The effect of pumice as aggregate on the mechanical and thermal properties of foam concrete

Pumice is a porous rock, which is formed as a result of volcanic activity and does not include any crystal water. Its porous structure makes it lightweight and provides advantage for heat and sound isolation. Foam concrete is a type of lightweight concrete. Foam concrete is obtained by adding the foam obtained from the agent to the mixture of cement, water, and aggregate. Foam concrete is an environmentally friendly structure and insulation material which provides light, heat, and impact sound insulation that can be used in place of the building elements used in the interior-exterior walls and floors of all buildings. Because of the lack of coarse aggregate in the foam concrete mix, it has some structural problems and this limits its usage area. In this study, four different types of pumice aggregates and stone powder were used to overcome the structural problems of foam. The cement dosages (250 kg/m³), aggregate amounts (250 kg/m³), fresh concrete densities and w/c ratio (0.45) were kept constant in all foamed concrete mixtures. Then, physical, mechanical, and thermal conductivity properties of the resulting foam concretes were investigated. When the findings were evaluated, the most suitable type of lightweight aggregates for use in foam concrete have been determined in terms of compressive strength and thermal conductivity properties. In all aggregate groups, Nevsehir Pumice has the highest compressive strength while Karaman Pumice has the lowest thermal conductivity. However, when both properties were evaluated together, it was determined that the most favorable lightweight aggregate was Nevsehir Pumice.     

Utilization of bituminous limestone ash from EL-Lajjun area in production of lightweight Masonry block

The following work aims at minimizing the environmental impact of the solid wastes (ash) that is produced after the utilization of the bituminous limestone in thermal power stations and/or retorting processes. The laboratory tests have been selected with respect to construction needs and possible post construction conditions. Utilization of the various types of ash in the production of lightweight concrete block has revealed optimum results. The compressive strength of various ash–glass sand mixes has ranged between 19 and 76 kg/cm² at 28 days. The compressive strength of ash–tuff mixes has ranged between 54 and 63 kg/cm² at 28 days. Ultra light mixtures using ash–polyester with a density of 0.88 kg/m³ and a compressive strength of 21 kg/cm² at 28 days are produced at normal room curing temperature without the use of ordinary Portland cement. The high alkalinity of El-Lajjun ash is considered a disadvantage when utilized in normal concrete mixes for structural purposes. Ash only can be mixed with aggregates to produce lean concrete for blinding purposes for use in foundations.     

Factors Affecting Engineering Properties of Microfine Cement Grouted Sands

An experimental investigation was conducted in order to evaluate the influence of distance from the injection point and of parameters pertinent to the cement, the suspension and the sand on the effectiveness of microfine cement grouts. Three different cement types, each at three different gradations having nominal maximum grain sizes of 100, 20 and 10 μm, were used. Grouting effectiveness was evaluated by injecting suspensions with water to cement (W/C) ratios of 1, 2 and 3, by weight, into five uniform sand fractions with different grain sizes and eight composite sands with different gradations, using a specially constructed apparatus. Unconfined compression and permeability tests were conducted on the resulting grouted sand specimens, after curing for 28 and 90 days. Microfine cement grouted sands obtained unconfined compression strength values of up to 14.9 MPa and permeability coefficients as low as 1.3 × 10^?6 cm/s or by up to 5 orders of magnitude lower than those of clean sands. The W/C ratio and the bleed capacity of suspensions as well as the effective grain size and the permeability coefficient of sands are very important parameters, since they affect substantially the grouted sand properties and are correlated satisfactorily with them. The strength and permeability of grouted sands can increase, decrease or remain constant with distance from the injection point depending on the easiness of suspension penetration into the sands. The improvement of grouted sand properties with increasing distance from the injection point is consistent with the observed increase of the cement content of grouted sands.     

