In January 2005, TXI, with Austin Bridge and Road as general contractor,
started one of the largest internal curing paving projects in the United
States. From January to June 2005, TXI produced and Austin Bridge and
Road placed 250,000 cubic yards of concrete paving for the Union Pacific
Inter-modal Facility located south of Dallas, Texas. What was unique
about the concrete paving mix is that it contained a medium gradation of
expanded shale aggregate in conjunction with limestone aggregate and
concrete sand. The reason for the addition of the expanded shale
aggregate was to promote the internal curing properties of this low
slump, low water cement ratio, high strength concrete mix.
The construction phase of the project spanned the seasonal temperature
extremes of Texas from cold and wet to hot and dry weather conditions.
Through it all, TXI Hydromax concrete mix performed well in ease of
placement of the 3-inch max slump concrete mix. The 28-day compressive
strengths averaged 1000 PSI higher than the required 28-day strengths
and the 28-day flexural strengths were easily obtained within 3 days.
Post construction observations of the pavement, in place for four years,
show minimal cracking in a massive concrete paving project that is used
daily by heavy trucks to move several million tons of cargo annually.
This is an excellent testament of expanded shale aggregate improving the
durability, strength, and quality of concrete paving.
