Effect of Curing Conditions on the Hydration and Performance of CFBC Ash Cementitious System

Circulating fluidized bed combustion （CFBC） ash can be used as supplementary cementitious material for concrete production for its high pozzolanic activity. We investigated the effect of curing conditions on the hydration and performance of CFBC ash-Portland cement system （30： 70, by mass） including hydration products, paste microstructure, linear expansion ratio, chemically combined water content and compressive strength. The results show that tobermorite rather than ettringite is generated under the condition of autoclaved curing. The expansion and mortar strength of the system cured in water is higher than those cured in air at a given age, and the strength and bulk volume may retract under the condition of air curing. In addition, autoclaved curing facilitates the increase of strength gain at early curing ages （the increase rate lowers down in the following ages） and the improvement of system volume stability. It is suggested that sufficient water is necessary for the curing of CFBC ash cementitious system, and autoclaved curing may be considered where volume stability is a primary concern.

Influence of Curing Condition on the Adhesive Strength of EVA Modified Mortar to Tile

The reducing water effectiveness of EVA latex and powder was observed. Adhesive strength of EVA modified mortar to tile under different curing condition was studied. And the adhesive strengths of mortars modified by EVA latex and by EVA powder were compared. The results show that the reducing water effectiveness is improved by 36.12% and 21.55%, respectively, when the content of EVA latex and powder are 8% and 4%. EVA latex and powder can improve the adhesive strength of modified mortar to tile under the standard curing, high temperature curing, and freeze-thaw circle curing. EVA latex can improve the water resistance obviously, besides improve the adhesive strengths of standard curing and high temperature curing, comparing with EVA powder.

Effects of Curing Conditions on Strength Development of High Strength Concrete

This paper presents the results of a series of studies on the influence of curing conditions on the strength development of high strength concrete. The 1-, 3-, 7-, 14- and 28-day strengths of four different mixes of Grade 75 similar to 80 concrete, with or without pulverized fuel ash and/or condensed silica fume, under five different curing regimes were investigated. It is revealed that the curing conditions have significant influence on both the short term and long term strength development of the concrete and that concrete mixes of the same grade but containing different mineral admixtures show distinct favour for a curing regime. These results will be helpful for evaluating suitable curing methods for high strength concrete with different mix proportions.

Influence of subsequent curing on water sorptivity and pore structure of steam-cured concrete

Steam-cured condition is found to cause larger porosity and worse properties of concrete compared with normal curing condition. For the sake of seeking effective measurements to eliminate this bad effect of steam-cured condition on concrete, the water sorptivity and pore structure of steam-cured concretes exposed to different subsequent curing conditions were investigated after steam-curing treatment. The capillary absorption coefficient and porosity of the corresponding concretes were analyzed, and their mechanisms were also discussed. The results indicate that water sorptivity and pore structure of steam-cured concrete are greatly influenced by the curing condition used in subsequent ages. Exposure steam-cured concrete to air condition has an obviously bad effect on its properties and microstructures. Adopting subsequent curing of immersing steam-cured concrete into about 20℃ water after steam curing period can significantly decrease its capillary absorption coefficient and porosity. Steam-cured concrete with 7 d water curing has minimum capillary absorption coefficient and total porosity. Its water sorptivity is decreased by 23% compared with standard curing concrete and the porosity is 9.6% lower. Moreover, the corresponding gradient of water sorptivity and porosity of steam-cured concrete both decrease, thus mictostructure of concrete becomes more homogeneous.

