Influence Of Volcanic Scoria On Mechanical Strength, Chemical Resistance And Drying Shrinkage Of Mortars

Abstract

In the study, three types of cement have been prepared; one CEM I type (the control sample) and two blended cements: CEM II/A-P and CEM II/B-P (EN 197-1), each of them with three replacement levels of volcanic scoria: (10 %, 15 %, 20 % wt.) and (25 %, 30 %, 35 % wt.), respectively. Strength development of mortars has been investigated at 2, 7, 28 and 90 days curing. Evaluation of chemical resistance of mortars containing scoria-based cements has been investigated through exposure to 5 % sulphate and 5 % sulphuric acid solutions in accordance with ASTM C1012 & ASTM 267, respectively. Drying shrinkage has been evaluated in accordance with ASTM C596. Test results showed that at early ages, the mortars containing CEM II/B-P binders had strengths much lower than that of the control mortar. However, at 90 days curing, the strengths were comparable to the control mortar. In addition, the increase of scoria significantly improved the sulphate resistance of mortars. Further, an increase in scoria addition improved the sulphuric acid resistance of mortar, especially at the early days of exposure. The results of drying shrinkage revealed that the CEM II/B-P mortar bars exhibited a greater contraction when compared to the control mortar, especially at early ages. However, drying shrinkage of mortars was not influenced much at longer times.

Volcanic Scoria as Cement Replacement

“…The increase of drying shrinkage with the cement replacement level [99] might be due to: (1) the pozzolanic reaction, generating an additional CSH, resulting in the decrease in spacing of CSH particles; (2) the transportation of large pores into fine pores (pore size refinement) increasing capillary tension [99][100][101][102][103]; (3) the higher water demand of scoria-based cements [99,102]; (4) the porous microstructure of scoria [104] (Figure 1d). However, this increase was lower than the maximum 0.03% allowed by ASTM C618 (Figure 11) [99]. Figure 11 shows the results of drying shrinkage of VS-based cement mortars.…”

“…In addition, none of the mixtures containing 25% volcanic scoria and more lost 10% weight even after 100 days of exposure to nitric and acetic acids. Weight losses over time of 90 days-cured mortars exposed to 5% H 2 SO 4 [99].…”