Research Progress of Eco-Friendly Portland Cement Porous Concrete:A Review

With the great impetus of energy conservation and emission reduction policies in various countries,the proposal of concepts such as“Sponge City”and“Eco-City”,and the emphasis on restoration and governance of ecological environment day by day,portland cement porous concrete(PCPC),as a novel building material,has attracted more and more attention from scientific researchers and engineers.PCPC possesses the peculiar pore structure,which owns numerous functions like river embankment protection,vegetation greening as well as air-cleaning,and has been of wide application in different engineering fields.This paper reviews the salient properties of PCPC,detailedly expounds the research progress of domestic and foreign literature about this subject in the past ten years(2010–2020),conducts the statistical analysis of the distribution rule of its major properties around the world,combines with the engineering application to summarize the excellent properties of PCPC,and makes a forecast of future research direction.

Anti-Crack Performance of Low-Heat Portland Cement Concrete

The properties of low-heat Portland cement concrete（LHC） were studied in detail. The experimental results show that the LHC concrete has characteristics of a higher physical mechanical behavior, deformation and durability. Compared with moderate-heat Portland cement（MHC）, the average hydration heat of LHC concrete is reduced by about 17.5%. Under same mixing proportion, the adiabatic temperature rise of LHC concrete was reduced by 2 ℃-3 ℃,and the limits tension of LHC concrete was increased by 10× 10^-6-15×10^-6 than that of MHC. Moreover, it is indicated that LHC concrete has a better anti-crack behavior than MHC concrete.

Experimental Study of Rubberized Asphalt Emulsion Modified Portland cement concrete

The poor fatigue properties and high rigidity of cement asphalt emulsion treated mis(CETM) have for a long time been problems restricting its further development making it impossible for C-ETMto be used as surface layer materials. In this paper, a new kind of cement asphalt emulsion composite-rubberized asphalt emulsion modified Portland cement concrete (RACC) was proposed, which was formed by dispersing rubberized aSPhalt emulsion coated coarse aggregates into cement mortar matrix. In order to evaluate systematically the performance of RACC, laboratory tests with nearly one thousand SPecimen were conducted for resilient modulus, fatigue properties, ultimate ban and length,abrasion, temperature contraction, and dry shrinkage. The experimental results show that the problems existed in C-ETM have to a great extends been solved by RACc. To verify the field performance and inquire into paving technology, teSt road appearsatlsfactory it is concluded that when thed ape surface laycr of semi-rigid base course, RACC is more for surface layer material than both Portland cement concrete(PCC) and asphalt concrete(AC)

Influence of Selected Curing Techniques on Compressive Strength of Concrete From Palm Kernel Shell Ash and Ordinary Portland Cement

This paper discusses the findings of an experimental study on the effect of various curing procedures on the compressive strength of concrete pro­duced by partially substituting portland cement with Palm Kernel Shell Ash(PKSA).Palm kernel shell ash was utilized in a 1:2:4 mix ratio as a partial substitute for ordinary Portland cement(OPC)at percentage levels of 0%,10%,and 15%.River sand with particles passing a 4.75 mm BS sieve was used,as well as crushed aggregate with a maximum size of 20 mm,and palm kernel shell ash with particles passing a 212μm sieve.The compressive strength of the test cubes(150 mm × 150 mm × 150 mm)was determined after 7,28,and 56 days of curing.The results demonstrated that test cubes containing Palm kernel shell ash developed strength over a longer curing period than ordinary Portland cement concrete samples and that the strength changes depending on the amount of PKSA in the cube samples.The findings showed that at 28 days,test cubes with 5%,10%,and 15%PKSA content in all curing procedures utilized obtained a greater compressive strength.Curing by immersion produced the highest compres­sive strength in all replacement level while the concrete cured by sprinkling and spraying gives a lower strength in all replacement level.

