混凝土抗压强度和弹性模量与其超声声速之间关系的试验研究

在混凝土超声无损检测法的基础上，本文对三种强度等级，各龄期的混凝土试块进行超声波测试，并同时进行抗压强度和弹性模量试验，由试验数据经回归分析得到了抗压强度、弹性模量和超声声速之间的函数关系，为用超声法测试混凝土抗压强度和弹性模量提供了一定的试验数据和参考依据。     

橡胶混凝土超声声速与抗压强度关系的试验研究

利用超声检测方法对掺60目、1~3 mm、3~6 mm橡胶颗粒(粉)的橡胶混凝土进行超声声速及抗压强度测试。试验结果发现:橡胶混凝土超声声速与抗压强度之间存在幂函数关系,超声声速随抗压强度的提高而增大,超声声速与抗压强度随橡胶掺量的增大而减小,随粒径的增大而增大。     

高强混凝土弹性模量与抗压强度的相关性试验研究

结合某水库工程工程高强混凝土试验研究,建立了高强混凝土弹性模量与抗压强度的相关关系式,讨论了硅灰掺量,水胶比及骨料量对弹性模量的影响。     

再生混凝土的抗压强度与弹性模量研究

研究了再生骨料的掺量以及掺加方式对再生混凝土轴心抗压强度与弹性模量的影响,结果表明:再生骨料对再生混凝土弹性模量与抗压强度的影响并不一致,再生混凝土的弹性模量随着再生骨料掺量的增加而逐渐降低,但强度则并非如此,而是当再生骨料掺量为50%时强度最高,再生混凝土具有高强度低弹模的特性。     

再生混凝土的早期抗压强度与弹性模量研究

再生混凝土的早期抗压强度和弹性模量对于该类结构施工期的安全性具有重要影响.选取试验龄期分别为1、3、7、14、21、28d,考察不同强度等级和不同再生骨料取代率再生混凝土早期抗压强度和弹性模量的发展规律.试验结果表明,再生混凝土的早期抗压强度和弹性模量较普通混凝土偏低,需要在施工期间采取相应措施,以保证再生混凝土结构施工的安全性.基于试验结果,建议了再生混凝土早期抗压强度和弹性模量的计算公式.在此基础上,进一步将研究成果应用于某再生混凝土刚性路面施工中,取得了良好的效果.     

混凝土动弹性模量的试验测定

1 概述 目前,建筑结构抗震设计中,通常先求出结构的自振周期,然后采用振型分解频谱法计算地震作用。计算自振周期时混凝土的弹性模量取《混凝土结构设计规范(CBJ10-89)》采用的弹性模量E_h。事实上,在动力荷载作用下,特别是在应变速率很高的情况下,混凝土内部的微裂缝来不及发展,使混凝土的弹     

基于超声弹性模量测量的混凝土健康状况监测

研究了超声法弹性模量测量的原理,通过采用超声波法测量混凝土结构的弹性模量,来评价混凝土的健康状况及老化程度,并给出了实验结果,为解决工程实际中的在役混凝土结构的健康监测问题提供了可行性依据。     

自保温混凝土小型空心砌块砌体抗压强度及弹性模量的试验研究

对三组27个自保温混凝土砌块试件进行了抗压强度和弹性模量的试验研究,试验结果表明,自保温混凝土砌块砌体的受压破坏过程分为三个阶段,与普通混凝土砌块砌体的受压破坏过程类似;自保温混凝土砌块砌体的初裂荷载约为破坏荷载的70%,表现出了明显的脆性特征。     

纤维复合胶粉改性混凝土的弹性模量与强度的相关性

通过正交试验研究分析了纤维、胶粉以及硅粉复合改性混凝土的抗压强度和弹性模量,分析了纤维复合胶粉改性混凝土抗压强度与弹性模量的关系。研究表明:聚丙烯纤维复合胶粉改性混凝土的抗压强度与弹性模量符合Ec=0.278fc+19.209线性关系,相关性十分显著;正交试验四个参数对混凝土的抗压强度和弹性模量的影响主次顺依次为胶粉掺量、硅粉掺量、纤维掺量、纤维长度,且胶粉能明显减小抗压强度和弹性模量;硅粉对混凝土抗压强度的增强效应在其掺量为2.5%时最佳。     

Evaluating residual compressive strength of concrete at elevated temperatures using ultrasonic pulse velocity

In this paper, the ultrasonic pulse velocity (UPV) is used to quantitatively evaluate the residual compressive strength of concrete subjected to elevated temperatures. A series of tests were performed to examine the relationship between the residual UPV and strength of concrete with different mixture proportions at elevated temperatures. Cylindrical specimens were made of concrete with water–cement ratios of 0.58 and 0.68, and heated in an electric furnace at temperatures ranging from 400 to 600 °C. After exposing to the elevated temperature, the concrete specimens were cooled down in the ambient air and tested on different days. For each test, the pulse velocity and compressive strength were measured. Experimental results show that change in mixture proportion of concrete does not have a significant effect on the residual strength and UPV ratios of concrete subjected to elevated temperatures. This important finding considerably enhances the feasibility of using UPV for quantitative evaluation of the residual strength of fire-damaged concrete structures. The relationship between the residual strength ratio and the residual UPV ratio was developed and a general equation was proposed for residual strength prediction. Finally, this paper verifies the suitability of the proposed equation for predicting the residual strength ratios of different concrete specimens with the measured residual UPV ratios.     

