Modelling of Fresh Ultra-High- Performance Slag Concrete Properties Using Response Surface Method

Sana Taha Abdulhussain, PhD student at College of Civil Engineering, University of Technology, 10066, Baghdad, Iraq AND Civil Engineering Dept., College of Engineering, Mustansiriyah University, 10052 Baghdad, IraqFollow
Maan S. Hassan, College of Civil Engineering, University of Technology, 10066, Baghdad, IraqFollow
Shatha S. Hasan, College of Civil Engineering, University of Technology, 10066, Baghdad, IraqFollow

Keywords

UHPC, GGBFS, Steel slag, Setting time, Flow, Response surface method

Document Type

Article

Abstract

The use of large quantities of cement, silica sand, and quartz powder in the production of ultra-high-performance concrete (UHPC) imposes environmental burdens, increases CO₂ emissions, and depletes natural resources. In this concept, there is a need for sustainable UHPC mixtures that reduce clinker and natural aggregate consumption while maintaining ultra-high strength, particularly by utilizing industrial by-products and alternative materials combinations. This study aims to develop sustainable UHPC by incorporating steel slag and utilising accelerated carbonation in the manufacturing of sustainable silica-based binder materials, and to model the resulting fresh properties using response surface methodology (RSM). The investigated variables include GGBFS replacement with cement up to 75%, inert steel slag replacement of fine aggregate up to 95%, and CO₂ curing with various carbonation levels. Their effects on fresh properties (i.e., flow and setting time) and hardened (i.e., compressive strength at 28 days) properties were evaluated using 18 mixtures designed through a design of experiments (DoE) approach to analyse the complementary effects of the influencing factors. Second-order polynomial RSM models were developed, yielding statistically significant and accurate correlations between the input variables and the target responses. The response surface analyses revealed that progressive GGBFS replacement up to 60% yielded a maximum flow of 220 mm and an increased compressive strength of 178 MPa, demonstrating that substantial cement reduction is suitable without compromising UHPC performance. The results also indicated that the prolonged setting time of UHPC mixtures can be effectively controlled by employing accelerated carbonation, particularly in mixtures incorporating slag-based binders. The novelty of this work lies in the unique combination of high-volume GGBFS, treated steel slag, and CO₂ curing, together with RSM-based modelling of fresh and hardened properties. This approach offers a rational framework for designing UHPC mixtures for modelling fresh behaviour and ultra-high strength.

Recommended Citation

Abdulhussain, Sana Taha; Hassan, Maan S.; and Hasan, Shatha S. (2026) "Modelling of Fresh Ultra-High- Performance Slag Concrete Properties Using Response Surface Method," Engineering and Technology Journal: Vol. 44: Iss. 5, Article 4.
DOI: https://doi.org/10.30684/2412-0758.1549

DOI

10.30684/2412-0758.1549

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