Recycling petroleum coke in blended cement mortar to produce lightweight material for Impact Noise Reduction

This work introduces a new way to use low-cost petroleum (pet) coke as lightweight aggregate in cement mortars to make sound barriers. The feasibility of adding pet coke in cement matrix was investigated: an in-depth characterization of as-received coke and the new lightweight mortar was made. The acoustic behaviour herein was assessed by constructing a large dimension mortar slab (made of cement and coke as aggregate) used as floor covering and measuring, according to the procedure described in international standards, the impact noise pressure level over the range of frequencies 100–5000 Hz. Impact Noise Reduction (INR) was also obtained and the results were compared to the ones experimentally obtained from a control mortar slab (made of cement and sand). Results showed that coke addition leads to a decrease in mechanical properties of resultant mortars, this is principally due to an increase of the porosity (∼60%). A gradual increase of impact noise insulation was observed in lightweight floor covering from middle to higher frequencies tested, reaching, within this range, a remarkable improvement of sound insulation compared to control slab (∼14 dB).     

Transient Thermal Response of Lightweight Cementitious Composites Made with Polyurethane Foam Waste

The development of low-cost lightweight aggregate (LWA) mortars and concretes presents many advantages, especially in terms of lightness and thermal insulation performances of structures. Low-cost LWA mainly comes from the recovery of vegetal or plastic wastes. This article focuses on the characterization of the thermal conductivity of innovative lightweight cementitious composites made with fine particles of rigid polyurethane (PU) foam waste. Five mortars were prepared with various mass substitution rates of cement with PU-foam particles. Their thermal conductivity was measured with two transient methods: the heating-film method and the hot-disk method. The incorporation of PU-foam particles causes a reduction of up to 18 % of the mortar density, accompanied by a significant improvement of the thermal insulating performance. The effect of segregation on the thermal properties of LWA mortars due to the differences of density among the cementitious matrix, sand, and LWA has also been quantified. The application of the hot-disk method reveals a gradient of thermal conductivity along the thickness of the specimens, which could be explained by a non-uniform repartition of fine PU-foam particles and mineral aggregates within the mortars. The results show a spatial variation of the thermal conductivity of the LWA mortars, ranging from 9 % to 19 %. However, this variation remains close to or even lower than that observed on a normal weight aggregate mortar. Finally, a self-consistent approach is proposed to estimate the thermal conductivity of PU-foam cement-based composites.     

Influence of a new type of additive on the performance of polymer-lightweight mortar composites

This paper shows how a new powder polymer additive (PPA), containing a waterproofing agent, a rheology control agent and air-entrainers, affects the workability, mechanical properties and setting times of polymer-lightweight mortar composites (PLMC). The waterproofing agent was a mixture of redispersible polyethylene vinyl acetate and redispersible silane based polymer powder. The rheology control agent was a redispersible hydroxypropyl carboxymethyl ether of patato starch based polymer powder. Air-entraining agent was a redispersible and an unmodified sodium laurly sulphate based polymer powder. Pumice fine aggregate at 0–3 mm size fraction was used as lightweight aggregate throughout the research work. In order to examine the effects of powder polymer additive on flowability and the performance when the additive is mixed in a mortar, the mixture proportions were set in four trial batches. The volume proportions of cement and pumice lightweight fine aggregate were fixed at 1:9, 1:8, 1:7 and 1:6, respectively, defining the mixture of mortar for measuring the compressive strength and workability of lightweight mortar. In this research study, PLMC mortars with 28 different mixture proportions (M1–M28) by weight of cement contents of 0.2%, 0.4%, 0.6%, 0.8%, 1.0% and 1.2% were adopted for the mortar mixture batches, respectively. Flow value of mortar was measured using a flow table method in accordance with the regulation in ASTM C230, “flow table for use in tests of hydraulic cement”. The target flow was fixed at 130 mm for each mixture proportion, which is regarded as the most suitable fluidity to secure workability at a site. For each mixture, 12 fresh plastic mortar samples were prepared according to the method specified in ASTM C305 and cured in a humidified atmosphere for 24 h, removed from the mould after 24 h, cured in water for 7 days, and then cured in air. The compressive strength test results were evaluated in accordance with ASTM C270.The suitability of using a new powder polymer additive in terms of workability and required compressive strength in PLMC mortar applications is also presented in this paper. It is observed that PLMC mortars have adequate strength and more convenient workability for their use in general masonry construction applications.     

