Thermal expansion of concrete aggregate materials

Abstract

As a part of a study of the properties of concrete aggregates, thermal-expansion determinations were made on 123 specimens of aggregate materials by the optical interferometer method over the temperature range-20° to + 60° C. Additional measurements were made on crystals of calcite, quartz, and feld spar; The thermal expansivities of most aggregate materials are close to or within the range of expansivities of hardened portland cements. Certain exceptions are pointed out. Crystal orientation, rock texture, and composition are discussed with regard to their effects on the relation of the thermal expansion of aggregates to the durability of concrete. I. II. III. IV. V. VI. VII. CONTENTS Page Introduction ________ _________ _______________ _______ ____ ____ ____ 101 Previous work _____ ___ ____________ ______________________________ 102 Test method _______________________________ __________________ __ 103 1. Apparatus and calibration ________________ _______________ __ 103 (a) General description ___ __ ___ _____ _______________ ___ 103 (b) Establishment of heating and cooling schedule _ _ _ _ _ _ _ _ 104 (c) Calibration of thermocouple and refraction thermometer _______________________________________ 104 (d) Determination of temperature lag in test specimen ____ 105 2. Preparation of specimens __________________________________ 105 3. T est procedure ___________________________________________ 106 4. Reliability of results ____ __ _______________________________ 107 Description of materials tested ___________________________________ 107 Results and discusRion ___ ____________________________ _____ ______ __ 115 1. Effect of crystal orientation _____ __________________________ 115 2. Effect of composition difference _______ _____ ________________ 118 3. Effect of texture_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 119 4. Materials with irregular expansion ___________________________ 121 5. Comparison of present results with previous work ____________ 123 6. Aggregate expansivity in relation to concrete ___________ _____ 124 Summary ______________________ : _______________________________ 125 References ________________________________________ _____________ 126