Transcriptome and genome analysis to identify C2H2 genes participating in low-temperature conditioning-alleviated postharvest chilling injury of peach fruit

Objectives:This work intended to identify candidate C2H2 genes participating in low-temperature conditioning(LTC)-alleviated postharvest chilling injury of peach fruit.Materials and Methods:For LTC treatment,fruit were pre-stored at 10℃for 5 d and then transferred to 0℃storage.Fruit firmness was measured by a hardness tester.H_(2)O_(2)content was determined by luminosity measurement model using a multifunctional enzyme labeler.Identification of C2H2 family members was performed by HMMSCAN according to peach genome.The cis-acting element of gene promoters was analyzed using the Plant CARE website.Weighted gene coexpression network analysis(WGCNA)was performed by the WGCNA package in the BMK Cloud platform.Results:LTC treatment decreased flesh browning rate and H_(2)O_(2)production of‘Beijing No.9’peach.Transcription factor identification of differentially expressed genes in 0℃and the LTC treatment indicated that peach C2H2 participated in the regulation of chilling injury.A total of 47 C2H2 genes were identified based on peach genome.Real-time quantitative polymerase chain reaction(qRT-PCR),phylogenetic analysis and promoter cis-acting element analysis revealed that ZFP21 was involved in the regulation of LTC-alleviated chilling injury in peach.WGCNA and dual luciferase assay suggested that ZFP21 participated in LTC-alleviated chilling injury by downregulating the expression of reactive oxygen species-related genes Rboh.Conclusions:Our investigation,based on genome and RNA-seq,revealed that ZFP21 was involved in LTC treatment-alleviated chilling injury of peach fruit.This work is useful for the identification of peach cold tolerance-related genes and the study of C2H2 family in peach.

Effect of High Temperature Curing on the Frost Resistance of Recycled Aggregate Concrete and the Physical Properties of Second-Generation Recycled Coarse Aggregate under Freeze-Thaw Cycles

With the emphasis on environmental issues,the recycling of waste concrete,even recycled concrete,has become a hot spot in the field of architecture.But the repeated recycling of waste concrete used in harsh environments is still a complex problem.This paper discusses the durability and recyclability of recycled aggregate concrete(RAC)as a prefabricated material in the harsh environment,the effect of high-temperature curing(60℃,80℃,and 100℃)on the frost resistance of RAC and physical properties of the second generation recycled coarse aggregate(RCA_(2))of RAC after 300 freeze-thaw cycles were studied.The frost resistance of RAC was characterized by compressive strength,relative dynamic elastic modulus,and mass loss.As the physical properties of RCA_(2),the apparent density,water absorption,and crushing value were measured.And the SEM images of RAC after 300 freeze-thaw cycles were shown.The results indicated that the frost resistance of RAC cured at 80℃ for 7 days was comparable to that cured in the standard condition(cured for 28 days at 20℃±2℃ and 95%humidity),and the RAC cured at 100℃ was slightly worse.However,the frost resistance of RAC cured at 60℃ deteriorated seriously.The RAC cured at 80℃ for 7 days is the best.Whether after the freeze-thaw cycle or not,the RCA that curd at 60℃,80℃,and 100℃ for 7 days can also meet the requirements of Grade III RCA and be used as the aggregate of non-bearing part of prefabricated concrete components.RCA_(2) which is cured at 80℃ for 7 days had the best physical properties.

Hydration evolution of pre-cast concrete with steam and water curing

The hydration characteristics of pre-cast concrete considering the effects of effective initial steam-curing and water-curing duration were measured and analyzed with XRD, TG, X-ray CT, SEM-BSE and MIP techniques. The results show that the effective initial steam-curing duration for pre-cast concrete with lower water-binder ratio was 10 14 h at 50 °C and the initial water-curing duration was 7 14 d. And the hydration evolution of cement, fly ash and slag in pre-cast concrete was obtained respectively by combining the hydrochlorides and EDTA selecting dissolution methods, based on which the contents of hydrated and anhydrate in concrete were calculated and the corresponding dynamic capillary porosity was also determined. Moreover, the comparison between calculated results and experimental ones indicates that the proposed evolution models of microscopic characteristics corresponding to hydration kinetics of cemented materials could be adopted to predict the developing trend of capillary porosity and hydration-products content in pre-cast concrete with fly ash and slag under certain curing conditions.

