A Blended Cement Containing Blast Furnace Slag and Phosphorous Slag

Blended cement containing blast furnace slag (BFS) and phosphorous slag( PS) is a new kind of cement. The total content of blended materials could increase if two additives were used. Using the same admixtures , the properties of the blended cement with 70% additives could reach the standard of 525-grade slag cement according to GB. The strength of cement with 80% additives could reach the standard of 425-grade slag cement. The tests of strength, pore structure, hydration products, inhibiting alkali-aggregate reaction, resistance to sulfate corrosion of BFS-PSC were performed.

Combined Recycling of White Rice Husk Ash as Cement Replacement and Metal Furnace Slag as Coarse-Aggregate Replacement to Produce Self-Consolidating Concrete

According to empirical evidence,high levels of energy and considerable amounts of natural resources are used in the production of concrete.Given the context,this study explores self-consolidating concrete(SCC)that includes rice husk ash(RHA)and metal furnace slag(MFS)as an alternative to cement and the natural aggregates in standard SCC mixes.In this study,mixture designs are investigated with 20 wt.%of RHA,10–30 wt.%of MFS and water-to-powder material ratios of 0.30 and 0.40.Based on the findings regarding the fresh-state,hardened-state,and durability properties of the resulting SCC mixes,it is evident that the use of RHA and MFS can significantly improve the properties of concrete.The highest compressive strength was achieved for SCC with 20 wt.%RHA and 10 wt.%MFS.This outcome should be used as a basis for further investigations into the production of concrete materials that are both high-performance and sustainable.

Application of Air-cooled Blast Furnace Slag Aggregates as Replacement of Natural Aggregates in Cement-based Materials：A Study on Water Absorption Property

The influence of air-cooled blast furnace slag aggregates as replacement of natural aggregates on the water absorption of concrete and mortar was studied, and the mechanism was analyzed. The interface between aggregate and matrix in concrete was analyzed by using a micro-hardness tester, a laser confocal microscope and a scanning electron microscope with backscattered electron image mode. The pore structure of mortar matrixes under different curing conditions was investigated by mercury intrusion porosimetry. The results showed that when natural aggregates were replaced with air-cooled blast furnace slag aggregates in mortar or concrete, the content of the capillary pore in the mortar matrix was reduced and the interfacial structure between aggregate and matrix was improved, resulting in the lower water absorption of mortar or concrete. Compared to the concrete made with crushed limestone and natural river sand, the initial absorption coefficient, the secondary absorption coefficient and the water absorption capacity through the surface for 7 d of the concrete made from crushed air-cooled blast furnace slag and air-cooled blast furnace slag sand were reduced by 48.9%, 52.8%, and 46.5%, respectively.

Volumetric Variation and Rheology of Cement Based Mineral Additions （Blast Furnace Slag and Silica Fume）

The partial substitution of clinker by mineral additions offers very significant, both economical and environmental benefits. This adds value to industrial waste, and contributes also in the preservation of natural resources, like clay and limestone, as well as the reduction of greenhouse gas emissions （CO2）. This study is interested in the simultaneous effect of BFS （blast furnace slag） and SF （silica fume） on setting time and water requirement of cement paste. The volumetric variations are tested in mortars, prepared in the same mixture of pastes, and the tests indicate that the addition of slag increase the fluidity, reduce the water demand, shrinkage and expansion, compared to the mortar, containing ten percent （10%） of Silica Fume only. The images of pastes obtained by SEM （scanning electron microscopy）, are indicated an improvement of the microstructure of the paste with a large amount of slag, which leads to improve durability.

Setting and Strength Characteristics of Alkali-activated Carbonatite Cementitious Materials with Ground Slag Replacement

The effect of the ground granulated blast-furnace slag （ GGBFS ） addition, the modulus n （ mole rutio of SiO2 to Na2O ） and the concentrution of sodium silicate solution on the compressive strength of the material, i e alkuli-activated carbonatite cemeutitious material （ AACCM for short ） was investiguted. In addition, it is found that barium chloride has a sutisfiwtory retarding effect on the setting of AACCM in which more than 20% （ by mass ） ground carbonatite was replaced by GGBFS. As a result, a cementitious material, in which ground carbonatite rock served as dominative starting material, with 3-day and 28-day compressive strength greuter them 30 MPa and 60 MPa and with continuous strength gain beyond 90 days was obtained.

