Test and analysis of influencing factors on the permeability coefficient of steel slag permeable concrete

The steel slag （SS） permeable concrete was prepared by SS. The influences of the aggregate-cement rate, the aggregate particle size, the water-cement rate, the admixture dosage and other factors on the permeability coefficient of SS permeable concrete were analyzed. The law of influence was also investigated. The study serves as a technological reference for the construction and design of SS permeable concrete.

Investigating the Relationship between Porosity and Permeability Coefficient for Pervious Concrete Pavement by Statistical Modelling

A study evaluating the relationship between porosity and permeability coefficient for pervious concrete (PC) is presented. In addition, the effect of mixture design parameters particularly, water-to-cement ratio (W/C) and size of aggregate on the permeability coefficient of PC was investigated. The PC mixtures were made with 4 range of W/C and 2 range size of aggregate. PC mixes were made from each aggregate and were tested. The results showed that the W/C and aggregate size are key parameters which significantly affect the characteristic performance of PC. Permeability coefficient of coarse pervious concrete (CPC) is bigger than fine pervious concrete (FPC) and the porosity of CPC are bigger than porosity of FPC. A regression model (RM) along with analysis of variance (ANOVA) was conducted to study the significance of porosity distribution on permeability coefficient of PC. The statistical model developed in this study can facilitate prediction permeability coefficient of CPC and FPC as the sustainable pavements.

Pore Characteristic Design Method of High-strength Pervious Concrete Based on the Mechanical Properties and Rainstorm Waterlogging Resistance

High-strength pervious concrete(HSPC) with porosity ranging from 0.08% to 2.011% was prepared. The mechanical properties and rainstorm waterlogging resistance of HSPC were evaluated,and a design method of HSPC pore characteristics(porosity and pore diameter) based on the mechanical properties and rainstorm waterlogging resistance was proposed. The results showed that the reduction of effective cross-sectional area caused by artificial channels was the main factor affecting flexural strength but had limited influence on compressive strength. Compared with the concrete matrix without artificial channels,the compressive strength of HSPC with porosity of 2.011% decreased by 7.4%, while the flexural strength decreased by 48.3%. The permeability coefficient of HSPC can reach 16.35 mm/s even at low porosity(2.011%).HSPC can meet the requirements of no rainstorm waterlogging, even if exposed to 100-year rainstorms. When the mechanical properties and rainstorm waterlogging resistance are compromised, the recommended porosity ranges from 1.1% to 3.5%, and the recommended pore diameter ranges from 0.8 to 2.7 mm.

Research and Prediction on the Properties of Concrete at Cryogenic Temperature Based on Gray Theory

To solve the cryogenic temperature problems faced by all-concrete liquefied natural gas(ACLNG)storage tanks during servicing,a low temperature resistant and high strength concrete(LHC)was designed from the perspectives of reducing water-binder ratio,removing coarse aggregates,optimizing composite mineral admixture and utilizing steel fibers.The variation laws of compressive and tensile strength,elastic modulus and Poisson’s ratio for C60 concrete and LHC were compared and analyzed under the temperatures from 10 to-165℃through uniaxial compression and tensile tests.The rapid freezing method was adopted to analyze the evolution process of mass and relative dynamic elastic modulus loss rates for C60 and LHC in 0-300 freeze-thaw cycles.The gas permeability test was carried out,and the laws of gas permeability coefficient varied with temperature and cryogenic freeze-thaw cycles were obtained.Then,the grey dynamic model GM(1,1)was used to predict the variation laws of physical and mechanical parameters on the basis of the test data.The test results demonstrate that the compressive strength,elastic modulus and Poisson’s ratio for both C60 and LHC increase significantly from 10 to-165℃,but the specific variation laws are difierent,and there is a phenomenon that some parameters decrease after reaching a critical temperature range for C60.The uniaxial tensile strength increases first and then decreases as temperature decreases,and finally increases slightly at-165℃for both C60 and LHC.The mass and relative dynamic elastic modulus loss rates of LHC are much lower than that of C60 under different freeze-thaw cycles.The gas permeability coefficient of C60 declines gradually with the drop of temperature,and increases gradually with the number of freeze-thaw cycles while the gas permeability coefficient of LHC basically remains stable and is much lower than that of C60.Therefore,such a conclusion can be drawn that LHC has better properties at cryogenic temperature.On the premise of providing consistent functional mode,GM(1,1)can predict the test data with high accuracy,which well reflects the variation laws of relevant parameters.

