Compressive Strength of Compacted Portland Cement-Based Mixtures Using Phosphogypsum

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Title: Compressive Strength of Compacted Portland Cement-Based Mixtures Using Phosphogypsum

Author(s): Kuo-Ting Lin, Antonio Nanni, and Wen Chang

Publication: Special Publication

Volume: 96

Issue:

Appears on pages(s): 57-76

Keywords: compacting; compressive strength; consolidation; gypsum; phosphoric acids; portland cements; roller-compacted concrete; vibration; wastes; Materials Research

Date: 1/1/1987

Abstract:
Industrial and mining wastes, often extremely fine-grained, are being used as fillers and binders in structural concrete and consolidation by compaction, as opposed to high-frequency vibration. Impact and static compaction can be industrially used for the automatic production of such building elements as bricks and blocks, whereas roller-compacted concrete is more suitable for field applications. Compressive strength characteristics under air-dry, sealed, and soaked conditions of portland cement mixtures containing a complete range of combinations of dihydrate phosphogypsum (by-product of the phosphate fertilizer industry) and fine aggregate (crushed lime rock) are presented. Cylindrical specimens were prepared according to the Modified Proctor procedure (impact compaction). Based on these results, strength comparisons are made for selected constituent proportions in the cases of: 1) consolidation by static compaction; 2) consolidation by high-frequency vibration; 3) site consolidation by vibratory roller compactor; and 4) substitution of the dihydrate phosphogypsum with the hemihydrate form (other available by-product). It is shown that consolidation by compaction is advantageous because of the contribution of phosphogypsum to strength development. Laboratory-compacted samples of the by-product alone indicate that strengths of over 1000 psi (6.89 MPa) can be achieved. In addition, low-cement (7.5 percent) mixtures using hemihydrate gypsum waste exceed the 4000 psi (27.56 MPa) mark.