Corrosion performance of rice husk ash blended concrete

Rice husk ash is one of the promising pozzolanic materials that can be blended with Portland cement for the production of durable concrete and at the same time it is a value added product. Addition of rice husk ash to Portland cement not only improves the early strength of concrete, but also forms a calcium silicate hydrate (CSH) gel around the cement particles which is highly dense and less porous. This may increase the strength of concrete against cracking. So far a systematic and detailed investigations on the corrosion performance of rice husk ash blended concrete is very scarce. Therefore, in the present investigation, a realistic approach has been made using different techniques such as compressive strength, bond strength, split tensile strength etc. Corrosion performance was evaluated using, open circuit potential measurements, rapid chloride ion permeation test and impressed voltage test and the results were discussed.     

Strength and water permeability of concrete containing palm oil fuel ash and rice husk–bark ash

In this paper, palm oil fuel ash and rice husk–bark ash, which are by-products from electricity generating power plants and disposed as wastes in landfills, were used as a partial cement replacement. They were ground and incorporated into concrete at the levels of 20%, 40% and 55% by weight of binder. Compressive strength and water permeability of concretes containing ground palm oil fuel ash (GPOA) and ground rice husk–bark ash (GRBA) were investigated. From the tests, the replacement of Portland cement by both materials resulted in the higher water demand in concrete mixtures as compared to ordinary Portland cement (OPC) concrete with compatible workability. The compressive strengths of concretes containing 20% of GPOA and GRBA were as high as that of OPC concrete and were reduced as the increase in the replacement ratios. Although the compressive strengths of concrete with the replacement of GPOA or GRBA up to 40% were lower than OPC concrete, their water permeabilities were still lower than that of OPC concrete. These results indicate that both of GPOA and GRBA can be applied as new pozzolanic materials to concrete with an acceptable strength as well as permeability.     

Effect of rice husk ash on the strength and durability characteristics of concrete

This work investigates the effects of adding residual rice husk ash (RHA) from South Vietnam, generated when burning rice husk pellets in the boiler, to cement. To improve pozzolanic reactivity, RHA was ground for 1 h. The non-ground RHA and ground RHA were used to test strength activity index according to ASTM C311. The properties of the concrete were investigated, including compressive strength, concrete electrical resistivity, and ultrasonic pulse velocity. Results show that the non-ground RHA can be applied as a pozzolanic material. Decreasing the non-ground RHA average particle size provides a positive effect on the compressive strength of mortar. Compressive strength of cylindrical concrete in the 47–66 MPa range was obtained in this study. The results also indicate that up to 20% of ground RHA could be advantageously blended with cement without adversely affecting the strength and durability properties of concrete.     

A study of the workability and compressive strength characteristics of corn cob ash blended cement concrete

The study investigated the workability and compressive strength characteristics of corn cob ash (CCA) blended cement concrete. Nine classes of CCA-blended cements were employed with the CCA content ranging from 0% to 25%. The 0% CCA replacement involved the use of normal ordinary Portland cement and it served as the control. The mix proportions of cement:sand:granite used were 1:1½:3, 1:2:4 and 1:3:6 with 0.5, 0.6 and 0.7 water-to-cement ratios, respectively. The concrete cubes were tested at the curing ages of 3, 7, 28, 60, 120, and 180 days. Slump and compacting factor tests were carried out to check the effect of CCA on the workability of concrete. The results showed that the concrete slump and compacting factor decreased as the CCA content increased indicating that concrete becomes less workable (stiff) as the CCA percentage increases. The compressive strength of CCA-blended cement concrete was lower than the control at early ages, but improves significantly, and outperforms the control at later ages (120 days and above). The optimum compressive strength of 57.10 N/mm², 40.30 N/mm² and 28.07 N/mm² for 1:11/2:3, 1:2:4 and 1:3:6 mix proportions, respectively at 180 days were obtained at 8% CCA replacement level. It was concluded that only up to 8% CCA substitution is adequate where the blended cement is to be used for structural concrete.     

Sulfate resistance of blended cements containing fly ash and rice husk ash

In this paper, the sulfate resistance of mortars made from ordinary Portland cement containing available pozzolans viz., fly ash and ground rice husk ash (RHA) was studied. Class F lignite fly ash and RHA were used at replacement dosages of 20 and 40% by weight of cement. Expansion of mortar prisms immersed in 5% sodium sulfate solution and the change in the pH values of the solution were monitored. The incorporation of fly ash and RHA reduced the expansion of the mortar bars and the pH values of the solutions. RHA was found to be more effective than fly ash. Examination of the fractured surface of mortar prisms, after a period of immersion, by scanning electron microscopy confirmed that sulfate attack of blended cement mortars was restricted owing to the reductions in calcium hydroxide and C/S ratio of the C–S–H gel in the blended cement mortar. In comparison to Portland cement mortar, less calcium sulfate and much less ettringite formations were found in the mortars made from blended cement containing RHA. The amounts of calcium sulfate and ettringite found in the blended cement mortar containing fly ash were also small but were slightly more than those of RHA mortar. Up to 40% of Portland cement could be replaced with these pozzolans in making blended cement with good sulfate resistance.     

