Production of high strength concrete by use of industrial by-products

Blast furnace slag aggregates (BFSA) were used to produce high-strength concretes (HSC). These concretes were made with total cementitious material content of 460–610 kg/m³. Different water/cement ratios (0.30, 0.35, 0.40, 0.45 and 0.50) were used to carry out 7- and 28-day compressive strength and other properties. Silica fume and a superplasticizer were used to improve BFSA concretes. Slump was kept constant throughout this study. Ten percent silica fume was added as a replacement for ordinary portland cement (OPC) in order to obtain HSC. The silica fume was used as highly effective micro-filler and pozzolanic admixture. Superplasticizer at dosages of 2%, 1.5%, 1%, 0.5% and 0% by OPC weight for 0.30, 0.35, 0.40, 0.45 and 0.50 w/c ratios, respectively, were adopted. Results showed that compressive strength of BFSA concretes were approximately 60–80% higher than traditional (control) concretes for different w/c ratios. These concretes also had low absorption and high splitting tensile strength values. It is concluded that BFSA, in combination with other supplementary cementitious materials, can be utilized in making high strength concretes.     

Studies on termite hill and lime as partial replacement for cement in plastering

This study investigated the compressive strength and water absorption capacity of 50×50×50 mm mortar cubes made from mixes containing lime, termite hill and cement and sand. Two mix ratios (1:4 and 1:6) and varying binder replacements of cement with lime or termite hill amounting to 0%, 10%, 20%, 30%, 40% and 50% were used. Test results showed that the compressive strength of the mortar cubes increases with age and decreases with increasing percentage replacement of cement with lime and termite hill. However, for mix ratio 1:6, up to 20% replacement of cement with either lime or termite hill, all the mortar cubes had the same strength; subsequently, the termite hill exhibited a higher compressive strength. For mix ratio 1:4, mortar cubes made from lime/cement and termite hill/cement mixtures had the same strength at 50% replacement. Generally, water absorption is higher in mixtures containing lime (18.10% and 14.20% for mix ratios 1:6 and 1:4, respectively, both at 50% replacement level) than those containing termite hill (16.10% and 13.02% for mix ratios 1:6 and 1:4, respectively, both at 50% replacement level). Termite hills seem to be promising as a suitable, locally available housing material for plastering.     

Development of a cementless mortar using hwangtoh binder

This paper presents the properties of a cementless mortar developed to produce eco-friendly building material without carbon dioxide emissions and with various beneficial effects. The binder, hwangtoh binder (HB), used in this mortar was developed by reaction of a very small amount of inorganic minerals and activated hwangtoh, which is rich in silica, SiO₂, and alumina, Al₂O₃. To investigate the compressive strength and shrinkage deformation of the cementless mortar using HB, HB mortar, water–HB ratio, fine aggregate–HB ratio, and the maximum size and grading of fine aggregate were selected as the main variables of test specimens classified into three groups. The test results presenting the effect of various parameters on the properties of HB mortar confirmed that the developed HB has a highly effective performance as a binder. The equations using nonlinear multiple regression analysis based on the test results are represented to assess the flow and 28-day compressive strength of HB mortar. Comparisons between predicted and measured flow and 28-day compressive strength show good agreement.     

石粉在建筑砂浆中的应用

对石粉在砂浆中的作用进行了分析；从砌筑砂浆、抹灰砂浆、屋面找平层三方面进行了论述；提出了石粉代替部分砂的新方法；进行了砂浆强度、和易性、粘结力的研究；提高了砌筑砂浆的强度，改善了砂浆和易性、粘结力。解决了砌体组合强度低、砂浆离析和分层现象及屋面找平层空鼓裂缝的问题。     

高吸附性机制砂石粉对防水砂浆性能的影响研究

为了明确高吸附性机制砂石粉在防水砂浆中应用的技术可行性,采用片麻岩机制砂及其石粉制备防水砂浆,研究了石粉部分替代粉煤灰后,对其和易性、强度、体积稳定性的影响。结果表明:片麻岩机制砂石粉部分替代粉煤灰可降低防水砂浆2 h稠度损失率并提高保水性,对防水砂浆的抗压强度影响不大,在一定程度上可降低防水砂浆的收缩和开裂敏感性。     

