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Western U.S. lignite and subbituminous fly ashes have higher CaO + MgO + SO3 and lower Al203 + SiO2 than bituminous ashes. They also have lower loss on ignition and greater proportions of crystalline material. No more than one-third of the total lime is free lime. Several chemically, physically, and mineralogically different lignite and subbituminous fly ashes were used in varying substitutions for portland cement. The following data were obtained: compressive strength, effect of admixtures, freeze-thaw durability, and resistance to sulfate solutions. Depending on the mix proportions, a high lime fly ash may not contribute more to compressive strength than one that has 50 per-cent less lime, and is coarser. High lime fly ashes produce excellent freeze-thaw durability. With certain high lime fly ashes, similar strengths are obtained by either 25 or 75 percent substitution for cement. Extremely low expansions of several high lime fly ash concrete specimens soaking in 10 percent Na2S04 for up to 3 years have indicated that the R factor, (CaO-5)/Fe203, for sulfate resistance is not totally valid. Concretes using high lime fly ashes produce higher early strengths than low lime bituminous ashes.

Lignite Fly Ash (LFA) was used in concrete replacing Portland cement at 0, 30, 40, 50, 60, 70, 80, 9 0 and 100%. Properties investigated in concrete prepared with different percentages of LFA were: 1. Compressive and flexural strengths (7, 28 days 3, 6 months 1, 2, 3, 4 and 8 years). Water to cement plus LFA ratios (W/C+F) 0.55, 0.65, 0.75,0.85, 0.95. Concrete slump 40-50mm, 60-70mm, 80-100mm, lOO-150mm, 150-200mm. A total of 10,000 specimens were tested for compressive strength at various ages during 5 years. 2. Modulus of elasticity according to ASTM C469-65. 3. Bond between steel-concrete according to ASTM C234-71. The test data showed that LFA can replace Portland cement when used as a separate batch material up to 40% in reinforced concrete and up to 70% in plain concrete.

Fly ash in China contains low CaO (5%) and is obtained by burning bituminous coal. Thus such a fly ash concrete exhibits low early strength at an optimal dosage of 10-20%. Two methods were adopted to increase the dosage of fly ash (1) introducing calcium directly during burning or (2) as an additive. The effect of dosage of such fly ash on strength, shrinkage, frost resistance, carbonation and steel corrosion of concrete was investigated. Method 1 is effective in improving the activity of fly ash and permits the optimal dosage of fly ash to increase by 30-4O%. Early strength of concrete is also increased. Method 2 is applicable to steam-cured fly ash concrete at a high dosage (5O-60%). X-ray diffraction analysis was used to study the process of reaction between fly ash and cement.

Data on the mix design, strength and elasticity properties of concrete containing 50% low calcium fly ash replacement and a superplasticizer for 28 day strengths of 20 to 60 MPa are presented. It is shown that for concretes with low water-cement ratios of 0.32 to 0.42, high early strength of 12 to 20 Mpa in one day and 28 day strengths of 45 to 60 MPa can be produced with slumps in excess of 150mm. Under wet curing such concretes can give strength increases of 50 to 100% from 28 days to one year compared to increases of 18 to 25% for all OPC concretes. Even under the worst curing conditions, fly ash concretes showed a slow but steady strength gain and maintained their target strengths at one year whereas all OPC concretes under similar conditions showed strengths of 25 to 35% below the target strength. Air drying always produced greater losses in strength and elasticity in all OPC concretes than in fly ash concretes. The latter were able to develop flexural strengths of 3.5 to 6.0 MPa and tensile splitting strengths of 2.0 to 4.5 MPa at one year under these conditions. The practical and technical benefits of incorporating high fly ash contents are emphasized.

A study was conducted to find the shrinkage and creep of sealed and unsealed concrete made with Type I cement and containing 50% Saskatchewan fly ash. The tests were carried out at different stress/strength ratios and creep was measured at those ratios of: 10, 20, 30, 40, 50, and 60% and for a maximum period of 112 days. All the tests were carried out at room temperature of 70°F (21.4OC). Experimental results showed that creep of concrete made with 50% fly ash was a linear function of stress/strength ratio. The shrinkage of this concrete was about 11% higher than that of plain concrete, while its creep was lower by about 13% for the unsealed specimens and 39% for the sealed ones. In addition, the ratio of creep values of unsealed/sealed concrete was about 2.44 for plain concrete and 3.67 for concrete with 50% fly ash.