Effect of Partial Replacement of Fly Ash by Decoration Waste Powder on the Fresh and Mechanical Properties of Geopolymer Masonry Mortar

This study aims to investigate the feasibility of using decoration waste powder(DWP)as a partial replacement for fly ash(FA)in the preparation of geopolymer masonry mortar,and to examine the effect of different DWP replacement rates(0%-40%)on the fresh and mechanical properties of the mortar.The results showed that each group of geopolymer masonry mortar exhibited excellent water retention performance,with a water retention rate of 100%,which was due to the unique geopolymer mortar system and high viscosity of the alkaline activator solution.Compared to the control group,the flowability of the mortar containing lower contents of DWP(10%and 20%)was higher.However,as the DWP replacement rate further increased,the flowability gradually decreased.The DWP could absorb the free water in the reaction system of geopolymer mortar,thereby limiting the occurrence of geopolymerization reaction.The incorporation of DWP in the mortar resulted in a decrease in compressive strength compared to the mortar without DWP.However,even at a replacement rate of 40%,the compressive strength of the mortar still exceeded 15 MPa,which met the requirements of the masonry mortar.It was feasible to use DWP in the geopolymer masonry mortar.Although the addition of DWP caused some performance loss,it did not affect its usability.

Experimental study on the seismic performance of masonry wall reinforced by cement mortar and polypropylene band

Since masonry structures are prone to collapse in earthquakes,a novel joint reinforcement method with a polypropylene band(PP-band)and cement mortar(CM)has been put forward.Compared with the common reinforcement methods,this method not only facilitates construction but also ensures lower reinforcement cost.To systematically explore the influence of joint reinforcement on the seismic performance of masonry walls,quasi-static tests were carried out on six specimens with different reinforcement forms.The test results show that the joint action of PP-band and CM can significantly improve the specimen′s brittle failure characteristics and enhance the integrity of the specimen after cracking.Compared with the specimen without reinforcement,each of the seismic performance indexes of the joint reinforced specimen had obvious improvement.The maximum increased rate about peak load and ductility of the joint reinforced specimen is 100.6%and 233.4%,respectively.

Bond-slip constitutive relationship between bars and mortar for block masonry

Ten specimens were tested in this paper in order to study the bond behavior and the process of force transfer when bars adhered to mortar. The development of the bond stress between bars and mortar was calculated. Test results show that the maximum bond-stress is not influenced by the bar bond length and increases as the increased splitting strength of mortar for block. The local bond stress-slip curve was obtained. Then,based on the regressive analysis of test data,two bond shearing stress-slip constitutive models between bars and mortar were proposed. The models can be used in the numerical simulation or finite element analysis and provide references for the improvement of the corresponding design codes.

Numerical simulation on the seismic performance of retrofitted masonry walls based on the combined finite-discrete element method

Due to the long construction life,improper design methods,brittle material properties and poor construction techniques,most existing masonry structures do not perform well during earthquakes.The retrofitting method using an external steel-meshed mortar layer is widely used to retrofit existing masonry buildings.Assessing the seismic performance of masonry walls reinforced by an external steel-meshed mortar layer reasonably and effectively is a difficult subject in the research field of masonry structures.Based on the combined finite-discrete elements method,the numerical models of retrofitted brick walls with four different masonry mortar strengths by an external mortar layer are established.The shear strength of mortar and the contact between the retrofitted mortar layer and the brick blocks are discussed in detail.The failure patterns and load-displacement curves of the retrofitted brick walls were obtained by applying low cycle reciprocating loads to the numerical model,and the bearing capacity and the failure mechanism of the retrofitted walls were obtained by comparing the failure patterns,ultimate bearing capacity,deformability and other aspects with the tests.This study provides a basis for improving the seismic strengthening design method of masonry structures and helps to better assess the seismic performance of masonry structures after retrofitting.

