胶凝材料体系对透水混凝土性能的影响

选取了水泥(Cement,C)、水泥-粉煤灰(Cement-Fly ash,C-FA)、水泥-硅灰(Cement-Silica fume,C-SF)和碱激发粉煤灰矿渣胶凝材料(Alkali-activated Fly ash-Slag,AA-FA-SL)四种胶凝材料体系制备了透水混凝土,并研究了不同胶凝材料体系对透水混凝土抗压强度、透水性能及耐酸雨侵蚀性能的影响.结果 表明:C体系透水混凝土透水性能较好,但抗压强度和耐酸雨侵蚀性需进一步提高;C-FA体系透水混凝土具有较好的耐酸雨侵蚀性能,但抗压强度偏低;C-SF体系和AA-FA-SL体系透水混凝土均有合适的抗压强度和耐酸雨侵蚀性能,虽然透水性能略低于C体系透水混凝土但仍能满足工程排水需求;综合考虑使用性能、经济成本以及社会环境效益,制备高性能透水混凝土可优先选用AA-FA-SL胶凝体系.     

PVC/秸秆类纤维复合材料性能

为比较不同秸秆类(芦苇秸秆、稻秸秆、麦秸秆)纤维对其制备复合材料性能的影响,以芦苇秸秆、稻秸秆、麦秸秆为填充材料,以聚氯乙烯(PVC)为基体材料,采用挤出成型工艺制备3种PVC/秸秆类纤维复合材料。对3种秸秆纤维进行了成分分析,对它们制备的复合材料进行了力学性能和吸水性能测试,并对3种复合材料进行了FTIR分析,用SEM观察了复合材料拉伸断面微观结构。结果表明,3种秸秆类纤维中,芦苇秸秆的纤维素、半纤维素和木质素含量最高,其制备的PVC复合材料结合界面和力学性能最佳,PVC/芦苇秸秆纤维复合材料拉伸、弯曲和冲击强度分别为36.79 MPa,67.19 MPa和7.01 k J/m2,比PVC/麦秸秆纤维复合材料分别提高了104.62%,89.7%,99.72%。3种PVC/秸秆类纤维复合材料中PVC/芦苇秸秆纤维复合材料24 h吸水率最低,比PVC/麦秸秆纤维复合材料降低67.36%。     

聚丙烯/麦秸秆木塑复合材料的力学性能

采用转矩流变仪混合造粒,通过注射成型方法制备了聚丙烯(PP)/麦秸秆木塑复合材料,研究了NaOH浓度、增容剂的含量和麦秸秆含量对PP/麦秸秆木塑复合材料力学性能的影响,采用扫描电子显微镜对麦秸秆表面及复合材料的断面形貌进行分析。结果表明:8%NaOH溶液处理麦秸秆时,PP/麦秸秆木塑复合材料的拉伸强度、弯曲强度和冲击强度达到最大;马来酸酐接枝PP增容剂的加入使得麦秸秆与PP的界面相容性提高,复合材料的力学性能增加;在一定范围内麦秸秆的添加降低了PP材料的拉伸强度和冲击强度,而提高了其弯曲强度,并且PP/麦秸秆复合材料的弯曲强度随着麦秸秆含量的增加而增加,在麦秸秆含量为30%时弯曲强度达到最大值为43.4 MPa。     

模压压力和温度对PE/麦秸秆发泡复合材料的影响

为探讨模压压力和温度对聚乙烯(PE)/麦秸秆发泡复合材料微观结构和性能的影响,以偶氮二甲酰胺(AC)为发泡剂模压制备PE/麦秸秆发泡复合材料,对比研究模压压力和温度对PE/麦秸秆发泡复合材料热导率、表观密度和吸水性能的影响,用体视显微镜观察材料的断面微观形貌,用傅立叶变换红外光谱分析探讨复合材料的化学结构。结果表明,当模压压力为10 MPa,模压温度为150℃时,PE/麦秸秆发泡复合材料内部泡孔结构均匀,热导率、表观密度和吸水率较小,麦秸秆和PE的界面结合较好,材料较致密。     

