Comparative analysis of biogenic and chemical sulfuric acid attack on hardened cement paste using laser ablation-ICP-MS

The aim of this study was to investigate the relative role of chemically and microbially derived sulfuric acid (H₂SO₄) corrosion on hardened cement paste representing a concrete binder. Cement stone disks were exposed to chemical H₂SO₄ (pH 1.0 and 2.0) and biological H₂SO₄ (pH 1.5-2.1). After 28 days, the degree of damage was evaluated by common visual-physical parameters and laser ablation-ICP-MS as a novel evaluation tool to assess changes in elemental distributions. The results revealed a pH-dependent degree of damage. The 4 mm thick disk at pH 1.0 was completely corroded. For the disks exposed to biogenic and chemical H₂SO₄ at pH 2.0 an intact core remained with a similar thickness of the corrosion layer (1.8-2.0 mm) and sulfuric acid penetration depth (1.1-1.3 mm). Since the elemental distribution was similar in the corroded layer independent of applying biological or chemical H₂SO₄, no obvious differences between the two acid attacks were revealed.