Influences of a composite addition on the strength of mortar and shrinkage of cement paste

摘要

The influences of a composite addition on the strength of mortar as well as the shrinkage of cement paste were investigated. Portland cement, fly ash and a composite addition were used in binary and ternary cementitious blends. The composite addition used in this research was composed of an ultrafine dust collected from iron-smelting furnaces and a small amount of alkali chemicals. The test results indicate that the use of fly ash and the composite addition in the ternary blends enhanced the strength noticeably, especially at early age. Incorporation of the addition resulted in an increase of autogenous shrinkage, but the total shrinkage at 90 days was close to the control specimen when the sealed curing period was longer than 7 days. The longer the specimen cured under sealed conditions, the smaller the total shrinkage produced. An abrupt increase of drying shrinkage was observed as soon as the specimen was demoulded, no matter how long the specimen was cured under sealed conditions.