Experimental studies were carried out using sandwich composite panel specimens, consisting of both polyurethane foam core (PUF) and aramid honeycomb core (Nomex) type constructions. These specimens were subjected to impact damage at energy levels ranging between 7.56 and 15.6 J. A ply-drop-patching technique was employed to repair the impact damaged sandwich specimens. The undamaged (virgin), impact damaged, and repaired specimens were then subjected to flexural (four point bending) and edgewise compression tests and strength recoveries were measured to determine the efficacy of the repair technique employed. In flexure, strength recoveries of up to 97% in PUF core and 90% in honeycomb core sandwich specimens were realized after repair, whereas in compression, the corresponding values were up to 90% in PUF core and 88% in honeycomb core sandwich specimens. A repair effectiveness factor (Ref) has been conceived and introduced to quantify the efficiency of the repair technique. Further, the repair quality was assessed using a simple NDT method prior to subjecting the sandwich specimens for destructive tests.

Concrete elements exposed to fire undergo temperature gradients and, as a result, the surface layers spall, exposing steel reinforcement. Relatively few studies have been undertaken on heat-induced changes in fly ash concrete. The structural property of concrete that has been studied most widely as a function of heat exposure is compressive strength. Less attention has been given to flexural strength as influenced by heat exposure. Therefore, to investigate the effect of temperature on the flexural strength of fly ash concrete, the present study was carried out with M28, M33 and M35 grades of concrete. Concrete specimens 100 mm × 100 mm × 500 mm with partial replacement of cement by fly ash (10%, 20% and 30% replacement levels) were heated to 100°C, 200°C and 250°C for 1 h, 2 h and 3 h duration in an electric oven. The specimens were tested for flexural strength in the hot condition immediately after removing from the oven. The fly ash concrete showed consistently the same pattern of behaviour as that of concrete without fly ash under elevated temperatures during flexure. The fly ash concrete with fly ash content up to 20% showed improved performance compared with the specimens without fly ash by retaining a greater amount of its strength.

The present study is aimed to study the effect of elevated temperatures ranging from 50 to 250°C on the compressive strength of high-strength concrete (HSC) of M60 grade made with ordinary portland cement (OPC) and pozzolona Portland cement (PPC). Tests were conducted on 100 mm cube specimens. The specimens were heated to different temperatures of 50, 100, 150, 200 and 250°C for three different exposure durations of 1, 2 and 3 h at each temperature. The rate of heating was maintained as per ISO-834 temperature–time curve for standard fire. After the heat treatment, the specimens were tested for compressive strengths. Test results were analysed and the effects of elevated temperatures on PPC concrete were compared with OPC concrete. The PPC concrete exhibited better performance than OPC concrete.

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The present study investigated the effect of elevated temperatures ranging from 50 to 250°C on the tensile strength (splitting and flexural) of high-strength concrete (HSC) made with Portland cement (PC) and pozzolana Portland cement (PPC), for application in the chemical and metallurgical industries or thermal shielding of nuclear power plants. Tests were conducted on 150 mm diameter cylindrical specimens and 100 mm × 100 mm × 500 mm beam specimens. The specimens were heated to different temperatures of 50, 100, 150, 200 and 250°C for three different durations of 1, 2 and 3 h at each temperature. After the heat treatment, the specimens were tested for both splitting and flexural tensile strengths. Test results were analysed and the effects of elevated temperatures on PPC concrete were compared with PC concrete. The PPC concrete exhibited better performance than PC concrete.