Stone Aggregate Research Articles

The Use of Carbon Fiber Cementitious Matrix Connection for the Strenghtening of Multiple-Leaves Masonry

The paper reports the results obtained by a numerical investigation carried out on a multi-ple leaf masonry characterized by very poor inner core leaf in mortar and stone aggregate strengthened by innovative technology based on the use of composite materials. The scope of the study is to predict and simulate the real performance of the masonry when re-inforced by means of Carbon fiber connector. The proposed reinforcement technology consists in inserting some transversal C-FRP joints through the thickness of the wall. All the connection joints were inserted by a constant distance along the height of the masonry wall. The joints consist of a bundle of unidirectional long fibers held by a special mesh and inserting in the thickness of the wall by means of a cementitious matrix. The ad-vantages of having replaced an epoxy resin with cementitious matrix are multiple and re-gard, on one hand an increase in the reinforcement capacity and on the other an improve-ment regarding the problem of the durability of the structural reinforcement which for FRPs is a real. To this aim, a finite element investigation was carried out, firstly, on the original non-reinforced masonry then on the reinforced model both subjected to eccentric loads. This scheme of load is very common in practice due to eccentricity of the self-weight resultant of the top storey when the thickness is reduced in respect to the ground floor.

Assessment of the Temperature of Waterproofing Membrane When A Recycled Crushed Glass Finish Layer Is Used On Flat Roofs to Protect From Sun Radiance

The aim of this research was to determine the impact of the use of a recycled crushed glass finish coat on flat roofs to reduce the transmission of heat from sun radiance to indoor spaces in the buildings. This research forms part of previous studies carried out by LiTa on the application of cool roof products to reduce the energy required for air-conditioning inside buildings.Many flat roofs are finished with crushed stone aggregates of natural or artificial origin. The use of recycled crushed glass as a cool roof is potentially a double opportunity to reduce the environmental footprint: it is a recycled material and it may reduce air-conditioning demand. In order to evaluate the real efficiency of recycled crushed glass, this research compared the results with other technical alternatives that are generally applied in real conditions.

Mechanical and thermal properties of concrete incorporating rubber and fibres from tyre recycling

In this paper, an analysis of the mechanical and thermal properties of a sustainable concrete incorporating crumb rubber (CR) and steel or plastic fibres partially coated with rubber (FCR) is presented. Whereas CR is normally used as aggregate in concrete, FCR is a new aggregate. FCR consists of fibres partially coated with crumb rubber recovered from the tyre recycling process, during granulation and before the total separation of rubber. The mechanical properties of concrete with rubber getting up to 100% volume substitution of stone aggregate have been obtained through compressive, bending, impact and wear resistance tests. Young’s modulus, toughness, toughness index and impact energy absorption are also studied. Concrete with FCR aggregate presents the same or even better mechanical behaviour than conventional rubberized concrete. The thermal conductivity (k) of concrete with FCR as aggregate is comparable to the k of concrete with CR, and it is also lower than the reference concrete. Finally, some proposals of constructive systems with rubberized concrete for thermal rehabilitation of buildings are analysed using pseudotime-dependent software, for which a significant reduction of the thermal fluxes can be observed.

