Flexural behaviour of ferrocement
Ferrocement is often believed to be a form of reinforced concrete. However, in spite of the similarities between the two materials there are still major differences, indicating that ferrocement requires a separate study to establish its structural performances. On the other hand, although a large amount of research has been carried out on ferrocement, its flexural behaviour is still not fully understood. The aim of this investigation is to study the structural behaviour of ferrocement plates under flexural loading and the influence of the different variables on the strength and deformation characteristics. The variables studied were the mesh number, strength, opening and distribution, presence of steel bars, and the thickness of the section and the mortar cover. The experimental programme included 49 plates, 1000x300 mm in dimensions, reinforced with woven type steel wire mesh and tested under two lines load. Deformation measurements were taken from first application of the load up till failure and about10000 crack measurements (crack width and spacing) were recorded. The crack width data were dealt with statistically. The effect of the variables on the crack width was studied, quantitatively, by comparing the rate of growth of crack width of the plates. It was found that ferrocement cracking behaviour is characterized by almost a full development of the cracks at relatively early stages of the load (about 30-50% of the ultimate load) and the crack width is smaller and more uniformly distributed than in reinforced concrete. The mesh number and yield strength influenced significantly the crack width and spacing. There was a limit for the mesh number after which the enhancement in the cracking performance of the plates slowed down noticeably. Crack width prediction equations were derived from these tests showed good correlation, whereas the published crack width formulae largely overestimated or underestimated the measured crack width. The strength and deformation were influenced mainly by the yield strength and fraction volume of reinforcement in the loading direction. The deflection is most likely to exceed the serviceability criteria before the crack width. For a span-deflection ratio of 180, the mean crack width was mostly below 20 microns, and the load was about 15-30% of the ultimate load. A procedure is proposed to analyse ferrocement sections under flexural loading. While application of reinforced concrete theory to predict the ultimate moment largely underestimated the experimental results, the proposed procedure predicted closely the experimental moment and deflection at first cracking, yielding and failure of the tested plates.