Rational permeability coefficient of a permeable lining for composite tunnel lining structures

Various factors influence the tunneling are simplified considering the axial symmetry of the composite lining structure.The analytical expressions for the seepage field,stress,and displacement in the surrounding rock and those for the grouting circle,permeable lining,and ordinary lining are obtained according to the principle of effective stress.The seepage discharge,plastic zone,stress,and displacement around a tunnel affected by the different permeability coefficient ratios between the permeable lining and surrounding rock are studied.The reasonable value of permeability coefficient for the permeable lining are discussed.The results show that the grouting circle controls the tunnel seepage discharge well and has a reasonable permeability coefficient and an optimal radius.The grouting circle controls the plastic zone development in the surrounding rock,i.e.,the thicker the grouting circle,the smaller the plastic zone in the surrounding rock.The tunnel seepage discharge and the effective stress in the grouting circle and lining increase gradually with the increasing of permeability coefficient ratio and tend to be stable after the ratio reaches 0.1.Comprehensive analysis on the factors such as the stability of tunnel seepage discharge,the plastic zone of the surrounding rock and the stress around the tunnel indicates that it is relatively reasonable for the permeability coefficient ratio to be greater than or equal to 0.1.

低弹模混凝土防渗墙材料参数统计特性及相关分布模型

为获取低弹模混凝土防渗墙渗透系数、弹模和抗压强度3个材料参数的统计特性及相关分布模型,基于2座土石坝的检测数据,根据赤池信息准则(AIC)识别材料参数的最优分布类型及相关分布模型的最优Copula函数、Bootstrap方法模拟识别结果的统计不确定性。结果表明,抗压强度、渗透系数和弹模分别服从极值Ⅰ型、对数正态、威布尔或极值Ⅰ型分布,变异系数均值分别为0.17、0.40、0.11;抗压强度与渗透系数、弹模与抗压强度、弹模与渗透系数之间的Pearson相关系数均值分别为-0.79、0.67、-0.55,最优Copula函数分别为Plackett Copula、Gaussian Copula、Gaussian Copula。研究结果可为低弹模混凝土防渗墙的渗流和强度可靠度计算提供参考。

PET回收料改性再生透水混凝土性能的研究

利用聚对苯二甲酸乙二醇酯(PET)回收料制备再生透水路面材料。通过在透水混凝土中添加不同掺量PET回收料制备了再生透水混凝土并研究其性能。结果表明:掺入不同掺量PET再生骨料的再生透水混凝土表现出了较高的孔隙率与较低的密度;掺入不同掺量PET再生骨料的再生透水混凝土满足力学性能标准值,并且在PET(G)-10达到最高,抗折强度和抗压强度分别为4.03MPa和25.1MPa;掺入不同掺量PET再生骨料的再生透水混凝土的透水性能均高于标准值,拥有良好的透水性能,在保证力学性能满足标准的同时,PET(S)-30和PET(G)-50的透水系数分别为8.5mm/s和8.4mm/s。因此,掺入不同掺量PET再生骨料的再生透水混凝土具有较好的综合性能,可以满足建筑行业的使用要求。

透水混凝土的配合比设计及性能研究

通过L9(34)正交试验研究了骨料级配(_(m4.75~9.50 mm∶m9.50~16.00 mm)=7∶3、6∶4、5∶5)、骨胶比(3.0、3.1、3.2)、粉煤灰掺量(10%、15%、20%)、增强剂掺量(4%、5%、6%)对透水混凝土抗压强度、劈裂抗拉强度、有效孔隙率和透水系数的影响。结果表明:对于抗压强度和劈裂抗拉强度,最佳的_(m4.75~9.50 mm∶m9.50~16.00 mm)为6∶4、骨胶比为3.1、粉煤灰掺量为20%、增强剂掺量为4%;对于有效孔隙率和透水系数,最佳的_(m4.75~9.50 mm∶m9.50~16.00 mm)为6∶4、骨胶比为3.2、粉煤灰掺量为15%、增强剂掺量为6%。

基于正交试验的矿物掺合料透水混凝土性能研究

在透水混凝土中掺入硅灰和矿粉,设计了四因素四水平正交试验,采用极差法分析了目标孔隙率、水胶比、硅灰掺量、矿粉掺量对透水混凝土抗压强度和透水性能的影响,并对其微观形貌进行了分析。结果表明:各因素对透水混凝土抗压强度和透水性能影响的大小顺序为目标孔隙率>水胶比>硅灰掺量>矿粉掺量;透水混凝土的抗压强度和透水系数之间呈负相关关系;微观分析发现,未掺硅灰、矿粉的透水混凝土微观结构存在明显孔洞,硅灰或矿粉的掺入可以对孔洞进行有效填充,在一定程度上减少了孔隙数量,可改善透水混凝土的综合性能。

