基于正交试验的掺CWCPM的小型混凝土配合比优化设计

为提高建筑垃圾废砖再生利用率,将废旧粘土砖磨细成粉,并与其他工业废渣复合形成建筑垃圾复合粉体材料(Construction waste composite powder materials,以下简称CWCPM)。采用正交试验设计方法对掺CWCPM的C20~C30小型混凝土预制构件配合比进行试验研究,探讨水灰比、CWCPM掺量和砂率对混凝土工作性和力学性能的影响,并推荐了混凝土较优配合比。同时,借助XRD微观测试手段研究CWCPM对混凝土微观性能的影响。结果表明,水灰比仍是影响混凝土工作性与抗压强度的主要因素,其次为CWCPM掺量,砂率对混凝土各项性能的影响最小,CWCPM掺量对混凝土90d抗弯拉强度的影响最为显著。微观测试结果表明,CWCPM掺入后并未生成新的水化产物,但改变了水泥基材料的水化产物数量,进而影响混凝土的宏观性能。     

基于孔结构参数的掺CWCPM混凝土抗压强度预测模型的建立

为提高废旧粘土砖活性,将废砖破碎、粉磨后进行活性激发,制得建筑垃圾复合粉体材料(Construction waste composite powder materials,CWCPM)。为进一步研究CWCPM作为混凝土掺合料的可行性,首先研究不同因素对掺CWCPM混凝土抗压强度及孔结构参数的影响规律。然后,分析孔隙参数、孔径分布参数与抗压强度之间的关系。最后,基于多元回归理论,建立同时考虑孔隙参数与孔径分布参数的掺CWCPM的混凝土的抗压强度-孔结构关系模型。结果表明,CWCPM的掺入降低了混凝土7 d抗压强度。当CWCPM掺量不高于30%时,试件28 d强度高于基准试件,CWCPM可作为混凝土掺合料进行再生利用。总孔隙面积越大,总孔隙量、平均孔径和孔隙率越小,混凝土抗压强度越高。抗压强度与毛细孔及大孔数量均为负相关关系,而与凝胶孔及过渡孔含量之间未表现出显著的定量关系。考虑孔隙参数与孔径分布的抗压强度-孔结构模型可准确地预测掺CWCPM的混凝土的抗压强度。     

碱激发和复合激发下建筑垃圾砖粉活性研究

为提高建筑垃圾废砖再生利用率,采用砂浆力学测试手段研究了建筑垃圾砖粉活性和碱激发、复合激发对建筑垃圾砖粉活性的影响,并借助扫描电镜和热分析方法对建筑垃圾砖粉、建筑垃圾复合粉体材料的颗粒形貌、水化产物组成等进行了研究。结果表明:建筑垃圾砖粉活性较小,当掺量大于20%时,砂浆强度随其掺量的增加直线下降;不同碱激发剂对建筑垃圾砖粉有不同的激发效果,Ca(OH)2激发效果最好,NaOH次之,Na2SiO3·9H2O激发效果最差;复合形成的建筑垃圾复合粉体材料具有较好的活性,当其掺量不超过40%时,砂浆28d抗压强度高达50 MPa。微观分析结果表明:建筑垃圾复合粉体材料比砖粉具有更好的颗粒级配,在其水化过程中降低了稳定性较差的Ca(OH)2含量,提高了水泥石密实度,是一种经济、环保的新材料。     

两种乳胶粉对三元胶凝体系饰面砂浆性能的影响

研究了乙烯-醋酸乙烯共聚物(乳胶粉A)及乙烯-醋酸乙烯-丙烯酸酯三元共聚物(乳胶粉B)对铝酸盐水泥-硅酸盐水泥-半水石膏三元体系饰面砂浆抗泛白性、耐沾污性、吸水性及力学性能的影响。结果表明,乳胶粉B对各项性能的作用效果均优于乳胶粉A。乳胶粉B掺量为0~6%时砂浆7d泛白等级为0级;适当掺量的乳胶粉B能改善砂浆的耐沾污性,在其掺量大于等于12%时,砂浆的耐沾污性优于未掺乳胶粉的砂浆;乳胶粉A的掺量为3%~9%时,乳胶粉B掺量为3%~15%时可改善砂浆的吸水性;乳胶粉A能提高砂浆抗折强度及拉伸粘结强度,但会降低砂浆的抗压强度,而乳胶粉B能同时提高砂浆的抗折强度、抗压强度及拉伸粘结强度。     

