Recycling waste latex paint in concrete

Currently, in Ontario, Canada, around 21.7% of the total hazardous waste (HZW) collected by municipalities is waste paint. Waste latex paint (WLP) alone constitutes 12% of the total HZW. It is estimated that only 10-30% of this waste is presently being collected but this proportion is growing with public education efforts. In addition, due to increasingly more stringent environmental regulations on volatile organic compounds (VOCs), more latex-based paints will be produced compared to solvent- and oil-based alkyds. This will result in more WLP being generated annually in Ontario and across North America. The disposal cost of such waste currently varies between Can$0.90 and Can$1.40 per litre. This study was conducted in collaboration with the City of London, Ontario and the Ontario Paints and Coatings Association and aims at investigating the benefits of recycling WLP in concrete with a special focus on concrete sidewalks. WLP was used in concrete mixtures both as a partial replacement for virgin latex and for mixing water. This paper demonstrates that concrete mixtures incorporating WLP can have improved workability, higher flexural strength, lower chloride ion penetrability, better resistance to deicing salt surface scaling and can be more economic because they require less water-reducing and air-entraining admixtures. The results also indicate that the annual urban concrete sidewalk construction could use the yearly production of WLP while producing sidewalks with enhanced properties and durability.     

Durability of recycled aggregates concrete: a safe way to sustainable development

Fine and coarse recycled aggregates recovered from demolished masonry and concrete structures were utilized in the manufacture of new concrete mixtures. Three properties of these new concretes were analyzed: water absorption, total pores volume, and carbonation. The recycled concrete families were created by replacing parts of the natural aggregates forming families of concrete with 0%, 20%, 50%, and 100% of aggregates from recycled sources. The usual comparison between mixtures by comparison between behaviors of concrete families. This research shows that the mix design nomogram (MDN) is a new and useful tool that allows the researchers to compare properties and behaviors of different concretes. The results show that the family concrete with the highest pore volume and with the same compressive strength of 20, 30, and 40 MPa (2900, 4350, and 5800 psi) did not always correspond to the concrete family with the highest degree of carbonation. This experiment also showed that some compositional characteristics of concrete could have more influence on the durability that the traditional physical aspects.     

Effect of incorporating PVC waste as aggregate on the physical,mechanical, and chloride ion penetration behavior of concrete

With the growing needs for resource materials and the environmental protection requirements associated with sustainable development, it has become necessary to study all the possibilities of reusing and recycling industrial wastes and by-products, especially in the field of civil engineering. In the work presented here, non-biodegradable plastic aggregates made of polyvinylchloride (PVC) waste, obtained from scrapped PVC pipes, were used in partial replacement of conventional aggregates in concrete. For this purpose, a number of laboratory prepared concrete mixes were tested, in which natural sand and coarse aggregates were partially replaced by PVC plastic waste aggregates in the proportions of 30, 50, and 70% by volume (granular classes 0/3 and 3/8). Fresh concrete mixtures were tested for workability and density, and hardened concrete specimens were used to investigate compressive strength, ultrasonic wave velocity, and resistance to chloride ion penetration. The results of the laboratory study showed that concrete made with 50 and 70% of recycled PVC aggregates fell into the category of structural lightweight concrete in terms of unit weight and strength properties. This study gave quite encouraging results and opened up a new way of recycling PVC waste as a lightweight aggregate in concrete.     

再生粗骨料附着砂浆含量对再生混凝土抗冻耐久性的影响

选取五种不同附着砂浆含量的商用再生粗骨料在全取代天然粗骨料条件下制备C40再生混凝土,探讨了30%极限拉应力水平下,再生粗骨料附着砂浆含量对再生混凝土抗冻耐久性的影响规律,通过数学拟合确定了基于相对动弹性模量和抗冻耐久性指数要求的砂浆界限含量。结果表明:冻融循环后,再生混凝土抗压强度损失率与附着砂浆含量存在较强线性关系;再生混凝土质量损失率、相对动弹性模量、抗冻耐久性指数均与再生粗骨料附着砂浆含量呈二次函数关系;以冻融循环300次后再生混凝土相对动弹性模量降至60%为限值,获得对应的砂浆界限含量为49.52%(质量分数);以不同设计使用年限及不同冻融工况所规定的抗冻耐久性指数作为界定条件,得到了再生混凝土在拉应力条件下满足相应抗冻耐久性指数的砂浆界限含量。最后,通过搜集文献数据验证了本研究结果的合理性。     

