Papers by Keyword: Masonry

Abstract: This article presents the findings of a research on improving the properties of hemp masonry to meet the standard strength of non-load baring concrete blocks and assess its properties as energy conserving construction material according to specifications declared under the Ministerial Announcement of the Ministry of Energy. Production of hemp masonry used finely chopped hemp stalk with bark mixed with Type 1 Portland cement, sand and water to form 7.5 x 7.5 x 10 centimeters blocks. The ratio by weight between hemp and binder was 1:10 and the property was improved using Al₂(SO₄)₃, plasticizers, natural rubber latex and polymer. Compression strength, dry density, water absorption, thermal conductivity coefficient, specific heat value and OTTV were tested. The research found that hemp masonry improved using Al₂(SO₄)₃ at 10% by weight of hemp with polymer was the sample with properties within standard limits of non-load baring concrete blocks. The compression strength achieved was 2.79 MPa, dry density 990 kg/m³, water absorption 351 kg/m³, thermal conductivity coefficient 0.25 w/m°C, specific heat 1.12 kJ/kg°C and the highest OTTV of 45 w/m² was calculated for the southeast wall. This was lower than the minimum standard for masonry of energy conserved office building. Therefore, the masonry produced using hemp stalk with bark has the strength comparable to non-load baring concrete block and has the quality to protect heat from outside which is good for energy conservation construction practice.

Abstract: The research presented results on improving the properties of hempcrete and hemp concrete by pretreating the hemp surface using aluminum sulfate with 3 other additives including plasticizers, natural rubber latex, and polymer. The aim of the research was to investigate the changes in the compressive strength of the blocks. Hempcrete samples were produced with a ratio by weight of hemp to lime of 1:12 and a water content of 34.62% by weight. Hemp concrete samples had a ratio of hemp:hydraulic cement:soil of 1:4:8 and a water content of 34.62% by weight. Both samples were formed using a 7.5 x 30 x 10 cm steel mold. Results from the compressive strength test found that the strength for both hempcrete and hemp concrete improved using 10% by weight aluminum sulfate together with polymer had the highest increase in strength in comparison to the other cases in this study. The compressive strength obtained was 1.21 MPa for hempcrete and 2.83 MPa for hemp concrete, resulting in an increase of 55.13% and 194.79%, respectively. These results showed that this method for improving the properties of hemp concrete made its compressive strength higher than the standard for nonloadbearing concrete masonry as required by construction standards.

Abstract: The construction industry is undergoing another revolution, including the field of masonry construction. New materials and products for masonry are constantly being developed and construction details and implementation procedures are being resolved. Digitization and the introduction of automation in the masonry process (in prefabrication halls or on-site robotic bricklaying) are also an integral part of the development of the masonry construction industry. The topic of the following paper is a summary of problematic construction details of masonry buildings, i.e., the solution of the plinth console, the solution of the building opening, the bearing of lintels on the masonry and the bearing of the ceiling structure on the masonry wall. The results of laboratory tests are presented – the load-bearing capacity of the jamb of the building opening (accessory bricks / cut bricks in the jamb) and the load-bearing capacity of the lintel placed on the accessory edge brick. Furthermore, the paper deals with the construction of masonry buildings in the 21^st century, including the first results of a compressive load test on masonry walls made of precast small-format units. The conclusion of the paper points out the importance of correct design details of masonry buildings before their application (programming) in software controlling the automated masonry process.

Abstract: The present study aims to contribute to the knowledge of the mechanical properties of limestone blocks extracted from mines in the Republic of Moldova and used in a new masonry technology. The initial shear strength is examined based on laboratory work carried out on 5 samples from each of the 3 mines in different areas of Moldova. The strength calculation of the proposed masonry technology is carried out based on the standards for load-bearing walls and corresponds to the requirements. The results showed that Moldovan limestone blocks have high mechanical properties. The proposed masonry technology is based on the use of local materials and to increase the strength, instead of steel mesh, fibreglass mesh and epoxy resin will be used, which can be implemented in the Republic of Moldova. This research based on the use of local materials is significant for the development of the construction technology branch in Moldova.

