Concrete, when made with hot lime or cement, swells to an extent amounting to 1/8-3/8 in. per foot of its linear dimensions. This is owing to the imperfect slaking or cooling of the lime or cement. It is probable that when such expansion takes place there is a slight disintegration throughout the mass of concrete, and that its coherence is destroyed. It has been ascertained by experiment that when lime is carefully slaked, the concrete does not expand at all, and concrete should be so carefully prepared that no expansion will take place. The expansion which occurs in concrete made with hot lime or cement has, however, been taken advantage of in "underpinning" walls that have settled in parts; hot concrete forced tightly into openings made below the faulty portions expands and sets, filling the opening, and lifting the superincumbent work into its proper position.

An indispensable guide to those interested in concrete construction is Reid's 'Practical Treatise on Natural and Artificial Concrete.'