水泥基材料比热容测定及计算方法的研究

比热容是研究水泥基材料温度分布及温度变形的必要参数.将用以推定混凝土比热容的加权平均方法应用于混凝土凝结硬化后的组成及结构,并利用差示扫描量热仪对未水化水泥、硬化水泥浆体的比热容进行了测试分析.试验结果表明,用差示扫描量热法(DSC法)来测定水泥基材料的比热容简捷、准确、精确度高;所提出的混凝土比热容计算方法理论合理,计算结果与标准方法测定结果有很好的相关性.     

硬化混凝土中水泥用量的测定方法概述

水泥用量是混凝土配合比的重要参数,测定混凝土中的水泥用量对耐久性判断及配合比检查具有重要意义。硬化混凝土中的水泥用量可用化学分析方法及光学显微镜法测得。化学分析法又分为水泥溶解法与可溶性SiO2和CaO分析法,光学显微镜法包括荧光显微镜和扫描电镜。重点对化学分析方法的测定原理、试验方法及结果计算做了介绍,评价了各种方法的精密度与准确性,并总结了可能对测定造成影响的因素。     

掺加聚羧酸减水剂的混凝土微观结构表征

通过扫描电镜和压汞试验,表征和分析了聚羧酸减水剂对混凝土硬化水泥浆体、界面结构和水泥石孔结构的影响.结果表明,旱龄期的混凝土硬化水泥浆体和界面结构裂纹较宽,裂缝较多,龄期长,结构较密实;相同龄期掺有聚羧酸减水剂的混凝土硬化水泥浆体和界面过渡区结构裂缝数量和裂纹宽度均小于萘系减水剂;掺有聚羧酸减水剂少害孔和无害孔含量多,而有害孔和多害孔含量少.聚羧酸减水剂对混凝土结构优于萘系减水剂.     

含超细矿渣水泥的水化研究

用ＴＧ－ＤＴＡ，ＸＲＤ，ＳＥＭ研究了超细矿渣水泥的水化反应，并与硅酸盐水泥、含普通细度矿渣水泥的水化作了比较。结果表明：超细矿渣的水化程度较快、活性较高、可大量消耗水泥浆体中的Ｃａ（ＯＨ）２，生成更多的凝胶产物，因而改善了水泥石的微观结构，提高了水泥的物理力学性能。     

孔结构对水泥混凝土抗冻性的影响

用压汞法和扫描电子显微镜研究了冻融循环作用下硬化水泥浆体和混凝土宏观与细观结构的变化。结果表明,冻融以后硬化水泥浆体和混凝土中砂浆的孔隙率,特别是大于50 nm的毛细孔体积和微裂纹增加较多,导致硬化水泥浆体由密实结构向松散结构发展,最后导致粗骨料与砂浆分离。     

Performance of high strength concrete made with copper slag as a fine aggregate

This research study was conducted to investigate the performance of high strength concrete (HSC) made with copper slag as a fine aggregate at constant workability and to study the effect of superplasticizer addition on the properties of HSC made with copper slag. Two series of concrete mixtures were prepared with different proportions of copper slag. The first series consisted of six concrete mixtures prepared with different proportions of copper slag at constant workability. The water content was adjusted in each mixture in order to achieve the same workability as that for the control mixture. Twelve concrete mixtures were prepared in the second series. Only the first mixture was prepared using superplasticizer whereas the other eleven mixtures were prepared without using superplasticizer and with different proportions of copper slag used as sand replacement. The results indicated that the water demand reduced by almost 22% at 100% copper slag replacement compared to the control mixture. The strength and durability of HSC were generally improved with the increase of copper slag content in the concrete mixture. However, the strength and durability characteristics of HSC were adversely affected by the absence of the superplasticizer from the concrete paste despite the improvement in the concrete strength with the increase of copper content. All concrete mixtures did not meet the strength and durability design requirements due to the segregation and dryness of the concrete paste. Therefore it can be concluded that the use of copper slag as sand substitution improves HSC strength and durability characteristics at same workability while superplasticizer is very important ingredient in HSC made with copper slag in order to provide good workability and better consistency for the concrete matrix.     

