Resistance of concrete with blast-furnace slag against chlorides, investigated by comparing chloride profiles after migration and diffusion

Abstract

The effect of partial replacement of ordinary Portland cement (OPC) by blast-furnace slag (BFS) on concrete's resistance to chlorides was examined by comparing chloride profiles and colour change boundaries after non-steady state migration and natural diffusion tests, cfr. NT Build 492 and NT Build 443, respectively. Chloride profiles were obtained by means of potentiometric titration and the colour change boundaries by spraying 0.1 M AgNO3-solution. One OPC mixture and three BFS mixtures, with cement replacement levels of 50, 70 and 85 %, were tested. It was found that, compared to OPC concrete, migration coefficients of 50 and 70 % BFS concrete are decreased with 32 and 57 %, respectively. Diffusion coefficients are reduced by 66 and 50 %, respectively. Nevertheless, the chloride binding capacity of BFS concrete, determined from the difference between total and free chlorides, was lower than for OPC concrete. The results for 85 % BFS concrete differ from the results for 50 and 70 % BFS concrete, since higher migration and diffusion coefficients are found. Besides, free chloride concentrations at the colour change boundary (ccb), obtained after spraying with AgNO3-solution, amounted to 0.30 mol/l on average. There was no clear relation between the free chloride content at ccb and the BFS content

Evaluating the effects titanium dioxide on resistance of cement mortar against combined chloride and sulfate attack

“…To resemble sulfate in the marine environment, Na 2 SO 4 with a concentration of 27.5 g/L was added to chloride solution. To see the impact of sulfate, a concentration of 55 g/L of Na 2 SO 4 was used as well . Na 2 SO 4 and NaCl were used as control samples, separately.…”

“…Using the 0.1 M AgNO 3 spray onto both surfaces, the chloride penetration depth was measured. The white deposit of AgCl 2 showed the penetration depth, which was measured by caliper . To get the penetration profile, chloride concentrations needed to be measured at different depths.…”

“…Cement replacement might have a positive effect on the resistance of concrete against chloride penetration. Several supplementary cement materials have been used to control hydration heat and improve the service life of marine structures …”

“…Several supplementary cement materials have been used to control hydration heat and improve the service life of marine structures. [11][12][13][14][15] Another threat in marine environments is the penetration of sulfate ions through diffusion and capillary suction. Some common forms of sulfate ions found in seawater, such as Na 2 SO 4 and MgSO 4 , result in the expansion of the concrete samples and reduction of compressive strength.…”

Mechanical, durability and hygrothermal properties of concrete produced using Portland cement-ceramic powder blends

“…In addition, pozzolans were found to increase the strength and chemical resistance and reduce heat of hydration, permeability, porosity and alkali-silica expansion, which was another bonus [9]. The most frequently used pozzolans in the current concrete industry are industrial by-products such as fly ashes [10], silica fume [11], metallurgical slags [12] or waste glass [13]. Agricultural wastes, represented, for instance, by rice husk ash [14], bagasse ash [15] or sugar cane leaf [16], are being increasingly used, particularly in the regions where they are produced.…”