Unit Weight Of Concrete Research Articles

Physical-durable performance of concrete incorporating high loss on ignition-fly ash

This study investigates the feasibility of using raw fly ash with a high loss on ignition in concrete. The fly ash-free concrete samples were prepared with different water-to-binder (w/b) ratios of 0.35, 0.40, and 0.45, whereas the fly ash concrete samples were prepared with a constant w/b of 0.40 and with various fly ash contents (10%, 20%, and 30%) as a cement substitution. The physical properties and durability performance of the concretes were evaluated through fresh concrete properties, compressive strength, strength efficiency of cement, ultrasonic pulse velocity, and resistance to sulfate attack. Test results show that the w/b ratio affected the concrete properties significantly. The incorporation of fly ash increased the workability and reduced the unit weight of fresh concrete. In addition, the fly ash concrete samples containing up to 20% fly ash exhibited an improved strength at long-term ages. Further, all of the fly ash concrete samples showed a good durability performance with ultrasonic pulse velocity value of greater than 4100 m/s and a comparable sulfate resistance to the no-fly ash concrete.

Study on Steel Fibre Reinforced Self Compacting Concrete

Self Compacting Concrete (SCC) consists of a higher amount of fine content and admixtures, thus eliminating the time for compaction and labour cost. Micro silica is a by-product of the industrial manufacture of ferrosilicon and metallic silicon that is been made in high-temperature electric arc furnace. The ferrosilicon is drawn from 2000°C furnace, thus after when it cools down, the particles are condensed and are trapped in huge cloth bags. The condensed fume is processed by removing impurities and thus micro silica is being formed. Micro silica, as a waste by-product, being used for land filling, instead it can be used as an additive to concrete. The overall weight of the concrete increases up to 15 percent, thus increasing the unit weight of concrete. In addition, nano silica and steel fibres have been used to improve the strength and durability of concrete. Addition of silica to a concrete mix alters the cement paste structure. The resulting paste contains more of the calcium-silicate hydrates and less of the easily soluble calcium hydroxides. Due to its smaller size particle distribution, they disperse among and separate the cement particles. In the present study, different mix ratio using micro silica, nano silica and steel fibres has been prepared to study the fresh and hardened properties of SCC respectively.

A comparative study on the thermal conductivities and mechanical properties of lightweight concretes

Thermal conductivity of the materials used in buildings is one of the major factors affecting the heat transfer. Higher thermal conductivity of building walls results in higher heat losses, and in order to maintain the same temperature inside a building, energy consumption for heating or cooling increases. To reduce the heat loss, thus decrease the energy usage, materials with lower thermal conductivities should be preferred. Lightweight concretes can be used for this purpose. However, the properties of these concretes may vary depending on the materials used. The main objective of this experimental study is to compare the properties of lightweight concretes produced with different lightweight aggregates. Lightweight concretes in a wide range of unit weights from approximately 300–1800kg/m3 were prepared in the experimental program. Some properties of the concretes containing pumice and expanded polystyrene beads were obtained. Properties of concretes with expanded perlite and autoclaved aerated concrete determined in previous studies are also included in comparisons and discussion. The test results showed that, depending on the amount and type of lightweight aggregate, unit weight of concrete can be reduced and concretes with various physical and mechanical properties of can be achieved. Thermal conductivity was reduced with the use of lightweight aggregates and for all the lightweight concretes considered, a good relationship was obtained between thermal conductivity and unit weight of concrete. Reductions in the compressive strength and modulus of elasticity of concretes have been obtained with decreasing concrete unit weights. The reduction in strength was more for the concrete containing expanded polystyrene beads.Results showed that strong relationships exist between modulus of elasticity and unit weight of concrete. Results showed that strong relationships exist between modulus of elasticity and unit weight of concrete.

Fracture energy and mechanical characteristics of self-compacting concretes including waste bladder tyre

Management of solid wastes is one of the most important environmental problems in the world. Waste tyres are also one of these solid wastes. The growing number of waste tyres that are stocked every year brings problems in respect of human health, environmental pollution, and also causes esthetical problems. The main purpose of this study is to investigate the effect of waste tyre addition on self-compacting concretes’ mechanical characteristics and fracture properties under bending. In this study, waste bladder tyres (RA) mechanically cut in 25, 50 and 75mm lengths were used by volumetric replacement of coarse aggregates in self-compacting concretes (SCC). Unit weight, flow, J-ring, column segregation, water absorption, 28days of compressive strength, ultrasound pulse velocity and fracture energy tests were applied on concretes obtained by replacement of coarse aggregates in 5%, 10% and 15% ratios by volume. Also, Scanning Electronic Microscope (SEM) and Energy Distribution Spectroscopy (EDS) analyses of the samples were examined. In the study, it was determined that RA replacement decreases unit weight of fresh concrete; when RA length ratio increases, it becomes difficult for the concrete to pass through reinforcement openings; in hardened concrete samples dry unit weight decreases; 10% fibre addition increases compressive strength values; after the ultrasonic pulse velocity measurement, the concretes are included in “good” quality concrete classifications. As a conclusion, it was determined that 25mm long 10% rubber aggregate replacement to self-compacting concretes can give optimum results.

