<![CDATA[This study examines the feasibility of using crushed porcelinite — a naturally occurring siliceous sedimentary rock found in the Western Desert of Iraq — as a replacement for natural sand in cement mortar, and evaluates whether a Type F superplasticizer can offset the elevated water demand inherent to porous lightweight aggregate. Cement mortar cube specimens measuring 50 × 50 × 50 mm were prepared with crushed porcelinite replacing natural sand at 25%, 50%, 75%, and 100% by volume, alongside a reference mix containing only natural sand. Compressive strength results from the first group identified 25% replacement as the most promising configuration; this mix was subsequently treated with Type F superplasticizer at dosages of 2%, 3%, and 5% by mass of cement and retested at 7 and 28 days. Compressive strength declined consistently as porcelinite content rose, accompanied by a marked increase in the water-to-cement ratio from 0.64 at 25% replacement to 1.30 at full replacement, an increase of 103%. Dry densities of the untreated porcelinite mortars ranged from 1,664 to 1,920 kg/m³, confirming their lightweight character. Superplasticizer addition raised the 28-day compressive strength of the 25% porcelinite mortar by 2.8%, 8.5%, and 19.1% at dosages of 2%, 3%, and 5% respectively, while reducing free water demand by 12.5% at the two lower dosages and 18.75% at 5%. The highest strength recorded, 31.80 N/mm² at 28 days, approaches the lower boundary of the moderate-strength lightweight concrete range. The results indicate that porcelinite is a technically viable and locally available lightweight fine aggregate for cement mortar in Iraq, and that the strength penalty associated with its high porosity can be substantially offset through chemical admixture treatment.]]>
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