Effect of calcium chloride on portland cements and concretes

Abstract

To study the effect of the addition of calcium chloride on portland cements of widely varying composition, and on portland-cement concretes, a carefully controlled laboratory investigation was conducted. Such measurements as heats of hydration, setting times, consistencies and the strengths at various ages under several curing temperatures were made. The addition of calcium chloride appears to increase somewhat the heat contributed at the end of 24 hours by dicalcium silicate and tetracalcium alumino-ferrite and to decrease the heat contributed by tricalcium aluminate. Calcium chloride has but little effect on the heat contributed by tricalcium silicate. Calcium chloride increases the rate at which the heat is evolved from all cements. The strength contributed by the two silicate compounds in cement was increased and the strength contributed by tricalcium aluminate was decreased by the addition of calcium chloride. Calcium chloride decreased the time of set of 11 commercial cements and increased the flow and the strength of the resulting concrete. The physical properties of the experimental cements were similarly affected by the addition of calcium chloride. The optimum amounts to be added for different types of cement and at various curing temperatures are indicated. CONTENTS Page I. Introduction ___________________________________________________ 499 II. Description of cements and calcium chloride ______________________ __ 500 III. Effect of calcium chloride on the heat evolved during the first 24 hours of hydration _______________________________ _________ ____ ___ __ 500 1. Heat of hydration of experimental cements ________ __________ 500 2. Heat of hydration of 11 commercial cements ________________ 502 IV. Effect of calcium chloride on the physical properties of mortars and concretes ________________________ ___ _____ _____________ ___ ____ 504 1. Strength of experimental cements_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 504 2. Commercial cements _____ ___ _______________ ______________ 508 (a) Making the test specimens _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 508 (b) Test results ___________ ____ __ _____________ _______ 508 (1) Time of set ___ ___________________________ 508 (2) Strengths ________ ________________________ 509 (3) Plasticity t ests ____ ____