Prediction of fire resistance of reinforced concrete structures with polypropylene microfibre or fire protection

Introduction. The options and features of solving the actual problem of preventing explosive loss of integrity of concrete and ensuring the required fire resistance of reinforced concrete structures (RCS) through the use of polypropylene microfibre (PPMF) in concrete or structural fire protection products are considered.

Goal and objectives. Justification of the choice of effective methods to prevent explosive loss of concrete integrity and ensure the given fire resistance of structures. Organization and carrying out of fire tests of reinforced concrete columns and floor slabs under load in the presence and absence of PPMF in the concrete composition, as well as with the use of structural fire protection. Analysis of the results and variants of their practical use.

Methods. The fire resistance of columns and slabs was assessed by testing specimens under load in a fired furnace with additional thermocouple measurements. It was carried out using approved simple methods and programmes for calculating temperature fields in structures. The procedure for determining the thermophysical characteristics of structural fire protection materials in the operating temperature range was proposed.

Results. The results of unique fire experiments of load-bearing columns and slabs are presented and summarized. The effectiveness of the use of PPMF is demonstrated, as well as the role of fire protection preventing loss of integrity in structures and increasing their fire resistance and fire protection under standard and hydrocarbon exposure. Examples of the effective use of structural fire protection in the form of “PROZASK Firepanel” slabs and “IGNIS LIGHT” plaster are presented to ensure high fire resistance limits of concrete. In the course of a new series of reinforced concrete slabs tests, for the first time carried out under hydrocarbon mode of exposure, it was found that when using PPMF, the time of reaching the limit state of specimens exceeds 120 minutes, and when using structural fire protection — 240 minutes. The possibility of recalculation (including reduction) of fire protection thicknesses used in the test is shown. This is substantiated by thermal engineering calculations, for which it is provided to obtain new data on the thermophysical characteristics of fire protection materials in the operating temperature range.

Conclusions. The methodology of complex researches is proposed, a considerable volume of unique fire and other experiments with thermotechnical analysis of their results is carried out. A considerable amount of important information necessary to prevent explosive failure and ensure the specified fire resistance of load-bearing reinforced concrete structures was obtained. Recommendations for further experimental and theoretical studies are presented. The use of the obtained results in the design of reinforced concrete structures, means of their fire protection, as well as in the adjustment of normative documents on reinforced concrete structures are presented.

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