寒区再生集料水泥稳定碎石路基的力学和温缩性能北大核心CSCD

为解决废旧沥青混合料(RAP)和铁尾矿砂(ITS)固废处理问题,将两者充当砂石料掺加到水泥稳定碎石中,通过无侧限抗压试验、弯拉试验和温缩试验对水泥稳定碎石进行路用性能研究,分析了RAP和ITS掺量对水泥稳定碎石的影响。结果表明:RAP掺量一定时(25%),ITS掺量增加有利于提高水泥稳定碎石的抗压强度和弯拉强度,但会增大材料的温缩应变和温缩系数,降低温缩性能,其中ITS45(ITS掺量为45%)有较好的温缩性能;ITS掺量一定时(60%),RAP掺量增加不利于水泥稳定碎石的抗压强度,但可以提高水泥稳定碎石的弯拉强度,降低温缩应变和温缩系数,其中RAP70(RAP掺量为70%)温缩性能达到最优;与ITS45相比,RAP70有更宽泛的施工温度区间。     

Impacts of karst phenomena on engineering properties of limestone foundation bed,Ar Riyadh,Saudi Arabia

Evaluation of mechanical and petrophysical properties of the karst limestone became essential to avoid future risks in the construction of new urban cities built on limestones. Therefore, this study aims to evaluate the impact of karsts phenomena on engineering properties of limestone foundation bed at Ar Riyadh in Saudi Arabia. Three hundred core plugs were obtained by rotary drilling at depths ranging from the ground surface to 20 m collected from 24 boreholes in two sites: (1) karst limestone (KL) at Al Aziziyah district and (2) massive hard limestone (HL) at Hittin district in Ar Riyadh city, Saudi Arabia. Petrographic, SEM, EDX, and XRD analyses are used to identify the mineralogical composition and microstructures of limestone samples. The petrophysical properties included the ovendry density, P-wave, and porosity where the mechanical properties covered the uniaxial compressive strength (UCS), point load strength index (PLI), and rock quality designation (RQD) for the karst and hard limestone samples. KL is characterized by 17.11% total porosity, 14.71% water absorption, 32.1 MPa UCS, 1.70 g/cm³ ovendry density (γ dry), 51% weathered RQD, 5.49 MPa medium shear strength, and low modulus of deformation of the plate loading test. HL showed 11.63% total porosity, 9.45% water absorption 43.1 MPa UCS, 2.50 g/cm³ ovendry density (γ dry), 78% hard to fresh rock affinity RQD, and 9.93 MPa high strength and high modulus of deformation of the plate loading test. For the water absorption (%), KL at Al Aziziyah district showed a range of 12.85–17.80% averaged 14.71%. HL at Hittin district varied between 7.04 and 11.29% with an average of 9.45%. KL proved to be dense with ovendry density (γ dry) averaged at 1.70 g/cm³ while HL showed very dense affinity of 2.50 g/cm³. KL clarified a UCS range from 22.5 to 40.1 MPa and an average of 32.1 MPa while HL showed a range from 35.4 t o 48.1 MPa with an average of 43.1 MPa. KL is moderately weathered with RQD average of 51% while HL showed a hard to fresh rock affinity of 78%. Point load test clarified a medium shear strength with 5.49 MPa for KL and high strength of 9.93 MPa for HL. Plate loading tests indicated low and high modulus of deformation for KL and HL, respectively. Results of petrographical analyses and XED of limestone samples showed that the strength parameters of samples mostly composed of micrite (mudstone/wackestone) and dolomite in hard limestone of Hittin district. In Al Aziziyah district (KL), the samples mostly consist of foraminifera and high amount of calcite as in karst limestone (wackestone/packstone). Rock mechanical tests with combination of fabric analyses have shown that strength parameters depend not only on the amount of karst but also on the amount of allochem. Major geomechanical differences between the two types of limestone provide the proper base for prioritizing areas to alleviate future risks and sustainable urban planning for decision makers. The karstic limestone, therefore, is considered as an acceptable foundation bed for light engineering structures. However, for heavy structures and buildings, improving the foundation bed strength by grouting, cement injection, and mat foundations is necessary to avoid future failure risks.     

