矿物掺合料与高效减水剂对水泥基材料流变性能的影响

利用磨细粉煤灰、磨细矿渣和硅灰作为矿物掺合料,分别研究了矿物掺合料、高效减水剂以及它们复合作用时对水泥净浆浆体流变性能的影响情况。研究结果表明：矿物掺合料与高效减水剂“双掺”时,大大提高了水泥浆体的流动性。在此基础上,本文着重分析了高效减水剂与矿物掺合料对水泥基材料流变性能的作用机理。     

黏土和石粉含量对聚羧酸减水剂的影响研究

选用聚羧酸减水剂加到水泥净浆中,利用测定水泥、黏土和石粉的吸水性,同时,通过对水泥净浆流动度和抗压强度等性能的研究,探讨黏土和石粉含量(0、0.5%、1%、2%、4%、8%)对掺聚羧酸减水剂的净浆性能影响规律。结果表明:掺减水剂的浆体,随含泥量的增大,其流动度与7、28 d抗压强度均降低。掺减水剂的浆体,随石粉含量的增加,其流动度变化不大;含量小于4%时,试块7、28 d抗压强度基本不变,甚至增大。黏土和石粉同时取代水泥时,其含量小于2%时,对掺聚羧酸减水剂的净浆7、28 d抗压强度影响不大;但当含量超过0.5%,掺聚羧酸的净浆流动度明显下降。     

A model for predicting the carbonation depth of concrete containing low-calcium fly ash

Low-calcium fly ash (FL) is a general product from the combustion of anthracite and bituminous coals and has been widely used as a mineral admixture to produce high strength and high performance concrete. Carbonation of cement blended with fly ash is much more complex than ordinary Portland cement because of the pozzolanic activity in an aluminosilicate glass phase of fly ash. In this paper, based on multi-component concept, a numerical model that can predict carbonation of low-calcium fly ash contained concrete was built. This numerical model includes two parts: hydration and carbonation models. The hydration model starts with a mix proportion of concrete and considers both Portland cement hydration and pozzolanic activity. By applying a hydration model, the amount of hydration product that is susceptible to carbonate as well as porosity was obtained as a function of curing age. Furthermore, the diffusivity of CO₂ in concrete was determined and the carbonation depth of concrete was also predicted. The prediction results showed good agreement for the results of the experiment performed in this study.     

可溶碱对水泥/氨基磺酸盐减水剂相容性的影响

测定了水泥浆体中的总碱含量和可溶碱含量.通过掺加K2CO3溶液(改变水泥浆体中可溶碱的含量),同时调整氨基磺酸盐高效减水剂掺量,观察水泥浆体的流动度和流动度经时损失变化,以确定水泥浆体中可溶碱含量对水泥/氨基磺酸盐高效减水剂相容性的影响.研究结果表明:氨基磺酸盐高效减水剂掺量和水泥中的可溶碱含量共同决定了水泥浆体的流动度.水泥中所含可溶碱含量低于最佳可溶碱含量.当氨基磺酸盐高效减水剂掺量小于其饱和掺量时,掺加适量的可溶碱有助于提高水泥浆体的流动度,减小水泥浆体流动度经时损失;当氨基磺酸盐高效减水剂掺量大于其饱和掺量时,则基本上可以不考虑可溶碱含量对水泥浆体流动度的影响.     

