Hollow Concrete Block Masonry Research Articles

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.

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.

Experimental Evaluation of Compressive Properties of Early-Age Mortar and Concrete Hollow-Block Masonry Prisms within Construction Stages.

Early-age masonry structures require temporary support until they achieve full strength. Nevertheless, there is a limited understanding of the properties of freshly laid masonry and the design of newly constructed, unsupported masonry walls. This situation has led to numerous instances of structural damage and injuries to workers, prompting conservative construction bracing techniques. This paper presents comprehensive experimental studies on early-age mortar cubes and masonry prisms to assess the effects of curing time on the compressive properties of masonry assemblies, which is necessary for the design of temporary bracing. The change in modulus of elasticity and compressive strength of masonry prisms and mortar with curing time has been experimentally assessed. The results indicate that the compressive strength of freshly cast mortar cubes is relatively insignificant until approximately 24 h after construction, when it was observed to increase logarithmically. Regarding the performance perspective, the compressive strength of early-age masonry prisms is inconsiderable, less than 15% of full strength during the first day after construction. By contrast, regarding the life safety perspective, the compressive properties of a mortar joint within a masonry assembly (which is of more practical interest) appear to have no effect on the failure strength of concrete masonry prisms over the range of ages tested. The failure modes of the early-age mortar cubes and early-age masonry prism samples depend on the curing time, and different failure modes occurred before and after the start of the primary hydration phase, which is 20.8 h after construction. It is anticipated that the proposed research will provide valuable material properties leading to efficient design of control devices (e.g., temporary bracing) and improved guidelines for concrete-block masonry construction.

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.

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.

Compressive strength prediction of hollow concrete masonry blocks using artificial intelligence algorithms

In this study, artificial intelligence algorithms are proposed for estimating the compressive strength of hollow concrete block masonry prisms, including neural networks (ANN), combinatorial methods of group data handling (GMDH-Combi), and gene expression programming (GEP). To train and test the proposed models, 102 samples of hollow concrete prisms from previous research works were collected. The height-to-width ratio of hollow concrete prisms and the compressive strength of mortar and concrete blocks were considered as inputs. In order to evaluate the validity and predictability of the proposed models, they were compared with empirical models and models presented in codes and standards. Among the suggested and existing models, the ANN model with an R-value of 0.950 and MAPE error value of 6.921% had the best performance, which with a more complicated equation, can be used in the scientific aspect. In contrast, the other two proposed models (GMDH-Combi and GEP) with acceptable performance and accuracy levels and more simple closed-form equations can be utilized in practical aspects. Based on the parametric analysis, the proposed models were highly efficient and accurate. Moreover, the sensitivity analysis results showed that in all three proposed models of ANN, GMDH-Combi, and GEP, the compressive strength of concrete blocks was the most effective input parameter in the compressive strength estimation of hollow concrete prisms.

Studies on Strength of Hollow concrete Block Masonry Externally Bonded with Textile Reinforced Mortar Composites

The aim of present study is to determine the mechanical properties of hollow concrete block masonry externally bonded with coir and glass textile reinforced mortar composites. The properties of textile composites were determined by testing TRM Coupons. A total number of 39 prisms were cast. The block masonry prisms were externally bonded with coir and glass textile fibre mesh with mortar. The elastic properties of block masonry, shear and flexural strength were determined for both unreinforced and strengthened specimens. The results showed that increasing the number of layers of textile fibers, enhanced the flexural capacity of TRM coupons. The provision of connectors also enhanced flexural strength. The stiffness of unreinforced masonry prisms was found to increase by strengthening with textile reinforcements even though the increase in compressive strength is marginal. There is a significant enhancement in flexural strength and shear bond strength when compared to unreinforced masonry.

