Superficial strengthening of AAC block masonry using GFRP strips—Diagonal compression tests of small wallettes

In many countries the autoclaved aerated concrete (AAC) has become one of the most popular materials used in construction of small dwelling houses as well as multi-apartment residential buildings. It is also very popular to use AAC as masonry infill of frame or slab-column structures. Because of the recommended construction technology, the ACC blocks are arranged on thin bed joints, with head (vertical) joints not filled with mortar. Unfortunately, such type of masonry is characterised with low crack resistance. One of the solutions to this problem may be application of GFRP laminates as superficial strengthening assembled to one or both sides of a masonry wall. Taking into account rather high cost of this type of materials, the use of GFRP laminates for strengthening of masonry structures may be realised in a form of strips cut out from a mat and glued to the surface of the masonry wall. The presented laboratory tests were focused on the effectiveness of such type of strengthening for two orientations of GFRP strips: vertical and diagonal (inclined at the angle of 45 degrees to the bed joints). Three series (6 specimens in each series) of masonry specimens were tested: unstrengthened wallettes (as reference members), wallettes with strengthening on both sides with two vertical (in relation to bed joints) strips covering unfilled head joints, glued on each side, and diagonally-oriented strips glued on both sides. All specimens were subjected to diagonal compressive loading according to RILEM LUMB 6 recommendation. An increase in shear capacity of both types of strengthening with respect to unreinforced members was observed. The tests also allowed determining a positive effect of external strengthening and possibility to reduce the number of GFRP strips as well as recommended location and orientation of this external reinforcement with respect to the bed joints.