Influence of polypropylene and steel fibres on thermal spalling and physical-mechanical properties of concrete under different heating rates

International audienceAbstractThis study investigates three concrete compositions: a control concrete, a reinforced concrete containing 60 kg/m3 of steel fibres, and a hybrid concrete containing 60 kg/m3 of steel fibres and 0.75 kg/m3 of polypropylene fibres. Cylindrical specimens were manufactured and subjected to two heating rates (10 °C/min and the ISO 834 fire standard) to study their spalling sensitivity. Moreover, unidirectional heat transfer and pressure measurements were performed on slabs heated at 10 °C/min to 600 °C. To understand the influence of fibres on spalling processes more clearly, the thermal properties were studied during heating and cooling: the gas permeability, compressive strength, and Young’s modulus of specimens were measured after a heating and cooling cycle at 0.5 °C/min. The results show that the spalling phenomenon was more severe for cylindrical specimens than for slabs. The addition of 60 kg/m3 of steel fibres had an unfavourable influence on spalling, especially during the ISO 834 fire test. The addition of 0.75 kg/m3 of polypropylene fibres allowed the concretes containing steel fibres to avoid spalling, regardless of the thermal loading conditions

Influence of elevated temperature on properties of radiation shielding concrete with electric arc furnace slag as coarse aggregate

The development of value-added materials from by-product of the steel-making process can promote sustainability in construction to move towards a circular economy. The use of Electric Arc Furnace (EAF) steel slag as heavyweight coarse aggregate to develop sustainable radiation shielding concrete could provide both technical and economic benefits with less environmental impact. This contribution investigates the behaviour at high temperature of a sustainable radiation shielding concrete. Thermal behaviour of EAF slag concrete was compared to another heavyweight concrete made of barite aggregates and to a normal-weight concrete. On one hand, the thermal stability of the three different aggregates was determined via simultaneous Thermogravimetry and Differential Scanning Calorimetry analyses and visual observations after 10 \ub0C/min heating. On the other hand, the evolution of thermal conductivity of concretes during heating, the residual mechanical properties and the assessment of potential spalling occurrence were investigated. Stereo-microscope and Scanning Electron Microscope pictures provide additional explanations by showing the paste-aggregate interface after heating at 450 \ub0C. The results indicated that EAF concrete displayed less strength reduction at increasing temperature. This improved behaviour is attributed to both the strong bond between the paste and the aggregates, and the better thermal behaviour of the EAF slag aggregates compared to barite aggregates

Durability Analysis of Natural Lime Concrete

Concrete is known to be durable and dependable material since it is resistance to weathering action and chemical attacks while maintaining its engineering properties. However, carbon dioxide produced by the cement industries had caused severe environmental pollution. To minimize carbon dioxide emission into the atmosphere, eggshell wastes are treated as partial cement replacement in this study. The eggshell was oven-dried at 105.5 °C for 24 h before grinding it into powder passing through sieve size 45 µm. Eggshell powder was used as partial cement replacement at 5, 10, 15 and 20%. The performance of the concrete mix was evaluated against control concrete mix. The specimens were tested on acid attack and sulphate attack. The concrete specimens were prepared in the form of cubes and then subjected to water curing for 28 days before immersed in sulphuric acid solution for 1800 h and sodium sulphate for 50 weeks respectively. From the analysis, it is observed that reduction of compressive strength of the concrete cubes for the acid attack and sulphate attack reduce gradually when the eggshell powder increase