水泥固化稳定珊瑚礁岩、砂吹填材料路用性能研究

为实现岛礁公路建设资源集约化,提出采用水泥固化稳定珊瑚礁岩、砂作为路面基层材料。通过无侧限抗压强度、劈裂强度、回弹模量、水稳性、干缩和温缩试验,探究水泥固化稳定珊瑚礁岩、砂吹填材料强度、刚度、水稳性和收缩性等路用性能,为后续岛礁工程建设提供理论依据和数据支持。结果表明:在标养条件下,相同龄期的试样抗压强度和劈裂强度随水泥用量增加而提高,水泥用量相同的试样随龄期增长而提高;抗压强度增长基本符合线性规律。回弹模量随水泥用量增加而提高,但增幅逐渐减小。相同龄期下,试件饱和抗压强度相对于低于标准抗压强度;水泥用量和龄期越大,强度损失率越小,抗软化能力越强,如水泥用量6%试样28 d强度损失率与软化系数是水泥用量3%的93%和101%。试样失水率与干缩应变随龄期与水泥用量增加而增长,如水泥用量6%试样180 d失水率和干缩应变是水泥用量3%的1.35倍和1.27倍。温缩试验表明:温缩应变和温缩系数随水泥用量增加而增大,而随温度降低先增大后减小,处于30~45℃温度区间是岛礁公路建设最不利的状态,应尽量避免高温施工。     

Effect of animal borings on geotechnical properties of coralline limestone in NW Jeddah City, Red Sea Coast, Saudi Arabia

The coralline limestone covers large areas in the western and northern parts of Jeddah City. This coralline limestone is composed mainly of shelly limestone with pencil-sized animal borings. These borings increase the primary porosity and make the rock weak enough to have low-bearing capacity. The dry density (γ _dry) values of the study coralline limestone ranges from 1.54 to 2.09 g/cm³. The total porosity varies from 12.34 to 28.42 %. The absorption percentage fluctuates between 6.49 and 17.75 %. More than 95 % of the tested rock core samples have compressive strength less than 15 MPa. The compressive strength commonly decreased with the increase of animal borings. The obtained results cause the study coralline limestone weak enough to support heavy structures.     

Investigation of Cement–Bentonite Slurry Samples Containing PFA in the UCS and Triaxial Apparatus

Three mixtures of cement–bentonite slurry containing 28, 36 and 44 % PFA (as a proportion of cementitious materials) were tested using the unconfined compressive strength and triaxial apparatus to determine the stress–strain and shear strength relationships for samples cured for various periods. The samples were batched using 4 % bentonite and 20 % cementitious materials (by mass of water) and allowed to cure underwater once extruded from sealed moulds. Curing periods of 14, 28 and 90 days were selected to investigate the changes in behaviour at durations commonly specified (28 and 90 days) as well as providing insight into changing behaviour with curing (additional curing periods of 7 and 60 days were investigated on a smaller number of samples to increase understanding). Two rates of displacement were used (1.0 and 1.3 mm/min) and four confining pressures (0, 50, 100 and 200 kPa). Shear strength and strain at peak deviator stress of the samples do not appear to vary considerably with confining pressure. For samples containing 28 % PFA, the majority of physical properties exhibited by the cement–bentonite samples change with curing period up to 60 days, where after the properties become similar to those cured for 90 days.     

Effect of Natural Zeolite and Cement Additive on the Strength of Sand

It is widely known and well emphasized that the cemented sand is one of economic and environmental topics in soil stabilization. In some instances, a blend of sand, cement and other materials such as fiber, glass, nano particle and zeolite can commercially be available and effectively used in soil stabilization especially in road construction. In regard to zeolite, its influence and effectiveness on the properties of cemented sands systems has not been completely explored. Hence, in this study, based on an experimental program, it has been tried to investigate the potential of a zeolite stabilizer known as additive material to improve the properties of cemented sands. A total number of 216 unconfined compression tests were carried out on cured samples in 7, 28 and 90 days. Results show unconfined compression strength and failure properties improvements of cement sand specimens when cement replaced by zeolite at optimum proportions of 30 % after 28 days due to pozzolanic reaction. The rate of strength improvement is approximately 20–78 and 20–60 % for 28 and 90 days curing times respectively. The efficiency of using zeolite has been enhanced by increasing the cement content and porosity of the compacted mixture. The replacement of cement by natural zeolite led to an increase of the pH after 14 days. Chemical oxygen demand (COD) tests demonstrate that the materials with the zeolite mixture reveal stronger adsorptive capacity of COD in compare to cemented mixture. Scanning electron microscope images show that adding zeolite in cemented sand changes the microstructure (filling large porosity and pozzolanic reaction) that results in increasing strength.     

