Finite Element Analysis of Concrete Slabs Under Torsion

The purpose of this study was to Analyze the characteristics of theaggregates used in concrete mixtures and analyze how muchincrease in compressive strength of concrete with a variation ofnickel slag substitution 0%, 5%, 15%, 25% compared with normalconcrete. The characteristics of the material examined are watercontent, sludge content, specific gravity and absorption, volumeweight, abrasion with los angeles machines, and filter analysis.While the large increase in compressive strength of concrete can betested at the age of 7 days, 14 days, 28 days and 35 days. From the results of the analysis of the characteristics of nickel slagwaste in concrete mixes meet the test standards in concretemixtures, with a moisture content of 0.86%, sludge content of 0.44%,specific gravity of 2.94 gr / cm3, volume weight of 1.76 gr / cm3,abrasion 36.07%. And a large increase in compressive strength ofconcrete with a variation of nickel slag substitution of 0%, 5%, 15%,25% compared to normal concrete is increasing. The highestpercentage increase in concrete compressive strength is found inconcrete compressive strength between a variation of 15% with avariation of 25% at 14 days concrete age, with a percentage increasein value of 13.13%.

Concrete, which is usually composed of cement, water, and fine and coarse aggregate, is the most dynamic building material for the construction of physical infrastructures because of its strength and durability, which solidifies over time in response to environmental changes. The size and shape of the aggregate have a significant impact on workability, strength, and durability of concrete since various particle sizes produce distinct reactions. To support the manufacturing of sustainable concrete, the research suggested substituting stone dust (SD) for sand. In contrast to the addition of stone dust, the application of superplasticizers improves the workability of concrete. The study aims to examine the compressive strength of M20-grade concrete that has superplasticizer added in addition to stone dust as fine aggregate replacement. The Maximum compressive strength of concrete has been achieved at 40% sand replacement. The findings revealed that the increase in stone dust content results in an increase in compressive strength of concrete using superplasticizer. The use of superplasticizer serves to increase the workability of the concrete and has no discernible effect on the compressive strength up to 50% sand replacement. The 28-days compressive strength achieved maximum value at 50% sand replacement with 2% superplasticizer. When stone dust and superplasticizer are added, the concrete becomes denser;conversely, when the amount of stone dust and superplasticizer is increased, the concrete becomes more slumped. For the construction of sustainable concrete, the SD can be used in place of fine aggregate in conjunction with superplasticizer.

Concrete material innovations are no emerging more and more and are something that is really needed, one of which is material innovation with the addition of fiber. Fiber concrete is a mixture of concrete plus fiber. The fiber material can be asbestos fiber, plastic fiber (poly-propyline), or pieces of steel wire, plant fibers (hemp, coconut fiber, bamboo, palm fiber). The purpose of adding fiber is to improve or increase the mechanical properties of concrete in the form of tensile strength, compressive strength and flexural strength. This research uses areca nut skin fiber, the skin and seeds are separated, then the betel nut fiber is spread apart so that it does not clump when mixing, then the betel nut fiber is mixed little by little into the concrete mixture. This research aims to determine the effect of adding Areca nut fiber on the compressive strength of concrete aged 7, 14 and 28 days. The percentage of areca nut shell fiber used in this research as 1.6%, 2.4% and 4%. The research used test objects in the form of cubes measuring 15 x 15 x15 cm, with a sample of 12 pieces of concrete, including 9 pieces of concrete with a mixture of betel nut fiber according to each type of concrete aged 7, 14 and 28 days, and 3 pieces of concrete without mixed/normal. The test carried out on the concrete mixture is the compressive strength of the concrete. From the research results obtained, the results of testing the compressive strength of fiber concrete with a percentage of Areca fruit fiber of 1.6% at concrete ages of 7, 14, and 28 days obtained an average compressive strength result of 7.65 MPa, for testing the compressive strength of concrete with a percentage 2.4% for concrete ages of 7, 14 and 28 days experienced a decrease in average compressive strength of 5.88 MPa and for concrete compressive strength testing with a percentage of 4% for concrete ages of 7, 14 and 28 days there as an increase in average concrete compressive strength. The average is 11.43 MPa.