煤矸石掺合料对水泥浆体结构与性能的影响

研究了煤矸石作为掺合料对水泥浆体强度及孔结构的影响。结果表明:与基准水泥浆体相比,煤矸石水泥浆体早期强度较低,但后期强度发展较快,低掺量(<30%)煤矸石水泥浆体后期(28d)强度可接近或达到基准水泥浆体强度;相同掺量条件下,与粉煤灰水泥浆体相比,煤矸石水泥浆体各龄期强度均较高;与矿粉水泥浆体相比,煤矸石水泥浆体早期强度较高,后期两者强度相当;与基准水泥浆体相比,煤矸石水泥浆体总孔隙率有所上升,但其孔径后期有所细化。     

组成及龄期对复合粉煤灰/水泥浆Cl~-结合性能的影响

研究了组成和龄期对粉煤灰/水泥浆体系硬化水泥浆Cl~-结合能力的影响。首先研究了组成和龄期对粉煤灰和水泥二组分体系硬化水泥浆Cl~-结合性能的影响,并且确定了Cl~-结合量最大的组成比。在该硬化水泥浆Cl~-结合量的组成比例下继续以钠钙硅玻璃粉和Ca(OH)_2混合组成取代水泥,并采用正交试验设计,探讨了玻璃粉掺量、细度和Ca(OH)_2掺量对Cl~-结合性能的影响。结果表明,14d和28d龄期时,粉煤灰对水泥取代量为50wt%的硬化水泥浆Cl~-结合能力达到极大值。正交试验结果表明,在10wt%、20wt%、30wt%的三个水平中,玻璃粉的掺量对硬化水泥浆的Cl~-结合量的影响最大,有使硬化水泥浆Cl~-结合能力降低的作用,而Ca(OH)_2具有使Cl~-结合能力增大的作用。但掺加了玻璃粉和Ca(OH)_2的粉煤灰-水泥浆体系硬化水泥浆Cl~-结合量随龄期的延长而下降。从正交试验的结果来看,少量玻璃粉的掺入并配合使用Ca(OH)_2,有望对掺粉煤灰硬化水泥浆的氯离子结合起到促进作用。     

The influence of gypsum ratio on the mechanical performance of slag cement accelerated by calcium sulfoaluminate cement

This paper investigates the use of calcium sulfoaluminate cement to improve the strength of high-grade slag cement composed of granulated blast-furnace slag and anhydrite. Two quaternary binders, composed of granulated blast-furnace slag, Portland cement, calcium sulfoaluminate clinker and calcium sulphate are compared with the reference. The only parameter studied is the gypsum ratio in the calcium sulfoaluminate cement. The results of compressive strength testing on standard mortar (in accordance with the European standard NF EN 196-1) indicate that the early and medium-term mechanical performances increase as the amount of gypsum increases. To explain this, pore size distribution in the mortar was studied and XRD, DTA–TGA and SEM techniques were applied to pure paste. The investigation showed that the hydration reactions of the individual constituents are dependent on the gypsum ratio and that its variation can lead to the formation of different hydrates.     

超高强混凝土用低水胶比浆体的水化热研究

采用自行改进的水化热测定系统,研究了粉煤灰、矿渣粉和水胶比对超高强混凝土用低水胶比浆体水化热和水化进程的影响规律.结果表明:掺10%(质量分数,下同)粉煤灰或矿渣粉不影响低水胶比浆体的水化进程;掺30%,50%粉煤灰或矿渣粉均使低水胶比浆体的水化温升和水化放热速率峰值明显降低,并延缓这些峰值出现的时间,且粉煤灰对水化进程的延缓效果优于同等掺量的矿渣粉;提高水胶比只能略微推迟浆体的水化温升和水化放热速率峰值出现的时间,使水化放热速率峰值有所增大,不会改变浆体温升曲线和放热速率曲线的形状.     

聚羧酸盐高效减水剂的研制(Ⅲ) ——减水剂的作用和应用研究

以自制的聚醚接枝丙烯酸/甲基丙烯磺酸钠共聚物作为高效减水剂,研究了该减水剂对水泥石结构的影响,讨论了减水剂掺量对水泥净浆流动性、水泥砂浆减水率、混凝土坍落度和坍落度损失以及水泥砂浆和混凝土抗压强度的影响,并与市售的萘系减水剂进行了比较.实验结果表明,聚羧酸盐高效减水剂对水泥净浆、水泥砂浆和混凝土有较好的减水作用,能显著提高上述材料的流动性和力学强度.     

