Hollow Concrete Block Research Articles

New techniques for the energy saving of sustainable buildings by using phase change materials

Efficiency and energy system improvement are among the main important modern studies centered the energy consumption reduction and thermal performance enhancement of buildings. The main objective of this study is saving the energy of sustainable buildings by using paraffin wax as phase change materials (PCMs) and pumice fine aggregates (PUs) with concrete hollow blocks (CHBs) by using the cement mortars into the walls and ceilings (CILs). The effects investigated on temperature reduction and their role is improving thermal performance, thermal comfort, and electrical consumption energy savings of buildings. Eight concrete hollow blocks CHBs specimens were prepared using the cement mortars. The first group consists of four specimens included CHBs (Standard; without mortar) and the other three mixtures with different percentages of PCMs (0%, 50%, and 75%) by volume of sand. The second group was prepared using PUs aggregate that consists of three CHBs specimens with different percentages of PCMs (0%, 50%, and 75%) by volume of PUs, that prepared to investigate the effects of PUs aggregate and PCMs replacement on the thermal properties. The eighth CHBs specimen was filled with pure PCMs. The thermal properties of the prepared specimens were performed by Differential Scanning Calorimetry (DSC), thermal Conductivity (K- Value), and heat transfer evolution (HTE) analysis technique. Four rooms were built with a 6 cm ceiling thickness and CHBs walls, to study the effect of PCMs and PUs on the thermal properties. The temperature evolution in the rooms and the offset peak hours, cooling load, and energy cost savings were investigated. Results indicate improving the thermal properties of the tested specimens. The room results show a decrease in the indoor temperature of the room with 5.75 °C. The cooling load reduction was 26%, corresponding to an electricity consumption savings of approximately $2.76/Day m3. Based on all results, thermal performance tests showed that the modal room with the PCMs + PUs can be improved thermal comfort keeping the indoor temperature at the comfortable range for a large time and reduced the electrical consumption energy of buildings.

A microwave system for measuring moisture of hollow concrete blocks

In this paper, the authors aim to present a microwave system for measuring moisture of hollow concrete blocks. The idea is to use this system as a new technique for Structural Health Monitoring (SHM). The hollow concrete block is an element widely used in civil construction. For that, five samples of blocks were selected and analyzed. Next, antennas and a frequency selective surface (FSS) that is used as a sensor element were designed to measure the frequency responses for various moisture levels of concrete blocks combined with the FSS. The results show a high level of correlation between the frequency variation and the relative humidity level (r=−0.98). The numerical treatment and the statistical analysis of the results were fundamental to determine a first-order function that met the dynamics of the resonance frequency and the relative humidity. Linear regression is performed that results in R2=0.96, being statistically proven that the defined function meets the proposed study within the range of 10 to 90% relative humidity, as well as a specific methodology for this type of study, is established.

Thermal performance of lightweight concrete applications in building envelopes in Lebanon

Innovative building materials are being used in building envelopes for reducing their heating and cooling needs. This paper aims to assess the thermal impact of using lightweight concrete in Lebanese building constructions by pouring an 8 cm thickness of lightweight concrete on the roof and the slab and replacing traditional hollow concrete block by lightweight concrete blocks. Thermal properties of two different samples were experimentally determined: the first one (558 kg/m3) used for the roof and the slab and the second one (1074 kg/m3) used for the walls. Then numerical simulations were carried out for a Lebanese traditional detached house using the characteristics of these two samples. The thermally improved Light Weight Concrete building (LWC) was compared to a traditional Lebanese house base case (BC) using a dynamic building energy simulation tool in the four different Lebanese climate zones: coastal, mid-mountain, mountain, and inland zones. The results highlight the effectiveness of integrating LWC to building envelopes by reducing energy consumption and improving thermal comfort in both winter and summer climate conditions and in the different Lebanese climatic zones. The paper demonstrates that the use of LWC in the vertical walls replacing the traditional hollow blocks can reduce the heating needs by up to 9% and by up to 13% for cooling needs. On the other hand, adding a LWC roof screed has a very high impact on cooling and heating energy consumption, which can reach up to 74% in cooling energy savings and up to 24% in heating energy savings.

Thermal performance of alternative binders lime hemp concrete (LHC) building: comparison with conventional building materials

ABSTRACT This research aims to estimate the operational energy (OE) savings of a full-scale building, made of lime hemp concrete (LHC) with alternative binders partly replacing lime, compared to buildings made of conventional materials, e.g. Autoclaved Aerated Concrete (AAC), Hollow Concrete Blocks (HCB), and Expanded Polystyrene (ESP). The thermal performance of small size (1 m × 1 m) different materials test cells was experimentally studied. Experimental results were compared to simulated values obtained by EnergyPlus. Monitored and simulated indoor temperatures were found to be in good agreement. Subsequently, the thermal performance and energy consumption of full-scale buildings (10 m × 10 m × 2.9 m) were simulated by EnergyPlus with a great degree of confidence. In up-scaled building simulations, LHC presented the best thermal performance and consequently the lowest energy consumption, reaching ∼7 kWh/m2/year, nearly Zero Energy Building standards, 90% lower as compared to HCB which obtained the highest energy consumption. Dynamic external window shading was shown to have a significant impact on cooling energy savings. This research clearly shows the high potential of using LHC with alternative binders as a partial replacement for lime, as it has advantages in terms of energy savings, and their equivalent CO2 emissions.

