• Title/Summary/Keyword: Engineering Properties of concrete

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Optimum LWA content in concrete based on k-value and physical-mechanical properties

  • Muda, Zakaria Che;Shafigh, Payam;Yousuf, Sumra;Mahyuddin, Norhayati Binti;Asadi, Iman
    • Advances in concrete construction
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    • v.14 no.3
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    • pp.215-225
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    • 2022
  • Thermal comfort and energy conservation are critical issues in the building sector. Energy consumption in the building sector should be reduced whilst enhancing the thermal comfort of occupants. Concrete is the most widely used construction material in buildings. Its thermal conductivity (k-value) has a direct effect on thermal comfort perception. This study aims to find the optimum value of replacing the normal aggregate with lightweight expanded clay aggregate (LECA) under high strengths and low thermal conductivity, density and water absorption. The k-value of the LECA concrete and its physical and mechanical properties have varying correlations. Results indicate that the oven-dry density, compressive strength, splitting tensile strength and k-value of concrete decrease when normal coarse aggregates are replaced with LECA. However, water absorption (initial and final) increases. Thermal conductivity and the physical and mechanical properties have a strong correlation. The statistical optimisation of the experimental data shows that the 39% replacement of normal coarse aggregate by LECA is the optimum value for maximising the compressive and splitting tensile strengths whilst maintaining the k-value, density and water absorption at a minimum.

Mechanical Properties of Carbon Fiber Reinforced Porous Concrete for Planting

  • Park Seung-Bum;Kim Jeong-Hwan
    • KCI Concrete Journal
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    • v.14 no.4
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    • pp.161-169
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    • 2002
  • The mechanical properties of fiber reinforced porous concrete for use as a planting material were investigated in this study. Changes in physical and mechanical properties, subsequent to the addition of carbon fiber and silica fume, were studied. The effects of recycled aggregate were also evaluated. The applicability as planting work concrete material was also assessed. The results showed that there were no remarkable changes in the void and strength characteristics following the increase in proportion of recycled aggregate. Also, the mixture with 10% silica fume was found to be the most effective for strength enforcement. The highest flexural strength was obtained when the carbon fiber was added with 3%. It was also noticed that PAN-derived carbon fiber was superior to Pitch-derived ones in view of strength. The evaluation of its usage for vegetation showed that the growth of plants was directly affected by the existence of covering soil, in case of having the similar size of aggregate and void.

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Interaction of magnetic water, silica fume and superplasticizer on fresh and hardened properties of concrete

  • Mazloom, Moosa;Miri, Sayed Mojtaba
    • Advances in concrete construction
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    • v.5 no.2
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    • pp.87-99
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    • 2017
  • After passing through a magnetic field, the physical quality of water improves, and magnetic water (MW) is produced. There are many investigations on the effects of magnetic field on water that shows MW properties like saturation and memory effect. This study investigates the fresh and hardened properties of concrete mixed with MW, which contains silica fume (SF) and superplasticizer (SP). The test variables included the magnetic field intensity for producing MW (three kinds of water), SF content replaced cement (0 and 10 percent), water-to-cementitious materials ratio (W/CM=0.25, 0.35 and 0.45) and curing time (7, 28 and 90 days). The results of this study show that MW had a positive impact on the workability and compressive strength of concrete. By rising the intensity of the magnetic field which was used for producing MW, its positive influence on both workability and compressive strength improved. MW had greater positive impacts on samples containing SP that did not have SF. Moreover, the best compressive strength improvements of concrete achieved as W/CM ratio decreased.

Mechanical Properties of Energy Efficient Concretes Made with Binary, Ternary, and Quaternary Cementitious Blends of Fly Ash, Blast Furnace Slag, and Silica Fume

  • Kim, Jeong-Eun;Park, Wan-Shin;Jang, Young-Il;Kim, Sun-Woo;Kim, Sun-Woong;Nam, Yi-Hyun;Kim, Do-Gyeum;Rokugo, Keitetsu
    • International Journal of Concrete Structures and Materials
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    • v.10 no.sup3
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    • pp.97-108
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    • 2016
  • When the energy performance of concrete is substantially higher than that of normal type concrete, such concrete is regarded as energy efficient concrete (WBSCSD 2009). An experimental study was conducted to investigate mechanical properties of energy efficient concrete with binary, ternary and quaternary admixture at different curing ages. Slump test for workability and air content test were performed on fresh concretes. Compressive strength, splitting tensile strength were made on hardened concrete specimens. The mechanical properties of concrete were compared with predicted values by ACI 363R-84 Code, NZS 3101-95 Code, CSA A23.3-94 Code, CEB-FIP Model, EN 1991, EC 2-02, AIJ Code, JSCE Code, and KCI Code. The use of silica fume increased the compressive strengths, splitting tensile strengths, modulus of elasticities and Poisson's ratios. On the other hand, the compressive strength and splitting tensile strength decreased with increasing fly ash.