Flow behavior and microstructures of hydrous olivine aggregates at upper mantle pressures and temperatures

Deformation experiments on olivine aggregates were performed under hydrous conditions using a deformation-DIA apparatus combined with synchrotron in situ X-ray observations at pressures of 1.5–9.8 GPa, temperatures of 1223–1800 K, and strain rates ranging from 0.8 × 10^?5 to 7.5 × 10^?5 s^?1. The pressure and strain rate dependencies of the plasticity of hydrous olivine may be described by an activation volume of 17 ± 6 cm³ mol^?1 and a stress exponent of 3.2 ± 0.6 at temperatures of 1323–1423 K. A comparison between previous data sets and our results at a normalized temperature and a strain rate showed that the creep strength of hydrous olivine deformed at 1323–1423 K is much weaker than that for the dislocation creep of water-saturated olivine and is similar to that for diffusional creep and dislocation-accommodated grain boundary sliding, while dislocation microstructures showing the [001] slip or the [001](100) slip system were developed. At temperatures of 1633–1800 K, a much stronger pressure effect on creep strength was observed for olivine with an activation volume of 27 ± 7 cm³ mol^?1 assuming a stress exponent of 3.5, water fugacity exponent of 1.2, and activation energy of 520 kJ mol^?1 (i.e., power-law dislocation creep of hydrous olivine). Because of the weak pressure dependence of the rheology of hydrous olivine at lower temperatures, water weakening of olivine could be effective in the deeper and colder part of Earth’s upper mantle.     

Some Geological Considerations and Durability Analysis on the Use of Crushed Pyroclastics from Abakaliki (Southeastern Nigeria) as Concrete Aggregate

Samples of pyroclastic rocks from Abakaliki area (Nigeria) were subjected to geological and geochemical tests to determine the suitability and durability of the rocks as concrete aggregate. Petrographic analysis shows fine-grained texture and predominance of plagioclase (21–60 %) and shaley-muddy lithic fragment, while geochemical analysis classifies the rocks as alkaline. Analysis indicates that the pyroclastics would likely perform marginally well as concrete aggregates, especially in heavy Portland cement concrete and bituminous concrete. This is due to appreciably high values of natural moisture content, low bulk density, relative density and specific gravity, which suggests low durability, high voids and less aggregate absorption in concrete and bitumen mixes. The rocks are rated as moderate to high strength material on the basis of their unconfined compressive strength values, but are very likely to have low durability as buttressed by poor sulphate soundness test results, probably due to high amount of weak minerals. Analyses reveal that the Abakaliki Pyroclastics are not completely satisfactory as concrete aggregates source, despite their origin, texture, strength and economic availability. Hence, caution is required when they are used in concrete projects.     

Geomechanical evaluation of Pliocene natural aggregates as pavement materials

Asphaltic roads and constructions in Egypt annually consume a huge amount of aggregates. The physical and geomechanical properties of these aggregates have controlled their performance in which they are used. All road pavements require the efficient use of locally available materials if economically constructed roads are to be built. More than 650 million m³ of fine and coarse aggregates are herein selected to be the tonnage of the present study. The studied Pliocene aggregates have smoothed grading curves and neither a deficiency nor excess of any one particle size, generally produce good mixtures with fewer voids between particles. The litho-particles of coarse aggregates are composed mainly of granites, gneisses, granodiorite, gabbro, and quartz particles. The sand equivalent value of fine aggregates varies from 95 to 97 %. The specific gravity values of the studied aggregates vary from 2.72 to 2.74 gm/cm³ for coarse aggregate and range from 2.51 to 2.54 gm/cm³ for fine aggregate. The Los Angles abrasion value varies from 19 to 24 %. Both coarse and fine aggregates meet the international standards which are suitable for usage as subbase and surface course aggregates, respectively.     

