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.

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.

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。

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。

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.

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。

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.

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%。

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.

Concrete Based on Fly Ash Alumosilicate Polymers

Concretes on the basis of the alumosilicate polymer can be prepared by alkali activation （NaOH, sodium water glass） of waste brown coal fly ash. The preparation is possible： （1） by using a short-term heating of the concrete mix （to 80 ℃）; or （2） by allowing the mix to harden spontaneously at a temperature of 20 ℃. The concretes prepared by short-time heating attain high strength values after their preparation; the values are comparable to those characterizing concretes obtained on the basis of Portland cement. The strength development of concretes hardening at 20 ℃ is substantially less steep but, nevertheless, the strength attained after about 60 days is practically identical with that of the concretes exposed to a short-time heating. The shrinkage of concretes prepared by short-time heating is very small as compared with the concretes allowed to harden spontaneously; the shrinkage of latter concretes is larger than that of the concretes on the basis of Portland cement. The concretes on the basis of alumosilicate polymer exhibit much better resistance to the corrosive action of the environment as compared with those prepared on the basis of Portland cement.

Effective Contribution of Brazilian Rice Husk Silica(RHS)as Eco-Friendly Silica in Concrete Plants

Due to growing consumption of Portland cement and high levels of CO_(2) emissions in its production process,this study examined the use of Brazilian RHS(rice husk silica)obtained by FBC(fluidized bed combustion)as an alternative material in concrete production;the principal cause is the inappropriate disposal of carbonized or in natura rice husk in southern Brazil.To analyze its feasibility,concretes made with several types of cements were examined combined with RHS,and also concretes with different strength classes employing a slag-based binder featuring a smaller amount of clinker in its composition.Mechanical and scanning electron microscopy assays were carried out to verify formation of C-S-H and calcium hydroxide in the cement pastes.This study concludes that replacing 10%of Portland cement(CEMIII/A)by 3%of RHS can result in a cost reduction of around 5%and allows a reduction of 4%in CO_(2)eq levels.In this way,RHS from renewable sources can be a highly impactful sustainable alternative in civil engineering work,allowing the concrete industry to produce environmentally-sound concrete mixtures with lower CO_(2) emissions.

UTILIZATION OF FLY ASH AND CONCRETE RESIDUE IN THE PRODUCTION OF GEOPOLYMER BRICKS

This study presents the development of geopolymer bricks synthetized from industrial waste,including fly ash mixed with concrete residue containing aluminosilicate compound.The above two ingredients are mixed according to five ratios:100:0,95:5,90:10,85:15,and 80:20.The mixture’s physico-mechanical properties,in terms of water absorption and the compressive strength of the geopolymer bricks,are investigated according to the TIS 168-2546 standard.Scanning electron microscopy(SEM)and X-ray diffraction(XRD)analyses are used to investigate the microstructure and the elemental and phase composition of the brick specimens.The results indicate that the combination of fly ash and concrete residue represents a suitable approach to brick production,as required by the TIS 168–2546 standard.

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.

地质聚合物混凝土的冲击力学性能研究

以矿渣与粉煤灰为原材料,制备地质聚合物混凝土(geopolymeric concrete,GC)。采用Φ100 mm分离式霍普金森压杆(split Hopkinson pressure bar,SHPB)装置研究了不同强度等级的GC的冲击力学性能,包括抗压强度、变形及能量吸收特性的应变率效应问题。结果表明:GC的冲击力学性能呈现出显著的应变率相关性,强度的应变率敏感值为42.7 s—1;随着强度等级的提高,GC的变形能力反而降低。GC属于准脆性材料,相对于单一的强度或变形特性,GC的能量吸收特性更值得关注。

矿渣-粉煤灰基地质聚合物混凝土的基本性能研究

地质聚合物混凝土是一种新型混凝土类材料。为了研究地质聚合物混凝土的基本性能,以矿渣、粉煤灰为原料,以硅酸钠和氢氧化钠为激发剂,制备了矿渣-粉煤灰基地质聚合物混凝土,测试了不同配合比下矿渣-粉煤灰基地质聚合物混凝土的坍落度以及7、14 d和28 d的抗压强度,分析了水胶比对和易性与抗压强度的影响,探讨了抗压强度的增长规律。结果表明:制备的矿渣-粉煤灰基地质聚合物混凝土具有较高的抗压强度和良好的和易性,凝结硬化快,强度特性稳定;当水胶比为0.26,砂率为0.40,氢氧化钠和硅酸钠的质量比为0.29,碱溶液的浓度为56%时,矿渣-粉煤灰基地质聚合物混凝土的坍落度为110 mm,标准养护条件下7、14 d和28 d龄期的抗压强度分别达到40.4、50.3 MPa和60.20 MPa;随着水胶比的增大,和易性不断增强,抗压强度先增加,后减小;随着养护龄期的延长,抗压强度不断增长,但增速降低。

高温后地质聚合物混凝土声谱特性的小波包分析

制备了矿渣粉煤灰基地质聚合物混凝土(SFGC),通过抗压强度试验及超声波检测,研究了不同温度、不同冷却方式下SFGC强度及波速的变化规律,并运用小波包变换方法对所得声波测试信号进行分析.结果表明:利用小波包分析技术可以准确、清晰地反映出不同工况下SFGC声谱特征的变化规律;随着温度的升高以及试件损伤的演化发展,其强度、波速不断减小,各子频带内的功率谱及能量显著改变,频谱及能量谱中心向低频端移动;喷水冷却后SFGC的力学、声学特性较自然冷却情况变化更为明显;基于小波包变换的声谱特征参数对高温损伤的敏感性较好,可用以判别SFGC的工况类型及损伤程度.