Accelerated carbonation and leaching behavior of the slag from iron and steel making industry

Ground granulated blast furnace slag （GGBFS） and steelmaking slag have been used as a raw material for cement production or as an aggregate to make concrete, which contribute aluminum, calcium, iron, and silicon oxides. The suitability of the slag for a particular application depends on its reactivity, cost, availability, and its influence on the properties of the resulting concrete. For the interest of durability studying of concrete in the presence of slag, the accelerated carbonation products and leaching behavior of the slag and Portland cement （PC） were studied. The experimental results confirmed that the slag was more resistant to carbonation compared to PC. The carbonation degree of GGBFS reduced by 17.74%; and the carbonation degrees of steelmaking slags reduced by 9.51%- 11.94%. Carbonation neutralized the alkaline nature of the hydrated pastes and gave rise to the redox potential of the leachate slightly （30-77 mV）. The carbonation also increased the release of most of the elements presented, except for calcium, to the aqueous environment. It is concluded that blend cements （PC plus slag） have economical advantages and better durability compared to PC,

Incorporation of a nanotechnology-based additive in cementitious products for clay stabilisation

The mechanical performances and water retention characteristics of clays,stabilised by partial substitution of cement with by-products and inclusion of a nanotechnology-based additive called RoadCem(RC),are studied in this research.The unconfined compression tests and one-dimensional oedometer swelling were performed after 7 d of curing to understand the influence of addition of 1%of RC material in the stabilised soils with the cement partially replaced by 49%,59%and 69%of ground granulated blast furnace slag(GBBS)or pulverised fuel ash(PFA).The moisture retention capacity of the stabilised clays was also explored using the soil-water retention curve(SWRC)from the measured suctions.Results confirmed an obvious effect of the use of RC with the obtained strength and swell properties of the stabilised clays suitable for road application at 50%replacement of cement.This outcome is associated with the in-depth and penetrating hydration of the cementitious materials by the RC and water which results in the production of needle-like matrix with interlocking filaments e a phenomenon referred to as the‘wrapping’effect.On the other hand,the SWRC used to describe the water holding capacity and corresponding swell mechanism of clays stabilised by a proportion of RC showed a satisfactory response.The moisture retention of the RC-modified clays was initially higher but reduced subsequently as the saturation level increased with decreasing suction.This phenomenon confirmed that clays stabilised by including the RC are water-proof in nature,thus ensuring reduced porosity and suction even at reduced water content.Overall,the stabilised clays with the combination of cement,GGBS and RC showed a better performance compared to those with the PFA included.

Mechanical properties and durability of alkali-activated steel slag-blastfurnace slag cement

Alkali-activated cement(AAC)is either clinker-less or free,and it is also environmentally friendly due to its low carbon footprint and wide range sources.Industrial wastes,like steel slag and blastfurnace slag,usually have latent hydraulic reactivity,and can be used as precursors of AAC.Both clinkerless and clinker-free AAC were prepared from the mixture of steel slag and blastfurnace slag by using water glass as an activator,and four different recipes which satisfied the strength requirement of 42.5R Portland cement were obtained.Each recipe of AAC exhibited better resistance to sulfate attack and frost attack than Portland cement.AAC showed huge drying shrinkage,but it was equivalent to that of Portland cement as steel slag content increased to 40%.The AAC also had quite low risk of alkali-aggregate reaction.Microstructure analysis showed that the major products were calcium silicate hydrate(C–S–H),calcium aluminosilicate hydrate(C–A–S–H)and zeolite-like phases.Ettringite was also detected in the binder when gypsum was contained in the precursors.

Effect of Content and Fineness of GGBS on Pore Structure of Cement Paste

The effect of the content and specific surface area of the ground granulated blast furnace slag (GGBS) on the pore structure of the cement paste was determined through the low-field nuclear magnetic resonance (NMR).The Pearson correlation analysis method was used to calculate the correlation coefficient between the porosity and age of cement paste,the specific surface area of GGBS and the content of GGBS.The test results exhibited that the porosity of the cement paste with different ageing durations gradually decreased on increasing the content and specific surface area of GGBS.The content and specific surface area of GGBS had a negligible effect on the 1-10 nm size gel pores in the cement paste,whereas,had a significant effect on the 10-100 nm size capillary pores.In addition,these parameters did not affect the final most probable pore size of the cement paste.The correlation between age and porosity was the largest,and the correlation between GGBS content and porosity was greater than that between GGBS specific surface area and porosity.Moreover,a modified pore structure model was successfully developed to effectively predict the pore structure of the GGBS based cement paste.

