ABSTRACT
A cable parameter related to the volume of effective non-combustible content, Ω, is proposed, which depends on the ratio of non-metallic, non-combustible component volume to non-metallic, combustible component volume, and the effective area of heat transfer within the cable during the combustion process. The correctness of the proposed cable parameter for circular cables is confirmed by tests and the determination of Spearman's correlation. High Spearman's correlation factors (close to -1) were obtained for total heat release and total smoke production as a function of the Ω cable parameter. The Ω cable parameter might be used in selecting cable samples for large geometric-scale fire testing within the same cable family.
ABSTRACT
The results of flexural tests of basalt fibre-reinforced cementitious mortars in terms of flexural strength and the occurrence of the bridging effect are summarised. Mixture proportions and curing conditions were altered for various series. The main parameters concerning mixture proportions were water to cement ratio (w/c), micro-silica and plasticiser addition and fibre dosage (1%, 3% and 6.2% by binder's mass). Various curing conditions were defined by different temperatures, humidity and time. The influence of the amount of water inside the pores of the hardened cementitious matrix on the flexural strength values, as far as the impact of the alkaline environment on basalt fibres' performance is concerned, was underlined. The designation of flexural strength and the analysis of post-critical deformations were also performed on the reference series without fibres and with the addition of more common polypropylene fibres. The bridging effect was observed only for the basalt fibre-reinforced mortar specimens with a relatively low amount of cement and high w/c ratio, especially after a short time of hardening. For the lowest value of w/c ratio (equalling 0.5), the bridging effect did not occur, but flexural strength was higher than in the case of non-reinforced specimens. Comparing mortars with the addition of basalt and polypropylene fibres, the former demonstrated higher values of flexural strength (assuming the same percentage dosage by the mass of the binder). Nevertheless, the bridging effect in that case was obtained only for polypropylene fibres.
ABSTRACT
Although fiber reinforced polymer (FRP) bars have proved their usefulness in the case of reinforced concrete flexural elements, there are still limited data on their performance in such structures under compression. Despite multiple benefits of using FRP bars as the reinforcement in concrete elements, their potential application as main reinforcement in compressed elements is still very controversial, mainly due to the limited amount of published research results. The presented work partly fulfills this knowledge gap. Two series of theoretical analyses-one based on the stress distribution in the cross-section and the second using the finite elements method (FEM)-with reference to the experimental results are presented. The analyses concern basalt FRP, glass FRP, and steel-reinforced concrete elements under axial compression. There are derived calculations of load-displacement relations and stress values in bars. Damage progression was analyzed as well. Main findings are as follows: (1) a good agreement between calculated failure loads and experimental results has been achieved; (2) potential negative influence of FRP reinforcement on the compressive capacity of the reinforced element should not be neglected; (3) nonlinear FEM analysis is useful in predicting the maximum value of load and damage zones; (4) stress values of only about 100 MPa (much lower than their compressive strength value) were obtained in non-metallic bars. The results might be useful for the further establishment of design rules.
ABSTRACT
Ventilation-controlled fires tend to be the worst for toxicity, because they produce large amounts of fire effluent containing high yields of toxic products. In order to examine the dependence of the amount of chosen few main combustion gases under ventilation-controlled conditions, a PVC-insulated copper electric wire with unknown composition (PVC filled with chalk) was studied by mean of a steady state tube furnace. For the tested wire, lower values of CO2 yields at different ventilation conditions were obtained than for the reference pure polymer unplasticized PVC and additionally tested pure LDPE, the yields were higher three times in the case of PVC and two times in the case of LDPE than those received for wire at the same ventilation conditions, which pointed out decreasing contribution of hyperventilation effect to human during cable fire. In contrast, higher values of toxic CO yields, four times higher, were obtained for the PVC-insulated electric wire rather than for the pure polymers. The maximum value of CO yield (0.57 g/g) was determined in the case of 5 L/min of primary airflow and decreased with increasing ventilation. The measured yields of hydrocarbons were similar to the reference values except for the equivalence ratio f = 0.27, where hydrocarbon yield was equal to 0.45 g/g. The HCl yield of fire effluents from the PVC-insulated wire was shown to be independent of ventilation conditions. The corrosive reaction between copper and the HCl species and the flame-retardant mechanisms of the additives, caused the lower values of HCl in the fire effluent of the PVC-insulated copper wire than for pure polymer.
