Compressive Strength Gain of Glass Powder–Portlandite: An Investigation Toward Maximizing the Use of Waste Glass as Cement Replacement in Concrete

The paper presents selected findings from a combined theoretical and experimental investigation focusing on chemical reactions and strength gain in glass powder (GP) and calcium hydroxide (CH) mixes as a means of achieving more than the current wisdom of ~20% cement replacement with waste glass powder in concrete. The expected chemical reactions between CH (in concrete, CH is available as a by-product of cement hydration) and silica (SiO₂) present in GP were first theoretically established using mole concept theory. The theoretically obtained results were then used to determine an appropriate CH and GP mix ratio for the CH–GP test specimens. The strength gain in CH–GP specimens with time was determined using compression tests, and the formation of strength contributing compound calcium–silicate–hydrate (C–S–H) was determined using X-ray diffraction (XRD) experiments. The compression test results showed CH–GP specimens possessed noticeable compressive strength, and the XRD results confirmed the formation of C–S–H. The results of both compression test and XRD analysis show the major strength imparting compounds in CH–GP specimens formed at later stages (i.e., after 28 days) of curing.