Case Studies in Construction Materials (Jul 2023)
Development of a Lytag-silica fume based lightweight concrete and corresponding design equation for pure bending
Abstract
This study presents a novel Lytag-silica fume concrete (LSFC) for structural and other construction applications. The evaluation of compressive strength development and stress strain relationships of the LSFC light weight was carried out to determine the strength growth in LSFC and for the development of the proposed beam design equation. Four different mix compositions were adopted for concrete grade 20, 30, 40, 50 at cement dosage of 260, 330, 450 and 570 kg/m3 on 24 concrete samples. A rectangular parabolic stress block was derived using representative stress-strain curves, and the results show that the parameter kbal that defines the ultimate design moment in the compressive zone was equal to 0.107 compared to kbal value of 0.167 for a normal weight concrete according to Eurocode 2. The ultimate compressive strain obtained for LSFC was 2.18‰ after 28 days for the LSFC compared to that of the normal weight concrete (NWC) of 3.5‰. The result also shows that 94.15 % of the compressive strength of LSFC was developed within 7 days of age due to the high pozzolanic chemical composition of Lytag and Silica fume. A reduction in embodied carbon was evident on reduction in water to cement ratio. The analysis and design results compared with NWC shows that Lytag-silica fume light weight concrete reduces reinforcement to 47 % with an increase in shear resistance. Scanning Electron microscopy analysis shows that the pathology and microstructure of the lytag-silica fume concrete is characterised with high micro pores with increasing water to cement ratio while the low water to cement ratio exhibit low distribution of pores which is an attribute of good mechanical properties of LSFC. The stress strain behaviour does not display a strain softening phenomena which is indicative of good flexural strength.