Evaluation of physical and mechanical characteristics of siderite concrete to be used as heavy-weight concrete

The objective of this study is to investigate the usability of siderite aggregates mentioned above as a heavy-weight aggregate in the heavy-weight concrete production and their effects on physical properties of the heavy-weight concrete mixture. For this purpose, normal-weight aggregate content was decreased at the rate of 20%, 40%, 60%, 80% and 100% by volume of the concrete mixture prepared and mixtures were prepared by its substitution with siderite aggregate at the same rates. Based on the increase in siderite aggregate in the concrete mixture, a considerable increase in unit weight, compressive strength and tensile strength of concrete was obtained. Plate-shaped concrete specimens obtained from combined normal-weight and heavy-weight aggregates were exposed to radiation with different X-ray source (118 keV, 164 keV) and Co-60 (1250 keV) beam source at Çekmece Nuclear Facility. It is clearly seen that the concrete mixture containing siderite aggregate improved 70% radiation absorption characteristics compared to that of the concrete mixture without siderite aggregate.

Compressive strength behavior of concrete by partial replacement of regular brick with over-burnt brick aggregate

Numerous kinds of coarse aggregates are being used around the world, and most of these coarse aggregates are naturally originated. Due to the gradual diminution of natural resources, modern society is facing a challenge in concrete work which demands a huge amount of coarse aggregate. In Bangladesh, handful brick fields around the country made brick aggregate available as well as economical compared to natural coarse aggregates. Uncontrolled heat in brick kilns produces a good number of over-burnt bricks. Due to the unevenness, those bricks are staked as an idle in brick fields. Those over-burnt brick could be a source of recycled coarse aggregate. This paper highlights on the behavior of concrete, prepared by the partial replacement of regular brick aggregate (RBA) with over-burnt brick aggregate (OBBA) in a range from 0 to 100%. Three different water cement ratios (0.5, 0.55 and 0.6) are considered in this study. Result shows that compressive strength of concrete increases with the increment of OBBA content. For 75% replacement of RBA with OBBA in concrete increases the compressive strength by 33%. Unit weight of concrete decreases with the increment of OBBA content. The lowest achieved unit weight of concrete is 79% of the usual value of unit weight of concrete. The slump test was conducted for each batches of mixing, and the slump values are in between the range of 3.5–9.0 cm. OBBA in concrete could decrease structure’s dead load and increase its strength with a provision of economy.

Effects of Particle Sizes and Cement Pastes on Mechanical Properties of Pervious Concrete

The purpose of this study is to determine the effects of aggregate size as well as the paste volume on unit weight, connected porosity, water permeability coefficient, compressive strength, and flexural strength of pervious concrete. Four aggregate sizes and four filled percentages of voids by cement pastes were selected as variables. Test results show that the unit weight, compressive strength, and flexural strength of pervious concrete increased with an increase of the filled percentage of voids by cement pastes, but decreased the connected porosity and water permeability coefficient. Pervious concrete with aggregate size of 0.24 – 0.4cm and 90% filled percentage of voids by cement pastes had the highest compressive strength of 25 MPa. Meanwhile, the water permeability of this mixture was higher than 0.01 cm/s which can be classified as the pervious concrete according to the Japan Road Association (JRA).

RIを用いたコンクリートの単位容積質量および水分量の非破壊測定方法に関する研究

This paper discusses a measurement method of unit weight and water content of concrete using radio isotope meter. Concrete members with different unit weight were measured them at the age of 7, 28 and 91 days. As a result, it was found the following things. If the unit weight of concrete is high, the measurement accuracy of the unit weight and water content using radio isotope meter is low. Inserting the radio isotope source a sleeve, it can reduce variations in measurements. The drying of concrete read from radio isotope meter. The calibration curve between the unit weight of concrete and the attenuation of radiation was created.