Impact response of lightweight mortars containing expanded perlite

This paper describes the mechanical response of lightweight mortars subjected to impact loading in flexure. Expanded perlite aggregate with a bulk density of 64 kg/m³ was used at between 0 and 8 times by volume of Portland cement to yield a range of mortars with density between 1000 and 2000 kg/m³. Some specimens were reinforced with a polypropylene microfibre at 0.1% volume fraction and the dynamic fracture toughness was evaluated by means of an instrumented drop-weight impact system. Companion tests were carried out in compression under quasi-static loading to standardise the mixes. The compressive strength and elastic modulus scale as the cube of the relative density, defined as the ratio of the density of the mortar to that of Portland cement paste. Whereas the flexural strength and fracture toughness were both linearly proportional to the relative density of the mortar under quasi-static loading, there was an increase in their sensitivity to relative density at higher loading rates. Contrary to what is seen in regular concrete, fibre reinforcement led to an increase in the stress-rate sensitivity of flexural strength in lightweight mortars. For the same impact velocity, the stress-rates experienced by a specimen was strongly influenced by its density. While the stress-rate sensitivity of flexural strength dropped with a decrease in the mix density, that of the fracture toughness was consistently higher for the lighter mixes.     

Laboratory investigation of carbonated BOF slag used as partial replacement of natural aggregate in cement mortars

Direct mineral carbonation produces a material rich in carbonates and with reduced quantities of free oxides. The aim of this work was to show that such materials can be used in the construction domain. Basic Oxygen Furnace (BOF) slag from the steelmaking process has been traditionally seen as unfit for bounded applications due to its propensity to swelling, resulting from hydration of its high free lime content. Here, BOF slag was crushed to suitable particle sizes, carbonated in an aqueous solution of carbonic acid, and utilized to replace 50% of natural sand aggregate in cement mortars. The mechanical and chemical properties of these mortars were compared to mortars containing non-carbonated slags, and a standard cement mortar as a reference. Tests were conducted to determine mortar paste consistency and soundness, and cured mortar compressive strength and leaching tendencies. The results showed a satisfactory performance for all considered aspects (comparable with the reference) of the mortar sample containing 37.5 wt% (1.5 in 4 parts solids) carbonated BOF slag of <0.5 mm particle size.     

Lightweight mortar made with recycled polyurethane foam

This paper presents results of an experimental study on the use of rigid polyurethane foam wastes with cement-based mixtures to produce lightweight mortar. Several mortar grades were obtained by mixing cement with different amounts of polyurethane, aggregate and water. Dosages were varied to replace aggregates with recycled polyurethane, while the amount of water was optimized to obtain good workability. Rigid polyurethane was ground to particle sizes of less than 4 mm prior to use as an aggregate substitute. The characteristics of the test specimens were defined and they were tested in both a fresh and a hardened state. Results show that an increase in the amount of polyurethane affects the mortar, decreasing its density and mechanical properties while increasing its workability, permeability, and occluded air content. These results confirm that mortar produced with recycled polyurethane is comparable to lightweight mortar made with traditional materials.     

建筑隔声研究的进展

论文对近年来建筑隔声在研究和实践的几个主要方面进展,作一评述。所讨论的问题包括:质量定律与单值评价、轻钢龙骨板墙的隔声、楼板隔声的评价、侧向传声、声屏障及绿化降噪、窗的隔声和通风、敞开办公室的私密性。     

Fiber reinforced mortar affected by alkali-silica reaction: A study by synchrotron microtomography

Alkali-Silica reaction (ASR) is a physicochemical process that can deteriorate concrete and is a recurring engineering problem. In this study three different cylindrical samples affected by ASR were prepared: a plain mortar and two composite mortars containing fibers (polypropylene and a polymer hybrid), which were analyzed at the microtomography (μCT) beamline 8.3.2 at the Advanced Light Source (ALS). In general, three different features were observed during the 136 day observation period: (1) aggregate dissolution, (2) crack propagation from inside the aggregate, through the cement matrix, and at the ITZ, and (3) the alkali-silica gel filling cracks and voids. In addition, accelerated mortar bar tests were utilized to observe ASR's expansive effect in the plain and composite mortars, and the fibers' ability to restrain expansion due to ASR.     

Diffusivity evolution under decalcification: influence of aggregate natures and cement type

Since the decalcification of cement paste has been largely reviewed, we focus our studies on the influence of aggregate nature on this phenomenon in relation to the type of cement used, Ordinary Portland Cement or blended cement with fly ash and slag. Some characteristics of similar mortar mixtures where only aggregate nature differs (lime and siliceous sand) are therefore compared for the two types of cement before and after chemical decalcification induced by ammonium nitrate attack: mechanical strength, microstructure (porosity observed by mercury intrusion and profiles of oxide content trough degraded and sound zones determined by electronic microprobe analysis), transport properties (chloride ions diffusivity, gas and water permeabilities). The characterization of sound mortars underlines that siliceous aggregates promote less porous cementitious matrix. The duplication of ammonium nitrate attacks on same material allows testing the experimental parameters governing the degradation. The flows of calcium leached, the microstructure and the evolution of transport properties with decalcification suggest that limestone aggregates are not inert material. Consequently, for the mortars incorporating siliceous sand, the cementitious matrix is more decalcified and this leads to an amplification of ionic transports, especially through blended cement paste.     

