外掺MgO与水泥内含MgO在大体积混凝土中的膨胀效应

为了了解外掺MgO膨胀剂与水泥内含MgO组分在大体积混凝土中的膨胀效应,分析了MgO膨胀剂与内含MgO水泥的烧成条件、质量稳定性、质量和掺量控制标准,以及实际工程的应用效果。结果表明,使用外掺MgO膨胀剂方式,比采用高含MgO水泥生产的MgO混凝土膨胀效果好,且更能发挥MgO混凝土技术的优越性。     

外掺MgO混凝土的膨胀及其在约束条件下的强度

本文研究了外掺MgO混凝土的膨胀及其在约束条件下的强度。试验结果表明,MgO混凝土的膨胀随MgO膨胀剂掺量的增加而增大,养护温度越高,膨胀速度越快。在MgO膨胀剂掺量与养护温度相同的条件下,二维约束能够提高外掺MgO混凝土的强度。     

80℃加速养护评定外掺MgO膨胀剂混凝土的安定性

本文采用80℃水养护与实际工程用混凝土配合比相同的外掺MgO膨胀剂的混凝土试件,通过考察试件膨胀、劈拉强度和微观结构的变化,综合评估外掺MgO膨胀剂的混凝土的体积安定性。结果表明,80℃水养护能够有效加速MgO膨胀的水化,使其膨胀在90d内趋于稳定。掺5%和8%MgO膨胀剂的混凝土试件的劈拉强度比未掺膨胀剂的混凝土高,且微观结构完好,表明掺MgO膨胀剂的混凝土体积安定。     

MgO掺量对不同介质膨胀性能的影响

为了解MgO外掺量对不同介质膨胀性能的影响规律,进行了不同MgO外掺量情况下的水泥净浆、水泥砂浆、混凝土砂浆的压蒸膨胀率和混凝土的自生体积变形试验.试验结果显示,不同介质的压蒸膨胀率和混凝土的自生体积变形均随着MgO外掺量的增大而增大.当MgO外掺量过大时,经过压蒸后各种介质的试件都因过大的膨胀力造成外观的弯曲变形.研究成果对MgO混凝土膨胀变形测定方法的制定和最大MgO外掺量的确定具有参考意义.     

80℃蒸汽养护条件下外掺MgO膨胀剂三级配混凝土的膨胀

在80℃蒸汽养护条件下,粗骨料粒径为5～20 mm、20～40 mm、40～80 mm三级配MgO混凝土试件的膨胀。结果表明,80℃蒸汽养护条件下,三级配MgO混凝土试件,28 d前膨胀快之后膨胀放缓,90 d时膨胀趋于稳定。MgO膨胀剂的活性越高,MgO混凝土试件最终产生的膨胀越小。粉煤灰降低掺低活性MgO膨胀剂混凝土试件膨胀,而对掺高活性MgO膨胀剂的膨胀影响较小。     

堵头混凝土性能试验研究

通过对不同膨胀剂品种及掺量、不同水泥品种混凝土性能试验研究表明:在水泥净浆安定性合格前提下,单掺或复掺MgO、ZY膨胀剂均不能配制出满足设计要求膨胀量的的堵头混凝土。建议对低MgO含量水泥、低热水泥和其它品种膨胀剂做进一步试验研究,以配制出设计需要的膨胀量的堵头混凝土。     

轻烧MgO膨胀剂对水工混凝土耐久性能的影响

文章研究了外掺轻烧MgO膨胀剂对C25水工混凝土的抗水渗透性能、抗氯离子渗透性能、抗冻性能和抗碳化性能的影响,探讨了轻烧MgO膨胀剂的掺量及水化活性值对C25水工混凝土耐久性能的影响。结果表明:轻烧MgO膨胀剂在外掺6%范围内,随着掺量增加,C25混凝土的抗渗性能、抗碳化能力提升;MgO水化活性值越低,混凝土的碳化深度越低;150次冻融循环内,外掺6%以内轻烧MgO膨胀剂对抗冻性无明显影响。外掺6%以内轻烧MgO膨胀剂对水工混凝土耐久性具有改善作用。     

碾压混凝土外掺MgO安定性试验研究

本试验对掺MgO膨胀剂的碾压混凝土在常压90℃,绝湿养护条件下进行了混凝土安定性试验。结果显示MgO混凝土膨胀破坏主要发生在水泥石与骨料的界面上,随着MgO膨胀剂掺量的增加,劈裂抗拉强度降低,孔隙率提高,超过临界掺量6%后,水泥石与骨料界面出现裂缝,孔隙率激增,强度锐减。     

MgO对水泥-粉煤灰胶凝材料膨胀及微观性能的影响

采用中热硅酸盐水泥、粉煤灰、氧化镁膨胀剂制备水泥-粉煤灰微膨胀胶凝材料，研究MgO膨胀剂对浆体初始流动度、膨胀效能、孔结构和微观结构的影响。结果表明：浆体初始流动度随膨胀剂掺量增加而减小；在相同养护龄期下，膨胀率随膨胀剂掺量增加而增大；在相同掺量下，膨胀率随着养护龄期的延长而增大；加入粉煤灰后会抑制MgO膨胀剂的微膨胀性能。MgO膨胀剂掺量为7%时，孔径及孔隙率最小，且随着MgO水化的进行，孔隙中的Mg(OH)2数量不断增多，结构更加致密。     

民用建筑用轻烧MgO膨胀剂的制备与性能

针对民用建筑混凝土收缩开裂的特点,以菱镁矿为原材料,制备了民用建筑用轻烧MgO膨胀剂(UMEA),研究了掺UMEA水泥净浆的变形性能,包括压蒸安定性能、水养(20℃)膨胀性能、自收缩性能以及干燥收缩性能.结果表明:UMEA既具有较大的早期膨胀、又具有持续的后期微膨胀,对水泥净浆自收缩和干燥收缩均具有较好的补偿作用;掺U...     

