Macro-mechanics and Microstructure of Nanomaterial-modified Geopolymer Concrete: A Comprehensive Review

We have described in detail the effects of nano-SiO_(2),nano-CaCO_(3),carbon nanotubes,and nano-Al_(2)O_(3) on geopolymer concrete from the perspectives of macro mechanics and microstructure.The existing research results show that the mechanism of nano-materials on geopolymer concrete mainly includes the filling effect,nucleation effect,and bridging effect,the appropriate amount of nano-materials can be used as fillers to reduce the porosity of geopolymer concrete,and can also react with Ca(OH)2 to produce C-S-H gel,thereby improving the mechanical properties of geopolymer concrete.The optimum content of nano-SiO_(2) is between 1.0%and 2.0%.The optimum content of nano-CaCO_(3) is between 2.0%and 3.0%.The optimum content of carbon nanotubes is between 0.1%and 0.2%.The optimum content of nano-Al_(2)O_(3) is between 1.0%and 2.0%.The main problems existing in the research and application of nanomaterial-modified geopolymer concrete are summarized,which lays a foundation for the further application of nanomaterial in geopolymer concrete.

Prediction of Geopolymer Concrete Compressive Strength Using Convolutional Neural Networks

Geopolymer concrete emerges as a promising avenue for sustainable development and offers an effective solution to environmental problems.Its attributes as a non-toxic,low-carbon,and economical substitute for conventional cement concrete,coupled with its elevated compressive strength and reduced shrinkage properties,position it as a pivotal material for diverse applications spanning from architectural structures to transportation infrastructure.In this context,this study sets out the task of using machine learning(ML)algorithms to increase the accuracy and interpretability of predicting the compressive strength of geopolymer concrete in the civil engineering field.To achieve this goal,a new approach using convolutional neural networks(CNNs)has been adopted.This study focuses on creating a comprehensive dataset consisting of compositional and strength parameters of 162 geopolymer concrete mixes,all containing Class F fly ash.The selection of optimal input parameters is guided by two distinct criteria.The first criterion leverages insights garnered from previous research on the influence of individual features on compressive strength.The second criterion scrutinizes the impact of these features within the model’s predictive framework.Key to enhancing the CNN model’s performance is the meticulous determination of the optimal hyperparameters.Through a systematic trial-and-error process,the study ascertains the ideal number of epochs for data division and the optimal value of k for k-fold cross-validation—a technique vital to the model’s robustness.The model’s predictive prowess is rigorously assessed via a suite of performance metrics and comprehensive score analyses.Furthermore,the model’s adaptability is gauged by integrating a secondary dataset into its predictive framework,facilitating a comparative evaluation against conventional prediction methods.To unravel the intricacies of the CNN model’s learning trajectory,a loss plot is deployed to elucidate its learning rate.The study culminates in compelling findings that underscore the CNN model’s accurate prediction of geopolymer concrete compressive strength.To maximize the dataset’s potential,the application of bivariate plots unveils nuanced trends and interactions among variables,fortifying the consistency with earlier research.Evidenced by promising prediction accuracy,the study’s outcomes hold significant promise in guiding the development of innovative geopolymer concrete formulations,thereby reinforcing its role as an eco-conscious and robust construction material.The findings prove that the CNN model accurately estimated geopolymer concrete’s compressive strength.The results show that the prediction accuracy is promising and can be used for the development of new geopolymer concrete mixes.The outcomes not only underscore the significance of leveraging technology for sustainable construction practices but also pave the way for innovation and efficiency in the field of civil engineering.

Properties of Chemically Synthesized Nano-geopolymer Cement based Self-Compacting Geopolymer Concrete(SCGC)

The physical and mechanical properties of self-compacting geopolymer concrete(SCGC) using chemically synthesized nano-geopolymer cement was investigated. Nano-geopolymer cement was synthesized using nano-silica, alkali activator, and sodium aluminate in the laboratory. Subsequently, nine nanogeopolymer cement sbased SCGC mixes with varying nano-geopolymer cement content, alkali activator content, coarse aggregate(CA) content, and curing temperature were produced. The workability-related fresh properties were assessed through slump flow diameter and slump flow rate measurements. Mechanical performances were evaluated through compressive strength, splitting tensile strength, and modulus of elasticity measurements. In addition, rapid chloride penetration test, water absorption, and porosity tests were also performed. It was assessed that all mix design parameters influenced the fresh and hardened properties of SCGC mixes. Based on test results, it was deduced that nano-geopolymer cement SCGC performed fairly well. All the SCGC mixes achieved the 28-day compressive strength in the range of 60-80 MPa. Additionally, all mixes attained 60% of their 28-day strength during the first three days of elevated temperature curing. FTIR and SEM analyses were performed to evaluate the degree of polymerization and the microstructure respectively for SCGC mixes.