Dynamic Modulus of Elasticity of Some Mortars Prepared from Selected Jordanian Masonry Cements

In light of the highly demanding cement market in Jordan, comprehensive studies should be undertaken to investigate the properties of the different cement types. This paper studies the Dynamic modulus of elasticity (DME) at 2, 7 and 28 days in mortars using six cement Jordanian types with CaO contents less than that of the ordinary Portland cements. It was found that the DME has strong relation with compressive strength. At the age of 28 days the mortars had some different values of DME. One important result of our work is that DME at the age of 28 days can be derived from those of the two days mixes. To account for the differences in dynamic modulus of elasticity with time, it is highly recommended to study in detail the mortars petrography under the light microscope. Using the scanning electron microscope (SEM), usually with attachment for chemical analysis at the crystal scale, in addition to X-ray diffraction technique may help characterization of the cement phases qualitatively and quantitatively.

Potential Use of Crushed Ghanaian Limestone in Paste and Mortar Formulated for Masonry

Crushed Ghanaian limestone （L） powder was analysed for its physical, chemical and microstructural properties for the formulation of mortar for masonry. Ordinary Portland Cement （OPC） was replaced by 10- 40% limestone powder for paste and mortar formulation. Mechanical properties that included compressive strength, water demand and setting times （initial and final） were determined and analysed. The mechanical properties were determined in accordance with ASTM standards. The test results indicated that crushed limestone powder contained about 88.7% CaO in calcite form. A 10-30% and 35-40% limestone content in conjunction with OPC was suitable to produce ASTM type M and S mortars respectively. Formulated OPC - L paste showed a high water demand, a delayed initial setting time and an accelerated final setting time than the plain OPC paste.

Experimental Investigation of Bed Joint Reinforcement Corrosion in Masonry Mortars

The paper investigates the behaviour against corrosion offered by seven masonry mortar compositions to the reinforcement placed in masonry bed joints. Durability protection was evaluated on the basis of four criteria: carbonation area of the specimens, mass loss of steel, electrochemical potential and presence of chloride ions. Tests were performed against two corrosive environments, with and without chloride ions, and were carried out for three periods: three, six and thirty three months. Two types of steel were used, plain steel and galvanized steel. Moreover, the steel protective action of a corrosion inhibitor, sodium nitrite, was examined. A qualitative comparison approach against prototype concrete-like mortars was used. The results showed that the selected masonry mortars did not exhibit similar properties against corrosion to those of concrete and that the addition of sodium nitrite decrease of the corrosion rate only 5% - 20% did not meaningfully improve durability properties. Nevertheless, the addition of lime in small quantities did not have a negative impact on the mortars’ durability characteristics, e.g. the same average corrosion rate.

基于计算机断层扫描的浆砌石真实三维孔隙网络模型及其渗流数值模拟

为研究浆砌石渗流规律,以广东省某已运行30余年的浆砌石拱坝典型芯样为例,基于计算机断层扫描(CT)技术构建了浆砌石真实三维孔隙网络模型,并对不同孔隙结构和水压差下浆砌石的渗流特性进行模拟。结果表明,高流速的渗流路径沿着大孔隙所在位置集中,流线更加顺直平滑,而其周围的小孔隙内渗流路径则较为分散;大孔隙中流速和流量更大,大流速会冲蚀浆砌石结构从而促进联通孔隙向着微裂隙转变,小孔隙向着大孔隙转变;随着水头差增大,浆砌石最大流速和最大流量均逐渐增大,且孔隙结构越发育,增大幅度越大。

基于镁渣-水泥-脱硫石膏复合胶凝材料的砌筑砂浆制备及其性能

镁渣高效利用对于金属镁冶炼行业的可持续发展和环境保护具有重要意义。本文以镁渣、水泥和脱硫石膏为主要原料,设计和配制复合胶凝材料,并以此制备高性能砌筑砂浆。三元体系胶凝材料试验结果表明,以高掺量镁渣制备的胶砂试件28 d抗压强度可达35.6 MPa,脱硫石膏对镁渣-水泥胶凝体系起到了活性激发作用,尤其对28 d强度具有明显的促进作用。以镁渣-水泥-脱硫石膏复合胶凝材料制备的砌筑砂浆28 d抗压强度最高达25.32 MPa,满足JGJ/T 98-2010《砌筑砂浆配合比设计规程》中M25等级的要求。研究成果可为镁渣大规模资源化利用提供参考。