Utilization of Jebel Marra Volcanic Ash as Low Cost Material in Concrete Hollow Blocks in Darfur, Sudan

Concrete hollow blocks (CHB) have an important place in modern building industry, and although the CHB is considered a better alternative to fired bricks from the ecological and economical points of view, however, its prices are still high, since the main cost-factor is the ordinary Portland cement (OPC). This study is mainly focusing on the utilization of volcanic ash (VA) from Jebel Marra as a low cost material for CHB. In this study a VA sample from Jebel Marra (Al-malam area) was investigated for its physical and chemical properties, different substitution levels of 10, 20, 30, 40, and 50% of the OPC with pozzolanas were tested. Combined aggregates of locally available sand and stone aggregates were also tested for their economical value of fineness modulus. Then the potential use of these materials was implemented in (CHB) with different blends and mix ratios. The results of the chemical and physical analysis of the VA showed their compliance to the international specifications. The strength activity index of the mix containing 20%VA of the OPC weight at 28 days was 87%. If consider 3.5 MPa as the minimum compressive strength of load bearing CHB required by the Indian standard, it can be concluded that the VA can be used successfully as low cost material in the CHB with the substitution level up to 40%, 30%, and 20%, for binder aggregates ratio by volume 1:6, 1:7, and 1:8, respectively, with subsequent reduction in binder cost by 34, 26, and 17%, In addition, increasing the compressive strength of blocks can be achieved by using high pressure blocks making machine.

Simplified micro-modeling of partially-grouted reinforced masonry shear walls with bed-joint reinforcement: Implementation and validation

Partially grouted reinforced masonry (PG-RM) shear walls of hollow concrete blocks (HCB) have been an object of study during the last years. The non-constant cross-section of this type of structural element and the presence of reinforcement set a challenging scenario when assessing their lateral resistance. This scenario makes simple approaches (e.g., design expressions) lacking accuracy. Besides, the most accurate existent analysis methodologies rely on user-defined sub-routines that are not available for commercial use. Therefore, proper analysis methodologies are still a need. In this regard, this research aims at reproducing the behavior of PG-RM shear walls with bed-joint reinforcement with a simple but also accurate approach. In this line, the in-plane behavior of PG-RM shear walls was reproduced by implementing 2D micro-models in a multi-purpose commercial FE code without requiring excessive work, advanced programming skills, and unaffordable hardware. The model approach was validated by reproducing two identical full-scale PG-RM shear walls. Although the model was not able to reproduce cyclic loading as in the tests, the model captured the experimental failure mode and lateral resistance with an acceptable degree of accuracy. Moreover, the distribution of cracks and deformations in horizontal reinforcement elements were appropriately reproduced at the lateral resistance, indicating the most demanded reinforcement portions. Additionally, the proposed modeling approach was compared with two alternative approaches: a 2D model that reproduced tensile failure employing interfaces and a smeared crack model and a 3D model that reproduced tensile failure utilizing a smeared crack model. The benchmark results pointed out the advantages of the reference model over the alternative modeling approaches. The first alternative model reproduced an excessive displacement capacity, and the second alternative model simulated an inaccurate crack pattern and was associated with a heavy computational burden.

A micro–macro modelling methodology for the analysis of infilled frames

A macro-modelling approach is proposed for representing the masonry infill walls in a non-linear analysis of infilled frame structures. The infill wall is modelled by equivalent struts. The paper presents a combination of an experimental testing method and analytical method to determine the constitutive law of the equivalent struts model. Thus, the model is based on the physical behaviour of the infill wall, rather than on empirical values that came from experimental or numerical tests of infilled frames. Upon requirement, the model can be developed to horizontal or vertical distortion of the infill wall. The strut model was incorporated in a detailed, micro non-linear two-dimensional finite element analysis and validated against reinforced concrete frames infilled by hollow concrete blocks and autoclaved aerated concrete blocks subjected to loss of supporting column scenario. The validation procedure showed that the model captures not only the stiffness and the resistance of a reinforced concrete infilled frame but also the failure mode and the pattern of cracking of the frame.

