Concrete Block Masonry Research Articles

Influence of Loading Direction on Compressive Strength of Concrete Block Masonry

Influence of Loading Direction on Compressive Strength of Concrete Block Masonry

Analysis of behavior and uniaxial compression failure modes in ungrouted hollow concrete block masonry and their implication in design expressions

In this study, new analytical expressions for the design and revision of ungrouted masonry of hollow concrete blocks under gravitational effects were developed. These expressions can predict the compressive strength and modulus of elasticity for full and face-shell mortar beddings. A trend chart was generated, considering various modes of failure for different strength relationships between blocks and mortar. The study revealed that the main international masonry design codes underestimate the compression resistance of masonry when using weak mortar in combination with full mortar bedding. Results obtained using the Finite Element Method indicated that the optimal compression strength ranges were: 62–70 % for weaker mortar than the block with full mortar bedding; 152 % for block weaker than the mortar with full mortar bedding; and close to 67 % with face-shell bedding mortar.

Application of Experimental Studies of Humidity and Temperature in the Time Domain to Determine the Physical Characteristics of a Perlite Concrete Partition

These days, the use of natural materials is required for sustainable and consequently plus-, zero- and low-energy construction. One of the main objectives of this research was to demonstrate that pelite concrete block masonry can be a structural and thermal insulation material. In order to determine the actual thermal insulation parameters of the building partition, in situ experimental research was carried out in real conditions, taking into account the temperature distribution at different heights of the partition. Empirical measurements were made at five designated heights of the partition with temperature and humidity parameters varying over time. The described experiment was intended to verify the technical parameters of perlite concrete in terms of its thermal insulation properties as a construction material used for vertical partitions. It was shown on the basis of the results obtained that the masonry made of perlite concrete blocks with dimensions of 24 × 24.5 × 37.5 cm laid on the mounting foam can be treated as a building element that meets both the structural and thermal insulation requirements of vertical single-layer partitions. However, it is important for the material to work in a dry environment, since, as shown, a wet perlite block has twice the thermal conductivity coefficient. The results of the measurements were confirmed, for they were known from the physics of buildings, the general principles of the formation of heat and the moisture flow in the analysed masonry of a perlite block. Illustrating this regularity is shown from the course of temperature and moisture in the walls. The proposed new building material is an alternative to walls with a layer of thermal insulation made of materials such as polystyrene or wool and fits into the concept of sustainable construction, acting against climate change, reducing building operating costs, improving living and working conditions as well as fulfilling international obligations regarding environmental goals.

Experimental investigation of the effects of different reinforcement configurations on the shear strength of reinforced concrete block masonry

Reinforced concrete block masonry walls exhibit complex behaviour under lateral loading due to their composite nature and the interaction between their constituents, including units, mortar, grout, and reinforcement. The shear strength of reinforced masonry walls depends on various factors, including the properties of each constituent material, wall geometry, boundary conditions, and the presence of reinforcement with different configurations. International masonry design standards vary significantly in how they address the parameters influencing the shear capacity of reinforced masonry shear walls. Consequently, the predicted capacities show varying levels of conservatism when compared to experimental values. Given that masonry materials and construction practices are similar in the countries being compared, these discrepancies suggest differing interpretations of the significance of each parameter and possibly different philosophies regarding the balance between conservatism and accuracy in shear design. Therefore, this study investigated the influence of different reinforcement schemes on the shear strength of reinforced concrete block masonry (RM) assemblages with running bond. Forty-one concrete block masonry assemblages were tested under diagonal tension following the ASTM E519 to examine the effect of various parameters, namely, the presence of vertical or horizontal reinforcement, the vertical and horizontal reinforcement ratios, and the spacing and combination of vertical and horizontal reinforcement within the masonry assemblages. The behaviour of the masonry assemblages was evaluated based on the maximum shear stress and the corresponding shear strain, shear modulus, toughness, and pseudo-ductility. Furthermore, the effect of the studied parameters on the stress-strain curves, failure mechanisms, and crack propagation was assessed. The obtained maximum shear stresses of the tested concrete block masonry assemblages were compared with the nominal shear capacity calculated using codified equations of different design standards. The RM assemblages showed an enhancement in the shear behaviour, ductility, and distribution of cracks, especially when combining horizontal and vertical reinforcement. The results showed that adding vertical reinforcement improved the shear capacity of reinforced masonry assemblages by 21%, with an increase in the peak shear strain by 52%. Moreover, combining the vertical and horizontal reinforcement in the reinforced concrete block masonry assemblages increases the shear capacity by 15% with an enhancement in the maximum shear strain by 23%. The CSA S304–14, TMS 402/602–22, and NZS 4230 showed an underestimation of the actual shear capacity of masonry assemblages constructed in running bond and with vertical reinforcement by 177%, 138%, and 79%, respectively. Additionally, the results revealed the need for a re-evaluation of the above mentioned code equations that estimate the shear capacity for different configurations of concrete block masonry assemblages. The analyses aimed to provide insights into the effectiveness of different reinforcement configurations in enhancing the shear resistance of RM walls. The findings of this research contribute to the development of optimized design guidelines for reinforced masonry structures, thereby enhancing their overall seismic performance and safety.

