Constructed of concrete designed to last 1,000 years, the raft foundation for the BAPS temple in Stafford, Texas, could potentially join the ranks of innumerable ancient structures that have withstood the elements for centuries, project officials contend. The Colosseum, built in 80 A.D., and the Pantheon dating from 120 A.D., they add, epitomize the height of durability that can be achieved through proper and careful selection of materials.

Evangelical professor P.K. Mehta, Emeritus Professor, University of California at Berkeley, is the advisor for the BAPS temple project. Dr. Shondeep Sarkar, P.E., of Houston-based Sarkar & Associates, Inc., developed and optimized proportions for the concrete mix comprising high-volume fly ash (nearly 68.5 percent by mass of Class F fly ash), as little as 150 lb/yd³ portland cement, and local aggregates consisting of a 2:1 mixture of crushed limestone and pea gravel. Jatin Desai, P.E., and his team of engineers at Maverick Engineering, Inc., Houston, designed the structure, while the concrete was supplied by TXI.

The foundation slab, approximately 10,000 sq. ft. in area, is supported by 244 piers containing up to 50 percent by mass of fly ash. The piers run 30 ft. deep with diameters ranging from 30 to 54 in. The first three feet of the new generation of environmentally friendly, high-volume fly ash concrete were placed in early summer. The slab thickness varies from five feet minimum to 11 feet in places. A total of nearly 5,000 yd. of concrete will be used for the foundation slab.

Corrosion of reinforcing steel stands out as one of the primary factors causing concrete to deteriorate prematurely. Given the relatively short service life of reinforced concrete, an obvious solution would be to use a nonreinforced slab. On the other hand, synthetic reinforcements have a relatively short track record. Consequently, BAPS opted for a high-volume fly ash and low cement content concrete for its foundation.

The slow strength development of this mix allows for low modulus at an early age, yielding a significantly reduced potential for cracking. In fact, the strength criteria are not onerous; but to meet the design yardstick of a 1,000-year service life, micro- and macro-cracking in the nonreinforced concrete are of paramount concern. Accordingly, the concrete was designed to be free from cracking by virtue of a very low cement/water ratio, low modulus of elasticity at early ages as well as minimal temperature rise and thermal gradient.

HIGH-VOLUME FLY ASH CONCRETE