废混凝土制作球型路障试验研究

针对建筑垃圾排放量大、利用率低以及石材路障消耗天然石材等问题,以废混凝土作为骨料,制作混凝土再生骨料型球型路障,试验研究了废混凝土取代率、减水剂用量等因素对其性能及外观效果的影响。结果表明废混凝土再生骨料可完全取代天然骨料制球型路障通过调节减水剂掺量,可改善制品的外观质量,减少表面孔洞发生。     

利用固体废弃物制作交通路障可行性

分析了目前常用交通路障的特点,简要概述了固体废弃物的排放和利用情况,提出利用固体废弃物制作交通路障的可行性,并阐述了固废型交通路障的优势,认为采用固体废弃物制作的交通路障,不但完全可以代替石材路障,而且具有石材路障不具备的优势。利废型路障的制作,不但可节约天然石材资源,还可再生利用固体废弃物,减少环境污染,一举多得。     

石煤废渣资源化利用的研究

对采用等量取代法以石煤废渣取代部分水泥制作混凝土进行研究.实验结果表明,石煤废渣具有超细结构,可与水泥形成"二级微观填充体系",能提高混凝土的密实度,改善混凝土界面结构和孔隙结构特征,使混凝土的可泵性、坍落度提高.综合利用作者简介:戴文灿,硕士,研究方向:清洁生产与资源综合利用,已发表论文十二篇.     

双掺粉煤灰再生骨料对混凝土强度影响研究

通过试验研究再生骨料混凝土中粉煤灰和再生骨料对混凝土强度的影响。采用粉煤灰替代部分水泥、再生骨料替代部分天然粗骨料的方法,通过正交试验测定混凝土立方体抗压强度的方法,来研究粉煤灰对再生骨料混凝土强度的影响。试验得出:当再生骨料掺量为20%~30%时,粉煤灰的最佳掺量为20%左右;当再生骨料掺量高于40%、粉煤灰掺量高于20%时,其混凝土拌合物搅拌时间不小于240 s,且当粉煤灰在20%~30%时,可获得较理想的混凝土抗压强度;当粉煤灰的掺入量分布在20%~30%、再生骨料的最佳掺量为50%时,可获得较理想的混凝土抗压强度。由此得出,合理的再生骨料、粉煤灰掺量对混凝土的抗压强度影响并不明显且有提高的趋势,对降低混凝土成本,提高建筑垃圾的再生利用,有一定的经济效益和社会效益。     

梅州市建筑废弃物再生利用研究

研究分析梅州市混凝土运输车洗涮废水和废弃混凝土对新拌混凝土力学性能的影响。结果表明:洗车废水呈碱性,将其替代部分自来水拌制混凝土,会引起新制混凝土强度降低;在流动度恒定的条件下,用火灾后废弃混凝土作骨料时,混凝土用水泥浆体量增加而强度则降低,建议掺入量以小于35%为宜。     

再生骨料基本性质及对混凝土性能影响的研究

系统研究了废弃混凝土经破碎、分级、清洗后得到的再生骨料的基本性质,揭示了再生骨料较天然花岗岩骨料密度小、空隙率大、吸水率和吸水速率大及压碎指标大等特点.同时还讨论了再生骨料对新拌混凝土和易性和抗压强度的影响规律,再生骨料将使新拌混凝土的流动性降低,但粘聚性和保水性较好,使硬化混凝土的抗压强度略有降低.     

废旧混凝土资源化再生利用技术

试验研究了再生混凝土的基本性质,讨论了废旧混凝土资源化再生利用技术的可行性和有效途径.     

成型方式对不同骨料透水混凝土性能影响试验研究

采用4种不同成型方式分别制作再生骨料透水混凝土和天然骨料透水混凝土,研究其强度和透水性能的变化规律.试验结果表明:手工振捣+平板振动成型方式制作的透水混凝土,具有较高的强度与优良的透水性能,为最佳的成型方式;同配比时,再生骨料透水混凝土较天然骨料混凝土强度更高,透水性能也较好.     

粉煤灰混凝土中凝胶水合物稳定存在的热力学条件探讨

混凝土中凝胶产物的稳定性直接影响到混凝土构件的安全耐久性。本文以研究粉煤灰混凝土中水合硅酸钙、水合铝酸钙的稳定条件为目的，通过对水合凝胶产物水解反应的标准自由焓变的计算，讨论了在自然环境水的侵蚀下，粉煤灰混凝土中某些凝胶产物稳定存在的热力学条件。     

C20全废混凝土再生骨料透水混凝土配比试验

为了再利用建筑垃圾,节约天然骨料资源,试验骨料全部采用废混凝土,研究水灰比、胶骨比及减水剂对废混凝土再生骨料透水混凝土性能的影响。结果表明:在胶骨比不变时,水灰比增加,抗压强度增加、孔隙率降低;在水灰比不变时,胶骨比增加,抗压强度增加、孔隙率降低;减水剂可以改善拌合物的和易性,从而提高抗压强度,降低孔隙率,但加入量不宜过大;用全废混凝土完全可配制出符合规范要求的透水混凝土。     