特细砂高强混凝土的初步探索

本文初步探索了使用特细砂,同时掺加高效减水剂、粉煤灰、硅灰等配制出C50￣C80的高强度混凝土的一系列性能,诸如和易性、强度、弹性模量等。试验结果表明采用低砂率,同时双掺高效减水剂和矿物掺合料时,在不增加水泥用量的前提下,完全可以配制出满足要求的C50￣C80的高强度混凝土。     

粉煤灰、矿渣及硅灰对水泥胶砂流动性及早期强度的影响

本文在试验的基础上研究了矿物掺合料单掺和复掺时对水泥胶砂流动性及1d早期强度的影响。试验结果表明,与不掺掺合料的基准胶砂相比,矿物掺合料的使用可以提高胶砂的流动度,但同时极大地降低了胶砂的早期强度。与单掺粉燥灰的胶砂相比,多种矿物掺合料复掺可以提高胶砂的1d强度,但会降低胶砂的流动性。     

掺高效减水剂水泥砂浆的早期开裂研究

采用多通道椭圆环收缩开裂试验、自由收缩试验和强度试验综合评价了萘系（UNF）、聚羧酸类（PC）高效减水剂对水泥砂浆体积稳定性及早期开裂的影响．结果表明,高效减水剂的掺入延长了水泥砂浆的初始开裂时间,从而降低了水泥砂浆的开裂敏感性．高效减水剂降低水泥砂浆开裂敏感性的效果为：聚羧酸类〉高浓型萘系〉普通型萘系．掺高效减水弃1均增大了水泥砂浆的自由收缩值,且水泥砂浆自由收缩值随着高效减水剂掺量的增加而增大．高效减水剂控制水泥砂浆体积稳定性的效果为：聚羧酸类〉普通型萘系〉高浓型萘系．聚羧酸类高效减水剂的掺入减小了水泥砂浆的最大裂纹宽度,而萘系高效减水剂的掺入则加快了水泥砂浆最大裂纹宽度的发展速度．在干燥养护条件下,掺聚羧酸类高效减水剂比掺萘系高效减水剂更能有效地提高水泥砂浆28d的强度．     

C30大体积高流态高性能混凝土设计

利用氨基磺酸盐系、萘系减水剂及缓凝、引气和浆体稳定组分复配出适用于大体积高流态混凝土的高效泵送剂,通过胶砂强度实验得出矿渣和粉煤灰的最佳掺量比例;采用最佳浆骨比法设计混凝土配合比,经过计算検耘錀调整的方法确定了C30大体积高流态混凝土的高性能化设计方案;并通过计算检验混凝土温度以避免大体积混凝土施工过程中温度裂缝出现。     

石灰石粉作掺合料对混凝土工作性能的影响

通过Marsh筒[1]、胶砂流动度及实测混凝土和易性等方法,研究了石灰石粉作掺合料对混凝土工作性能的影响,并与粉煤灰的效果相对比.试验结果表明:一定颗粒分布的石灰石粉能改善新拌混凝土的流动性能,减少泌水率及缩短凝结时间.     

木聚脂肪族高效减水剂与水泥相容性研究

通过水泥净浆流动度试验,研究了新型木聚脂肪族高效减水剂与水泥的相容性.讨论了不同掺量减水剂与不同熟料、不同细度、含不同混合材及其掺量的水泥之间的相容性.结果表明,减水剂掺量为1.6%时与各种水泥有良好的相容性.但水泥比表面积大于4000cm2/g时,随着水泥比表面积的增加,30min及60min经时流动度损失较大;当水泥熟料中C3A含量较低(10%以下)时,降低C3S/C2S比值可以减小水泥浆体流动度的经时损失.粉煤灰与矿粉双掺,可以进一步提高木聚脂肪族高效减水剂与水泥的相容性.     

聚羧酸减水剂复合无碱速凝剂对水泥浆体凝结时间和早期强度的影响

研究了不同聚羧酸减水剂与自制无碱液体速凝剂复合后对水泥浆体凝结时间与早期强度的影响。结果表明:当无碱速凝剂掺量为水泥质量的6%时,复合推荐掺量的不同类型减水剂会显著延缓水泥净浆的凝结时间;当速凝剂掺量提高至7%时,凝结时间会缩短-延长。掺入市售聚羧酸减水剂的水泥净浆在静置30、60 min后再加入速凝剂,与同掺减水剂和速凝剂的水泥净浆相比,凝结时间延缓明显;但采用复合了保坍组分的自制聚羧酸减水剂再加入速凝剂,对水泥浆体的凝结时间影响不大。添加自制聚羧酸减水剂还会对掺无碱速凝剂水泥砂浆的1 d强度有一定的提高。     

