Dry-stacked Masonry Research Articles

Experimental assessment of retrofitted damaged mortarless dry stacked interlocking masonry walls

The aim of this research study is to experimentally investigate the effectiveness of ferrocement overlay on the seismic capacity of damaged mortarless dry stacked masonry constructed with self-interlocking compressed earth blocks. For the achievement of the aim, two full scale damaged walls were retrofitted with ferrocement overlay technique. To study the effects of openings, one wall was provided with a window, while the other one was a solid wall. Retrofitting materials consist of 18-gauge galvanized steel welded wire mesh having opening size of 12.5 × 12.5 mm (0.5" × 0.5″) and 1:4 conventional cement-sand mortar. The walls were tested with displacement-controlled quasi static cyclic loading protocols. The seismic performance of the retrofitted walls under a combination of vertical axial load and lateral reverse cyclic loading was compared to the specimens before retrofitting. Damage patterns and different seismic parameters such as force deformation curve, energy dissipation, stiffness degradation and performance levels were assessed. The results show that the seismic capacity of damaged mortarless dry stacked interlocking masonry can be restored and enhanced as the overall response of the structure is significantly improved.

Numerical simulations on refractory linings for steel casting vessels

This paper presents an extensive numerical investigation for developing finite element models capable of simulating the thermal and mechanical response of dry-stacked masonry linings for steel casting vessels. The developed numerical models were previously validated with experimental results. The models were developed using the finite element software Abaqus. A meso-modelling approach was adopted, therefore, the units were modelled separately and connected to each other by surface-to-surface contact interactions. This work shows that the joints play an important role in dry-stacked refractory masonries reducing the stiffness of the linings and consequently reducing the compressive stresses developed in the working lining, and the tensile stresses in the steel shell. The influence of creep in the stress's development and the influence of the Young's modulus are also presented and discussed.

Improving seismic capacity of dry stacked interlocking masonry structure through confinement at corners

Interlocking dry stacked masonry is an emerging building material and has a project wining future due to its sustainable and affordable housing aspects. The aim of this research work is to study the improvement in seismic parameters of self-interlocking mortarless masonry by the provision of confinement at the corners. To fulfill the aim, a full-scale structure was fabricated by using locally prepared self-interlocking stabilized earth blocks and evaluated by testing through quasi-static test. Damaged patterns and different seismic parameters have been assessed, which include lateral load carrying capacity, energy dissipation, displacement ductility, structural stiffness, response modification factor and performance levels. On the basis of test data, the corners confinement of dry stacked masonry enhanced the ultimate lateral load and drift capacity by 64% and 288% respectively.

Behavior of unreinforced dry-jointed masonry walls at corners under lateral loads

This study is based on the simultaneous application of in-plane and out-of-plane seismic loads on unreinforced dry masonry (URM) walls. The mode of failure under such a type of loading is the separation of the corner portion from the rest of the structure. This type of failure generally occurs in old masonry structures in which the strength of the mortar has deteriorated, and the floor of the structure is weakly coupled with the rest of the structure. Such structures generally lack the box-type behavior of masonry buildings. Single-story dry-stacked masonry models were considered and subjected to bidirectional loading to study such failures. These masonry models were developed and analyzed using the finite-element (FE) software package Abaqus, and results were verified using experimental testing of the half-scaled model. Simplified corner failure mechanisms and limiting acceleration formulation were proposed based on the observed failure pattern.

Performance evaluation of confined dry-stacked block masonry against blast loading

The ascendancy of the current spate of home-grown and international terrorism increased the awareness of the possibility of cowardice terrorist attacks in Pakistan. Many buildings in Pakistan and other affected countries in the world, are at continuous risk of terrorist attacks including the buildings of Law Enforcing Agencies (LEA), education and health sectors. The revolution in masonry units has been extended from ordinary masonry units to mortarless interlocking blocks. Keeping in view, the astounding energy-dissipating capacity of dry-stacked block masonry, it was decided to explore the behavior of Interlocking Compressed Earth Block (ICEB) masonry against blast loading. Four confined masonry walls and a typical full-scale structure were subjected to blast load at different scale distances. The pressure sensors data, high-speed video, and post-testing inspection of the test’s specimens were assessed for the evaluation of structural performance against shock waves. It has been concluded that the ICEB has sufficient out-of-plane shear capacity against blast loading and the reinforcement detailing of the confining elements plays a vital role in the overall performance of the confined dry-stacked masonry.

