OPTIMIZATION OF SCC MIXTURES INCORPORATING A POLYCARBOXYLATE-BASED SUPERPLASTICIZER AND FINE MATERIALS AVAILABLE IN SAUDI ARABIA Fares, G.* Al-Negheimish, A. Alhozaimy, A. Khan, M. I. Al-Zaid, R. Center of Excellence for Concrete Research and Testing College of Engineering, King Saud University Riyadh, KSA Abstract The development of self-compacting concrete in Saudi Arabia under the hot and harsh conditions widespread in the Kingdom represents a real challenge. Moreover, the requirement of utilization of local fine materials in self- compacting concrete is essential for mass production and cost reduction. The adequate additions of local fine materials as fillers in self-compacting concrete should render efficient plastic viscosity and ensure sufficient stability of all phases. However, an increased amount of fine materials requires the use of high range superplasticizer to get the desired flowability. The optimization of the rheology of self-compacting concrete necessitates the optimization of its paste phase, i.e. cement, water, fine materials and superplasticizer. A few of polycarboxylate-based super plasticizers intended for the production of self-compacting concrete are available in Saudi Arabia construction market, such as Glenium. The robustness of this type of superplasticizer with cement and fine material is critical. A little variation in the dosage of Glenium could lead to detrimental bleeding, segregation and formation of a thick powder layer at the concrete top surface. Formulation of robust mixtures of cement with Glenium and limestone dust is the aim of the current paper. A modified mini-slump test supported with photographic-based evaluation method is used. In this method an evaluation index called visual deposit surface index is taken as a qualitative and semi-quantitative index for the superplasticizer concentration range that should be tested. Binary combinations of cement with Glenium and limestone dust are evaluated in paste then being applied in self compacting concrete. Different rheological properties such as T 500 , Slump flow, J-ring flow and visual stability index of SCC mixtures with limestone dust are determined at different times until a standard flow of 650 mm is attained. As an outcome of this research, a good agreement between the effective range of superplasticizer dosages obtained from the visual deposit surface index and rheological properties of concrete is attained. Originality of the research The current research presents a simple test method to optimize the incorporation of a polycarboxylate high range water-reducer admixture in self-compacting concrete using a photographic-based evaluation method. This method determines an effective and robust range of admixture dosages that can be added to SCC without creating significant segregation and without forming a remarkable layer of floated fine particles at the top surface. Contribution of the research The current research contributes to the increase in demand for using the local fine materials and admixtures in self-compacting concrete with minimum concomitant compatibility and robustness inconveniences. Moreover, it helps in the production of low cost self-compacting concrete in Saudi Arabia under the hottest, most dry and harshest climate in the world. Keywords: Optimization, Mini-slump test, Rheology, SCC * Corresponding author: Email galfares@ksu.edu.sa Tel +9661477986, Fax +9661470740