Water Stability Improvement of Acid Fine Aggregate-Based Asphalt Concrete

In general,acid aggregates are not used in combination with asphalt concrete because of their poor compatibility with the asphalt binder,which typically results in a scarce water stability of the concrete.In the present study,the feasibility of a new approach based on the combination of acid granite fine aggregate with alkaline limestone coarse aggregate and Portland cement filler has been assessed.The mineral and chemical compositions of these three materials have first been analyzed and compared.Then,the effect of different amounts of Portland cement(0%,25%,50%,75%and 100%of the total filler by weight)on the mechanical performance and water stability of the asphalt concrete has been considered.Asphalt concrete has been designed by using the Marshall method,and the mechanical performance indexes of this material,including the Marshall stability and indirect tensile strength(ITS),have been measured together with the related water stability indexes(namely the Marshall stability(RMS)and tensile strength ratio(TSR)).The results indicate that the alkaline limestone coarse aggregate and Portland cement filler can balance the drawback caused by the acid granite fine aggregate.The asphalt concrete has good mechanical performances and water stability when the amount of common limestone powder filler replaced by cement is not less than 75%.

Study of interfacial transition zones between magnesium phosphate cement and Portland cement concrete pavement

The Portland cement concrete pavement(PCCP)often suffers from different environmental distresses and vehicle load failure,resulting in slab corner fractures,potholes,and other diseases.Rapid repair has become one of the effective ways to open traffic rapidly.In this study,a novel type of rapid repair material,basalt fiber reinforced polymer modified magnesium phosphate cement(BFPMPC),is used to rapidly repair PCCP.Notably,the mechanical properties and characteristics of the repair interfaces which are named interfacial transition zones(ITZs)formed by BFPMPC and cement concrete are focused on as a decisive factor for the performance of the rapid repair.The changing trend of the elastic moduli was studied by nanoindentation experiments in the ITZs with the deconvolution analysis that the elastic moduli of certain kinds of substances can be determined.The experimental results show that the elastic modulus of ITZ-1 with a width of about20μm can be regarded as 0.098 times of the aggregate,and 0.51 times of the ordinary Portland cement(OPC)mortar.The BFPMPC-OPC mortar ITZ has roughly the same mechanical properties as the ITZ between aggregate and BFPMPC.A multi-scale representative two-dimensional model was established by random aggregate and a two-dimensional extended finite element method(XFEM)to study the mechanical properties of the repair interface.The simulation results show that the ITZ formed by the interface of BFPMPC and OPC mortar and basalt aggregate is the most vulnerable to failure,which is consistent with the nano-indentation experimental results.

A Study on Strength Properties of Concrete with Replacement of Low C3A Cement by Fly Ash

The chemical composition of cement has a crucial impact on the performance of concrete.Different brands of Portland cement are used for various construction works without prior knowledge of their performance.For economic and environmental reasons,the valorization of fly ash in concrete production has been increasingly studied.The aim of this study is to determine the mechanical performance of the cement in which hydrated cement has been injected,and to assess the environmental benefit of using the waste as a partial replacement.The experimental study consists of replacing cement,with high tricalcium aluminate(C3A)content,with cement with low C3A content.The obtained result shows that it is very feasible to valorize this material and to manufacture eco-environmental cement which has rheological and mechanical characteristics almost similar to or better than that of ordinary cement,where a resistance of 30 MPa has been obtained,after a substitution rate of 50%.The valorization by using cement with low C3A content makes it possible to strengthen the material at a young age and leads to obtain more economical and less polluting cement.

Influence of Constituent Materials Properties on the Compressive Strength of in Situ Concrete in Kenya

The poor quality of Kenyan in situ concrete has necessitated research to establish the properties of the ingredient materials and their influence on the troubling rate of failure of reinforced concrete structures in the country during construction and usage. The compressive strength of concrete relies on the properties of the constituent materials, proportions of the mixture, workmanship, compaction method and curing conditions. This paper outlines findings of an experimental investigation on the properties of Kenyan concrete ingredient materials and their influence on the compressive strength of concrete in Kenya. Three types of cements (42.5N, 32.5R, 32.5N) from six different cement manufacturers and fine aggregates from three different regions in the country were used during the study. Cements and aggregates chemical analysis was done using the Atomic Absorption Spectrometer machine while the physical and the mechanical properties were checked based on the British Standards. The British DOE concrete mix design method was used to generate the concrete mix proportion and concrete was tested for early and ultimate compressive strengths at 7, 14 and 28 days. It was observed that the different cement brands have varying properties with CEM A having the highest ultimate compressive and flexural strengths. It was further noted that aggregates from the coastal region produced concrete of higher compressive strengths. When the commonly used mix design method was adopted, blended Portland cements produced concrete with ultimate compressive strengths lower than the designed target strengths. The study therefore recommends the development of a concrete mix design procedure for blended cement concrete production in Kenya.