This study explores the response of spiral-reinforced lightweight concrete to short-term compression by conducting an experimental program. The response includes deformation capacity, compressive strength, concrete strain at compressive strength, modulus of elasticity, and failure mode. The response is explored by varying the pitch of spiral reinforcement, diameter of spiral wire, compressive strength of plain concrete, and specimen size. Test results show that deformation capacity of spiral-reinforced lightweight concrete decreases with an increase in compressive strength of plain lightweight concrete. Nevertheless, deformation capacity can be increased by reducing the pitch of spiral reinforcement and by increasing the diameter of spiral wire. This study also suggests the mathematical expressions to estimate the compressive strength of spiral-reinforced lightweight concrete, concrete strain at compressive strength, and modulus of elasticity of plain lightweight concrete. Understanding of the concrete response gained from the present study would be beneficial in analysis and design of lightweight concrete structural members.

The Impact of silica fume existence and its content with the duration of curing on concrete compressive strength (ordinary and high) has investigated experimentally. Two mixture sets were done in this work to examine the concrete ordinary and high strength. Every set involved four mixtures with varied silica fume proportions as a substitution of cement with (0, 5, 10 and 15 percent). Ninety-six cubes of concrete were prepared and cured by immersion in water to the required age (7, 28, 90 and 150 days). In ordinary concrete and high strength concrete, the results demonstrate that when silica fume used as a substitution with 15 %, the compressive strength of concrete gave the highest value. As compared with concrete having nil content of silica fume, the earned strength for high compressive concrete consisting of silica fume was relatively less than the corresponding ordinary concrete strength. However, continuously curing with water after 28 days produced a considerable increase in the compressive strength of concrete; such an increase in compressive strength was greater in the existence of silica fume

One of the approaches to producing lightweight concrete is by adding the aluminum powder to the cement mixture to create air bubbles in the concrete as such enabling pores to appear in the concrete. Aluminum powder can reduce the weight of lightweight concrete despite its tendency to reduce compressive strength. The compressive strength of concrete can be increased by certain methods, one of which is by the addition of Plastiment-VZ admixture. This study aims to investigate the effect of the use of Plastiment-VZ admixture on the compressive strength and flexural strength of lightweight concrete. The normal concrete compressive strength is designed to the range of 0.7 MPa – 5.0 MPa. The concrete testing specimens were in the form of a cube of 15 cm x 15 cm x 15 cm for the compressive test and beams with dimensions of 15 cm x 15 cm x 60 cm for the flexural test. The test results of the compressive strength obtained for normally aerated concrete (0% of Plastiment-VZ) is 6.31 MPa; and for the variation of 0.2% is 6.52 MPa, for 0.4% is 6.8 MPa, and for 0.6% is 8.04 MPa. The highest increase in strength occurred at 0.6% variation, which is 27.46% above normally aerated concrete. The degrees of flexural strength of the concrete produced from each variation of 0%; Based on the findings, it can be concluded that Plastiment-VZ has a significant effect on increasing the compressive strength and flexural strength of lightweight concrete. The more quantity of Plastiment-VZ is used, the higher the compressive strength and flexural strength are produced; even though, the optimum level for the use of Plastiment-VZ for aerated concrete has not been found.

Sand is extracted at a rate more than its restoration. Nevertheless, the availability of sand in the growing demand of the construction industry remains a challenge due to cost and quality problems. This study investigates the compressive strength of concrete by partially replacing sand with iron-ore waste. Experimental investigations were conducted to study the compressive strength, physical, mechanical and fresh property of concrete containing iron-ore waste. During the experiment, concrete cubes were prepared with 10-100% composition of iron ore waste to evaluate their compressive strength. Results from the experimentation revealed that, concrete cubes prepared by partially replacing sand with iron ore waste often yield a better compressive strength than a conventional concrete. More so, the densities of concrete cubes were observed to remain consistent but increased slightly, notably at 10% and 20% of waste replacement. Meanwhile, at 30% waste replacement, there was reduction in compressive strength at 28days curing age and this reduction continued as percentage iron ore increased towards 100%. Also, increase in compressive strength of concrete cubes was observed at 10-20% sand replacement with iron ore. It was therefore established that concrete produced under 10% and 20% replacement, can be utilized for all construction purposes requiring concrete.

Acceleration of early strength of concrete can be obtained by reducing water in the concrete mixture followed by addition of superplasticizer. The application of the addition of superplasticiser to water-reduced concrete mixtures requires innovation in providing a time lag to produce good workability. This study analyzes the effect of giving a time delay when adding superplasticizer followed by reducing water with certain variations on the workability and early strength of concrete. The results of this research are very important for the concrete industry with the purpose of shortening the removal time of formwork and optimizing the construction process. Water cement ratio is adjusted by reducing its volume by a fraction of 10% to 30%, superplasticizer 1% to the weight of cement is added in two stages, during the initial mixing and after one or two hours afterwards. 0.3% retarder was added to control homogeneity during mixing. The test results concluded that the reduction of water that provided the highest increase in concrete compressive strength at 4 days was LN25-1 of 21.94 MPa (87% of the design compressive strength) and LN20-2 of 19.12 MPa (76% of the compressive strength plan). The optimal amount of water reduction at the initial age of the concrete is 20 – 25% of the design water weight. Giving a time lag does not reduce the increase in concrete strength due to the addition of superplasticizer.

