EARLY AGE AND LONG TERM STRENGTH OF MIXES MADE WITH STALITE LIGHTWEIGHT AGGREGATE CAROLINA STALITE COMPANY RESEARCH LAB GOLD HILL, NORTH CAROLINA

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1 EARLY AGE AND LONG TERM STRENGTH OF MIXES MADE WITH STALITE LIGHTWEIGHT AGGREGATE CAROLINA STALITE COMPANY RESEARCH LAB GOLD HILL, NORTH CAROLINA RESEARCH BY: JODY R WALL, P.E. DIRECTOR RESEARCH AND DEVELOPMENT STEVEN MALOOF TECHNICAL REPRESENTATIVE

2 On May 28, 2003 three concrete mixes were produced at Carolina Stalite s laboratory in Gold Hill, North Carolina. The mixes were similar to those recommend by Stalite for 3000, 4000 and 5000-psi concrete production. The mixes were labeled, which is a standard 3000 psi mix design recommended by Stalite,, which is a standard 3000 psi mix design recommended by Stalite,, which is a standard 3000 psi mix design recommended by Stalite, and NW which is a typical 3500 to 4000 psi normal weight mix design. The materials used for the mixes were Lafarge Type I/II cement, Hedrick concrete sand from Lilesville North Carolina, normal weight #67 stone from Vulcan Materials Cabarrus Quarry, Stalite ¾ to #4 rotary kiln expanded slate lightweight aggregate and local water. The mix proportions and fresh properties are list below. Mix Design Material NW 1 Cement Stalite ¾ Lightweight Normal weight Stone Natural Sand Water WRDA 35 oz/cmt AEA 1400 oz/cmt Fresh Properties Material NW 1 Slump (in.) Air Content (%) Temperature(º F) Plastic Density (pcf) The set time of the above concrete mixtures was determined in accordance with ASTM standards. Set Time Time (Hours) Penetrometer Reading (psi) NW

3 The results show a similar set time for the lightweight concrete mixtures and the normal weight comparison mixture. SET Time Penetrometer Reading (PSI) NW Time (Hrs) The compressive strength of the mixtures was determined in accordance with ASTM standards. Compressive Strength (psi) 12 hr hr hr hr hr hr hr The lightweight mixtures show compressive strengths similar to the normal weight comparison mixture at 48 hours. For precast/prestress applications this is important in determining bed turnaround times. With the lightweight concrete mixes tested using expanded slate lightweight aggregate the bed turnaround time can be estimated the same as for similar normal weight concrete mixtures.

4 Compressive Strength fc' (PSI) Concrete Strength vs Time 0 to 2 days Time (days) NW 1 Log. () Log. () Log. () Log. (NW 1) Compressive Strength (psi) 7 DAYS DAYS DAYS DAYS DAYS DAYS DAYS DAYS DAYS DAYS

5 Concrete Strength vs Time 0 to 7 Days Compressive Strength fc' (PSI) Time (days) NW 1 Log. () Log. () Log. () Log. (NW 1) Concrete Strength vs Time 0 to 90 days Compressive Strength fc' (PSI) NW 4 Log. () Log. () Log. () Time (days) Log. (NW 4) The Modulus of elasticity of the concrete mixtures was determined in accordance with ASTM standards. The cylinders were moist cured until testing age. 4 x8 cylinders were tested at 7, 28, 56, 90, 180 and 365 days. The unit weight of the mixtures was determined in accordance with ASTM C567. The following tables show the concrete compressive strength, modulus of elasticity and density at ages of 7 to 365 days. The tables also show the calculated modulus of elasticity

6 based on the Georgia institute of technology document, the ACI 363 modified prediction model and the ACI 318 model referenced in ACI 213. Modulus of Elasticity (psi) 7 DAYS 2.81E E E E DAYS 3.42E E E E DAYS 3.18E E E E DAYS 3.35E E E E DAYS 3.53E E E E DAYS 3.38E E E E DAYS 3.74E E E E DAYS 3.70E E E E DAYS 3.37E E E E DAYS 3.47E E E E+06 The positive numbers in the variance charts below represent overestimation by the models and negative numbers represent underestimations by the models. The tables below show that the ACI 363 model is the most accurate prediction of modulus of elasticity for lightweight concrete with compressive strengths in the range tested. The testing showed that the ACI 318 model overestimated the modulus of elasticity for expanded slate lightweight aggregate concrete by about 10% on average. The testing showed the Georgia Institute of Technology model to be extremely accurate at strengths above 8000 psi. Modulus of Elasticity Predicted by ACI DAYS 3.13E E E E DAYS 3.71E E E E DAYS 3.56E E E E DAYS 3.65E E E E DAYS 3.72E E E E DAYS 3.56E E E E DAYS 3.62E E E E DAYS 3.76E E E E DAYS 3.82E E E E DAYS 3.80E E E E+06