Utilization of Low-Alkalinity Cementitious Materials in Cemented Paste Backfill of Gold Mine Tailings

The purpose of this paper was to explore the possility of using low alkalinity cementitious materials as binders,in which ground blast furnace slag and fly ash acted as a partial replacement of ordinary Portland cement,and CaSO_(4),Na_(2)SO_(4),and CaO were used as a sulfate activator and alkali activated additives,to solidify gold mine tail-ings for preparation of a green,inexpensive cemented paste backill(CPB).For this target,the effects of cement/tailings ratio,superplasticizer dosage,solid content,tailings fineness on the mechanical properties of the CPB were inves tigated.Additionally,the hydration mechanism of the CPB was analyzed based on X-ray diffraction and scanning electron microscopy results.The results showed that the fuidity of the CPB slurry could be improved by adding polycarboxylic acid superplasticizer.The unconfined compressive strength(UCS)of the CPB specimens was increased with the increase of cement/tailings ratio and solid content.Under the same experi-mental conditions,the 28 d UCS of the CPB specimens was 3.8-4.9 times higher than that of ordinary Portland cement.The softening coefficient of the CPB specimens was increased with the increasing cement/tailings ratio,ranging from 0.83 to 0.92.The shrinkage rate of the CPB specimens was decreased from 0.70%to 0.54%with the increase of cement/tailings ratio from 1:12 to 1:4 The UCS of the full tailings CPB was the highest,followed by the fine tailings CPB specimens,and the UCS of the coarse tailings CPB specimens was the lowest.The low alka-linity binder was proved to be a promising material to improve the engineering performances of the CPB.The optimal mixing ratio is 1:6 cement/tailings ratio,0.15 wt% superplastizer dosage,and 70 wt%solid content.Pre-pared by this mixing ratio,the UCS values of the CPB after 3,7,and 28 d curing ages reached 1.85,5.87,and 9.16 MPa,respectively,which were suitable as CPB for the Zhaoyuan gold mine in terms of strength requirements.

高钛矿渣在水泥混凝土中的研究应用进展

区别于普通高炉矿渣,高钛矿渣中TiO_(2)含量较高、矿物组成差异大、利用率低。高钛矿渣大量堆存会造成资源浪费,且给生态环境带来严重负担,因此亟需实现其固废资源化利用。近年来,基于高钛矿渣的矿物成分和结构稳定、微火山灰活性、多孔、集料性能优良等特点,研究人员逐渐将其作为矿物掺合料、粗细骨料等应用于水泥混凝土中,实现高钛矿渣的高效利用以及提高其使用附加值,促进高钛矿渣在混凝土中的工程应用。本文系统梳理了高钛矿渣在水泥混凝土中的研究应用进展,对高钛矿渣的来源、物理化学性质、在混凝土中的利用方式,介绍了其对混凝土工作性能、力学性能、耐久性能等方面影响的研究进展,此外深入论述了高钛矿渣作为矿物掺合料以及再生骨料对混凝土性能的影响及作用机理。最后,针对现阶段研究中的不足提出相应建议,旨在为高钛矿渣在水泥混凝土中的研究和工程应用提供参考。

煤气化渣替代矿渣制备超硫酸盐水泥的可行性研究

煤气化渣(CGS)富含硅、铝元素,具备作为胶凝材料前体的潜力,但其颗粒形态粗糙,活性较低。为了解决CGS活性低、利用难等问题,利用CGS部分替代矿渣(BFS),探究CGS替代BFS制备超硫酸盐水泥(SSC)的技术可行性,并借助傅里叶红外光谱、X射线衍射仪、热重分析仪、扫描电子显微镜及能谱仪等微观测试技术对SSC水化产物的微观结构进行表征分析。结果表明,CGS作为制备SSC的原料,能提供初始水化所需要的硅、铝元素,驱动SSC发生水化反应。随着CGS掺量的增加,SSC胶砂的抗压强度呈逐渐减小趋势,而抗折强度受影响较小。CGS的最佳掺量为20%(质量分数),在此掺量下胶砂试样的28 d抗折强度最大,抗压强度也达到43.9 MPa。SSC的水化产物主要是水化硅酸钙、水化硫铝酸钙等凝胶。研究结果显示CGS部分替代BFS完全可用于制备SSC。

