Properties of lightweight pedestrian paving blocks incorporating wheat straw: Micro-to macro-scale investigation

This study elucidates the manufacture of lightweight pedestrian paving blocks (LPPB) by partially substituting sand with wheat straw fibres. Sodium silicate was used to treat wheat straw fibres before their integration into the mixtures. The physical, mechanical, and long-term properties of all LPPB mixtures were evaluated by running the slump, compressive and splitting tensile strength, and water absorption tests, respectively. The interfacial transition zone and interaction mechanism between wheat straw and the cementitious matrix were thoroughly investigated through scanning electron microscopy (SEM) and fourier transform infrared spectroscopy (FTIR) analyses, respectively. The results demonstrated the formation of a relatively strong interphase bonding between wheat straw and cement when the wheat straw is treated with sodium silicate. However, evident delamination in mixtures is noticed when untreated wheat straw is employed. A maximum reduction of 62% in the water absorption of LPPB mixtures containing 5% treated wheat straw was achieved, compared to control, due to the influence of sodium silicate in sealing the pores of wheat straw fibres. All LPPB mixtures experienced a drop in their compressive and splitting tensile strength values after the integration of wheat straw (treated and untreated). Still, the drop was less severe in the case of treated wheat straw mixtures attributable to the better bonding that sodium silicate forms.