再生橡胶颗粒对自流平砂浆力学性能影响的试验研究

分别研究了再生橡胶颗粒掺量、颗粒粒径及乳化沥青复合对自流平砂浆力学强度、折压比等力学性能参数的影响规律;提出了再生橡胶颗粒在水泥基材料体系中的三大作用效应,并分析了相应的影响机理。结果表明,再生橡胶颗粒掺量、颗粒粒径对自流平砂浆的抗折强度、抗压强度以及折压比存在较为显著的影响,当橡胶颗粒等量取代骨料体积15%时,体系的折压比达到最大,且橡胶颗粒与乳化沥青复掺后可进一步显著提高试件的折压比;与普通振捣密实成型砂浆体系相比,橡胶颗粒对自流平砂浆力学强度的影响未有明显的不同。     

固化剂对环氧树脂砂浆修补材料性能的影响

主要探讨了固化剂的掺量、存贮时间及环境因素对环氧树脂砂浆性能的影响.研究结果表明,固化剂掺量为30份/100份环氧树脂时,环氧树脂砂浆早期强度发展很快,3d抗折强度为7.2MPa,抗压强度为24.4MPa;后期强度发展稍慢,90d抗压强度为53.1MPa.固化剂掺量为10份/100份环氧树脂时,后期强度很大,90d抗压强度为96.9MPa,但早期强度发展较慢,固化时间长.40℃环氧树脂砂浆固化迅速,3d抗折强度即高于12.5MPa,抗压强度可达48.1MPa.     

橡胶骨料碱性砂浆孔结构与抗压性能非线性回归模型

废旧轮胎的弃置会导致诸多环境问题，而粉碎制得的橡胶粉可在建筑砂浆中替代细骨料。砂浆中橡胶骨料的掺量和粒径是橡胶混凝土强度的主要影响因素，利用碱激发矿渣材料可替代普通硅酸盐水泥，提升砂浆的环境友好性。研究多因素耦合作用对橡胶骨料砂浆抗压性能的影响，通过测试砂浆的抗压强度，对试验结果进行显著性分析及多元非线性回归，建立了多因素与砂浆抗压强度的多元非线性回归模型。对砂浆试样进行细观孔隙测量和SEM表征，探究橡胶骨料对砂浆抗压强度的劣化机制。结果表明：砂浆中橡胶骨料掺量的提升会造成砂浆抗压强度的下降，40vol%骨料替代率下碱激发类砂浆抗压强度均值相比对照组降低了49.93%，硅酸盐类降低了66.62%；在碱激发类砂浆的高碱性环境下，使用0.38 mm粒径橡胶骨料的砂浆抗压强度均值为对照组的69.65%，取得试验组中最优值；而在硅酸盐类砂浆的低碱性环境中，随着橡胶骨料粒径的减小，砂浆抗压强度均值由对照组的61.46%降至37.98%。     

硅烷复合乳液对水泥砂浆干燥收缩性能及力学性能的影响

将氧化石墨烯/异丁基三乙氧基硅烷复合乳液(GO/lBTS复合乳液)和正硅酸四乙酯/异丁基三乙氧基硅烷复合乳液(TEOS/lBTS复合乳液)分别内掺到水泥砂浆中,研究了两种硅烷复合乳液在不同掺量下对砂浆在养护过程中的干燥收缩性能、水分散失和力学性能的影响.研究结果表明:GO/lBTS复合乳液能有效抑制砂浆的干燥收缩和水分散失,当掺量为2％时,砂浆干燥收缩量和水分散失量达到最小,而且力学强度达到平均最高;TEOS/lBTS复合乳液对砂浆干燥收缩和水分散失的抑制作用不明显,但是当掺量为2％时,力学性能达到最大,抗压强度和抗折强度分别提高了5％和17％;但两种硅烷复合乳液掺量不宜超过水泥质量的3％.通过SEM、EDS测试发现,GO/lBTS复合乳液会在砂浆内部形成一层分散均匀的絮状结构.另外,红外光谱测试结果表明,硅烷复合乳液通过化学键与水泥基材料相结合.     