养护条件对风积砂混凝土强度及孔隙发展规律的影响

养护条件在混凝土强度发展过程中起到了重要作用,为了研究其对风积砂混凝土性能的影响,进行了立方体抗压试验确定最优风积砂替代率,在此基础上通过核磁共振试验,讨论自然养护、标准养护、水养护三种条件下混凝土微观结构发展规律。结果表明:混凝土较优风积砂替代率为20%,此时抗压强度达到最大;不同养护条件下风积砂混凝土抗压强度规律为:水养护>标准养护>自然养护;水养护与标准养护条件下风积砂混凝土T2图谱随养护龄期的增加逐渐向左移动,无害孔占比较高,但自然养护条件下,有害孔占比较高,不利于提高抗压强度;相较于标准养护,水养护条件下混凝土峰结束位置较早,平均孔径减小,无害孔占比增加。

抗氧化剂对富氮气调散气后片烟储存质量的影响

利用3种不同抗氧化剂的高、低2种浓度分别作用于片烟,探究富氮气调养护片烟在散气后的品质变化。以持续富氮气调养护28个月的云南文山C3F复烤片烟为试验材料,分析碘值、pH、色差值、多酚氧化酶活性的变化情况。不同处理组对减缓自然放置3个月的烟叶碘值增幅的效果为Ve-环糊精复合物处理>富氮气调处理>0.75 g/L Ve>0.75 g/L Vc>0.075 g/L Vc/0.075 g/L Ve。自然放置6个月后高浓度的Ve和Vc处理效果最佳。Ve-环糊精复合物处理下样品的pH下降速度最慢,对样品的原pH维持效果最佳。低、高浓度的Ve和高浓度Vc、Ve-环糊精复合物的处理均可提升散气后自然放置6个月内的烟叶的色度。自然放置6个月后,高浓度的Ve处理下多酚氧化酶的活性最低。3种抗氧化剂均能有效延缓富氮气调储存烟叶散气后自然放置状态下的性质变化,且高浓度的Ve对烟叶感官评价结果的影响最小。

单组分耐高温糊状胶粘剂的固化工艺研究

以J-481单组分耐高温糊状胶粘剂为研究对象,采用差示扫描量热分析仪检测了J-481胶粘剂的放热曲线。利用流变仪考察了胶样的黏-温曲线和不同升温工艺下的黏-时特性,分析了不同固化工艺下胶接试样的粘接强度、不同胶层厚度的胶粘剂在不同固化工艺下固化后的实物状态。研究结果表明:J-481胶粘剂的黏度、固化程度和粘接性能受固化机制影响明显,升温过快造成黏度增长迅速、热量积聚引起厚胶层试样爆聚烧蚀,固化温度不足则导致粘接强度下降。采用120℃/3 h+180℃/1 h梯度升温固化,所有厚度(0.3~5 mm)的试样均可以正常固化,未出现爆聚烧蚀现象,更适合实际工况的应用。对比120℃/3 h+180℃/1 h和180℃/3 h两种固化条件下的固化度以及粘接不同基材的粘接强度,发现采用120℃/3 h+180℃/1 h梯度升温固化机制,能够确保J-481胶粘剂粘接不同基材均达到优异稳定的粘接性能。

养护条件对混凝土力学性能及抗硫酸盐侵蚀性能的影响

针对新疆盐渍环境及高温干旱气候条件下混凝土普遍存在的硫酸盐侵蚀问题,研究了不同养护条件[标准养护、自然条件下内养护、(40±2)℃恒温内养护]对混凝土力学及抗硫酸盐侵蚀性能的影响,进行了混凝土的抗压强度、干湿循环硫酸盐侵蚀试验,计算了质量损失率及耐蚀系数。结果表明:SAP内养护可以在一定程度上改善混凝土的抗压强度,且可以延缓干湿循环硫酸盐侵蚀对混凝土的腐蚀破坏;混凝土的耐蚀系数与质量损失率之间有显著的负相关性,随着耐蚀系数的降低,混凝土的质量损失率增加。

