2. The compressive strength of PFA concrete should be greater than 

 that of regular lightweight concrete because the individual aggregate 

 particles are stronger. Concrete strength is usually controlled by the 

 strength of the aggregate particles. Regular lightweight aggregate 

 particles have about 50% void volume, which is the cause of a relatively 

 weak particle strength. PFA particles have the void volume filled with 

 polymer which imparts added strength to the particles and should result 

 in higher compressive strengths for lightweight concretes. 



3. The elastic moduli for PFA and regular lightweight concrete 

 will be similar. This is beneficial for applications which require a 

 relatively low elastic modulus and a nonlinear material response near 

 ultimate conditions. 



Polymer impregnation techniques are available for filling all the 

 voids in the concrete (i.e., the cement voids and the aggregate voids), 

 but this method causes the elastic modulus to increase to about twice 

 that of nonimpregnated concrete and the material exhibits brittle behavior 

 at near ultimate load conditions. These are undesirable characteristics 

 in some cases. The desirable features of im.pregnating the concrete with 

 polymer are that three- to four-fold increases in compressive strength 

 and two-fold increases in tensile strength can be expected. Research on 

 polymer impregnated concrete is reported elsewhere." This report was 

 concerned with determining the strength properties of PFA lightweight 

 concrete. 



SCOPE 



In this test program four mix designs of PFA concrete and correspond- 

 ing control specimens of regular lightweight concrete (same aggregate 

 but not polymer-filled) were investigated. Fifteen specimens 4 inches 

 in diameter by 8 inches long were made for each batch of concrete. Six 

 specimens were tested in compression, of which three were instrumented 

 for strain to obtain elastic moduli and Poisson's ratio data; five 

 specimens were tested in split tension; and two specimens each were 

 placed in a 30% relative humidity (RH) environment and a pressure vessel 

 at 500 psi to obtain unit weight data. 



MATERIALS 



Regular Lightweight Aggregate 



Regular lightweight aggregate for structural grade concretes is 

 typically a manufactured product made by using heat to expand naturally 

 occurring shales, clays, and slates and industrial by-products such as 

 clay and pelletized fly ash. In all cases, the aggregates are light in 

 weight because of an internal cellular structure of the individual 

 aggregate particles. 



"American Concrete Institute. ACl SP-58: Polymers in Concrete - Inter- 

 national Symposium. Detroit, Mich., 1978, 425 pp. 



