Strength Of Concrete Blocks Research Articles

Experimental Characterization of the Initial Shear Strength of Composite Masonry including AAC Blocks and DPC Layers

Modern masonry structures, apart from having a load-bearing function, are more and more subjected to additional non-structural requirements related to, e.g., thermal insulation and moisture control. This has respectively led to the introduction of thermal break layers, in practice often executed using autoclaved aerated concrete (AAC) blocks, and damp proof courses (DPC) in masonry walls. These modifications have an impact on the mechanical characteristics of the masonry, such as the shear strength. In this paper, an extensive experimental campaign is therefore conducted on masonry triplets to investigate the initial shear strength of concrete block and clay brick masonry, including AAC blocks. The impact of the the presence of a polyethylene DPC layer is also studied. Moreover, the position of the DPC membrane is varied, i.e., directly on top of the brick (which is generally not recommended yet common in construction practice) and in the middle of the mortar joint. In total, 138 shear tests were performed according to the EN 1052-3 standard, with low to moderate precompression levels. The test results focus on the differences in friction angle, shear modulus, and friction coefficient. It is concluded that the presence of an AAC block decreases the initial shear strength to a value which is lower than the one assumed by Eurocode 6. Moreover, when adding a DPC membrane, the shear strength is reduced even further to almost zero, in particular when the membrane is not put in the middle of the mortar joint.

Analyzing the Strength of Concrete Blocks Reinforced by Half Portion of Coconut Shell

Concrete is the premier construction material around the world and is most widely used in all types of construction works, including infrastructure, low and high-rise buildings, and domestic developments. It is a man-made product, essentially consisting of a mixture of cement, aggregates, water and admixture(s). Inert granular materials such as sand, crushed stone or gravel form the major part of the aggregates. Traditionally aggregates have been readily available at economic prices and of qualities to suit all purposes. But the continued extensive extraction use of aggregates from natural resources has been questioned because of the depletion of quality primary aggregates and greater awareness of environmental protection. In light of this, the non-availability of natural resources to future generations has also been realized. Different alternative waste materials and industrial by products such as fly ash, bottom ash, recycled aggregates, foundry sand, China clay sand, crumb rubber, glass were replaced with natural aggregate and investigated properties of the concretes. Apart from above mentioned waste materials and industrial by products, few studies identified that coconut shells, the agricultural by product can also be used as aggregate in concrete. According to a report, coconut is grown in more than 86 countries worldwide, with a total production of 54 billion nuts per annum. India occupies the premier position in the world with an annual production of 13 billion nuts, followed by Indonesia and the Philippines.

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.

Analysis of The Mechanical Properties of Concrete Beams That Use Pumice as a Partial Substitution of Concrete Mixtures

One of the most common inhibiting factors in the archipelago is the lack of availability of material resources and human resources. One of the options is the use of lightweight concrete precast using materials around the islands. The local material which is widely distributed in North Maluku is pumice but it has not been used maximally because so far it has only been used as pile material. This study aims to analyze the effect of partial substitution of pumice on fine aggregate in a concrete mixture. This research was carried out experimentally in a laboratory using UTM and divided into 2 stages. Stage 1, designing and analyzing concrete mix using pumice compared without using pumice, Phase 2 testing using concrete beam dimensions of 600x150x100 mm with an inter load of 150 mm. Beam test results show that the limited use of pumice in a concrete mixture does not greatly affect the strength of normal concrete beams, as indicated by the deflection value and strength of concrete blocks that are almost as large.

FBG testing on inside strain capturing of concrete blocks subjected to hard projectiles penetration

This study evaluates the terminal ballistics and strain behaviors of normal strength concrete blocks penetrated by hard ogival-nosed projectiles. Fiber Bragg Gratings (FBG) sensors are utilized herein to measure the radial strain responses inside concrete target during penetration process. With precise location, a novel method of FBG sensors embedment inside concrete block is proposed. The penetration tests are conducted with ballistic gun whereby the FBG sensor reflected signals are recorded. Consequently, Holmquist–Johnson–Cook (HJC) model is used to describe the concrete material dynamic behaviors. The LS-Dyna numerical penetration model is validated by Depth of Penetration (DOP) prediction. The numerical radial strain inside concrete target matches well with the experimental data by FGB testing.