Sound insulation of a hollow concrete blocks wall made with construction and demolition waste and wood-based panels as linings

It is a well-discussed topic that Construction and Demolition Waste (CDW) can be recycled and used as aggregate in the construction sector. Generally, Brazilian construction techniques are based on hollow blocks or bricks and mortars as coating systems. This paper describes the sound insulation of a masonry wall built with hollow concrete blocks and CDW as aggregates. The measurements were performed according to the reverberant chamber method. Keeping sustainability in mind instead of applying cement mortar as coating system, Oriented Strand Boards (OSB) and Wood-Wool Cement Boards (WWCB) were used and also tested as acoustical linings. The panels were directly attached on the wall with nails in the receiving room. All types of panels increased the weighted sound reduction index ([Formula: see text]). Wood-based composites can also improve the air quality because of their hygroscopic properties. In summary, sustainable wall systems were characterized according to their sound insulation properties, presented as possible substitutes for traditional masonry walls.

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.

Mechanical Properties of a New Type Recycled Aggregate Concrete Interlocking Hollow Block Masonry

Considering the advantages of energy conservation and reducing the construction skill requirement of the workers, a new type of interlocking hollow block using recycled aggregates concrete (IHB-RAC) with the compressive strength up to 10 Mpa was proposed, which could help improve more than 56% of the construction efficiency compared to commonly used concrete hollow blocks. In order to study the mechanical properties and promote the application of this new type block in building engineering, the masonries considering different strengths of mortar and the concrete used in the grouting holes were designed, and the corresponding compressive and shear strength, as well as the failure mode of the masonries were studied according to the test results. Then, experimental results were compared with the calculated values obtained from Chinese code GB50003-2011 to check the suitability of the standards. In order to make an accurate prediction of the compressive strength of the masonry, modifying coefficients were suggested considering the positive contributions of the connecting keys. In addition, according to the test results, an appropriate calculation method for accurately predicting the shear strength of the grouted IHB-RAC masonry was proposed by separately considering the effort of the mortar and the grouting hole concrete.

Shearing of infill masonry walls under lateral and vertical loading

The paper presents an experimental investigation on the behavior of two identical large-scale masonry infill walls subjected to different shearing deformations resulting from lateral or vertical loading. The former produces a horizontal displacement field that simulates the behavior of the wall under earthquake excitation. The latter produces a vertical displacement field that simulates the case followed by loss of gravity support. Both scenarios were identified in past earthquakes. The experiments were conducted on similar infill walls with an aspect ratio of 1:1 made of hollow concrete blocks. The tests show fundamentally different behaviors in terms of the cracking patterns and load-bearing mechanisms. The orthotropic properties of the masonry infill wall significantly affect the load-displacement behavior, including the load resistance mechanism, the stiffness, and the unloading behavior. The major differences between the two cases call for caution in simulating the behaviour of infilled frame structures in the case of loss of a supporting column based on the accumulated knowledge on the behavior under lateral loading.

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.

Implementation and evaluation of the underwater crack repair in the hollow concrete block of the gravity wharf

Concrete block quay wall is the most popular type of structures in the gravity wharf. The concrete block can be generally categorized into two types: solid and hollow concrete blocks. Compared to the solid concrete block, the hollow concrete block can reduce the usage of concrete significantly and increase the resistance to sliding and overturning. This paper studied the application of hollow concrete blocks in the gravity wharf of Qingdao Port. It was discovered that in the application, the main problem was the crack development in the hollow concrete blocks. The paper first analysed the reason of crack development in the structure by conducting laboratory model tests. It was found that the contact conditions between two hollow concrete blocks was the key of the crack development. In order to improve the performance of the structure of hollow concrete blocks, an effective scheme, which can repair the cracks in the underwater environment and increase the bearing capacity of the gravity wharf, is proposed. The scheme contains two main procedures. The first step is to use the invented mending material to fill up the cracks. The next is to use the grouting technique to bond the rockfill inside the block holes and the hollow concrete blocks together. The model tests, field tests in 1980s and 2010 have proved the effectiveness of the scheme. This paper provides reference for the construction of similar structures.