Carbon Footprint Assessment: Case Studies for Hemp-Based Eco-Concrete Masonry Blocks

In recent times, climate change has become more evident than ever, and measures to slow down its negative effects are imperative for the future of the world. The scientific and economic communities of countries around the world, under the force of international climate agreements, are identifying solutions to reduce greenhouse gas (GHG) emissions by establishing appropriate measures and developing new strategies. In the context of these objectives, the effort to identify eco-sustainable practices for the construction industry is growing significantly. Recently, much research has focused on solutions for producing green building materials, as well as applying circular economy principles to achieve a balance between anthropogenic emissions and absorptions by greenhouse gas absorbers. The relevant indicators of the level of achievement of these major objectives can be identified, already from the construction design phase, with the help of Life Cycle Assessment (LCA) analysis. This paper presents a series of environmental impact analyses for an eco-friendly solution of precast concrete masonry blocks. Ecological concrete is manufactured with aggregates from biological waste resulting from hemp crops. Impact assessments were performed with the SimaPro 9.5 software application. Research has shown that in the production chain, which includes the materials resulting from the recycling and reuse of hemp concrete blocks, the contribution to the effort to achieve neutrality in terms of global warming is significant. The Cradle-to-Cradle scenario revealed that the recycling of hemp concrete masonry blocks at the end of their use, for a functional unit of 0.5 m3, has a GHG emission of 33.5228 [kg CO2-eq] and CO2 uptakes can reach the negative value of −53.8397 [kg CO2-eq]. Thus, the balance of GHG emissions is negative, with values of approximately −20.3169 [kg CO2-eq]. The LCA analyses also reflect a decreased damage to human health, natural resources, and biodiversity when hemp concrete is used for masonry blocks.

REDUCING THE INFLUENCE OF THERMAL BRIDGES IN THE BASEMENT SLAB OF CAST-IN-SITU FRAME BUILDINGS IN EXTREMELY COLD REGIONS

Introduction. Heat insulation of multi-story buildings with a reinforced concrete frame on pile foundations under climatic conditions with extremely low outdoor air temperatures is complicated by high air infiltration. When such buildings are used in winter, the most characteristic are temperature regime violations on the first floor. Purpose of the study: The study aimed to evaluate various methods to reduce the influence of thermal bridges in the basement floor of a cast-in-situ frame building with pile foundations under extreme climatic conditions. Methods: Thermal performance of 3D models of enclosing structures was determined using the certified HEAT3 program. Options of internal and external heat insulation of the basement floor with thermal breaks in the structures were considered. Results: As a result of numerical analysis of standard basement floor designs, it was established that low temperature on the inner surface and significant heat losses are associated with the presence of through thermal bridges: reinforced concrete raft — basement slab — column — concrete block masonry. The most effective solution for heat insulation of cast-in-situ frame buildings is external heat insulation of the basement floor with a thermal break in the raft. Compared to the standard solution, heat losses through the corner section of the slab with the offset column are reduced by 33.6 %, and the minimum temperature on the inner surface is higher than the dew point.

A unified theory for predicting the compressive stress–strain curve of concrete block masonry

I-type internal structures are commonly present in concrete hollow block masonry. A unified theory based on I-type internal structures is proposed to analyze types of masonry systematically. In this unified theory, the I-type element represents the I-type internal structure; the equivalent frame is introduced to analyze the interaction between the block and grout; and the characteristic strength of mortar is employed to measure the performance of mortar in masonry. Each subtheory of the unified theory is independent, and the application scope of this theory can be expanded by adjusting the subtheories. The predictions of the unified theory for the compressive behaviors of fully grouted, partially grouted, and ungrouted masonry are well matched with the measured data. Through targeted adjustments, the prediction of this theory for special cases is also accurate. The calculation results suggest that the unified theory can effectively analyze different types of masonry with an I-type internal structure.

