Sinusoidal vibration and impact loading techniques have been tested in the laboratory and on field structures. An impact system has been tested which has proven more economical and versatile than the more commonly used sinusoidal system. With transient loading, a broad band of frequencies (including the resonant frequencies) is applied to the structure simultaneously rather than sweeping through each frequency one at a time. The resonant frequency of a structure is directly related to its dynamic Young's modulus and hence its mechanical integrity. Factors that influence the soundness and safety of a structure such as continuity and boundary conditions also directly affect the resonant frequency. With the availability of digital Fourier analyzers, mathematical functions such as spectra, coherence, and transfer relationships, permit the analysis of the behavior of large structures under dynamic con-ditions in-place and in real-time. Results of laboratory and field tests established the feasibil-ity of determining mechanical properties and assessing other factors that influence the soundness and safety of concrete structures using this nondestructive testing technique.

Rate of wetting by capillary absorption and rate of drying from the saturated state were determined on mature cement pastes with w/c ratios of 0.40 and 0.60. The cumulative water gained or lost was parabolically related to time. The coefficients of this relationship, for both the wetting and the drying data, were two to three orders of magnitude larger for the pastes with w/c = 0.6 than for those with w/c = 0.4.

Concretes containing Class F and Class C fly ashes were evaluated with respect to various aspects of concrete durability. A majority oE concretes with fly ash produced stable air-void systems; however, the volume of air retained over a period of 90 minutes was adversely affected, more in Class F than Class C fly ash concretes. Concretes with fly ash requiring a high dosage of air-entraining admixture generally exhi.bited poor retention of original air content. Organic matter content of the fly ash affected air-entraining admixture dosage and air content stability. Air-entrained concrete with or without fly ash and cured at 73OF (23OC) generally showed good resistance to Ereezing and thawing: however, when these concretes were cured at low temperature, Class F fly ash concretes showed slightly less resistance to freezing and thawing than Class C fly ash concretes. Deicer scaling tests showed that air-entrained concretes without fly ash performed better than fly ash concretes, regardless of curing provided. Both Class C and Class F fly ash concretes exhibited similar performance when subjected to deicer chemicals during freezing and thawing. The chloride-ion penetration of concrete made with fly ash was not signi.Eicantly affected by the class of fly ash. Class F fly ashes were significantly more effective as inhibitors of alkali-silica reaction expansion in mortar bars than were Class C fly ashes. Class F fly ashes significantly improved the sulfate resistance of concrete made with a cement containing 8 % C3A. Concretes with Class C fly ashes exhibited poor performance to sulfate solution.

This paper presents the results of an experimental investigation on the freezing and thawing durability of concretes in which 5 percent of the cement was replaced with cement kiln dust. Three types of cements namely: Type I, II, and 111 were investigated. Six sets of concretes with cement contents of 560 lb/yd3(332 kg/m3) and 650 lb/yd3(386 kg/m3) were tested. The water-cement ratio was 0.52 for the lower cement content and 0.45 for the higher cement content. The air contents of the concretes ranged from 3.1 to 8.4 percent. The freezing and thawing tests were conducted according to ASTM C 666-77 Procedure A, using 4x4~14 in. (102xlO2x356mm) prisms. Weight loss, fundamental resonant transverse frequency, and pulse velocity were measured at approximate intervals of 30 cycles. The freeze-thaw testing was stopped at 300 cycles and the prisms were tested in flexure. The broken specimens were then used to obtain the absorption coefficient. The durability behavior of the various concretes are evaluated by using the relatlive dynamic modulus, durability factor and absorption coefficient. Plastic and hardened concrete properties are also reported. The analysis of the results indicates that a 5 percent replacement of cement with cement kiln dust does not appreciably effect the freeze-thaw durability of concrete. Both the control specimens, as well as specimens containing cement kiln dust exhibited excellent durability.

The soundness of portland cement has a major effect on concrete durability. Mandatory standard specifications have been widely applied to control the manufacture and quality performance of portland cements. Despite these specifications there is evidence in aging concrete to suggest that potential unsoundness, which is due to excessively large amounts of uncombined lime occurring at least intermittently in clinker, is not detected by currently specified tests. This paper indicates that significantly large amounts of uncombined lime are intermittently present in clinker, that its presence is induced by variations in material preparation and in burning conditions during manufacture, and that it remains undetected by current tests. Some possible means of minimizing the amount of uncombined lime in clinker and improving its detection and measurement are discussed.