气泡混合轻质土干湿循环和硫酸钠耐久性试验研究

采用水泥和地聚合物作为固化剂制备气泡混合轻质土,测试水泥轻质土（LCSC）和地聚合物轻质土（LGSC）在干湿循环和硫酸钠长期浸泡环境下的无侧限抗压强度和质量变化率,并相互进行对比,分析干湿循环级数和硫酸钠浸泡环境对其强度特性的影响规律。结果表明,标准养护地聚合物轻质土强度约为水泥轻质土的2倍;干湿循环后地聚合物轻质土强度随干湿循环级数衰减较快且破坏程度逐渐增大,水泥轻质土强度未出现明显衰减,与水泥轻质土相比,地聚合物轻质土抗干湿能力较差;硫酸钠溶液浸泡120 d后,地聚合物轻质土强度出现小幅下降,约为标准养护28 d试样的80%;水泥轻质土出现开裂破坏,与水泥轻质土相比,地聚合物轻质土抗硫酸钠侵蚀能力较强。     

Desiccation-Induced Volumetric Shrinkage of Compacted Foundry Sand Treated with Cement Kiln Dust

Foundry sand, an industrial waste, was treated with up to 12 % cement kiln dust content at comparative energy levels of British standard light, West African standard or “intermediate” (WAS) and British standard heavy (BSH) efforts at molding water contents ?2, 0, 2, 4 and 6 % of optimum moisture content. Samples were extruded from the compaction molds and allowed to air dry in the laboratory in order to assess the effect of desiccation-induced shrinkage on the material for use as a hydraulic barrier in waste containment application. Results recorded show that volumetric shrinkage strain (VSS) values were large within the first 5 days of drying; VSS values increased with higher molding water content, water content relative to the optimum moisture content. VSS generally increased with higher initial degree of saturation for all compactive efforts, irrespective of the level of cement kiln dust (CKD) treatment. A compaction plane of acceptable zones for VSS based on the regulatory value is ≤4 %. The influence of CKD treatment generally showed a decrease in the desiccation-induced volumetric shrinkage strain with increasing CKD content. This is largely due to the pozzolanic input of CKD. Finally, only the BSH compactive effort gave successful results of volumetric shrinkage strain at CKD treatment content of between 4 and 8 %, while 12 % CKD content produced successful volumetric shrinkage strain results at WAS and BSH compactive effort, respectively.     

Potential Application of Lateritic Soil Stabilized with Cement Kiln Dust (CKD) as Liner in Waste Containment Structures

This study evaluates the applicability of residually derived lateritic soil stabilized with cement kiln dust (CKD), a waste product from the cement manufacturing process as liner in waste repositories. Lateritic soil sample mixed with 0–16 % CKD (by dry weight of the soil) was compacted with the British Standard Light, West African Standard and British Standard Heavy compaction efforts at water contents ranging from the dry to wet of optimum moistures. Geotechnical parameters such as Atterberg limits, compaction characteristics, hydraulic conductivity, unconfined compressive strength and volumetric shrinkage strain were determined. Results indicate that the plasticity index, the maximum dry unit weight and hydraulic conductivity together with the volumetric shrinkage decreased with increased amount of CKD while the optimum moisture content and unconfined compressive strength increased with higher CKD content for all the efforts. When measured properties were compared with standard specifications adopted by most environmental regulatory agencies for the construction of barrier systems in waste containment structures, the resulting values showed substantial compliance. Besides developing an economically sustainable liner material, the present study demonstrated effective utilization of an industrial by-product otherwise considered as waste by the producers, in addition to a systematic expansion in the use of the lateritic soil for geotechnical works.     

