Strength and permeability of steel fibre reinforced grouts

The feasibility of using steel fibres to improve the tensile strength and durability of cement–sand grout was investigated. Initial tests focused on achieving pumpable grout mixes and 13 mm round steel fibres with a diameter of 0.16 mm were found to be compatible with a conventional grout paddle mixer and piston pump. Subsequently, grouts with 0.5% and 1% fibre volume fraction were subjected to compressive and splitting tensile strength tests, coefficient of permeability tests and wet–dry cycles. The effect of partial cement replacement with silica fume and blast furnace slag was also investigated. It was found that steel fibres were beneficial for short- and long-term tensile strength. Coefficient of permeability was not adversely affected by addition of fibres. Resistance to microcracking and increase in permeability after wet–dry cycles was also improved by steel fibres. Partial replacement of cement with blast furnace slag resulted in enhanced mechanical properties, whereas the results for silica fume were mixed.     

Basic rheological and mechanical properties of high-volume fly ash grouts

Soil, rock and oil-well grouting require enormous amounts of cement and are therefore good examples of areas where high volumes of fly ash could replace cement partially to produce low-cost, environmentally friendly and durable grouts. This paper presents the results of the particle size distribution, three rheological properties (flow time, bleeding and setting time), and five mechanical and strain properties (compressive strength, shear bond strength, modulus of elasticity, Poisson's ratio and drying shrinkage) of high-volume fly-ash (HVFA) grouts (cement replacement by fly ash of over 55% by weight), with and without superplasticizer (SP) and/or anti-washout agent (AWA). Rheological properties are reported for eight water–cementitious materials (cement+fly ash) ratios (W/CM), ranging from 0.4 to 1.3, whereas mechanical and strain properties of hardened grouts are given at W/CM of 0.5, 0.55 and 0.65. The effects of SP and AWA on the flow time of low-W/CM grouts and the stability of high-W/CM grouts were investigated. The results indicate that the addition of fly ash in cement grouts reduces the flow time, improves stability, reduces drying shrinkage, and attains similar compressive and shear bond strengths as pure cement grouts at later ages. Moreover, when SP is used for low-W/CM grouts, the latter destabilizes, and in those cases AWA should be used.     

钢渣微粉对高强混凝土性能的影响

试验对比研究了钢渣微粉对混凝土工作性、抗压强度、体积稳定性以及耐久性的影响.结果表明,钢渣微粉可以显著改善混凝土的工作性,但也导致了混凝土凝结时间的延长.相对于粉煤灰和矿粉,钢渣微粉的活性略低,配制出的混凝土早期强度略低,但钢渣微粉可以与粉煤灰或矿粉双掺而产生超叠加效应.且钢渣微粉可以显著降低混凝土的于燥收缩,提高混凝土的抗氯离子渗透性能,对混凝土的抗冻性也无不利的影响.     

Compressive strength and shrinkage of mortar containing various amounts of mineral additions

Three mineral additions largely used in cementitious materials were tested in order to follow the shrinkage behaviour for 1 year of observation when they substitute a part of cement. The tests were carried out on standardized mortars specimen where cement was replaced by 5%, 15% and 25% of limestone, 10%, 20%, 30% of natural pozzolan and 10%, 30% and 50% of slag. The substitution of cement by 10%, 20% and 30% of limestone powder, natural pozzolan and slag respectively involves an optimal improvement of compressive strength of mortar. The separate quantification of the autogeneous and drying shrinkage development shows the effective contribution of each addition on microstructure modification and of the additional hydrates production. The microstructure was improved in the presence of limestone and of a moderate rate of slag, whereas it remains normal with natural pozzolan. The replacement rate of an active addition lower than 10% led to an additional hydrates production. This overproduction which accompanies the autogeneous shrinkage is more pronounced when cement is largely replaced by limestone. The evolutions of strength and shrinkage of mortars follow the same tendency from where it is easier to find a linear relationship giving the shrinkage deformation according to the compressive strength.     

Performance of high wokability slag-cement mortar for ferrocement

The performance of high workability mortar mix, applicable for the casting of thin ferrocement elements by using slag as cement replacement and superplasticizer as water reducing agent is investigated. Cement mortars (1:2. 1:2.5 and 1:3) incorporating various percentages of slag and superplasticizer were designed to have high workability (136±3% flow). Performance of the mortars is studied in terms of compressive strength, unit weight, strength development and water absorption. Effect of three different curing regimes on strength and strength development of the mortars is also the part of this study. The results showed that the high workability slag cement mortars of reasonably high strength, low water absorption and exhibiting early age strength comparable to that of the OPC mortars can be designed in order to cast thin ferrocement elements by the method of pouring.     

