ACI 549.4R-13 Guide to Design and Construction of Externally Bonded Fabric- Reinforced Cementitious Matrix (FRCM) Systems for Repair and Strengthening Concrete and Masonry Structures.
4.2—Masonry repair applications
4.2J Si enitheninr of unreinforcd masonry chimney— FRUM was used to strengthen the masonry chimney part of the now-closed sawmill Francois Uuny complex located in the municipality of Gerardmer. France (Nanni 2012). This chimney. a symbol of industrial heritage, was to be preserved and restored. The chimney has a height of approximately 124.7 (1(38 m) with a diameter ranging from 11.8(1(3,60 m) at the base to 5.6 ft (1.70 m) at the top (Fig. 4.2.1a. Today. the structure is used to support several telephone antennas and their cabling.
The technical challenge of the high capillary absorption of the clay bricks, including their sand-lime joints (Fig. 4,2.lb(a)), was addressed by using a cemenhitious repair mortar to rectify the existing surface without any surface pretreatment such as sandblasting. The chimney was analyzed as a cantilever beam with wind being the primary load condition. The analysis indicated that it was necessary to strengthen the structure with 0.47 in. (10 mm) thick FRUM reinforced by a single fiber mesh (Fig. 4.2.lb)),
4.2.2 School building sirengthening—FRCM was selected to strengthen a school building in Karystos. Greece (Triantafillou 2007). This involvcd both Ilexural strengthening of RU slabs with heavily corroded reinforcement and shear strengthening of unreinlbrced stone masonry walls, Strengthening was completed using fIber meshes combined with cementitious mortar (Fig. 4.2.2).
There are a variety offiber meshes available in the marketplace that could be potentially used as constituents of FRUM systems. In these meshes, the typical spacing of primary- direction (PD) and secondary-direction (SD) strands is less than I in. (25.4 mm). and the total coverage area of the fiber mesh is less than 2/3 oftotal area (that is. there is at least 33.3 percent of open area among strands). With reference to fiber types in particular, extensive descriptions of various physical and mechanical properties exists in the literature (ACt
440R-07: ACt 440 2R-08; ACt 440.7R-1O ACI 544.1 R-96; RILEM Technical Committee (TC) 201 ). Although a significant amount of research was carried out on the use of greige (uncoated) alkali-resistant (AR) glass fibers, the results, although interesting, appear to be of limited practical application. This is because AR glass meshes for the applications discussed in this guide are typically coated to improve their long-term durability in a cementitious matrix and for ease of handling and installation.
While many interesting and promising field applications have been undertaken, and FRCM technology has been proven reliable, experimental and theoretical research continues to fully characterize FRUM and quanti its mechanical effectiveness based on parameters such as type and arrangement of fibers, type of cementitious matrix, and conditions of the substrate (LiAmbrisi and Focacci 2011). Several analytical approaches are available that allow for measurement of the contribution of different reinforcement meshes and matrix systems using mechanics-based approaches (Mobasher 2012: Soranakom and Mobasher 201 Oa,h).ACI 549.4R pdf download.