A Comparative Life Cycle Assessment (LCA) of a Composite Bamboo Shear Wall System Developed for El Salvador

To meet the UN sustainable development goal targets by 2030, it is necessary to provide adequate, resilient, and affordable housing solutions which are also low-carbon. In the context of affordable housing in El Salvador, an improved vernacular construction system, following the composite bamboo shear wall (CBSW) technology, has been developed as a feasible option to fill the current housing deficit. A life cycle assessment (LCA) has been conducted comparing a house built using the CBSW system with a reinforced concrete hollow block masonry system, considering the A1 to A5 (raw material production and manufacture) and B4 (replacement) life cycle modules. The LCA scope was limited to modules where there was sufficient confidence in the inputs. End-of-life modules were excluded as there is a large degree of uncertainty in the end-of-life scenarios for these materials in the regional context. The LCA results show that the CBSW system has approximately 64% of the global warming potential (GWP) of the reinforced masonry house, and when considering biogenic carbon, this reduces to 53%. There is additional potential to minimise impacts and maximise end-of-life opportunities (e.g., re-use, biofuel, etc.) for the biomaterials within the CBSW system, if considering modules beyond the scope of this paper, and this needs further study. Nevertheless, the results from this LCA—of limited A1 to A5 and B4 scope—show that the CBSW system has significant sustainability advantages over conventional construction systems and is considered a promising solution to alleviate the housing deficit in El Salvador.

Predicting compressive strength of hollow concrete prisms using machine learning techniques and explainable artificial intelligence (XAI)

The design of masonry structures requires accurate estimation of compressive strength (CS) of hollow concrete masonry prisms. Generally, the CS of masonry prisms is determined by destructive laboratory testing which results in time and resource wastage. Thus, this study aims to provide machine learning-based predictive models for CS of hollow concrete masonry blocks using different algorithms including Multi Expression Programming (MEP), Random Forest Regression (RFR), and Extreme Gradient Boosting (XGB) etc. A dataset of 159 experimental results was collected from published literature for this purpose. The collected dataset consisted of four input parameters including strength of masonry units (fb), height-to-thickness ratio (h/t), strength of mortar (fm), and ratio of fm/fb and only one output parameter i.e., CS. Out of all the algorithms employed in current study, only MEP and GEP expressed their output in the form of an empirical equation. The accuracy of developed models was assessed using root mean squared error (RMSE), objective function (OF), and R2 etc. Among all algorithms assessed, XGB turned out to be the most accurate having R2 = 0.99 and least OF value of 0.0063 followed by AdaBoost, RFR, and other algorithms. The developed XGB model was also used to conduct different explainable artificial intelligence (XAI) analysis including sensitivity and shapley analysis and the results showed that strength of masonry unit (fb) is the most significant variable in predicting CS. Thus, the ML-based predictive models presented in this study can be utilized practically for determining CS of hollow concrete masonry prisms without requiring expensive and time-consuming laboratory testing.

Cyclic testing and diagonal strut modelling of different types of masonry infills in reinforced concrete frames designed for modern codes

This article presents an experimental study on cyclic testing of full-scale reinforced concrete (RC) frames designed for modern codes with three different masonry infills: burnt clay brick, fly ash brick, and autoclaved aerated concrete (AAC) block masonry. A digital image correlation (DIC) system was used to study, in detail, the failure pattern and the complex interaction between the infill and the surrounding frame. The experimental results were compared with the pre-existing analytical models for strength and stiffness to determine the best-fit model. The experimental results indicated that the masonry-infilled frames had higher strength, stiffness, and energy dissipation capacity compared to the bare frame, and brittle modes of failure were avoided due to the design for modern codes. The masonry infill altered the RC frame’s deformation pattern by constraining the end portions of the columns from moving laterally, resulting in widespread flexure cracks throughout the column’s height, unlike the bare frame, where cracking was limited to the end portions. The modification was minimal in the case of AAC block masonry infill. The AAC block infilled frame reached different damage states at lower drifts than the other two infill types. The strength and stiffness, separately, were found to be in good agreement with some of the existing models; however, none of the considered models could predict both stiffness and strength accurately.