Effect of silica fume on the fresh and hardened properties of fly ash-based self-compacting geopolymer concrete

The effect of silica fume on the fresh and hardened properties of fly ash-based self-compacting geopolymer concrete （SCGC） was investigated in this paper. The work focused on the concrete mixes with a fixed water-to-geopolymer solid （W/Gs） ratio of 0.33 by mass and a constant total binder content of 400 kg/m3. The mass fractions of silica fume that replaced fly ash in this research were 0wt%, 5wt%, 10wt%, and 15wt%. The workability-related fresh properties of SCGC were assessed through slump flow, V-funnel, and L-box test methods. Hardened concrete tests were limited to compressive, splitting tensile and flexural strengths, all of which were measured at the age of 1, 7, and 28 d after 48-h oven curing. The results indicate that the addition of silica fume as a partial replacement of fly ash results in the loss of workability; nevertheless, the mechanical properties of hardened SCGC are significantly improved by incorporating silica fume, especially up to 10wt%. Applying this percentage of silica fume results in 4.3% reduction in the slump flow; however, it increases the compressive strength by 6.9%, tensile strength by 12.8% and flexural strength by 11.5%.

Preparation and properties of geopolymer-lightweight aggregate refractory concrete

Geopolymer-lightweight aggregate refractory concrete (GLARC) was prepared with geopolymer and lightweight aggregate. The mechanical property and heat-resistance (950 ℃) of GLARC were investigated. The effects of size of aggregate and mass ratio of geopolymer to aggregate on mechanical and thermal properties were also studied. The results show that the highest compressive strength of the heated refractory concrete is 43.3 MPa,and the strength loss is only 42%. The mechanical property and heat-resistance are influenced by the thickness of geopolymer covered with aggregate,which can be expressed as the quantity of geopolymer on per surface area of aggregate. In order to show the relationship between the thickness of geopolymer covered with aggregate and the thermal property of concrete,equal thickness model is presented,which provides a reference for the mix design of GLARC. For the haydite sand with size of 1.18-4.75 mm,the best amount of geopolymer per surface area of aggregate should be in the range of 0.300-0.500 mg/mm2.

Utilization of Concrete Waste Aggregates Using Geopolymer Cement

Reuse of concrete waste, especially in large quantity, can save not only material but also cost for its disposal. This paper presents experiment results on the use of fine and coarse aggregates from concrete waste in geopolymer mortars and concretes. Geopolymeric cement is an inorganic compounds of aluminosilicates synthesized from precursors with high content of silica and alumina activated by alkali silicate solutions. Geopolymer in this experiment was synthesized from fly ash as the precursor and sodium silicate solution as the activator. Hardening of geopolymers was performed by heating the casted paste in an oven at -60~Cfor 3 to 36 hours. Compressive strength of geopolymer pastes and mortars using either fresh or waste fine aggregates were in the range of 19-26 MPa. Hardening time of 3 hours at 60~C followed by leaving the test pieces at room temperature for 7 day before testing results in similar strength to that of mortars cured for 36 hours at 60~C followed by leaving the samples at room temperature for 3 days. It suggests that optimum strength can be achieved by combination of heating time and rest period before testing, i.e the specimens age. Applying mix design with a target strength of 40 MPa, conventional Portland cement concretes using fresh aggregates reached 70% of its target strength at day-7. Compressive strength of geopolymer concretes with waste aggregates was -25 MPa at day-3 while geopolymer concretes with fresh aggregates achieved -39 MPa at day-3. It can be concluded that geopolymer concretes can achieve the target strength in only 3 days. However, the expected reinforcing effect of coarse aggregates in concrete was ineffective if waste coarse aggregates were used as the strength of the concretes did not increase significantly from that of the mortars. On the other hand, waste fine aggregates can be reused for making geopolymer mortars having the same strength as the geopolymer mortars using fresh aggregates.