Numerical Approximation of Blast Loads on Confined Dry-Stacked Masonry Wall

This research intends to numerically study the out-of-plane behaviour of confined dry-stacked masonry (CDSM) walls against blast loading. CDSM is a mortarless interlocking masonry system consisting of Hydraform blocks laid in stretcher bond with reinforced concrete (RC) confining elements. A nonlinear numerical model is developed using advanced finite element hydrocode ANSYS-Autodyn to study the response of CDSM walls subjected to explosive loads. Four different test cases using a charge weight of 4 kg, 8 kg, 12 kg, and 16 kg of Wabox explosive are investigated numerically. The results obtained from numerical simulation are validated with the experimental tests results. The numerical results are found in good agreement with the experimental results. The ability of the numerical model is studied to correctly predict the pressure-time history in pressure gauges installed on walls and compared with experimental data. Peak incident overpressures obtained in these numerical tests ranged from 240 to 1000 kPa. Likewise, the damage patterns obtained from the numerical simulations are compared with available experimental results which show a satisfactory agreement. This study helps to check the response of CDSM structures against blast load which can be used for the construction of blast resisting design of buildings.

Analysis of the geometrical imperfections of a dry-stacked masonry block based on Miscanthus

This paper aims to verify the suitability of masonry blocks based on Miscanthus concrete to be used in dry-stacked walls. Therefore, the load-bearing capacity of single Miscanthus concrete masonry blocks as well as of dry-stacked wallets based on these blocks is analysed in function of geometrical imperfections, such as possible height differences between adjacent blocks due to the production process or/and surface roughness of the dry bed joint. For the study on the load-bearing capacity of single masonry blocks the mixture composition was varied and optimised leading to a maximum ultimate load of 5.42 MPa. With the optimised mixture composition masonry blocks were produced to create small wallets, which achieved a maximum load-bearing capacity of 4.84 MPa. The Miscanthus masonry blocks presented a low Young’s Modulus leading to a very ductile behaviour of the wallet without sudden failure. Furthermore, the variation of the contact area as a consequence of geometrical imperfections was studied and an exponential relation between the contact area and the applied load could be established.

Thermomechanical behaviour of refractory dry-stacked masonry walls under uniaxial compression

Vessels used in industrial high temperature processes of steel and cement production are protected by refractory linings built with dry-stacked masonry, which plays a crucial role on the overall behaviour of the vessels. This paper presents the results of an experimental and numerical research on dry-joint refractory masonry subjected to uniaxial compression. Its main purpose is to fully characterize the masonry walls at different temperatures and different loading conditions. Several aspects that may influence the behaviour of these walls have been tested, namely the loadbearing capacity, the behaviour under cyclic loading and the restrained thermal elongation. The experimental results allowed to identify the effects of the stress concentrations caused by brick’s height imperfections in the mechanical behaviour of the bricks and in the loadbearing capacity of the specimens, the evolution of the wall’s Young’s modulus with the load application, the developed crack patterns and the mechanical behaviour of the samples at ambient and high temperatures. Numerical models were also developed to simulate the behaviour of the walls under different testing conditions and a good agreement with the experimental results was obtained. The concrete damaged plasticity model, using a micro-modelling approach, proved to be suitable for representing the behaviour of these walls at ambient and high temperatures.

