Behaviour of Fly ash and GGBS based Monoblock Prestressed Geopolymer Concrete Composite sleepers

Abstract

In railways, Prestressed concrete is generally adopted for the design of railway sleepers as the material behaves in a ductile manner within certain stress limits in addition to the benefits of having the reduced size of the member. Monoblock Prestressed Concrete (PSC) sleepers because of its enormous use demands a huge amount of cement and this factor is of vast economic importance in the railway infrastructure. Considering the environmental threats resulted due to the manufacturing of cement, activation of materials consisting of SiO2 and Al2O3 in an alkaline medium is considered as an interesting alternative to produce cementitious materials. The likelihood of utilizing fly ash and Ground Granulated Blast Furnace Slag (GGBS) for manufacturing Monoblock Prestressed geopolymer concrete sleepers as per the specifications of Indian Railway Standard (IRS) Specification for sleepers without using cement was explored. Four trial mixes were used by varying the fly ash and GGBS contents for example 90% and 10% (F90 G10), 80% and 20% (F80 G20), 70% and 30% (F70 G30) and 60% and 40% (F60 G40) for evaluating the strength properties like Strength under compression, Split tensile strength and strength under flexure. Through test results, it was found that strength is proportional to the quantity of GGBS used in the mixes. Two sleepers were cast using the mix F70G30 and the static bending strength tests were conducted on the pretensioned geopolymer concrete sleepers. Moment of resistance (MR) test and Moment of Failure (MF) tests were carried out for Centre Top and rail seat bottom loading conditions. From the strength tests conducted on sleepers, it can be concluded that the sleepers cast using the alkali activation process of GGBS and cement without cement can meet the requirements of IRS Specifications for Pretensioned sleepers and fly ash and GGBS could be considered as a sustainable substitute material for cement for sleepers.