水泥与磁化水

水以一定的流速通过磁场,由于切割磁力线使水的性质发生变化,称为水的磁化,这种水称为磁化水。据国内外试验研究,用磁化水搅拌水泥和混凝土可以提高强度、节约水泥,具有很好的经济效益。　　一、磁化水搅拌水泥和混凝土后的物理力学性质　　1、抗压强度　　原苏联的B·A·乌拉佐夫斯基等人,用互感器型的磁化设备进行了多年的研究,试验研究表明,利用磁化水搅拌的水泥,其强度有所提高,而且水泥块体的强度与磁场强度和水流通过磁场的速度有关。当水流经过磁场的速度为0.65米/分,磁场强度为160千安培每米时,磁化水与普通水拌制水泥试块相对…     

磁化水对凝石性能影响初探

经对比分析普通水和磁化水表明,水经磁化后部分物理化学性质发生改变。再通过大量试验,从凝石拌和物水化过程中磁化水对凝石性能的影响进行了研究。结果表明,磁化水可显著增大凝石净浆试块的抗压强度;采用磁化水拌制的砂浆试块强度和未磁化试样相比,早期抗压强度显著提高,后期强度增长率减缓。当水的磁化条件为磁场强度240mT、流速1.0m/s时,性能提高最为明显,用其拌制的凝石砂浆试块的28d抗压强度可提高10%左右。     

变频磁化水对混凝土抗裂性能影响的研究

为明确变频磁场产生的磁化水对混凝土抗裂性能的影响,采用圆环试验法,以混凝土开裂时刻为主要指标评价试件的抗裂性能;研究不同水流速度下,变频磁化水pH值、电导率、表面张力的变化规律。研究结果表明:变频磁化水混凝土抗压强度相比普通水混凝土提高4.33%～18.89%;与普通水相比,变频磁化水物理性质发生变化,其pH值、电导率、表面张力随水流速度变化呈不规则波动;变频磁化水能提高混凝土的抗裂能力,并存在一个最佳磁化参数,水流速度为80mL/s时,混凝土抗裂能力的增加幅度最大。     

磁化水钢纤维混凝土压拉性能试验与分析

为提高钢纤维混凝土的压拉性能,将磁化水技术应用到钢纤维混凝土中。对磁化水水流速度与钢纤维体积率进行正交试验,并制作标准试块进行压拉强度试验,研究磁化水对钢纤维混凝土压拉性能的影响。试验结果表明:磁化水能有效提高钢纤维混凝土的压拉强度,当磁场强度为285 mT,水流速度为2.1 m/s,钢纤维体积率为1.8%时,磁化水钢纤维混凝土的压拉强度与素混凝土相比,28天立方体抗压强度提高23.71%,劈裂抗拉强度提高43.63%。对磁化水增强钢纤维混凝土压拉性能机理进行分析可知,磁化水能通过提高混凝土压拉强度和改善钢纤维与混凝土间的界面粘结力,增强钢纤维混凝土的压拉性能。     

磁化水混凝土耐久性研究

本文主要从四个方面研究了磁化水对混凝土耐久性的影响：孔结构、抗冻融性能、干缩和抗氯离子渗透性能.磁化水由自来水通过自主研制的MW-Ⅰ型磁水器而获得.试验中采用的磁化参数为磁场强度810mT,流速0.73m/s,磁场长度580mm.结果显示,磁化处理使混凝土总孔隙率下降20.8%,各龄期的孔级配改善.导致磁化水混凝土的干燥收缩有较大改善,90天相对收缩下降6%.冻融循环和抗氯离子渗透性能有较大的提高.     

活化磺化麦草碱木质素高效减水剂性能的研究

以麦草碱木质素为原料,通过活化、磺化、缩合制备高效减水剂GSAL,研究其对水泥和混凝土性能的影响,并探讨了GSAL的减水作用机理。结果表明,水灰比为0.32,掺0.6%GSAL的水泥净浆流动度为248 mm,比掺奈系减水剂FDN的水泥净浆流动度大30 mm,水泥净浆流动度120 min后仅损失17.3%,水泥净浆的终凝时间延长2～3 h,混凝土减水率达24.5%,比FDN高3.7%,GSAL使混凝土3 d、28 d抗压强度比分别达到178%和154%,比掺FDN分别提高36%和33%。通过表面物化性能研究表明,GSAL对水泥的减水分散作用主要是由于其对水泥颗粒具有良好的润湿作用、适当的气泡润滑作用以及在水泥颗粒表面形成了较强的静电斥力。     

柠檬酸钠对普通硅酸盐水泥与硫铝酸盐水泥复配体系的性能研究

本文通过水泥净浆、砂浆试验,研究了柠檬酸钠对普通硅酸盐水泥与硫铝酸盐水泥复配体系净浆的凝结时间、砂浆流动度和拉伸粘结强度、水泥水化产物的影响。研究表明,柠檬酸钠通过抑制铝酸钙、硫铝酸钙的早期水化,延缓复配体系的凝结时间、改善砂浆流动性,柠檬酸钠掺量为1.2%时,初凝时间与终凝时间分别为106 min、118 min,砂浆的流动度达到最大值为157 mm;柠檬酸钠使水泥后期水化更充分,增加钙矾石的生成量,提高砂浆拉伸粘结强度,柠檬酸钠掺入量为1.0%时,砂浆拉伸粘结强度为0.54 MPa。     

