Effect of polyvinil alcohol fiber on the microstructure and properties of cement composite with expanded glass aggregates

Abstract

The paper presents the results of the tests conducted with light-weight cement-based composite consisting of Portland cement (CEM I 42,5R), expanded glass aggregate (PSU), waste materials with pozzolanic characteristics (metakaolin generated in glass cullet granulation process (MW) and fluidized bed catalytic cracking catalyst (FCCC), and PVA fibres. Two different types of PVA fibres were used in the specimens tested: fibres of diameter 40±1 µm and length 8±1 mm; fibres of diameter 200±1 µm and length 12±1 mm. Two types of cementbased composite specimens were moulded for the tests containing 0.25 % and 0.5 % of the same type of PVA fibre by weight of cement. The following parameters of the composite were tested: hydration process (differential scanning calorimetry), microstructure and chemical composition (SEM, X-ray microanalysis and ultrasonic pulse velocity); mechanical and drying shrinkage characteristics were measured. The test results showed that PVA fibre reduces the heat release rate in the acceleration phase of the hydration process. SEM test results revealed the formation of dense C-S-H micro-zones around the fibres and a good contact between the fibre and the binder. The development of such a structure increases the compressive strength of the composite modified with PVA fibre compared to unmodified control specimens. However, the tests also revealed that PVA fibre do not have significant influence on flexural strength of the specimens. The drying shrinkage tests showed that after 28 days of curing the shrinkage of PSU modified light-weight composite is about twice lower than the shrinkage of control specimens (without PVA fibre) irrespective of the size and the amount of PVA fibre in the composite.