7 Modulus of Elasticity Variance from ACI DAYS 10.09% 14.16% 11.17% 16.22% 28 DAYS 7.96% 13.63% 16.30% 12.16% 28 DAYS 10.63% 8.11% 8.38% 18.47% 56 DAYS 8.24% 5.66% 10.28% 23.49% 90 DAYS 5.23% 12.71% 17.12% 14.91% 90 DAYS 5.11% 10.95% 10.84% 12.39% 180 DAYS -3.33% 3.60% 8.03% 18.16% 180DAYS 1.40% 12.70% 5.55% 11.61% 365 DAYS 11.87% 6.82% 8.22% 8.90% 365 DAYS 8.70% 11.90% 8.51% 1.27% Modulus of Elasticity Predicted by ACI 363 modified 7 DAYS 2.96E E E E DAYS 3.36E E E E DAYS 3.25E E E E DAYS 3.31E E E E DAYS 3.35E E E E DAYS 3.24E E E E DAYS 3.28E E E E DAYS 3.37E E E E DAYS 3.41E E E E DAYS 3.40E E E E+06 Modulus of Elasticity Variance from ACI DAYS 5.06% 7.10% 3.15% 10.52% 28 DAYS -1.77% 7.25% 9.67% 5.49% 28 DAYS 2.14% -1.15% -2.72% 10.24% 56 DAYS -1.37% -5.08% 0.13% 14.99% 90 DAYS -5.22% 2.22% 5.53% 5.71% 90 DAYS -4.25% -0.22% -1.23% 2.61% 180 DAYS % -8.42% -4.12% 8.36% 180DAYS -9.87% 1.18% -7.56% 1.19% 365 DAYS 1.35% -4.75% -4.10% -1.74% 365 DAYS -2.08% 0.79% -4.01% %

8 Modulus of Elasticity Predicted by Georgia Tech Model 7 DAYS 3.43E E E E DAYS 3.65E E E E DAYS 3.59E E E E DAYS 3.62E E E E DAYS 3.65E E E E DAYS 3.58E E E E DAYS 3.60E E E E DAYS 3.66E E E E DAYS 3.68E E E E DAYS 3.67E E E E+06 Modulus of Elasticity Variance from Georgia Tech Model 7 DAYS 18.05% 17.10% 13.01% 11.47% 28 DAYS 6.50% 18.18% 20.09% 5.49% 28 DAYS 11.44% 7.88% 3.92% 7.34% 56 DAYS 7.46% 2.53% 7.63% 10.97% 90 DAYS 3.27% 8.71% 9.62% 1.93% 90 DAYS 5.73% 6.07% 3.93% -1.73% 180 DAYS -3.88% -1.49% 1.66% 3.17% 180DAYS -1.27% 6.85% -2.23% -3.75% 365 DAYS 8.50% 2.35% 1.73% -6.67% 365 DAYS 5.47% 7.35% 1.49% % Variance from ACI 318 vs Compressive Strength Variance % 18.00% 16.00% 14.00% 12.00% 10.00% 8.00% 6.00% 4.00% 2.00% 0.00% 10.09% 16.30% 14.16% 13.63% 11.17% 10.63% 8.11% 8.24% 7.96% 5.11% 10.28% 5.66% 5.23% % 8.38% 10.95% 3.60% Compressive Strength f'c 8.03% 10.84% 17.12% LW1

9 E-Modulus vs Concrete Strength Lightweight Mixes 4.10E E+06 E-Modulus (PSI) 3.70E E E E E+06 Log. () Log. () Log. () 2.70E E Concrete Strength, fc' (PSI)