Abstract
Acid attack causes the deterioration of construction material surfaces. The objective of this study was to investigate the degradation of different types of cement mortar in terms of variations in pore size distribution obtained by mercury intrusion porosimetry (MIP), mass loss, and compressive strength. The mortars were manufactured with nanosilica, zinc stearate, and an ethyl silicate coating. After curing (28 days), the samples were subjected to acid exposure for 90 days, immersed ina solution (3% w/w) of sulphuric acid (H2SO4). The results indicate that the mortars showed a more refined microstructure, with a higher proportion of smaller pores (<100 nm) compared to the control mortar. The 28-day and 90-day compressive strength variations of mortars were also determined by observing pronounced reduction due to the appearance of expansive compounds responsible for microcracking.
Highlights
Acid rain can be produced by natural effects, but it is human action that causes the most emissions of sulphur and nitrogen oxides
This study evaluates the effects of acid rain, simulated with a solution of sulphuric acid, on mortars made with three types of admixtures
This paper addresses the degradation of different types of cement mortars exposed to sulphuric acid attack using mercury intrusion porosimetry
Summary
Acid rain can be produced by natural effects (e.g., volcanic eruptions), but it is human action that causes the most emissions of sulphur and nitrogen oxides (e.g., metallurgical industry, energy production processes, and heating system). Several studies show that acid rain generates a layer of gypsum on the substrate [2,3] due to a chemical reaction of sulphuric acid with products of cement hydration (such as calcium silicate hydrate and calcium hydroxide) [4,5], and with calcium carbonate [6] that usually comes from aggregates utilised in the manufacturing of cementitious materials. Ethyl silicate ( called TEOS-tetraethyl orthosilicate) is a versatile product that has been used since the early 20th century for various applications (e.g., stone consolidant, ceramic binder, adhesive, source of amorphous silica) [16] It is one of the most used products in the consolidation of architectural heritage materials, such as bricks, stone, and lime mortars. This study evaluates the effects of acid rain, simulated with a solution of sulphuric acid, on mortars made with three types of admixtures (zinc stearate, nanosilica, and an ethyl silicate coating). The effects of the acid attack were analysed in terms of microstructure, compressive strength, and mass loss
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