Anisidine adsorption on Co-supported pumice

In this study, the adsorption of 2-, 3-, 4-anisidines on metal (Co)-supported pumice has been performed. The amount of cobalt on pumice was measured by ICP-OES analysis. Scanning electron microscopy indicated the formation of metal modification on the pumice surface. The samples were examined by Fourier transform infrared spectroscopic analysis of the adsorption process. The data show that after cobalt cation was supported on pumice, the adsorption of 2-, 3-, 4-anisidines was characterized by the bands at 2,958, 1,633, 1,450, 760, and 734 cm^?1. Adsorption of anisidines was observed only on Co-supported pumice, not on bulk pumice. The results show that the main adsorption process can only occur on the metal cation and metal oxide surface of pumice. Geometrical effects of isomers were monitored after adsorption.     

Municipal solid waste incineration fly ash sintered lightweight aggregates and kinetics model establishment

Municipal solid waste incineration fly ash blended with pine sawdust and shale, using a neotype trefoil rotary kiln to form lightweight aggregates, is an effective and a potential means method of fly ash disposal. The optimum sintering conditions of Trefoil rotary kiln were determined in terms of an orthogonal test by measuring the pellets’ bulk density, granule strength, 1 h water absorption. As far as the kinetics is concerned, an integral method of Coats–Redfern was introduced to analyze the kinetics characteristics of the mixture samples. Also, the kinetic triplets (apparent activation energy, pre-exponential factor and reaction order) were estimated by the reaction of kinetics model functions. It is shown that the optimum sintering conditions are as follows: (a) preheating temperature of 500 °C, (b) sintering temperature of 1130 °C, (c) holding time of 4 min. The optimum reaction models of the four stages are Avrami–Erofeev, Mample, Avrami–Erofeev and There-dimensional diffusion (Jander), respectively.     

Relevance of SEM to Long-Term Mechanical Properties of Cemented Paste Backfill

This paper is an attempt to relate the microstructure to long-term mechanical properties of the cemented paste backfill produced from a hard rock mine tailing from North Queensland in Australia bound with flyash-based geopolymer (geopolymer), flyash-blended cement (FBC), and general purpose cement (GPC). A relatively high slump (260 mm) paste backfill mix with 74 wt% solids has been used to prepare cylindrical paste backfill samples with a diameter of 50 mm and a height of 100 mm. The uniaxial compressive strength tests were conducted on all samples after curing for 112 days to obtain their strength, failure strain and Young’s modulus. Fractured samples were examined under scanning electron microscope to understand the failure mechanisms at the microstructural scale. The results show that binders significantly affected the mechanical properties of paste backfills (ANOVA, p < 0.05). The paste backfill bound with geopolymer gave the lowest strength and Young’s modulus, while the paste backfills bounded with FBC and GPC showed comparable higher strength and modulus values. This was attributed to the relatively well-packed paste backfills with less cracks and smaller pore sizes in these paste backfills bound with FBC and GPC binders. In particular, needle-shaped particles, which were originally identified in GPC, highly influenced the mechanical property of paste backfills. These results indicate that fly ash can be used to partially replace the cement as a binder for paste backfills to achieve economic and environmental benefits.     

Assessment of Cement Kiln Dust-Treated Expansive Soil for the Construction of Flexible Pavements

An expansive soil (black cotton soil) treated with up to 10 % cement kiln dust (CKD), a waste obtained from the manufacture of cement, was evaluated for use as a flexible pavement construction material. Laboratory tests were carried out on specimens compacted with British Standard light, British Standard light or standard Proctor (relative compaction = 100 %) energy. Results obtained show that the index properties of the soil improved with CKD treatment. Peak unconfined compressive strength of 357.07 kN/m² and California bearing ratio (CBR) of 7 % as well as resistance to loss in strength of 44 % were recorded at 10 % CKD treatment. Reduction in the particle sizes with curing period was observed when samples were viewed through the scanning electron microscope. The study showed that CKD can be beneficially used to improve the subgrade of lightly trafficked roads and as admixture in lime stabilization during construction of flexible pavements over expansive soil.