磁化水对水泥拌合物性能的影响

本文主要研究了磁化水对水泥砂浆和净浆性能的影响。磁化水由自来水通过自主研制的MW-Ⅰ型磁水器而获得。试验中研究的磁化参数包括磁化器的磁场强度、水流通过磁场中心的流速、磁场有效长度、水流循环次数和养护时间。结果显示,采用磁化水拌制的水泥净浆流动度、胶砂试件强度和空白试样相比有很大的提高，当磁场强度达到810mT,水流速达到0.73m/s时,性能提高最为明显,水泥初凝时间可以提前30min～50min,砂浆抗压强度早期可提高20%～30%,28d强度增进率有所下降。     

Enhancement of mechanical and hydrophobic properties of Adobes for Building Industry by the addition of polymeric agents

Availability, cheapness and thermal insulation properties give adobe an advantage over other building materials in dry regions. On the contrary, its poor compressive strength and high water adsorption are important disadvantages. We report the enhancement on compressive strength and water absorption resistance obtained in this material by the addition of dodecylamine and emulsified asphalt to the clay used for its manufacture. We characterized the adobes by X-ray diffraction, infrared spectrometry, ζ-potential measurements and scanning electronic microscopy. Ultra violet accelerated test, compressive strength test and water absorption tests were also carried out. The results show that adobes with cationic amine and emulsified asphalt improve their compressive strength and lower their water absorption at the time that they preserve their properties under weathering conditions.     

一种新型自流平砂浆的研究

选择适宜凝结时间和强度的水泥,并通过试验选择合适的外加剂,进而又引入了硅灰和石膏等掺合料,调配出了一种新型自流平砂浆。试验证明,此种自流平砂浆流动度大,经时损失小,收缩率低,表面光洁,耐磨性能优良,1d抗压强度可达50、60MPa、抗折强度7.20MPa,28d压强度可达87．10MPa、抗折强度11．30MPa。     

再生细骨料的不同取代率对砂浆性能的影响

再生细骨料是硬化的水泥砂浆颗粒和水泥颗粒组成。本文用废旧混凝土破碎产生的再生细骨料部分或全部代替天然细骨料来配制砂浆,通过采用固定配合比和调整减水剂、用水量两种方法,研究了再生细骨料取代率对砂浆性能的影响。     

分类再生细骨料对建筑砂浆性能影响的试验研究

将不同来源的废弃混凝土破碎筛分后,按照《混凝土和砂浆用再生细骨料》分为I、II、III类,依据《建筑砂浆基本性能试验方法标准》对这三类再生细骨料设计五种不同取代率的水泥砂浆标准试块,测定其和易性和抗压强度,并对取代率为100%的再生砂浆界面结合区的微观形貌进行观察。试验结果表明:I、II、III类再生细骨料所配制的砂浆和易性和强度依次降低;控制稠度在60~90 mm时,随取代率的增大,用水量增大,保水性降低,强度降低;通过SEM观察,II类再生细骨料与水泥石黏结较好,强度也较高。建议I类再生细骨料取代率不宜超过50%,II、III类再生细骨料不宜超过30%。     

再生EPS颗粒对砖粉泡沫混凝土性能影响的研究

再生EPS颗粒表面粗糙,且多粒径具有一定的级配,将其加入到废弃微粉新体系泡沫混凝土中,可改善其性能,拓宽其利用渠道。研究了再生EPS颗粒对砖粉泡沫混凝土各项性能的影响。试验结果表明,EPS的掺入使其干密度线性降低,掺量在4%~6%之间时,抗压强度下降缓慢,含水率大幅度下降,抗碳化能力增强,抗冻融能力满足规范要求,导热系数减小。与通过增加泡沫用量获得的同密度等级的砖粉泡沫混凝土相比,掺有再生EPS颗粒的混凝土抗压强度提高,含水率和吸水率降低,性能较为优越。     

聚合物改性高强水泥修补砂浆的试验研究

阐述了聚合物改性水泥砂浆的原理,介绍了聚合物改性高强水泥修补砂浆的试验研究成果并展望了聚合物改性水泥修补砂浆的应用前景。     

Characterisation of the behaviour of high performance mortar subjected to high temperatures