MP08-07 SINGLE PULSE-PER-SECOND SETTING SIGNIFICANTLY REDUCES FLUOROSCOPY TIME DURING URETEROSCOPY

You have accessJournal of UrologyImaging/Radiology: Uroradiology I1 Apr 2017MP08-07 SINGLE PULSE-PER-SECOND SETTING SIGNIFICANTLY REDUCES FLUOROSCOPY TIME DURING URETEROSCOPY Todd Yecies, Anisleidy Fombona, and Michelle Semins Todd YeciesTodd Yecies More articles by this author , Anisleidy FombonaAnisleidy Fombona More articles by this author , and Michelle SeminsMichelle Semins More articles by this author View All Author Informationhttps://doi.org/10.1016/j.juro.2017.02.294AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookTwitterLinked InEmail INTRODUCTION AND OBJECTIVES Both patients and surgeons are exposed to ionizing radiation during endourologic procedures. Modern C-arms have settings that can be modified to lower radiation exposure, including “low-dose” and pulsed fluoroscopy. Pulsed fluoroscopy rates range from a standard rate of 30 to 1 pulse-per-second (pps). We present here the only known series evaluating the effect of 1 pps on fluoroscopy time and surgeon radiation exposure. METHODS A retrospective review of a single endourologist's operative records was performed over a 12 month period. Adult patients undergoing ureteroscopy were included. At the 6 month point, the switch from continuous “low-dose” to 1 pps “low-dose” fluoroscopy was made. Collected data included age, gender, body mass index (BMI), aggregate stone burden, stone multiplicity, laterality, laser and ureteral access sheath usage, operative time, fluoroscopy time, rates of failed or staged ureteroscopy and complication rates. Surgeon radiation exposure was measured using 1 dosimeter placed at the torso under the lead apron and 1 dosimeter overlying the chest outside the lead apron. Deep Dose Equivalent (DDE), Lens Dose Equivalent (LDE), and Shallow Dose Equivalent (SDE) were calculated using the EDE1 formula. RESULTS A total of 84 and 70 patients underwent ureteroscopy using continuous and 1 pps fluoroscopy, respectively. No significant differences were identified between the 2 groups with regards to patient age (p=0.96), sex (p=0.26), BMI (p=0.95), stone multiplicity (p=0.31), bilateral ureteroscopy (p=0.07), pre-stenting (p=0.99), staged (p=0.84) or failed ureteroscopy (p=0.99), ureteral access sheath utilization (p=0.10), or case duration (p=0.54). Patients in the 1pps cohort had a larger median stone burden (1.8cm IQR 0.9-2.8cm vs. 1.3cm IQR 0.8-2.0 cm, p=0.04). Median fluoroscopy time was reduced from 77 (IQR 54-115) to 16 seconds (IQR 13-24) using 1 pps (p<0.001). Monthly surgeon radiation exposure was reduced by an average of 64%, from 6.8±8.3 to 1.8±2.7 mRad DDE (p = 0.11), 120.6±101.4 to 49.2±66.6 mRad LDE (p=0.10), and 116.2±97.8 to 47.6±64.0 mRad SDE (p=0.11). Complications were rare without significant difference between the 2 groups. Image quality was acceptable in all cases using 1 pps fluoroscopy despite a maximal patient BMI of 82.2. The only technical compromise noted was increased motion artifact, which was easily avoided by allowing the C-arm to complete motion prior to image acquisition. CONCLUSIONS Use of single pulse-per-second fluoroscopy significantly reduces fluoroscopy time and lowers surgeon radiation exposure by 64%. © 2017FiguresReferencesRelatedDetails Volume 197Issue 4SApril 2017Page: e92-e93 Advertisement Copyright & Permissions© 2017MetricsAuthor Information Todd Yecies More articles by this author Anisleidy Fombona More articles by this author Michelle Semins More articles by this author Expand All Advertisement Advertisement PDF downloadLoading ...

MP50-06 HYDRONEPHROSIS AFTER URETERAL ACCESS SHEATH USE

You have accessJournal of UrologyStone Disease: Surgical Therapy V1 Apr 2017MP50-06 HYDRONEPHROSIS AFTER URETERAL ACCESS SHEATH USE Brandon Otto, Stephanie Stillings, and VINCENT BIRD Brandon OttoBrandon Otto More articles by this author , Stephanie StillingsStephanie Stillings More articles by this author , and VINCENT BIRDVINCENT BIRD More articles by this author View All Author Informationhttps://doi.org/10.1016/j.juro.2017.02.1594AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookTwitterLinked InEmail INTRODUCTION AND OBJECTIVES Ureteral access sheaths (UAS) are commonly used at the time of ureteroscopic lithotripsy (URSL) for the treatment of nephrolithiasis to facilitate multiple scope passages, stone extraction, and improve irrigation flow. There is a potential risk of ureteral injury and stricture formation with UAS use. We sought to review our UAS experience to better define both the risk of and predictors of post-operative hydronephrosis and ureteral strictures. METHODS 531 consecutive URSL with UAS (12/14 Fr) at a tertiary care center by a single surgeon were retrospectively reviewed between September 2010 to March 2016. We evaluated patient factors, operative details, and post-operative imaging in patients undergoing URSL with UAS. RESULTS Ureteral access sheaths were successfully placed in 506 (95.3%) of patients. Table 1 lists the demographics and stone characteristics of the cohort. The mean aggregate stone size was 15.4 mm. 272 (51.4%) patients had a pre-operative stent. 74 (14%) patients needed additional procedures to clear residual stone burden. 53 (10%) patients had hydronephrosis on post-operative imaging. The hydronephrosis was mild in 39 (73.6%), moderate in 12 (22.6%), and severe in 2 (3.8%) patients. Follow-up demonstrated that hydronephrosis resolved without intervention in 39 (73.6%) of patients. The mean time to resolution of hydronephrosis on imaging was 222 days. An additional 10 (18.9%) of patients had persistent hydronephrosis without evidence of obstruction on functional imaging. Four patients (7.5%) had persistent hydronephrosis and some degree of obstruction on functional imaging. Univariate analysis found that an unsuccessful UAS placement was the only predictor for the development of post-operative hydronephrosis (28% vs 9.1%, p=0.002) CONCLUSIONS UAS use at the time of URSL was successful in most patients and the risk of long-term obstruction is low. Post-operative hydronephrosis was observed in 10% of patients, however the majority of this hydronephrosis was mild and resolved without intervention. © 2017FiguresReferencesRelatedDetails Volume 197Issue 4SApril 2017Page: e685-e686 Advertisement Copyright & Permissions© 2017MetricsAuthor Information Brandon Otto More articles by this author Stephanie Stillings More articles by this author VINCENT BIRD More articles by this author Expand All Advertisement Advertisement PDF downloadLoading ...