二氧化碳养护水泥基材料的研究进展

水泥基材料通过碳化反应可以快速形成以碳酸盐和高聚度硅胶为主要产物的固碳制品。固碳制品因其可以兼顾CO_(2)消纳能力与优良的力学性能受到了广泛的关注。国内外研究团队在原材料开发、组成与工艺优化、养护制度设计等基础上,开发了多种应用场景,主要包括板材、小型砌块、骨料等。从碳化反应机理与动力学出发,归纳了反应条件对结构与产物组成的影响规律,总结了现有制品的种类、性能与应用现状,以期为建材工业的碳减排提供新的思路。

基于无侧限抗压强度试验的不同养护环境对水泥土强度影响研究

以福建省宁德市连城路(疏港路-学院路段)道路工程项目为依托,采用无侧限抗压强度试验系统研究了不同养护条件、不同水泥掺量、不同养护龄期对水泥土强度的影响。结果表明:当水泥掺量和养护龄期均相同时,试验箱中水泥土的无侧限抗压强度均小于标养箱;在同一水泥掺量下,试验箱和标养箱中水泥土的无侧限抗压强度均与养护龄期成正相关,即随着养护龄期的增加而增长,但其强度增长幅度随着养护龄期的增加逐渐降低;同一养护龄期下,不同养护条件下水泥土的无侧限抗压强度均随着水泥掺量的增加而增长,且试验箱和标养箱中试样的强度差值随着水泥掺量的增加逐渐加快。

LNG底板大体积混凝土温度裂缝控制方法研究

基于深圳某下沉式LNG储罐基坑及相关地下结构工程,通过实测温度数据和数值模拟结果分析了不同浇筑方式和不同养护条件等因素对大体积混凝土温度、应力的影响及其变化规律,并分析了对工程最高温度、最大温升等规范要求参数的影响,验证了该基坑底板工程的大体积混凝土温度控制方法的有效性。

低介质损耗乙烯基树脂材料的制备与性能

使用双酚A(BPA)和4-乙烯基苄氯(VBC)为原料合成一种双酚A型乙烯基苄基醚(VLBPA)树脂,采用高效液相色谱、红外光谱分析和核磁共振氢谱表征方法,确定了产物结构,探究了产物的最优合成条件。在145℃/1.5 h+175℃/2 h+210℃/4h固化条件下制备VLBPA固化物,并测试了其热学性能和介电性能。结果表明,产物的最优合成条件为:n(BPA)∶n(VBC)∶n(NaOH)=1.0∶2.8∶2.4,反应时间7 h,该条件下产物产率可达到92.76%。差示扫描量热(DSC)分析结果表明,VLBPA在117.7℃时存在融化的吸热峰,在156.3℃时存在乙烯基的交联放热峰。树脂固化物在N_2气氛下5%热失重温度(T_(5%))达到了400.5℃,具有良好的热稳定性能;在频率10 GHz下,介电常数(D_k)为2.79,介质损耗(D_f)为0.006 5。

养生条件对掺粉煤灰水泥乳化沥青砂浆收缩及黏弹性能的影响

水泥乳化沥青砂浆(CA砂浆)性能易受到养生环境和原材料组成的影响,通过设置的5组养生条件和3种配合比进行CA砂浆收缩率和动态黏弹性能的测试,并采用扫描电镜观察其微观形貌。结果表明:掺加粉煤灰会适当增大CA砂浆的膨胀率,不同养生湿度下砂浆体积变化趋势不同,增大沥灰比、升高养生温度均可改善CA砂浆的体积稳定性;掺粉煤灰CA砂浆的储能模量和损耗模量均随养生温度升高而增大,表现为砂浆刚度提高,变形时内部摩擦力做功增加;掺加粉煤灰能够改善CA砂浆的黏弹性能,其低温抗开裂性、高温抵抗变形能力均有所增强;20℃干养下粉煤灰CA砂浆黏弹性能最优;综合收缩性能和黏弹性能,20℃干养下沥灰比为1.4的粉煤灰CA砂浆性能较优。微观形貌观察的结果显示掺加粉煤灰后CA砂浆沥青膜增厚、孔隙率降低、结构更加致密,这是掺加粉煤灰CA砂浆体积稳定性和黏弹性得以改善的主要原因。

