Slump

ÇÖKME (SLUMP) DENEYİ (TS EN 12350-2) Kapsam Çökme (slump) deneyi, taze beton kıvamını tayin etmek amacıyla yapılır. Çökme deneyi, 10 mm ile200 mm arasında çökme değerine sahip betonların kıvamındaki d eğişimlere duyarlıdır. Bu sınırlar dışında, çökme değerinin ölçülmesi yoluyla kıvam tayini uygun değildir ve bu durumda diğer kıvam tayini deneyleri kullanılmalıdır. Deney esnasında, taze betondaki çökmenin, kalıbın (çökme hunisinin) çekilmesinden sonraki bir dakikalık süreden sonra da devam etmesi, çökme deneyinin bu betonun kıvamını tayin etmek için uygun olmadığını gösterir. Agrega en büyük tane büyüklüğü 40 mm.den daha fazla olan betonlar da çökme deneyi uygun değildir. Prensip Taze beton, kesik huni şekilli kalıp içerisine sıkıştırılarak doldurulur. Kalıbın yukarı doğru çekilerek alınmasından sonra, taze beton kütlesindeki çökme mesafesi, betonun kıvam ölçüsü olarak kullanılır.

The cost of tensile member of concrete has always attracted attention of civil engineers to be supplemented by some cheaper material. This paper focuses the advantages of using naturally available material namely basalt as fibre reinforcement to enhance the strength as well as reinforcement akin properties in the concrete. Basalt an igneous origin rock has excellent load bearing properties can be a choice for massive concrete works in the construction industry. In the paper the engineering properties of basalt fibres are worked out experimentally and were discussed as a comparable choice of already in use synthetic fiber materials. Basalt being cheap and easily available fibre may be used for the construction of structural units with cement-paste or cement mortar / concrete composites have great potential, especially for developing countries.

Concrete  is  very  variable  material,  having  a  wide  range  of  strengths  and  stress-strain  curve.  Concrete  composite  material  whose  basic  properties      are      related  to  the  characteristic  of  constituent  element,  especially  the  aggregate.  This  research  aimed  to  investigate  the  effect  of  replacing sharp sand with stone dust as an alternative to only river sand. Sieve  analysis  was  carried  out  on  the  aggregate  to  determine  the  size  of  particle distribution. Slump test was carried out to compare the batches of concrete  for  the  grade,  water  content  between  batches  of  concrete  and  amount  of  aggregate.  Compressive  strength  test  was  carried  out  on  concrete cubes made from sharp sand and  concrete  cubes  made  from replacement  of  sharp  sand  with  stone  dust  also  concrete  made  from  ordinary  stone  dust  at  constant  of  free  water/cement  ratio  0.5.  To  check  the properties of concrete produced with different materials, the tests were done  for  7,  14,  21  and  28  days.  The  result  obtained  indicated  that  the  strength  of  using  sharp  sand  with  stone  dust  in  concrete  production  was  higher  than  the  strength  of  stone  dust  in  concrete  also  higher  than  the  strength of using sharp sand in concrete.

In the construction industry, sustainable development has become a major concern over the years mainly due to the waste produced during construction, but more significantly, during demolition or destruction of large concrete structures. Due to the day-by-day increasing amount of demolished concrete waste, the idea of recycling such waste to produce aggregate for reuse in construction has been increasingly encouraged, thereby promoting the use of a recycled coarse aggregate as a substitute for the natural coarse aggregate. Reusing the aggregates obtained from demolished waste concrete not only conserves natural virgin aggregate but also reduces the need for landfills, decreases energy consumption and also lead to cost savings. In this study, experimental investigations were based on recycled coarse aggregate (RCA) obtained from crushing waste concrete found at the B.I.T. Sindri campus, Dhanbad, Jharkhand, India. The major focus of the research was obtaining the 28-day compressive strength for concrete with varying RCA content of 0%, 25%, 50%, 75%, and 100%. A total of five mixes with water-cement ratio of 0.44 were utilized for this purpose. The experimental results show that fresh natural coarse aggregate has the highest slump value, thereafter it starts deceasing with increasing the content of recycled coarse aggregate. There was a trend of decreasing strength of the 28th day compressive strength test with increase in the RCA content. However, the 50% RCA concrete mix produced very similar compressive strength to that of the 100% natural coarse aggregate concrete.

