Prestressed concrete (PC) sleepers are used in modern railway systems worldwide. Although the PC sleepers are durable under harsh environmental conditions, frequent cracks can be found hindering the railway's capacities. This article investigates an improvement of placing steel stirrups in shear deficient PC sleepers commonly used in railways of Thailand. PC sleepers with a cross-section of 258 Â 205 mm 2 varied with five different stirrup's ratios were tested under a three-pointed bending load to observe the improvement of shear resistance. From the experimental results, the peak load of PC sleepers with stirrups can be enhanced from 14.1% to 21.2%, whilst the failure deformation can also be enhanced from 87.5% to 176.6%, compared with PC sleeper without any stirrup. With increasing stirrup's ratio, failure modes of PC sleepers were shifted from brittle shear to ductile flexural failures. Moreover, the PC sleepers with deformed-bar stirrups exhibited better bond interfaces than that with rounded-bar. Then, the proper stirrup's ratio and type of steel stirrups are recommended to enhance the shear resistance of the PC sleeper. In addition, a finite element analysis results based on advanced constitutive models and the fixed-cracking approach showed good agreement with the results from experiment.

Low density of the light-weight cement blocks offers an advantage in terms of dead load reduction, which is advantageous in structural design-reduction of size and numbers of load-carrying structural components is possible. Production of cement blocks, however, generally requires Ordinary Portland Cement (OPC) which creates harmful environmental impacts. Utilization of waste as alternative raw materials for cement production is a route to alleviate the problem. This research aims at synthesizing eco-friendly cement-like material for production of light-weight cement blocks. The cement-like material were prepared from eggshells, cockleshells, and rice husk ash (RHA). With high content of calcium oxide and silica, eggshells and cockleshells are potential sources of calcium, whereas RHA is a good source of silicon. Additionally, a fuel-efficient solution combustion technique was employed in synthesis of the cement-like material. Phase identification analysis of the synthesized powder indicated that tri-calcium silicate (C3S), di-calcium silicate (C2S), tri-calcium aluminate (C3A),and tetra-calcium alumino ferrite (C4AF), which are main constituents of OPC, were obtained. To fabricate eco-friendly light-weight cement blocks, the synthesized cement-like material were mixed with cement, water, and additional RHA and cast into blocks. The optimal compressive strength and density of the cement blocks were in comparable range with the standard light-weight concrete defined by Thai Industrial Standards Institute (TISI) and American Concrete Institute (ACI 213,2001). With jute fiber reinforcement, enhanced compressive strength of 20% was achieved, while elimination of spalling after compression test was clearly evident, implying a more ductile failure.