Various industrial wastes were employed as supplemental cementitious materials to savernthe environment from filling with non-biodegradable wastes and to limit thernconsumption of existing limestone. Waste paper sludge makes up a significantrncomponent of the numerous materials produced as byproducts in the paper industry. Thernoverall goal of this research is to determine the suitability of waste paper sludge ash as arnpartial cement replacement material by conducting compressive strength and reactivityrntests while substituting cement in various quantities. rnThe end-by-product of the paper manufacturing industry is paper sludge, which is a wetrngray waste mud. This paper sludge is turned into ash and utilized as a partial cementrnreplacement. This research is entirely based on the use of waste paper sludge ashrn(WPSA) as a cement replacement in mortar production. WPSA amounts of 0, 5, 10, 15,rn20, 25, and 30% by volume of cement are used to make the mortar mix. rnAt the ages of 7, 28, and 56 days after curing under ambient conditions, the compressivernstrength of mortar cube specimens was measured. The results suggest that increasing thernreplacement level up to a certain level increases the strength of mortar cubesrnincorporating waste paper sludge ash (WPSA). In terms of compressive strength, 15rnpercent replacement yielded the optimum results. rnWPSA reactivity was assessed using a variety of techniques. This was accomplished byrnassessing the reactivity of WPSA using a modified Chappelle test, estimating the amountrnof bound water, and characterization of pastes using XRD analysis was done for arnsample at the optimum replacement level, i.e. 15%. The strength development was alsorncompared to the test results. rnOn day 7, reference sample had a bound water content of 4.18%, whereas blendedrnsample had a bound water level of 5.20%. WPSA has a reactivity of -1244.89 mgrnCa(OH)rn2rn per gram of WPSA. These findings suggest that the increase in compressivernstrength is entirely due to the filler effect.