Wear resistance of polymer-impregnated mortars and concrete

The wear resistance of mortar and concrete samples untreated and impregnated with solutions of epoxide resin was tested. The compressive strength has a decisive influence on the abrasion of untreated mortar and concrete samples. The idealized diameter area of the maximal grain of the gravel in the sample has less influence on it. The wear resistance of impregnated samples with low compressive strength markedly increases. The hardener used influences the polymerization rate of the activated resin in the structure of samples, with time, and their abrasion is influenced also in this way.     

Heat of hydration in foamed concrete: Effect of mix constituents and plastic density

Foamed concrete is a versatile material that can be utilised in a wide range of construction projects, although the majority of it is consumed in high volume void filling applications. The advantages of foamed concrete are its high flowability, low self-weight, minimal consumption of primary aggregate, controlled low strength and excellent thermal insulation properties. However, in applications with high volume to surface area ratios, the relatively high Portland cement contents often used in foamed concrete, together with its high thermal insulating capacity, can lead to significant core temperature rises due to heat of hydration. This paper describes a laboratory study of the (i) temperature development of low-density (600 to 1200 kg/m³) foamed concrete with Portland cement contents between 300 and 600 kg/m³, (ii) influence of mix parameters on the temperature profiles, (iii) effect on cube strength, (iv) use of fly ash to ameliorate the problem and (v) provides a method to estimate temperature rise.     

加载速度对聚苯乙烯缓冲材料静态压缩特性的影响

聚苯乙烯缓冲材料是一种粘弹性材料，实验研究表明，该材料与时间有关的应力可分离为一个时间函数与一个应变函数的乘积，而回载速度对此材料的静态实习生 的影响可以略去注地。     

掺硅粉高水灰比水泥石高温强度衰退现象分析

实验发现,通过增加水固比为0.74获得的密度为1.65 g/cm3的低密度水泥浆（加有40%粗细搭配的硅粉）,在185℃、21 MPa养护48 h,抗压强度衰退率为20.3%,超声波强度衰退率高达50.6%。对该配方低密度水泥浆不同养护龄期的水泥石进行物相分析及微观形貌分析,认为其强度高温衰退的原因为:高水固比的水泥石机体内微孔隙本身较大,在高温养护过程中,随着水泥石机体内部物相的结晶化,微孔隙进一步增加,导致了强度衰退现象的发生,而且由于微孔隙对声波传输速度影响很大,这种衰退现象在声波强度上体现更加明显。通过外掺25%粒径为0.154 mm、密度为1.35 g/cm3的碳粉C-filler配制1.65 g/cm3低密度水泥浆,水固比降低为0.51,固相体积分数由32.0%升为46.0%,高温养护后水泥石密实、机体内微孔隙较少,强度衰退现象可得到改善。      

塑料排水管道破裂等级评价的分析研究

城镇排水管道在运行的过程中,常会由于各种原因造成管道破裂。这些破裂缺陷如何影响排水管道承载能力,是排水管道缺陷等级定义和评估要解决的问题。目前国内对排水管道破裂缺陷的研究比较有限,本文主要利用塑料管道作为模型试件,参照《城镇排水管道检测与评估技术规程》CJJ181-2012对破裂缺陷等级的划分,对试件模拟了叉形和圆形缺陷,并进行环刚度、抗压强度、外压破坏荷载试验研究,探讨管道破裂缺陷等级与缺陷数量的等效关系,以及缺陷位置和缺陷分布对管道破坏的影响。结果表明,1个2级叉形破裂缺陷与4个1级叉形破裂缺陷是等效的;1个4级圆形破裂缺陷与7个3级圆形破裂缺陷是等效的;相比排水管道顶部,管道侧壁是排水塑料管道的缺陷敏感区域;管道缺陷分布越均匀,对管道破坏程度越大。     

水淬锰渣在加气混凝土中的应用

参照工业上砂加气混凝土工艺,研究水淬锰渣作为硅质材料和轻质骨料制备加气混凝土的可行性,通过对两种加气混凝土进行性能测试及SEM微观观察,研究了其抗压强度、收缩性能和水化产物,并分析了两者性能之间的差异。     

再生EPS颗粒对砖粉泡沫混凝土性能影响的研究

再生EPS颗粒表面粗糙,且多粒径具有一定的级配,将其加入到废弃微粉新体系泡沫混凝土中,可改善其性能,拓宽其利用渠道。研究了再生EPS颗粒对砖粉泡沫混凝土各项性能的影响。试验结果表明,EPS的掺入使其干密度线性降低,掺量在4%~6%之间时,抗压强度下降缓慢,含水率大幅度下降,抗碳化能力增强,抗冻融能力满足规范要求,导热系数减小。与通过增加泡沫用量获得的同密度等级的砖粉泡沫混凝土相比,掺有再生EPS颗粒的混凝土抗压强度提高,含水率和吸水率降低,性能较为优越。     

稻杆纤维对改善泡沫混凝土抗压强度的研究

用化学发泡法制作了泡沫混凝土,并对稻杆纤维对泡沫混凝土抗压强度的影响进行了试验研究。通过对不同纤维直径、长度和掺量的组合试验,确定了最佳秸秆参数组合和最主要的影响因素,并分析了各个因素的影响作用。     

掺不同纤维的活性粉末混凝土力学性能研究

通过对16组分别掺入钢纤维和聚丙烯纤维的活性粉末混凝土试件进行抗压、抗折强度试验,并且对每组试件采用了三种不同的养护方案。试验结果表明:热水养护对活性粉末混凝土的抗压和抗折强度有较大幅度的提升,当温度达75℃时,提升幅度10%~30%;相比单掺聚丙烯纤维单掺钢纤维对活性粉末混凝土试块的抗压、抗折强度提升幅度更大,钢纤维含量为4%时活性粉末混凝土的抗压和抗折强度分别提高21%和53%;钢纤维掺量为2%和聚丙烯纤维掺量为0.3%并且经过75℃高温养护的活性粉末混凝土试块其抗压、抗折力学性能达到最优,其抗压强度达到168.4MPa,抗折强度达到31.57MPa。     

Compressive image broadcasting in MIMO systems with receiver antenna heterogeneity

In this work we consider image delivery in MIMO broadcast networks with diverse channel quality and varying numbers of antennas across receivers. In such systems, performance is normally constrained by the weakest users with either a low channel SNR or only a single receive antenna. To address both dimensions of heterogeneity, we propose a new analog image delivery system that adapts seamlessly along both dimensions simultaneously. Our sender scales the DWT coefficients according to a power allocation strategy, and generates linear combinations of the coefficients using compressive sensing (CS), before transmitting them with amplitude modulation. On the receiving side, the received physical layer symbols are passed directly to the source decoder without conventional MIMO decoding, and the DWT coefficients are recovered using a CS decoder.There are two main contributions of our system. First, integrating CS into MIMO transmission ensures that the reconstructed image quality at the receivers is commensurate with both the channel SNR and the MIMO channel dimension. Second, we introduce a power allocation strategy to achieve a performance tradeoff between receivers with different antenna numbers. Experimental results show that the proposed system outperforms both the analog reference SoftCast and the conventional digital system known as HM-STBC. The average gain is 2.92 dB over SoftCast for single-antenna users and 1.53 dB over HM-STBC for two-antenna users.