Non-Destructive Multi-Method Assessment of Steel Fiber Orientation in Concrete

Integration of fiber reinforcement in high-performance cementitious materials has become widely applied in many fields of construction. One of the most investigated advantages of steel fiber reinforced concrete (SFRC) is the deceleration of crack growth and hence its improved sustainability. Additional benefits are associated with its structural properties, as fibers can significantly increase the ductility and the tensile strength of concrete. In some applications it is even possible to entirely replace the conventional reinforcement, leading to significant logistical and environmental benefits. Fiber reinforcement can, however, have critical disadvantages and even hinder the performance of concrete, since it can induce an anisotropic material behavior of the mixture if the fibers are not appropriately oriented. For a safe use of SFRC in the future, reliable non-destructive testing (NDT) methods need to be identified to assess the fibers’ orientation in hardened concrete. In this study, ultrasonic material testing, electrical impedance testing, and X-ray computed tomography have been investigated for this purpose using specially produced samples with biased or random fiber orientations. We demonstrate the capabilities of each of these NDT techniques for fiber orientation measurements and draw conclusions based on these results about the most promising areas for future research and development.

Study on the Effect of Nano-Silica in Mechanical and Durability Properties of Concrete with Steel Fiber

This study presents experimentally the combined effect of using Nano-silica (NS) and steel fibers (SF) on the mechanical properties of hardened concrete. NS is used as partial cement replacement by different percentages, and SF is used as volume substitution by different percentages. Splitting tensile strength, modulus of elasticity, and flexural strength are evaluated using different combinations between NS and SF. Significant improvement in the mechanical properties of concrete is observed on using NS due to its high pozzolanic activity. The Optimum content of SF is improved splitting tensile strength with different percentages respectively compared to without either NS or SF. Utilizing NS with SF leads to improving modulus of elasticity compared to without either NS or SF. Flexural strength is doubled for using NS and SF compared to without NS and SF.

Effect of Ether-Typed Polycarboxylate Superplasticizer on the Adsorption, Rheology and Concrete Properties

This article disclosed the influence of acid-ether ratio, n(SH)/n(IPEG), and n(APS)/n(IPEG) on adsorption and fluidity performance. The optimum synthetic parameters of acid-ether ratio, n(SH)/n(IPEG) and n(APS)/n(IPEG) were 0.5, 0.35 and 0.05, respectively. The rheology fitting equation was τ= 719.55γ+ 1834.54. And the correlation coefficient was 0.9843. The cement paste conformed to the law of pseudoplastic fluid. The preferred PCE-11 had excellent performance in freshly mixed and hardened concrete.

Analysis of High Strength Concrete processed from Recycled Concrete Aggregates

As everyone is aware of the fact that Natural Coarse Aggregate (NCA) is the main constituent of traditional concrete mixes. Whenever an existing concrete structure is demolished, it produces smashed concrete waste in the large amount. Concrete waste give rise to negative effects on the environment. To evade the environmental pollution and mark effective reuse of the concrete waste as Recycled Aggregates in the place of NCA. This operative initiative provides an opportunity to reduce air pollution and soil exploitation to some extent. Such concrete is sustainable in nature and also eco-friendly to the environment. Also, such waste material will lower the usage of naturally occurring stone to produce NCA and thus various natural energy resources will be safeguarded. This study covers the suitability norms for a material to be used for Recycled Aggregate. In this study the natural aggregate is replaced with recycled aggregate in the different percentages (0%, 25%, 50%). When percentage of recycled aggregate mixed in the fixed proportion as percentage replacement to natural aggregates, it imparts improvement in the property of fresh as well as hardened concrete like, compressive strength & split tensile strength. Laboratory results of this research indicates that the value of compressive strength, tensile strength stress-strain curve & NDT of these mixes drives on decreasing, but at the 25% replacement level, it achieves target mean strength. Hence, for the fundamental concrete mix Natural Coarse Aggregate can be efficiently replaced by the Recycled Aggregate to the range of 25%. Keywords: Concrete, Recycled aggregate, Natural Coarse Aggregate (NCA), Compressive Strength, Tensile strength, , NDT, Stress-Strain Curve

Effect of Kota Stone Slurry Powder in Fresh and Hardened Concrete: A Review

Concrete is highly used construction material with cement being its major ingredient. Also, the demand for good quality of concrete is increasing because of the fast-growing urbanization. But there are certain problems associated with the manufacturing of cement. One of the major problems being production of carbon dioxide causing pollution in environment, the manufacturing of cement is quite expensive and it also leads to the depletion of resources. In order to curtail the consumption of cement, it has become inevitable to replace cement by certain amount with substituent materials that are cheaper to produce in order to lower down the financial cost of concrete production by some extent. The review paper, elaborates many properties of concrete by the inclusion of Kota stone slurry after evaluating several research papers. The following paper discusses numerous properties of concrete including workability, compressive strength, split tensile strength, water absorption and modulus of elasticity. The paper demonstrates that when used appropriately, inclusion of Kota stone slurry in concrete had a positive impact on concrete by increasing the strength and durability.

Evaluation of Eco-Efficient Concretes Produced with Fly Ash and Uncarbonated Recycled Aggregates

The fabrication of conventional concrete, as well as remains from demolition, has a high environmental impact. This paper assessed the eco-efficiency of concrete made with uncarbonated recycled concrete aggregates (RCA) and fly ash (FA). Two concrete series were produced with an effective water/cement ratio of 0.50 (Series 1) and 0.40 (Series 2). In both series, concretes were produced using 0% and 50% of RCA with 0%, 25% and 50% FA. After analysing the compressive strength, and carbonation and chloride resistance of those concretes, their eco-efficiency based on the binder intensity and CO2-eq intensity was assessed. We found that the use of 50% uncarbonated RCA improved the properties of concretes produced with FA with respect to using natural aggregates. The concrete made of 25% FA plus RCA was considered the most eco-efficient based on the tests of compressive, carbonation and chloride properties with the values of 4.1 kg CO2 m−3 MPa−1, 76.3 kg CO2 m−3 mm−1 year0.5 and 0.079 kg CO2 m−3 C−1, respectively. The uncarbonated RCA improved carbonation resistance, and FA improved chloride resistance. It can be concluded that the use of 50% un-carbonated RCA combined with FA considerably enhanced the properties of hardened concrete and their eco-efficiency with respect to concretes produced with natural aggregates.