花岗岩废料再生混凝土路面砖抗冻融性能研究

采用慢冻法对花岗岩废料再生混凝土路面砖进行50次冻融循环试验,以质量损失与抗压强度作为依据研究影响再生混凝土路面砖抗冻融性变化规律。基于体积膨胀及渗透压理论并结合扫描电镜分析,对比冻融前后再生混凝土路面砖显微结构与水化产物组成,从细微裂缝积累与膨胀性应力作用角度揭示其冻融损伤机理,建立浆体孔隙结构变化模型和浆体浓度差所产生的渗透压模型。研究结果表明,微、细、粗集料分别以20%、30%、50%(质量分数)为最佳取代率的再生混凝土路面砖的质量损失率为1.5%,抗压强度损失率为10.0%,较基准组有所降低,但较大程度上提高了花岗石废料的利用率,且满足试验标准和路用性能的基本要求。微观分析结果表明,浆体水化产物中较高的钙矾石含量使混凝土微裂缝富集,最终形成宏观裂缝导致冻胀破坏,所建立的模型揭示了外界水的侵入引起体积膨胀、毛细孔与凝胶孔中浆体浓度差所产生渗透压引起的膨胀性应力是致使冻融损伤发生的真正原因。     

Breakage of waste concrete by free fall

For producing high-quality recycled aggregates from waste concrete, the characteristics of waste concrete when subjected to breakage by impact were investigated under free-fall conditions at various heights. In general, a lump of waste concrete did not disintegrate by a single impact, but underwent abrasion and occasional chipping before eventually breaking into several pieces. Further, when the sample was pretreated by heat, the number of free falls required for disintegrative fracture reduced markedly. Moreover, the resulting recycled aggregates had less adherent cement mortar due to weakening of the bonding strength between the aggregates and the cement mortar. Therefore, the energy penalty resulting from preheating the sample could be partially compensated for by the production of high-quality recycled aggregates. These results suggest that preheating followed by gentle breakage through free fall is an efficient technique to produce high-quality recycled aggregates from waste concrete.     

A method for assessment of the freeze-thaw resistance of preformed foam cellular concrete

The growing use of cellular concrete for building materials and geotechnical fills brings forth the question of suitable durability and performance standards. Of particular importance is the performance of cellular concrete in freezing and thawing environments. Since the macrostructure of cellular concrete or cellular control low-strength material is not like that of normal-weight concrete, a modified procedure is needed to specify the required characteristics of cellular concrete that lead to freeze-thaw durability. This research investigated the freeze-thaw durability of cellular concrete and developed a modified freeze-thaw test procedure, based on ASTM C666. Physical properties related to freeze-thaw durability were measured for each mixture and compared to the initial properties. As a result of these comparisons, recommendations are made regarding the production of freeze-thaw-resistant preformed foam cellular concrete exposed to freeze-thaw environments. The results of the study show that depth of absorption was a key predictor in developing freeze-thaw-resistant concrete. Compressive strength, depth of initial penetration, absorption and absorption rate are the important variables in producing cellular concrete that is resistant to cycles of freezing and thawing. Density and permeability were shown not to be significant variables.     

Effect of supplementary cementitious materials on the compressive strength and durability of short-term cured concrete

This research focuses on studying the effect different supplementary cementitious materials (silica fume, fly ash, slag, and their combinations) on strength and durability of concrete cured for a short period of time—14 days. This work primarily deals with the characteristics of these materials, including strength, durability, and resistance to wet and dry and freeze and thaw environments. Over 16 mixes were made and compared to the control mix. Each of these mixes was either differing in the percentages of the additives or was combinations of two or more additives. All specimens were moist cured for 14 days before testing or subjected to environmental exposure. The freeze-thaw and wet-dry specimens were also compared to the control mix.Results show that at 14 days of curing, the use of supplementary cementitious materials reduced both strength and freeze-thaw durability of concrete. The combination of 10% silica fume, 25% slag, and 15% fly ash produced high strength and high resistance to freeze-thaw and wet-dry exposures as compared to other mixes. This study showed that it is imperative to cure the concrete for an extended period of time, especially those with fly ash and slag, to obtain good strength and durability. Literature review on the use of different supplementary cementitious materials in concrete to enhance strength and durability was also reported.     

