Optimization of the type and amount of polypropylene fibres for preventing the spalling of lightweight concrete subjected to hydrocarbon fire

Abstract

This paper presents the results from an experimental study on the optimum amount of polypropylene fibres to be used in lightweight high-strength concrete to prevent spalling when exposed to hydrocarbon fire, taking into consideration the characteristics of the lightweight aggregate, the water-to-cement ratio (W/C) of the mixtures, and the length and thickness of the fibres.Twelve different concrete mixtures were made. One block, 610x425x770 mm in size, was cast from each mixture and tested for fire resistance under hydrocarbon fire exposure. The temperature in the blocks during the test was recorded. After the test, the condition of the blocks was evaluated, and cores were taken for determining the residual compressive strength of the concrete.Results from the study show that close to 3.5 kg of the 20-mm polypropylene fibres per cubic meter of concrete is required to prevent the spalling of a low W/C lightweight concrete made with a silica fume-blended cement when subjected to hydrocarbon fire but that only 1.5 kg of the finer 12.5-mm fibres per cubic meter is sufficient.The amount of 20-mm fibres required to prevent spalling for a higher W/C of 0.42 is significantly less: of the order of 1.5 kg per cubic meter of concrete.The susceptibility of the concrete to spalling increases with the degree of absorption of the lightweight aggregate used in concrete.

Influence of length and dosage of polypropylene fibres on the spalling tendency and the residual properties of self-compacting concrete after heated at elevated temperatures

“…Spalling occurred above 500 • C for the mixtures NVC and SCC 1 and destroyed some cylindrical specimens. It was observed that relative splitting tensile strength f ct (T)/f ct (20) was reduced up to 300 • C following a similar path for all concretes. Among concrete mixtures tested, SCC2 and SCC5 were more susceptible in reducing their relative splitting tensile strength about 14-18%, at temperatures up to 300 • C. The other concretes presented a slight strength loss ranging from 3 to 9%.…”

“…A lot of research has been carried out in order to model the spalling tendency of HPC and to propose some alternative solutions such as different mixture proportions or use of materials that provide a passive or active protection against spalling. Among the solutions proposed, the addition of polypropylene fibres seems to be an effective one (15)(16)(17)(18)(19)(20). It was reported (21) that polypropylene melts at 160-168 • C whereas HPC spalls when the air temperature ranges between 190-250 • C.…”

The effect of polymer coated pumice to the stiffness and flexural strength of reinforce concrete beam

“…LWAC has been known offers various advantages due to its lower density [1], higher ratio of strength/weight [2], less conductivity thermal [3,4], better durability properties [5,6], fire resistance [7] and etc. The use of lightweight concrete reduce the size of columns, beams, wall and foundation which as well reducing the dead load and minimizing the damages of structures due to earthquake [8].…”

Experimental study of the effect of water to cement ratio on mechanical and durability properties of Nano-silica concretes with Polypropylene fibers

“…Authors [11][12][13] have shown that the behavior of concrete at high temperature can be improved by adding polypropylene fibres (with a ratio varying from 0.5 kg/m 3 -3 kg/m 3 ). The melting (160 o C-170 o C) and vaporization (350 o C) of polypropylene fibres generates not only new pores, but also creates microcracks at the tip of fibres connecting the already existing pores [14]. Ozawa and Morimoto [15] carried out permeability tests on high strength concretes (72 MPa) including 0.15% by volume of PPF.…”