Influence of Fineness of Recycled Glass Waste and Slag on Compressive Strength of Sulphate Resisting Cement Mortars

Background:

Cement and concrete industry is responsible for 5% of the worldwide man-made CO₂ emission to environment. Therefore, the demands of producing low carbon concrete is increasing every day for climate change mitigation and adaptations.

Objective:

To minimize the amount of clinker production and associated CO₂ emission, the potential use of recycled ground glass waste (GGW) and electric arc furnace slag (EAFS) as a substitute of cement was evaluated through compressive strength tests on mortars and by calculating their strength activity index (SAI) values.

Method:

At first, two optimized fineness levels were attained for both cement substituting materials used in this study (GGW as glass fine ˂ 38µm (GF), glass superfine ˂ 25µm (GSF) and EAFS as slag fine ˂ 75µm (SF), slag superfine ˂ 32µm (SSF)). In addition to control mortar (CM), four types of binary mortar mixtures were cast by substituting cement 5-20% with GGW (GF and GSF) and 10-30% with EAFS (SF and SSF). ASTM C109 and C311 were employed to perform compressive strength tests and to calculate the SAI values, respectively.

Results:

The results demonstrated that the strength of mortar increased with increasing fineness of both the cement substitute materials. More specifically, the compressive strength of mortar containing GSF matched with those of CM at 5% substitution and comparable for its other substitutions (10, 15, and 20%) at age of one-year. Similar results were noticed for SSF at its 10% substitution where it produced the best comparable results to CM. However, the strength of mortars containing SF or 30% SSF was significantly reduced as compared to CM.

Conclusion:

Almost all the mortars containing GGW or EAFS have satisfied the strength activity criteria of ASTM C989 Grade 80 of blast furnace slag, except those containing 20 and 30% of SF. Moreover, the mortars containing GSF and SSF matched BFS of Grade 100 corresponding to their 5 and 10% substitutions, respectively.

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