A study of the effects of LCD glass sand on the properties of concrete

In order to study the recycling of discarded liquid crystal display (LCD) glass into concrete (LCDGC), a portion of the usual river sand was replaced by sand prepared from discarded LCD glass. Three different mix designs were regulated by the ACI method (fc(28)=21, 28, and 35MPa) with 0%, 20%, 40%, 60%, and 80% LCD glass sand replacements investigated; their engineering properties were determined. Test results revealed that, when compared to the design slump of 15cm, the 20% glass sand concrete for the three different mix designs kept good slump and slump flow. Furthermore, a slump loss ranging from 7 to 11cm was observed for specimens with 60% and 80% glass sand replacement for the design strengths of 28 and 35MPa. The compressive strengths of the concrete with glass sand replacement were higher than the design strengths. Moreover, the durability of the concrete with 20% glass sand replacement was better than that of the control group. Surface resistivity for specimens with different amounts of LCD glass sand replacement was also higher than that in the control group for mid to long curing ages. The sulfate attack in concrete with different amounts of glass sand replacement caused less weight loss than in the control group. Moderate chloride ion penetration was observed for glass sand concrete. Furthermore, the measured ultrasonic pulse velocities for LCD glass sand concrete specimens were higher than 4100m/s, which qualified these specimens as good concrete. OM and SEM indicate that the dense C-S-H gel hydrate was produced at the interface between the glass sand and cement paste. The test results indicate that the addition of 20% LCD glass sand to concrete satisfies the slump requirements and improves the strength and durability of concrete. This suggests that LCD glass sand can potentially be used as a recycled material in concrete applications.     

Waste tyre rubberized concrete: Properties at fresh and hardened state

The main objective of this paper is to investigate the properties of various concrete mixtures at fresh and hardened state, obtained by a partial substitution of coarse and fine aggregate with different volume percentages of waste tyres rubber particles, having the same dimensions of the replaced aggregate. Workability, unit weight, compressive and flexural strength and post-cracking behaviour were evaluated and a comparison of the results for the different rubcrete mixtures were proposed in order to define the better mix proportions in terms of mechanical properties of the rubberized concrete. Results showed in this paper were also compared to data reported in literature. Moreover, a preliminary geometrical, physical and mechanical characterization on scrap tyre rubber shreds was made.The rubberized concrete mixtures showed lower unit weight compared to plain concrete and good workability. The results of compressive and flexural tests indicated a larger reduction of mechanical properties of rubcrete when replacing coarse aggregate rather than fine aggregate. On the other hand, the post-cracking behaviour of rubberized concrete was positively affected by the substitution of coarse aggregate with rubber shreds, showing a good energy absorption and ductility indexes in the range observed for fibrous concrete, as suggested by standard (ASTM C1018-97, 1997).     

全废砖再生轻骨料混凝土试验研究

将废粘土砖加工成粗细骨料,用于配制全废砖再生轻骨料混凝土.检测结果表明：所用废砖粗细骨料属轻骨料范畴,但其吸水率较大,且细骨料级配不良.试验表明：本试验配合比体系中,净水灰比为0.42,体积砂率为50％时最佳;以全废砖配制的再生砖轻骨料混凝土的强度发展规律与普通轻骨料混凝土类似,均有随水泥用量提高而强度提高的趋势,但随着所配制的混凝土强度等级的提高,再生轻骨料混凝土的强度提高趋势下降.以全废砖为骨料适合配制强度等级LC30及以下的再生轻骨料混凝土.     

再生混凝土骨料对钢渣骨料透水混凝土性能影响试验研究

将再生混凝土骨料以不同比例取代钢渣骨料配制透水混凝土,采用沸煮试验法考察废混凝土骨料对钢渣透水混凝土强度和体积稳定性的影响,结果表明:再生混凝土骨料可改善钢渣透水混凝土强度,减轻钢渣骨料膨胀对透水混凝土体积稳定性的影响,用再生混凝土骨料在改善钢渣骨料透水混凝土性能同时可消纳两种固体废弃物,具有环境效益和社会效益。     

Reuse of municipal solid wastes incineration fly ashes in concrete mixtures

This study is aimed at assessing the feasibility of concrete production using stabilized m.s.w. (municipal solid waste) incineration fly ashes in addition to natural aggregates. The tested fly ashes were washed and milled, then stabilized by a cement-lime process and finally were reused as a "recycled aggregate" for cement mixture production, in substitution of a natural aggregate (with dosage of 200-400 kg m(-3)). These mixtures, after curing, were characterized with conventional physical-mechanical tests (compression, traction, flexure, modulus of elasticity, shrinkage). In samples containing 200 kg(waste) m(-3)(concrete), a good compressive strength was achieved after 28 days of curing. Furthermore, concrete leaching behavior was evaluated by means of different leaching tests, both on milled and on monolithic samples. Experimental results showed a remarkable reduction of metal leaching in comparison with raw waste. In some cases, similar behavior was observed in "natural" concrete (produced with natural aggregates) and in "waste containing" concrete.     