Water Permeability in Fly Ash-Based Geopolymer Concrete

This research investigated the water permeability coefficient of fly ash-based geopolymer concrete. The effect of sodium hydroxide （Na（OH）） concentrations and Si/AI ratios on water permeability and compressive strength of geopolymer concretes were studied. The geopolymer concrete were prepared from Mae Moh fly ash with sodium silicate （Na2SiO3） and sodium hydroxide （Na（OH）） solutions. In the first group, concentration of Na（OH） was varied at 8, 10, 12, and 14 molar and the Si/AI ratio was kept constant at 1.98. In the second group, a concentration of Na（OH） was kept constant at 14 molar and the Si/AI ratio was varied at 2.2, 2.4, 2.6, and 2.8. The hardened concretes were air-cured in laboratory. The compressive strength and water permeability were tested at the age of 28 and 60 days. The results showed that compressive strengths of geopolymer concrete significantly increased with the increase of a concentration of Na（OH） and Si/AI ratio. The water permeability coefficients increase with the decrease of compressive strength. In addition, the high reduction of water permeability coefficients with time was found in geopolymer concrete with lower Na（OH） concentration than that higher Na（OH） concentration.

The Impact of Marine Water on Different Types of Coarse Aggregate of Geopolymer Concrete

This research studies the impact of different types of coarse aggregate on the behavior of geopolymer concrete based on both fly ash (FA) and ground granulated blast furnace slag (GGBFS) in different marine environments. Aiming to solve the problems caused by the construction and demolition waste and the depletion of natural aggregates, in the present study coarse recycled aggregates is used to produce new green concrete with a fly ash-slag based geopolymer. By this examination, the research seeks to improve the quality and productivity of concrete used in construction and hydraulic projects. For this research, four mixtures containing different types of coarse aggregate in two different water environments were used. The utilized mixtures contained natural aggregate concrete (NAC) such as basalt and crushed marble. Also, recycled coarse aggregate concrete (RAC), which totally replaced natural aggregate, was presented in this paper such as crushed concrete and crushed ceramic. For this study, in the sieve analysis;specific and unit weights, was recorded. Furthermore, the mechanical properties were determined, using a compressive test that was conducted on the 7th, 28th, 56th and 90th days at different water environments;potable water (PW) and sea water (SW). Durability test was also performed for total absorption measurement. Results indicated that geopolymer concrete exhibits better strength in marine environments than in those of potable water. Results also showed that crushed marble (CMA) exhibits higher compressive strength and durability.

Experimental investigation of engineered geopolymer composite for structural strengthening against blast loads

The recent increase in blast/bombing incidents all over the world has pushed the development of effective strengthening approaches to enhance the blast resistance of existing civil infrastructures.Engineered geopolymer composite(EGC)is a promising material featured by eco-friendly,fast-setting and strain-hardening characteristics for emergent strengthening and construction.However,the fiber optimization for preparing EGC and its protective effect on structural elements under blast scenarios are uncertain.In this study,laboratory tests were firstly conducted to evaluate the effects of fiber types on the properties of EGC in terms of workability,dry shrinkage,and mechanical properties in compression,tension and flexure.The experimental results showed that EGC containing PE fiber exhibited suitable workability,acceptable dry shrinkage and superior mechanical properties compared with other types of fibers.After that,a series of field tests were carried out to evaluate the effectiveness of EGC retrofitting layer on the enhancement of blast performance of typical elements.The tests include autoclaved aerated concrete(AAC)masonry walls subjected to vented gas explosion,reinforced AAC panels subjected to TNT explosion and plain concrete slabs subjected to contact explosion.It was found that EGC could effectively enhance the blast resistance of structural elements in different scenarios.For AAC masonry walls and panels,with the existence of EGC,the integrity of specimens could be maintained,and their deflections and damage were significantly reduced.For plain concrete slabs,the EGC overlay could reduce the diameter and depth of the crater and spallation of specimens.