纳米秸秆灰对多孔混凝土路面力学性能的影响

本文主要研究了掺加纳米秸秆灰后对多孔混凝土路面性能的影响。根据抗压强度，弯曲强度和抗拉强度来测试多孔混凝土。结果表明，使用纳米秸秆灰材料极大提高了多孔混凝土路面的力学性能，其中纳米秸秆灰以10％质量分数替代水泥制备的多孔混凝土与其它比例制备的样品相比，表现出更加优异的强度；并且测试发现纳米秸秆灰多孔混凝土路面的抗压强度，弯曲强度和抗拉强度随着养护时间的增加而增加。     

复合掺配生土改性试验及抗压性能分析

为了推动工业固体废弃物综合利用，改善传统生土材料的力学性能，通过在生土材料中添加煤矸石粉、矿粉、石灰、粉煤灰和麦秸秆灰等5种材料复合掺料进行生土改性试验，依据《土工试验方法标准》(GBT 50123—2019)制备了96个Φ102 mm×116 mm的圆柱体试样，在室内养护28 d后不烘和烘干2种状态下进行轴心抗压试验，得到改性生土试件的荷载-位移关系，分析了复合材料对改性生土抗压强度的影响规律和复合掺料的最优配比。结果表明：煤矸石粉、矿粉、石灰、粉煤灰和秸秆灰掺量分别为0%、8%、6%、8%和2%时，复合材料改性生土试样的28 d抗压强度最大，2种状态下分别达到了3.07、5.07 MPa,与同养护条件的素土试样相比，其分别是其抗压强度的1.71、1.77倍。     

长英质尾矿制备透水路面砖研究

介绍了透水砖的发展前景,利用矿物聚合机理以粉煤灰和长英质尾矿为主要原料制备出一种免烧路面透水砖,同时研究了砂灰比和骨料粒径对透水砖的影响.结果表明:随着骨料粒径增大,制品的透水系数增大,劈裂抗拉强度和抗折强度减小;随着砂灰比增大,制品的透水系数增大,劈裂抗拉强度和抗折强度随之减小.并对透水砖结构模型和机理做了探讨,发现砂灰比会影响制品的有效空隙,进而影响制品的透水性能.     

三种植物纤维填充聚乳酸复合材料性能对比

为充分利用农作物植物资源,以稻秸秆、麦秸秆、稻壳三种植物纤维为填充相,聚乳酸(PLA)为基体,制备了PLA/植物纤维复合材料。对三种植物纤维的成分进行了对比分析,并对制备的复合材料的力学性能和吸水性能进行了比较,分析了三种复合材料的热重曲线、差示扫描量热曲线与红外光谱,并用扫描电子显微镜观察了复合材料的断面微观结构。结果表明,三种植物纤维材料中稻秸秆的纤维素与半纤维素总含量最高,稻秸秆制备的PLA复合材料力学性能与界面结合性最好,其弯曲强度为28 MPa,分别比麦秸秆和稻壳制备的PLA复合材料高75%和47%;PLA/稻壳复合材料的吸水率最小,比PLA/稻秸秆和PLA/麦秸秆分别小10%与25%;三种植物纤维改性PLA复合材料的热分解曲线基本相同,PLA/稻壳复合材料的热稳定性相对最好。     

麦秸秆开发利用的新技术

报道了利用麦秸秆生产一次性卫生餐盒、一次性卫生筷子的工艺技术,介绍了以麦秸秆为原料,通过酶解产糖并发酵制备乙醇的工艺研究。     

秸秆灰利用的研究进展

生物质热化学转化过程中产生的秸秆灰已逐渐成为经济和环境的负担。随着生物质热化学转化技术的进一步发展,秸秆灰的利用问题逐步凸显。基于秸秆灰的特性,秸秆灰能制备很多的化学产品;能应用在建筑工业中;作为一种主要的吸附剂能去除很多污染物,尤其是在经过物理和化学活化后吸附效果更显著;由于秸秆灰的基本矿物元素与土壤相近,经过处理后,还能作为农业肥料使用。本文还介绍了秸秆灰在化学工业、建筑材料、环境管理及农业领域的更进一步的研究情况。     

