Properties of high-volume fly ash concrete incorporating nano-SiO2

This paper presents a laboratory study on the influence of combination of fly ash (FA) and ground granulated blast-furnace slag (GGBS) on the properties of high-strength concrete. A contrast study was carried out for the concrete (GGFAC) incorporating FA and GGBS, control Portland cement concrete and high-volume FA high-strength concrete (HFAC). Assessments of the concrete mixes were based on short- and long-term performance of concrete. These included compressive strength and resistance to H2SO4 attack. The microstructure of the concretes at the age of 7 days and 360 days was also studied by using scanning electron microscope. The results show that the combination of FA and GGBS can improve both short- and long-term properties of concrete, while HFAC requires a relatively longer time to get its beneficial effect.

Properties of concrete incorporating fly ash and ground granulated blast-furnace slag

A parametric experimental study has been conducted to investigate the effect of polypropylene fiber on the workability and durability of the concrete composite containing fly ash and silica fume. Four different fiber volume fractions (0.06%, 0.08%, 0.1% and 0.12%) were used. The results indicate that the addition of polypropylene fiber has a little adverse effect on the workability of concrete composite containing fly ash and silica fume. With the increase of fiber volume fraction, both of the slump and slump flow are decreasing gradually. However, the addition of polypropylene fiber has greatly improved the durability of the concrete composite containing fly ash and silica fume. The length of water permeability, the dry shrinkage strain and the carbonation depth of concrete containing fly ash and silica fume are decreasing gradually with the increase of fiber volume fraction as the fiber volume fraction is below 0.12%. Besides, freeze–thaw resistance of polypropylene fiber reinforced concrete containing fly ash and silica fume was found to slightly increase when compared to the concrete composite without fibers. Moreover, there is a tendency of increase in the freeze–thaw resistance with the increase of fiber volume fraction as the fiber volume fraction is below 0.08%. However, the freeze–thaw resistance begins to decrease slightly after the fiber volume fraction beyond 0.08%.

Effect of polypropylene fiber on durability of concrete composite containing fly ash and silica fume

Laboratory investigation of portland cement concrete containing recycled asphalt pavements

The aim of this study is to evaluate the properties of ground coarse fly ashes, from five sources in Thailand, the shapes, sizes, and chemical compositions of which are completely different. Coarse fly ash was fractionated by an air classifier and ground into three different finenesses ranging from median particle sizes of 1.9–17.2 μm. Physical and chemical properties of the Portland cement and the fly ashes were investigated. Mortar cubes of 5 cm were cast with 20% replacement by weight of Portland cement with ground coarse fly ash. The compressive strengths of the fly ash–cement mortars were determined and compared with the control mortar. The results revealed that the degree of pozzolanic reaction, as determined using compressive strength, of coarse fly ash increased when its fineness was increased by grinding. The strength activity indices of the original fly ash–cement mortars at the curing ages of 7 and 28 days were in the range of 69–82% and 76–90%, respectively. When the particle size smaller than 9 μm of ground coarse fly ash was used, the strength activity index achieved was over 100% of that of the control within 28 days. The results also showed that the fineness of fly ash, not the chemical composition, was the major factor affecting the strength activity index of ground coarse fly ash–cement mortar.

A study of ground coarse fly ashes with different finenesses from various sources as pozzolanic materials

Extensive data are presented on the properties, in the fresh and hardened state, of fly ash concrete containing normal weight and light weight aggregates suitable for structural applications. Tests on reinforced concrete beams and slabs are reported to show that fly ash concrete can exhibit structural performance similar to that of conventional concrete with adequate safety factors and predicted by existing codes.

R. N. Swamy

Papers

Early Strength Fly Ash Concrete for Structural Applications

Steel Fibers for Controlling Crackingand Deflection