Raman microscopy of alkali-silica reaction (ASR) products formed in concrete

Recently, the structure of the crystalline alkali-silica reaction (ASR) product formed in affected concrete has been identified based on mu-XRD measurements. However, the data were obtained from a single aggregate. In this study, Raman microscopy is applied on crystalline ASR products formed in several aggregates and concrete mixtures, enabling a comparison of their spectra and with it their structure. In a first step, samples from the same concrete used for mu-XRD measurements are analyzed and compared. In a second step, samples from a second structure and from a concrete prism test are measured. In addition to Raman microscopy, SEM with EDX is used to characterize the microstructure. The Raman spectra of the crystalline ASR product are practically identical in all studied aggregates and concrete mixtures, showing it is the same phase. This conclusion is further supported by the microstructural data.