3.1.1
Concrete Mixtures
A summary of the mixtures design is provided in Table 2. The HES mixture was designed to meet standards provided by Pennsylvania Department of Transportation (PennDOT) for a 7-hr accelerated mix design whereas the conventional concrete mix was designed to meet PennDOT requirements for LLCP. Both mixes used Type I/II Portland cement with Type F fly ash. The coarse aggregates included #57 limestone and #8 sandstone, and the fine aggregate was concrete sand. Table 2: Mixture design details
Cement (lbs) Pozzolan 1 (lbs) Total Cementitious (lbs) Coarse Aggregate 1 (lbs) Coarse aggregate 2 (lbs) Total Coarse Aggregate (lbs) Fine Aggregate (lbs) Total Water (lbs) W/C Ratio Unit Weight (lbs/cu.ft) 3.1.2
High Early Strength Mix 600 150 750 1309 396
Long-Life Conventional Paving Mix 477 134 611 1357 410
1705
1767
1158 236 0.315 142.93
1161 249 0.408 141.03
Laboratory and Field Testing
Three types of testing were conducted for this field study: conventional laboratory strength testing, maturity, and ultrasonic tomography. Laboratory testing was performed on cylinder and beam specimens to determine concrete strength in different ages. Maturity and ultrasonic data were collected on both the laboratory specimens and on the slabs in the field. 3.1.2.1 Laboratory Strength Testing Compressive and flexural strength testing were performed (Figure 5). Cylinder and beam specimens were cast from concrete collected during the construction of slabs HES1 (HES) and C1.1 (LLCP). Standards ASTM C39, for compressive strength using 4 x 8-inch cylinders, and ASTM C78, for flexural strength using third-point loading, were applied (ASTM C39, 2015; ASTM C78, 2008). For the HES mix, compressive strength was estimated at 3, 5, 7, and 24 hours post construction. HES beams were only tested at 7 hours to determine the flexural strength at the suggested opening time. For the LLCP mix, both flexural and compressive
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