Effect of curing condition on bonding quality of scarf-repaired composite laminates

Both single-face vacuum bag curing(SVC) and double-face vacuum bag curing(DVC)can be used in scarf repair of composite structures. But different curing conditions caused by the sealing state may affect the bonding quality of scarf-repaired structures. In this paper, the effect of curing condition on bonding quality of scarf-repaired laminates was experimentally investigated in terms of surface profiles, moisture absorption curves and section profiles. In order to further explore the moisture absorption mechanism, finite element model of the repaired laminates using DVC was established with moisture diffusion of both the adhesive and composite laminates considered. This model was verified by experimental results. Based on the model of DVC case, the model of SVC case was built by changing moisture absorption parameters of the adhesive. Results show that SVC reduces the bonding quality, mainly reflecting in more adhesive inner voids and patch-toparent dislocation. And SVC increases moisture absorption rate and moisture equilibrium content of the adhesive, and its effect on the former is far greater than that on the latter.

Low-temperature-curable and photo-patternable benzocyclobutene-derived aggregation-induced emission-active polymer dielectrics

The high curing temperatures required for traditional benzocyclobutene(BCB)materials have posed limitations on their applicability in high-temperature-sensitivefields.To address this challenge,our work focuses on the synthesis of a novel tetraphenylethylene(TPE)-functionalized BCB monomer,TPE–BCB,achieved through the introduction of an ether bond onto the BCB’s four-membered ring via Williamson reaction.TPE–BCB demonstrates remarkable low-temperature curing properties,characterized by a ring-opening peak temperature of 190◦C,representing a reduction of 60◦C compared to conventional BCBs.Fully cured TPE–BCB resins exhibit exceptional dielectric and mechanical properties,coupled with minimal water absorption.Additionally,the incorporation of TPE with aggregation-induced emission characteristics enhances the resins’luminescence and photolithographic capabilities.Notably,our TPE–BCB resins achieve impressive photolithography performance with a resolution ratio of up to 10μm.In contrast to conventional BCB-functionalized resins,TPE–BCB offers the dual advantage of low-temperature curing and luminescence.This development marks a significant step in the advance-ment of low-temperature curing BCB materials and serves as a pioneering example in the realm of multilayer wafer bonding materials.

养护制度对掺MgO膨胀剂混凝土力学性能的影响研究

研究了不同掺量MgO膨胀剂在自然养护、标准养护、限制养护和高温养护条件下对混凝土力学性能的影响,结果表明:随着MgO膨胀剂掺量增大,各养护条件下,混凝土抗压强度均逐渐降低;不同养护条件对混凝土强度影响明显,高温养护下强度发展最快,自然养护下,强度发展最慢;对于C30混凝土,掺20 kg MgO膨胀剂对混凝土强度无明显负面影响;掺MgO膨胀剂混凝土长龄期抗压强度无倒缩现象。

Properties of high cis-1,4 content hydroxyl-terminated polybutadiene and its application in composite solid propellants

In this paper,high cis-1,4 content hydroxyl-terminated polybutadiene(cis-HTPB)with different molecular weights was prepared through the oxidative cracking process using cis-butadiene rubber as raw material.Firstly,this article comprehensively compared the differences between cis-HTPB and conventional I-HTPB in terms of molecular weight distribution,functionality,viscosity,molecular polarity,and other physicochemical properties,which provided effective data support for its subsequent application.In addition,the reaction kinetics study showed that cis-HTPB with isocyanate curing agent has high reactivity,allowing it to be rapidly cured at low temperatures,and the cured elastomers had excellent mechanical properties,with tensile strength and elongation up to 1.89 MPa and 1100%,respectively.It was also found that cis-HTPB has extremely excellent low-temperature resistance,and the glass transition temperature(T_(g))of its cured elastomer is as low as-101℃.Based on the above studies,cis-HTPB is applied as a binder in composite solid propellants for the first time to investigate its practical performance,and the results indicated that cis-HTPB-based propellants have excellent process and mechanical properties.