An experimental investigation was conducted to evaluate the performance of mortar mixed with silica fume (SF) when exposed to high temperatures. A three-point bending test apparatus was developed to test concrete-like materials at high temperatures. Notched specimens were first heated at a rate of 3.3 °C/min to various target temperatures from room temperature to 900 °C and then maintained under constant temperature during 2 h. They were then subjected to a three-point bending test while the temperature was held constant. The maximum peak load occurred at 300 °C and decreased sharply at higher temperatures. The experimental results demonstrated a noticeable influence of the temperature on the fracture resistance of the high-performance mortar. The toughness parameters, such as intensity factor or fracture energy, evolved nonlinearly with the target temperature, and reached their maximum value at 300 °C; at higher temperature, their values decreased considerably. SEM micrographs of the heated specimens after the mechanical tests and cooling and TGA/DTA analysis of the dried material matrix facilitated the understanding of the material’s macroscopic behaviour.     

废旧胶粉改性水泥砂浆制备及其物理力学性能研究

将2种不同粒径、碱活化的废旧硫化橡胶粉(WTR),以3种不同掺量等体积取代细骨料,制成废旧胶粉改性水泥砂浆(WTRCM),研究WTRCM耐水抗渗、抗压及阻尼减振性能。结果表明,WTRCM的单面吸水率、力学强度随WTR掺量的增加均逐渐降低,60目和80目WTR体积掺量为20%的WTRCM单面吸水量、抗压强度分别降低了60%、69%和62%、60%,表明憎水且柔性WTR掺入能提升砂浆抗渗耐水能力,但会降低其抗压强度,且掺加粒度细的WTR更为有利。WTRCM的损耗因子随WTR掺量增加而逐渐增大,60目和80目WTR体积掺量为30%的WTRCM阻尼减振效果可提高分别达30%、36%,表明具有柔韧性的WTR掺入有利于快速衰减掉WTRCM所受的振动能量,且掺加粒度细的WTR更为有效。     

模糊综合评判高性能耐磨砂浆

目前国内学者在研究耐磨砂浆时,普遍采用单一因素评价.虽然这种方法可以评定砂浆某一方面的性能,但研究结论往往带有片面性.为此,采用模糊综合评判方法对高强耐磨砂浆进行分析,为客观评价耐磨砂浆综合性能提供一种方法.     

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.     

Microstructure of pre-wetted aggregate on lightweight concrete

A study was made on microstructure and water absorption rate of ‘Litcon’—a porous lightweight aggregate made from expanded clay. EDAX analysis on the aggregate particle showed different chemical compositions between the shell and the inner core of the lightweight aggregate. S.E.M. examination on the resulting concrete showed a good mechanical bonding between the cement and the aggregate interface, though traces of inter-granular cracks were observed. When the pre-wetting time of the aggregate increased, the strength and the workability of the concrete increased too. The high workability of fresh concrete was attributed to the localised high water content at the surface of the pre-wetted aggregate. The surface pores of the aggregate shell absorbed the water built-up at the cement/aggregate transition phase thus resulting with lower water content at the transition zone. EDAX analysis confirmed migration of cement phase into the aggregate shell. This loss of fluidity at the transition zone may have a significant effect on the permeability of lightweight concrete.     

利用原状干排粉煤灰配制高强混凝土试验研究

利用新海电厂原状干排粉煤灰及其它常规原材料,研制出坍落 度达190－260,28d抗压强度达50－75MPa,抗渗等级超过P20的高强粉煤灰混凝土。讨论了粉煤灰掺量、胶材总量、砂率、水胶比、减水剂品种与掺量等参数对混凝土强度和流动性的影响,还讨论了粉煤灰掺量对混凝土抗渗性能的影响。     

大掺量粉煤灰对砂浆强度的影响

试验研究了水胶比,粉煤灰掺量,粉煤灰种类和龄期等因素对砂浆强度的影？分析了砂浆强度与粉煤灰掺量之间的相互关系,以确定最佳水胶比和粉煤灰掺量.