Effect of calcination temperature on the pozzolanic activity of sugar cane bagasse ash

This work presents the results of the processing of sugar cane bagasse ash (SCBA) under controlled calcination conditions in order to obtain materials with optimum pozzolanic activity. Bagasse samples were burnt in an aired electric oven with a heating rate of 10 °C/min, at 350 °C for 3 h, and at different temperatures ranging from 400 to 800 °C for another 3 h. For all calcination temperatures the pozzolanic activity, structural state of silica and loss on ignition of the ashes were determined. Moreover, the SCBA with greater pozzolanicity was characterized by using chemical analysis, scanning electron microscopy, density, specific surface area and chemical reactivity.     

Effect of fineness of ash on pozzolanic properties and acid resistance of sugarcane bagasse ash replaced cement mortars

This paper addresses the potential use of Sugar Cane Bagasse Ash (SCBA) as a pozzolanic material for partial cement replacement in concrete mixtures. Cement mortars containing SCBA having five different particle size distributions at a replacement rate of 20% by weight were used to study the chemical and physical pozzolanic properties of SCBA. The durability of SCBA replaced mortars was also evaluated. SCBA with 0% retained on sieve No. 325 was used to replace 20% by weight of cement and create mortar specimens that were subjected to sulfuric acid attack of varying concentrations (1%−3% by weight of water). The tested samples were observed to check visual distortion, mass loss, and compressive strength loss at 1, 7, 14, 28, and 56 d of acidic exposure, and the results were compared to those for the control sample, that was lime water cured, at the same ages. The SCBA sets were found to meet the requirements for pozzolan class N specified by ASTM C 618. Mortars containing SCBA with 0% or 15% retention produced better compressive strength than the control mortars after 28 d. Additionally, X-ray fluorescence and X-ray diffraction analysis showed that the SCBA had favorable chemical properties for a pozzolanic material. Furthermore, SCBA replaced samples at all ages showed improved resistance against acidic attack relative to that of the control mortars. Maximum deterioration was seen for 3% concentrated solution. This study’s findings demonstrated that SCBA with an appropriate fineness could be used as a pozzolanic material, consistently with ASTM C 618.     

低品质粉煤灰在混凝土中的应用

国标将粉煤灰划分为三个等级,其中I、II级粉煤灰在混凝土中已得到广泛应用,而III级及等外灰,即低品质粉煤灰,由于其颗粒粗、含碳量大、活性低等缺点使其在混凝土中的应用受到限制。对粉煤灰的碱性、硫酸盐和氯盐改性的机理作了分析,并简要论述了目前低品质粉煤灰在混凝土中的主要应用形式:作为掺合料和细骨料等。为低品质粉煤灰在混凝土中的应用提供借鉴。     

Production of rice husk ash for use in concrete as a supplementary cementitious material

Rice husk ash (RHA), rich in silica content, can be produced from rice husk using appropriate combustion technique for use in concrete as a supplementary cementitious material. This paper discusses production process of RHA from rice husk and the quality of RHA produced using rudimentary furnace of the National University of Malaysia (UKM). Three combustion methods and two grinding methods were used to investigate physical characteristics and chemical aspects of RHA produced. Combustion temperature distribution of the furnace, ash particle size, silica crystallization phase and chemical content of the produced RHA were studied using X-ray diffraction (XRD) analysis and scanning electron microscopy (SEM). From the investigation, it was found that combustion period, chilling duration, and grinding process and duration are important in obtaining RHA of standard fineness and quality. In addition, air ducts in the furnace are very useful in order to supply air for proper burning of rice husk.     

Production of low cost self compacting concrete using bagasse ash

Self compacting concrete (SCC) is a development of conventional concrete, in which the use of vibrator for compaction is no more required. This property of self compacting concrete has made its use more attractive all over the world. But its initial higher supply cost over conventional concrete, has hindered its application to general construction. Therefore, for producing low cost SCC, it is prudent to look at the alternates to help reducing the SSC cost. This research is aimed at evaluating the usage of bagasse ash as viscosity modifying agent in SCC, and to study the relative costs of the materials used in SCC.In this research, the main variables are the proportion of bagasse ash, dosage of superplasticizer for flowability and water/binder ratio. The parameters kept constant are the amount of cement and water content.Test results substantiate the feasibility to develop low cost self compacting concrete using bagasse ash. In the fresh state of concrete, the different mixes of concrete have slump flow in the range of 333 mm to 815 mm, L-box ratio ranging from 0 to 1 and flow time ranging from 1.8 s to no flow (stucked). Out of twenty five different mixes, five mixes were found to satisfy the requirements suggested by European federation of national trade associations representing producers and applicators of specialist building products (EFNARC) guide for making self compacting concrete. The compressive strengths developed by the self compacting concrete mixes with bagasse ash at 28 days were comparable to the control concrete. Cost analysis showed that the cost of ingredients of specific self compacting concrete mix is 35.63% less than that of control concrete, both having compressive strength above 34 MPa.     

