Location
University of Leeds
Keywords
acid attack, aggregate, durability, degradation kinetics, cement mortar, micro-tomography
Abstract
Cement-based materials being alkaline in nature are often subjected to rapid deterioration on exposure to the aggressive acidic environments. Acids penetrate into the cement matrix causing calcium leaching and deterioration of phases leading to alteration in the microstructure. Currently, there are hardly any codes or standards available for evaluating the durability of materials to acid attack. Moreover, the literature addressing the material resistance is quite inconclusive. This paper aims to evaluate the influence of mineralogical nature of aggregates on the degradation kinetics of cement mortar when exposed to inorganic and organic acid solutions by performing a static accelerated leaching test. Cement mortar (1: 3) specimens of size 10 × 10 × 60 mm were prepared using Ordinary Portland Cement (OPC), using limestone (calcareous) aggregates and siliceous aggregates with a water to cement ratio of 0.40. After 28 days of initial curing in saturated lime water, the specimens were exposed to various concentrations of sulphuric (1 % and 3 %) and acetic acid solutions (0.25 M and 0.5 M) for a testing period of 4 months. The acid solution was replenished on a periodic basis to maintain the aggressiveness of the solution. The degradation kinetics was investigated by measuring mass changes, thickness changes, changes in pH of the acid solution and imaging using X-ray micro-tomography. Additionally, periodic abrasive action applied manually (using soft nylon brush) was used to accelerate the degradation process in case of sulphuric acid exposure and its effect was compared with the testing without the abrasive action. An attempt was also made to evaluate the changes in compressive strength and changes in dynamic modulus of elasticity of cylindrical mortar specimens (25 mm diameter and 50 mm height) on exposure to the acid solutions. The test results indicate that the performance of limestone aggregates is better on exposure to sulphuric acid and worse in case of acetic acid when compared to siliceous aggregates.
Included in
Influence of Mineralogical Nature of Aggregates on Acid Resistance of Mortar
University of Leeds
Cement-based materials being alkaline in nature are often subjected to rapid deterioration on exposure to the aggressive acidic environments. Acids penetrate into the cement matrix causing calcium leaching and deterioration of phases leading to alteration in the microstructure. Currently, there are hardly any codes or standards available for evaluating the durability of materials to acid attack. Moreover, the literature addressing the material resistance is quite inconclusive. This paper aims to evaluate the influence of mineralogical nature of aggregates on the degradation kinetics of cement mortar when exposed to inorganic and organic acid solutions by performing a static accelerated leaching test. Cement mortar (1: 3) specimens of size 10 × 10 × 60 mm were prepared using Ordinary Portland Cement (OPC), using limestone (calcareous) aggregates and siliceous aggregates with a water to cement ratio of 0.40. After 28 days of initial curing in saturated lime water, the specimens were exposed to various concentrations of sulphuric (1 % and 3 %) and acetic acid solutions (0.25 M and 0.5 M) for a testing period of 4 months. The acid solution was replenished on a periodic basis to maintain the aggressiveness of the solution. The degradation kinetics was investigated by measuring mass changes, thickness changes, changes in pH of the acid solution and imaging using X-ray micro-tomography. Additionally, periodic abrasive action applied manually (using soft nylon brush) was used to accelerate the degradation process in case of sulphuric acid exposure and its effect was compared with the testing without the abrasive action. An attempt was also made to evaluate the changes in compressive strength and changes in dynamic modulus of elasticity of cylindrical mortar specimens (25 mm diameter and 50 mm height) on exposure to the acid solutions. The test results indicate that the performance of limestone aggregates is better on exposure to sulphuric acid and worse in case of acetic acid when compared to siliceous aggregates.