Spalling Properties of High Strength Concrete Mixed with Various Mineral Admixtures Subjected to Fire

  • Han, Cheon-Goo;Han, Min-Cheol;Heo, Young-Sun
    • International Journal of Concrete Structures and Materials
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    • v.2 no.1
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    • pp.41-48
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    • 2008
  • This study investigates the spalling properties of high strength concrete designed with various types of mineral admixture and diverse content ratios of polypropylene (PP) fiber. Experimental factors considered in series I are four pozzolan types of mineral admixture and series II consists of three shrinkage reducing types of mineral admixture. PP fiber was added 0.05, 0.10 and 0.15vol. % in each mixture of series I and series II, so that totally 27 specimens including control concretes in each series were prepared. Test results showed that the increase of fiber content decreased the slump flow of fresh concrete and increased or decreased the air content depending on the declining ratio of slump flow. For the properties of compressive strength, all specimens were indicated at around 50 MPa, which is high strength range; especially all specimens in series II were 60 MPa. Fire test was conducted in standard heating curve of ISO 834 with ϕ100×200mm size of cylinder moulds for 1 hour. The specimens incorporating silica fume exhibited severe spalling and most specimens without the silica fume could be protected from the spalling occurrence in only 0.05vol % of PP fiber content. This fire test results demonstrated that the spalling occurrence in high strength concrete was not only affected by concrete strength related to the porosity of microstructure but also, even more influenced by micro pore structure induced by the mineral admixtures.

Effects of cement dosage and steel fiber ratio on the mechanical properties of reactive powder concrete

  • Erdogdu, Sakir;Kandil, Ufuk;Nayir, Safa
    • Advances in concrete construction
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    • v.8 no.2
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    • pp.139-144
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    • 2019
  • In this study, the mechanical properties of reactive powder concrete (RPC) with a constant cement to silica fume ratio of 4 were investigated. In the experimental program, reactive powder concretes with steel fiber at different ratios were produced. Five productions using quartz sand with a maximum grain size of 0.6 mm were performed. A superplasticizer with a ratio of 3% of the cement was used for all productions. 40×40×160mm prismatic specimens were prepared and tested for flexural and compression. The specimens were exposed to two different curing conditions as autoclave and standard curing condition. Autoclave exposure was performed for 3 hours under a pressure of 2 MPa. It was observed that the compressive strength of concrete, along with the flexural strength exposed to autoclave was quite high compared to the strength of concretes subjected to standard curing. The results obtained indicated that the compressive strength, along with the flexural strength of autoclaved concrete increased as the amount of cement used increases. Approximately 15% increase in flexural strength was achieved with a 4% steel fiber addition. The maximum compressive strength that has been reached is over 210 MPa for reactive powder concrete for the same steel fiber ratio and with a cement content of 960kg/m3. The relationship between compressive strength and flexural strength of reactive powder concrete exposed to both curing conditions was also identified.

Concrete properties prediction based on database

  • Chen, Bin;Mao, Qian;Gao, Jingquan;Hu, Zhaoyuan
    • Computers and Concrete
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    • v.16 no.3
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    • pp.343-356
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    • 2015
  • 1078 sets of mixtures in total that include fly ash, slag, and/or silica fume have been collected for prediction on concrete properties. A new database platform (Compos) has been developed, by which the stepwise multiple linear regression (SMLR) and BP artificial neural networks (BP ANNs) programs have been applied respectively to identify correlations between the concrete properties (strength, workability, and durability) and the dosage and/or quality of raw materials'. The results showed obvious nonlinear relations so that forecasting by using nonlinear method has clearly higher accuracy than using linear method. The forecasting accuracy rises along with the increasing of age and the prediction on cubic compressive strength have the best results, because the minimum average relative error (MARE) for 60-day cubic compressive strength was less than 8%. The precision for forecasting of concrete workability takes the second place in which the MARE is less than 15%. Forecasting on concrete durability has the lowest accuracy as its MARE has even reached 30%. These conclusions have been certified in a ready-mixed concrete plant that the synthesized MARE of 7-day/28-day strength and initial slump is less than 8%. The parameters of BP ANNs and its conformation have been discussed as well in this study.