Effect of copper slag as a fine aggregate on the properties of cement mortars and concrete

An experimental investigation was conducted to study the effect of using copper slag as a fine aggregate on the properties of cement mortars and concrete. Various mortar and concrete mixtures were prepared with different proportions of copper slag ranging from 0% (for the control mixture) to 100% as fine aggregates replacement. Cement mortar mixtures were evaluated for compressive strength, whereas concrete mixtures were evaluated for workability, density, compressive strength, tensile strength, flexural strength and durability. The results obtained for cement mortars revealed that all mixtures with different copper slag proportions yielded comparable or higher compressive strength than that of the control mixture. Also, there was more than 70% improvement in the compressive strength of mortars with 50% copper slag substitution in comparison with the control mixture. The results obtained for concrete indicated that there is a slight increase in density of nearly 5% as copper slag content increases, whereas the workability increased significantly as copper slag percentage increased compared with the control mixture. A substitution of up to 40–50% copper slag as a sand replacement yielded comparable strength to that of the control mixture. However, addition of more copper slag resulted in strength reduction due to the increase in the free water content in the mix. Also, the results demonstrated that surface water absorption decreased as copper slag content increases up to 50% replacement. Beyond that, the absorption rate increased rapidly and the percentage volume of the permeable voids was comparable to the control mixture. Therefore, it is recommended that up to 40–50% (by weight of sand) of copper slag can be used as a replacement for fine aggregates in order to obtain a concrete with good strength and durability requirements.     

高效减水剂与矿渣-钢渣复合掺合料的适应性研究

为了加快高性能矿渣-钢渣基复合掺合料的开发和应用,本工作研究了萘系减水剂和聚羧酸两类减水剂与钢渣和硅酸盐水泥三种矿粉之间的适应性。研究表明：对于矿渣、钢渣和硅酸盐水泥三种矿粉的单组分净浆,各种减水剂的饱和掺量在0．3％～1．1％之间。萘系高效减水剂掺量过大,胶砂和混凝土离析泌水严重,硬化体的强度显著下降。聚羧酸盐减水剂的突出优势是使净浆、砂浆和混凝土的流动度和稳定性俱佳,但混凝土强度低于掺萘系高效减水剂的混凝土。     

掺矿渣水泥水化反应特性的试验研究

通过抗压强度、非蒸发水量、矿渣反应度的试验测定及XRD分析,研究了掺矿渣水泥浆体的水化反应进程.结果表明,在相同龄期下,抗压强度随矿渣掺量与水胶比的增加呈减小趋势,矿渣的化学活性在28d前比较显著;掺矿渣水泥浆体的非蒸发水量高于纯水泥浆体非蒸发水量;矿渣的反应度则随其掺量的增加而减小,随水胶比的增加而增大.     

High performance concrete containing lower slag amount: A complex view of mechanical and durability properties

A wide set of parameters of concrete containing 10% of ground granulated blast furnace slag as Portland cement replacement involving basic material characteristics, mechanical and fracture-mechanical properties, durability characteristics, hydric and thermal properties and chloride binding characteristics is determined and compared with the parameters of reference Portland cement concrete with otherwise the same composition. The experimental results show that the replacement of Portland cement by even such a low amount of ground granulated blast furnace slag as environmental more friendly and still valuable alternative binder either affects positively or at least does not worsen in a significant way the substantial properties of hardened concrete mix. The mechanical and fracture-mechanical properties are found to be very similar as compared to the reference mix, the liquid water transport parameters of the mix containing slag are significantly better, the basic durability characteristics such as the frost resistance and corrosion resistance similar and very good, the resistance against de-icing salts slightly worse. These findings may be significant for the future use of slag in the countries where its available amount is decreasing and its more efficient use as a binder than it was common to date can appear necessary.     

