Polyolefin reinforced cement in tension and flexure.

The work reported in this thesis is principally concerned with the experimental and theoretical behaviour of polypropylene- and high modulus polyethylene-reinforced cements in tension and in flexure. Polypropylene-reinforced cement has a proposed application as a thin sheet cladding material and developments in associated thin sheet fibre-reinforced cement technologies are discussed. Existing theories to account for the tensile and flexural behaviour of fibre-reinforced cements are reviewed. A comprehensive theoretical treatment is presented for the complete behaviour in loading-unloading-reloading in direct tension of a cement composite, reinforced by continuous, aligned fibres. The treatment is modified to account for the measured non-linear stress-strain behaviour exhibited by polyolefin fibres. A satisfactory comparison is drawn between theoretical and experimental results for residual strains, reloading moduli and energy absorption during an unloading/reloading cycle. It la argued that an existing approach for the prediction of the flexural load-deflection relationship of a fibre cement composite is inappropriate and an alternative 'crack development' approach is presented, which yields a more realistic comparison with experimental data from flexural tests on polyolefin-reinforced cement composites. The behaviour of specimens under cyclic flexural loading and in reversed flexure through zero is discussed. The theoretical developments are expected to be generally applicable to a range of fibre-reinforced brittle matrix composites