Chai Jaturapitakkul

Comparative study on the characteristics of fly ash and bottom ash geopolymers.

This research was conducted to compare geopolymers made from fly ash and ground bottom ash. Sodium hydroxide (NaOH) and sodium silicate (Na(2)SiO(3)) solutions were used as activators. A mass ratio of 1.5 Na(2)SiO(3)/NaOH and three concentrations of NaOH (5, 10, and 15M) were used; the geopolymers were cured at 65 degrees C for 48 h. A Fourier transform infrared spectrometer (FT-IR), differential scanning calorimeter (DSC), and scanning electron microscope (SEM) were used on the geopolymer pastes. Geopolymer mortars were also prepared in order to investigate compressive strength. The results show that both fly ash and bottom ash can be utilized as source materials for the production of geopolymers. The properties of the geopolymers are dependent on source materials and the NaOH concentration. Fly ash is more reactive and produces a higher degree of geopolymerization in comparison with bottom ash. The moderate NaOH concentration of 10 M is found to be suitable and gives fly ash and bottom ash geopolymer mortars with compressive strengths of 35 and 18 MPa.

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

Abstract 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.

USE OF GROUND COARSE FLY ASH AS A REPLACEMENT OF CONDENSED SILICA FUME IN PRODUCING HIGH-STRENGTH CONCRETE

Abstract This paper presents a method of improving coarse fly ash in order to replace condensed silica fume in making high-strength concrete. The coarse fly ash, having the average median diameter about 90–100 μm, yields a very low pozzolanic reaction and should not be used in concrete. In order to improve its quality, the coarse fly ash was ground until the average particle size was reduced to 3.8 μm. Then, it was used to replace Portland cement type I by weights of 0%, 15%, 25%, 35%, and 50% to produce high-strength concrete. It was found that concrete containing the ground coarse fly ash (FAG) replacement between 15% and 50% can produce high-strength concrete and 25% cement replacement gave the highest compressive strength. In addition, the concrete containing FAG of 15–35% as cement replacement exhibited equal or higher compressive strengths after 60 days than those of condensed silica fume concretes. The results, therefore, suggest that the FAG with high fineness is suitable to use to replace condensed silica fume in producing high-strength concrete.

Compressive Strength and Heat Evolution of Concretes Containing Palm Oil Fuel Ash

The study of using palm oil fuel ash (POFA) in concrete work is just the beginning, and obtained data are very little as compared to fly ash and silica fume. In order to collect experimental data, the effects of ground POFA (GPOFA) replacement rate up to 30 wt % and water/binder (W/B) ratios of 0.50, 0.55, and 0.60 on normal concrete properties were studied. GPOFA with high fineness was found to be a possible pozzolanic material in concrete. Cement replacement of GPOFA at rates of 10 and 20% yielded higher compressive strength than that of control concrete after 28 days of curing. In addition, heat evolution in terms of temperature rise of fresh concrete decreased with an increased of GPOFA replacement. For concrete with a W/B ratio of 0.50, the use of 30% GPOFA as a cement replacement exhibited the lowest peak temperature rise. However, a decrease compressive strength at early age might be considered if a high replacement rate of GPOFA was used.

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.

Silicate-, aluminosilicate and calciumsilicate gels for building materials: chemical and mechanical properties during ageing

Silicate, aluminosilicate and calciumsilicate concretes, cements, and mortars were synthesized based on rice husk-bark ash, fly ash, slag and metakaolin. Alkali activation was done using sodium and potassium waterglass solutions. The hardening of the concretes and mortars was investigated in dependence on time by compressive strength measurements. The ageing of cement pastes was followed by infrared absorption spectroscopy. The infrared absorption peaks were evaluated in comparison to spectra obtained for silicate and aluminosilicate glasses and condensates from waterglass solutions. The increase in compressive strength of the materials at the beginning of ageing can be explained by the development of two main structural units on different time scales: a fast formation of silicate chain type units of considerable length and a slow formation of a silicate – and in presence of Al – aluminosilicate three-dimensional network enclosing the chains. The protection of the chains against destruction becomes crucial for long term high strength. Alkali activation of slag containing significant amounts of CaO leads to the formation of calcium silicate hydrate type phases and strongly enhanced mechanical strength.

