No abstract

In recent times, there has been increased interest in using various types of fibres in the cement-based materials industry. This work thus aims to investigate the possibility of improving the mechanical properties of mortar samples by using available and cheap polypropylene fibre with the aid of a microwave curing technique. For this purpose, 5×5×5 cm cubes of mortar containing different percentages and lengths of polypropylene fibres were cast and then subjected to various ranges of curing time under microwaves. Compressive strength, direct tensile strength, and density tests were conducted on reference mortar (specimens without fibres) and mortar reinforced with polypropylene fibre specimens at various ages (3, 7, and 28 days) of curing. The results showed a marginal decrease in the compressive strength against an increase in the direct tensile strength as fibre content increased. All mixes showed acceptable values for density against the reference mixes.

This paper examined the effect of the difference between the temperature of the two end of the body exposed to transient conduction heat transfer on the inception of thermal sensitivity and at different distances from the hot end of the sample. The study was based on the selection of a sample with a length of 15 cm and a fixed height of 1 cm. Four materials with different thermal properties were selected. One end of the model was exposed to three different temperatures (75, 125, and 175) oC. The other end of the sample was placed under a convection heat transfer at 25 oC. To adopt an inception indicator of thermal sensitivity of the sample when exposed to transient heat transfer, (26) oC was used because it is the nearest temperature to the initial condition of the sample. Four points were selected on different distance from hot end along the sample. The hot end temperature was also adopted as an indicator to measure the effect of the temperature difference for two body ends as the other end is subject to constant transient heat transfer.   Determine the effect of the temperature difference   between two body ends exposed to transient heat transfer on the inception of thermal sensitivity is study target. The  results of this study showed  the reverse effect of the temperature difference   between two body ends  exposed to transient heat transfer on the inception of thermal sensitivity, this effect increases by increasing the distance from  hot sample end   and depressing of thermal diffusivity. The results also showed that the values of the Thermal sensitivity inception ranged between (0.43-17845) seconds according to the    distance from the hot end, its temperature, and the thermal diffusivity of sample materials for each case.