Effect of lignosulfonate, calcium chloride and their mixture on the hydration of RHA-blended portland cement

Hydration of 10 wt.% rice husk ash (RHA)-blended Portland cement has been studied in the presence of 2 wt.% CaCl₂, 1 wt.% lignosulfonate (LS) and a mixture of the two admixtures by using different methods. Free lime determinations and differential thermal analysis have shown that CaCl₂ accelerates the pozzolanic reaction of Ca(OH)₂ and RHA. In the presence of mixture of two admixtures, lower amount of water is required for consistency of the paste. IR spectral studies have supported that the mixture of the two admixtures act as a strong accelerator for cement hydration. The compressive strength is highest in the presence of a mixture of the two admixtures at 28 days of hydration. The admixtures did not prevent the deterioration of the blended cement in corrosive atmosphere.     

Effect of chloride solutions on portland cement

Expansion of hardened normal Portland cement in chloride solutions exceeded that in distilled water, but specimens made of ground cement-clinker were not appreciably affected by the presence of chloride ions. Addition of chloride ions to sulphate solutions caused increased expansion of cement pastes, but the combined effect of chloride and sulphate ions was less than that of the sum of the separate components. Magnesium and calcium chloride were more aggressive than sodium and potassium chloride. In chloride solutions, richer cement pastes were more strongly expanded than poorer ones, in contrast to their behaviour in sulphate solutions. The results are interpreted in terms of the rates of formation of calcium chloroaluminate, the effect of chloride ion on sulphoaluminate crystallisation, slight variations in composition of the chloride phase and leaching of some of the reaction products.     

Effect of curing conditions on the total water content of hardened portland cement paste

The effect of various curing conditions on the amount of water held by pastes with low water/cement ratios was investigated. It was concluded from the results that factors significantly influencing the total water content of a cement paste made with ordinary Portland cement and cured at room temperature are: water/cement ratio, curing medium, curing period and curing history.     

Effect of applied stress on the helium inflow characteristics of hydrated portland cement

Studies of porous hydrated portland cement have been carried out to assess quantitatively some aspects of microstructural deformation due to applied stress. Hydrated portland cement paste cured for six years at a water/cement ratio of 0.6 was sliced into discs 1.25 mm thick. These were positioned in a specially designed sample holder and loading device that permitted the specimens to be placed under uniaxial compressive stress at 7.1, 14.8 and 22.8 MPa. Helium intake and pycnometric measurements were made at 0, 2.5, 4.5, 7.0 and 9.0 per cent moisture loss with respect to the 11 per cent RH condition. Maximum effects were observed at 7.0 per cent moisture loss, at which helium intake was reduced by 48 per cent at 40 h. Densities were also reduced by stress, and it was concluded that entrances to interlayer space were constricted during application of stress.     

Hardened portland blast-furnace slag cement pastes: I. Effects of additives on surface area and on pore structure

Portland blast-furnace slag cement pastes were prepared with various water/cement ratios. Specific surface areas and pore structures of the hardened pastes were investigated by nitrogen adsorption. The “accessibility” of the nitrogen molecules to the pore structure is discussed in terms of degree of hydration and total porosities of the pastes. Effect of presence of CaCl₂, a typical steel reinforcement corrosive agent, was also studied, and results indicated that it alters the area and pore structure extensively, to a more “open structure,” thus facilitating its own accessibility. Lime and gypsum addition was also studied in presence and in absence of CaCl₂, and the effect of the Blaine surface area of the unhydrated cement is particularly emphasized in this investigation.     

Differentiation of interlayer and adsorbed water in hydrated portland cement by thermal analysis

Work leading to the new model of hydrated portland cement has shown that much of the water previously considered to reside on free surfaces exists as interlayer water. In the present work samples were conditioned at various relative humidities for times varying from to 14 months and were dried to two different levels before conditioning, one being d-dry. Conditions were chosen, based on the model, so that the different states of water could be clearly illustrated. It was concluded that thermal analysis allows differentiation of interlayer and physically adsorbed water and that the different degrees of drying and very long times allowed for equilibration support all sorption results on which the new model of hydrated portland cement was based.     

