Specifications for reinforcement and accessory metals used in the construction of masonry walls is provided by International Building Code (IBC 2009) and Building Requirements and Specification for Masonry Structures (ACI 530.1-11).
Various types of reinforcement and metal accessories is discussed in the following sections.
Fig.1: Reinforcement Placement in Masonry Wall
Fig.2: Reinforcement and Accessory Metals Employed in Masonry Wall
- Masonry Reinforcement, its Types and Accessory Metals for Masonry Structure
Masonry Reinforcement, its Types and Accessory Metals for Masonry StructureMasonry reinforcement and accessories includes:
- Steel reinforcement
- Vapor and moisture barriers
Steel Reinforcement for Masonry StructureSteel reinforcement used in masonry structure involves reinforcement bars, joint reinforcement, and deformed reinforcing wire. Steel bars are utilized to improve both the tension and compression strength of the masonry structure. Masonry bond beams, lintels, and walls are examples in which steel reinforcement are applied to improve the tensile strength of the member whereas reinforcement bars are used in masonry column to increase its compression strength. Hot-rolled deformed bars, which possess ribs on its surface to enhance bond strength, are employed in a masonry structure. As per ACI 530.1-11, the maximum reinforcement steel bar size is No.11. The restriction on the size of reinforcing bars depends on the accepted construction practice and performance of the masonry structure. It is claimed that using and distributing small-size steel bars in masonry provides better performance compared with a small number of large-size reinforcements placed in the masonry structure. Figure-3 demonstrates installed deformed steel reinforcement bars in the masonry wall.
Fig.3: Utilization of Deformed Steel Bars in Masonry WallThe steel reinforcement bars are usually categorized based on the minimum yield stress of the steel employed to manufacture the steel bars. Both epoxy-coated and zinc-coated steel bars are permitted to use in masonry structures and they may be utilized when corrosion-protected reinforcement is specified as per the design. Both epoxy and zinc coats protect steel bars in severe conditions and consequently increase the life span of the structure. If steel bars are covered with an epoxy coat, then it is required to increase their development length and it should be 1.5 times the development length of uncovered bars. On the contrary, bars covered with zinc coats do not need to increase the development length because zinc provides the same property as uncoated bars. It should be said that delivery and installation of coated bars need considerable attention to avoid coating damages otherwise the purpose of steel coating will not be achieved. So, any damages experienced by steel coating need repair prior to installation. Figure-4 and Figure-5 show epoxy coated and zinc-coated steel bars respectively.
Fig.4: Epoxy Coated Steel Bars for Masonry Structures
Fig.5: Zinc Coated Steel Bars for Masonry StructuresThe fiber-reinforced polymer bars can be employed in masonry structures as a replacement of both zinc and epoxy coated bars in aggressive environments. Figure-6 provides different types of fiber-reinforced polymer bars. The FRP bar is available in different sizes and they are considerably light which is advantageous because it substantially decreases the cost of delivering, handling, and installation.
Fig.6: Various Types of FRP Bars for Masonry StructuresRegarding joint reinforcement, there are three types of joint reinforcement involves welded wire fabric, deformed reinforcing wire, and ladder or truss type joint reinforcement. Joint reinforcement is provided for a different reasons for example increase the size of a panel, increase the spacing between movement joints, and control differential movements. Added to that, it improved horizontal bending and restricts cracks in a masonry structures. Joint reinforcement applications are shown in Figure 7 and Figure 8.
Fig.7: Joint Reinforcement Applications in Masonry Structure Construction
Fig.8: Installation of Joint Reinforcement in Masonry Walls
Connectors for Construction of Masonry StructuresThere are various types of connectors that are used to connect or secure two members or parts together. For instance, ties can join two Wythe’s of masonry wall together and adjustable ties may be employed to make rooms for differential elevation in masonry bed joints.
Fig.9: Types of Adjustable Pintle Tie Used in Masonry Structure
Fig.10: Types of Veneer Tie Employed in Masonry Structure
Fig.11: Types of Connectors Used in Masonry Structure
Sealants in Masonry WallsSealants are employed to fill and seal the spaces or joints which are created deliberately in masonry walls for specific purposes. There are three major joints in masonry structures includes construction joints, expansion joints, and control joints. Sealants are usually produced from manmade polymers such as latex, silicone, neoprene, and butyl rubber. The elastic property of sealant including compressibility is equal to the ratio of minimum thickness to the original thickness. Based on the anticipated service life of sealants, deteriorated sealants need to be replaced by new ones. It is claimed that the ordinary life span of the majority of sealants, which are placed at the exterior face or walls is around seven-year. The main factor behind sealant deterioration is due to sealant exposure to ozone and ultraviolet light. This is because polymers that are utilized to manufacture sealants are damaged under such conditions. Figure-12 illustrates the application of sealants in the masonry wall joint, and Figure-13 shows sealants before and after the masonry wall expansion.
Fig.12: Use of Sealant in Masonry Wall Joints
Fig.13: Employing Sealant in Expansion Joints of Masonry Wall
Flashings for Construction of Masonry WallsFlashing is changeable and adaptive watertight material that may be manufactured from copper, stainless steel, plastic, plastic-coated aluminum, and rubberized asphalt. The life service of metallic flashing is considerably longer than plastic flashing that is prone to tearing. Rubberized asphalt flashing, which adheres to the masonry, can be installed easily and demonstrate reasonable durability. Flashings are installed at different locations of masonry walls, for example, all interrupted drainage cavities, the bottom of each story level, under the sills of windows and doors, and over lintels of windows and doors. It is applied to drain water that penetrates the external Wythe of the masonry wall. Weep holes at a spacing of around 61cm above the level of flashing. Figure-14 shows the installation of flashing and weep hole exactly above it in a masonry wall.
Fig.14: Installation of Flashing in Masonry Wall