低温条件下硅酸盐水泥基钢筋连接用套筒灌浆料试验研究

通过研究环境温度、拌和水温度、预养护时间及外加剂对套筒灌浆料工作性和力学性能的影响,探索了常温套筒灌浆料在低温环境下性能变化的趋势,为利用硅酸盐水泥制备低温套筒灌浆料提供试验基础。试验结果表明:常温套筒灌浆料不适宜用于低于5℃的温度环境;低温时,升高拌和水温度有助于提高灌浆料的早期强度,但处于负温时,灌浆料强度发展缓慢;预养护有助于提高低温时套筒灌浆料的早期强度;适量掺加防冻剂和早强剂可以提高套筒灌浆料早期强度,流动度随其掺量的增加而逐渐下降。综合考虑,4种外加剂中亚硝酸钠效果最好,其合理掺量为2.0%,碳酸锂效果最差。对于硅酸盐水泥基套筒灌浆料,在负温时难以通过单掺外加剂来获得较高的早期强度。     

不同钢渣掺量对UHPC性能的影响研究

钢渣作为大宗固体废弃物在建筑材料领域的应用是节能减排的重要途经之一。本文研究了不同钢渣掺量对UHPC工作性、力学性能及收缩性能的影响规律,并通过TG/DTG及SEM分析其水化机理。结果表明,随着钢渣掺量的增加,UHPC的流动度呈不同程度增加,早期抗压强度和抗折强度降低幅度较大,但后期力学性能差距逐渐减小。UHPC的自收缩性能随着钢渣掺量的增加呈降低趋势。钢渣粉掺量占总胶凝材料的18%时,制备的UHPC的工作性能和自收缩性能仍较为优异,水化28d后力学性能增长较快。     

不同水泥基的低负温套筒灌浆料性能研究

通过测试2种不同水泥基低负温套筒灌浆料和1种常温套筒灌浆料在不同温度环境及养护方式下的流动度和抗压强度,对比研究了三者在低负温环境下的性能差异。结果表明,常温套筒灌浆料在低负温下极易被冻害,强度无法有效增长;掺激发剂的硅酸盐水泥基低负温套筒灌浆料可长期在低负温环境下养护,有良好的低温流动性,-5℃养护28 d抗压强度大于85 MPa;硫铝酸盐水泥基低负温套筒灌浆料只可在低负温环境下短期养护,再转标准养护后强度也能继续增长,-5℃养护7 d+标养28 d抗压强度可达85 MPa以上。     

利用磨细钢渣矿粉配制C60高性能混凝土的研究

本文将经过闷渣和超细粉磨处理的钢渣矿粉用于配制C60强度等级高性能混凝土,研究了掺磨细钢渣矿粉混凝土的新拌工作性能、抗压强度、收缩性能以及抗氧离子渗透、抗冻性、抗钢筋锈蚀等耐久性能。研究结果表明,适量磨细钢渣掺入混凝土中可以提高混凝土的工作性能、抗压强度以及耐久性能;将磨细钢渣与优质粉煤灰复掺可以发挥超叠加效应,进一步改善混凝土性能;另外,掺入磨细钢渣矿粉可以降低混凝土的早期收缩。     

碱激发矿渣-锂渣混凝土试验研究

用锂渣部分代替矿渣制备碱激发矿渣-锂渣混凝土,结果表明,当溶渣比(质量比)为0.5,0.6,胶凝材料用量为390 kg/m3时,碱激发矿渣-锂渣混凝土的28 d抗压强度大于70 MPa,且早期抗压强度高,3 d就都达到28 d的70%左右.同时,研究了碱激发矿渣-锂渣混凝土的工作性和氯离子渗透性.结果表明,该混凝土的工作性良好,抗氯离子渗透性高.     

钢渣代砂建筑砂浆的性能研究

研究了宝钢转炉滚筒渣、电炉渣代砂建筑砂浆的和易性、强度、凝结时间和收缩等性能.结果表明,用2种钢渣代砂配制的建筑砂浆,其和易性、强度和收缩性能较普通砂浆均有明显改善,凝结时间能达到要求,且电炉渣优于滚筒渣.     