Production of Hollow Block Using Waste Plastic and Sand

In building construction, hollow concrete block (HCB) is a versatile material used in the construction industry, consisting of a mixture of cement, sand, and optionally fine aggregates with water. The cost of these materials, which make up the concrete block, is expensive. So we should use a renewable natural resource that causes negative impacts on the environment. Plastics are one of the materials present in our everyday lives, which have many chemical and hazardous substances that affect human health and the surrounding environment. This study aims to produce hollow blocks using waste plastic material in the ratio of 1:2, 1:3, 1:4, and 1:5 of hollow block size 40cm X 20cm X 10cm of different Polyethylene Terephthalate (PET) and High-Density Polyethylene (HDPE) waste plastic and sand content. This research discussed the material used, the methodology was followed, and the production of hollow blocks and Quality control test of prepared material samples compared with the standard material specification. In this research work, many characteristics that have relevance to the production of Hollow blocks were considered. The plastic is shredded, washed, dried, and melted within the range of 257-315°C temperature in open-air. After melting of PET and HDPE into liquid-state, fixing the sand materials' proportion, mixing the sand materials fed into the mold, and testing the samples after 48 hours was conducted. The test results notice that properties of two samples produced from hollow block satisfy the class-B based on Ethiopian Building Code Standard requirements. The test result for the 1:2 ratio having 3.87Mpa. Therefore, the hollow block production has high compressive strength and low water absorption, which fulfills the standard requirement comparing with the surface property of HCB and aesthetics. The rough surface of HB creates bondage with mortar, which is easier for plastering purpose.

Humidity and specimen preparation procedure: influence on compressive strength of concrete blocks

abstract: It is extremely important that the quality control of the concrete block used in structural masonry is conducted based on standard procedures that allow reliable estimation of the properties of these components. This work aims to analyze and evaluate the influence of the concrete block moisture on the result of the compression test. Hollow concrete blocks were prepared and subsequently maintained in different environments for various periods of time and under different conditions of temperature and humidity to determine the influence of the type of drying on the relative humidity of the block at the time of testing and consequently on its compressive strength. As a conclusion, it can be stated that, because it is necessary to use water in the process, the grinding rectification of the faces of the blocks led them to have high humidity, above 70%. If tested in this condition, the results of the compressive strength tests will be lower than that of blocks under usual environmental conditions. No differences were found in the average block strength when they were kept dry in the controlled environment of the laboratory during periods of 24 or 48 h. After grinding, it is not necessary to dry the blocks inside an oven at 40ºC before the tests; simply leaving them at a usual room temperature of 23ºC and humidity of 40 ± 5% for 24h is sufficient. The attempt to accelerate drying in an oven at 100ºC is not adequate because this leads to an increase in the compressive strength. From the results, it was possible to determine expressions to correlate the compressive strength as a function of the moisture of the block at the time of the test. The best-fit expressions are distinct for each block type, but the formulations are consistent in indicating a considerable difference in resistance as a function of moisture.

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.

Experimental investigation on structural concrete masonry in fire: emphasis on the thermal behavior and residual strength

abstract: This paper aims to analyze the thermal behavior and residual mechanical properties of concrete hollow-blocks structural masonry and its component materials in fire situation using experimental investigation. Compression tests were carried out on blocks, prisms and small walls at room temperature and after being exposed for 70 minutes to the ISO 834 Standard Fire. The test at high temperatures was run using a furnace powered by natural gas and instrumented with thermocouples to measure temperatures in the specimens. The influence of the initial concrete strength on masonry behavior was evaluated considering the use of blocks with different strengths at room temperature. In addition, exposure to fire was also investigated considering masonry elements with no coverings and submitted to two different fire exposure conditions: one or both sides. The results indicate a substantial loss in the masonry load capacity at high temperatures, especially in cases of fire exposure on both sides, where the residual compressive strength resulted, on average, between 20% and 27% for the blocks and approximately 14% for prisms and small walls. Its performance with fire heating up on only one face is much higher, with an average residual masonry strength equal to 46% compared to its strength at room temperature. The obtained results are also useful for evaluating masonry regarding the integrity and thermal insulation criteria, the latter achieved with little over 60 minutes of testing.

Optimizing thermal insulation of external building walls in different climate zones in Libya

An efficient way to reduce the energy required for conditioning buildings and therefore to reduce CO2 emission is the use of proper thermal insulation in buildings’ external walls. This measure requires data from metrological stations that can be used in the optimization of the thermal insulation. The main objectives of this study are to construct thermal climatic zones for Libya and to specify the optimum insulation thickness for external walls for the different zones. This work is comprehensive as the metrological data from all existing 33 weather stations has been collected and used for identifying thermal zones. For the optimization of the construction of external walls, the most commonly used local wall structures are investigated: hollow concrete block, limestone block and hollow brick. In addition, four thermal insulation materials: extruded polystyrene, expanded polystyrene, rock wool and foamed polyurethane are used with every wall type. Optimum insulation thickness, energy savings, energy cost and payback periods were estimated for the 33 locations using life cycle cost analysis. A map is constructed for the thermal zones based on degree-day values for the entire country. The results show that limestone blocks with expanded polystyrene insulation form the optimum wall construction as it provides the minimum total cost for all locations. Depending on the Degree-day values, the optimum insulation thickness varies between 5.4 and 15.3 cm across the country with energy saving varies between 28 and 178 $/m2. Using the optimum thickness, the average CO2 emissions can potentially be reduced by about 85%. Finally, a contour map represents the optimum thickness of expanded polystyrene is presented in this work.