Reuse of construction and demolished concrete waste by producing affordable high strength concrete block

The issue of achieving sustainable environment is highlighted in different national and international strategic documents, such as Rwanda Viosion 2020, EDPRS II and MDGs. Rwanda on its track towards achieving sustainable environment, is still experiencing some challenges like Environmental degradation for the search of aggregates, energy for extraction of natural aggregates and difficulties in finding dumping sites for demolitions and construction wastes. Therefore, all those problems have created the need for developing a new source of construction materials.The idea of recycling of C&D concrete wastes aims at finding solution to the environment degradation caused by damped demolished wastes as well as producing affordable high strength concrete blocks. This research investigated the availability of C&D concrete wastes and it was discovered that up to 33.33% of C&D waste came from concrete structures while more than 23.75% of people confirmed to have been involved in demolition works more than three times a year.The research was done by collecting sample composed of C&D concrete wastes at construction site of BPR headquarter where they demolished the existed building for construction of a new multistory building in kigali city and the sample was crushed, batched and mixed with a proportion of 1:3 and 1:5 as stated by Rwanda Bureau of Standards and manufactured new concrete blocks. The research performed on series of concrete blocks: 2 series each made of different proportions of cement for recycled concrete blocks, and one serie of reference blocks made of natural aggregates. Compressive strength test gave an average of 5.13N/mm2 for recycled concrete block, which fulfills requirement of Rwanda Bureau of standards for hollow concrete blocks and which is 0.87 times the compressive strength of an ordinary block tested under same conditions. Finally, the cost effectiveness showed that the new recycled concrete block will be affordable by reducing at 15.6% of cost for that one made of natural aggregates.Keywords: Concrete wastes, Recycled concrete block, Mechanical properties, Cost effectiveness and Environmental protection

Double lap shear test on steel fabric reinforced cementitious matrix (SFRCM)

The present work deals with the experimental characterization of the mechanical bond behaviour of a galvanized steel fabric reinforced cementitious matrix (SFRCM) laminated on concrete support. The specimens, made of two low strength concrete blocks connected with a galvanized steel fabric embedded in a geo-polymeric mortar layer, have been tested according to double lap test (DLT) set-up. Six different groups of specimens have been tested varying both the lamination length and the steel fabric density. In order to reproduce the load-slip or bond-slip curves, a tri-linear bond slip model together with its parameters identification has been proposed.For some specimens, the slip profile and the slip distribution have been analysed and split into the substrate laminate slip and inner laminate layers slip. This distinction has been used as a measure of the fabric-matrix compatibility. In addition, the effect induced by the rigid blocks rotation occurred during the DLT has been argued. The DIC optical system monitoring has been used to asses both the force-slip distribution and the crack opening displacement (COD).

The Utilisation of Shredded PET as Aggregate Replacement for Interlocking Concrete Block

The consumption of plastic has grown substantially all over the world in recent years and this has created huge quantities of plastic-based waste. Plastic waste is now a serious environmental threat to the modern way of living, although steps were taken to reduce its consumption. This creates substantial garbage every day, which is much unhealthy. Plastic bottles such as Polyethylene terephthalate (PET) was use as the partially component in this making of interlocking blocks concrete. This project investigates the strength and workability of the interlocking block concrete by replacing course aggregate with % PET. The suitability of recycled plastics (PET) as course aggregate in interlocking block concrete and its advantages are discussed here. Moreover, there were more benefits when using interlocking block than using conventional block such as it easy for construction because they are aligning, easy to place, high speed stacking and they offer more resistance to shear and buildings would be even stronger. Based on the test perform, the failure parameter were discussed .From the compressive strength test result, it shows that the strength of concrete block decreased with increased of PET used. From the results, it shows that higher compressive strength was found with 5% natural course aggregate replaced with PET compared to other percentages.