Leaching of heavy metals from solidified waste using Portland cement and zeolite as a binder

This study investigated the properties of solidified waste using ordinary Portland cement (OPC) containing synthesized zeolite (SZ) and natural zeolite (NZ) as a binder. Natural and synthesized zeolites were used to partially replace the OPC at rates of 0%, 20%, and 40% by weight of the binder. Plating sludge was used as contaminated waste to replace the binder at rates of 40%, 50% and 60% by weight. A water to binder (w/b) ratio of 0.40 was used for all of the mixtures. The setting time and compressive strength of the solidified waste were investigated, while the leachability of the heavy metals was determined by TCLP. Additionally, XRD, XRF, and SEM were performed to investigate the fracture surface, while the pore size distribution was analyzed with MIP. The results indicated that the setting time of the binders marginally increased as the amount of SZ and NZ increased in the mix. The compressive strengths of the pastes containing 20 and 40wt.% of NZ were higher than those containing SZ. The compressive strengths at 28 days of the SZ solidified waste mixes were 1.2-31.1MPa and those of NZ solidified waste mixes were 26.0-62.4MPa as compared to 72.9MPa of the control mix at the same age. The quality of the solidified waste containing zeolites was better than that with OPC alone in terms of the effectiveness in reducing the leachability. The concentrations of heavy metals in the leachates were within the limits specified by the US EPA. SEM and MIP revealed that the replacement of Portland cement by zeolites increased the total porosity but decreased the average pore size and resulted in the better containment of heavy ions from the solidified waste.

Effects of Calcium Carbide Residue–Fly Ash Binder on Mechanical Properties of Concrete

This study investigated the use of two kinds of waste from landfills, calcium carbide residue and fly ash, as a low CO2 emission concrete binder. Calcium carbide residue is a by-product of an acetylene gas production process, and fly ash is a by-product of a thermal power plant. Ground calcium carbide residue (CR) was mixed with original fly ash (OF) or ground fly ash (GF) at a ratio of 30:70 by weight and was used as a binder to cast concrete without portland cement. The effects of fly ash finenesses and water to binder ( W/B ) ratios of CR-OF and CR-GF concretes on setting times, compressive strength, modulus of elasticity, and splitting tensile strength were investigated. The results indicated that CR-OF and CR-GF mixtures could not only be used as a new binder in concrete but could also help reduce environmental problems associated with CO2 emissions. Without the use of portland cement, CR-GF concrete yielded compressive strengths of 28.4 and 33.5 MPa at 28 and 90 days, respectively. In addition, lowe...

Effect of insoluble residue on properties of Portland cement

Abstract Insoluble residue is a non-cementing material which is present in Portland cement. This residue material affects the properties of cement, especially its compressive strength. To control the non-cementing material in Portland cement, ASTM standard allows the insoluble residue to be not higher than 0.75%. This limitation is much lower than the allowance provided by the British standard which is 1.5%. To verify the effect of insoluble residue on the properties of Portland cement, artificial insoluble residue was prepared and replaced in Portland cement type I. Finely crushed sand was extracted to represent artificial insoluble residue. Setting times and compressive strengths of cement mortar mixed with insoluble residue were investigated. The Portland cement was replaced by insoluble residue which varied in amounts of 0%, 0.5%, 1.0%, 1.5%, 2.0%, 3.0%, 5.0% and 7.0% by weight. The results showed that the addition of the insoluble residue from 0.0% to 7.0% by weight in Portland cement did not affect the normal consistency or setting times of cement. However, the compressive strength of cement mortar was affected during the early age, but the figure reduced as the cement mortar was older. With 7.28% of insoluble residue in the mortar at 1 day, the compressive strength was reduced by 11.5%, but after 60 days, the strength of the same mortar was only reduced by 5.5% as compared to the control mortar. It was also found that the compressive strength of Portland cement mortar with insoluble residue provided by ASTM standard or British standard was still higher than the compressive strength of Portland cement mortar type I allowed by the standards. The limit of insoluble residue given by ASTM standard as 0.75 is rather low and can possibly be increased to 1.5% according to British standard, or even slightly higher, without significantly reducing the compressive strength of cement.

Cellular lightweight concrete containing high-calcium fly ash and natural zeolite

Cellular lightweight concrete (CLC) with the controlled density of approximately 800 kg/m3 was made from a preformed foam, Type-I Portland cement (OPC), fly ash (FA), or natural zeolite (NZ), and its compressive strength, setting time, water absorption, and microstructure of were tested. High-calcium FA and NZ with the median particle sizes of 14.52 and 7.72 μm, respectively, were used to partially replace OPC at 0, 10wt%, 20wt%, and 30wt% of the binder (OPC and pozzolan admixture). A water-to-binder mass ratio (W/B) of 0.5 was used for all mixes. The testing results indicated that CLC containing 10wt% NZ had the highest compressive strength. The replacement of OPC with NZ decreased the total porosity and air void size but increased the capillary porosity of the CLC. The incorporation of a suitable amount of NZ decreased the setting time, total porosity, and pore size of the paste compared with the findings with the same amount of FA. The total porosity and cumulative pore volume decreased, whereas the gel and capillary pores increased as a result of adding both pozzolans at all replacement levels. The water absorption increased as the capillary porosity increased; this effect depended on the volume of air entrained and the type or amount of pozzolan.