Confined hollow concrete block masonry buildings: An experimental approach for vulnerability assessment

This paper presents experimental study on the response of a sustainable structure 3.65 x3.05x3.35 m, made with confined hollow concrete block masonry (CHCBM). The model was tested under quasi-static cyclic test to assess the response against seismic load and to determine the potential vulnerability. Based on test data, envelope curves and bilinear idealized curves were drawn according to both Magenes–Calvi and Elnashai methods. Different performance levels i.e. Immediate Occupancy (IO), Life Safety (LS) and Collapse Prevention (CP) were evaluated based on both methods. Damage pattern and force-deformation behavior of CHCBM building was compared with models of the similar configuration and loading conditions. Similarly values of Response modification factor (R), Displacement Ductility (µD) and Displacement amplification factor (Cd) were calculated and compared with the previously tested models and it confirmed that CHCBM building was ductile and structurally integrated under earthquake loading.

Study on overstrength and ductility of reinforced concrete building with different infill through nonlinear analysis

The building structure with infill wall shows higher global stiffness along with the uncertain behaviour during 2015 Gorkha earthquake. It significantly increased the collapse rate of structures during earthquakes. The response of buildings with different infills during seismic excitations is not completely accounted by current seismic codes in the region. On the other hand, due to the different geological region, availability of infill materials for reinforced concrete building also differs on region to region. In most of the situations the burnt clay brick, concrete blocks and stone block are used as infill materials during building construction. In this scenario, this study explores the importance of selection of right infill material for better seismic performance during earthquakes. For this, building constructed at Pokhara Metropolitan City is considered for case study. The structural model is prepared with and without considering infills. The solid, hollow concrete block and clay brick masonry are taken as infill material during analysis. The structural behaviour during earthquakes is studied with non-linear static pushover. The result shows that the hollow concrete block masonry infill (INHB) shows better structural performance compared to other infill types.

Numerical study of composite material (FRP/TRC)-reinforced masonry walls under in-plane loading

Fibre-reinforced polymers (FRPs) and textile-reinforced concretes (TRCs) are becoming increasingly common solutions for strengthening masonry walls. This study focuses on different approaches for modelling the behaviour of hollow concrete block masonry walls strengthened with FRPs and a TRC subjected to in-plane loading. Specifically, the masonry is modelled using the heterogeneous approach, wherein the damage post-peak softening behaviours of both bricks and mortar are considered, as this approach is appropriate for material and structure scales. To model the FRP/TRC-reinforced masonry walls, the reinforcements (FRPs/TRC) are perfectly connected to the substrate. Although the homogeneous approach is proposed to model the FRPs with linear elastic behaviour and is shown to be appropriate for modelling the FRP-reinforced masonry walls, the TRC is modelled using the heterogeneous approach, allowing for the real contribution of the filaments to be expressed through an ‘efficiency factor’. The numerical results show that this factor has a significant influence on the behaviour of the TRC and therefore, on the overall behaviour of the TRC-reinforced walls. However, the ‘efficiency factor’ of the TRC sample is significantly higher than that of the TRC in the strengthened wall. This result confirms that the choice of the heterogeneous approach to model the TRC in our case is appropriate. Moreover, it verifies that it is impossible to transpose this global factor from the material scale (uniaxial tensile stress) to the structure scale when the application target is a masonry wall (multi-axiality, and therefore, complexity of the stress). Consequently, the constitutive laws of the TRC composite obtained through only direct uniaxial tensile characterization procedures are insufficient to enable a suitable restitution of the overall behaviour of the masonry reinforced with the TRC. In addition, regardless of the nature of the reinforcement, the overall behaviours of the masonry walls reinforced with the FRPs/TRC are governed by both the axial stiffness of the reinforcement and the compressive strength of the masonry substrate.

