Influence of open porosity, hydration products and extent of hydration on the strength of desilicated lime fly ash composites

The prediction of strength of lime ash composites is critical for quality control, material performance monitoring and material serviceability limit state. A study was conducted to investigate the influence of open porosity (an index of micro grain alignment and macro particle parking), sum of hydration products and extent of hydration of desilicated fly ash (DFA) on the unconfined compressive strength (UCS) of DFA lime composites. A comparison with as received fly ash (FA) was also done. The wet and dry cycle durability of DFA and as received FA composites was also investigated. The DFA and FA composites were found to have a UCS of 8.6 MPa and 7.9 MPa respectively. The FA composite was found to be more durable than the DFA composite as after 10 wet and dry cycles the composites had a UCS of 3.5 and 1.8 MPa respectively. Statistical correlation between UCS and open porosity, extent of FA/DFA hydration and sum of hydration products was implemented by Multivariate analysis. For both FA and DFA it was observed that the three parameters combined (open porosity, extent of FA/DFA hydration and sum of hydration products) had the greatest influence on the UCS than individually. This study shows that no single parameter on its own can adequately be used to predict UCS of FA/DFA lime composites. Correlation coefficients above 0.98 were found to describe the relationship between the three parameters and UCS for each composite. Thus could account for differences in durability or soaked strength of materials with equal initial dry strength.