Title : SULFATE INGRESS ON FLY ASH CONTAINING MORTAR SAMPLES
Authors : Johannes Haufe, Anya Vollpracht and Wolfgang Brameshuber
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Price : 250
Abstract : To characterise the influence of fly ash on the sulfate ingress, experiments were conducted on mortar samples. Different types of cement in combination with and without fly ash were examined using flat prisms. The specimens were stored in sodium sulfate solution with a sulfate content of 30,000 as well as 3,000 mg SO42-/l. The experiments were conducted at different temperatures between 5 °C and 20 °C. The sulfate attack was evaluated by measuring the expansion and the dynamic modulus of elasticity of the specimens. To characterise the ingress of sulfate ions and the development of expansive phases, a grinding equipment was developed to take subsequent powder samples over the depth of the specimen. The received powder was analysed via X-ray diffraction (XRD). To support the achieved results scanning electron microscopy (SEM) was used on polished sections of the specimens. The study shows that the acceleration of the test by increasing the concentration of sulfate ions can also be achieved by lowering the temperature. Furthermore, it is shown that the lower concentration of sulfate in the test solution results in a different attack mechanism. It can be concluded that realistic lower sulfate concentrations should be used in future test procedures to avoid the formation of phases to an extent that will not appear in nature.