Influencia de diferentes condiciones de curado en la estructura porosa y en las propiedades a edades tempranas de morteros que contienen ceniza volante y escoria de alto horno

Abstract

In this work, the evolution of the microstructure, durability properties and mechanical strength of mortars made with commercial cements, which contain fly ash (between 21% and 35%) and ground granulated blast-furnace slag (between 66% and 80%), were studied. These mortars were exposed to three different environments during their hardening, an optimum laboratory condition, and two environments representing a mild Atlantic climate and a Mediterranean climate, respectively. As a reference, ordinary Portland cement mortars were also tested. The microstructure was characterized using mercury intrusion porosimetry. Regarding durability, the capillary suction coefficient and non-steady-state chloride migration coefficient were determined. Compressive strength was studied too. The tests were performed at 7, 28 and 90 days. The main conclusion of this work is that cements with slag and fly ash hardened under environmental conditions of Atlantic and Mediterranean climates, can develop good service properties after three months of hardening.

Durability and compressive strength of blast furnace slag-based cement grout for special geotechnical applications

“…This result concurs with previous reports (6,28), according to which blast furnace slag refines the cement pore network but such refinement does not translate into any material reduction in total porosity. The findings also indicate that the w:c ratio scantly affects grout microstructure other than as regards the foreseeable rise in pore volume at higher ratios.…”

“…While at early ages electrical resistivity was similar in the two cement grouts, at later ages higher values were recorded for CEM III than for CEM I. These findings may be related to the substantial microstructural refinement attendant upon slag hydration (6,7,28), in which additional C-S-H phases form (12), giving rise to a more compact pore network. Moreover, the fact that early age electrical resistivity values were similar in the two types of cement studied, but slightly higher for CEM I at w:c ratios of 0.5 and 0.55 may be attributable to the slower reaction rate in slag hydration (7,34).…”

“…Electrical resistivity rose with time for both types of cement studied (see Figure 2), denoting the progressive refinement of the pore network as a result of ongoing clinker and slag hydration (6,28). While at early ages electrical resistivity was similar in the two cement grouts, at later ages higher values were recorded for CEM III than for CEM I.…”

“…This finding was foreseeable, given the higher strength class of CEM I (52.5 MPa) than CEM III (42.5 MPa). Moreover, strength gain in slag-blended cement is known to be slower than in portland cement (7,28), requiring more time to reach comparable strength values. In addition, the CEM III studied here has low initial strength.…”

“…Given the large number of samples analysed in this study and the need to determine all the porosity-related properties at approximately the same time, the samples were dried at 105 °C for 12 hours and from then on through the beginning of the test 12 hours later, they were stored in air-tight containers with silica gel. This procedure has been used in the past for fly ash-and blast furnace slag-blended cement (28).…”