水淬高炉矿渣还原性对高硫尾砂氧化过程的影响探索研究

尾砂是选矿厂在特定的经济技术条件下,将矿石磨细,选取有用成分后排放的废弃物,是我国排放量最大的工业固废。尾砂的大量堆存不仅会形成安全隐患,还会引起占用土地、污染土地和水体等问题。利用尾砂进行矿山充填是实现尾砂大宗量消纳处置的有效途径。高硫尾砂一般指硫元素含量大于8%的尾砂,由于高硫尾砂氧化生成的硫酸根达到一定浓度后就会对水泥的硬化过程有破坏作用,导致高硫尾砂在矿山充填中的利用率较低。找到抑制高硫尾砂氧化的方法是降低高硫尾砂环境污染、提高高硫尾砂充填利用率的途径之一。本文通过开展高硫尾砂氧化试验,对水淬高炉矿渣的还原性对高硫尾砂氧化过程的影响开展了探索研究,通过观察试验结果,结合理论分析和其他学者的研究成果,可以得出结论:①高硫尾砂在水中可以发生氧化反应,主要反应过程为黄铁矿(FeS2)等硫化物与水和水中的溶氧反应生成硫酸根和氢离子;②矿渣微粉对高硫尾砂的氧化过程有抑制作用,可以显著减缓水中高硫尾砂的氧化速率;③矿渣微粉具有还原性,还原性来源是高炉中的还原性气氛,还原性的物质承担者是其中低价态的硫;④矿渣微粉抑制高硫尾砂氧化速率的原因是矿渣中低价态的硫优先与水中的溶氧发生反应,降低了高硫尾砂中硫化物的氧化速率。

激发剂对锂渣-矿粉-水泥复合体系性能的影响

为改善锂渣基胶凝体系水化性能及物理力学性能,以锂渣、矿粉和水泥熟料制备三元复合胶凝材料,并优化了水化硅酸钙/聚羧酸减水剂(C-S-H-PCE)、Na_(2)SiO_(3)、三异丙醇胺(TIPA)3种激发剂的正交配合比。结果表明,C-S-H-PCE明显增加浆体流动度,Na_(2)SiO_(3)显著提升抗压强度和水化性能。相较不掺激发剂的基准组,复配3%C-S-H-PCE、1%Na_(2)SiO_(3)和0.05%TIPA体系的胶凝材料28 d抗压强度提高了5.2%,且72 h放热量最高。Na_(2)SiO_(3)可以促进C-S-H凝胶生成,C-S-H-PCE能够显著降低水泥颗粒与水之间的表面张力,提供更多成核位点促进锂渣后期火山灰反应。TIPA通过加速水化产物形成并优化结构,降低孔隙率。Na_(2)SiO_(3)虽可促进C-S-H生成,但高量Na_(2)SiO_(3)会生成阻碍水化的不溶性硅酸盐。合理配比3种激发剂可显著改善锂渣基胶凝体系的综合性能。

固氚用粉煤灰-矿渣基地聚物水泥体系研究

针对核工业含氚废水安全处理的难题,构建了一种以碱激发粉煤灰-矿渣为基础的地聚物水泥固化体系。优化设计制备的地聚物水泥固化体具有优异的抗硫酸盐侵蚀、抗冻融性能,且微观结构致密。引入聚丙烯酸极大地增强了纤维与基体间的界面粘结性能,从而有效提高了固化体的抗压和抗折强度。模拟氚水的固化实验研究表明,地聚物水泥固化体的氘渗漏率显著低于传统的普通硅酸盐水泥固化体。地聚物水泥固化体采用聚脲喷涂表面处理后,10%氘水浓度下的喷涂前后氘渗漏率分别为25.11%、0.68%。