渗透结晶材料对混凝土裂缝自愈合的影响

通过在纯水泥混凝土和粉煤灰、矿粉混凝土中掺入渗透结晶材料制备不同混凝土,同时制备基准混凝土,分别采用裂缝深度观测、强度恢复测试、抗渗恢复测试研究渗透结晶材料对混凝土裂缝自愈合的影响,并采用SEM-EDS分析愈合产物.试验结果表明,渗透结晶材料可以显著改善混凝土的裂缝自愈合效果,降低开裂混凝土裂缝深度,提高混凝土强度恢复率和抗渗恢复率.对于掺渗透结晶材料的粉煤灰、矿粉混凝土,裂缝自愈合效果更优.渗透结晶材料促进了水化硅铝酸钙在裂缝处的生成和富集,从而起到促进裂缝自愈合的作用.     

麦秸增强脱硫石膏-粉煤灰砌块的研究

以脱硫石膏和粉煤灰作为基料,麦秸为增强材料,添加适宜的粉煤灰激发剂、防水剂及其他助剂,用合理的生产工艺制备出麦秸增强脱硫石膏-粉煤灰砌块.对砌块的原料配比、防水性能进行了试验研究,通过化学成分分析、扫描电镜分析等测试手段对基料组成、砌块微观形貌进行了分析.     

废弃烧结砖骨料制备渗蓄生态材料研究

从海绵城市建设理念着手,采用不同粒级的建筑垃圾废弃烧结砖为骨料,农业废弃物谷壳灰为填充料,研究骨料粒级、原料配合比、填充料掺量等对废弃烧结砖骨料蓄水透水材料的吸水率、渗透系数和抗压强度的影响,得到蓄水性好、透水性高、强度较大的渗蓄生态材料的优化配比.研究结果表明:骨料粒级为2.36~4.75 mm时,通过优化配比设计,材料的吸水率可达24.3%,渗透系数达5 cm/s,强度约为8 MPa;通过掺入约35 kg/m3的谷壳灰,可使渗蓄生态材料的吸水率达到30%,提高6%,渗透系数≥4 cm/s,强度≥5 MPa.该材料可用于海绵城市建设及堤岸护坡工程.     

秸秆灰对煤焦气化反应性的影响

钾、钙对煤焦气化反应性具有重要影响,秸秆灰中含有丰富的钾、钙。以神木煤为制焦原料,通过STA409PC同步热分析仪研究了秸秆灰对煤焦气化反应性的影响,并通过测定煤焦的碘吸附值对其比表面积及孔隙结构进行了分析。结果表明：煤与玉米秸秆共焦化所得煤焦的气化反应性明显优于单独煤焦,且与玉米秸秆的添加比例有关;采用脱灰玉米秸秆与煤共焦化所得煤焦的气化反应性与单纯煤焦相近;将与玉米秸秆等效的秸秆灰添加到煤焦中,煤焦的气化效果明显优于等效玉米秸秆与煤共焦化所得煤焦。煤焦碘吸附值测定结果表明,脱灰秸秆与煤共焦化所得煤焦的碘吸附值最大,单纯煤焦的碘吸附值最小,说明玉米秸秆及秸秆灰对煤焦的比表面积及孔隙结构具有重要的影响,与煤焦的气化反应性评价结果基本一致。     

生物质与煤混合灰的熔融及黏温特性

使用灰熔点测试仪研究了稻草、玉米秸秆、棉秆3种生物质分别掺入不同比例对鲍店煤灰熔融特性的影响,并利用高温黏度计考察了3种生物质掺入比例均为10%时对鲍店煤灰黏温特性的影响。结合X射线衍射仪分析测试结果,采用热力学计算软件FactSage得到了不同温度下灰渣熔融过程中物相及渣液内固含量的变化。结果表明：3种生物质掺混比例为10%～30%时,混合灰灰熔点均随生物质掺混比例的增加而降低,在较高的掺混比例下混合灰灰熔点呈现波动性,但均未高于煤的灰熔点。掺混比例为10%时,生物质的加入一定程度上改善了鲍店煤灰的黏温特性,可使气化炉操作温度下限降低约20℃左右。钙长石的生成是造成熔渣黏度迅速增加的主要原因。     