装配式ALC砌块轻质隔墙专用粘结砂浆性能研究与应用

采用碱激发矿渣-粉煤灰胶凝材料替代传统的水泥基粘结砂浆用于工厂快速砌筑装配式ALC砌块轻质隔墙,通过试验研究了胶凝材料中碱含量对粘结砂浆凝结时间、抗压强度、拉伸粘结强度的影响,增粘组分对粘结砂浆拉伸粘结强度的影响,保水组分对粘结砂浆力学性能和工作性能的影响。结果表明,碱含量在5%以上时,6 h、1 d、28 d抗压强度均能满足设定指标要求,增粘组分掺量在1.2%时6 h和14 d拉伸粘结强度达到最大值,分别为0.59、0.62 MPa。考虑到砂浆性能、施工时间及材料成本,胶凝材料中碱含量应控制在5%~6%,增粘组分掺量为0.8%,保水组分掺量为0.3%。

砂浆流失下长期服役砌石渡槽稳定性规律研究

以某砌石渡槽结构为对象,通过开展现场检测分析,揭示结构病害规律,针对砌石结构中的砌石离散的特点,提出以不连续块体理论开展砌石渡槽研究,揭示了砂浆流失对结构安全的影响。结果表明:(1)长期服下砌石渡槽的结构性主控致灾病害为拱圈砂浆流失;(2)砂浆流失位置和程度是关键参数,拱顶处砂浆流失致危程度最高,其次是拱肩和基础,砂浆集中流失比分散性流失更危险;(3)砂浆脱落造成的砌体结构失稳的物理机制,是由于砌石“物理性咬合度下降”影响,而非砂浆参数、砌石断裂或错动;(4)长期服役下砌石渡槽加固延寿措施应以阻断砂浆物理性流失和加强砌石咬合度为原则。研究成果对长期服役砌石渡槽的检测与安全鉴定、带病运行的砌石渡槽除险加固具有重要意义。

考虑砌筑砂浆劣化的老旧砌体结构抗震性能分析

北京地区现存大量建造于1980年前后的在役老旧砌体房屋,因服役时间较长,普遍存在建筑材料劣化的现象。选取砌筑砂浆作为研究对象,通过分析冻融循环劣化过程和现场砌筑砂浆实测结果,建立北京地区实际服役环境下砂浆抗压强度劣化时变模型。通过建立典型老旧砌体结构房屋有限元模型,采用层间位移角作为评价指标,对不同建造年代的砌体房屋抗震性能进行分析研究。结果表明,随着服役时间增加,该六层砌体结构整体位移响应增大,且主要发生在服役20年之后。在7度设防地震作用时,服役超过40年的砌体房屋损伤接近严重破坏状态,难以满足抗震设防要求。在峰值加速度为200gal的地震作用时,未劣化砌体结构没有达到倒塌状态,而服役50年的劣化砌体结构进入倒塌状态指标界限内,抵抗倒塌的能力下降十分显著,显示出对多年服役劣化砌体结构进行鉴定加固的急迫性。

双层玻璃纤维网格增强环氧砂浆单面加固砌体墙抗震性能试验研究

为研究双层玻璃纤维网格增强环氧砂浆单面加固砌体墙的抗震性能,对两个高度为1200 mm、宽度为1600 mm、厚度为240 mm的砌体墙进行低周往复试验。试验结果表明:1)双层玻璃纤维网格增强环氧砂浆抗震加固技术切实可行,加固后的墙体破坏形态由脆性转为延性;2)加固后能够降低裂缝扩展速率,减小裂缝宽度;3)显著提高了墙体承载力与变形能力,峰值荷载约提高了91.5%,开裂荷载约提高了20.4%,墙体开裂位移提升了20.0%;4)加固墙体的滞回曲线更加饱满优良,可恢复性变形增加,残余变形更小。本文成果可为砌体墙的加固工程提供一定的借鉴与参考。