纯扭作用下地聚物混凝土梁静力性能试验研究

对地聚物混凝土梁纯扭性能进行了研究,以混凝土强度、纵筋配筋率和配箍率为研究参数设计并完成了6根地聚物混凝土梁和1根普通混凝土梁的纯扭试验。结果表明:当地聚物混凝土强度等级从C30提高到C70,试件开裂扭矩和极限扭矩分别提高了59.2%和12.9%,混凝土强度等级的增加显著提高了地聚物混凝土梁的开裂荷载,随着纵筋的增加和箍筋间距的减小,受扭裂缝出现的越细密,开裂后抗扭刚度越大,地聚物混凝土梁的裂缝发展和破坏模式与普通混凝土梁一致。开裂扭矩和极限扭矩值相比普通混凝土梁,分别提高了11.8%和2.93%。规范ACI 318—19的计算结果低估了地聚物混凝土梁的抗扭承载力,规范GB 50010—2010计算值与试验值吻合较好。

吐鲁浸膏中精油化学成分的GC-MS分析

利用挥发油提取器测定了吐鲁浸膏的精油含量 ,用GC -MS分析了浸膏精油的化学成分 ,鉴定出17种化合物 ,并采用GC峰面积归一化法定量 ,探讨了主要成分定量分析的重现性;该法简便、快捷 ,适用于工厂的浸膏类香料的质量监控和常规分析。

荷载-氯盐侵蚀耦合作用下矿渣基地质聚合物混凝土梁的受弯性能

地质聚合物混凝土因绿色低碳、高耐腐蚀受到广泛关注。本工作以矿渣为主要原材料,掺合粉煤灰和陶瓷粉制备了强度等级为C60的地质聚合物混凝土梁,分析其在荷载和氯盐侵蚀作用下的受弯性能。通过改变持荷大小和侵蚀时间,研究挠度、裂缝、应变以及氯离子渗透的变化。结果表明,在耦合作用下,地质聚合物混凝土力学性能变化曲线与普通硅酸盐水泥混凝土的规律具有高相似性,且抗弯和抗腐蚀性能高于同强度的普通硅酸盐混凝土。试验结果为地质聚合物在结构工程中的应用提供了数据支撑。

地聚物再生混凝土劈裂抗拉强度尺寸效应研究

研究地聚物再生混凝土(GRAC)劈裂抗拉强度的尺寸效应,探明其破坏机理和尺寸效应机理,提出劈裂抗拉强度尺寸效应计算方法,为GRAC材料和结构工程设计及推广应用提供参考。以试件边长分别为70.7 mm、100 mm、150 mm、200 mm的GRAC立方体试块进行劈裂抗拉强度试验;研究不同再生骨料取代率(0%、25%、50%、75%、100%)和不同水胶比(0.35、0.42、0.5)对地聚物再生混凝土劈裂抗拉强度尺寸效应的影响,并分析其微观机理。随着再生骨料取代率增大,GRAC劈裂抗拉强度不断降低,但其尺寸效应愈加明显;水胶比越小,试样开裂程度越大,脆性更大,尺寸效应更显著;Weibull的尺寸效应律更适用于GRAC劈裂抗拉强度,根据Weibull的尺寸效应律,得到了GRAC劈裂抗拉强度的临界尺寸和临界强度。GRAC相比于普通水泥混凝土劈裂抗拉强度的尺寸效应更加明显,可在工程实践中推广使用。

稻壳灰在建筑材料中的应用研究现状

作为农业大国,我国每年会产生大量的农业废弃物——稻壳灰(RHA)。RHA含有大量的非晶态二氧化硅,具有较强的火山灰活性,可作为辅助胶凝材料替代部分水泥,不仅能有效减少二氧化碳排放,还能实现RHA的资源化再生利用。大量研究表明,RHA能够显著改善水泥基材料的强度和微观结构,其多孔结构在水化反应体系中具有内养护效应,能够持续释放水分,促进水泥等材料的不断水化,从而表现出与硅灰等其他辅助胶凝材料不同的特性。综述了RHA的理化性质、活性影响因素及其在胶凝材料反应体系中的水化作用机理,并归纳了RHA在水泥混凝土、地质聚合物及土壤固化材料领域的应用研究现状,讨论了RHA对这些材料主要性能的影响,期望能推动RHA在建筑材料领域中的应用。

桂花浸膏香气成分的GC-MS分析

为了对桂花浸膏进行全成分分析以及评价主要香气成分对其香气特征的贡献,通过提取溶剂的优化,建立了用于桂花浸膏成分分析的二氯甲烷提取/GC-MS分析方法。借助双保留指数对桂花浸膏的成分进行定性分析,5个桂花浸膏样品共检测出121种化学成分,有26种成分在桂花浸膏分析研究的文献中未见报道。借助顶空固相微萃取筛选出14种桂花浸膏香气成分,通过香气活性值评价了香气成分对桂花浸膏香气特征的贡献,结果表明:芳樟醇、γ-癸内酯、α-紫罗兰酮、二氢-β-紫罗兰酮、β-紫罗兰酮、苯乙醇对桂花浸膏的总体香气特征贡献较大,是桂花浸膏的重要香气成分。

