Evaluation of Hydraulic Cement Concretes Containing Slag Added at the Mixer

About the report:

The study evaluated the effect of ground-granulated, iron blast-furnace slags on the properties of hydraulic cement concretes such as normally used in highway construction. Two cements with different alkali contents and two slags with different activity indices were used. Slags were used as replacements for portions of portland cement at 40%, 50%, and 65% by weight. This interim report presents the data on the properties of the freshly mixed concrete and the test results on time of set, heat of hydration, compressive strength, flexural strength, permeability, resistance to freezing and thawing, air void system of the hardened concrete, and the length change values for 32 weeks. Results of the studies on carbonation and hydration and the additional length change data will be included in the final report. The test results for the laboratory specimens indicate that mixtures with the slags exhibit delay in set and slower development of compressive strength at early ages, but have-equal or better strengths at later ages. The incorporation of slag reduces the permeability of concrete considerably. The resistance to cycles of freezing and thawing of air entrained concretes with and without slags was satisfactory when tested for 300 cycles in 2% NaCI solution. However, generally higher surface scaling was observed on the mixtures with the slags. It is concluded from this study that concretes in which up to 50% by weight of the cement has been replaced with a slag meeting the requirements of ASTM C989 and having a minimum activity index of I00 are satisfactory for highway construction.

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