The effect of cement alkali content on ASR susceptibility of mortars incorporating admixtures

In this study, the effects of three types of plasticizing chemical admixtures (modified lignosulfonate, sulfonated naphthalene formaldehyde and polycarboxylate based) on deleterious expansion due to alkali–silica reaction (ASR) have been investigated. Two different types of cements with low (0.53 Na₂O eq.) and high (0.98 Na₂O eq.) alkali contents, a non-reactive crushed limestone as fine aggregate and a reactive river sand were used within the scope of the experimental program. ASR tests were conducted according to accelerated mortar bar method (ASTM C 1260). Additionally the flow value, dry unit weight, capillary water absorption and compressive strength tests were performed. Test results indicated that mortars prepared with inert fine aggregate caused no significant expansion, regardless of cement type, admixture type and dosage. However, for mixes containing reactive sand, admixtures increased or decreased the expansion values (compared to plain mortars) depending on the alkali content of cement used. The magnitude of change of expansion also depended on the type and amount of admixture incorporation which have a dominant effect on stability and compactability of mortars. The high-alkali cement usually revealed the ASR expansion augmentation behaviour of admixtures. In contrast, low alkali cement decreased the expansion values compared to the control specimens.     

低水胶比下矿物掺合料对水泥与减水剂相容性的影响

本文从低水胶比时，在水泥基中单掺不同量的超细粉煤灰和硅灰以及复合超细粉煤灰和硅灰对水泥与减水剂相容性影响的现象出发，阐述了低水胶比时矿物掺合料对水泥与减水剂相容性的影响及作用机理。     

矿物掺合料对铁铝酸盐水泥力学性能影响研究

针对铁铝酸盐水泥早期水化热高的问题,提出采用掺加矿物掺合料的方法改善铁铝酸盐水泥性能。研究了单独掺加不同掺量粉煤灰、矿粉、石灰石粉、粉煤灰微珠、硅灰的铁铝酸盐水泥用水量、力学性能,以及复合掺加粉煤灰-矿粉、粉煤灰微珠-矿粉、粉煤灰微珠-硅灰及石灰石灰石粉-矿粉的铁铝酸盐水泥用水量、力学性能。结果表明,粉煤灰等掺合料均会降低铁铝酸盐水泥强度,但是对用水量的影响不同,粉煤灰及硅灰会显著增加铁铝酸盐水泥用水量,石灰石粉及粉煤灰微珠会降低用水量。当掺合料单独掺加或复合掺加等量取代30%水泥时,复合胶凝体系的抗压强度降至45.0MPa左右,掺合料的掺量宜控制在30%以内。     

Relationship between fluidity and stability of self-consolidating mortar incorporating chemical and mineral admixtures

In this study, the effect of chemical and mineral admixtures, including superplasticizer, viscosity modifying agent (VMA), limestone powder and fly ash in different W/C on fluidity, viscosity, and stability of self-consolidating mortar is investigated and proper workability regions for the prepared mixtures are presented. The obtained results indicate that W/C is the most significant parameter influencing the rheological properties of cementitious mixtures, specially their stability. Furthermore, the maximum allowable W/C for preventing inhomogeneity could not be a fixed value for all the mixtures and should be adjusted for the target fluidity. On the other hand, using VMAs is an effective method for stabilizing self-consolidating mortars and preventing any kinds of instability while limestone powder and fly ash mainly affect bleeding and aggregate blockage. Besides, these mineral admixtures improved the fluidity of the mixtures to some extent.     