粉煤灰、矿粉掺合料对低强度等级混凝土的强度及和易性的影响

粉煤灰和矿粉是低强度等级混凝土中最主要的掺合料、在未加掺合料的C30混凝土基础上,将粉煤灰、矿粉在混凝土中单掺或双掺,并以若干组不同掺量的粉煤灰、矿粉对混凝土不同龄期的强度和和易性变化进行研究。试验结果表明:粉煤灰对提高预拌混凝土的和易性效果极好,但混凝土的早期、中期强度发展缓慢,矿粉相对粉煤灰对混凝土各龄期强度发展较快,但和易性差于粉煤灰,二者双掺混凝土后各龄期强度及拌合物和易性均较好,最佳比例为水泥质量的30%~40%。     

Influence of bacteria on the compressive strength, water absorption and rapid chloride permeability of fly ash concrete

This paper presents the results of an experimental investigation carried out to evaluate the influence of Sporoscarcina pasteurii bacteria on the compressive strength and rapid chloride permeability of concrete made without and with fly ash. Cement was replaced with three percentages (10, 20 and 30) with fly ash by weight. Three different cell concentration (0, 10³,10⁵,10⁷ cells/ml) of bacteria were used in making the concrete mixes. Tests were performed for compressive strength, water absorption and rapid chloride permeability at the age of 28 days. Test results indicated that inclusion of S. pasteurii in fly ash concrete enhanced the compressive strength, reduced the porosity and permeability of fly ash concrete. Maximum increase (22%) in compressive strength and four-times reduction in water absorption was observed with 10⁵ cells/ml of bacteria. This improvement in compressive strength was due to deposition on the bacteria cell surfaces within the pores.Calcite deposition in concrete observed nearly eight times reduction in chloride permeability of fly ash concrete. The present work highlights the influence of bacteria on the properties of concrete made with supplementing cementing material such as like fly ash. Usage of bacteria like S. pasteurii improves strength and durability and strength of fly ash concrete through self-healing effect.     

水泥粒径分布对混凝土抗压强度影响的试验研究

为了考察水泥粒径分布对混凝土抗压强度的影响,开展了试验研究。首先,将普通硅酸盐水泥经气流粉碎机生产获得化学组分相同、粒径分布不同的超细水泥,然后通过掺加超细水泥改变水泥粒径分布。分别测定了3种不同超细水泥掺量下的水泥等温放热曲线和混凝土抗压强度。试验结果表明:①掺加适量超细水泥能够优化水泥粒径分布,提高水泥利用率,增加混凝土抗压强度;②混凝土抗压强度并不一定随超细水泥掺量的增加而递增,存在一个最佳的超细水泥掺量,使水泥粒径分布最优,从而获得最高的混凝土抗压强度。     

再生骨料和稻壳灰对混凝土力学性能影响研究

在稻壳灰等量取代水泥的掺量为20%定量的情况下,通过再生粗骨料不同比值等量取代天然骨料为15%,20%,25%,试配制4组混凝土试块,研究了再生骨料和稻壳灰复掺对混凝土力学性能的影响,提出了最佳取代量为稻壳灰20%、再生粗骨料为25%。同时,在现行普通混凝土配合比设计规程的基础上,给出了带修正系数0. 467的复掺混凝土配制强度公式。     

稻壳/稻壳灰在墙体材料领域中的应用研究

介绍了稻壳/稻壳灰主要组成和特性。总结了稻壳在建筑墙体材料中的主要利用途径及相关研究进展,展示了稻壳的广阔利用前景。     

利用稻壳灰配制不同灰度混凝土性能研究

采用整体着色方法,在普通混凝土中加入适量的稻壳灰,可将原本灰白色的混凝土变成不同层次的灰色混凝土,以减少大量的二次装修.随着稻壳灰掺量的增加,混凝土灰色不断加深,同时,新拌混凝土的流动性略有降低,黏聚性变得越来越好,不泌水;在混凝土中加入适量的稻壳灰,可以提高硬化混凝土的抗压强度,增强混凝土的抗冻性能和抗渗性能.     