Use of waste plastic aggregation in concrete as a constituent material

The amount of Plastics consumed annually has been growing increasingly in Bangladesh. Consequently, waste plastic recycling has become one of the major challenges in recent times. The present study has selected waste PET, a polymer compound of Polyethylene Terephthalate, to investigate its possible use as plastic aggregate in concrete application. The shredded waste plastic was used in concrete with partial replacement of 5%, 10% and 20% by volume of conventional coarse aggregate. Four types of concrete specimens including one without plastic aggregate, for comparison purpose, were prepared. All the concrete specimens were tested for its different mechanical properties after a curing period of 7, 21 and 28 days. Various physical properties of all aggregates and fresh concrete properties were also tested in the laboratory. The specific gravity of waste plastic aggregate was found 1.4 and the maximum density of concrete containing plastic aggregate was 115 lb/ft3. The density of concrete specimens containing plastic aggregate decreased with the addition of more amount of plastic aggregate. It was found that the concrete specimen containing waste PET at 10% volume showed higher compressive strength and higher modulus of elasticity than other specimens. The splitting tensile strength was about 8-11% of compressive strength. The flexural strength of concrete specimens containing plastic aggregate was lower than that of concrete without plastic aggregate. It was found that the strength of concrete containing PET aggregate falls in the category of lightweight concrete in terms of their strength, specific gravity and density. Thus, the waste PET aggregate could be effectively used to reduce the unit weight of concrete which results in a reduction in the dead weight of a structural concrete. Furthermore, it is concluded that the use of waste PET in concrete provides some advantages such as reduction in the use of conventional aggregate, disposal of wastes, prevention of environmental pollution, and energy saving.Progressive Agriculture 27 (3): 383-391, 2016

Effect of Concrete Types and Construction Joints on Concrete Shear Friction Characteristics

The present study examined the effect of smooth construction joint and concrete unit weight on the shear friction behavior of concrete. From nine push-off test specimens, shear load-relative slip relationships, shear cracking stress, shear friction strength were measured. Test results showed that the shear cracking stress was hardly affected by the configuration of transverse reinforcement or concrete unit weight. The shear friction strength of monolithic normal-weight concrete was approximately three times higher than that of the companion specimens with construction joint. Meanwhile, the heavyweight concrete joints had a similar shear friction strength to normal-weight concrete ones.

Properties of Light Weight Concrete Containing Crumb Rubber Subjected to High Temperature

In this study, the compressive strength, unit weight and chemical structure of light weight concrete (LWC) containing crumb rubber after exposure to high temperature are investigated. The crumb rubber was used as light weight aggregate in place of normal aggregate at the content of 3-15 wt% of LWC. For all mixtures, the water/cement ratio and sand/cement ratio were fixed at 0.5 and 0.2, respectively. The experimental results showed that the unit weight of LWC containing crumb rubber decreased with increasing crumb rubber content. The unit weight and compressive strength values are in range of 1566-1761 kg/m3, 12-29 MPa, respectively. The LWCs containing 3-7 wt% and 15 wt% crumb rubber can meet the requirement of ASTM standards for structural light weight concrete and masonry, respectively. After high temperature exposure, the unit weight loss and compressive strength loss were 25% and 75%, respectively. All specimens still complied with the requirement of ASTM standard for masonry.

Effects of waste PET as coarse aggregate on the fresh and harden properties of concrete

This study investigates the effect of plastic as an alternative coarse aggregate on various fresh and harden properties of concrete. Polyethylene terephthalate (PET), a thermoplastic polymer, is considered as an alternative aggregate and replaced with natural coarse aggregate, such as brick chips. The PET aggregate is obtained by shredding, melting and crushing the collected waste PET bottles. The primary focus of the work is to observe compressive strength and unit weight of PET aggregate concrete (PAC) along with their workability in comparison with the natural aggregate concrete (NAC). With the increase in PET replacement ratio and w/c ratio lower unit weights and compressive strengths are observed for PAC compare to NAC. Compressive strength for 20% PET replaced PAC at 0.42w/c ratio is 30.3MPa which is only 9% less than the NAC. However, PAC has significantly high workability as 1.8cm slump value is observed for 20% PET replaced PAC at 0.42w/c ratio. Therefore, PET replaced concrete with low w/c ratio and high workability can be used for structural concrete member.