水泥砂浆强度和阻尼增强掺料及试验

通过在水泥净浆或砂浆中掺加不同比例的增强掺料 (乳胶、硅粉和甲基纤维素 ) ,比较了各种掺料对水泥砂浆构件强度和对水泥净浆构件阻尼比的影响效果 ,另外初步探讨了各种掺料的作用机理。试验表明 :掺乳胶水泥净浆构件的阻尼比是基准水泥净浆构件阻尼比的 2～ 3倍 ,掺硅粉水泥砂浆构件比基准水泥砂浆构件强度提高 30 %～ 5 0 % ,而甲基纤维素在提高构件阻尼比和强度方面都很有效     

高活性矿物掺合料浆在混凝土中的应用

研究了高活性矿物掺合料浆的制备过程及其对净浆基本性能、水化热、化学收缩及混凝土制品强度的影响.结果表明:高活性矿物掺合料浆按固含量替代10%～30%的水泥可配制出C30～C50的高性能混凝土,其工作性及后期性能均达到了国家标准,实现了低水化热、低收缩、低成本的应用效果.     

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。     

用磁化技术提高凝石胶凝材料性能的试验研究

采用磁化技术对凝石拌和水进行磁化预处理,可显著提高凝石胶凝材料的理化性能.与未磁化试样相比,采用磁化水拌制的砂浆试块早期抗压强度提高明显,后期有所减缓.水的磁化条件以磁场强度240 mT、水速1.0 m/s时提高最为明显,28 d抗压强度可提高10%左右.     

Effects of portland composite and composite cements on durability of mortar and permeability of concrete

In this study, the effects of Portland composite and composite cement on the properties of cement paste, durability of mortar and permeability of concrete were investigated. The results were compared with reference mixture of cement paste, mortar and concrete made with Portland cement. The ratio of water to cementitious materials (W/C_m) in cement paste, mortar and concrete mixtures were determined in a way that all the similar mixtures had the same workability. Flexural tensile and compressive strength of mortar samples containing Portland Composite and Composite cement were determined at various ages. In cement paste samples, the shortest and longest setting time was obtained in samples made with Portland and composite cement, respectively. Also, maximum amount of volume expansion was found in the sample made with Portland composite cement. Mortar samples made with Portland composite and composite cement had lower strength values than the reference mortar mixture at early ages but at 28 days and later ages they had higher strength values than the reference mixture. In durability tests, there was no loss of weight and cracks in mortar mixture samples made with Portland composite and composite cement when they were held in microthiol, Na₂SO₄ and MgSO₄ solutions. Also, no water leakage was observed through the concrete samples made with Portland composite and composite cement when they were held under five-bar pressurized water.     

火山灰质粉对砂浆性能与微结构的影响

为加强我国区域火山灰资源利用，为工程建设提供优质建筑原材料，选取泸定桥、泸霍两地典型火山灰弃岩资源磨制成火山灰材料，研究不同种类和粒径的火山灰质材料基本特性。采用火山灰等质量取代水泥制备火山灰-水泥砂浆，分析火山灰对水泥砂浆力学性能与微观结构的影响及机理。结果表明，随着火山灰粒径（d50）的降低，砂浆各个龄期的抗压强度和火山灰活性指数升高，但浆体的流动性降低。掺入火山灰会导致浆体的孔隙率增大和孔结构粗化。当火山灰粒径相似时，泸定桥组砂浆的28d活性指数小于泸霍组。此外，蒸汽养护可以促进各组砂浆的抗压强度和活性增长。     

Utilization of separator bag filter dust for high early strength cement production

This paper presents the feasibility of incorporating ultra-fine particles collected in the separator bag filter during the process of manufacturing cement (SBFC) as an substitution material for cement. Approximately 2.5% of SBFC is produced during OPC manufacturing process. Also, the average size of SBFC particles is about 5 μm, the average size of OPC particles is about 14 μm. This method does not require additional processes needed in the existing processes to manufacture high early strength cement such as modifying mineral components and adjusting the firing temperature. Moreover, it can also solve the issue of efficiency decrease resulted from the increase of the grinding time applied in the existing process of manufacturing microcement. In order to investigate the characteristic properties of this cement mixture, cement blends have been produced by using different amounts of SBFC. While the blaine value of 100% SBFC was significantly higher (6953 cm²/g) than that of Ordinary Portland Cement (OPC), its chemical composition showed no significant difference. Cement paste, mortar mixtures have been prepared by using cement blends incorporating 0, 50 and 100% SBFC by weight. Flowability, setting time and compressive strength tests has been performed. Test results showed that substitution of SBFC negatively affect the flowability of cement paste and mortar mixtures. Moreover, setting times shortened, compressive and flexural strength values increased by the substitution of SBFC. Finally, microstructure analysis of cement paste samples showed that incorporation of SBFC reduced the internal porosity by 9% as determined by the proposed method. The internal porosity of paste was measured by mercury intrusion porosimetry (MIP). The compressive strength and bending strength of mortar were higher in the order of 100, 50 and 0% SBFC mixed.     

