Abstract
The ambient temperature records in Iraq show a large variation between day and night reaching 20 C, depending on the season, whether it is summer or winter. For this reason, the aim of this research is to study the effect of these conditions on the drying shrinkage of self-compacting concrete produced by using Portland-Limestone cement (ASTM C595 - Type IL). SCC mixes were designed to attain compressive strengths of 40 and 60MPa at 28days with and without silica fume respectively. Same mixes were reproduced with ordinary Portland cement (ASTM C150 - Type I) for comparisons. Two maximum sizes of aggregate 10 and 20 mm were incorporated in this work. The drying shrinkage was measured for 180 days after 7 days of water curing. The range of ambient (outdoor) temperature variation was from - 4 to + 39°C and the relative humidity ranged from 15 to 60 %. The results of this exposure were compared to that of specimens kept in the shrinkage chamber, with a temperature of 21°C and relative humidity 35%. The current results showed that due to the irreversible nature of shrinkage strain, the drop of ambient temperature and the rise of atmosphere moisture or relative humidity would not reverse the shrinkage strain. It is important to figure the final total accumulated strain when dealing with ambient temperature variation. The drying shrinkage characteristics for concrete made with Type IL cement, are found similar to that for concrete produced with Type I cement.
Highlights
Drying shrinkage is a major cause of the concrete deterioration especially in Middle East region, the acknowledgement of the shrinkage deformation needs to be evaluated
The current results showed that due to the irreversible nature of shrinkage strain, the drop of ambient temperature and the rise of atmosphere moisture or relative humidity would not reverse the shrinkage strain
It is important to figure the final total accumulated strain when dealing with ambient temperature variation
Summary
Drying shrinkage is a major cause of the concrete deterioration especially in Middle East region, the acknowledgement of the shrinkage deformation needs to be evaluated. Sivilis et al [2] concluded that limestone cements, have lower paste water demand than the relative pure cements. Holt and Leivo [3] stated that drying shrinkage is greatly affected by environmental conditions such as wind and humidity in the first days of curing. Revealed that the shrinkage initially tends to be higher for high strength concrete; the ultimate shrinkage strain is larger for normal strain concrete. Khan and Montgomery [5] concluded that the use of milled limestone in self- compacting concrete with suitable content may reduce drying shrinkage of concrete
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