新型聚羧酸系高效减水剂的合成及性能研究

结合高分子科学及混凝土科学的“分子设计”原理,将丁氧基聚氧乙烯甲基丙烯酸酯（BPEOMA）、AA、MAA、不饱和磺酸盐单体通过自由基水溶液共聚合的方法合成了一种新型梳状聚羧酸系高效减水剂SP,通过傅立叶变换红外光谱表征了减水剂的分子结构.重点研究了磺酸盐种类、用量,不饱和羧酸及引发剂对减水剂性能的影响.结果表明,减水剂SP具有良好的分散性及分散保持性能,折固掺量为0.3%,水灰比为0.29时,水泥净浆流动度可达290mm,90min内坍落度基本不变,且无泌水现象.     

矿质混合料堆积与混凝土致密正填配合比设计

本文首次提出混凝土“致密正填配合比设计法”：先按照固态材料粒度由粗到细的顺序进行逐次填加,寻求矿质混合料体系的正填致密堆积,印粗细集料、矿物掺合料(本文中采用碎石、中砂和粉煤灰)组成的固态颗粒混合物的最大单位重与“最佳填塞率”的关系;再选取合适的水胶比和水泥浆富裕系数进一步进行经济合理的混凝土致密正填配合比设计。在相同的水胶比0．36和减水剂用量SP=1．0％的情况下,致密正填配合比设计法由于矿质混合料的致密堆积,掺入大量(与水泥质量比为77．13％)具有一定细度和活性的粉煤灰,与传统的超量取代法相比,不但在节约水泥30％的情况下强度稳步增长,还将混凝土的抗渗性能提高了20％,对于进一步改善混凝土的耐久性十分有益。     

石灰石粉作为矿物掺合料对水泥胶砂性能的影响研究

本文以石灰石粉等量替代水泥、等量替代粉煤灰或矿渣粉,试验研究了石灰石粉对水泥胶砂流动度和强度的影响。试验结果表明:作为掺合料在砂浆中掺入10%~30%数量的石灰石粉是完全可行的,与单掺粉煤灰相比,石灰石粉与粉煤灰复掺作为掺合料的效果较好;而与矿渣粉相比,石灰石粉与矿渣粉复掺作为掺合料的效果较差。     

Evaluation of the sulfate resistance of concrete containing palm oil fuel ash

The effects of using palm oil fuel ash (POFA) as a new pozzolanic material on sulfate resistance in terms of expansion and loss in compressive strength of concretes exposed to 5% MgSO₄ solution for up to 24 months were evaluated. POFA was processed to obtain different sized particles: small and medium sizes (SP and MP) were produced by grinding, and the large size (LP) used unground POFA. Portland cement type I was replaced by SP, MP, and LP at a level of 10–40% by weight of binder. Results showed that unground POFA (LP) is not suitable for use as a cement replacement in concrete because it produces low compressive strength and can not improve the sulfate resistance of concrete. Increasing proportions of ground POFA (MP and SP), caused a decrease in the expansion of concrete bars and an increase in the loss in compressive strength. However, the expansion and loss in compressive strength were reduced when the POFA fineness was increased. The results suggested that ground POFA (MP and SP) could be used as a pozzolanic material and could also improve the sulfate resistance of concrete.     

Effects of fineness of cement on polynaphthalene sulfonate based superplasticizer–cement interaction

The effects of fineness of portland cement procured from six different Turkish cement plants, on superplasticizer/cement interaction were investigated. CEM I 42.5 type portland cements (PC) were ground into different finenesses ranging from 280 to 550 m²/kg Blaine values. The effects of PC fineness on initial fluidity and fluidity loss of superplasticized cement paste were evaluated. It was found that increasing the Blaine fineness of incompatible cement up to a certain level reduced the viscosity of cement pastes but had no marked effect on the yield stress of the paste mixtures. Nevertheless, flow loss and also saturation point at 60 min increased with increasing the cement fineness. In other words, pastes with lower viscosity can be produced by using finer cement and more superplasticizer.