石灰石粉作为掺合料在混凝土中的应用研究

针对当前石灰石粉作为掺合料在混凝土中的应用存在的问题,以C35混凝土的配合比为例,从原材料、混凝土的拌合物性能试验、力学性能、抗冻性能和使用注意事项及社会经济效益等几方面详细阐述了石灰石粉作为掺合料在混凝土中的应用研究过程,为类似使用提供参考。     

Recycled glass replacement as fine aggregate in self-compacting concrete

With increasing environmental pressure to reduce solid waste and to recycle as much as possible, the concrete industry has adopted a number of methods to achieve this goal by replacement of waste glass with concrete composition materials. Due to differences in mixture design, placement and consolidation techniques, the strength and durability of Self Compacting Concrete (SCC) may be different than those of conventional concrete. Therefore, replacement of waste glass with fine aggregate in SCC should deeply be investigated compared to conventional concretes. The aim of the present study is to investigate the effect of glass replacement with fine aggregate on the SCC properties. In present study, fine aggregate has been replaced with waste glass in six different weight ratios ranging from 0% to 50%. Fresh results indicate that the flow-ability characteristics have been increased as the waste glass incorporated to paste volume. Nevertheless, compressive, flexural and splitting strengths of concrete containing waste glass have been shown to decrease when the content of waste glass is increased. The strength reduction of concrete in different glass replacement ratios is not remarkable, thus it can be produced SCC with waste glass as fine aggregate in a standard manner.     

Palm kernel shell as a lightweight aggregate in concrete

An artificial aggregate, the plam kernel shell obtained from palm nut, can be classified as organic lightweight aggregate.

Tests on the concrete made with this material as coarse aggregate, show a density range of 1450 kg m⁻³ to 1750 kg m⁻³, which classifies it as lightweight concrete. Compressive strength results of the concrete show that there is increase in strength with curing period, for up to 90 days tested. Based on the American Standard for Testing Materials, the shell concrete is adequate as a structural concrete. It also showed good sound absorption capacity and low thermal conductivity.     

“双掺”泵送混凝土配合比项目优化研究

针对当前"双掺"泵送混凝土配合比项目优化研究存在的问题,以泵送混凝土强度等级C30为例,进行配合比双掺技术研究。从技术方案及主要操作流程、混凝土的试验分析和社会及经济效益等方面详细阐述了"双掺"泵送混凝土配合比项目优化研究的过程,供相关人员参考借鉴。     

Utilization of alkali-activated copper slag as binder in concrete

This study was focused on developing concrete using alkali-activated copper slag (AACS) as a binder. The properties of alkali-activated copper slag concrete (AACSC) were compared with portland cement concrete (PCC). Different AACSC mixes were prepared with varying Na₂O dosage (6% and 8% of the binder by weight) and curing methods. Hydration products in AACSC were retrieved using Fourier-transform infrared spectroscopy (FTIR) and X-ray powder diffraction (XRD) techniques. The test results indicate that the workability of AACSC was lesser than that of PCC. The AACSC mix with 6% Na₂O dosage has exhibited similar mechanical properties as that of PCC. The mechanical properties of AACSC were higher than PCC when 8% of Na₂O dosage was used. Heat curing was effective to upgrade the strength properties of AACSC at an early age of curing, but at a later age mechanical properties of ambient cured and heat-cured AACSC were comparable. The hydration products of AACSC were not identified in XRD patterns, whereas, in FTIR spectra of AACSC some alkali-activated reaction products were reflected. The AACSC mixes were found to be more sustainable than PCC. It has been concluded that AACSC can be produced similarly to that of PCC and ambient curing is sufficient.     

混凝土外加剂的质量检测及其分析

2005年7月至2006年6月扬州市建筑工程质量检测中心检测了扬州地区建筑工程中使用的191份混凝土外加剂的质量,并对检测结果进行了分析,指出了一些问题。     

混凝土泵送剂中的缓凝组分对商品混凝土的性能影响浅析

商品混凝土中最主要的原材料是胶凝材料、化学外加剂。本文主要根据一种怪水泥在调整其与外加剂相容性的过程中,对混凝土的硬化前坍落度损失、硬化后的立方体抗压强度、耐久性能中抗氯离子渗透性能进行试验分析,论述混凝土泵送剂中的缓凝组分对混凝土硬化前及硬化后的性能的影响。     

偏高岭土作混凝土掺合料的研究

高岭土经热处理得到的偏高岭土具有很强的火山灰活性，是一种新型混凝土掺合料。分析了偏高岭土提高水泥胶砂强度的机理，指出高岭土热处理以800℃保温2h的效果较好。     

玄武岩-矿渣-石灰石微粉制备混凝土的试验研究

研究了将玄武岩、矿渣和石灰石磨细成微粉用作混凝土掺合料,通过正交试验,分析了水灰比、砂率、玄武岩粉掺量、矿渣微粉掺量及石灰石粉掺量5因素对玄武岩混凝土工作性能、抗压强度和抗氯离子渗透扩散性的影响.综合考虑各因素对三指标的影响,得出制备C45混凝土的适宜配合比.通过SEM照片对各龄期微观结构分析发现其密实度明显高于基准混凝土.     

废混凝土作粗集料、废砖作细集料制备再生混凝土的实验研究

将实验室检测用废混凝土试块和废黏土砖经破碎、筛分后,作为再生混凝土粗细集料应用。结果表明,经过合适的配比。配制出满足强度和工作性能要求的混凝土：在严格控制试验用水量的条件下,采用预加水浸泡再生细集料的方法,能够得到工作性能良好的再生混凝土。