The Effect of Water-to-Cement Ratio and Curing on Material Properties of Mortar Specimens in Stray Current Conditions

Abstract

This work reports on the synergetic effect of water-to-cement ratio, curing conditions, varying external environment and stray current on the microstructural (porosity and pore size), electrical (resistivity) and mechanical (compressive strength) properties of 28 days-cured cement-based materials. The influence of curing on porosity and pore size, in stray current conditions, was assessed by correlating the performance of 28 days cured mortar with that of fresh (24h-cured only) mortar specimens in identical environmental medium. Three different levels of electrical current density (i.e. 10mA/m 2 , 100 mA/m 2 and 1 A/m 2 ) were applied to simulate stray current flow through hardened mortar specimens with water-to-cement ratio of 0.5 and 0.35. Different environmental conditions were employed i.e. sealed conditions, partly immersed, and fully submerged in water and calcium hydroxide medium. Microstructural, mechanical and electrical properties were monitored in the course of 140 days. The outcomes suggest a potentially positive effect of the stray current, where water and/or humidity exchange with the external environment is restricted. The potential for this positive effect was experimentally supported through the recorded matrix densification and increased compressive strength of mortar specimens, subjected to stray current and treated in calcium hydroxide and/or sealed conditions, compared to equally handled and treated control cases. In contrast, for water submerged mortar specimens, subjected to stray current, coarsening of the bulk matrix and reduced compressive strength were observed. The outcomes were irrespective of w/c ratio and curing conditions. The effect of stray current was found to be predominantly determined by the current density level and increased at values > 100mA/m 2 . This would result in compromised mechanical properties and potentially reduced performance of cementbased materials within service life. Therefore, concrete curing and conditioning on site need to include considerations for the potential effect of stray currents.

Effects of Moisture on Mechanical and Piezoresistive Properties of Cement Composites containing Carbon Fiber during long age

“…Obviously, the mechanical properties of CFRCM1 and CFRCM2 increased obviously with the time going. Similar law of strength development can be found in document [18]. The hydration of cement is a long process.…”

Comparative Analysis on the Mechanical Properties, Transportation Cost, and Carbon Footprint Emission of Cement Mortar with PE and SSRS as Partial Replacement for Aggregates

“…The compressive strength of the various cement mortar specimens improved with a curing time of 3 to 91 days regardless of the aggregate replacement material (SSRS or PE) and w/c ratio. This is due to the continuing hydration of the cement [42]. Additionally, every sample showed a compressive strength of at least 17 MPa, indicating that their strength is on par with that of lightweight structural concrete according to ASTM C330 [43].…”

Bond of steel-mortar interface interfered by stray current

“…stray current flowing through the fresh (non-mature) bulk matrix, may lead to enhanced migration of water and ions. In this case the cement hydration and steel surface passivation can be enhanced [7,46,47]. However, this phenomenon is not evident for the condition of sufficiently cured bulk matrix, as the bulk matrix is already hardened when the stray current is supplied.…”