The influence of carbonization on the performances of fly ash geopolymeric concrete

摘要

Two mixtures were designed to manufacture ordinary Portland cement concrete (PCC) and alkali-activated fly ash geopolymeric concrete (FGC). The depth of carbonation at 3rd, 7th, 14th and 28th day were measured according to the carbonization test method in "Ordinary Concrete Long-term Performance and Durability Test Method Standard"(GB/T 50082-2009) by spotting with phenolphthalein solution. The changes of compressive strength of the specimens carbonized with different days were tested and compared, as well as the pH value of specimens' surfaces. Furthermore, the changes in microstructure and chemical composition were observed through the scanning electronic microscope (SEM) and energy dispersive X-ray spectrometer (EDX), respectively. The results show that although the compressive strength of FGC decreased significantly at first, but there is no obvious effect of carbonization on compressive strength, pH value and chemical composition of FGC as carbonation going on. Moreover, the microstructure of FGC is more homogeneous and denser. It can be concluded that compared with PCC, carbonization resistance of FGC is much better.