芯样试件抗压强度检测结果的不确定度评定

对芯样抗压强度试验进行不确定度评定,分析其面积、数值修约、压力机三者的不确定度分量,完整的表示其抗压强度的不确定度。

混凝土立方体试件强度检测的影响因素及分析

本文主要对混凝土试件强度检测的影响因素进行探讨,通过在原材料、配合比、试件制作及运输等方面进行分析,为建设工程结构混凝土强度验收提供了一定的指导作用。

回弹法是检测混凝土强度的实用技术

1 前言 随着生产技术、工程结构的发展与住房制度的改革,越来越多的人们提出了这样一个问题,即采用混凝土试块试压的方法所得出的强度,是否能反映构件的实际强度?因为同条件的试块,即使其质量合乎要求,但它在混凝土取样、成型、养护及受力状态等方面,都是与构件有很大的差异.按照现行规范的要求,每100m3可取一组试件,也就是说少量几组试块的试压结果,能在多大程度上代表构件各部位的强度是值得研究的.而在具体的质量事故中,又往往对某一构件需要确定出强度不合格的区域,藉以据此采用相应的加固补强措施,这也不是能通过试块的试压结果能解决的.因此,回弹法不论在理论上还是实用上,都是具有较大的说服力,得到了广泛应用.

水泥砼试件的制、作养护

砼试件的制作和养护的好与坏会直接影响砼强度的准确性,同时也会给工程进度和费用造成不必要的影响,为了更好的控制砼成品的质量,无论在砼配合比或者砼浇筑过程中都要求实验人员现场制作水泥砼试块,测定其7天28天的强度。砼试件作为标准评定其强度是否满足设计强度等级的要求,另外砼试件强度还能指导施工,例;砼拆模有强度要求,梁板吊装时对梁板强度和梁身盖板梁有强度规定等。掌握水泥砼试件的制作、养护的方法是很有必要的.要注意每个细节问题,在少洛高速某标于试验人员经验不足,在制作砼试块过程中,不规范、不明白、无责任心,在制作过程中为了省事,把砼拌和物直接装入试模内,用50㎜震动棒直接一振,大多骨料被振出,结果制出的试件除尺寸形状不符合要求,而且强度不够,结果造成一大桥桩基十几根需要进行取心验证实验。除浪费大量人力物力外,还导致因进度滞后被业主罚款标段分割的后果。

超长大直径钻孔灌注桩自平衡法试验研究——以海峡西岸某标志性建筑为案例

海峡西岸某标志性超高层建筑桩基础采用超长大直径钻孔灌注桩,试验桩桩长达90m^103m,桩径1300mm,设计砼强度水下C50,采用了自平衡试桩法静载试验,设计要求的最大加载值高达55 000kN。通过自平衡法试验、桩身内力测试、钻芯法等检测方法,测到单桩竖向抗压极限承载力、各土层桩身侧阻力和混凝土试件抗压强度检测值等参数,并基此深入分析了桩基破坏模式、桩身侧摩阻力的发挥、桩端承载性状、桩身混凝土抗压强度等。研究结果认为,自平衡法静载试验相较于传统的静载试验具有不受场地条件影响等诸多明显优势,为超长大直径灌注桩的承载力试验提供了一种相对可靠的直接试验方法。同时,建议福建省尽快出台有地区代表性的芯样强度折算系数。

混凝土生产质量管理水平评定问题探讨

【正】一般来讲,要了解某材料的质量情况,首先可从它的平均值来衡量.它是表示数据集中的一个特征数,实质上表示了数据分布的中心位置.例如混凝土立方体试件抗压强度是取三个试件实测值的算术平均值x作为该组试件的抗压强度值.但是有时尽管平均值符合要求,但数据波动太大,它们平均值就不能反映材料的真正质量情况.因此还要弄清被考察材料性能数据的波动情况.我们可以利用衡量波动性大小的指标——标准离差来达到这一目的:

Experimental investigation on strength and deformation of plain high-strength concrete under multiaxial stress state

To investigate the strength and deformation behavior of plain high-strength concrete （HSC） under muhiaxial stress states, a large static-dynamic true triaxial machine was employed, and muhiaxial tests were performed on 100 mm × 100 mm × 100 mm cubes concrete specimens. Friction-reducing pads were three-layer plastic membranes with glycerine in-between for the compressive loading plane. The tensile loading plane of concrete samples was processed by attrition machine, and then the samples were glued up with the loading plate with structural glue. Failure modes of specimens were described. The principal static compressive strengths, strains at the peak stress and stress-strain curves were measured, and the influence of stress ratios on them was analyzed as well. Experimental results show that the ratio of the compressive strength σ3f over the uniaxial compressive strengthfo depends on brittleness-stiffness of concrete besides stress state and stress ratios. The formula of Kupfer-Gerstle＇ s and Ottosen＇ s failure criterion for plain HSC under biaxial compression and muhiaxial stress state is proposed respectively.

Compressive strength and abrasion resistance of concrete containing SiO_2 and CuO nanoparticles in different curing media

In the present study,abrasion resistance and compressive strength of concrete specimens containing SiO2 and CuO nanoparticles in different curing media have been investigated.Portland cement was partially replaced by up to 2.0 wt%of SiO2 and CuO nanoparticles and the mechanical properties of the produced specimens were measured.Increasing the nanoparticles content was found to increase the abrasion resistance of the specimens cured in water and saturated limewater,while this condition was not observed for compressive strength in the both curing media.The enhancement of abrasion resistance was higher for the specimens containing SiO2 nanoparticles in both curing media.Since abrasion resistance and compressive strength of the specimens followed a similar regime as the nanoparticles increased for the specimens cured in saturated limewater,some experimental relationships has been presented to correlate these two properties of concrete for this curing medium.On the whole,it has been concluded that the abrasion resistance of concrete does not only depend on the corresponding compressive strength.