Enhancement of recycled aggregate properties by accelerated CO2 curing coupled with limewater soaking process

Strengthening the attached old cement mortar of recycled concrete aggregate (RCA) is a common approach to enhance the RCA properties. Accelerated CO₂ curing has been regarded as an alternative way to enhance the properties of RA. However, the improvement of the properties of RCA was limited by the shortage of reactive components in the old cement mortar available for the carbonation reactions. In this study, a CO₂ curing process associated with a limewater saturation method was performed cyclically on cement mortar samples, aiming to enhance the properties of cement mortars via artificially introducing additional calcium into the pores of the cement mortars. The results indicated that the adopted treatment method promoted the level of carbonation which was demonstrated by higher CO₂ uptake by the limewater saturated cement mortar when compared to that without limewater treatment. After 3-cycles of limewater-CO₂ treatment, the density of the cement mortar slightly increased by 5.7%, while the water absorption decreased by over a half. For mechanical properties, the compressive and flexural strength were increased by 22.8% and 42.4%, respectively. Compared to the untreated cement mortar samples, the total porosity of cement mortar was reduced by approximately 33% and the densified microstructure therefore resulted in a higher microhardness.     

Properties of alkali-activated mortar and concrete using lightweight aggregates

This study reports the testing of 12 alkali-activated (AA) mortars and six AA concretes using lightweight aggregates. These tests aimed to explore the significance and limitations of the development of lightweight AA mortar and concrete. Ground granulated blast-furnace slag, which was used as source material, was activated by sodium silicate powder. The main parameter investigated was the replacement level of lightweight fine aggregates to the natural sand. The effect of the water–binder ratio on the compressive strength development was also studied in AA mortars. Initial flow and development of compressive strength were recorded for the lightweight AA mortar. For the lightweight AA concrete, many factors were measured: the variation of slump with elapsed time, the development of compressive strength, splitting tensile strength, moduli of rupture and elasticity, stress–strain relationship, bond strength and shrinkage strain. Test results showed that the compressive strength of AA mortar decreased linearly with the increase of the replacement level of lightweight fine aggregates, regardless of the water–binder ratio. The compressive strength of AA concrete, however, sharply decreased when the replacement level of lightweight fine aggregates exceeded 30%. In particular, the increase in the discontinuous grading of lightweight aggregate resulted in the deterioration of the mechanical properties of AA concrete.     

装配式轻质隔墙的隔声性能研究

近些年,装配式轻质隔墙由于在现场施工和造价等方面的优势被逐步推广,其隔声性能的研究也日益受到重视。由于隔声性能受多种因素影响,文章通过一系列实验,研究和分析了不同材料和构造对装配式轻质隔墙隔声性能的影响。结果表明,装配式轻质隔墙的隔声性能受墙体板材自身的声学性能影响较大,其共振频率主要出现在125~250 Hz;通过增加墙板层数,在墙体两侧加挂或外粘玻镁板,能有效提高墙体在中低频的隔声性能;在龙骨和墙板之间填充岩棉,能显著提升墙体在全频段的隔声性能,同时能有效改善低频共振对其隔声性能的影响。     

住宅浮筑楼板撞击声改善量试验

弹性材料应用于浮筑隔声楼板中,对于优化改善住宅楼板的撞击声隔声性能有重要意义,其中弹性减振层和浮板质量层的优选是关键技术措施。以发泡橡胶减振垫板和聚氨酯泡沫板为对象,试验、分析了其在不同加载方式下的测试厚度、动态刚度、共振频率、阻尼比等主要性能参数。然后以钢筋混凝土住宅分隔楼板为例,分别以发泡橡胶减振垫板和聚氨酯泡沫板作为弹性减振垫层,浇筑成型不同厚度的浮筑隔声楼板结构,测试其在不同厚度、不同作用时间下的撞击声压级及其变化规律,对比分析了其对住宅楼板撞击声改善量的影响。     

Quantitative composition of ancient mortars from the Notre Dame Cathedral in Tournai (Belgium)

A combined micro- and macroscopical approach was implemented for the quantification of the main constituents in a set of 41 ancient mortar samples from Tournai (Belgium). The samples range in age from Roman to Romanesque. The microscopical study consisted of point counting on thin sections prepared from these mortars. If sufficiently large samples were available, Image Analysis on plane polished surfaces was used to quantify the larger objects (> 1 mm) as lime lumps or ceramics. In spite of possible uncertainties, general conclusions about these mortars could be drawn. The Roman and Palaeochristian mortars are all comparable in containing a considerable amount of ceramic fragments, whereas their presence was not systematic during later times. The binder/aggregate ratios varied from 0.4 to 2.3. Romanesque mortars seem to have a less variable binder to aggregate content compared to the older mortar samples.     