纳米二氧化硅对丁苯共聚物/硫铝酸盐水泥复合砂浆物理力学性能的影响

为厘清纳米二氧化硅(NS)和丁苯共聚物乳液(SB)在硫铝酸盐(CSA)水泥中的协同作用，同时解决SB/CSA水泥复合砂浆凝结时间长、抗压强度低的问题，采用NS和SB对CSA水泥砂浆进行复合改性，研究改性复合砂浆物理力学性能随NS掺量的变化，并通过测定水化放热及水化产物分析NS在SB/CSA水泥复合砂浆中的作用机制。结果表明：NS可有效缩短SB/CSA水泥复合砂浆的凝结时间，提高其抗压强度，并与SB对CSA水泥砂浆抗折强度提升具有协同作用；NS最佳掺量为1.5%,此时与不加NS的纯SB改性砂浆相比，28 d抗压和抗折强度分别提高了28%、30%。同时，掺入NS会降低复合砂浆的流动度，提高表观体积密度，降低含气量和干燥收缩率，并略微降低毛细孔吸水率。NS可通过促进无水硫铝酸钙和硫酸钙反应，进一步加快SB/CSA水泥复合浆体的水化进程，提高钙矾石的含量，从而缩短凝结时间并提高力学强度。     

蒸压养护对废玻璃粉复合砂浆力学性能的改善

为改善玻璃粉复合砂浆力学性能,参考蒸压加气砖的制备条件,用蒸压养护对比常温养护,以不同比例废玻璃粉取代水泥制备玻璃粉复合水泥砂浆;结合X射线衍射分析、扫描电镜等方法研究废玻璃粉复合砂浆力学性能的变化。结果表明:常温养护下,废玻璃粉复合砂浆强度随取代比例的提高而降低;蒸压养护下,玻璃粉复合砂浆强度随取代比例的提高而呈"凸"型变化,最优掺量为30%(质量分数),其60 d抗压强度超过基准水泥砂浆17. 6%,建议制备玻璃粉复合砂浆中玻璃粉的取代比为30%。     

磁场诱导定向碳纤维增强水泥砂浆的力学性能

首次利用磁场诱导定向技术,制备了具有明显择优取向的碳纤维增强水泥砂浆,表征与测试了不同水灰比、龄期和纤维掺量的水泥砂浆的碳纤维取向、抗压和劈裂抗拉强度,研究了碳纤维的取向性对力学性能提升效果的影响。结果表明:水灰比、纤维掺量对碳纤维的取向性有显著影响;相较于无择优取向的普通碳纤维增强水泥砂浆,经磁场诱导定向的碳纤维增强水泥砂浆的劈裂抗拉强度有显著增加,而抗压强度无明显变化;相同水灰比下,纤维取向和纤维掺量是影响定向碳纤维增强水泥砂浆劈裂抗拉强度的主要因素。其中,定向碳纤维增强水泥砂浆劈裂抗拉强度增强效率的最佳碳纤维掺量为水泥的0.50%。      

氧化石墨烯增强水泥基复合材料的力学性能及微观结构

本文采用改进的Hummers法制备了氧化石墨烯（Graphene oxide,GO）悬浮液,通过FTIR、XRD和AFM等测试技术对GO晶体结构和尺寸形态进行了表征,考察了GO掺量和水灰比的变化对GO增强水泥基复合材料力学性能和微观结构的影响。结果表明：GO增强水泥基复合材料抗折抗压强度随GO掺量增加而先提高后降低,且对于抗折强度增强效果远超过抗压强度,当GO掺量为0.03%时,抗折强度达到最大值13.72 MPa;高水灰比条件下掺入GO对水泥胶砂强度的提高更显著;通过SEM对GO增强水泥基复合材料微观结构进行表征,发现GO能够优化水泥水化产物的微观结构形态,细化晶体尺寸,形成更加致密均匀的网络结构,从而改善水泥基复合材料的宏观性能。     