Engineering Properties of High Strength Concrete Using Lime Stone Recycling Fine Aggregate (석회암 순환잔골재를 사용한 고강도 콘크리트의 공학적 특성)

  • Han, Cheon-Goo;Kim, Hyun-Woo
    • Journal of the Korean Recycled Construction Resources Institute
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    • v.3 no.1
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    • pp.72-79
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    • 2007
  • This study investigates the engineering properties of concrete incorporating lime stone crushed fine aggregate(Ls), which has been abandoned about 20% of total production due to the low purity. Test results showed that increase of Ls had favorable fluidity and slightly decreased air content. Bleeding capacity of all specimens was not appeared as those were high strength mixture proportion, but the specimens using more Ls accelerated initial and final setting. For the mechanical properties, specimens incorporating higher ratio of Ls, overall, resulted in increase of compressive strength, and exhibited very small inclined tendency in a dynamic elasticity modulus test In addition, for the durability properties, specimens incorporating higher Ls dramatically decreased a drying shrinkage and showed similar tendency in a frost & thaw test, as well as showing no more change in an accelerated neutralization test from the beginning. In conclusion, as it was confirmed in the experimental test, the high strength concrete applying Ls did not showed any problems in the aspects of engineering properties and mostly exhibited even more excellent quality than the specimens using natural fine aggregate.

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Case-based reasoning approach to estimating the strength of sustainable concrete

  • Koo, Choongwan;Jin, Ruoyu;Li, Bo;Cha, Seung Hyun;Wanatowski, Dariusz
    • Computers and Concrete
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    • v.20 no.6
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    • pp.645-654
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    • 2017
  • Continuing from previous studies of sustainable concrete containing environmentally friendly materials and existing modeling approach to predicting concrete properties, this study developed an estimation methodology to predicting the strength of sustainable concrete using an advanced case-based reasoning approach. It was conducted in two steps: (i) establishment of a case database and (ii) development of an advanced case-based reasoning model. Through the experimental studies, a total of 144 observations for concrete compressive strength and tensile strength were established to develop the estimation model. As a result, the prediction accuracy of the A-CBR model (i.e., 95.214% for compressive strength and 92.448% for tensile strength) performed superior to other conventional methodologies (e.g., basic case-based reasoning and artificial neural network models). The developed methodology provides an alternative approach in predicting concrete properties and could be further extended to the future research area in durability of sustainable concrete.

Experimental study on geopolymer concrete prepared using high-silica RHA incorporating alccofine

  • Parveen, Parveen;Singhal, Dhirendra;Jindal, Bharat Bhushan
    • Advances in concrete construction
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    • v.5 no.4
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    • pp.345-358
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    • 2017
  • This paper describes the experimental investigation carried out to develop geopolymer concrete using rice husk ash (RHA) along with alccofine. The study reports the fresh and hardened properties of the geopolymer concrete (GPC) activated using alkaline solution. GPC were prepared using different RHA content (350, 375 and 400kg/m3), the molarity of the NaOH (8, 12 and 16M). The specimens were cured at 27C and 90C. GPC was activated using NaOH, Na2SiO3, and alccofine. Prepared GPC samples were tested for compressive and splitting tensile strengths after 3, 7 and 28 days. RHA was suitable to produce geopolymer concrete. Results indicate that behavior of GPC prepared with RHA is similar to fly ash based GPC. Workability and strength can be improved by incorporating the alccofine. Further, alccofine and heat curing improve the early age properties of the GPC. Heat curing is responsible for the initial polymerization of GPC which leads to high workability and improved mechanical properties of the GPC. High strength can be achieved by using the high concentration alkaline solution in terms of molarity and at elevated heat curing. Further, RHA based geopolymer concrete has tremendous potential as a substitute for ordinary concrete.