MP75-12 PROSPECTIVE EVALUATION OF STONE FREE RATES BY COMPUTED TOMOGRAPHY AFTER AGGRESSIVE URETEROSCOPY

You have accessJournal of UrologyStone Disease: Surgical Therapy VII1 Apr 2017MP75-12 PROSPECTIVE EVALUATION OF STONE FREE RATES BY COMPUTED TOMOGRAPHY AFTER AGGRESSIVE URETEROSCOPY Noah Canvasser, Aaron Lay, Elysha Kolitz, Jodi Antonelli, and Margaret Pearle Noah CanvasserNoah Canvasser More articles by this author , Aaron LayAaron Lay More articles by this author , Elysha KolitzElysha Kolitz More articles by this author , Jodi AntonelliJodi Antonelli More articles by this author , and Margaret PearleMargaret Pearle More articles by this author View All Author Informationhttps://doi.org/10.1016/j.juro.2017.02.2160AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookTwitterLinked InEmail INTRODUCTION AND OBJECTIVES Previous retrospective and prospective studies have shown surprisingly low stone free rates (SFR) (approximately 50%) after ureteroscopy (URS) using stringent computed tomography (CT) criteria, although the aggressiveness of fragment extraction was not always quantified. Our goal was to determine SFR by CT after URS and aggressive fragment retrieval, quantified by the number of ureteroscope passes through a ureteral access sheath (UAS). METHODS We prospectively evaluated patients undergoing URS with laser lithotripsy at our institution from December 2015 to October 2016. UAS were used in all patients except those with distal ureteral stones. Every attempt was made to extract all stone fragments, regardless of size, after fragmentation. Patient demographics, stone number, size, and location, and the number of passes of the ureteroscope were recorded. SFR was determined using non-contrast CT scan approximately 8 weeks after the procedure. Stone free (SF) cohort was compared to the residual fragment (RF) cohort using the student′s T-test and the chi-squared test, and binary logistic regression identified factors associated with stone free status. Statistical significance was set at p < 0.05. RESULTS In total, 104 patients (141 renal units) underwent URS, with 67 patients (84 renal units) completing radiographic follow up to date. Mean number of stones was 3.3 and mean aggregate stone size was 13mm. Our overall SFR was 55%, with a mean number of ureteroscope passes of 44 (range 1 - 164). On univariate comparison between the SF and RF cohorts, SF patients had fewer numbers of stones (2.4 vs. 4.3, p=0.001), smaller aggregate stone size (11 vs. 15mm, p=0.02), and a smaller proportion of renal or renal and ureteral stones (54% and 15% vs. 66% and 26%, respectively, p=0.003). There were no significant differences in OR time, UAS size, or the number of ureteroscope passes (41 vs. 48, p=0.4) between groups. Binary logistic regression revealed no significant factors predictive of SF status. CONCLUSIONS SFRs by CT after URS are disappointingly low even with aggressive manual fragment retrieval. Larger sample size is likely to identify select cohorts of patients that benefit most from URS. © 2017FiguresReferencesRelatedDetailsCited bySorensen M (2019) Editorial CommentaryUrology Practice, VOL. 6, NO. 5, (298-298), Online publication date: 1-Sep-2019. Volume 197Issue 4SApril 2017Page: e1007-e1008 Advertisement Copyright & Permissions© 2017MetricsAuthor Information Noah Canvasser More articles by this author Aaron Lay More articles by this author Elysha Kolitz More articles by this author Jodi Antonelli More articles by this author Margaret Pearle More articles by this author Expand All Advertisement Advertisement PDF downloadLoading ...

