Residual Repeated Impact Strength of Concrete Exposed to Elevated Temperatures

Abstract

Portland cement concrete is known to have good fire resistance; however, its strength would be degraded after exposure to the temperatures of fire. Repeated low-velocity impacts are a type of probable accidental load in many types of structures. Although there is a rich body of literature on the residual mechanical properties of concrete after high temperature exposure, the residual repeated impact performance of concrete has still not been well explored. For this purpose, an experimental study was conducted in this work to evaluate the effect of high temperatures on the repeated impact strength of normal strength concrete. Seven identical concrete patches with six disc specimens each were cast and tested using the ACI 544-2R repeated impact setup at ambient temperature and after exposure to 100, 200, 300, 400, 500 and 500 °C. Similarly, six cubes and six prisms from each patch were used to evaluate the residual compressive and flexural strengths at the same conditions. Additionally, the scattering of the impact strength results was examined using three methods of the Weibull distribution, and the results are presented in terms of reliability. The test results show that the cracking and failure impact numbers of specimens heated to 100 °C reduced slightly by only 2.4 and 3.5%, respectively, while heating to higher temperatures deteriorated the impact resistance much faster than the compressive and flexural strengths. The percentage reduction in impact resistance at 600 °C was generally higher than 96%. It was also found that the deduction trend of the impact strength with temperature is more related to that of the flexural strength than the compressive strength. The test results also show that, within the limits of the adopted concrete type and conducted tests, the strength reduction after high temperature exposure is related to the percentage weight loss.

Experimental Study on Self Compacting Fibrous Concrete Comprising Magnesium Sulphate Solution Treated Recycled Aggregates

“…The mixes with high volume replacements of NA with RCA exhibited wider cracks, which might have been due to the effortless delamination of the newly formed mortar from the adhered mortar available on the surface of RCA due to its inferior quality. The specimens without steel fibres tended to split into pieces at the stage of failure [ 64 , 65 , 66 , 67 ], whereas the specimens incorporating steel fibres failed without splitting [ 68 , 69 , 70 , 71 ]. This is attributed to the bridging mechanism of steel fibres with the concrete, which improved the interlocking between the particles in the matrix [ 72 , 73 ].…”

Impact Resistance of Functionally Layered Two-Stage Fibrous Concrete

“…FRC is the potential for enhancing impact-resistant applications in essential constructions such as flooring, nuclear storage, and airplane pavements [5]. An intense explosion may not harm the buildings, but repeated collisions can cause damage and collapse [6]. Increasing made-made risks have forced the construction of high impact resistance infrastructure subjected to repeated crashes and explosions [7].…”

“…The increased Q1 and Q2 due to a higher fibre dose (2.4%) resulted in improved ductility. 6 11.1 6.7 16.9 9.0 11.5 9.7 9.4 7.5 13.5 6.6 13.0 6.0 15.0 10.1 9.9 6.9 11.5 5.9 16.6 9.0 13.8 8.9…”

Numerical Analysis of Seismic Performances of Post-Fire Scoria Aggregate Concrete Beam-Column Joints

“…So far, extensive experimental research has been conducted on the mechanical properties and seismic performance of structural components after exposure to fire. Al-Ameri conducted an experimental study to evaluate the effect of high temperatures on mechanical properties and repeated impact strength of normal strength concrete [3]. The results revealed that the compressive strength was increased by less than 2% after exposure to 100 °C, while it reduced to approximately 50% of the original strength at 600 °C; the impact strength decreased sharply by 74.2% after exposure to 200 °C.…”