Technical Evaluation of Block Masonry with Pozzolanic Additions

Tests are carried out on various specimens of concrete block masonry, replacing Portland cement with pozzolans available in the region of Antofagasta, Chile (fly ash, volcanic ash and desert dust). To characterize the strength of the masonry, individual blocks, prisms and small walls, made of concrete with different binder combinations cement-pozzolan are tested; the obtained resistances are compared with standard mixture (100% cement). The results indicate that it is feasible to replace a percentage of Portland cement with pozzolans, obtaining very similar resistance, contributing to the reduction of construction costs and also, contributing to the environment by reducing cement demand and thereby reducing emissions of greenhouse gases that are generated in the calcination of the raw material. It is also pretension to enhance the importance of the masonry of concrete blocks in the construction of low-cost housing (economic and ecological).

Improving the lateral load resistance capacity of cellular lightweight concrete (CLC) block masonry walls through ferrocement overlay

Cellular lightweight concrete (CLC) block masonry is an eco-friendly building material gaining popularity in both developed and developing countries. Despite its increasing use, the material's behavior under seismic loading remains insufficiently understood. This research involved quasi-static testing of two full-scale CLC blocks masonry walls strengthened with ferrocement overlay. One of the strengthened walls was subjected to confinement, while the other was unconfined. The aim was to assess their seismic performance by comparing force deformation curves, damping, stiffness degradation, and structural performance levels with non-strengthened walls. The findings indicate that the strengthened masonry outperformed the unreinforced version, suggesting that CLC block masonry exhibits potential for effective performance in low to moderate seismic zones.

Shaking table tests of a one-quarter scale model of concrete hollow block masonry houses retrofitted with fiber-reinforced paint

Unreinforced masonry (URM) buildings are prone to significant damage when subjected to ground motion. Some strengthening methods have been proposed to increase the seismic capacity. However, the widespread adoption of these methods faces various challenges, including economic constraints experienced by common people in developing countries, the complexity of implementation, efficiency, and seismic safety of each technique. This paper introduces a new retrofitting method of fiber-reinforced paint using fiberglass as the primary reinforcing material. The advantage of this technique lies in its simplicity and ease of application, with the added benefit of using the paint to improve the appearance of the house. Two 1:4 scale concrete hollow block (CHB) masonry houses were constructed to represent unreinforced masonry and retrofitted masonry structures using fiber-reinforced paint (FR-Paint). The shaking table test results indicate that the retrofitted house model showed improvements of up to 18 times in deformation capacity and up to 13 times in energy dissipation compared to the non-retrofitted house model. FR-Paint has a robust performance even in high input motion at a seismic intensity JMA of 7 (Japan Meteorological Agency). This confirms that this retrofitting method has a high earthquake-resistant performance.

Assessing Mechanical Properties of Concrete Block Masonry under Uniaxial Compression for Design Applications

Assessing Mechanical Properties of Concrete Block Masonry under Uniaxial Compression for Design Applications

Thermal behavior of dry-cast concrete blocks masonry walls at elevated temperatures

This study aims to contribute to a better understanding of the behavior of masonry structures in the event of a fire, addressing a critical gap in both local and international standards and design guidance. Particularly in Brazil, the widespread adoption of structural masonry contrasts with the absence of national standards for evaluations at high temperatures, mainly due to the scarcity of research on the subject, potentially leading to severe consequences for life safety and property losses. This paper addresses a comprehensive study on the thermal behavior of dry-cast hollow concrete blocks masonry at high temperatures. The study combines both experimental and numerical analyses and involves underexplored topics, including characterization of thermal properties at elevated temperatures of commonly used blocks, post-fire condition of masonry's components, and determination of isotherms in the masonry cross-section in scenarios with one or both faces of the wall exposed to fire (separating and non-separating walls). Despite differences in the physical characteristics of the concrete used in block production, the temperature dependency of thermal properties obtained during experiments showed similar to that in Eurocode 2. Numerical and experimental results also indicate a low influence of block strength and mortar joints on the temperature evolution within the masonry. A key finding refers to a relatively fast temperature increase during heating due to the small thickness of the shells and webs of the blocks, thus impacting the performance of masonry structures in fire.