自制硅酸盐对传统糯米灰浆性能的影响

采用灰浆性能表征和扫描电镜(SEM)、X射线衍射(XRD)、红外光谱(FTIR)等技术手段,探讨了自制硅酸盐对糯米灰浆的影响及作用机理。结果表明:自制硅酸盐对糯米灰浆的表面硬度、抗压强度、耐冻融性和耐水性均有一定程度的改善。6%自制硅酸盐糯米灰浆的综合性能最佳,其66d抗压强度高达1.41 MPa,耐冻融性较之空白样品提高了133%,耐水性能提高了43.8%。改性糯米灰浆耐水性等性能的提高,可能与灰浆中水化硅酸钙的生成有关。     

在水热作用下废弃水泥基材料的再生研究

对水热作用下废弃水泥基材料的再生进行了研究.测试再生废弃水泥基材料的抗压强度、表观密度和吸水率等随氢氧化钙掺量的变化.结果表明,在废弃水泥净浆中掺加氢氧化钙对抗压强度增加不明显;在废弃水泥胶砂中当氢氧化钙掺量为15%时试样的抗压强度最高;在废弃混凝土中当氢氧化钙掺量为10%时试样的抗压强度最高.利用这种再生方法,可以充分利用废弃水泥基材料中的剩余胶凝材料和硅质材料.     

Estimation of uniaxial compressive strength from point load strength,Schmidt hardness and P-wave velocity

Uniaxial compressive strength is considered one of the most important parameters in the characterization of rock material in rock engineering practice. The study investigated correlations between uniaxial compressive strength and point load index, P-wave velocity and Schmidt hardness rebound number together with the effects of core diameter size. A total of 150 core samples at five different diameters (54, 48, 42, 30 and 21 mm) were obtained from sandstone, limestone and cement mortar. Ten saturated samples at each diameter (length:diameter ratio 2:1) were prepared from each of the three materials. The best correlations were found between uniaxial compressive strength and point load or Schmidt hammer values. The closest relationship was observed for the 48 mm diameter cores.      

利用碱性电解水激发砂浆中矿粉活性的研究

利用碱性电解水制备矿粉砂浆,研究了不同取代率矿粉对砂浆工作性和力学性能的影响,结合XRD分析,评价了利用碱性电解水激发矿粉的活性和改善矿粉砂浆性能的可行性。结果表明:碱性电解水矿粉砂浆的工作性和力学性能均优于自来水矿粉砂浆;当矿粉取代率为20%时,碱性电解水矿粉砂浆的28 d抗折强度和抗压强度较自来水矿粉砂浆分别提高了11.9%和23.5%;碱性电解水矿粉砂浆中存在多钙钾石膏和钾长石,且水化硅酸钙和铝酸钙矿物的衍射峰显著强于自来水矿粉砂浆。     

再生细骨料干混砂浆力学性能试验研究

利用含红砖的再生细骨料100%替代天然砂,制备生态干混砂浆,研究了用水量、再生粉料掺量和外加剂掺量对干混砂浆力学性能的影响。结果表明:当再生粉料和外加剂掺量不变时,砂浆强度随着用水量的增大而降低,但56 d强度增长率反而增大;当再生粉料掺量和用水量不变时,外加剂掺量的增加对砂浆各龄期的强度均有负面影响;当外加剂掺量和用水量不变时,再生粉料掺量为20%时,对应的砂浆强度最大,低于或高于此掺量均会使砂浆强度降低;含红砖再生细骨料干混砂浆的后期强度(56 d)仍有较大提升空间。     

Assessing compressive strengths of mortar and concrete from digital images by machine learning techniques

Compressive strength is the most important metric of concrete quality. Various nondestructive and semi-destructive tests can be used to evaluate the compressive strength of concrete. In the present study, a new image-based machine learning method is used to predict concrete compressive strength, including evaluation of six different models. These include support-vector machine model and various deep convolutional neural network models, namely AlexNet, GoogleNet, VGG19, ResNet, and Inception-ResNet-V2. In the present investigation, cement mortar samples were prepared using each of the cement:sand ratios of 1:3, 1:4, and 1:5, and using the water:cement ratios of 0.35 and 0.55. Cement concrete was prepared using the cement:sand:coarse aggregate ratios of 1:5:10, 1:3:6, 1:2:4, 1:1.5:3 and 1:1:2, using the water:cement ratio of 0.5 for all samples. The samples were cut, and several images of the cut surfaces were captured at various zoom levels using a digital microscope. All samples were then tested destructively for compressive strength. The images and corresponding compressive strength were then used to train machine learning models to allow them to predict compressive strength based upon the image data. The Inception-ResNet-V2 models exhibited the best predictions of compressive strength among the models tested. Overall, the present findings validated the use of machine learning models as an efficient means of estimating cement mortar and concrete compressive strengths based on digital microscopic images, as an alternative nondestructive/semi-destructive test method that could be applied at relatively less expense.