Field performance of plain and blended cement concretes in marine environments

Abstract

Concrete is the most versatile construction material in the world today. It is estimated that approximately 50% of the expenditure in the construction industry is spent on repair and rehabilitation of the existing structures in aggressive environmental conditions. This implies a need to study the reasons for its deterioration and make the necessary changes required. A marine environment is the condition prevailing in and in the vicinity of an ocean or sea. Coastal areas, which can be characterized to have a marine climate, reach normally some 10 km from the coastline, due to wind-blown salt mist. The study of concrete in this environment deserves special attention due to the nature of deterioration. The present research was conducted to evaluate the performance of plain and reinforced concrete specimens exposed to the marine environment at Khaleej Mardomah research centre, Jubail Industrial city, Saudi Arabia, for a period of five years. The exposure conditions included: tidal, belowground, and aboveground zones. The mix variables included: cement content, water to cementitious materials ratio, mixing and curing water and type of curing. The different materials under the study included Type I and Type V cements, blended cements, additives, corrosion inhibitors, curing compounds and coal tar epoxy. The effect of exposure conditions on the performance of the selected mixes was evaluated by assessing the mechanical properties and morphological/mineralogical changes. Deterioration was the highest in the specimens placed in the tidal zone, followed by the ones in belowground and aboveground zones. The data obtained were analyzed to rank the performance of the investigated mixes in tidal, below ground and above ground zones. Based on the results, the following cement concrete mixes are recommended: (a) Tidal zone: 70% ground granulated blast furnace slag or 10% super-pozz. (b) Below ground zone: 8% silica fume with 0.3 w/cm ratio. (c) Above ground zone: 8% silica fume with 0.3 w/cm ratio, or 8% silica fume or 20% fly ash.