Search

This paper discusses the results of tests to failure on eccentrically loaded clay brick prisms (93 mm thick, six courses, stack-bonded) and concrete block prisms (140 mm thick, two courses, stack-bonded). The blockwork prisms had both full and face-shell mortar bedding, and load was applied at the same eccentricity top and bottom (single curvature) at nominal values, in terms of thickness, of 0, t/ 12, t/6 and t/3. Elastic and ultimate load design methods used in structural masonry codes are also discussed., Proceedings of the Third Canadian Masonry Symposium '83: 06 June 1983, Edmonton, Alberta, Canada

A brief study has been carried out on the effect of temperature on brick suction or initial rate of absorption (IRA), which is a factor in determining the amount of water extracted from mortar placed between bricks. This is important during cold weather construction when the amount of water extracted determines the pore space available for expansive forces if the remaining water freezes at an early age. The study included extruded clay and shale, dry-press clay, sand-lime, and concrete bricks selected to include a range of control IRA (suction) values. Values were determined at 20, 10, -1.5, and -10 degrees C with water at 20 degrees C and at 20 degrees C with water at 10 degrees C. Results indicate a small reduction in suction with dropping temperature for low absorption bricks and a substantial drop for high absorption extruded and dry-press clay bricks at temperatures below 0 degrees C. It is concluded that bricks should be at temperatures above 0 degrees C to ensure maximum potential for reducing the moisture content of mortar during winter construction.

Ceramic wicks (Efflorwicks) were partly embedded in cyclinders of masonry mortars of various compositions, and the hardened mortars were alternately wetted and dried, which produced various amounts of efflorescence on the wicks. Portland cement in mortars contributed significantly to efflorescence. The alkaline material of the cementing substance of the mortars appeared to be an important source of the efflorescence.

Attention is drawn to a number of pertinent properties and characteristics of building materials which the designer may presently consider usefully, as well as to a number of other considerations with which little guidance can yet be given. Water is seen to be the great complicating factor which must be studied and understood in dealing with many problems involving stability and durability of building materials.

The constants in an idealized heat flow simulation are adjusted by non-linear regression to match the experimental results of 94 fire endurance tests performed at the Division of Building Research. They are then used to predict fire endurances. Confidence limits are assigned.

High-absorption brick were treated with a water-soluble silicone before they were combined with mortar into brick masonry. The resistance of the masonry to moisture penetration was much improved compared with that in which untreated brick or brick soaked in water had been used. The silicone pretreatment in some cases increased, in others decreased, the strength of bond in direct tension between brick and mortar compared with that obtained from the brick used dry. Outdoor exposure of brickwork samples demonstrated that silicone pretreatment of bricks resulted in cleaner-appearing brick masonry.

The durability of a brick with regard to freeze-thaw action depends on two factors: (1) the properties of the brick, and (2) the conditions under which it is used in service. This paper deals mainly with those service conditions that affect freeze-thaw action, particularly the temperature changes experienced by a brick in a wall and the amount of moisture in the pores of a brick when it is frozen. The movement of freezing planes through a wall, the number of freeze-thaw cycles and their dependence on the orientation of the wall, and various factors that affect a brick's moisture content such as geographical location and orientation are discussed in relation to freeze-thaw damage to bricks.

Researchers in brick masonry are cautioned about the pickup of capillary moisture by specially textured ends and faces of some bricks, when the ASTM test for initial rate of absorption is performed. This moisture may prevent a true evaluation of the characteristics of such bricks, particularly when it forms a large proportion of the total moisture gained in the initial rate of absorption test. The extra moisture may also lead to confusion of the results of research work in which close control of absorption characteristics is important.

A particular case of cracking and spalling of masonry mortar was attributed to the migration of soluble salts from the brick to the mortar. Experiments with bars of masonry mortars showed that their expansion was influenced by soluble salts in bricks. Efflorescence is therefore considered to be more than a problem of aesthetics; it may affect the dimensional stability and durability of masonry.

Changes in the moisture content and temperature of masonry materials exposed to the weather at two locations for two years depended on several factors. The moisture content was influenced mainly by the nature of the material exposed, its geographical location and direction of exposure, and the season of the year. The temperature also depended on geographical location and direction of exposure and on daily and seasonal changes in air temperature. The number of freeze-thaw cycles experienced by the samples was considerably influenced by the direction of exposure as well as by geographical location. The rate of freezing of the exposed samples and the moisture content when frozen--two factors important to durability--differed considerably from the freezing rate and moisture content used in a standard test for brick durability. The results of the exposure tests suggest that more realistic conditions should be used in laboratory freeze-thaw testing.