建筑外墙框架体系一体化系统研发与应用

研发了新型建筑外墙框架体系一体化系统,并研究不同砌筑粘结砂浆对系统界面粘结性能的影响,分析了系统功能性、耐久性及应用技术。结果表明,普通、薄层、保温砌筑粘结砂浆在硅墨烯改性聚苯保温板与蒸压加气混凝土砌块同时砌筑时的系统拉伸粘结强度,相比其与硅墨烯改性聚苯保温板的拉伸粘结度分别提高了128.6%、35.3%、100.0%。另一方面,使用薄层、保温砌筑粘结砂浆能够明显改善砌体的通缝抗剪强度和系统拉伸粘结强度等性能,进一步提高墙体系统的稳定性和抗开裂性。

砌体快速施工技术的应用

恰当借用一种木质砂浆铺筑工具,论文研究一种砌体快速施工技术。通过应用表明此种技术砌筑速度较快,操作过程简单易于掌握,砂浆平整度有一定保证,在节约施工成本的同时,亦提高了砌体结构几何线性美观度,具备一定推广与实用价值。

利用低碳胶凝材料制备干混砂浆的试验研究

为助力水泥行业的“双碳”目标实现,试验采用一种新型的多元固废低碳胶凝材料替代传统的M32.5砌筑水泥制备干混砂浆,并研究了低碳胶凝材料的组分掺量对干混砂浆的施工性和硬化性能影响。结果表明,采用低碳胶凝材料制备的干混砂浆施工性较好,制备出的砂浆满足GB/T 25181—2019《预拌砂浆》性能要求,可实现低碳胶凝材料在砂浆中的规模化应用。

粉煤灰和玻化微珠改性保温砌筑砂浆性能研究

为改善目前砌筑砂浆和易性和保温性较差的问题,以粉煤灰与硅酸盐水泥作为胶凝材料,玻化微珠和石英砂作为骨料,以及可再分散性乳胶粉、憎水剂、木质纤维素和纤维素醚复合作为添加剂,开发了一种新型保温砌筑砂浆,从干密度、抗压强度、导热系数和干燥收缩四个主要指标入手,确定了蒸压砂加气混凝土专用砌筑保温砂浆的最优配比,对提高自保温墙体的热工性能具有重要的意义。

既有建筑中分隔墙的现场检测及承载力复核

针对既有建筑内分隔墙,探讨不同检测方法下砂浆强度检测值的选择、上部墙体在不同边界条件下的高厚比差异及条形基础抗倾覆的荷载选择;通过一厂房高大隔墙的安全性检测案例及反算,掌握自承重墙承载力复核中水平力的意义。

贯入法检测特细砂砌筑砂浆抗压强度的测强曲线研究

针对重庆地区特细砂砌筑砂浆的性能差异,设计制作不同强度等级的砂浆试件,对组测定其贯入深度和抗压强度,拟合建立贯入法检测特细砂砌筑砂浆抗压强度的专用测强曲线。试验结果验证了贯入法统一测强曲线应用于重庆地区特细砂砌筑砂浆的检测误差,同时表明所建立的专用测强曲线较统一测强曲线检测精度更高,更接近砌筑砂浆的实际强度。专用测强曲线可作为既有砌体结构房屋砂浆强度检测鉴定的参考,亦可作为贯入法检测砌筑砂浆强度地方标准编制的基础数据。

不同砌筑方式下置换砂浆加固砖墙体的抗震性能研究

在现存的历史风貌建筑中,存在许多砂浆强度降低而砖仍然具有较高强度,造成砌体墙体的承载力不满足要求的现象。基于“最小干预”原则,提出了通过用高性能砂浆置换部分旧砂浆提高结构安全性的砌体结构保护性加固技术。在前期置换砂浆加固砌体性能研究的基础上,选择X形置换砂浆的方式,对一顺一丁、三顺一丁、梅花丁、全丁和全顺等砌筑方式设计了6个墙体进行了拟静力试验。试验结果表明:置换砂浆能有效提高墙体的抗剪承载力,且在不同砌筑方式的砖墙中均能起到加固作用;加固后砖墙的承载力取决于未加固区的交叉裂缝或者底部水平裂缝的抵抗能力;砖墙中顺砖占比率越高,墙体刚度退化越慢,后期延性也越好。