Influence of magnetic field treated water on the compressive strength and bond strength of concrete containing silica fume

The use of high-strength concrete (HSC) started about four decades ago in world. Using (HSC) supports the applications in civil engineering such as reduce the size of buildings columns, increase the girders length, increase the buildings stores as well as the economics benefits. The paper aims to investigate the effect of using various compressive strength of concrete mixes on the behavior and load capacity of reinforced concrete beams in terms of cracking, yield, failure loads, deflection and ductility. The experimental program included the cast of six reinforced concrete beams with 1.75 m length and cross section of 200 ϗ 300 mm. The beams specimens were tested under two points loads. Several concrete mixes were tried to obtain the concrete compressive strengths 30.9, 40.3, 51.2, 60.1, 71.6 and 89 MPa that used for every specimen beam. The experimental results showed that the increase of concrete compressive strength developed the load capacity strength and ductility. By increasing the compressive strength ratio with (30%, 67%, 95%, 132%, and 188%) caused increase in cracking load by 25%, 66%, 94%, 116% and 152% respectively, and increased the yield and failure loads by (18%, 31%, 41%, 51%, and 69%), (14%, 32%, 47%, 59% and 77%) respectively. As well as the deflection in yield was decreased by (13%, 22%, 33%, 26% and 13%), while it was increased by 10%, 16%, 23%, 26%, and 39% respectively in failure stage as a result of increased of load failure. Adding to that, ductility is increased by 27%, 50%, 84%, 70% and 61%, respectively with the of increasing of compressive concrete strength in ratios mentioned above.

The issues considered in the article are related to the determination of the combined effect of mechanochemical activation of Portland cement and its consumption, ground quartz sand, superplasticizer (hereinafter SP) and amorphous microsilica (hereinafter MS) on the strength and abrasion resistance of concrete. The effect of partial replacement of Portland cement with ground quartz sand was studied, the consumption of which in the mixed binder varied in the range from 0 to 40%. The consumption of MS in the mixed binder varied in the range from 0 to 10%, and the consumption of SP ‒ from 0 to 1% of the Portland cement mass. The consumption of Portland cement in the concrete mix varied in the range from 350 to 450 kg/m3. The activation period of the binder was 180 sec. The obtained experimental results indicate the possibility of varying the recipe and technological factors to increase the strength of concrete and reduce the consumption of Portland cement in the concrete mix. The obtained experimental data indicate a significant effect of mechanochemical activation of the mixed binder on the strength of concrete. Of the listed factors, the greatest effect on the compressive strength of concrete is exerted by the consumption of ground sand and SP in the mixed binder. The addition of ground quartz sand (40%) to the mixed binder causes a decrease in the strength of concrete from 35.1 MPa to 22.5 MPa (by 35.9%) at the grade age. An increase in the consumption of SP (up to 1%) in the mixed binder causes an increase in the strength of concrete from 17 MPa to 28 MPa (by 64.7%) at the early stages of hardening and from 35.1 MPa to 49.7 MPa (by 41.6%) at the grade age. The use of MS (10%) in the composition of the mixed binder provides a relatively insignificant increase in strength (6.5%) at the early stages of curing and (4.6%) at the grade age compared to the control. The use of mechanical activation provides an increase in concrete strength by 62.4% (at the early stages of hardening) and 25.1% (at the grade age) compared to the control. The combined effect of mechanical activation (180 sec), addition of ground quartz sand (40%), MS addition (10%) and an increase in the consumption of SP (1%) in the composition of the mixed binder (Portland cement consumption 350 kg/m3) causes an increase in the compressive strength of concrete (8, ), a decrease in concrete abrasion from 0.33 (40% ground sand) to 0.21 g/cm2 and a decrease in Portland cement consumption from 350 kg/m3 (control) to 189 kg/m3 (by 46%).

