Abstract

Using durable materials is a sustainable solution for extending the lifetime of constructions. The use of crystalline admixtures makes cementitious materials more durable. They plug pores, capillary tracts and microcracks, blocking the entrance of water due to the formation of crystals that prevent the penetration of liquids. The literature has covered the performance of these admixtures on concrete, but studies on mortars are still scarce. The aim of this study is to investigate the effect of an aggressive environment (sulphuric acid solution—3 wt%) on mortars produced with different percentages of a crystalline admixture (1%, 1.5% and 2% by weight of cement content). Physical and mechanical properties were studied after immersing the mortars in a H2SO4 solution for 90 days. It was found that, after a 90-day sulphuric acid exposure, mortars with the crystalline admixture showed greater compressive strength than the control mortar, besides exhibiting lower mass loss. However, the crystalline admixture did not produce any significant effect on the capillary water absorption coefficient. In a nonaggressive environment, and in the short term, the crystalline admixture did not have a significant effect on the compressive strength, the capillary water absorption coefficient or the ultrasonic pulse velocity.

Highlights

  • Nowadays, cement-based materials are exposed to acids because of environmental pollution, contact with some soils, ground waters, industrial waste-waters or sewers

  • Materials that are designed to work in aggressive chemical conditions must be durable materials, that is, materials with the capacity to withstand, for its service life, the physical and chemical conditions to which they are exposed [4]

  • The results demonstrate that the ultrasonic technique reflects the deterioration caused by sulphuric by sulphuric acid attack, providing information about the internal condition and quality of the acid attack, providing information about the internal condition and quality of the mortars [56,57]

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Summary

Introduction

Cement-based materials are exposed to acids because of environmental pollution, contact with some soils, ground waters, industrial waste-waters or sewers. These conditions can be found in some foundations, sanitation networks, treatment plants, agricultural and farm facilities, etc. The reaction of the sulphuric acid (H2 SO4 ) with the chemical compounds of cement hydration (calcium silicate hydrate, portlandite and calcium sulphoaluminate hydrate) generates gypsum, amorphous hydrous silica and aluminum sulphate.

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