콘크리트의 전단마찰내력에 대한 시공줄눈의 영향

To evaluate the shear friction performance of concrete interfaces with construction joint, a total of 18 push-off specimens were tested under direct shear and constant axial compressive forces. The main parameters investigated were concrete unit weight, arrangement type of transverse reinforcement (V-type for perpendicular configuration to the shear plane and X-type for <TEX>$45^{\circ}$</TEX>-degree inclined configuration), and the magnitude of axial compressive stresses. The initial shear cracking stress and the slope at the ascending branch of the shear load-relative slip relationship were independent of the type of transverse reinforcement and concrete unit weight, whereas they tended to increase as the axial compressive stresses increases. The shear friction strength increased in proportion to the summation of the applied axial stresses and shear transfer capacity (<TEX>${\rho}_{vf}f_y$</TEX>) of transverse reinforcement. The X-type transverse reinforcement had higher shear transfer capacity than the V-type reinforcement. From the mechanical model derived using the upper bound theorem of concrete plasticity, the concrete cohesion and coefficient of friction at the interfaces with construction joint could be estimated to be 1.56 MPa and <TEX>$36.3^{\circ}$</TEX>, respectively.

Properties of Heavyweight Concrete for Structural and Radiation Shielding Purposes

In applications of concrete for shielding against hazardous radiation or for being used as counterweight, as well as in various other applications that involve the use of heavyweight concrete, the most significant method of mix design involves the use of heavyweight aggregates. Concrete mixes that were produced for this work contained iron ore, steel mill scale, two types of barite, and steel slag, which are the heavyweight aggregates available in Turkey. An additional heavyweight concrete mixture was also produced using magnetite as a natural mineral heavyweight aggregate. In all concrete mixes produced, water/cement ratio, cement content, and the maximum aggregate size of the aggregates used were kept constant. In terms of the main mechanical properties, the best performances were obtained when iron ore was used, while the highest fracture energy values were reached in concretes with steel mill scale, magnetite, or with the combination of steel slag, iron ore, and crushed sand. Another important objective of this research was to evaluate the radiation shielding properties of heavyweight concretes containing iron ore, steel mill scale, two types of barite, or steel slag as aggregates. The experimental results showed that the attenuation coefficient varied from 0.224 to 0.265 1/cm, while the unit weight of heavyweight concrete was increased from 3012 to 3820 kg/m3. On the other hand, there is reasonably good agreement between theoretical and experimental results of linear attenuation coefficients. It can be concluded that the dominant factor in the determination of attenuation coefficient is the unit weight of heavyweight concrete and that the value of the coefficient is independent of the type of heavyweight aggregate used.

Properties of Concrete made with Waste Clay Brick as Sand Incorporating Nano SiO2

The present study aims to investigate the use of clay bricks in concrete preparation. In the first phase of the study, the clay bricks as waste materials from building remains were collected and ground by jaw mills and finally graded in the range of standard sand. The first experiments like XRF, water absorption, and unit weight were then carried out on the materials. After that, some samples with substitution percents of zero to one hundred from waste bricks as sand were made and the new concrete parameters such as compressive strength, water absorption and unit Weight were examined. In the second phase, nano SiO 2 in all mixes from the brick waste materials were replaced for the cement and then the experiments of compressive strength and water absorption were done on the samples that contained nano SiO 2 and waste clay bricks. The results clearly revealed that, in light of some positive effect such as a reduction in the concrete unit weight and recycling the waste materials and also the minimum reduction of compressive strength, using brick waste materials may be considered a suitable choice in concrete especially in areas close to brick furnaces. Furthermore, nano SiO 2 can improve the strength and durability of concrete. Conclusively, using waste bricks can be an effective measure in sustainable development.

Choice of thixotropic index to evaluate formwork pressure characteristics of self-consolidating concrete

Formwork lateral pressure exerted by concrete is affected by mixture composition, placement conditions, and formwork characteristics. The mixture composition includes binder type and content, supplementary cementitious materials, fillers, water-to-cementitious ratio, content and characteristics of coarse aggregate, paste volume, chemical admixtures, concrete unit weight, concrete consistency, and temperature. Thixotropy of concrete expressed here in terms of structural build-up at rest is employed to collectively reflect the effect of combined mix design factors on formwork pressure. This research demonstrates relationships between 12 indices that can be used to evaluate the structural build-up at rest of concrete, determined using portable vane, inclined plane, and concrete rheometer tests, and formwork pressure characteristics. These characteristics include the initial maximum pressure after casting and pressure decay. In total, 12 SCC batches and one conventional vibrated concrete were prepared with various consistency levels, coarse aggregate contents, sand-to-total aggregate ratios, and paste volumes to produce wide-range of thixotropic properties and formwork pressure. The results showed that concrete of greater level of thixotropy can develop greater structural build-up when left in rest and displays lower lateral pressure during placement and rapid decay of pressure thereafter. Statistical ranking of the 12 structural build-up indices suggested that the portable vane test can be the best to reflect structural build-up at rest of concrete.