Properties of Sawdust Concrete

This work examined the structural properties of concrete obtained by partially replacing cement with sawdust ash.The sawdust ash which is a pozzolan was obtained by burning sawdust which is a waste product from processing of timber in an open air.The burnt ash was passed through a 150μm metric sieve to obtain the ash used.Physical and chemical analysis were performed on the ash to verify its suitability as a partial substitute for cement in concrete.Chemical analysis was also carried out on the Ordinary Portland Cement(OPC)sample.Concrete mixes were produced by replac­ing OPC with 0%,5%,10%,20%and 30%of Sawdust Ash(SDA).Both fresh and hardened properties of the concrete produced were investigated.The chemical investigation on the ash showed that it contained most of the basic compounds found in OPC making it suitable to serve as a partial substitute for OPC in concrete.Investigation on the concrete showed that both the workability and density of the concrete reduce as the SDA content increases.Analysis on the hardened concrete revealed that the compressive strength of the concrete decreases as the ash content increases for the early ages of curing.However,from 21 days curing age upwards,the compres­sive strength decreases as SDA increases up to 10%of SDA at which the compressive strength rose to a maximum value,and then starts reducing again as the percentage SDA increases.Thus,the SDA concrete gained rap­id strength at later ages indicating its pozzolanic activity.

Use of Plant-Based Accelerator to Enhance Rate of Gain of Strength of Kenyan Blended Cement

Concrete is the most widely used construction material in the world. The situation in the country is not an exception as most of the infrastructures in Kenya such as buildings, bridges, concrete drainage among others, are constructed using concrete. Sadly, the failure of buildings and other concrete structures is very common in Kenya. Blended Portland cement type 32.5 N/mm2 is the most widely used concrete binder material and is found in all parts of the country. Despite blended cement CEM 32.5 being the most commonly used cement type in construction industry in Kenya and most developing countries as a result of its low price and availability locally, its strength gain has been proven to be lower compared to when other types of cement are used due to quantity of pozzolanic material added to the blend. This paper outlines findings of an experimental investigation on the use of cypress tree extract as an accelerator to enhance rate of gain of strength on Kenyan blended cements. Six different blended cement brands locally available were used during the study. Cement chemical analysis was done using X-ray diffraction method while for the cypress extract, Atomic Absorption Spectrometer machine was used. Physical and mechanical properties were checked based on the British standards. The generation of the concrete mix design was done using the British DOE method and concrete was tested for the compressive strength at 7, 14, 21, 28, 56 and 90 days. It was observed that 15% dosage of the extract expressed as a mass percentage of the cement content gives the most improved compressive strength of concrete, 10.4% at 7 days and 9.5% at 28 days hence the optimum. It was further noted that when Cypress tree extract is used as an accelerator in the mix, the blended cement concrete achieves the design strength at 27 days saving 10 days of the project duration compared to when no accelerator is used while the ultimate strength is achieved at 67 days. The study therefore recommends the use of the cypress tree bark extract at a dosage of 15%, by mass, of the cement content as an accelerator when the structure is to be loaded at 28 days and waiting up to 39 days before loading the structure if no accelerator is used for blended cement concrete.