Abstract: The normal and tangential adhesive strength between bricks and mortar in bed joints is the main parameter that determines the performance of masonry under biaxial stress conditions. This research aims to determine the possibility of increasing the tangential adhesive strength (shear) of masonry by using mortars reinforced with PET fibres obtained from recycled plastic bottles. Shear tests are proposed on simplified brick masonry specimens made with mortars containing PET fibres in percentages of 0.5%, 1% and 1.5% of the mass of cement and sand. It has been determined that the addition of PET fibres in percentages no greater than 1% increases the tangential bond strength. The addition of 0.5% PET fibres increases the tangential adhesive strength by 37% and 1% PET by 60%, while the addition of 1.5% PET fibres decreases the studied strength by 22.86%.

Abstract: This study presents a set of "particular" strength criteria of the constituent elements of masonry as a composite material constituted by homogeneous fragments of heterogeneous materials (brick and mortar) and contact interface (shear and normal adhesive strength). This paper proposes the expressions for calculate the values of each particular strength criterion used for the discrete modelling of masonry. The results were obtained based on the experimental study of stresses and failure modes in masonry specimens, mortar samples and brick units. There are determined a set of 8 particular strength criteria, which correspond to the actual work of the masonry constituent elements. Their use in the structural micromodelling of masonry allows to determine the body contact interactions, track the gradual accumulation of local stresses, exclude from the calculation model the elements in which a particular strength criterion has been exceeded, and modelling the degradation process.

Abstract: This study presents a new model to estimate the compressive strength of masonry prisms considering both crashing and splitting failure mechanisms of the masonry prisms. The model is developed considering a probability of events by defining the resulted failure of the masonry prism as the main event. On the other hand, the different modes of failure including crushing of brick units, crushing of mortar under compression stresses and splitting of the brick units and mortar under bilateral stresses have defined as sub-events of the resulted failure. Eventuaaly, the developed model is verified against extensive results of experimental tests of masonry prisms that published by other researchers. A comparison is conducted between the estimated strength and the experimental results as well as those obtained from several available models in term of statistical measures. Comparison results reveal that the new proposed equation exhibits very good agreement with experimental results and shows the best accurate estimations with less deviations compared with the other available equations. The new proposed equation shows a mean value of the experimental to the estimated compressive strength of masonry equals to 1.01 ± 0.35 and a coefficient of variations equals to 35.12 %.

Abstract: Increasing the durability of brick structures is a current requirement for reducing damage in particular natural disasters, over-pressure wind effects and extraordinary loads.The structures are designed today according to valid standards and on the basis of empirical experience. They are designed for extraordinary effects only in cases where this is required by regulations, especially fire regulations. For brick structures, it is often followed by established procedures and catalogue recommendations, and the solution of these structures is often considered banal. However, what if the damage exceeds the effects set by the standards. Therefore, this contribution is devoted to simple instructions for increasing the durability of low-floor masonry buildings above the normal limit given by the current construction and the applicable regulations.

Abstract: The following paper deals with the comparison of characteristic initial shear strength of masonry specimens made of innovative Heluz bricks and selected adhesives. The characteristic initial shear strength of masonry was determined according to ČSN EN 1052-3. Five different adhesives were tested in total. The characteristic initial shear strength of masonry was also researched depending on the amount of applied adhesive – this was determined for two adhesives. The specimens were made of three shaped bricks and a defined adhesive. Twenty-one large specimens were produced in total and they were put to the shear test in the age of one day. Adhesives available on the Czech market and foreign adhesives were tested. Selected adhesives were applied to the bed joints of bricks according to the usual standards. The produced specimens were stayed overnight in the production hall of the Heluz brick plant in Dolní Bukovsko and tested in the age of one day in the laboratory according to stated methods in appropriate norm. This paper deals with procedure of preparation of specimens, the course of the test and comparison of gained results.

Abstract: Structural strengthening using composite materials is nowadays one of the most interesting techniques to overcome weaknesses of masonry structures constituting large part of the building heritage. The use of FRCM composites is becoming more and more widespread due to some limitations of FRP retrofitting systems. In this framework, the presented experimental study is aimed at evaluating the in-plane and the out-of-plane behaviour of masonry walls strengthened with different types of FRCMs, analyzing in detail failure modes, capacity increments and efficiency of the strengthening systems when tested using two different configurations. To this purpose, bidirectional basalt grids and unidirectional steel fiber sheets, coupled with a lime based mortar, were used for retrofitting clay brick masonry walls subjected to diagonal compression tests and out-of-plane flexural tests. Experimental outcomes, when considering the in-plane or the out-of-plane direction, show that the adopted different layout strictly influences the flexural and shear strengthening efficiency of the reinforcement.