Effects of Magnetite Aggregate and Steel Powder on Thermal Conductivity and Porosity in Concrete for Nuclear Power Plant

Abstract

Among many engineering advantages in concrete, low thermal conductivity is an attractive property. Concrete has been widely used for nuclear vessels and plant facilities for its excellent radiation shielding. The heat isolation through low thermal conductivity is actually positive for nuclear power plant concrete; however the property may cause adverse effect when fires and melt-down occur in nuclear vessel since cooling down from outer surface is almost impossible due to very low thermal conductivity. If concrete containing atomic reactor has higher thermal conductivity, the explosion risk of conductive may be partially reduced. This paper presents high thermally conductive concrete development. For the work, magnetite with varying replacements of normal aggregates and steel powder of 1.5% of volume are considered, and the equivalent thermal conductivity is evaluated. Only when the replacement ratio goes up to 30%, thermal conductivity increases rapidly to 2.5 times. Addition of steel powder is evaluated to be effective by 1.08~1.15 times. In order to evaluate the improvement of thermal conductivity, several models like ACI, DEMM, and MEM are studied, and their results are compared with test results. In the present work, the effects of steel powder and magnetite aggregate are studied not only for strength development but also for thermal behavior based on porosity.

Fire Performance of Heavyweight Self-Compacting Concrete and Heavyweight High Strength Concrete

“…Compared to barite aggregate, magnetite has lower thermal conductivity, however, it still has a higher thermal conductivity than normal aggregate. As reported by the authors of Reference [ 37 ], the thermal conductivity of magnetite aggregate is in the range of 6–23 W/m.K, while for normal aggregate it is in the range of 1.3–2.8 W/m.K at ambient temperature which would explain the minor crack propagation for HWSCCs at higher temperatures (i.e., 900 °C) compared to SCC. Higher thermal conductivity results in a better heat transfer, and consequently will reduce thermal stresses within the concrete, which are originated from the temperature gradients between the inner and outer surfaces of the concrete structure exposing to high temperature.…”

“…Moreover, for HWSCC75 and HWSCC100 the initial increase in the elastic modulus occurred at a higher temperature compared to the control SCC sample and HWSCC50. A higher thermal conductivity of magnetite aggregates than cement and air in the filling of pores within the cement matrix can well explain the more significant initial increase of modulus of elasticity for HWSCCs and HWHSC50 [ 37 ]. Increasing the magnetite content, especially with a smaller particle size, leads to the filling of pores and a more compact microstructure.…”

Multifaceted Analysis of the Thermal Properties of Shielding Cement-Based Composites with Magnetite Aggregate

“…Research on the influence of magnetite aggregate on concrete porosity was conducted, among others, by [ 37 , 38 ]. Jóźwiak-Niedźwiedzka et al [ 37 ] showed that the total pore volume evaluated by MIP was influenced by the content of magnetite aggregate in concrete.…”

Uticaj Sadržaja Vlage Na Koeficijent Toplotne Provodnosti Betona

“…[6] Овај тип бетона има велику примену у изградњи нуклеарних електрана, због високог нивоа заштите од зрачења. Услед повећаног ризика од експлозија, када долази до великог ослобађања енергије, неки аутори предлажу и додатно повећање топлотне проводности оваквих бетона [8]. У састав нормалних бетона најчешће улазе компактни агрегати, па њихова порозност зависи највише од процеса хидратације употребљеног цемента.…”