The strength of hollow concrete block walls, reinforced hollow concrete block beams, and columns

This study aimed to determine the strength of hollow concrete block masonry walls, beams, and columns and compare their values with brick masonry walls and ordinary reinforced concrete beams and columns. The specimens for the hollow concrete block and brick masonry walls were prepared and tested for compressive and flexural strengths and horizontal and diagonal shear strengths. Moreover, two hollow concrete blocks and two ordinary reinforced concrete beams were designed to experience flexural and shear failure and loaded under a two-point bending load. Meanwhile, a hollow concrete block and an ordinary reinforced concrete column were also constructed and subjected to centric axial loads until they collapsed. The results showed the hollow concrete block masonry walls have greater strength than those made with bricks. In contrast, both flexural and shear capacity and the flexural ductility of reinforced hollow concrete block beams were higher than ordinary reinforced concrete beams. Meanwhile, the centric compressive axial strength of the reinforced hollow concrete block column was smaller due to its inefficient bond with the infilled concrete, leading to their separation under the compressive axial load.

The effect of mortar grade on the out-of-plane behaviour of low-strength masonry wall strengthened with welded wire mesh

The present study aims to understand the effect of mortar grade for bonding the masonry units, on the out-of-plane flexural behaviour of low-strength hollow concrete block masonry walls strengthened with welded wire mesh (WWM). Static out-of-plane flexural tests were performed on unstrengthened and WWM-strengthened specimens constructed with three different mortar grades representing strong, medium and weak mortar. It is observed that mortar strength do not have any profound effect on the flexural strength of unstrengthened specimens. The increase in mortar strength increases the flexural strength and ductility of WWM-strengthened specimens. However, there is insignificant difference in ductility between medium and strong mortared WWM-strengthened specimens. The failure of WWM-strengthened specimens is restricted to the masonry walls only suggesting overstrength of WWM. The comparison of experimentally evaluated flexural strength is also compared with existing analytical formulations displaying good agreement between experimental and analytical formulations.

Compressive strength and deformation characteristics of concrete block masonry made with different mortars, blocks and mortar beddings types

Concrete hollow block masonry is widely used in North American and Australasian countries because it enables to accommodate grouting and reinforcement to resist higher axial and lateral actions, where it ultimately facilitates to construct high-rise masonry buildings. Subsequently only certain grades of mortars are recommended for the concrete block masonry in the standards mainly due to durability concerns. However, there is a lack of knowledge on the characteristics of concrete masonry with different grades of mortars and significant variations are found among the design standards. Therefore, in this research, an attempt has been made to investigate the compressive strength and deformation characteristics of concrete block masonry using different mortar grades, mortar bedding types and block types. In total, 40 concrete block masonry prisms were constructed and tested with three different types of mortars, two mortar bedding types and two types of concrete blocks. From the experimental results, the failure modes, compressive strength and stress-strain curves are derived and discussed. The experimental results revealed that the lower grade mortared prisms failed by mortar crushing and block splitting, whereas the other mortared prisms mainly failed by tensile splitting in the blocks. The compressive strength of concrete masonry was not significantly compromised for lower grade mortared prisms in comparison to other mortared prism combinations. The deformations and failure phenomenon of the mortar joints, blocks and prisms were investigated in detail using a non-contact digital image correlation (DIC) method. The experimental results were also verified through the finite element analyses and were compared with the predictions of four different masonry design standards. Discrepancies in the prediction of compressive strengths of concrete block masonry between the design standards were noted.

Strengthening of elevated home slabs on grade with external fiber-reinforced polymer (FRP) laminate

Concrete slab on grade homes are being increasingly elevated above the base flood elevation for mitigation of coastal and inland flooding. This is typically accomplished through placing additional beam and pier supports under a raised slab home. In this process, the slab support conditions are changed from uniform soil support to beam supports. This may lead to unanticipated stress/strain changes, concrete cracks and slab failure. This paper presents a numerical parametric study of such elevated slabs with non-linear finite element approach. The models were calibrated with data obtained from full-scale testing of two concrete slabs under uniform floor load, one of which was retrofitted with external carbon fiber reinforced polymer (CFRP) laminates at critical locations. The slabs were supported by typical wide-flange steel beams over hollow square concrete block masonry piers. The results showed that typical elevated slabs can behave in a brittle manner with low ductility and sudden explosive collapse. A single layer of a uniaxial CFRP application at the negative moment locations increased the floor load capacity by about 30% and more than three times the minimum building code specified live load. Increased beam spacing and lower slab thickness decreased the slab load capacity, as expected.