道路非开挖注浆加固补强材料研究进展

针对目前道路非开挖注浆加固中注浆材料选择缺乏明确的参考依据,系统地梳理了目前常用道路注浆材料的类型及配比,基于统计分析推荐了水泥基及地聚物注浆材料配比,确定了高聚物注浆材料密度对吸水率和抗压强度的影响规律。结果表明,水泥净浆注浆材料的推荐水灰比为0.46~0.67,水泥砂浆的推荐配比为m水泥∶m水∶m砂=1∶(0.46~0.59)∶(0.31~0.73);地聚物注浆材料水玻璃模数、水灰比和水玻璃质量分数推荐值分别为2.3~3.1、0.49~0.67和7.27%~9.73%;随着高聚物固化物密度增大,其抗压强度逐渐增大,吸水率逐渐减小。     

响应面方法优化碱激发矿渣-石粉水泥砂浆的研究

基于响应面中的中心复合试验法,选择碱含量和石灰石粉含量作为配合比变量,制备碱激发矿渣-石粉水泥砂浆,并研究其不同龄期的力学强度。通过数据处理得到各变量与抗折、抗压强度的响应曲面,分析了各变量对碱激发矿渣-石灰石粉水泥砂浆强度的影响规律,建立了各龄期强度的响应面模型,为现场不同龄期的砂浆强度预测提供了科学的方法。结果表明,当Na2O含量为8.27%(质量分数,下同)、石灰石粉含量为14.02%时,各组分能充分发挥协同作用,保证良好的力学性能,且响应面法是一种有效优化碱激发水泥砂浆组分的方法。     

具有大规模规整致密花状微观结构形貌高/超高性能氧化石墨烯/水泥基复合材料

通过掺入氧化石墨烯(GO)及调控水灰比制备了高性能及超高性能水泥基复合材料,当水灰比为0.26及GO掺量为0.03%和0.05%时,水泥基复合材料的抗压强度和抗折强度分别为125.6 MPa、146.7 MPa和15.6 MPa、18.3 MPa。当水灰比为0.18及GO掺量为0.03%和0.05%时,水泥基复合材料的抗压强度和抗折强度分别为168.6 MPa、181.3 MPa和26.9 MPa、29.4MPa。水泥基复合材料的抗渗透、抗冻融、抗碳化等性能得到了显著提高。通过SEM观察水泥基体的微观形貌,发现水泥水化产物成为了形状规整的水化晶体,并且交织交联成为规整致密的花状微观形貌。XRD结果表明,规整形状水化晶体是由多种水泥水化晶体复合杂化形成的复合晶体。     

The use of oil shale ash in Portland cement concrete

An experimental investigation was undertaken to study the potential use of Jordanian oil shale ash (OSA) as a raw material or an additive to Portland cement mortar and concrete. Different series of mortar and concrete mixtures were prepared at different water to binder ratios, and different OSA replacements of cement and/or sand. The compressive strength of mortar and concrete specimens, cured in water at 23 °C, was determined over different curing periods which ranged from 3 to 90 days. The results of these tests were subjected to a statistical analysis. Equations were developed by regression analysis techniques to relate the effect of batch constituents on the strength developments of OSA mortars and concretes. The models were checked for accuracy by comparing their predictions with actual test results.The obtained results indicated that OSA replacement of cement, sand or both by about 10% (by wt) would yield the optimum compressive strength, and that its replacement of cement by up to 30% would not reduce its compressive strength, significantly. It was found that OSA on its own possesses a limited cementitious value and that its contribution to mortar or concrete comes through its involvement in the pozzolanic reactions. The statistical model developed showed an excellent predictability of the compressive strength for mortar and concrete mixes.     

