Studies on Lightweight High-Strength Shotcrete
With small deadweight, light-weight shotcrete can avoid the shotcrete lining from falling off, which benefits the bolt-shotcrete support of the roadway better under same bond strength. Light-weight shotcrete can be made by using clay ceramsite, polystyrene particles and fly-ash ceramsite to replace some gravel and sand. The experiments show that the characteristic of fly-ash ceramsite shotcrete is superior to that of clay shotcrete, while by replacing part of gravel and sand with polystyrene particles and fly-ash ceramsite, light-weight high strength shotcrete will have excellent combination properties.
Slag Micro Powder Affected to the Mine Shotcrete Performance
A study was conducted in the lab on the different added quantity of the slag micro powder affected to the compressive strength,tensile strength,bending strength,and anti chlorine ion permeability of the light shotcrete.The paper analyzed those influence causes and mechanism occurred.The study results showed that the compressive strengths of the light shotcrete with 30% slag micro powder added would be increased individually after 3 days and 7 days and the bending strength of the shotcrete would be reduced with the slag micro powder added quantity increased.The tensile strength of the shotcrete could be increased within 10% slag powder added and would be reduced over 20% slag powder added.With the slag powder added increased,the toughness index of the shotcrete would be reduced and the anti chlorine ion permeability would be steadily increased.The suitable added quantity of the slag powder would be ranging from 10% to 20%.
DETERIORATION OF CONCRETE STRUCTURES IN THE ARABIAN GULF
This is a report of condition surveys of about 100 reinforced concrete structures in the United Arab Emirates. Each survey consisted of a visual inspection, a delamination survey, and a covermeter survey to determine the depth of concrete cover to the reinforcement. Chloride and sulphate contents and the depth of carbonation were determined from dust samples. The sulphate content results and the carbonation results are presented in this paper. It was found that in the Arabian Gulf, where the presence of sulphates is generally accompanied by the presence of chlorides and high temperatures, sulphate attack is not a major problem. The use of sulphate resisting cement is not necessary and may even be detrimental. Carbonation study results are presented and their design implications are discussed.