煤矸石混凝土水分传输及分布预测

为了研究煤矸石作为粗骨料对混凝土耐久性的影响,参照ASTM C1585-13推荐的方法,通过试验对煤矸石粗骨料混凝土的吸水性进行了研究,其中煤矸石替代传统粗骨料的质量比分别为0%,30%,60%,100%.分析了煤矸石掺量对混凝土吸水性能的影响,对比了各组试件的初始吸水率和第二阶段吸水率.结果表明:煤矸石混凝土的吸水率呈现两阶段特征.煤矸石粗骨料的掺量对混凝土的吸水性有显著的影响,当煤矸石替代30%的传统粗骨料时,试件的初始吸水率和第二阶段吸水率与未掺煤矸石试件的初始吸水率和第二阶段吸水率相差不大,但是当煤矸石的替代量大于60%时,试件的初始吸水率和第二阶段吸水率会明显增大,说明煤矸石掺量影响混凝土的耐久性.最后根据吸水试验的结果,结合非饱和毛细吸水的相关理论,对煤矸石混凝土内水分分布进行了预测.     

同掺再生粗细骨料混凝土的力学与耐久性能研究

为了探讨同时掺入大掺量再生粗骨料和细骨料制备C40及以上强度等级再生混凝土的可行性,在C45天然骨料混凝土配合比的基础上,采用II类再生粗骨料、I类再生细骨料,以同掺再生粗细骨料质量替代率为25%、50%、75%、100%配制了4组再生混凝土,研究了再生粗细骨料替代率对再生混凝土基本力学性能和耐久性能的影响规律。结果表明:当同掺再生粗细骨料的替代率为25%时,混凝土的力学性能下降很小,替代率为50%、75%的混凝土的抗压强度分别达到C45、C40等级,替代率100%的全再生粗细骨料混凝土的28 d抗压、劈拉、轴压强度和弹性模量等力学性能指标较天然骨料混凝土降低12.0%~23.2%,并达到C35抗压强度等级。增加再生粗细骨料的替代率会降低混凝土的耐久性,但即使是全再生粗细骨料混凝土仍可获得高的耐久性,其抗碳化性能、抗氯离子渗透性、抗冻性能分别达到T-IV、RCM-IV和F300等级,说明在混凝土中同时掺用50%及以上再生粗细骨料配制C40及以上强度等级的再生混凝土是可行的。     

The effect of sealers on the freeze-thaw resistance of mortar

The freeze-thaw resistance of eight types of mortar specimens treated with 57 concrete sealers was determined. The reduction in water uptake resulting from the presence of sealer did not, in general, improve the freeze-thaw durability based on failure criteria of 0.02% expansion. Inverse relationship seems to exist between the sealer caused reduction of water uptake and freeze-thaw durability, as evidence by the plot of the average percent expansion vs. average water uptake. The results emphasize the importance of water transfer through the surface zone in partially saturated systems, a phenomenon not considered by the hydrostatic pressure theory.     

Studies on mechanical properties of concrete containing waste glass aggregate

Quantities of waste glass have been on the rise in recent years due to an increase in industrialization and the rapid improvement in the standard of living. Unfortunately, the majority of waste glass is not being recycled but rather abandoned, and is therefore the cause of certain serious problems such as the waste of natural resources and environmental pollution. For these reasons, this study has been conducted through basic experimental research in order to analyze the possibilities of recycling waste glasses (crushed waste glasses from Korea such as amber, emerald green, flint, and mixed glass) as fine aggregates for concrete. Test results of fresh concrete show that both slump and compacting factors are decreased due to angular grain shape and that air content is increased due to the involvement of numerous small-sized particles that are found in waste glasses. In addition the compressive, tensile and flexural strengths of concrete have been shown to decrease when the content of waste glass is increased. In conclusion, the results of this study indicate that emerald green waste glass when used below 30% in mixing concrete is practical along with usage of 10% SBR latex. In addition, the content of waste glasses below 30% is practical along with usage of a pertinent admixture that is necessary to obtain workability and air content.     

