to assess mortar quality, the use of a sharp nail is no longer adequate. Is off site ready-mixed retarded mortar the solution; is it sensitive to site malpractice; is works control adequate, are there long term durability problems?