SUSTAINABLE UTILIZATION OF DISCARDED FOUNDRY SAND AND CRUSHED BRICK MASONRY AGGREGATE IN THE PRODUCTION OF LIGHTWEIGHT CONCRETE

Nowadays, there is a considerable shortage in the availability of river sand and natural stone aggregate for the construction activities all around the globe and the way out is being worked out by the use of discarded foundry sand and crushed brick masonry aggregate for construction purposes. In the present study, river sand was partly replaced by the discarded foundry sand procured from steel moulding industries and the crushed brick masonry aggregate was used as coarse aggregate for the production of lightweight concrete. The experimental program involved casting of six distinct mixes with 0%, 20%, 40%, 60%, 80% &amp; 100% replacement of fine aggregate by discarded foundry sand. The mechanical and durability properties of the lightweight concrete were assessed for each of the six diverse blends. Even though the 80% and 100% replacement mixes were found to be less dense than the rest of the mix, the blend of 40% replacement acquired desirable mechanical and durability properties when compared to that of all other mixes. The optimum replacement level of the discarded foundry sand by mass to the river sand was 40%. The lightweight concrete produced by utilizing crushed brick masonry aggregate and discarded foundry sand (40% substitution level) can be employed in all major structural lightweight construction aspects and is ideally suited for sloped roof slabs and making architectural or decorative concrete blocks.

ASSESSMENT OF PALM KERNEL SHELLS AS AGGREGATE IN CONCRETE AND LATERITE BLOCKS

&lt;p&gt;Palm kernel shells were assessed as aggregate in concrete and laterite blocks. Results showed that laterite blocks reinforced with kernel shells at the optimum proportion of 1:4 (kernel shells:laterite) by volume were about 15% stronger than plain laterite blocks. The strength of laterite blocks reinforced with kernel shells also compared favorably with strength of sandcrete blocks which are popularly used as partitions in buildings. However, replacement of crushed stone aggregate with kernel shells in concrete blocks resulted in a strength reduction of about 50%. Therefore, palm kernel shells are not good substitutes for crushed stone aggregates in concrete.&lt;/p&gt;

Water Permeability Characteristics of Normal Strength Concrete Made from Crushed Clay Bricks as Coarse Aggregate

Water permeability characteristic of concrete made from crushed clay bricks as coarse aggregate is investigated and compared with concrete made from natural stone aggregate. For this, six different brick and five different natural stone samples were selected. Crushing strength of brick samples and water absorption of aggregate produced from them were also measured. Concrete samples of three different compressive strengths were prepared as per ACI mix design method from each of these aggregate samples. Compressive strength of concrete that could be achieved with brick aggregate varied between 19 and 28 MPa, whereas, for stone aggregate, compressive strength varied between 24 and 46 MPa. These samples were then tested for water permeability using the AT 315 machine as per EN 12390-8: “Depth of Penetration of Water under Pressure.” Experimental results and subsequent analysis indicate that water permeability of brick aggregate concrete is 225% to 550% higher than that of concrete made from natural stone aggregate of identical compressive strength. Water permeability was found to be directly related to compressive strength, water absorption, and porosity of hardened concrete. It was also observed that water permeability of concrete is influenced by water absorption of brick aggregate and crushing strength of brick.

The Application of Porous Concrete Filled with Soil and Sands for Low Volume Traffic Road

Pavements were usually planned as an impermeable layer to protect the sub grade from water intrusion which weakens the bearing capability of the sub grade. However, the more area to be protected from water ingress resulted in an abundant surface flow that cause reduction in green areas which impact on the reduction of water catchment areas. To anticipate this problem, the use of adequate strong pavement layer, but more environmentally friendly which allow the water to hang through the layer and absorbed into the sub grade that could cut the surface flow but keep up the potency of the layer is expected. The purpose of such layer is possible for low traffic volume road. The objective of this study is to design the adequate strength of porous concrete filled with soil and sand for low volume traffic road. The study was conducted using the experimental method, namely by reducing the proportion of fine aggregate in the mix design of conventional concrete. Crushed stone aggregate used is a uniform size of 1-2cm. The proportion of fine aggregate used is 30% of the proportion of coarse aggregate. The voids of the each type of porous concrete were then filled with soil, natural sand and volcanic sand. The filled samples were then assessed for water permeability, speed of absorption and compressive strength. The test results with a variety filler of porous concrete, namely soil, natural sand and volcanic sand were obtained and analyzed. The highest vertical and horizontal permeability's achieved with natural sand filled samples by 0.38cm/Sec and 0.364cm/Sec, respectively. The rate of absorption achieves the highest value of 0.337 for porous concrete filled with natural sand. The high compressive strength value of 5.71MPa belongs to the porous concrete filled with volcanic sand. However, it is recommended that the filled porous concrete is only suitable for low volume traffic road such as road shoulders, parking lots and pedestrian paths.