Use of palm oil fuel ash as a supplementary cementitious material for producing high-strength concrete

The objective of this study is to investigate the use of ground palm oil fuel ash with high fineness (GPA) as a pozzolanic material to produce high-strength concrete. Samples were made by replacing Type I Portland cement with various proportions of GPA. Properties such as the compressive strength, drying shrinkage, water permeability, and sulfate resistance, were then investigated. After aging for 28 days, the compressive strengths of these concrete samples were found to be in the range of 59.5–64.3 MPa. At 90-day the compressive strength of concrete containing GPA 20% was as high as 70 MPa. The drying shrinkage and water permeability were lower than those of high-strength concrete made from Type I Portland cement. When the concrete samples were immersed in a 10% MgSO₄ solution for 180 days, the sulfate resistance in terms of the expansion and loss of compressive strength was improved. The results indicated that GPA is a reactive pozzolanic material and can be used as a supplementary cementitious material for producing high-strength concrete.     

Conversion of a waste mud into a pozzolanic material

This work investigated the conversion of a waste mud from alum production into a pozzolanic material. X-ray diffraction analysis indicated that the main components in the mud were kaolinite (Al₂O₃.2SiO₂.2H₂O), quartz (SiO₂) and titanium oxide (TiO₂). After calcination at 750^oC for 5 h, kaolinite in the mud converted into metakaolinite (Al₂O₃.2SiO₂), and quartz and titanium oxide remained unchanged. The calcined mud showed very high pozzolanic reactivity. The addition of chemical activators such as Na₂SO₄ and CaCl₂ accelerated the pozzolanic reaction between lime and calcined mud and increased the strength of lime–calcined mud very significantly.     

Pozzolanic behaviour of bagasse ash

The CBRI investigations indicate that bagasse ash has to be considered as a pozzolanic material like fly ash or any other conventional pozzolana. High surface area is required to expose the grains which are coated with iron oxide and carbonaceous impurities. The authors consider that the material may be used for preparing lime ash mixture to be used locally as a mortar, especially in rural areas where availability is high.     

Bottom ash as a backfill material in reinforced soil structures

The paper describes the interface behaviour of bottom ash, obtained from two thermal power plants, and geogrid for possible utilization as a reinforced fill material in reinforced soil structures. Pullout tests were conducted on polyester geogrid embedded in compacted bottom ash samples as per ASTM D6706-01. Locally available natural sand was used as a reference material. The pullout resistance offered by geogrid embedded in bottom ash was almost identical to that in sand. In order to study the influence of placement condition of the material on pullout resistance, test were conducted on uncompacted fill materials. Pullout resistance offered by geogrids embedded in uncompacted specimen reduced by 30–60% than that at the compacted condition.     

粉煤灰在混凝土墙材制品中应用及有关问题的探讨和建议

0 前言 粉煤灰在墙材制品中的应用日益受到人们的重视,使粉煤灰新型墙材产品品种和产量有了较大的发展,如粉煤灰烧结制品、粉煤灰(普通、轻集料)混凝土小型空心砌块、多孔砖等粉煤灰水泥混凝土制品,以及可以大量利用粉煤灰的蒸压粉煤灰砖、粉煤灰加气混凝土砌块(板)和粉煤灰小型空心砌块等粉煤灰硅酸盐混凝土墙材制品.本文主要就粉煤灰在水泥混凝土墙材制品中应用及有关问题进行讨论.     

双掺活性混合材对高强混凝土性能的影响

本文对比研究了普通硅酸盐高强混凝土、粉煤灰高强混凝土以及双掺粉煤灰和沸石粉混合料的高强混凝土的力学性能,研究表明,双掺混合材的高强混凝土的早期和后期的力学性能均较好。本文同时观测了高强混凝土的内部微观结构,对活性混合材的作用机理进行了初步的探讨。     

Utilization of treated spent liquor sludge with fly ash in cement and concrete

Design mix of M-20 concrete was prepared in the laboratory by substituting cement with the treated spent liquor sludge (TSLS) and fly ash. During the study, TSLS is fixed at 7.5% by weight, and fly ash is varied as 5%, 10%, 15%, 20% and 25% to study the possibility of replacement of cement. A 15% fly ash gives the optimum compressive strength. Addition of fly ash has resulted in complete removal of toxicity as per US EPA toxicity characteristic leaching procedure (TCLP) test. A total of 7.5% sludge and 15% fly ash in M-20 concrete is expected to save Rs. 252/m³ (≈USD 5.3/m³⁾ of concrete.     