外墙保温系统界面砂浆黏强度性能试验方法

通过比对试验,分析采用JG158-2004《胶粉聚苯颗粒外墙外保温系统》和DB33/T1054-2008《无机轻集料保温砂浆及系统技术规程》中界面砂浆黏结强度性能试验方法的差异,JG158-2004中的方法不能客观反映界面砂浆黏结强度的主要原因,并指出浙江地方标准DB33/T1054-2008的试验方法能较真实反映界面砂浆的黏结强度。     

绿色建筑楼板声学性能优化研究

绿色建筑对建筑健康性、舒适性和环境性提出了更高要求,满足楼板隔声性能要求是其基本的功能要求,但现实设计中却往往不被重视。建筑楼板作为分隔空间的构件,工程中应重视去解决楼板撞击声的隔声问题。以钢筋混凝土住宅楼板为基准,考虑了弹性材料类型、厚度、质量密度、动态刚度以及浮板质量和厚度等因素,给出了不同系列浮筑楼板做法,通过理论分析和试验,研究了其隔声性能的变化。研究结果对于建筑楼板的隔声降噪设计提供了技术支撑和案例经验,对于优化改善建筑隔声性能有积极意义。     

Reuse of spent catalyst as fine aggregate in cement mortar

This study examined the feasibility of reusing spent zeolite catalyst, after fluidized catalytic cracking, as a substitute for fine aggregate (sand) in cement mortars. The tested result shows that spent catalyst can replace up to 10% of fine aggregate without decreasing the mortar strength. In fact, the substituted mortars show higher compressive strength than the unsubstituted samples. The flowability of the fresh mortars decreases with increasing substitution level and the mortars incorporated with spent catalyst show less bleeding. In the hardened state, the water absorption of the resulting mortar increases with longer curing age, higher substitution level and smaller water-to-cement (W/C) ratio. Toxicity characteristic leaching procedure (TCLP) analysis confirms that the spent catalyst meets the standard, and thus should be classified as general non-hazardous industrial waste.     

The influence of mixing on the microstructure of the cement paste/aggregate interfacial zone and on the strength of mortar

The influence of mixing on the microstructure of the cement paste/aggregate bond has been investigated. Back-scattered electron microscopy was used in conjunction with quantitative image analysis to examine the microstructure of the interface between limestone aggregate and the cement matrix in a series of mortars. The distribution of porosity and anhydrous material along the paste/aggregate interface was shown to be dependent upon the relative abundance of water at the aggregate surface during mixing. Improvements in the interfacial microstructure were shown to correlate with improvements in strength and fracture properties. The interfacial zones seen in the limestone mortars were compared with a model interfacial system. A new classification system for two types of interfacial regions in mortar is proposed.     

Composites of scrap tire rubber particles and adhesive mortar – Noise insulation potential

In this work, composite materials made of adhesive mortar and scrap tire rubber particles were investigated with the main aim of characterizing their airborne noise insulation potential. Composites containing 10, 15 and 25% (in mass) of rubber particles with two different granulometry (between 18 - 35 mesh and between 35 - 60 mesh) were prepared, and the acoustic properties were evaluated considering the transmission loss and the sound absorption. Both transmission loss and sound absorption coefficient were obtained using an impedance tube with the One Microphone Method in a frequency range from 400 Hz to 2500 Hz. The results show an influence of the rubber particle size and mortar/rubber ratio on both acoustic properties. The apparent density estimation was carried out considering the relationship between the mass and dimensions of each sample, and as expected, composites presented lower density values than pure mortar. Composites containing 15% of rubber particles presented higher transmission loss values compared to pure mortar in all investigated frequency range. Composites containing 25% of rubber particles presented high values of sound absorption coefficient than those observed for pure mortar in a frequency range from 600 Hz to 2400 Hz. Composites presented lower values of tensile bond strength compared to the pure mortar. Composites and pure mortar were also characterized by scanning electron microscopy and X-ray microtomography in order to correlate the acoustic and tensile bond strength behaviors with microstructural properties.     

X-ray radiation shielding properties of cement mortars prepared with different types of aggregates

The types of aggregate used play an important role in determining the effectiveness of X-ray radiation protection of cement mortars. Cement mortars were prepared using fine aggregates obtained from six different sources. The influence of aggregate type on X-ray shielding properties was studied. The results showed that mortars prepared with barite and lead-laden recycled cathode ray tube funnel glass provided better shielding properties than mortars prepared with natural sand, natural crushed fine stone or crushed beverage glass. This is attributed to the use of dense aggregates being able to interact with X-ray radiation, thus reducing the depth of penetration. Due to the superior shielding properties of the mortar containing barite, it can be used to replace traditional sand mortar for applications as rendering or plastering materials for the construction of medical diagnostic and CT scanner rooms.