Shear Strength of Concrete Block Masonry Using Direct Shear Test

Shear Strength of Concrete Block Masonry Using Direct Shear Test

Reinforced concrete block masonry walls under eccentric compression: Assessment using experimental and numerical data

This paper presents the outcome of a research study carried out to assess the eccentric compression behaviour of reinforced concrete block masonry (RM) walls. The design provisions pertaining to axial compression capacity of RM walls are overly conservative, especially where slender walls are to be designed. To verify the relevancy of the design provisions outlined in the Australian masonry standards (AS 3700), an experimental database of RM walls tested under eccentric compression was created by gathering data from the past studies. In total, 76 partially grouted (PG) and 18 fully grouted (FG) RM wall test data were gathered. The established database revealed that the performance of fully grouted (FG-RM) walls are generally overlooked. To fill this gap, a finite element (FE) based numerical modelling procedure was established to understand the performance of FG-RM walls under eccentric compression. The established FE modelling procedure was validated with a set of experimental results and the validated modelling procedure was then used to parametrically analyse the eccentric compression behaviour of FG-RM walls. In total, 72 FG-RM wall cases were numerically simulated under eccentric compression, varying slenderness ratios (15, 21, 26, 32, 37, and 42), grout strengths (20 MPa, 30 MPa and 40 MPa) and boundary conditions (pinned-pinned and fixed-fixed). The analysed numerical data along with the experimental database were then used to verify the design provisions outlined in previous version of AS 3700 (2011) and current version of AS 3700 (2018). It was found that the provisions specified in AS 3700 (2011) were overly conservative than the AS 3700 (2018), justifying the need of deliberate revisions in terms of the treatment of slenderness, eccentricity and grout strength for designing the RM walls under compression.

Evaluating the axial compression behaviour of hollow concrete block masonry walls with small-size openings: Various opening positions and their influence on experimental results

Openings such as windows or channels for ventilation and heating systems are commonly encountered in masonry buildings to meet with functional needs. Although these openings are known to reduce the strength and stiffness of masonry walls, however, the relationship between the position of openings and load bearing capacity of masonry walls is not well understood. Therefore, the primary aim of this study is to investigate the effect of double opening positions on the axial compressive behaviour of masonry walls constructed with hollow concrete block units. Seven one-half scale walls with different double opening positions were constructed using hollow concrete block units and subjected to a uniformly distributed axial load. The compressive performance such as the strength, stiffness, load-deformation behaviour, stress-strain response, cracking pattern and failure behaviour of the walls have been reported. The results indicate that the 50% reduction in sectional area ratio caused by introducing two small openings in the walls reduced the load bearing capacity by 36 to 50%. Measured ultimate strain values ranges between 5.5 to 38.8% reduction in walls with openings compared with the wall without opening. Vertical cracking, face spalling, and block rupture were the dominant failure modes for walls with double openings, in contrast to mainly vertical cracks observed in the solid wall. This research provides valuable insights into how the positions of double openings influence the performance and overall structural response of hollow concrete block masonry walls under compression load.

Flatjack application on existing hollow concrete block masonry

This work aims to validate new flatjack in evaluating existing hollow concrete block masonry. The flatjack method is used as a non-destructive on-site test in masonry structures to obtain the actual stress-strain curve of masonry and estimate its strength. This method is already internationally standardized by ASTM and RILEM standard codes. However, most of the studies, standards, and available jacks refer to masonry with solid units, such as bricks and stones. The research adapted the deformability test performed on hollow block walls with the double flatjack to estimate the elasticity module and the masonry compressive strength, validating this technique as non-destructive. Experimental test using the newly developed equipment was performed in existing masonry buildings. The estimated strength results were compared to test results provided by the company responsible for the construction. The methodology using the new equipment proved good results. The adapted deformability test can be carried out on-site elements to estimate the properties of masonry made with hollow concrete blocks.

Experimental investigation of the influence of head joints and grouting conditions on the shear strength of concrete block masonry

The nonlinear composite nature of masonry has limited theoretical understanding of material shear strength – especially with concrete block, where minimal experimentation has rendered the influences of two important variables (head joints, presence of grout) unknown. The effects of these variables were investigated experimentally on non-precompressed triplet specimens. Head joints did not influence shear strength statistically significantly: the proportion of grouted cores linearly increased shear strength. The provisions in the Canadian standard lacked accuracy when predicting partially grouted specimen strengths (overestimating up to 135%). Units from tested triplet specimens were also found to have similar compressive strengths to undisturbed units.