The construction of a five-mile section of State Highway 121 north of Dallas is currently underway by the Texas Department of Transportation (TxDOT) and involves the conversion of a non-freeway facility to a freeway facility. After much research, TxDOT is mixing, placing, finishing and testing the slipform mainline concrete paving, utilizing TXI's rotary kiln expanded lightweight aggregate as both an intermediate gradation and as a reservoir to provide water to enhance the cement hydration of a typical paving mix. Construction of SH 121 represents the next logical step following research, taking the laboratory to the field in the form of this major highway project.
TxDOT had recently defined new optimized gradations for concrete aggregate that were more uniform. Existing specifications are gap graded with no intermediate sized rock. There are advantages to the new gradations, such as reduced paste content, which will lead to less drying shrinkage cracking, and less susceptibility to freeze thaw damage. TxDOT anticipates higher strengths, leading to a potential reduction in cement, thereby reducing concrete cost. The total cost of the 5.049-mile SH 121 project is $84,322,926.90. Work began in late October 2004 and was completed in 2007.