Cement–clay grouts modified with acrylic resin or methyl methacrylate ester: Physical and mechanical properties

Grouting is a common technical method with many applications, e.g. it is used for soil stabilization and strengthening, for reduction of water ingress to underground facilities or of the water loss through a dam foundation, etc. Grouts comprise several constituents, which are combined in many ways depending on the in situ conditions and the outcome desired. Superplasticizers, accelerators, antifreezers, air-entraining agents and many others are generally used to improve the quality of cement grouts and consequently, their effectiveness on strength (especially bond strength), durability, impermeability and resistance to chemical erosion of the grouted soil or rock mass. A comprehensive laboratory work was carried out in order to study the physical and mechanical properties of grouts prepared by using cement, clay, water in different percentages along with an amount of acrylic resin or methyl methacrylate co-polymer emulsion. Flowability, setting time, bleeding, compressive strength, elastic modulus, shear bond strength, resistance to wet–dry cycles and resistance to sulfate attack of the grouts were determined. The results of this study indicated that the addition of latexes improves significantly the compressive strength, shear bond strength, stability, resistance to wet–dry cycles and resistance to sulfate attack, especially for thick pure cement grouts. This improvement depends on the type of latex.     

Mechanical and durability properties of high performance concretes containing supplementary cementitious materials

An experimental investigation was carried out to evaluate the mechanical and durability properties of high performance concretes containing supplementary cementitious materials in both binary and ternary systems. The mechanical properties were assessed from the compressive strength, whilst the durability characteristics were investigated in terms of chloride diffusion, electrical resistivity, air permeability and water absorption. The test variables included the type and the amount of supplementary cementitious materials (silica fume, fly ash and ground granulated blast-furnace slag). Portland cement was replaced with fly ash up to 40%, silica fume up to 15% and GGBS up to a level of 70%.The results confirmed that silica fume performs better than other supplementary cementitious materials for the strength development and bulk resistivity. The ternary mixes containing ground granulated blast-furnace slag/fly ash and silica fume performed the best amongst all the mixes to resist the chloride diffusion. The mix containing fly ash showed favourable permeation results. All the ternary combinations can be considered to have resulted in high performance concretes with excellent durability properties.     

Effect of slag on the rheology of fresh self-compacted concrete

The building industry is turning increasingly to the use of self-compacting concrete (SCC) in order to improve many aspects of building construction as SCC offers several advantages in technical, economic, and environmental terms. Fresh self-compacting concrete (SCC) flows into place and around obstructions under its own weight to fill the formwork completely and self-compact without any segregation and blocking. SCC mixes generally have a much higher content of fine fillers. The use of supplementary cementitious materials is well accepted because of the improvement in concrete properties and also for environmental and economical reasons. The present paper is an effort to quantify the influence of Algerian slag on the properties of fresh and hardened self-compacting concrete. The workability-related fresh properties of SCC were observed through slump flow time and diameter, V-Funnel flow time, J-Ring test, U-Box filling height and GTM sieve stability test. The only hardened property that was included in this study was the compressive strength. An optimum slag content of 15% seems to give a good SCC mixture with workability retention of about 60 min. A decrease in compressive strength with increase of slag content was obtained, but this decrease in compressive strength is less important at late ages (56 and 90 days after mixing).     

煤气化渣对水泥混凝土性能的影响

为探讨煤气化渣应用于水泥混凝土的可行性,将2种类型的煤气化渣分别制备混凝土试件并对其性能进行研究。采用扫描电镜和能谱仪分析煤气化渣微观结构与元素组成,并测试其基本物理性能;进一步研磨煤气化渣,制备掺煤气化渣混凝土试件,测试混凝土的抗压强度、干缩性能,并与普通混凝土性能进行比较。结果表明:煤气化渣组分中含有大量非晶态胶凝活性物质,在混凝土中掺入研磨后的粗渣,其抗压强度远高于基准混凝土,且随着龄期延长后期强度持续上升;掺细渣混凝土强度低于基准混凝土,且细渣研磨后对强度增长不大;掺煤气化渣有利于减小混凝土干缩率,煤气化渣研磨后比表面积增大,混凝土干缩率略有增大;综合考虑,推荐在混凝土中使用研磨后的粗渣部分替代天然砂作为混凝土细集料。     

Effect of copper slag as a fine aggregate on the properties of cement mortars and concrete