Use of rubble from building demolition in mortars

Because of increasing waste production and public concerns about the environment, it is desirable to recycle materials from building demolition. If suitably selected, ground, cleaned and sieved in appropriate industrial crushing plants, these materials can be profitably used in concrete. Nevertheless, the presence of masonry instead of concrete rubble is particularly detrimental to the mechanical performance and durability of recycled-aggregate concrete and the same negative effect is detectable when natural sand is replaced by fine recycled aggregate fraction. An alternative use of both masonry rubble and fine recycled material fraction could be in mortars. These could contain either recycled instead of natural sand or powder obtained by bricks crushing as partial cement substitution. In particular, attention is focused on the modification that takes place when either polypropylene or stainless steel fibers are added to these mortars. Polypropylene fibers are added in order to reduce shrinkage of mortars, stainless steel fibers for improving their flexural strength. The combined use of polypropylene fibers and fine recycled material from building demolition could allow the preparation of mortars showing good performance, in particular when coupled with bricks. Furthermore, the combined use of stainless steel fibers and mortars containing brick powder seems to be an effective way to guarantee a high flexural strength.     

Use of waste plastic in concrete mixture as aggregate replacement

Industrial activities in Iraq are associated with significant amounts of non-biodegradable solid waste, waste plastic being among the most prominent. This study involved 86 experiments and 254 tests to determine the efficiency of reusing waste plastic in the production of concrete. Thirty kilograms of waste plastic of fabriform shapes was used as a partial replacement for sand by 0%, 10%, 15%, and 20% with 800 kg of concrete mixtures. All of the concrete mixtures were tested at room temperature. These tests include performing slump, fresh density, dry density, compressive strength, flexural strength, and toughness indices. Seventy cubes were molded for compressive strength and dry density tests, and 54 prisms were cast for flexural strength and toughness indices tests. Curing ages of 3, 7, 14, and 28 days for the concrete mixtures were applied in this work. The results proved the arrest of the propagation of micro cracks by introducing waste plastic of fabriform shapes to concrete mixtures. This study insures that reusing waste plastic as a sand-substitution aggregate in concrete gives a good approach to reduce the cost of materials and solve some of the solid waste problems posed by plastics.     

Sustainable construction: composite use of tyres and ash in concrete

An investigation was carried out to establish the physical, mechanical and chemical characteristics of a non-standard (unprocessed) pulverised fuel ash (PFA) and waste tyres from a former landfill site at the Power Station Hill near Church Village, South Wales, United Kingdom. Investigations are on-going to establish the suitability of the fly ash and/or tyres in road construction (embankment and pavement) and also in concrete to be used in the construction of the proposed highway. This paper reports on concrete-based construction where concrete blends (using various levels of PFA as partial replacement for Portland cement (PC), and shredded waste tyres (chips 15-20mm) as aggregate replacement) were subjected to unconfined compressive strength tests to establish performance, hence, optimising mix designs. Strength development up to 180 days for the concrete made with PC-PFA blends as binders (PC-PFA concrete), with and without aggregate replacement with tyre chips, is reported. The binary PC-PFA concrete does not have good early strength but tends to improve at longer curing periods. The low early strength observed means that PC-PFA concrete cannot be used for structures, hence, only as low to medium strength applications such as blinding, low-strength foundations, crash barriers, noise reduction barriers, cycle paths, footpaths and material for pipe bedding.     

Utilization of municipal solid waste bottom ash and recycled aggregate in concrete

In the combustion process of municipal solid waste (MSW), bottom ash (BA) represents the major portion of the solid residue. Since BA is composed of oxides, especially SiO(2) and CaO, the feasibility of its application in concrete as a substitute for cement was tested. It was found that at the age of 28 days, the flexural and compressive strengths of the binder linearly decrease at the rate of 0.03 and 0.02 MPa per wt% of BA in the binder, respectively. According to the results it may be recommended to replace up to 15 wt% of cement by BA and to use such binder where a low strength of concrete elements is required. Furthermore, the aggregate used for low strength concrete need not be of a very good quality. Therefore, gravel aggregate was partially replaced by recycled aggregate (RA). Consistency measured by slump was significantly reduced (>50%) when BA or/and RA were introduced into the mixture. However, concrete density and compressive strength were not affected and were approximately 2300 kg/m(3) and approximately 40 MPa, respectively.