基于裹浆工艺的煤矸石混凝土性能研究

采用裹浆工艺对煤矸石骨料进行预处理,研究原状煤矸石骨料与不同浆体裹浆煤矸石骨料的吸水率、压碎值和干湿、冻融环境下的劣化行为以及裹浆煤矸石混凝土的强度和耐久性能,并分析骨料性能强化与混凝土性能提升的相关性。采用XRD、SEM分析原状煤矸石骨料与裹浆煤矸石骨料干湿、冻融循环前后的矿物组成、微观形貌和界面过渡区。结果表明,原状煤矸石骨料吸水率高,硬度低,在干湿、冻融环境下劣化明显,裹浆后煤矸石骨料性能提升。原状煤矸石混凝土强度与耐久性能较差,裹浆后煤矸石混凝土性能得到增强,骨料性能与混凝土性能相关性良好。煤矸石骨料劣化的主要原因是黏土矿物吸水后在干湿、冻融环境下软化失稳,而裹浆可以起到隔绝水分的作用,从而使骨料性能得到强化。骨料强化以及骨料与砂浆基体的结合程度提高共同促进了裹浆煤矸石混凝土性能提升。     

Frost resistance of recycled aggregate concrete

The research presented in this paper deals with concrete containing building waste recycled as aggregates. The frost resistance is used as a durability indicator. The characteristics of recycled aggregates (RAs) and their impact on the characteristics of RA concrete are presented. Some basic factors concerning the frost resistance of RA concrete as RA content and degree of water saturation are considered. The RA concrete is compared with a control concrete made with natural aggregates. The pertinence of different criteria for the assessment of the frost resistance is also discussed.     

氯盐冻融耦合作用下再生混凝土损伤劣化规律

为了研究严寒盐渍环境中再生混凝土的损伤劣化规律,制备了再生粗骨料质量替代率为0％、50％、100％的再生混凝土进行氯盐冻融耦合作用下的试验研究,从外观形貌、质量损失率、相对动弹性模量和抗压强度等方面探讨混凝土损伤劣化规律.结果表明,氯盐冻融对再生骨料混凝土的破坏随再生骨料替代率的增加而增大.与冻融循环0次相比,冻融循环...     

The effects of different fine and coarse pumice aggregate/cement ratios on the structural concrete properties without using any admixtures

Structural lightweight concrete solves weight and durability problems in buildings and structures. In order to produce the high strength concrete in the civil engineering applications, lightweight concrete mixtures containing the fine pumice aggregate (FPA) from Nev°ehir region in Turkey and coarse pumice aggregate (CPA) from Yali Island in the Eastern Mediterranean were tested and the research findings were discussed in this paper. To analyse the effects of FPA and CPA/cement ratios on the structural concrete engineering properties, the range of different pumice aggregate/cement (A/C) ratios of 2:1, 2 1/2:1, 3:1, 3 1/2:1 and 4:1 by weight and cement contents of 440, 375, 320, 280 and 245 kg/m³, respectively, were used to make pumice aggregate lightweight concrete (PALC) mixture testing samples with a slump of from 35 to 45 mm.The experimental research findings showed that PALC has strengths comparable to normal weight concrete, yet is typically 30-40% lighter. PALC showed the design flexibility and substantial cost savings by providing less dead load due to its lower density values. The properties, which increase in value and indicate the increasing quality with lower A/C ratios (high cement contents), are compressive strength, modulus of elasticity and density. Properties, which decrease in value and indicate the increasing quality, with lower A/C ratios are water absorption and carbonation depth. In all cases, lowering the A/C ratio (higher cement content) increases quality. The research showed that structural lightweight concrete can be produced by the use of fine and coarse pumice aggregates mixes without using any additions or admixtures.     