高钙粉煤灰作为混凝土掺合料的应用研究

本文系统地分析了高钙粉煤灰在混凝土中的效应和掺加高钙粉煤灰的混凝土性能特点。研究了在相同条件下掺入适量高钙粉煤灰的混凝土与普通混凝土的性能比较，并介绍了高钙粉煤灰在混凝土中的应用试验实例及有待解决的问题。     

Filler effect and pozzolanic reaction of ground palm oil fuel ash

This research examines the compressive strength of mortar and how the filler effect and pozzolanic reaction of ground palm oil fuel ash (POFA) contribute to this strength. POFA and river sand were ground to three different particle sizes and used to replace Type I Portland cement at 10–40% by weight of binder to cast the mortar. The compressive strengths of ground POFA and ground river sand mortars were determined at various ages between 7 and 90 days. The results showed that the compressive strength of mortar due to the filler effect of ground river sand was nearly constant during the 7–90 day period for a specified replacement rate of cement. However, the compressive strength of mortar due to the filler effect tended to increase slightly with increased cement replacement. The pozzolanic reaction of ground POFA increased with increasing particle fineness of ground POFA, replacement rate of cement, and age of the mortar. The compressive strength contribution from the pozzolanic reaction of ground POFA was much more pronounced than the contribution from the filler effect when the smallest sizes of both materials were considered.     

Utilization of alkali-activated copper slag as binder in concrete

This study was focused on developing concrete using alkali-activated copper slag (AACS) as a binder. The properties of alkali-activated copper slag concrete (AACSC) were compared with portland cement concrete (PCC). Different AACSC mixes were prepared with varying Na₂O dosage (6% and 8% of the binder by weight) and curing methods. Hydration products in AACSC were retrieved using Fourier-transform infrared spectroscopy (FTIR) and X-ray powder diffraction (XRD) techniques. The test results indicate that the workability of AACSC was lesser than that of PCC. The AACSC mix with 6% Na₂O dosage has exhibited similar mechanical properties as that of PCC. The mechanical properties of AACSC were higher than PCC when 8% of Na₂O dosage was used. Heat curing was effective to upgrade the strength properties of AACSC at an early age of curing, but at a later age mechanical properties of ambient cured and heat-cured AACSC were comparable. The hydration products of AACSC were not identified in XRD patterns, whereas, in FTIR spectra of AACSC some alkali-activated reaction products were reflected. The AACSC mixes were found to be more sustainable than PCC. It has been concluded that AACSC can be produced similarly to that of PCC and ambient curing is sufficient.     

粉煤灰作沥青混凝土粉料的研究

为扩大粉煤灰利用途径,降低成本、对粉煤灰代替石粉配制沥青混凝土进行了研究,工程应用取得良了效果。用粉煤灰拌制的沥青混凝土性能优于普通沥青混凝土,完全满足现行沥青混凝土标准要求;粉煤灰沥青混凝土稳性良好的原因是其表面存在或吸附了一层碳膜,改善了其与沥青的亲和力。     

浅谈粉煤灰的综合利用

对粉煤灰的资源化利用方式作了综述;对其在其它方面的应用,例如环境治理等方面做了简单的介绍。     

粉煤灰在混凝土中的应用

本文从粉煤灰本身的品质、水泥中的混合材、与化学外加剂的适应性、与矿物掺合料的适应性这四个方面讨论了粉煤灰应用于混凝土中的影响因素。     

Hydraulic-lime based concrete: Strength development using a pozzolanic addition and different curing conditions

Concrete is a major worldwide building material, in which Portland cement is the usual binder. Taking into account environmental factors in cement production, especially concerning CO₂ emissions and energy consumption, this work aims at the development of concrete with a hydraulic-lime binder; in order to increase mechanical strength, pozzolanic materials were added. In this preliminary study, compositions with different percentages of hydraulic lime were tested and a pozzolanic material, a residue from expanded clay production, was used. Variations in percentage of pozzolan and conditioning were carried out. Concrete specimens were tested for mechanical strength at various ages and a pozzolanic index was determined in order to evaluate the influence of the pozzolanic material on attained mechanical strength. This paper presents the results of this testing campaign, concluding on the influence of pozzolanic additions and curing conditions on the strength development of this material.     

粉煤灰在混凝土中的应用

简要阐述了粉煤灰在混凝土中的作用机理，分析了粉煤灰掺入可降低混凝土水化热的原因，阐明了粉煤灰对大体积混凝土所起的作用，从而推广粉煤灰的应用。