Grey correlation analysis between strength of slag cement and particle fractions of slag powder

The particle size distributions of slag powder were investigated by Laser Scatter equipment. The influence of particle fractions of slag powder on the compressive strength of slag cement composed of 50% slag powder and 50% Portland cement was also studied by the method of grey correlation analysis. The results indicated that the volume fraction of particles 5–10 μm had a maximum positive effect on the mortar compressive strength of slag cement at 7 d and the volume fraction of particles 10–20 μm had a maximum positive effect on the mortar compressive strength at 28 d, whereas the volume fraction of particles larger than 20 μm had a negative effect on the mortar compressive strength at 7 and 28 d.     

Influence of mix proportions on rheology of cement grouts containing limestone powder

In this paper the parameters of cement grout affecting rheological behaviour and compressive strength are investigated. Factorial experimental design was adopted in this investigation to assess the combined effects of the following factors on fluidity, rheological properties, induced bleeding and compressive strength: water/binder ratio (W/B), dosage of superplasticiser (SP), dosage of viscosity agent (VA), and proportion of limestone powder as replacement of cement (LSP). Mini-slump test, Marsh cone, Lombardi plate cohesion meter, induced bleeding test, coaxial rotating cylinder viscometer were used to evaluate the rheology of the cement grout and the compressive strengths at 7 and 28 days were measured. A two-level fractional factorial statistical model was used to model the influence of key parameters on properties affecting the fluidity, the rheology and compressive strength. The models are valid for mixes with 0.35–0.42 W/B, 0.3–1.2% SP, 0.02–0.7% VA (percentage of binder) and 12–45% LSP as replacement of cement. The influences of W/B, SP, VA and LSP were characterised and analysed using polynomial regression which can identify the primary factors and their interactions on the measured properties. Mathematical polynomials were developed for mini-slump, plate cohesion meter, inducing bleeding, yield value, plastic viscosity and compressive strength as function of W/B, SP, VA and proportion of LSP. The statistical approach used highlighted the limestone powder effect and the dosage of SP and VA on the various rheological characteristics of cement grout.     

Performance of Portland limestone cements in mortar prisms immersed in sulfate solutions at 5 °C

The results of a test programme to investigate the sulfate resistance of mortars, immersed up to 12 months at 5 °C in magnesium sulfate and sodium sulfate solutions, is described. The mortars were prepared from four cements; a Portland cement, a sulfate-resisting Portland cement and two Portland limestone cements containing 15% by mass of an oolitic limestone and a carboniferous limestone. The mortar specimens were subject to BS 5328 Class 4A and 4B sulfate exposure conditions. These are the highest classes for concretes prepared using sulfate-resisting Portland cement (SRPC) before surface protection is required and are two and three classes higher than those recommended for concretes prepared using Portland cement (PC) and Portland limestone cement (PLC), respectively. Two free water-cement ratios were used, 0.5 and 0.75. Performance was monitored by visual assessment, expansion and changes in flexural and compressive strengths.At a free water-cement ratio of 0.75, the PC mortars and PLC mortars exhibited visually very severe attack with the former showing expansion and reductions in strength, and the latter mainly reductions in strength. At a free water-cement ratio of 0.50 both the PC mortars and PLC mortars showed slight/moderate to severe visual attack, the degree of deterioration appearing slightly greater in the PLC mortars, more especially those made with oolitic limestone. The PLC mortars also exhibited reductions in compressive failure load. The SRPC mortars exhibited little visual deterioration, no expansion, a small increase in flexural strength and no significant reductions in compressive strength. At a free water-cement ratio of 0.75 substantial amounts of thaumasite, together with ettringite was present in the surface layers of the deteriorated PLC mortars whilst ettringite was present in the surface layers of the deteriorated PC mortars. It is concluded that mortars made with a PC with a C₃A content of about 10% by mass were broadly similar in their vulnerability to sulfate attack at 5 °C as PLC mortars containing 15% limestone by mass, although the mode of attack was different.