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A comparative study has been performed on the acid resistance of cement paste exposed to acetic acid (pH=4) and sulfuric acid (pH=2). The pastes are prepared by replacing 30% and 50% cement with limestone powder. Their properties and microstructures are investigated by using strength test, X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. The paper reveals that erosion extent of pastes depends mainly not only on the pH value of acid solution and the w/b ratio of pastes, but also on the limestone powder mixed that contributes partly to the hydration. Though gypsum and ettringite formations are dominant to the deterioration of pastes exposed to sulfuric acid solution, the degree of decrease for the compressive strength of specimens exposed to sulfuric acid is retarded compared with the specimens exposed to acetic acid. This is attributed to the product of gypsum, which delays the further erosion to the internal paste.