影响混凝土结构耐久性的相关因素和控制对策

针对混凝土耐久性受多重因素的影响,对其不同因素探讨对提高混凝土的耐久性能具有很大的现实价值。对此,从冻融环境和硫酸盐腐蚀的角度对该问题进行研究,首先结合不同的原材料和混凝土强度要求,制备试验用的混凝土试件;其次,结合干湿循环试验和冻融试验分别对试件进行试验。通过实验结果发现,水胶比、硫酸钠浓度等混凝土的耐久性有着很大的影响。提出了在实际工程中如何提高混凝土的耐久性提出几点建议,以此为混凝土制备提供借鉴与参考。     

Utilisation of Turkish fly ashes in cost effective HVFA concrete production

High-volume fly ash (HVFA) concrete is an economical and durable option for structural as well as general concreting purposes, if properly controlled ashes are employed. The aim of this study was to investigate the possibility of the use of three types of Turkish fly ashes from different sources in cost effective high-volume fly ash concrete production. For this purpose HVFA concrete mixtures were prepared by substituting 40, 50, 60 and 70% of cement by fly ash. The mechanical properties and material costs of mixtures were compared with conventional concrete at the same strength grade at 28 days. It should be noted that as an additional benefit, the long-term strength development and durability advantageous of HVFA concrete is not taken into consideration in cost analysis. Results showed that for structural applications a technically suitable and cost effective HVFA concrete can only be produced by using the fly ashes within the limits of specific chemical and physical properties. It may be possible to use other fly ashes with rehabilitation and pre-process, which may reduce the economical feasibility of fly ash usage.     

Production and optimization of sustainable cement brick incorporating clay brick wastes using response surface method

This paper aims to fabricate and optimize eco-sustainable cement brick using different sizes of clay brick waste (CBW). The prime input factors of mixtures were clay brick powder (CBP) as a binder, fine-clay brick (FCB) as a fine aggregate, and coarse-clay brick (CCB) as a coarse aggregate, whereas the compressive strength was the main response of the generated eco-sustainable bricks. This was accomplished by utilizing the central composite design (CCD) and Response Surface Methodology (RSM) with Minitab-19. Twenty mixtures with CBW were generated and experimentally evaluated utilizing CCD concept in RSM. A multi-objective optimization approach was applied to obtain the optimum results for the input parameters. Based on an experimental program, the optimum mixtures were selected to investigate the physical and durability properties of the produced brick. The SEM test was also performed to determine the effect of the CBW particles on the microstructure of the brick. The life cycle assessment of mixtures is also performed in terms of global warming potential. The optimization showed that the input components CBP, FCB, and CCB had average optimum values of 21%, 0%, and 9.09%, respectively. The experimental results showed that employing CBW yields a durable and high freeze-thaw resistance of the eco-sustainable brick despite its high porosity and absorption. Furthermore, using cement brick with CBW particles is acknowledged as a more environmentally beneficial combination. The proposed models can speed up the process of mix design by using different sizes of brick waste to get the optimum eco-friendly cement brick properties.     

再生骨料构成对混凝土性能的影响

通过测试混凝土力学性能和耐久性指标,分析再生骨料构成变化对混凝土性能的影响规律.结果表明:再生砂浆块混凝土28 d前抗压强度较高,长期强度则天然骨料混凝土最高.经过100次冻融循环后,再生骨料混凝土质量损失率均低于5%.天然骨料和再生砂浆块混凝土的抗压强度损失率低于25%,而由30%砖块与70%砂浆块组成的混合骨料混凝土及再生砖块混凝土均超过了限值.各类再生骨料混凝土均可满足P10的抗渗等级要求.其中,天然骨料混凝土抗渗能力最强,其次为再生砂浆块混凝土、再生混合骨料混凝土和再生砖块混凝土;各类混凝土抗氯离子渗透能力与抗渗能力排列顺序一致.以上研究表明,再生骨料中的砖块对混凝土力学性能影响较小,但对耐久性能的负面影响较为显著.