Date of Graduation

12-2020

Document Type

Thesis

Degree Name

Master of Science in Civil Engineering (MSCE)

Degree Level

Graduate

Department

Civil Engineering

Advisor/Mentor

Murray, Cameron D.

Committee Member

Heymsfield, Ernest

Second Committee Member

Selvam, R. Panneer

Keywords

Alternative cement; Belitic calcium sulfoaluminate cement; Concrete mix design; Fast setting time; High compressive strength concrete; Set retarders

Abstract

Belitic calcium sulfoaluminate (BCSA) cement has well established advantages related to fast setting time, fast strength gain, long-term strengths, shrinkage, and sustainability. Due to its fast setting and hardening, this type of cement has historically been used to repair concrete structures, highways, and runways. This work provides much needed guidance on establishing mix design criteria for BCSA cement. Guidance is also given on the effects of set retarders on strength, slump, and setting times. Citric acid and a phosphonic acid-based admixture were tested as retarders for different concrete mixtures. Three studies were performed. In the slump study five different water contents (ranging from 275lb to 375lb per 1yd3) along with three citric acid dosages were tested (0%, 0.35% and 0.70% of cement weight). These same citric acid dosages were used in the other two studies to have consistency in the results. This study showed that the use of a retarder increases the slump, especially at low water contents. The compressive strength study was carried out testing three water/cement (w/c) ratios and four citric acid dosages (a citric acid dosage of 2% by cement weight was included). The behavior for the same citric acid dosage indicates that a lower w/c is associated with a greater compressive strength. An isothermal calorimeter was used to compare the heat released when citric acid or phosphonic acid admixture were used as retarders. Three citric acid dosages were compared to several phosphonic acid-based admixture dosages to find an equivalent dose between both retarders. The equivalence between those dosages was verified through setting time tests performed with a penetrometer.

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