磷渣硅酸盐水泥的水化与硬化

使用差热、红外、衍射、电镜、压汞等仪器和方法,对磷渣硅酸盐水泥的水化动力学和水化产物进行试验研究,取得了一致的结果;由于组成粒化磷渣的硅灰石玻璃体具有较高的凝聚程度和最终强度,帮磷渣水泥早期水沦速度较底,后期强度增进率较高。渣玻璃体中磷酸盐的溶出对水泥早期水化和凝结时间也有明显的影响。磷渣水泥的水化过程及水化产物基本相同于矿渣水泥。可以采用发迹磷渣成分,提高熟料质量、细磨、外加激发剂等工艺措施来提     

电炉渣水分对水泥易磨性影响研究

对水泥不同孔径筛筛余物进行了化学成分分析,并结合水泥原材料化学成分、易磨性能,分析了不同粒径范围水泥原材料的分布情况及造成其区别的主要原因;探讨了混合材电炉渣水分对水泥易磨性的影响.     

消石灰、无水石膏与石灰石粉对矿渣水泥性能的影响

通过掺加消石灰、无水石膏和石灰石粉提高矿渣水泥的早期强度、干缩等性能。研究结果表明：消石灰、无水石膏及石灰石粉可加速矿渣水化进程,并使水泥浆体密实度提高,最终体现为矿渣水泥早期抗压强度大幅度提高。复合掺加消石灰、无水石膏和石灰石粉的矿渣水泥水化早期的干缩率小于普通硅酸盐水泥,水化后期矿渣水泥的干缩率稍大于普通硅酸盐水泥,但大大小于未掺激发剂的矿渣水泥。     

不同助磨剂对矿渣硅酸盐水泥的性能影响

本文通过调整不同助磨剂[三乙醇胺与柠檬酸中和物（TC）、二乙醇单异丙醇胺（DEIPA）和聚羧酸超塑化剂（PC）]的掺量（0.01%、0.02%和0.03%）,系统研究了其对矿渣硅酸盐水泥的粉磨性能（粒径分布、筛余量和比表面积）、工作性能（凝结时间和需水量）和强度的影响。研究发现,在矿渣硅酸盐水泥中,各助磨剂的粉磨性能大小为DEIPA＞TC＞PC;提高需水量能力大小为DEIPA＞TC＞PC,其中PC能有效降低需水量;DEIPA和TC对3 d和28 d强度均具有较好的提高作用。通过调整三类助磨剂的比例,必定能使助磨剂兼顾粉磨效率高、降低需水量和提高早期后期强度等效果。     

Hardened portland blast-furnace slag cement pastes III. Corrosion of steel reinforcement versus pore structure of the paste matrix

The pore structure of the slag cement paste matrix seems to affect to a sensible extent the corrosion behavior of embedded steel. For both additive free, and additive containing slag cement pastes, the pore structure data were discussed in paper I of this series, whereas the corrosion behavior of embedded steel was discussed in paper II. In this paper III, the correlation between papers I and II is established, and the concluding remarks presented.     

The effect of water content and cement content on the strength of portland cement-stabilized compacted fly ash

Class F fly ash, when combined with portland cement and hydrated, forms a high-strength material whose strength increases with increasing cement content and compaction effort, and is highest near optimum water content of around 20–30%. However, fly ash in stockpiles can be at a water content of around 50%, so completely drying to optimum water content may not be practical. If the material is left at its stockpile water content, the cement content required to achieve a given strength is about 2.5–3 times higher than the cement content required if compacting at optimum water content. However, strength can be predicted as a function of water content for water contents between the stockpile water content and the optimum water content.     