Compressive strength of masonry constructed with high strength concrete blocks

Abstract Although the use of high strength concrete blocks for the construction of tall buildings is becoming common in Brazil, their mechanical properties and behavior are not fully understood. The literature shows a gap in experimental studies with the use of high strength concrete blocks, i.e., those with compressive strength greater than 16 MPa. The work presented herein was conducted in order to study the behavior of high strength structural masonry. Therefore, the compressive strength and modulus of elasticity of concrete block walls tested under axial load were assessed. The specimens included grouted and ungrouted walls and walls with a mid-height bond beam; ungrouted walls were constructed with face-shell and full mortar bedding. The walls were built and tested in the laboratory of CESP and in the Structures Laboratory of the UNESP Civil Engineering Department in Ilha Solteira (NEPAE). Concrete blocks with nominal compressive strength of 16 (B1), 24 (B2) and 30 (B3) MPa were used. Ungrouted masonry walls had a height of 220 cm and a width of 120 cm while grouted masonry walls had a height of 220 cm and a width of 80 cm. Traditional Portland cement, sand and lime mortar was used. The testing program included 36 blocks, 18 prisms, 9 ungrouted walls (6 with face-shell mortar bedding and 3 with full mortar bedding), 9 grouted masonry walls, and 12 ungrouted walls with a bond beam at mid-height. The experimental results were used to determine the compressive strength ratio between masonry units, prisms and masonry walls. The analyses included assessing the cracking pattern, the mode of failure and the stress-strain curve of the masonry walls. Tests results indicate that the prism-to-unit strength ratio varies according to the block strength; that face-shell mortar bedding is suitable for high strength concrete masonry; and that 20% resistance decrease for face-shell mortar bedding when compared with full mortar bedding is a conservative consideration. The results also show that using a bond beam at the mid-height of the wall does not lead to a compressive strength decreased but it changes the failure mode and the shape of the stress-strain curve. In addition, the results show that estimating E = 800 fp is conservative for ungrouted masonry walls but reasonably accurate for grouted masonry walls and that there is no reason to limit the value of E to a maximum value of 16 GPa. Furthermore, the results show that, for design purposes, a wall-to-prism strength ratio value of 0.7 may be used for high strength concrete masonry.

Experimental study on bond behavior between corrosion-cracked reinforced concrete and CFRP sheets

Bond behavior between corrosion damaged reinforced concrete and carbon fiber reinforced concrete polymer (CFRP) sheets was experimentally investigated. Forty ordinary strength concrete blocks (150 × 150 × 200 mm) were reinforced at one side across the 200-mm-dimension using three conventional ϕ12 mm steel bars at a spacing of (30, 40, and 50 mm) at a concrete clear cover of 15 mm. Thirty blocks were subjected to a cyclic treatment in 3% chloride solution until corrosion initiated and resulted in three different global cracking widths of up to 0.90 mm. Both control and corrosion damaged blocks were attached to CFRP sheets over their steel reinforced zone at bond lengths and widths ranging from (90 to 150 mm) and (50 to 150 mm), respectively, with CFRP bond length-to-bar spacing ratio kept constant at 1/3. Near-end pull-off tests were carried out using a special setup, mounted on a Universal Testing machine. Corrosion cracking caused significant reductions in bond strength, and slippage at ultimate stress at (41 and 68%), respectively. Other bond characteristics such as stress at first slippage, and bond stiffness and toughness were reduced, as well, by as high as (83, 44 and 67%) of those of control specimens, respectively. Corrosion cracks were more detrimental for smaller bond length and width values; especially after first and second corrosion stages, where bond failure was categorized by concrete skin peeling-off.

Numerical and experimental evaluation of masonry prisms by finite element method

Abstract This work developed experimental tests and numerical models able to represent the mechanical behavior of prisms made of ordinary and high strength concrete blocks. Experimental tests of prisms were performed and a detailed micro-modeling strategy was adopted for numerical analysis. In this modeling technique, each material (block and mortar) was represented by its own mechanical properties. The validation of numerical models was based on experimental results. It was found that the obtained numerical values of compressive strength and modulus of elasticity differ by 5% from the experimentally observed values. Moreover, mechanisms responsible for the rupture of the prisms were evaluated and compared to the behaviors observed in the tests and those described in the literature. Through experimental results it is possible to conclude that the numerical models have been able to represent both the mechanical properties and the mechanisms responsible for failure.

Influência do tipo de argamassa e suas propriedades do estado fresco nas propriedades mecânicas de alvenarias estruturais de blocos de concreto para edifícios altos