Biomass ash as supplementary cementitious material (SCM)

This paper describes the research done in order to valorise the biomass ash and evaluate its use as supplementary cementitious material (SCM) in the cement industry. The biomass ash samples used in this study were collected from three different power plants. The characterisation of the ashes as SCMs was performed after two different valorisation processes: (i) a vitrification process in order to obtain a new material with high hydraulicity and (ii) an easy de-alkalisation process in order to reduce the alkali content. The results of this work show that biomass ash derived from the combustion of woodchips and straw, properly treated, is characterised by pozzolanic activity and latent hydraulicity that could be exploited for the manufacture of low embodied energy concrete. The ultimate strength of mortars prepared using vitrified biomass ash becomes higher than that of the parent Portland cement after 28 days.     

Ash transformation during co-firing coal and straw

Co-firing straw with coal in pulverized fuel boilers can cause problems related to fly ash utilization, deposit formation, corrosion and SCR catalyst deactivation due to the high contents of Cl and K in the ash. To investigate the interaction between coal and straw ash and the effect of coal quality on fly ash and deposit properties, straw was co-fired with three kinds of coal in an entrained flow reactor. The compositions of the produced ashes were compared to the available literature data to find suitable scaling parameters that can be used to predict the composition of ash from straw and coal co-firing. Reasonable agreement in fly ash compositions regarding total K and fraction of water soluble K was obtained between co-firing in an entrained flow reactor and full-scale plants. Capture of potassium and subsequent release of HCl can be achieved by sulphation with SO₂ and more importantly, by reaction with Al and Si in the fly ash. About 70–80% K in the fly ash appears as alumina silicates while the remainder K is mainly present as sulphate. Lignite/straw co-firing produces fly ash with relatively high Cl content. This is probably because of the high content of calcium and magnesium in lignite reacts with silica so it is not available for reaction with potassium chloride. Reduction of Cl and increase of S in the deposits compared to the fly ashes could be attributed to sulphation of the deposits.     

Compositional constraints on slag formation and potassium volatilization from rice straw blended wood fuel

Experimental melting of biomass ash blends demonstrates that the addition of rice straw to a dominantly wood-based fuel causes a marked freezing point depression in the liquidus temperature of the inorganic slag from well above 2000 °C to a minimum of about 1260 °C. The minimum temperature is achieved for ash blends with about 30% rice straw ash. The melting interval (liquidus to solidus) for the ash blends is typically 100–200 °C. The solidus shows a systematic decrease from about 1350 °C to as low as 800 °C for pure rice straw ash. Potassium is completely lost from slag for blends with less than 30% rice straw ash content. The addition of more than 30% rice straw ash results in an enhanced retention of potassium in the solid slag. Potassium loss for fuel blends with above 30% rice straw ash is further positively correlated with melting temperature. As the temperature approaches the solidus, potassium is increasingly bound in the melt as well as in potassium–aluminum silicate minerals (leucite) and, therefore, partially retained in the slag. There are indications that melting temperatures above the ‘true’ liquidus for rice straw-rich blends cause partial potassium loss and consequently a rise in the liquidus. This will result in an apparent extending of the melting interval for blends with above 30% rice straw ash. The liquidus silicate mineralogy of the slag changes as a function of increasing rice straw ash from larnite, to åkermanite, wollastonite, and diopside. This mineralogical sequence reflects an increase in the Si/Ca ratio and polymerization of the melt. The experimental slag shows favorable similarities to the mineralogy and composition of slag formed in commercial biomass-fueled boilers, suggesting that the simplified conditions of the experimental melting study can be used to predict combustion conditions in commercial biomass-fueled boilers. Thus, small additions of straw to a predominantly wood fuel should have the effect of lowering slag melting temperature and relatively reducing potassium loss to the flue gas. If combustion temperature can be controlled to within, or below, the melting interval of the ash (< 1260 °C), the relatively loss of potassium can be minimized. Boiler operation below the minimum solidus temperature (∼ 1050 °C) will further strongly restrict loss of potassium.