4 PREFACE 



given. Each of these projects is analyzed into its sequential 

 operations with numerous references to the previous projects 

 for specific details. Many supplementary projects are pro- 

 vided. 



The authors are indebted to their many friends who have 

 given freely of their material and advice. They wish partic- 

 ularly to acknowledge the use of material furnished by the 

 University of Illinois, the University of Missouri, the Iowa 

 State College, the Portland Cement Association, and of cuts 

 furnished by several trade journals and taken from state 

 bulletins. 



FRED D. CRAWSHAW. 



E. W. LEHMANN. 



