Search results for "concrete"
showing 10 items of 262 documents
Creep of polymer concrete in the nonlinear region
2000
Two polyester-based polymer concretes with various volume content of diabase as an extender and aggregate are tested in creep under compression at different stress levels. The phenomenological and structural approaches are both used to analyze the experimental data. Common features of changes in the instantaneous and creep compliances are clarified, and a phenomenological creep model which accounts for the changes in the instantaneous compliance and in the retardation spectrum depending on the stress level is developed. It is shown that the model can be used to describe the experimental results of stress relaxation and creep under repeated loading. Modeling of the composite structure and su…
Pumice concrete for structural wall panels
2003
Some properties of lightweight pumice stone concrete (LWPSC) are discussed, on account of a possible structural use of this material. Then the results of an experimental investigation are described, in order to show that pumice can really be considered an alternative to common artificial lightweight aggregates, taking into account the performance pointed out by loading tests carried out on structural systems made of LWPSC. Three different kinds of reinforced wall panels were made using LWPSC, lightweight expanded clay concrete and normal weight concrete; then their structural responses under horizontal cyclic and constant vertical forces were compared, above all with reference to lateral st…
Compressive behavior of FRP externally wrapped R.C. column with buckling effects of longitudinal bars
2018
Abstract In this paper, a calculation model to simulate the compressive behavior of R.C. columns with square cross-sections externally wrapped with FRP, including buckling effects of the longitudinal bars and reduction of the confinement pressure induced by the buckled compressed bars, is presented and discussed. The model distinguishes the cases of corner and side bars, calculating the different critical lengths and the critical loads. The Teng et al. (2009) model was adopted to predict the compressive behavior of FRP-confined concrete, and the Dhakal and Maekawa (2002) model was taken into account to predict the compressive behavior of longitudinal bars. The critical length and critical s…
Influence of axial force and corrosion on failure of prestressed concrete structures considering M-V interaction
2021
Abstract Existing prestressed concrete structures suffer from degradation of prestressing for two main reasons: a defect of the sheath infills (cement grout) of bonded tendons, and corrosion of steel strands. These two causes, often concomitant, lead to a reduction over time of the effectiveness of initial prestressing, in addition to the ordinary tension losses due to concrete shrinkage and creep, and to steel relaxation. In many cases a consequence of bad grouting in bonded tendons is that the structure shows an intermediate behavior between that of external prestressing and that of internal bonded prestressing. This, added to damage to wires due to corrosion, makes it essential for the d…
Improvements in aggregate-paste interface by the hydration of steelmaking waste in concretes and mortars
2019
[EN] The objective of the experimental work is to study the mechanical properties in self-compacting concretes (SCC) in which part of the limestone aggregate has been replaced by granulated blast furnace slag (GBFS) in different percentages ranging from 0% to 60%. The results show that at early ages the SCC with the largest content in slag tend to have lower compressive strengths due to the poor compacting of the aggregates, although in the long-term their strength increases due to the reactivity of the slag. In fact, at the age of 365 days, the mortars made with the substitution of 50% of cement by ground GBFS reach compressive strength similar to that of the mortar made with 100% of cemen…
Heterogeneous crystallization of zinc hydroxystannate on galvanized steel for enhancing the bond strength at the rebar/concrete interface
2021
Abstract Zinc hydroxystannate (ZnSn(OH)6) coatings were deposited on galvanized carbon steel samples by an electroless heterogeneous crystallization process. Structural and morphological features of the coatings as a function of the immersion time were determined by X-ray diffraction, Raman Spectroscopy and Scanning Electron Microscopy revealing the presence of truncated octahedrons of crystalline ZnSn(OH)6. Electrochemical characterization in a simulated concrete pore solution without and with addition of chloride ions proved that the cathodic protection is preserved and that ZnSn(OH)6 improved the corrosion resistance of the rebars. Pull-out tests demonstrated an enhanced bond strength at…
Behavior of fiber-reinforced concrete columns under axially and eccentrically compressive loads
2010
An experimental investigation into the behavior of 16 short, confined, reinforced concrete columns with and without steel fibers was carried out. The columns with square sections had a concrete core 165 x 165 mm (6.49 x 6.49 in.) at the midsection and were hunched at the ends to apply eccentric loading and prevent boundary effects. The specimens were tested to failure at different strain rates under two loading schemes: concentric compression and eccentric compression with a constant eccentricity. The axial load and axial strains were obtained to evaluate the effects of the presence of steel fibers, the thickness of the cover concrete, and the eccentricity of the applied axial load. The com…
Stainless steel grids for confinement of clay brick masonry columns
2016
This work presents the results of an experimental investigation on the behavior of 21 solid clay brick columns internally strengthened by stainless steel grids placed in the horizontal joints of mortar. This reinforcing technique can be applied as a constructive technique for new construction or as a retrofitting technique for existing structures (old structures to be reconstructed by original constructive method and internal reinforcement). Monotonic compressive loading tests were carried out under concentric and eccentric load. The effects of different numbers of steel grids and eccentricity of the external load were examined. Also, a detailed characterization of the constituent materials…
Computational Study of Failure of Hybrid Steel Trussed Concrete Beams
2017
This study investigates the failure behavior of hybrid steel trussed concrete beams (HSTCBs) under three-point bending through a series of finite-element (FE) simulations. The FE model employs well-established constitutive relations of concrete and steel with a simplified contact condition between the concrete and steel truss. The numerical model is compared with existing experimental data as well as a FE model that uses a more sophisticated concrete-steel interfacial model. The comparison shows that the present model is able to capture various failure mechanisms of the beam and its peak load capacity. The model is applied to investigate the behavior of a set of HSTCBs of different sizes, w…
Flexural and Shear Resistance of Steel Fiber–Reinforced Lightweight Concrete Beams
2014
In the present paper an analytical model is proposed that is able to determine the shear resistance of lightweight reinforced concrete beams with longitudinal bars, in the presence of reinforcing steel fibers. The model is based on the evaluation of the resistance contribution resulting from beam and arch actions. For the resistance contribution of main bars in tension, the residual bond adherence of steel bars and the crack spacing of reinforced concrete (RC) beams in the presence of fibers are considered. The contribution in terms of postcracking resistance in the tension zone of the beams is also included. The model was verified on the basis of experimental data available in the literatu…