提高水泥石—集料界面粘结强度的研究

研究了提高普通混凝土中水泥石集料界面粘结强度的途径,结果表明：在水泥中掺加超细矿渣粉,低温浅烧处理大理石集料,集料表面涂以硅烷偶联剂或丁苯胶乳,以低水灰比浆体包裹集料,均可使水泥石集料界面粘结强度得以大幅度提高．对以上提高水泥石集料界面粘结强度的机理进行了讨论．     

中性钠盐碱矿渣混凝土抗渗防水性能研究

研究了中性钠盐碱矿渣水泥的膨胀性及其混凝土的抗渗性。试验结果表明 ,中性钠盐碱矿渣混凝土具有良好的抗渗性和防水性能 ,可用于刚性建筑防水。     

矿物掺合料对干粉砂浆物理性能及孔结构的影响

研究了石灰石、矿渣和粉煤灰3种矿物掺合料分别对干粉砂浆的工作性能和力学性能的影响,并探讨了掺有掺合料时干粉砂浆的宏观力学性能和其微观孔结构之间的关系。结果表明:粉煤灰在掺量小于30%时能够提高砂浆的流动度,但掺量再继续增大时,砂浆流动度反而下降;掺入矿渣粉略能提高砂浆的流动度;石灰石粉在一定程度上降低砂浆流动度;同时石灰石粉能够提高砂浆的保水率,而矿渣粉和粉煤灰却降低砂浆的保水率。随着石灰石、矿渣和粉煤灰掺量的增加,砂浆28 d强度均有不同程度的降低,影响顺序为石灰石>粉煤灰>矿渣;与空白样相比,内掺占水泥质量50%的石灰石粉和矿渣粉时,28 d砂浆硬化体的总孔隙率分别增加10.2%、7.7%,而掺等量粉煤灰时总孔隙率则基本不变。以石灰石替代50%的水泥时,28 d砂浆硬化体中d>100 nm的多害孔增加24.0%,而以粉煤灰替代50%的水泥时,砂浆中多害孔基本不变,以等量的矿渣粉替代时d>100 nm的多害孔减少6.5%。     

Cement paste–epoxy adhesive interactions

In the field of civil engineering, the durability of concrete assemblies using adhesives is widely conditioned by the properties of the interface between the resin and the mineral support (concrete). In this context we studied first the molecular interactions at the interface between an epoxy resin and cement pastes by several approaches based on XPS and IR spectroscopies, DSC, and inverse gas chromatography (IGC). XPS showed evidence of crosslinking of the polymer at the surface of hardened cement pastes. XPS chemical shifts of the N1s peak from the adsorbed hardener testified for the existence of interfacial donor–acceptor interactions between the cement and hardener. Such a specific interaction is probably responsible for the increase in the of glass transition temperature (T_g) of the adhesive near the cement substrate surface. FTIR study of the interactions of the epoxy adhesive with the main hydrates taken separately (namely C–S–H, ettringite and portlandite) permitted to better understand the complex cement paste–adhesive interfacial system. The IGC-determined dispersive and acid–base components of the surface energy of the cement pastes were found to be depressed after coating, a result that correlates with surface chemical composition data. Small area XPS analysis of cement paste/adhesive interphase revealed, on a prototype of cement paste–adhesive joint, modifications of the Ca2p and N1s regions, which suggests that this zone is the locus of chemical reactions that favour mineral substrate–resin adhesion. Small area XPS firmly showed the existence of a diffuse interphase rather than a sharp cement paste–adhesive interface.     

Effect of slag on the rheology of fresh self-compacted concrete

The building industry is turning increasingly to the use of self-compacting concrete (SCC) in order to improve many aspects of building construction as SCC offers several advantages in technical, economic, and environmental terms. Fresh self-compacting concrete (SCC) flows into place and around obstructions under its own weight to fill the formwork completely and self-compact without any segregation and blocking. SCC mixes generally have a much higher content of fine fillers. The use of supplementary cementitious materials is well accepted because of the improvement in concrete properties and also for environmental and economical reasons. The present paper is an effort to quantify the influence of Algerian slag on the properties of fresh and hardened self-compacting concrete. The workability-related fresh properties of SCC were observed through slump flow time and diameter, V-Funnel flow time, J-Ring test, U-Box filling height and GTM sieve stability test. The only hardened property that was included in this study was the compressive strength. An optimum slag content of 15% seems to give a good SCC mixture with workability retention of about 60 min. A decrease in compressive strength with increase of slag content was obtained, but this decrease in compressive strength is less important at late ages (56 and 90 days after mixing).