Visando uma melhoria das propriedades físicas e mecânicas do concreto, este trabalho surge com o intuito de estudar e analisar estas melhorias através da magnetização da água de amassamento utilizando um campo magnético fixo. Algumas pesquisas em outros países, sendo poucas no Brasil, tem comprovado que a magnetização da água implica em uma reorganização de suas moléculas, influindo em uma maior hidratação do cimento, o que faz com que a mistura de concreto seja assim aprimorada tanto no estado fresco quanto no estado endurecido. Com isso buscou-se realizar testes com a água magnetizada tanto para a fabricação do concreto quanto para a sua cura submersa, analisando a trabalhabilidade e a resistência à compressão aos 7, 14 e 28 dias. Os resultados obtidos com a magnetização da água de amassamento no concreto são positivos, pois demonstram um aumento considerável da sua trabalhabilidade, podendo-se reduzir a quantidade de cimento através da redução de água no traço, consequentemente gerando uma maior economia de dinheiro e contribuindo para questões de sustentabilidade. A resistência à compressão se mostrou na maioria dos casos superior a do concreto produzido com água normal, mesmo que os valores tenham sido pequenos, mas já condiz com algumas literaturas, necessitando de futuras pesquisas, pois a ciência da magnetização da água não é exata.

En el analisis y diseno de estructuras de concreto reforzado es utilizado el modulo de elasticidad (Modulo de Young) del concreto Ec, parametro relacionado con la resistencia a compresion del mismo. En Colombia, el modulo de elasticidad usado en el diseno estructural esta basado en los valores recomendados en la “Norma Sismo Resistente de 1998 (NSR-98)”. Para el caso colombiano se tiene un valor medio a utilizar sin considerar el origen del agregado, el cual esta definido en el NSR-98 por la ecuacion '500,12ccfE=(en kg/cm2). Sin embargo, son varias las ecuaciones que se han planteado en diferentes paises para estimar Ec. En el presente estudio se analizaron resultados de 611 especimenes de concreto preparados en plantas concreteras del area metropolitana de Bucaramanga (Colombia), respetando que la muestra seleccionada correspondiera a una resistencia de 210 kg/cm2. Los datos obtenidos se utilizaron para evaluar las ecuaciones propuestas para estimar el Ec del concreto muestread...

Numerous environmental problems and natural disasters have occurred due to high extraction of natural resources, Now researchers are focused on recycled materials for future developments. Recycled glass could be easily used in concrete, moreover its low cost, availability and simple process makes it eco-friendly and low-cost material that can be significantly applied in the construction industry. Therefore, primary aim of this research is to explore the applicability and adaptability of glass as a recycled material for concrete. Various properties of concrete made from glass coarse aggregates were analysed. A total number of 66 cubes were casted and tested for compressive strength, and 18 cylinders were casted and tested for split tensile strength and slump test was also performed. the results have shown that upto 10% of replacement of Coarse aggregate by RGA will not affect strength of concrete significantly and hence This paper intends to recommend that recycle glass can be used as an alternate coarse aggregate in concrete and will also be beneficial in waste management.

The addition of standard intermediate aggregate (IA) content may provide desired intermediate-sized aggregate particle (ISA) content that can enhance the aggregate gradation and predictability of the aggregate packing (k) and Portland cement concrete consistency. This study evaluates the effect of the ISA on the average variation between traditional dry-rodded and vibrated aggregate packing (Δk) results. Gradation factors were determined and plotted on the Modified Coarseness Factor Chart (MCFC) seeking to identify Δk-ISA content correlations and to investigate a relationship between ISA and concrete consistency. The aftermath of 96 tests were grouped in three intervals determined by gradation curve resemblance. The results indicated that when ISA was between 25 and 27 % (by weight), Δk reached its lowest level: 1.7 %. Also, the optimized gradation (B6) displayed ISA = 26 % and fell right at the center of the MCFC's Workability Box (WB). Lastly, aggregate blends with 10 < IA < 11 % (by weight) translated into 25 < ISA < 27 % and surrounded the WB of the MCFC. The study concludes that adding IA to concrete can increase adherence between concrete design and placement, besides providing better consistency to concrete.

ABSTRACT This paper presents a study for utilizing cement-bypass dust; an industrial solid waste that poses a great threat to the environment, to produce a low permeability cutoff wall. The cutoff mixture is prepared by mixing sand with specific amounts of silt, bentonite, cement bypass, and adding enough water to achieve the adequate slump required for workability. The compressive strength of the mixtures ranged from 0.28 to 1.5 MPa, and the permeability ranged from 1.6 × 10−7 to 1 × 10−8 m/s. The results show that cement bypass can effectively replace ordinary Portland cement to produce an economical cutoff wall with properties suitable for most geotechnical applications.

The most important challenge for concrete technologists is to improve the properties of concrete. In the last two decades, in Russia and China, a new technology, called magnetic water technology, has been used in the concrete industry. In this technology, by passing water through a magnetic eld, some of its physical properties change and, as a result of such changes, the number of molecules in the water cluster decrease from 13 to 5 or 6, which causes a decrease in the water surface tension. Using magnetized water in concrete mixtures causes an improvement in the workability and compressive strength of concrete. Also, this processed water causes a reduction in the cement content required for the speci ed compressive strength value. In this research, in the concrete laboratory of Sahand University of Technology, the e ects of magnetic water on some mechanical properties of high strength concrete, such as workability and compressive strength, have been studied. For the production of m...