Developing Structural Lightweight Concrete Using Volcanic Scoria Available in Saudi Arabia

This experimental investigation explored the feasibility of using volcanic scoria rocks located in the north-western region of Saudi Arabia for producing structural lightweight concretes (SLWCs). Several concrete mixes were designed, produced, and tested, to study the effects of various material and composition parameters on workability, unit weight, strength properties, and chloride penetration resistance of concrete. Test results indicated that the volcanic scoria could be used as coarse and fine aggregates for producing a series of lightweight concretes exhibiting strengths in the structural range. The SLWCs developed had a 7-day compressive strength of about 53–76 % of the 28-day compressive strength, a 28-day splitting tensile strength of about 9–11 % of the compressive strength, a 28-day flexural strength of about 10–15 % of compressive strength, and Poisson’s ratio of about 0.19–0.21. The modulus of elasticity could be expressed with a formula similar to the one proposed by ACI 318-08. The stress–strain diagrams of the SLWCs produced were comparable to those for normal-weight concrete (NWC) with larger strain capacity at peak stress ranging from 2,600 to 3,300 μ compared to 2,000 μ for NWC. The 28-day chloride penetration resistance of the SLWCs developed falls within low to moderate range according to the criteria of ASTM C 1202.

Studi Potensi Limbah Debu Pengolahan Baja (Dry Dust Collector) sebagai Bahan Tambah pada Beton

Abstract&#x0D; This research has the objectives of finding out the concrete properties, which are, workability, unit weight, compressive strength, flexural strength and finding out an optimum composition of dry dust collector waste in the concrete mixture. &#x0D; In this research, 3 different kinds of concrete mixture were created based on the amount of waste substitution in the concrete. The examined concrete mixture compositions were the concrete with water cement ratio = 0.68, with the waste substitution as much as 0%, 10%, and 20% of sand weight. The mechanical behavior of the concrete was tested at the age of 28 days.The research results show that, an addition of dry dust collector waste in the concrete influence concrete workability, unit weight of concrete with 10 % waste as much as 2497,44 kg/m3. The concrete with 10 % waste had the higher unit weight compare with the normal concrete without waste. The dry dust collector waste substitution as much as 10% in the concrete can improve compressive strength and flexural strength concrete. The compressive strength of the concrete increases as much as 21.21%, flexural strength of the concrete increases as much as 3.48%. &#x0D; &#x0D; Keywords: concrete, dry dust collector waste, compressive strength, flexural strength

중량 자철석 콘크리트의 유동성 및 역학적 특성에 미치는 보통중량 굵은골재 치환율의 영향

The objective of this study is to evaluate the workability and various mechanical properties of heavyweight magnetite concrete and examine the reliability of the design equations specified in code provisions. The main parameters investigated were the water-to-cement ratio and substitution level of normal-weight coarse aggregate (granite) for magnetite. The oven-dried unit weight of concrete tested ranged between 2446 and 3426 kg/m 3 . The measured mechanical properties included compressive strength development, stress-strain curve, splitting tensile strength, moduli of elasticity and rupture, and bond stress-slip relationship of concrete. Test results revealed that the initial slump of heavyweight magnetite concrete increased as the substitution level of normal-weight coarse aggregate increases. The substitution level of normal-weight coarse aggregate had little influence on the compressive strength and tensile resistance capacity of heavyweight concrete, while it significantly affected the modulus of elasticity and stress-strain curves of such concrete. The design equations of ACI 349-06 and CEB-FIP provisions mostly conservatively predicted the mechanical properties of heavyweight magnetite concrete, but the empirical equations for modulus of elasticity and splitting tensile strength need to be modified considering the unit weight of concrete.

Strength and fresh properties of borogypsum concrete

This paper reports on a comprehensive study on the properties of concrete containing borogypsum. Properties studied include setting time and volume expansion of paste, unit weight and consistency of fresh concrete, compressive and splitting tensile strength of hardened concrete. Potential use of borogypsum as a concrete admixture is discussed. Borogypsum contents of 0%, 3%, 5%, 10% and 15% by mass are used in the study. The strength results show that concrete mixtures containing 3% and 5% borogypsum developed higher strength values than those of control concrete mixtures. Based on strength properties, it is determined that 5–10% borogypsum may be used as a concrete additive. On the other hand, inclusion of borogypsum as a cement replacement reduced the consistency. Moreover, test results also showed that borogypsum delays setting time of paste made with cement and borogypsum. Thus, the use of borogypsum as a set retarder of Portland cement is recommended.