The Impact of Various Soil Proportions Towards the Strength of Interlocking Compressed Earth Brick

An interlocking compressed earth brick (ICEB) is a dry-stacked masonry brick with a similar production process to the Compressed Earth Brick (CEB). ICEB mainly consists of clay soil, sand, ordinary Portland cement (OPC) and water. This paper studies the properties of a combined soil (clay soil and sand), which affects the optimum moisture content (OMC) of the mixture and compressive strength of the produced specimens. There are five types of combined soils with mixture ratios of clay(C) soil to sand (S) of C55:S45, C50:S50, C45:S55, C40:S60, C35:S65 and C30:S70. Every mixture ratio shows a different OMC and varies in its compressive strength. The combination soil ratio of C45:S55, which means 45% of clay soil + 55% of sand, produced the highest compressive strength. The compressive strength increases as the clay content decreases and sand content increases. However, as the clay soil content decreased to lower than 45%, the compressive strength starts to decrease. It is due to the lack of plasticity properties from the clay which are responsible for bonding the material particles.

Overcome of bed-joint imperfections and improvement of actual contact in dry-stacked masonry

Several researchers studied dry-stacked masonry walls (DSM) and inferred that the actual contact surface between the different block rows and the compressive strength in such walls are reduced by bed-joint imperfections as well as by height differences between different masonry blocks leading both to high stress concentration. This paper concentrates on the first type on imperfections. Through experimental tests, it analyses the influence of bed-joint roughness on the load bearing capacity and investigates a strategy to improve the load-bearing capacity of DSM by placing an additional horizontal layer on the top face of raw masonry blocks. First, different contact layers using conventional and auxetic materials were applied. Then 20 dry-stacked masonry prisms built with raw and improved masonry blocks were tested under axial compressive load until failure. Prescale Fujifilm strips were used to measure the actual contact in the bed-joints. Experimental tests show that the use of a contact layer with well-defined material properties enables firstly to increase the actual contact area in the bed-joints from 23% to 98% of the nominal contact area and secondly to increase the load-bearing capacity by 14–97%. In addition, the contact layer with an auxetic material shows a significant capacity in altering the lateral expansion in the block units. The outcomes show that although the bed joint roughness influences the stress distribution in a dry-stacked masonry block, a contact layer with well-defined material properties enables to overcome the roughness induced by the bed-joint imperfections.

Experimental and analytical analysis of the load-bearing capacity Pu of improved dry-stacked masonry

Dry-Stacked Masonry (DSM) as structural load-bearing element is still unexploited because of many factors including the early face-shell cracking, the impacts of the block imperfections on the wall load-bearing capacity (Pu) and the lack of design code safely predicting Pu. Through experimental tests, this paper investigates a strategy for improving Pu of DSM by placing an additional horizontal contact layer on the top face of raw DSM blocks. The effect of four mixtures used to improve the raw DSM blocks has been investigated. Further, a mathematical model predicting Pu is proposed which takes into account the effects of the block imperfections. In the course of the investigation, 20 DSM wallets and 25 DSM prisms built with raw and improved DSM blocks were tested to failure under axial compression. In the former, the face-shell cracking load (Pcrack) and the load-bearing capacity (Pu) were recorded, while in the latter, the actual contact area was recorded in hundred full bed-joints using Prescale Fujifilm strips. The results showed that a contact layer of well-defined properties increased the actual contact area from 23% to 55% and improved Pu by 31,9%. The mathematical model for the raw DSM blocks predicts Pu with a mean accuracy of 93% and a standard deviation of 12% where the standards EN 1996-1-1 for mortared masonry exhibited a mean accuracy of 137% and a standard deviation of about 29%. Concerning the improved DSM blocks, the proposed model predicts Pu with a mean accuracy of 106% and a standard deviation of 10%, whereas the standards EN 1996-1-1 presents a mean accuracy of 124% and a standard deviation of 9%.