超细矿渣微粉对硅酸盐水泥性能影响研究

用超细矿渣微粉取代不同量水泥,研究超细矿渣微粉对水泥砂浆流动度,力学性能,干燥收缩及其抗冻性的影响,结合XRD结果说明超细矿渣微粉对水泥浆体早期水化的影响。结果显示超细矿渣微粉具有高活性,可以加速早期水泥水化,适量的取代水泥用量,提高水泥基材料的机械性能及耐久性,可以作为掺和料加入水泥基材料。     

Investigations on the relationship between porosity,structure and strength of hydrated portland cement pastes I. Effect of porosity

In a series of cement paste specimens made with different water-cement ratios and hydrated for different times the relationship between porosity and strength was determined. For a range of porosities between 5 and 28 per cent this relationship can be best expressed in the form of a linear plot. At equal porosities strengths of specimens obtained by pressing lie distinctly below those obtained by casting.     

Volume change on first drying of hydrated portland cement with and without admixtures

The effect of admixtures of several types on the volume change characteristics of portland cement pastes is reported. Samples were cut in the form of wafers and dried step by step through several humidities down to 40 per cent; other samples were dried to the d-dried state. Large first drying shrinkages were obtained with extra dosages of calcium lignosulphonate, hydroxy carboxylic acids, and triethanolamine. Below 40 per cent RH all samples showed similar behavior with further drying or rewetting. It is suggested that the effect of admixture is mainly one of degree of dispersion in terms of alignment of sheets and displacement of ends of sheets.     

A simple relationship between the compressive strength and porosity of hydrated portland cement

Previous work has shown that, for a series of experimental autoclaved aerated concretes with porosities ranging from 0.48 to 0.78, compressive strength is linearly related to the solid/pore volume ratio determined by helium pycnometry. In the work described here, this type of relationship has been applied to experimental data from hydrated Portland cement specimens, prepared using initial water/cement ratios of 0.35 to 0.50 and curing times of 2 to 28 days, with porosities ranging from 0.26 to 0.45. The relationship was found to provide a good fit using data obtained both by varying the water/cement ratio at constant curing times and by varying the curing time at constant water/cement ratios.     

磷渣对硅酸盐水泥凝结时间的影响及机理

重点研究了磷渣对硅酸盐水泥凝结时间的影响,以及几种常用外加剂硫酸钠、烧石膏和烧明矾石对磷渣水泥凝结时间的改善,并研究了一种以硫铝酸钙为主要矿物组成的合成外加剂的作用。结果表明磷渣的掺量与比表面积对磷渣硅酸盐水泥的缓凝作用非常大,硫酸钠和合成外加剂对磷渣的缓凝的改善效果最佳,烧石膏与烧明矾石的作用不显著。通过对磷渣的缓凝机理的研究,指出了磷渣中的PO43-溶出对水泥的缓凝作用。     

石膏掺量对碱激发矿渣水泥砂浆性能的影响

研究了石膏掺量对碱矿渣水泥砂浆流动性、力学性能、干缩及水化性能的影响。结果表明,掺入1%～5%的石膏,碱激发矿渣水泥砂浆的流动度下降;石膏掺量在2%以内时,可提高砂浆的强度,但当掺量超过2%后,强度开始下降;石膏掺量在1%～5%范围内递增时,砂浆的干缩率随之降低。交流阻抗谱分析表明,在碱矿渣砂浆中掺入1%～5%的石膏时,Nyquist图形从30 min～1 d的非Randles图形逐渐过渡到3～28 d的准Randles曲线,表明砂浆内部的电化学反应与其水化反应相匹配,交流阻抗参数R_1、R_2在3 d后随着石膏掺量增大而增大,表明石膏在一定程度上促进了砂浆的水化。     

增钙液态渣、高炉矿渣制生态型胶凝材料

将旋风炉增钙液态渣、矿渣分别磨细,与少量碱性激发剂混合后制成生态型胶凝材料.激发剂由改性脱硫石膏和低碱度材料配制.选择增钙液态渣/矿渣质量比、激发剂用量和粉磨细度3个因素,采用正交试验进行配方和工艺参数优化,优化后的胶凝材料质量分数为增钙液态渣61%,矿渣26%,激发剂13%.按GB/T 17671-1999对胶凝材料进行测试,28天胶砂抗压强度达到34.0 MPa,抗折强度达到5.9 MPa,安定性、凝结时间合格.并对增钙液态渣的活性、增钙渣与矿渣的协同作用和体系的低碱度特征进行了简要讨论.