Weerachart Tangchirapat

Use of High Fineness of Fly Ash to Improve Properties of Recycled Aggregate Concrete

This study used high fineness of fly ash as a cement replacement to improve recycled aggregate concrete properties. The mixture proportions of recycled aggregate concretes were first prepared using 100% recycled coarse aggregate, and then river sand was replaced with recycled fine aggregate at 0, 50, and 100% by weight of the fine aggregate (river sand plus recycled fine aggregate). Results indicated that use of 35–50% fly ash (with respect to total cementitious content) of high fineness could improve slump loss behavior in recycled aggregate concretes. Greater proportions of recycled fine aggregates decreased the compressive strength of concrete. However, use of high fineness of fly ash (1.2% retained on a No. 325 sieve) in recycled aggregate concrete could produce greater compressive strength than that of the recycled aggregate concrete alone. The splitting tensile strength of the recycled aggregate concretes containing high fineness of fly ash was 8.2% of its compressive strength, slightly lower than that of the normal aggregate concrete. The modulus of elasticity of recycled aggregate concrete, with or without high fineness of fly ash, was lower than that of the normal aggregate concrete and about 5.9% lower than the value predicted by ACI 318. The results suggest that high fineness of fly ash can be used to improve various properties of recycled aggregate concrete.

Influence of Fly Ash on Slump Loss and Strength of Concrete Fully Incorporating Recycled Concrete Aggregates

This paper investigates the effects of fineness and replacement of fly ash on the fresh and hardened properties of recycled aggregate concrete. Two groups of recycled aggregate concretes were studied and compared with that of conventional concrete (CON) in which crushed limestone and local river sand were used as aggregates. The first group was prepared using 100% coarse recycled concrete aggregate and local river sand. For the second group, crushed limestone and local river sand were fully replaced by both coarse and fine recycled concrete aggregates. The results indicate that the slump loss of the recycled aggregate concrete with fly ash was reduced to lower than that of the recycled aggregate concrete without fly ash when the fineness of the fly ash was increased, which increased the slump loss of the fresh concrete. Fly ash can be used to increase the compressive strength of recycled aggregate concrete, depending on its fineness and the degree of fly ash replacement. The addition of fly ash with different fineness in recycled aggregate concrete had no significant effect on the splitting tensile strength and the modulus of elasticity of the recycled aggregate concrete, which are related to its compressive strength.

Influence of Palm Oil Fuel Ash and W/B Ratios on Compressive Strength, Water Permeability, and Chloride Resistance of Concrete

This research studies the effects of W/B ratios and palm oil fuel ash (POFA) on compressive strength, water permeability, and chloride resistance of concrete. POFA was ground until the particles retained on sieve number 325 were less than 5% by weight. POFA was used to partially replace OPC at rates of 15, 25, and 35% by weight of binder. The water to binder (W/B) ratios of concrete were 0.40 and 0.50. The compressive strength, water permeability, and chloride resistance of concrete were investigated up to 90 days. The results showed that POFA concrete with W/B ratio of 0.40 had the compressive strengths ranging from 45.8 to 55.9 MPa or 82–94% of OPC concrete at 90 days, while POFA concrete with W/B ratio of 0.50 had the compressive strengths of 33.9–41.9 MPa or 81–94% of OPC concrete. Furthermore, the compressive strength of concrete incorporation of ground POFA at 15% was the same as OPC concrete. The water permeability coefficient and the chloride ion penetration of POFA concrete were lower than OPC concrete when both types of concrete had the same compressive strengths. The findings also indicated that water permeability and chloride ion penetration of POFA concrete were significantly reduced compared to OPC concrete.

Influence of Activation Methods on Strength and Chloride Resistance of Concrete Using Calcium Carbide Residue–Fly Ash Mixture as a New Binder

AbstractThis research aimed to investigate the compressive strength and chloride resistance of concrete made with 30% of calcium carbide residue (CCR) and 70% fly ash (FA) as a binder without portl...

Environmentally friendly interlocking concrete paving block containing new cementing material and recycled concrete aggregate

Abstract This paper investigates the properties of concrete block made from industrial waste materials. Two by-products, calcium carbide residue (CR) and bagasse ash (BA), were combined and used as a substitute binder for Portland cement, and 100% recycled concrete aggregate (RCA) was used to replace natural aggregate in making interlocking concrete paving block. The results showed that the densities of the concrete blocks with unmodified CR and BA as a binder were decreased, moreover, their water absorptions were higher than those of concrete blocks with high fineness of binder. The compressive strength of some concrete block can be sufficiently high to meet the requirement for interlocking concrete paving block in accordance with Thai Industrial Standard (TIS 827), which is higher than 40.0 MPa at the testing age of not less than 7 days. The abrasion resistance of concrete block is likely to be decreased compared to normal concrete due to the RCA in the mixture; however, the abrasion resistance can be improved by increasing the fineness of binder. These remarkable results indicate that CR, BA and RCA in suitably mixed proportions can be used as a good choice for an alternative material to make environmentally friendly interlocking concrete paving block.