再生微粉-电石渣制备硅酸盐水泥熟料及其水化性能研究

以再生微粉(RCP)和电石渣(CCS)等典型固废作为原材料,开展了固废基低碳水泥熟料制备技术研究。试验分析了煅烧温度(1300℃、1350℃、1400℃和1450℃)以及CCS和RCP含量对熟料煅烧和矿相组成的影响,并研究了1400℃下制备的水泥熟料的水化特性与力学性能。结果表明,RCP的加入可以降低水泥熟料的烧成温度,适量的RCP(60%)作为水泥生料掺入会提高熟料的力学性能,有利于水泥的早期水化。这些工作有助于推进建筑垃圾的资源化利用,为水泥生产中钙硅质原料提供了替代方案。

大体积混凝土工程用高等级抗裂、抗蚀混凝土制备及其性能研究

对比了高铁相硅酸盐水泥与普通硅酸盐水泥制备出的C45和C60混凝土材料抗压强度、水化放热量、化学结合水含量、自收缩变形及抗氯离子渗透性能差异。结果表明:以高铁相硅酸盐水泥为关键材料,辅以高掺量粉煤灰和矿粉复合矿物掺合料等方法,制备出的C45和C60高铁相水泥混凝土抗裂和抗蚀性能优异。C45高铁相水泥混凝土3d绝热温升仅为19.41℃,28d与56d化学结合水含量分别为20.91%、25.66%,较普通硅酸盐水泥混凝土,28d自收缩低17.74%,56d氯离子扩散系数低36.71%,56d电通量低1.99%;C60高铁相水泥混凝土3d绝热温升仅为23.00℃,28d与56d化学结合水含量分别为20.06%29.05%,较普通硅酸盐水泥混凝土,28d自收缩低11.21%,56d氯离子扩散系数低15.60%,56d电通量低3.36%。高铁相水泥混凝土胶凝材料后期水化更加充分,提升了高等级大体积混凝土的抗裂、抗蚀性能。

玄武岩纤维增强地质聚合物混凝土的动态力学性能

对玄武岩纤维增强地质聚合物混凝土(basalt fiber reinforced geopolymer concrete,BFRGC)进行了动态压缩试验,研究了玄武岩纤维掺量(0.1%、0.2%、0.3%)和龄期(3 d、7 d、28 d)对地质聚合物混凝土动态力学性能的影响,分析了玄武岩纤维对地质聚合物混凝土的强韧化效应。此外,对比分析了玄武岩纤维对地质聚合物混凝土和普通硅酸盐水泥混凝土的增强增韧效果。结果表明:BFRGC的动态抗压强度(f_(cd))和比能量吸收(U)随应变率近似线性增加。随着龄期的增大,BFRGC的f_(cd)和U不断增大,且f_(cd)和U的应变率敏感性不断增强。随着玄武岩纤维掺量的增大,BFRGC的f_(cd)和U先增大后减小,且f_(cd)和U的应变率敏感性也先增强后减弱。玄武岩纤维的最佳掺量为0.2%。玄武岩纤维对地质聚合物混凝土和普通硅酸盐水泥混凝土均具有增强增韧作用。玄武岩纤维对地质聚合物混凝土的强韧化效果优于普通硅酸盐水泥混凝土。

低热硅酸盐水泥水工衬砌混凝土抗裂性文献综述

对低热硅酸盐水泥的技术要求进行阐述,综述了前人对低热水泥进行的宏观微观抗裂性试验,对低热水泥抗裂性方面的研究成果文献进行归纳和总结,对国内外低热水泥在水利工程中的应用和研究现状进行回顾,指出低热水泥在水工衬砌混凝土抗裂性上研究不足,展望未来低热水泥在水工衬砌混凝土中的应用研究前景。

矿粉改善OPC基修补材料耐污水腐蚀性能的研究

针对混凝土表面缺陷修补材料存在耐久性不良的问题,研究普通硅酸盐水泥基(OPC)和普通硅酸盐水泥基-矿粉基(OPC-GGBS)修补材料在污水环境下外观形貌、质量、抗压强度及与老混凝土粘结强度的变化。结果表明:25%的矿渣粉取代率可显著减轻OPC修补材料的外观劣化程度,降低了质量、抗压强度及与老混凝土粘结强度的损失率,明显改善了OPC基修补材料的耐污水腐蚀性能。