气压差变化及环氧树脂层对混凝土气体渗透性的影响

基于Cembureau法测量不同气压差下混凝土气体渗透系数,研究气压差变化及环氧树脂层对混凝土气体渗透性的影响。研究结果表明,在一定范围内,混凝土气体渗透系数随气压差的增大呈减小趋势;环氧树脂层可有效减小混凝土气体渗透系数。

面板堆石坝主要分区渗透系数反演及敏感性分析

参数反演是工程渗流分析中确定材料合理的渗透系数的常用手段,但对材料分区较多的面板堆石坝等工程,若对所有分区渗透系数进行反演,将会降低反演效率和精度。对此,以某面板堆石坝工程为例,建立其三维有限元稳定渗流分析模型。通过设计5因子3水平正交试验,并采用测点水头值为分析指标,开展了各分区材料渗透系数对渗流场的敏感性分析,最终确定对渗流场影响较大的材料分区。利用ELM-GA算法对其渗透系数进行反演,结果表明测点水头计算值与实测值最大相对误差仅为2.2%,得到的渗透系数可用于坝址区的渗流计算分析。研究结果可为类似工程提供借鉴。

C25透水混凝土性能影响因素及应用分析

从孔隙率、骨料粒径、水胶比、增强材料等方面出发,系统分析了不同设计参数对透水混凝土性能的影响,并在此基础上,以C25透水混凝土为例进行配合比设计,研究了骨料粒径、不同增强料对透水混凝土抗压强度、孔隙率和透水系数的影响,同时结合实际工程开展透水混凝土的工程应用研究,为类似工程提供一定参考。

透水混凝土性能研究现状简述

随着城市化的推进,混凝土、沥青等非渗透性物质已经完全覆盖了城市的表面,造成了城市热岛效应、地下水补充不足、车辆噪声污染等现象。透水混凝土是一种环保型的、可持续的路面材料,由于其特殊的内部结构,具有控制雨水径流、改善水质、补给地下水、降低路面轮胎噪声、调节路面温湿度、缓解城市热岛效应等环境优势。但是由于透水混凝土的力学性能普遍低于一般的混凝土,从而制约了其在实际工程中的应用。本文对近年来对透水混凝土抗压性能和透水性能相关研究进行了简述,分别从水灰比、多种矿物掺合料和纤维等因素对透水混凝土性能的影响进行分析,对透水混凝土进一步研究和应用具有重要意义。

碳纤维改性透水混凝土的制备及力学性能研究

为探究碳纤维对透水混凝土的改性方法,明确相关参数对其物理力学性能的影响规律,文章开展了一系列室内试验研究。考虑碳纤维几何特征、掺量等核心参数,在室内制备标准试件,研究了碳纤维长度、掺量等对透水混凝土物理、力学性能的影响机制,以及对其透水性能的影响。研究结果表明,碳纤维长度、体积掺量对透水混凝土的力学性能有较大影响,纤维长度越长、掺量越大,透水混凝土的力学性能提升效果越显著,其中,抗折性能最高可提升70%。但是,碳纤维同时也会降低改性混凝土的透水性能,因此,在制备碳纤维改性混凝土时,应兼顾力学性能与透水性,合理设计。

建筑垃圾再生砖混透水混凝土性能研究

建筑砖混垃圾的再利用有利于节约资源和保护环境,促进中国更快实现“双碳”目标。为研究水灰比和骨料粒径对再生砖混透水混凝土抗压强度和透水系数的影响,文章以水灰比(0.28~0.32)和骨料粒径(4.75~19 mm)作为变量,探究2个变量对抗压强度和透水系数的规律。研究结果表明:一方面,再生砖混透水混凝土的抗压强度在水灰比变化时,起初会有所增强,但之后会呈现下降趋势;而随着骨料粒径的增加,其抗压强度则逐渐减弱。另一方面,该混凝土的透水系数会随着骨料粒径的增大而增加。值得注意的是,不同骨料粒径下的水灰比对透水系数的影响并非一致,存在一定的差异,骨料粒径4.75~9.5 mm和9.5~16 mm下的透水系数随水灰比增大而呈先增大后减小的趋势,而骨料粒径16~19 mm下透水系数随水灰比的增大而减小。文章研究结果可为实际工程提供参考和借鉴。