An experimental investigation was conducted to study the effect of using copper slag as a fine aggregate on the properties of cement mortars and concrete. Various mortar and concrete mixtures were prepared with different proportions of copper slag ranging from 0% (for the control mixture) to 100% as fine aggregates replacement. Cement mortar mixtures were evaluated for compressive strength, whereas concrete mixtures were evaluated for workability, density, compressive strength, tensile strength, flexural strength and durability. The results obtained for cement mortars revealed that all mixtures with different copper slag proportions yielded comparable or higher compressive strength than that of the control mixture. Also, there was more than 70% improvement in the compressive strength of mortars with 50% copper slag substitution in comparison with the control mixture. The results obtained for concrete indicated that there is a slight increase in density of nearly 5% as copper slag content increases, whereas the workability increased significantly as copper slag percentage increased compared with the control mixture. A substitution of up to 40–50% copper slag as a sand replacement yielded comparable strength to that of the control mixture. However, addition of more copper slag resulted in strength reduction due to the increase in the free water content in the mix. Also, the results demonstrated that surface water absorption decreased as copper slag content increases up to 50% replacement. Beyond that, the absorption rate increased rapidly and the percentage volume of the permeable voids was comparable to the control mixture. Therefore, it is recommended that up to 40–50% (by weight of sand) of copper slag can be used as a replacement for fine aggregates in order to obtain a concrete with good strength and durability requirements.     

Production of non-constructive concrete blocks using contaminated soil

In this research, a heavily contaminated humus-rich peat soil and a lightly contaminated humus-poor sand soil, extracted from a field location in the Netherlands, are immobilized. These two types of soil are very common in the Netherlands. The purpose is to develop financial feasible, good quality immobilisates, which can be produced on large scale.To this end, two binder combinations were examined, namely slag cement with quicklime and slag cement with hemi-hydrate. The mixes with hemi-hydrate proved to be better for the immobilization of humus rich soils, having a good early strength development. The heavily contaminated soil with 19% humus (of dm) could not be immobilized using 398 kg slag cement and 33 kg quicklime per m³ concrete mix (binder = 38.4% dm soil). It is possible to immobilize this soil using 480 kg binder (432 kg slag cement, 48 kg quicklime) per m³ of mix (58.2% dm). An alternative to the addition of extra binder (slag cement with quicklime) is mixing the soil with sand containing particles in the range of 0–2 mm. This not only improved the compressive strength of the immobilisates, but also reduced the capillary absorption. All the mixes with the lightly contaminated soil were cost-effective and suitable for production of immobilisates on a large scale. These mixes had good workability, a good compressive strength and a low capillary absorption. The leaching of all mixes was found to be much lower than allowed by the regulations. Given these results, the final mixes in the main experiment fulfilled all the financial and technical objectives.     

Properties of concrete prepared with crushed fine stone,furnace bottom ash and fine recycled aggregate as fine aggregates

This paper presents the results of a study to compare the properties of concretes prepared with the use river sand, crushed fine stone (CFS), furnace bottom ash (FBA), and fine recycled aggregate (FRA) as fine aggregates. Two methods were used to design the concrete mixes: (i) fixed water–cement ratio (W/C) and (ii) fixed slump ranges. The investigation included testing of compressive strength, drying shrinkage and resistance to chloride-ion penetration of the concretes. The test results showed that, at fixed water–cement ratios, the compressive strength and the drying shrinkage decreased with the increase in the FBA content. FRA decreased the compressive strength and increased the drying shrinkage of the concrete. However, when designing the concrete mixes with a fixed slump value, at all the test ages, when FBA was used as the fine aggregates to replace natural aggregates, the concrete had higher compressive strength, lower drying shrinkage and higher resistance to the chloride-ion penetration. But the use of FRA led to a reduction in compressive strength but increase in shrinkage values. The results suggest that both FBA and FRA can be used as fine aggregates for concrete production.     

矿物掺合料对C100～C120超高强混凝土基本性能的影响

通过正交试验考察了胶凝材料总量、水泥用量及超细粉煤灰用量对超高强混凝土抗压强度的影响,研究了硅灰、超细粉煤灰与复合硅材等矿物掺合料对C100~C120超高强混凝土基本性能的影响。结果表明,对超高强混凝土强度影响最主要的因素是水泥在胶凝材料中所占的比例;超细粉煤灰与硅灰复掺对超高强混凝土工作性能与强度改善效果较好;复合硅材对超高强混凝土的工作性能与强度均有一定的提高。     

水泥复合浆液在治理涌水涌砂基坑中的应用

本文研究的CWP水泥复合浆液含有水玻璃 (速凝剂 )和偏磷酸盐 (缓凝剂 )。水泥水化热试验和复合浆液可泵期试验证明 ,在CWP水泥复合浆液中 ,用磷酸二氢铵作缓凝剂效果最好。研制了三种复合浆液 (早凝型、早强型和防渗型 )的流变性、稳定性和结石体强度 ,并介绍了其中两种复合浆液在基坑抢险注浆工程中的应用。