Impact of the height imperfections of masonry blocks on the load bearing capacity of dry-stack masonry walls

Dry-stacked masonry walls gives rise to geometric imperfections: the height variation of different masonry blocks ΔH and the roughness of the support area Δh. This paper studies the effect of ΔH on the structural response and the load bearing capacity of masonry walls by highlighting the load percolation. Furthermore, an algorithm was developed to define a stress multiplier coefficient respecting the imperfections ΔH. The algorithm allowed predicting 77% of the amplified stress compared to the FE analysis and showed that the geometric imperfections govern the load percolation in a wall as well as the cracking mode and the bearing capacity.

The Behaviour of Palm Oil Fibre Block Masonry Prism under Eccentric Compressive Loading

Dry-stacked masonry offers great benefits in constructing masonry buildings. Several examples from previous research show that dry masonry is reasonable alternative to the traditional building system. By addition of fibre, the ductility and the propagation of cracking will be improved. This study investigates the dry stack oil palm fibre block prisms which were subjected to eccentricity compression loads. These concrete blocks were cast using a single mould with suitable fibre-cement composition namely 1:4 (cement: sand) and 0.40 water to the cement ratio based on cement weight. Prisms test using 400 (length) × 150 (width) × 510 (height) mm specimen was carried under eccentric load. There were forty eight (48) prisms built with different configurations based on their volume of fibre. In this study, one types of grout were used namely the fine grout of mix 1:3:2 (cement: sand: aggregate (5mm maximum). Based on the test performed, the failure mechanism and influencing parameters were discussed. From compressive strength test result, it shows that the strength of concrete block decreased with the increase of fibre used. Although the control sample has the higher strength compared to concrete with EFB, it can be seen from mode failure of masonry prism that fibre could extend the cracking time. These results show that the oil palm fibre blocks can improve the failure behaviour and suitable to be used as load bearing wall construction in Malaysia.

Performance of an 11 m high block-faced geogrid wall designed using the K-stiffness method

An 11 m high dry-stacked masonry concrete block wall reinforced with a high-density polyethylene (HDPE) geogrid was designed, instrumented, and monitored for a period of 2 years as part of a highway-widening project southeast of Seattle, Washington, in the USA. An extensive materials-testing program was conducted to characterize the geogrid and backfill soil properties. The empirical-based K-stiffness method was used to design the wall, and this approach resulted in a 35% reduction in total required reinforcement strength compared with the American Association of State Highway and Transportation Officials / Federal Highway Administration (AASHTO/FHWA) simplified method. The cost savings more than compensated for the cost of the instrumentation program. Geogrid strains were measured using strain gauges and extensometers, and the walls were surveyed to monitor facing deformations. The stiffness of the geogrid materials was computed from the results of laboratory in-isolation constant-load (creep) tests. The time- and strain-dependent stiffness values, in combination with measured strains, were used to compute measured reinforcement loads at the reinforcement connections and at locations within the reinforced soil backfill. The measured loads were compared with class A, B, and C1 predictions using the AASHTO/FHWA simplified and K-stiffness methods. These comparisons demonstrate that the simplified method significantly overestimated reinforcement loads, whereas the K-stiffness method provided estimates that were judged to be in better agreement with the measured results. The paper also quantifies the influence of construction procedures on reinforcement strains and load, shows that long-term creep of the reinforcement after 2 years after construction is negligible, and identifies lessons learned.

Influence of Construction Method on Water Permeation of Interlocking Block Masonry

This technical note discusses water penetration resistance studies on a solid interlocking block masonry system, adopting ASTM E 514-90 for the influence of the type of bedding (dry stacking, thin jointing, and mortar), surface finishes (stucco and plaster on one side or both sides), and simulated wind velocities (0, 50, and 100 km/h). Silblock masonry without a surface finish is suitable for rain protected and interior walls. Introduction of any form of mortar bedding (thin jointing or conventional) resulted in higher dampness than the dry-stacked specimens. With respect to dampness, plastered dry-stacked masonry performs better, whereas with respect to leakage, plastered thin-jointed masonry performs better.