硅酸盐水泥熟料研磨方式对水泥性能和混凝土抗裂性能的影响

首先介绍了球磨机和冲击粉磨机的工作原理,对两种研磨方式下水泥熟料的粒径和微观形貌进行观测,然后往两种水泥熟料中加入二水石膏制成水泥,测试水泥的标准稠度用水量、抗折强度、抗压强度、折压比和干燥收缩率;最后通过圆环约束收缩试验测试采用两种水泥制备的混凝土抗裂性能。结果表明:与球磨相比,冲击粉磨的水泥熟料粒度分布范围窄,0~10μm细粉含量少,但两种水泥熟料微观形貌差异不大;与采用球磨方式相比,采用冲击粉磨方式制备的水泥虽然早期强度较低,但后期强度较高,标准稠度用水量较少,折压比较高,干燥收缩率较小;与采用球磨方式相比,采用冲击粉磨方式制备水泥时混凝土抗裂性能更好。建议采用冲击粉磨方式生产铁路高抗裂混凝土用硅酸盐水泥。

不同类型持载混凝土碳化性能研究

为探讨外加荷载对不同环境湿度、不同类型混凝土碳化性能的影响,本文提出了自然条件下服役钢筋混凝土构件碳化深度预测模型。基于100 mm混凝土立方体试块和持载钢筋混凝土梁的加速碳化试验结果,分别采用硅酸盐水泥、硅酸水泥掺30%粉煤灰和硅酸水泥掺50%磨细高炉矿渣浇筑混凝土试块和梁试件。结果表明:对不同类型混凝土的服役钢筋混凝土构件,在50 a和100 a的设计使用年限内,其碳化深度预测值随相对湿度的增加先增大后减小,最大碳化深度预测值均在50%~70%的相对湿度范围内。对持载钢筋混凝土构件,仅硅酸盐水泥混凝土和掺50%磨细高炉矿渣的较小水胶比混凝土满足要求。水胶比较大的掺粉煤灰和掺粒状高炉矿渣的持载混凝土,不能满足不同暴露环境在50%~70%相对湿度范围内的耐久性要求。本文对不同类型持载钢筋混凝土构件的抗碳化耐久性设计有一定的参考价值。

负温条件下硅酸盐-铝酸盐-磷酸盐水泥体系水化机理研究

为了研究在-10℃环境下硅酸盐-铝酸盐-磷酸盐水泥体系(SAP体系)的水化反应情况,通过凝结时间、XRD、TG、SEM等测试分析了SAP体系的水化产物和反应机理。结果表明:掺入铝酸盐水泥(CAC)和焦磷酸钠均有利于硅酸盐水泥(OPC)的早期凝结,但不利于其后期强度发展;SAP体系早期的主要水化产物为C-S-H凝胶和NO_(2)-AFm晶体,CAC掺量越多,7 d水化产物生成量越多,试件的抗压强度越高;7~28 d时,CAC掺量为10%的S9A1P体系中Ca(OH)_(2)晶体持续生成,试件28 d抗压强度达到32.4 MPa。

协同利用锯泥、粉煤灰等固体废弃物制备混凝土

以花岗岩锯泥、粉煤灰、脱硫石膏为基础原料,以普通硅酸盐水泥为主要胶凝材料,通过正交实验进行配比设计,采用静压成型、压制成型两种方法制备了组分不同的混凝土砌块。重点研究混凝土力学性能受各种固体废弃物掺入量的影响及制备过程。研究表明,所设计的混凝土力学性能符合《混凝土路缘石》C30等级要求,耐腐蚀性能符合《混凝土结构耐久性设计标准》要求。

低热硅酸盐水泥对大坝混凝土性能的影响研究

研究不同高镁低热硅酸盐水泥对大坝混凝土的力学性能、变形性能、热学性能、耐久性能等性能的影响。结果表明:优化配合比中水泥、粉煤灰及外加剂掺量后,减水剂掺量可降低至0.4%~0.6%,引气剂掺量降低至0.012%~0.016%,C_(180)40混凝土的单方用水量可降低至82 kg/m^(3)~83 kg/m^(3),65d龄期的自变值在-83.3×10^(-6)~-109.5×10^(-6)之间,绝热温升在27.5℃~28.7℃之间,各配比混凝土的抗压强度和极限拉伸值均能满足设计要求,且有较大富裕;合理提高水泥中Mgo含量,具有较明显的补偿混凝土自生体积变形的收缩效果。