3 research outputs found
Modelling and parametric study of the re-anchorage of ruptured tendons in bonded post-tensioned concrete
The contribution of ruptured tendons to the residual strength of bonded post-tensioned concrete structures is currently assessed based on pre-tensioned concrete bond models. However, this approach is inaccurate due to the inherent differences between pre-tensioned and post-tensioned concrete. In this paper, a non-linear 3D finite element model is developed for the re-anchoring of a ruptured tendon in post-tensioned concrete. The model is validated using full-field displacement measurement from 33 post-tensioned concrete prisms and previous experimental data on beams from the literature. The influence of different parameters was investigated, including tendon properties (i.e. diameter, roughness), duct properties (i.e. diameter, thickness, material), initial prestress, concrete strength, grout strength, grout voids, stirrups, and strands, on the tendon re-anchorage. The most influential parameters are found to be tendon and duct properties
Flyash Based Geopolymer Concrete – A State of the Art Review
Concrete usage around the world is second only to water. Ordinary Portland Cement (OPC) is conventionally used as the
primary binder to produce concrete. But the amount of carbon dioxide released during the manufacture of OPC due to
the calcinations of lime stone and combustion of fossil fuel is in the order of 600 kg for every ton of OPC produced. In
addition, the extent of energy requires to produce OPC is only next to steel and aluminum. On the other hand, the
abundant availability of fly ash worldwide creates opportunity to utilize (by – product of burning coal, regarded as a
waste material) as substitute for OPC to manufacture concrete. Binders could be produced by polymeric reaction of
alkali liquids with the silicon and the aluminum in the source materials such as fly ash and rice husk ash and these
binders are termed as Geopolymer. In Geopolymer Concrete, fly ash and aggregates are mixed with alkaline liquids such
as a combination of Sodium Silicate and Sodium Hydroxide. United Nation’s Intergovernmental panel on Climate
Change (IPCC) prepared a report on global warming during April 2007 which enlists various methods of reduction of
CO2 emissions into atmosphere. As per that report, unmindful pumping of CO2 into the atmosphere is the main culprit
for the climate change. Large volume of fly ash is being produced by thermal power stations and part of the fly ash
produced is used in concrete industry, low laying area fill, roads and embankment, brick manufacturing etc. The balance
amount of fly ash is being stored in fly ash ponds. Hence it is imperative on the part of Scientists and Engineers to devise
suitable methodologies for the disposal of fly ash. Disposal of fly ash has the objective of saving vast amount of land
meant for ash pond to store fly ash. Further, use of fly ash as a value added material as in the case of geopolymer
concrete, reduces the consumption of cement. Reduction of cement usage will reduce the production of cement which in
turn cut the CO2 emissions. Many researchers have worked on the development of geopolymer cement and concrete for
the past ten years. The time has come for the review of progress made in the field of development of geopolymer
concrete. Consequently 102 papers pertaining to the ingredients and technology of geopolymer concrete have been
reviewed in this state of the art paper