工业废渣在湖相软土固化改良中的应用研究

为改善湖相软土承载力小、易压缩变形、含水率大的工程特性,提出采用粒化高炉矿渣(GGBS)作为主固化材料,电石渣和Na_(2)SO_(4)作为激发剂材料对湖相软土进行复配固化改良,并与水泥固化方案进行了工程性能对比试验。结果表明:单掺GGBS、电石渣或者Na_(2)SO_(4)均能提升软土强度,分别在12%、2.5%和4%掺量时达到强度最大值,但对于强度的提升程度较小;当采用GGBS(12.18%)+电石渣(2.3%)+Na_(2)SO_(4)(5.31%)的复配方案时,强度提升较为显著,28d龄期强度可以达到1107kPa,是原状软土的24.6倍,其强度改善效果与掺入13%水泥的固化改良效果相当;采用GGBS+电石渣+Na_(2)SO_(4)进行复配固化的软土稳定性强于采用水泥固化的软土,在经历9次干湿循环后,强度仅降低7kPa,而水泥固化组则降低了86kPa,复配固化改良软土具有更优越的工程力学性能。

高炉钛渣基碱激发水泥的制备及其性能

高炉钛渣用作水泥混合材是其综合利用的有效途径之一。以高炉钛渣为原料,氢氧化钠(NaOH)和水玻璃(Na_(2)O·nSiO_(2))复配为激发剂,制备高炉钛渣基碱激发水泥,研究激发剂模数、添加量、养护温度对材料性能的影响,并采用X射线衍射仪(XRD)、傅立叶变换红外光谱仪(FTIR)和扫描电子显微镜/X射线能谱(SEM-EDS)等技术手段分析材料物相组成和微观结构。研究表明,激发剂模数、添加量和养护温度显著影响高炉钛渣基碱激发水泥的抗压强度。当激发剂模数为1.6、掺量为8%、养护温度为65℃时,材料3 d的抗压强度达26.6 MPa,材料无定型相和结晶相钙钛矿CaTiO_(3)变化量分别为6.77%、5.95%。这说明碱激发剂对高炉钛渣存在一定的侵蚀活化作用,促进了C-S-H凝胶生成和材料强度的发展。

含有安定性不良钢渣骨料的混凝土病害诊治研究

某掺入钢渣的现浇混凝土高层住宅项目混凝土表面出现密集鼓起脱落,通过对从现场鼓起部位获得的块状样品和粉末状样品进行电子显微分析、能量色散谱分析和X射线荧光分析,确定混凝土鼓起的原因为混凝土中掺入了安定性不良的钢渣,并获得了安定性不良钢渣的典型微观形貌和元素构成。通过对236个鼓起构件进行分析统计,确定该批混凝土的碳化深度、破坏深度、破坏面直径等指标,为后续研究提供数据支撑。最后,本文建议采用先剔除钢渣和拉毛面层,再挂钢丝网和喷射高强聚合物改性水泥砂浆的处理措施来提高构件耐久性。修复完成后由房屋使用方负责日常巡检,前5年要求每年定期全面巡检1次,5年后每3年定期全面巡检1次。若发现已修补构件出现鼓起现象,应及时请有资质的单位进行检测和处理。

弱碱激发条件下磷渣-水泥复合填料路用性能试验研究

将磷渣固化后作为路基或路面基层填料是固体废弃物资源化利用的有效途径,具有广泛的经济效益和社会价值。本文通过室内和现场试验,从强度和水稳性的角度分析了磷渣-水泥复合填料的路用性能,并通过具体工程案例论证了本文固化方案的可行性。试验结果表明,弱碱激发(pH=8.0)条件下磷渣混合料在压实、固化后可作为路基填料使用,但固化体强度形成较为缓慢,7 d抗压强度约为28 d的50%。经固化后的磷渣-水泥复合填料具备了一定的耐水性,水泥熟料掺量大于7%(质量分数)时,浸泡60 d后未出现影响完整性的破坏,固化体试样的软化系数随着水泥掺量的增加而下降。在保证强度的基础上,固化剂(Na_(2)SiO_(3))的使用可以减少水泥用量,提高磷渣固化方案的经济性;而过度碱激发(pH=10.0)虽然可以提高磷渣固化体的早期强度,但对28 d强度影响并不显著。现场的工程实践表明,本文提出的弱碱激发磷渣固化方法可以有效实现磷渣的资源化再利用,在公路路基和路面基层填筑工程中具有很强的可推广性。