铁观音茶梗浸膏挥发性成分GC/MS分析及在卷烟中的应用

为开发新型天然烟用香料,采用同时蒸馏萃取法提取铁观音茶梗浸膏挥发性成分,用GC/MS法分离鉴定出58种挥发性成分,主要有(E)-橙花叔醇、(E)-香叶醇、芳樟醇及其氧化物、苯乙醇、脱氢芳樟醇、α-萜品醇、植酮、植醇、异植醇、棕榈酸、棕榈酸乙酯、亚油酸乙酯、亚麻酸乙酯和邻苯二甲酸二丁酯等。其中,芳樟醇、棕榈酸、植醇和(E)-橙花叔醇的含量最高,分别为13.27%,12.40%,7.74%和5.99%。将该浸膏用于卷烟加香,能够明显丰富烟香,减小刺激性和改善卷烟余味。

煤矸石在土木工程材料中的应用研究进展

煤矸石作为煤基固废系列的重要成员,其资源化利用一直是煤基固废的热点研究方向。多年来,在研究人员和工程技术人员的共同努力下,我国煤矸石资源化利用技术水平与利用效率均得到大幅提升,在多个领域(能源、化工、土木工程)成功实现了煤矸石“由废变宝”的转化过程。特别地,土木工程材料领域兼具“大体量”特点和“多元固废协同处置”等技术优势,成为大宗消纳煤矸石的中坚领域。本文综述了煤矸石作为胶凝材料/辅助胶凝材料和骨料在水泥混凝土、地质聚合物、道路工程及地下工程等方向的最新研究进展,总结并对比了煤矸石用作不同组分时的技术要点、难点及对应的质量控制措施和改性增强手段等。然而,矸石建材化的同时也容易导致矸石内部的“有价资源”未得到充分利用;矸石构筑物的长期耐久性和环境影响监测等工作也亟待补充。综上,受煤矸石理化性质、矸石资源化利用技术水平、经验及政策扶持力度等区域化差异因素的影响,煤矸石原料在用于多类型建材制品的生产过程中依然缺少因地制宜、明确且规范的分类管理和分级处置方法,“多领域技术-规范-政策”的逐步发展、完善和有机结合是今后建立高效有序的矸石建材市场及产业链的关键所在。

SDE/GC-MS法对两种不同葫芦巴浸膏香气成分的分析

生产过程中发现,Daniel公司的葫芦巴浸膏偏焦甜香气且较透发,而MAFCO公司的则偏膏甜香气且较沉闷。采用同时蒸馏萃取法与气相色谱质谱联用仪(GC／MS)对两种进口葫芦巴浸膏的香气成分进行了测试比较。结果表明,构成Daniel公司葫芦巴浸膏主要致香成分包括2-甲基-2-丁烯醛、3-羟基-2-丁酮、糠醛、2-氯环戊醇、棕榈酸乙酯、亚油酸乙酯、5-羟甲基糠醛等,而MAFCO公司则为糠醛、2-乙酰基呋喃、5-甲基糠醛等。同时发现,呋喃及其衍生物所占的比例很大,Daniel公司的葫芦巴浸膏所占比例为11.97％,MAFCO则更大,达到49.95％,这与已有文献结果存在明显的区别。

赖百当净油和浸膏挥发性成分的GC-MS分析研究

使用同时蒸馏萃取(SDE)和固相微萃取(SPME)方法对赖百当浸膏和明膏进行萃取浓缩,经气相色谱-质谱联用(GC-MS)分析对比,此外对进口和国产的赖百当净油采用直接进样的方法进行对比分析,得出它们的主要成分为3-苯丙酸乙酯(氢化肉桂酸乙酯)和降龙涎香醚,分别提供木香香气和龙涎香、琥珀香气。

HS-SPME-GC-MS法分析西梅浸膏挥发性成分

为研究西梅浸膏中挥发性成分的种类及相对含量,采用固相微萃取对西梅浸膏中挥发性成分进行富集提取,利用气相色谱-质谱联用法进行定性、定量分析,共鉴定出20种成分,其主要成分为5-羟甲基糠醛和苯乙酸庚酯,相对质量分数分别为13.96%和6.30%。