Laboratory Investigations on Reclaimed Asphalt Pavement (RAP) for using it as Base Course of Flexible Pavement

During Capacity augmentation of existing National Highway (NH) Projects, grade separated structures in terms of Flyovers, Vehicular underpass (VUP), Pedestrian underpass (PUP), Cattle underpasses (CUP) are proposed at regular intervals. Accordingly, existing road levels at approaches of these structures are required to be raised making the existing pavement materials redundant. Existing pavement materials are also obtained due to milling of existing pavement surface before laying overlay for strengthening. The present study is to assess the suitability of using these redundant pavement materials also called Reclaimed Asphalt Pavement (RAP) as potential subbase / base course materials for flexible pavement. It was observed from literature survey of various past studies that California bearing ratio (CBR) of 100% RAP is not suitable for its use as base of flexible pavement as per Indian Standards (IRC). Accordingly, attempts were made to improve strength of RAP in terms of CBR by mixing it with crushed stone aggregates, stabilizing it with cement and combination of both. In the present study, laboratory CBR tests have been conducted on RAP, mixture of RAP and crushed stone aggregates and also on mixture of RAP and crushed stone aggregates stabilized with various percentages of cement. It was observed that though un soaked CBR values of RAP were not influenced much due to its mixing with crushed stone aggregates and/or stabilization with cement, soaked CBR values increased substantially due to both mixing with crushed stone aggregates and stabilizing with cement. The soaked CBR value of RAP increases from 20% to in excess of 100% when it is mixed with crushed stone aggregates in various proportions and stabilized with small percentages of cement and thereby making it suitable for using it as subbase/base of flexible pavement. Modified proctor compaction tests were conducted on both RAP and mixture of RAP and crushed stone aggregates to established optimum moisture content for the preparation of CBR moulds for testings.

Influence of Crumb-Rubber in the Mechanical Response of Modified Portland Cement Concrete

The influence of crumb-rubber on the mechanical properties of Portland cement concrete (PCC) is studied by experimental tests and numerical simulations. The main hypothesis of the study is that replacing part of the stone aggregate with crumb-rubber in the mix modifies the energy dissipation during the cracking process and affects the concrete behaviour under monotonically increasing loads. The experimental research program characterizes the mechanical properties of PCC for three different types of concrete with a variable content of crumb-rubber. The experimental results showed that fracture energy and other properties are directly related to the rubber fineness used in the mixture. The material properties derived for these laboratory tests are used to study, by numerical models, its response through its damage evolution. The numerical model used to simulate the damage evolution of the concrete is the Embedded Discontinuity Method (EDM). One characteristic of the EDM is that it does not need to modify the mesh topology to propagate the damage through the continuum solid. For this study, the Disk-Shaped Compact Tension specimen geometry, normed by the D7313-13 of the ASTM, is used. Results showed that the numerical methods provide good approximation of the experimental curve in the elastic and softening branches.

Effects of grain size distribution on the packing fraction and shear strength of frictionless disk packings.

Using discrete element methods, the effects of the grain size distribution on the density and the shear strength of frictionless disk packings are analyzed. Specifically, two recent findings on the relationship between the system's grain size distribution and its rheology are revisited, and their validity is tested across a broader range of distributions than what has been used in previous studies. First, the effects of the distribution on the solid fraction are explored. It is found that the distribution that produces the densest packing is not the uniform distribution by volume fractions as suggested in a recent publication. In fact, the maximal packing fraction is obtained when the grading curve follows a power law with an exponent close to 0.5 as suggested by Fuller and Thompson in 1907 and 1919 [Trans Am. Soc. Civ. Eng. 59, 1 (1907) and A Treatise on Concrete, Plain and Reinforced (1919), respectively] while studying mixtures of cement and stone aggregates. Second, the effects of the distribution on the shear strength are analyzed. It is confirmed that these systems exhibit a small shear strength, even if composed of frictionless particles as has been shown recently in several works. It is also found that this shear strength is independent of the grain size distribution. This counterintuitive result has previously been shown for the uniform distribution by volume fractions. In this paper, it is shown that this observation keeps true for different shapes of the grain size distribution.