: PLTU waste produces a large enough amount that requires management so as not to cause environmental problems. In the field of construction, fly ash and bottom ash have the potential to be developed, one of which is their use as a base material. Potential if developed, one of which is its use as a basic ingredient in the concrete making mixture. This research aims to determine the percentage of increase or decrease in compressive strength of concrete produced with the addition of fly ash and bottom ash with a variation of 0%. Fly ash and bottom ash have variation of 0%, 7.5%, 15%, and 22.5%, with the age of 14 days, 21 days, and 28 days. 14 days, 21 days, and 28 days for each combination of mixtures with a plan quality of K-250 and know the comparison of compressive strength of concrete without mixtures and using a mixture of fly ash and bottom ash. Based on the research showed that the substitution of fly ash as cement and bottom ash as fine aggregate with a percentage of 0%, 7.5%, 15%, and 22.5%, the compressive strength of days-old concrete was 236 kg/cm2, 193 kg/cm2, 175 kg/cm2, 148 kg/cm2, 21 days-old concrete compressive strength values of 168 kg/cm2, 257 kg/cm2, 210 kg/cm2, 185 kg/cm2 and the compressive strength of concrete aged 28 days by 324 kg/cm2, 281 kg/cm2, 237 kg/cm2, 212 kg/cm2. The existence of the substitution of fly ash and bottom ash to normal concrete by 7.5%, 15%, and 22.5% decreased in strength as percentage of fly ash substitution to cement and bottom ash to normal concrete increased. Fly ash is to cement, and bottom ash is to sand. The greater the substitution of fly ash and bottom ash substitution to normal concrete, the more the strength of concrete descreased due to the reduced compositon of fine aggregate gradation and cement to normal concrete. Keywords : Concrete, Compressive Strength, Fly Ash, Bottom Ash ABSTRAK: Limbah PLTU ini menghasilkan jumlah yang cukup besar sehingga memerlukan pengelolaan agar tidak menimbulkan masalah lingkungan. Dalam bidang kontruksi abu terbang (fly ash) dan abu dasar (bottom ash) merupakan suatu hal yang sangat potensial bila dikembangkan, salah satu penggunaannya sebagai bahan dasar campuran pembuatan beton. Penelitian ini bertujuan untuk mengetahui persentase peningkatan atau penurunan kuat tekan beton yang dihasilkan dengan tambahan fly ash dan bottom ash dengan variasi sebesar 0%, 7,5%, 15%, dan 22,5% dengan umur 14 hari, 21 hari serta 28 hari untuk setiap kombinasi campuran dengan mutu rencana K-250 dan mengetahui perbandingan kuat tekan beton tanpa campuran dan memakai campuran fly ash dan bottom ash. Berdasarkan dari hasil penelitian dengan substitusi fly ash sebagai semen dan bottom ash sebagai agregat halus dengan persentase 0%, 7,5%, 15%, dan 22,5%, diperoleh nilai kuat tekan beton umur 14 hari sebesar 236 kg/cm2, 193 kg/cm2, 175 kg/cm2, 148 kg/cm2, nilai kuat tekan beton umur 21 hari sebesar 168 kg/cm2, 257 kg/cm2, 210 kg/cm2, 185 kg/cm2 dan nilai kuat tekan beton umur 28 hari sebesar 324 kg/cm2, 281 kg/cm2, 237 kg/cm2, 212 kg/cm2. Adanya subsitusi fly ash dan bottom ash terhadap beton normal sebesar 7,5%, 15%, dan 22,5% mengalami penurunan kekuatan seiring bertambahnya persentase substitusi fly ash terhadap semen dan bottom ash terdahap pasir. Semakin besar substitusi fly ash dan bottom ash terhadap beton normal, semakin menurun kekuatan beton disebabkan karena berkurangnya komposisi gradasi agregat halus dan semen terhadap beton normal.Kata Kunci : Beton, Kuat Tekan, Fly Ash, Bottom Ash