透水混凝土的组成设计及其性能研究

参考ATPB开级配沥青稳定碎石排水基层的级配设计要求,首先采用计算和试验相结合的方法确定透水混凝土的配合比,然后对不同孔隙率透水混凝土的性能进行探究。结果表明:透水混凝土力学性能随孔隙率增大而降低;透水系数随孔隙率的增大而增大;当透水混凝土设计孔隙率为18%时,其抗压与抗折强度分别为22.3 MPa和3.6 MPa,透水系数为1.63 mm/s,满足透水混凝土强度≮20 MPa、孔隙率≮15%的要求。

透水混凝土配合比优化研究

为改善目前透水混凝土应用中透水性能不足的问题,采用正交试验方法研究了水灰比、目标孔隙率、骨料级配、玄武岩纤维长度和掺量对其性能的影响。结果表明:水灰比和目标孔隙率对力学性能和透水性能具有显著影响;骨料级配为1∶6时其力学性能达到最佳,骨料级配为1∶7时其透水性能达到最佳;掺入适量的玄武岩纤维可以提高透水混凝土的力学性能,但对其透水性能具有不利影响。

玄武岩纤维及矿物掺合料对再生骨料透水混凝土性能的影响研究

再生混凝土由于采用了再生混凝土骨料及孔隙率较大,存在强度较低的问题,通过掺加纤维和矿物掺合料的方式可以有效提高多孔混凝土的力学性能。试验表明再生骨料透水混凝土抗压强度随孔隙率增大而减小,渗透系数随孔隙率增大而增大;再生骨料透水混凝土抗压强度随水灰比先增大后减小,渗透系数随水灰比增大而减小。当孔隙率18%,单掺玄武岩纤维时,再生骨料透水混凝土水的最佳水灰比为0.27,纤维掺量为0.1%;双掺硅灰和玄武岩纤维,玄武纤维掺量0.1%时,最佳水灰比为0.27,硅灰掺量6%~9%,透水混凝土28 d抗压强度为15.9~16.6 MPa,渗透系数为65.0~70.7 mm/s;双掺粉煤灰和玄武岩纤维,粉煤灰掺量10%时,最佳水灰比为0.30,玄武岩纤维掺量0.1%,透水混凝土28 d抗压强度为17.1 MPa,渗透系数为58.3 mm/s。

暴雨作用下新型再生透水混凝土的抗堵塞性能

通过暴雨堵塞试验,研究了新型再生透水混凝土(NRPC)的抗堵塞性能,分析了NRPC孔径(d)和堵塞物粒径(r)对NRPC堵塞结构、透水系数、堵塞深度和堵塞物通过率的影响.结果表明:NRPC形成的堵塞结构由孔径和堵塞物粒径的比值(d/r)共同决定,暴雨作用后的堵塞结构分为单颗粒表面堵塞、单颗粒孔道堵塞和多颗粒孔道堵塞;透水系数的降低主要发生在第1次暴雨堵塞循环中,小粒径堵塞物(r <1.18 mm)形成的多颗粒堵塞是造成NRPC透水系数降低的主要原因;随着d/r的增加,多颗粒孔道堵塞结构的稳定性不断降低,当d>r时,d/r越小,NRPC孔道堵塞的深度越大;随着d/r的增加,堵塞物的通过率不断增加,孔道的筛选作用降低.

矿物掺合料透水混凝土微观结构及性能分析

透水混凝土具有显著的孔隙特征,可有效缓解城市内涝,涵养地下水系。针对透水混凝土由孔隙大导致的抗压强度低等问题,采用矿物掺合料替代部分水泥作胶凝材料,能够实现降低生产成本并提高抗压强度的目的。本文以粉煤灰、矿渣、偏高岭土等固体废弃物为掺合料,通过抗压强度、透水性能测试分析矿物掺合料单掺、复掺、三掺对透水混凝土性能的影响,并探究其水化机理。结果表明:复掺以及三掺体系的透水混凝土力学性能明显优于单掺体系;当三掺体系粉煤灰、矿渣、偏高岭土掺量分别为15%(质量分数,下同)、15%、10%时,透水混凝土性能最佳,抗压强度达22.1 MPa,孔隙率和透水系数分别为14.3%、3.27 mm/s,满足行业标准。