ASF高效减水剂对混凝土工作性能和强度的影响

通过大量对比试验 ,分析得出氨基磺酸盐高效减水剂在改善混凝土工作性能保坍性 ,提高有效减水率和强度等方面的优越性 ,指出其具有广阔的应用前景     

The study of using rice husk ash to produce ultra high performance concrete

The limited available resource and the high cost of silica fume (SF) in producing ultra high performance concrete (UHPC) give the motivation for searching for the substitution by other materials with similar functions, especially in developing countries. Rice husk ash (RHA), an agricultural waste, is classified as “a highly active pozzolan” because it possesses a very high amount of amorphous SiO₂ and a large surface area. The possibility of using RHA to produce UHPC was investigated in this study. The result shows that the compressive strength of UHPC incorporating RHA, with the mean size between 3.6 μm and 9 μm, can be achieved in excess of 150 MPa with normal curing regime. The interesting point is that the effect of RHA on the development of compressive strength of UHPC is larger than that of SF. Besides, the sample incorporating the ternary blend of cement with 10% RHA and 10% SF showed better compressive strength than that of the control sample without RHA or SF. This blend proved to be the optimum combination for achieving maximum synergic effect.     

磨细稻壳和再生骨料对混凝土抗压强度影响研究

通过磨细稻壳按5%,10%,15%的掺量等量取代水泥,再生骨料按0%,30%掺量等量取代天然碎石的组合方式,研究了磨细稻壳和再生骨料对混凝土抗压强度影响。经测试7组磨细稻壳和再生骨料复掺混凝土试块的抗压强度对比分析,随着磨细稻壳掺量的增加,混凝土初凝时间相应延长,而抗压强度相应降低。在现行普通混凝土配合比设计规程的基础上,给出了带修正系数的复掺混凝土配制强度公式,同时,提出了磨细稻壳、再生骨料的最佳取代量。     

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.     

Genetic programming approach for prediction of compressive strength of concretes containing rice husk ash

Soft computing techniques have recently been widely used to model some of human activities in many areas of civil engineering applications. In this paper, two models in gene expression programming (GEP) approach for predicting compressive strength of concretes containing rice husk ash have been developed at the age of 1, 3, 7, 14, 28, 56 and 90 days. For purpose of building the models, experimental results for 188 specimens produced with 41 different mixture proportions are obtained from the literature. According to these experimental results, the models are arranged by using seven different input variables in GEP approach. In according to these input variables, the compressive strength values from mechanical properties of concretes containing rice husk ash are predicted in GEP approach models. The results of training, testing and validation sets of the models are compared with experimental results. All of the results showed that GEP is a strong technique for the prediction of compressive strength values of concretes containing rice husk ash.     

矿渣粉对混凝土和易性及强度影响的研究

试验研究和分析了矿渣粉掺量对低水胶比混凝土的和易性及强度的影响。结果表明,除了减水剂掺量对新拌混凝土和易性有显著影响外,矿渣粉掺量对混凝土拌合物的和易性有明显改善。水胶比是影响混凝土强度的主要因素,而矿渣粉掺量对混凝土强度的影响也较为明显。矿渣粉的细度小于水泥的细度,可作为细集料用于混凝土中,以改善混凝土拌合物的和易性,降低施工成本。     

浅议混凝土间歇时间对和易性及抗压强度的影响

混凝土从搅拌站生产出来后,需经过一段间歇时间(运输时间、等候时间、浇筑时间)后,才能浇筑到工程结构部位。如果是浇筑墙体,间歇时间可能会达到4～5 h,间歇时间的延长可能会影响混凝土的使用性能。通过对不同强度等级混凝土试验,研究间歇时间对混凝土工作性及抗压强度的影响。结果表明在使用聚羧酸外加剂时,为保证混凝土拌合物的工作性,外加剂的二次加入量随着间歇时间的延长而增加,混凝土强度等级提高,外加剂的二次加入量随之增大;成型时间在4～5 h以内时,各强度等级混凝土的抗压强度无明显下降;混凝土加水调整前,各时间段成型的混凝土抗压强度变化不明显,加水调整后,混凝土各龄期抗压强度明显下降。     

混凝土强度、粉煤灰掺量和水胶比关系探究与应用

粉煤灰作为混凝土中最常用的矿物掺合料,其优点得到业界的广泛认可。对于混凝土强度-粉煤灰掺量-水胶比三者之间的关系,国内外专家学者对粉煤灰进行了深入的研究。通过大量的试验数据,探讨混凝土强度-粉煤灰掺量-水胶比三者之间的关系,并通过工程应用,为粉煤灰的使用提供一点借鉴。     

高效减水剂与粉煤灰对再生混凝土的和易性影响研究

通过对3种不同的再生混凝土和易性影响研究,发现随着再生骨料取代率的不断增大,再生混凝土的流动性均降低,降低幅度的顺序为再生混凝土③>再生混凝土①>再生混凝土②;掺粉煤灰后再生混凝土拌合物的坍落度有所增加,但增加幅度并不大;正交试验显示,影响坍落度的4因素主次顺序为:再生骨料①取代率、高效减水剂、再生骨料②取代率、粉煤灰掺量,再生混凝土中加入高效减水剂和粉煤灰,可显著提高新拌再生混凝土的流动性,且粘聚性和保水性也较好。