Joints between walls are very important for structural analysis of each masonry building at the global and local level. This issue has often been neglected in the case of traditional joints and relatively squat walls. At present, the issue of wall joints is becoming particularly important due to the continuous drive for simplifying structures, introducing new technologies and materials. Eurocode 6 and other standards (American, Canadian, Chinese, and Japanese) recommend inspecting joints between walls, but no detailed procedures have been specified. This paper presents our own tests on joints between walls made of autoclaved aerated concrete (AAC) masonry units. Tests included reference models composed of two wall panels joined perpendicularly with a standard masonry bond (six models), with classic steel and modified connectors (twelve models). The shape and size of test models and the structure of a test stand were determined on the basis of the analysis of the current knowledge, pilot studies and numerical FEM (Finite Element Method) - based analyses. The analyses referred to the morphology and failure mechanism of models. Load-displacement relationships for different types of joints were compared and obtained results were related to results for reference models. The mechanisms of cracking and failure was found to vary, and clear differences in the behaviour and load capacity of each type of joint were observed. The individual working phases of joints were determined and defined, and an empirical approach was proposed for the determination of forces and displacement of wall joints.

The article presents laboratory tests on the impact of the mixing water content used in the preparation of fresh mortar on the flexural and compressive strength of one of the dry-mix mortars produced by a leading European producer and dedicated to bricklaying with clinker elements. The development of these parameters in relation to curing time was also analyzed. The mortar samples were prepared from a factory-made mortar mix using 4.0 L (the value recommended by the mortar manufacturer), 4.5 L, and 5 L of water per 25 kg bag of ready-made, pre-mixed dry mortar mix. All samples were tested in five series after 5, 9, 14, 21, and 28 days of sample curing. The results of these tests showed that the use of 6 and 18% more mixing water than recommended by the manufacturer (4.5 and 5 L per bag) adversely affected the basic mechanical parameters of the tested mortar. Moreover, it was found that the highest compressive strength values were obtained after 21 days of curing and not after 28 days as usual. It was also found that hardening time and higher than recommended water content adversely affected the bending strength of the mortar.

This paper presents the development of a numerical model aimed at the simulation of nonlinear behaviour of traditional joints between walls made of autoclaved aerated concrete (AAC) masonry units. Nonlinear behaviour and cracking of AAC and mortar were simulated using the concrete damaged plasticity (CDP) model available in the ABAQUS finite element software. The paper also presents and discusses the results of an experimental campaign involving testing six T-shaped, monosymmetric samples with traditional joints between walls loaded in shear. The results were used to validate the numerical model. The validation confirmed that the model is capable of producing accurate results and predicting the structural behaviour with a reasonably good accuracy in elastic and post-elastic stages. Furthermore, a sensitivity study was conducted, in which the variation of elastic modulus, Poisson’s ratio, tensile strength, compression strength and fracture energy of AAC was investigated. Results showed that the variation of elastic modulus, tensile strength and fracture energy is most critical to the structural behaviour of the model, while variation of the remaining parameters has a negligible effect on the results.

The paper presents the results of the Authors’ tests on the joints in AAC masonry walls. The shape of the tested element and the test stand were fitted innovatively based on the Authors’ own experience as well as on the literature overview and numerical analysis. Cracking morphology and mode of failure were investigated. The relationship between the load and displacement for different types of joins was compared. The obtained results were also compared to the results obtained on the reference model, which was a model with a traditional masonry bond. In the remaining testing elements, the connection was realized with the use of steel connectors. Various mechanisms of cracking and failure have been observed as well as the behaviour and load-bearing capacity of joints were different. The obtained results encourage to further analyses focused on detailing the joints and application of new methods in the construction of the joints.

In recent years, the autoclaved aerated concrete has become as one of the most popular material used in erecting of small housings as well as multi-apartment residential buildings. Recommended construction technology involves the use of the ACC blocks arranged on thin bed joints, with the head joints left unfilled. Practice has shown that this type of construction is characterised by low crack resistance, which was also confirmed during experimental investigation [1]. One of the solutions to this problem, proposed by the staff of the Silesian University of Technology, was the superficial strengthening of such type of masonry walls. Strengthening materials tested so far (glass and carbon fibre mesh used in FRP system solutions) gave very promising results but a relatively high cost of the material itself constituted the main drawback. This prompted a further search for new and relatively inexpensive materials that would allow improving the use of the existing structures made of AAC blocks. The goal of the laboratory test results presented in this paper was to determine the influence of wall surface strengthening made of not expensive GRFP mesh (dedicated as reinforcement of thin external plastering in thermal insulation systems) on the behaviour and mechanical properties of masonry wallettes made of AAC blocks with thin joints. Three series of masonry specimens were tested: not strengthened wallettes (as reference members), walls with superficial strengthening only on one side and walls with both sides strengthened. A total of 18 specimens subjected to diagonally compressive loading were tested (6 in each series). The results turned out to be highly promising. Increasing of shear capacity of both types of superficially strengthened masonry in comparison with reference members was observed. The tests also allowed determining a positive effect of external reinforcement on the type of cracking and failure mode of such walls.