橡胶混凝土抗压强度与超声波波速关系的试验研究

利用超声波混凝土无损检测技术,对3种不同粒径、不同掺量的橡胶粉改性高强混凝土试件进行了超声波检测,并同时进行了抗压强度试验,由试验数据回归出了抗压强度和超声波波速之间的关系,可为橡胶改性高强混凝土的强度测试提供一定的技术参考.     

Splitting tensile strength and modulus of elasticity of self-compacting concrete

In this experimental work, the splitting tensile strength and the modulus of elasticity are studied for self-compacting concretes of different ages. At the same time, its porous structure is analysed, since this aspect is directly related with mechanical properties of the material. Eight different concretes were used, four self-compacting and four normally-vibrated, with different water/cement ratios and different types of cement. The results obtained show that in self-compacting concretes made with limestone filler the splitting tensile strength is on average 15% less than that of normally-vibrated concretes. It is therefore suggested that the standard expressions that are normally used for normally-vibrated concretes should be modified for these concretes. In addition, it is seen that the cementitious paste’s modulus of elasticity is greater in the self-compacting concretes because the addition of limestone fines creates lower porosity and a finer microstructure. Despite this, the concrete’s modulus of elasticity tends to be around 2% less in the self-compacting concretes as a result of the greater amount of cement paste in the self-compacting concretes.     

Models to predict the uniaxial compressive strength and the modulus of elasticity for Ankara Agglomerate

Determination of the uniaxial compressive strength (UCS) and modulus of elasticity of block-in-matrix rocks (bimrocks) is often impossible in the laboratory since the preparation of the standard core samples from bimrocks is extraordinarily difficult. For this reason, some predictive models were developed to estimate the UCS and modulus of elasticity based on the volumetric portion of blocks in Ankara Agglomerate, which is composed of black and pink andesite blocks in a tuff matrix. The ratio of E_imin of blocks (5.99 GPa) to E_imax of the tuff matrix (2.83 GPa) is 2.2 for Ankara Agglomerate. In addition to this contrast, the minimum ratio of UCS values of andesite blocks (34.99 MPa) to matrix tuff (14.4 MPa) is 2.4. In the first stage of the study, fuzzy logic was used as a tool for the prediction of the UCS of Ankara Agglomerate based on its block and matrix constituents. UCS values for 164 agglomerate cores were evaluated in the prediction model based on fuzzy logic. A triangular chart expressed by “if-then” rules considers different constituent composition of the agglomerate. Considering the membership functions depending on the portion of constituents, a Mamdani fuzzy algorithm was constructed and a fuzzy triangular chart was obtained for the estimation of the UCS of the agglomerate. The ‘variance accounts for’ (VAF) and the root mean square error (RMSE) indices were calculated as 56.9% and 7.3, respectively, to characterize the prediction performance of the triangular chart. In the second stage of the study, the goal was to construct a prediction model for the estimation of the modulus of the elasticity. Regression analyses were performed using 103 UCSs and the unit weight data obtained from core samples prepared from tuff matrix, black and pink andesite blocks and agglomerate. An equation having a correlation coefficient of 0.951 was obtained from the regression analyses. The VAF and RMSE indices for the multiple regression equation were obtained as 88.8% and 0.84, respectively. Both correlation coefficient and the performance indices indicated that the prediction capacity of the equation is high.     

回弹超声角测综合法检测混凝土抗压强度研究

为提高回弹超声角测综合法对结构混凝土抗压强度的检测精度,在足尺结构模型混凝土柱两相邻侧面测试超声角测法测区声速、相应单面测区回弹值与相应测区直径100mm标准芯样抗压强度.利用所测得的数据回归拟合得到标称能量2.207J中型回弹仪回弹超声角测综合法专用测强曲线,并与以超声对测法测区声速参数回归建立的超声回弹综合法测强曲线进行比较.结果表明,采用超声对测法测区声速参数回归建立的超声回弹综合法测强曲线计算超声角测法测区混凝土抗压强度存在较大误差;建立的标称能量2.207J中型回弹仪回弹超声角测综合法专用测强曲线具有足够检测精度,可用于强度等级C20～C70预拌泵送混凝土抗压强度检测;采用自制的角距仪装置可准确测量超声角测法测点所处位置及二面角角度,然后根据余弦定理精准计算超声角测法测点间距.     

混凝土剪拉综合强度与立方体抗压强度关系的研究

通过分析混凝土立方体试块破坏的机理,以及混凝土剪切强度、拉脱强度与立方体抗压强度之间的数值关系,提出剪拉综合法的测试方法及其强度换算模型.大量相关试验数据的对比验证表明,剪拉综合法不是对剪切法与拉脱法的简单平均与组合,由于计算模型更加科学地反映了混凝土立方体试块的破坏机理,其计算结果的相对偏差和离散性明显优于单纯的剪切...     

混凝土芯样抗压强度尺寸效应研究

鉴于桥梁垮塌事故现场混凝土材料破碎的特点,混凝土取芯鉴别面临着尺寸效应的问题,通过对混凝土芯样尺寸效应的研究,总结分析了国内外针对非标准芯样抗压强度的换算系数,并根据破碎特点设计了针对性试验,混凝土非标准芯样抗压强度试验主要考虑准100、准67、准49、准32等4种直径范围和1.5、1.2、1.0、0.8、0.5等5种高径比范围,数据回归分析得到尺寸效应统计公式,并与相关规范做了比较,试验结果对事故鉴别和工程实践具有借鉴意义。