The article presents an analysis of the influence of the amount of polypropylene fiber, cement and polycarboxylate-type superplasticizer on the strength characteristics of concrete for rigid road surfaces and transport structures. Portland cement PC II/A-Sh-500R-N, polypropylene fiber Baumesh with a fiber length of 36 mm and a diameter of 0.68 mm, and polycarboxylate-type superplasticizer MC-PowerFlow 3200 were used. A 3-factor experiment was conducted in which the following composition factors were varied: the amount of Portland cement, 300 to 380 kg/m3; the amount of polypropylene fiber Baumesh, 2.5 to 3.5 kg/m3; the amount of superplasticizer, 1.0 to 1.6% of the cement mass. The compressive strength of fiber-reinforced concretes was determined at the age of 3 and 28 days, and the tensile strength at the age of 28 days. All studied concrete mixtures had equal mobility class P2. The influence of varied factors on the W/C ratio of mixtures was assessed. The amount of Portland cement has the greatest influence on this indicator. Increasing the dosage of superplasticizer from 1.0% to 1.6% allows reducing the W/C ratio by 8-24%. The amount of polypropylene fiber has a limited effect on the W/C ratio. The amount of Portland cement has the greatest influence on the compressive strength of the studied fiber-reinforced concretes. When the dosage of binder is increased from 300 kg/m3 to 380 kg/m3, the strength of fiber-reinforced concretes at the age of 3 increases by 74-80%, the strength at the project age increases by 38-47%. Increasing the amount of superplasticizer provides an increase in compressive strength at an early age by 10-12%, at a project age by 12-14%. Increasing the amount of reinforcing fibers from 2.5 to 3.5 kg/m3 at a high content in the mixture of binder and plasticizer does not significantly affect. By increasing the amount of fiber at a low amount of cement and superplasticizer, the early and project compressive strength of fiber-reinforced concretes increases insignificantly. By increasing the dosage of the binder to 380 kg/m3, the tensile strength of fiber-reinforced concretes increases by 9-12%. A similar increase in tensile strength at bending is achieved by increasing the dosage of the superplasticizer from 1.0 to 1.6%. The nature of the influence of polypropylene fiber on this strength indicator is nonlinear. An increase in strength by 9-12% is observed with an increase in fiber dosage from 2.5 kg/m3 to 3.0 kg/m3 both at high and low amount of binder and superplasticizer. It has been established that in general, from the point of view of achieving the highest compressive and tensile strength when bending, it is rational to introduce Baumesh polypropylene fiber in an amount of about 3.0 kg/m3 and MC-PowerFlow 3200 additive in an amount of 1.5-1.6% of the cement mass.

An experimental study on composite columns of square and circular steel hollow sections filled with normal concrete has been held in this paper. The concrete used in this study have two different compressive strength with mixing ratios of (1:2:4) and (1:1.5:3); the compressive strength of concrete were (22.9 MPa) and (31.8 MPa) respectively. Square steel hollow sections of (7.5×7.5 cm) and 2 mm thickness used with a yield stress of (352 MPa) while the circular hollow sections have (7.5 cm) diameter and 2 mm thickness with a yield strength of (327 MPa). Samples tested under the effect of concentric and eccentric axial loads with one case in which the column tested horizontally as a beam to evaluate the maximum bending resistance. The interaction curves for both shapes of columns and for two different concrete compressive strength are presented with a simple analysis for the pattern of failure in columns for each case of loading and for each type. The results show that the increase in compression strength of concrete provides more capacity for the composite columns in axial loading more than bending due to the confinement, and the failure in columns with square cross-sections are different from those which have circular cross-sectional area.

High strength concrete (HSC) posses more problems, since it has less ductility in comparison with normal strength concrete (NSC). To overcome this problem was reinforced with fibers and hybrid fibers. The effects of fibers and hybrid fibers upon the properties of high-strength concrete mixtures containing superplasticizing admixtures have been investigated. The properties of fibrous high-strength concrete and high-strength concrete are compared. Results showed that decrease in workability of all concrete mixtures containing polypropylene, glass and hybrid fibers compared with control mix. It was found that the addition polypropylene fibers increase the suitable w/c ratio to save the workability from 0.24 to 0.26, 0.27 and 0.29 at 0.5, 1.0 and 1.5 volume fraction respectively. While the w/c ratio increased to 0.35 when the 0.4% glass fiber was added. HSC with 1.5% polypropylene fibers showed superior splitting and flexural strengths over the other concrete without or with fibers, compared with HSC without fibers the increasing were 30.76% and 25.61% respectively. At 28-day age, fibrous high-strength concrete showed higher compressive, splitting and flexural strengths than the high-strength concrete, depending upon the types and volume fraction of fibers. The results obtained demonstrate that the addition of the hybrid fibers to the high strength concrete showed that the ratio of (0.7% polypropylene+0.12% glass fibers) at volume fraction 0.82% gives better fresh and hardened properties than the ratio (0.3% polypropylene+0.28% glass fibers) at volume fraction 0.58%. The maximum increase in compressive strength, splitting strength and flexural strength of high strength concrete contains (0.7% polypropylene+0.12% glass fibers) were 9.57%, 15.38% and 14.04% respectively.