Search

To mitigate autogenous shrinkage that may cause early-age cracking of alkali-activated fly ash-slag (AAFS) concrete, internal curing using superabsorbent polymers (SAP) is employed in this study. AAFS pastes with different SAP dosages (0–0.5%) and slag replacement ratios to fly ash (15–30%) are investigated. Experimental results indicate that with the addition of SAP workability of fresh paste is improved while compressive strength is comparatively reduced. As SAP dosage increases from 0.2% to 0.5%, chemical shrinkage and autogenous shrinkage of AAFS pastes are reduced by around 18% to 45% and 76% to 85%, respectively. Internal curing of SAP is found to lower the heat peak and shift the peak to the right. This indicates the slower hydration rate corresponding to the lower chemo-mechanical deformation (chemical shrinkage), which contributes to the mitigation of autogenous shrinkage. Therefore, internal curing by means of SAP is an efficient method for mitigating autogenous shrinkage in AAFS pastes.

This paper presents a systematic study on the feasibility of using recycled tyre polymer (RTP) fibres for mitigating the damage of concrete induced by elevated temperatures. A series of tests were conducted to investigate the effect of RTP fibres on mechanical and thermal behaviour, pore pressure build-up and microstructural evolution of concrete exposed to elevated temperatures (20, 105, 250, 400 and 600 °C), based on which the mechanism of RTP fibres in mitigating damage of concrete was explored. Results indicate that the addition of RTP fibres effectively prevented pore pressure accumulation and significantly mitigated damage of concrete at high temperatures as the melting of RTP fibres and thermal incompatibility between RTP fibres and concrete promoted the formation of interconnected pore-microcrack network of concrete. RTP fibre was proved as a promising sustainable alternative to manufactured polymer fibres for enhancing high temperature and fire resistance of concrete. The optimal RTP fibre content was 1.2 kg/m3 considering the damage mitigation efficiency and strength loss.

This paper presents a meso-scale modelling framework to investigate the fracture process in concrete subjected to uniaxial and biaxial compression accounting for its mesostructural characteristics. 3D mesostructure of concrete consisting of coarse aggregates, mortar and interfacial transition zone between them was developed using an in-house code based on the Voronoi tessellation and splining method, which enables to generate the realistic-look aggregates with controllable structural features such as content, location, size and shape. Based on the generated 3D mesostructure, the concrete damage plasticity approach was employed to simulate the compressive fracture behaviour of concrete in terms of crack morphology and stress-strain response against the shape parameters of aggregate. Results indicate that the shape of aggregate has a negligible effect on compressive strength of concrete, which is highly associated with the random location and size distribution of aggregate. The aggregate irregularity has a significant influence on crack initiation and growth of concrete.

Inorganic polymer concrete (IPC) reinforced with basalt fibre reinforced polymer (BFRP) was proposed as a promising substitute of conventional reinforced concrete for structures to enhance their sustainability and durability. This paper, for the first time, presents a systematic study, experimental, theoretical and numerical, of shear behaviour of IPC beams reinforced with BFRP bars and stirrups considering the effects of stirrup spacing (S = 80, 100 and 150 mm) and shear span-to-depth ratio (λ = 1.5, 2.0 and 2.5). Result indicates that all BFRP-IPC beams fail in shear as a result of BFRP stirrup rupture and shear-compression failure. Compared to S, λ has a more pronounced influence on shear performance of BFRP reinforced IPC beams, with a maximum reduction of ultimate shear load by 29.4%. The simulation results show good agreement with experimental data, while the theoretical predictions according to existing design provisions for FRP reinforced concrete have a discrepancy of more than 30% with experiments due to lack of consideration of λ. Modified equations taking into account the effect of λ were then derived and used to predict the shear capacity of BFRP reinforced IPC beams, which agrees well with experimental data with an average discrepancy of only around 5%.