Experimental behaviour of unreinforced and reinforced concrete block masonry walls under uniaxial compression

This paper presents the details of experimental investigations on the compressive strength of full scale hollow concrete block masonry walls. Comparison of load carrying capacity of unreinforced masonry walls with reinforced masonry walls have been studied as part of this study. The failure mechanism of reinforced hollow concrete block masonry (RHCBM) walls and unreinforced hollow concrete block masonry (URHCBM) walls have been studied. It is observed that the load carrying capacity of RHCBM walls are about 39.40% higher compared to URHCBM walls which is due to presence of marginal amount of reinforcement (about 0.12% of cross sectional area) and grout.

Analysis of uniaxial compression behavior of hollow concrete block masonry: experimental and analytical approaches

This article focuses on the uniaxial compression behavior of concrete hollow brick masonry assembly. This study was performed both by experimental and analytical approaches. In the first experimental part, the compression tests were done according to the European standard EN1052-1. It is highlighted from the tests that this concrete hollow brick masonry is a very high dispersive material and that the compression behavior of this masonry is similar and depends principally on that of bricks. In addition, the vertical splitting failure modes reflect the effect of "expanding/restraining" for this type of masonry and the elastic properties determined from these tests are comparable with the values found in the literature. Then, in the analytical approach, the simple calculations were done by different existed models to predict the compressive strength of masonry prism. A comparison of the results obtained by using these models with those of experimentation shows that only the model which takes into account the effect of vertical joints is mostly adapted for the safe design of this masonry prism under uniaxial compression load.

Analysis of uniaxial compression behavior of hollow concrete block masonry: experimental and analytical approaches

This article focuses on the uniaxial compression behavior of concrete hollow brick masonry assembly. This study was performed both by experimental and analytical approaches. In the first experimental part, the compression tests were done according to the European standard EN1052-1. It is highlighted from the tests that this concrete hollow brick masonry is a very high dispersive material and that the compression behavior of this masonry is similar and depends principally on that of bricks. In addition, the vertical splitting failure modes reflect the effect of "expanding/restraining" for this type of masonry and the elastic properties determined from these tests are comparable with the values found in the literature. Then, in the analytical approach, the simple calculations were done by different existed models to predict the compressive strength of masonry prism. A comparison of the results obtained by using these models with those of experimentation shows that only the model which takes into account the effect of vertical joints is mostly adapted for the safe design of this masonry prism under uniaxial compression load.

Effect of slenderness and eccentricity on the strength of concrete block masonry: An experimental investigation

There are a number of factors which govern the strength of masonry, namely strength and elasticity of masonry units and mortar, slenderness ratio of the wall, nature and magnitude of eccentric loads and masonry efficiency. There have been a number of publications on these factors, although many are with respect to brick masonry or masonry used in western countries. This is perhaps the first study in Indian Literature where a detailed study of hollow concrete block walls has been made. Experimental investigations on the masonry walls with two types of hollow blocks for the influences of slenderness ratio and eccentrically loaded walls have been studied in this paper. It is also necessary to observe that full-scale wall strengths have not been studied adequately in the Indian Context. The entire testing program was concentrated on the cellular concrete block and hollow concrete block masonry. The full-scale walls of two different sizes, i.e., 150-mm blocks and 200-mm blocks, were tested for hollow concrete blocks, whereas only 200-mm-thick blocks were tested for cellular concrete blocks. A total of nine walls were tested, out of which five walls were subjected to the axial type of loading, and the remaining four walls were subjected to eccentric loading. The test results confirm the better performance of hollow concrete block masonry as compared to brick masonry wall specimens tested by previous researchers.