Behaviour of reinforced concrete slabs made with high-strength concrete

• Main Author: Hussein, Amgad Ahmed
• Format: Thesis
• Language: English
• Published: Memorial University of Newfoundland 1990
• Subjects: Newfoundland
• Online Access: https://research.library.mun.ca/5322/; https://research.library.mun.ca/5322/1/Hussein_AmgadAhmed.pdf; https://research.library.mun.ca/5322/2/Hussein_AmgadAhmed.pdf

The present research investigation deals with the structural behaviour of two-way slabs made with high-strength concrete subjected to punching shear. -- A high-strength concrete mix, suitable for offshore applications, was developed using conventional cement and aggregates available in Newfoundland. The incorporation of silica fume and high-range water reducing agent made it possible to achieve high strengths at early ages. A compressive strength of 70 MPa at 28 days was achieved for concrete mix incorporating 12% class F fly ash, 8% condensed silica fume and a high-range water reducing agent of naphthalene formaldehyde base. The relevant rheological and mechanical properties of the mix were examined. In addition, an experimental program was carried out to study the effect of cold ocean water, simulated under laboratory conditions, on the mechanical properties of green high-strength concrete containing silica fume and fly ash. -- Seventeen slabs were tested in the structural laboratory at M.U.N. The effect of the reinforcement ratio, concrete strength, slab depth and column size on the behaviour of the slabs was investigated. The structural behaviour of the tested slabs with regard to deformations, strains, ultimate capacity, and modes of failure was examined. Test results revealed that the present North American Codes are unsafe for high-strength concrete slabs, since they overestimate the influence of the concrete strength, as a factor, on the ultimate capacity of two-way slabs. -- Based on the test results, a mechanical model was adopted. The formulation takes into account the actual behaviour of the high-strength concrete and steel. The proposed model gave a fairly good agreement between the predicted and experimental punching loads.