Abstract
Surfaces of carbon fibre roving were modified by means of a low temperature plasma treatment to improve their bonding with mineral fines; the latter serving as an inorganic fibre coating for the improved mechanical performance of carbon reinforcement in concrete matrices. Variation of the plasma conditions, such as gas composition and treatment time, was accomplished to establish polar groups on the carbon fibres prior to contact with the suspension of mineral particles in water. Subsequently, the rovings were implemented in a fine concrete matrix and their pull-out performance was assessed. Every plasma treatment resulted in increased pull-out forces in comparison to the reference samples without plasma treatment, indicating a better bonding between the mineral coating material and the carbon fibres. Significant differences were found, depending on gas composition and treatment time. Microscopic investigations showed that the samples with the highest pull-out force exhibited carbon fibre surfaces with the largest areas of hydration products grown on them. Additionally, the coating material ingresses into the multifilament roving in these specimens, leading to better force transfer between individual carbon filaments and between the entire roving and surrounding matrix, thus explaining the superior mechanical performance of the specimens containing appropriately plasma-treated carbon roving.
Highlights
The development of carbon fibre (CF) reinforced concrete has attracted much attention in recent years due to the emerging possibility of designing and producing sophisticated, thin-walled concrete structures, with extraordinary mechanical performance, very high durability, and enhanced potential for free-form designs in comparison to steel bar reinforced concrete [1,2]
As the results show and as could be expected, this influence is higher in the case of pure oxygen; see Figure 4
The plasma treatment of carbon multifilament roving was successfully applied for enhancedthe interaction a mineral-based coating and a subsequently improved load
Summary
The development of carbon fibre (CF) reinforced concrete has attracted much attention in recent years due to the emerging possibility of designing and producing sophisticated, thin-walled concrete structures, with extraordinary mechanical performance, very high durability, and enhanced potential for free-form designs in comparison to steel bar reinforced concrete [1,2]. The mechanical properties of such carbon concrete composites deteriorate dramatically under elevated temperatures, especially in the case of exposure to fire, with the result that key construction markets are still closed to them. The load-bearing behaviour of the carbon concrete composite is strongly related to the properties of the polymer-based CF coating. These polymer coatings, possess very temperature-dependent mechanical properties. The storage moduli of the widely used thermoplastic or thermosetting polymers decrease to a great extent. This deterioration of the mechanical properties begins as early as when the specific glass transition temperature is reached. Silva et al [8] have demonstrated a sudden worsening of load-bearing behaviour above 400 ◦ C, due to deteriorated polymer coatings
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