RESUMO O uso da alvenaria estrutural de blocos de concreto na construção de edifícios altos tem aumentado nos últimos anos em função da economia e racionalização que proporciona aos empreendimentos. Nessa busca pela otimização dos processos, o emprego de novos materiais, como as argamassas industrializadas, tem aumentado significativamente. Essas argamassas geralmente possuem aditivos na sua constituição, e apresentam vantagens de utilização, pois reduzem a responsabilidade de dosagem em obra, facilitam a gestão do canteiro e agilizam o processo de mistura e aplicação. Entretanto, em função da presença de aditivos, estudos indicam que essas argamassas, quando usadas para assentamento de blocos para alvenaria estrutural de resistências elevadas, podem não apresentar aderência adequada ao bloco, além de diminuir drasticamente o fator de eficiência e mudar o mecanismo de ruptura da alvenaria, que passa a ser por esmagamento da junta. Diante disso, foi estudado o desempenho de argamassas industrializadas ofertadas no mercado bem como traços de argamassas mistas empregados no Brasil para alvenarias estruturais de blocos de concreto de elevada resistência à compressão (16 Mpa), para construção de edifícios altos em alvenaria estrutural. A análise baseou-se na resistência à compressão, aderência e mecanismo de ruptura de prismas. Com base nas propriedades desejadas para argamassas empregadas em alvenaria estrutural de edifícios altos, o estudo concluiu que as argamassas mais comumente utilizadas no Brasil, não possuem a capacidade de gerar alvenarias com desempenho totalmente satisfatório.

Mix Ratio Test and Basic Property Analysis for Autoclaved Aerated Concrete (AAC) Block

Through the mix ratio optimization test, the appropriate autoclaved aerated concrete block may be prepared for the production demand, whose technical indexes could satisfy the requirement of national specification. Furthermore, in the light of the research on the property of autoclaved aerated concrete block for this mix ratio, the strength of concrete block would decrease with the increase of total porosity among the pore diameter from 0.5mm to 1.5mm. The autoclaved aerated concrete block possessed the strong capability of absorbing water, so the volume water absorption rate increased quickly at first and then went down furiously, which could make the shrinkage of autoclaved aerated concrete block augment because of the decrease of its water absorption rate.

Mix Ratio Test and Basic Property Analysis for Autoclaved Aerated Concrete (AAC) Block

Through the mix ratio optimization test, the appropriate autoclaved aerated concrete block may be prepared for the production demand, whose technical indexes could satisfy the requirement of national specification. Furthermore, in the light of the research on the property of autoclaved aerated concrete block for this mix ratio, the strength of concrete block would decrease with the increase of total porosity among the pore diameter from 0.5mm to 1.5mm. The autoclaved aerated concrete block possessed the strong capability of absorbing water, so the volume water absorption rate increased quickly at first and then went down furiously, which could make the shrinkage of autoclaved aerated concrete block augment because of the decrease of its water absorption rate.

Technology Research on Waterworks Sludge for Ceramsite

On the basis of analysis of the component of the sludge from Lingzhuang waterworks and the technological process was studied which use the sludge for raw material to produce the sludge ceramsite. Through a lot of experiments, the several factors affecting the nature of ceramsite were developed and the technological parameters were confirmed. A performance test of the ceramsite shows that when the optimized temperature is 1130°C~1170 °C, the optimized baking time is 5 min, strength of tube pressure of the ceramsite is 8 MPa, bulk density of it is 1200 kg/m3compressive strength of concrete blocks is 40 MPa. So the products could meet the demand on high strength ceremsite. It is gained that the way of waterworks sludge for ceramsite is feasible and can bring certain economical profits, social profits and environmental profits. The products can be used widely to load bearing structure in construction profession.

Bearing Strength of Concrete Blocks

The problem of end bearing in a post-tensioned concrete beam may be idealized and simplified to the problem of a circular cylindrical or a square prismatic concrete block with a longitudinal cable duct loaded by two circular or square punches applied on the cable duct at both ends. Bearing capacity solutions for the idealized problem were presented recently. Good experimental verifications of the solutions were available for the special case of concrete blocks with eccentricity but without cable duct. No suitable experimental data were available, however, for concrete blocks with both punch eccentricity and cable duct. The purpose of this note is to test specimens with variations of duct diameters and eccentricities with both plain and random wire reinforced concrete. The test results are presented and compared with the theoretical linear elastic and perfectly plastic solutions.

The effect of different test procedures upon the indicated strength of concrete blocks in compression

Synopsis Although the use of loose fibre-board caps with single blocks may increase the variation within a set of results when compared with mortar capping, the amount will depend largely upon the skill and experience of the mortar-capping operative. From an economic viewpoint, the board-capped single block specimen offers several advantages, and the sample size may be adjusted to give the required level of accuracy to the determination of block strength. The relationship between the results of tests on mortar- and board-capped specimens may be calculated, and both forms of test related directly to the performance of concrete block work walls.

砂利混凝土塊試驗成績

砂利混凝土塊試驗成績