Preservation of Sand and Building Energy Conservation

Abstract Due to developmental need of humankind, growing trend of energy generation and consumption results more and more Green House Gas emissions, which contribute significantly to the phenomena of Climate Change and Global Warming. The issue is further compounded by huge ash generation from thermal power plants. Judicious utilization of such waste in a greener way is another challenge. It is estimated that by 2030, 40.8% of Indian population shall be living under Urban environment, and huge no. of dwelling units would be required. Sand, being one of the conventional constituent of Concrete, and also the non-renewable soft mineral, is being mined mindlessly across the Globe. The energy consumed by building sector is around 40% of global energy use. HVAC load is the major contributor in overall energy profile in buildings situated under Hot & Humid climatic zones in tropical countries. Solar heat gain is resulted through building envelope, and the conventional concrete and plastered masonry surfaces contribute significantly to the same. An experimental work has been carried out to produce sustainable energy efficient concrete with Portland Pozzolana Cement, Sand, Coal Ash from Thermal Power Plant, Stone aggregate and water. Test samples are prepared with reducing quantities of Sand and increasing quantities of Coal Ash for a Design Mix Concrete. While characteristic strength of concrete could be achieved with replacement of Sand by Coal Ash, thermal conductivity value of concrete is reduced, while compared with normal concrete of same Mix.

POSSIBILITY OF UTILIZING RECYCLED CONCRETE AGGREGATES IN HMA MIXTURE

Environmental and economic considerations have encouraged civil engineers to find ways to reuse recycled materials in new constructions. The objective of this research was studying the possibility of utilizing recycled concrete RC in a surface course of hot mix asphalt HMA mixtures and evaluating the volumetric and mechanical properties of hot mix asphalt mixtures containing recycled concrete aggregates. For this purpose, the performance of HMA mixtures containing various percentages of RC has been evaluated based on experimental tests, such as Marshall Stability MS, Marshall flow, Marshall stiffness, and Indirect tensile strength ITS. 90 specimens contain 5% asphalt bitumen and RC in various percentages (10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, and 100%) were mixed with virgin crushed stone aggregates and compacted by using Marshall Compactor to produce HMA specimen then Marshall mix design method was used to measure the optimum RC content.The results of MS and flows slightly decreased with the addition of RC. Marshall stiffness values for 10 percent RC was higher than the Control Specimen CS and the others. ITS values decreased with increasing RC.A mixture without recycledconcrete RC and varies gradation of maximum size of ( 1/2,1, and 1/2) incheswas prepared as control mix to CM test the Marshall stability –flow , ITS, and temperature sensitivities properties of mixes with 58% ( optimum percent) of RC that is obtained from a mix design that was investigated in this study. Specimens showedslightly improvements in Marshall Stability, flow, and ITS as compared with CM.

Metakaolin as a precursor of materials for applications in Cultural Heritage: Geopolymer-based mortars with ornamental stone aggregates

Potentialities and suitability of metakaolin-based geopolymers in Cultural Heritage have been explored. In particular, in order to evaluate their possible use as restoration materials in conservation of historic manufactures, mortars have been prepared by adding aggregates of Italian ornamental stones to alkali-activated metakaolin with binder/sand ratio of 1:1. To improve workability, geopolymer binders have been synthesized from metakaolin and sodium silicate solution with water/solid weight ratios between 0.33 and 0.66 and SiO2/Al2O3 and Al2O3/Na2O molar ratios of 3.70 and 1.04, respectively, and characterized by several techniques, including mechanical strength tests according to UNI EN 196-1. All binders display good mechanical properties, with compressive and flexural strength values as high as 72MPa and 6MPa, respectively, and decreasing with increasing water/solid ratio. The increase of water in geopolymer formulation has little negative effect on the aluminosilicate gel development and on the strength of these materials.Mortars display a homogeneous and compact matrix, bonded (silicoaluminate aggregates) or interlocked (carbonate) with aggregates. Their compressive strengths fall in the masonry mortars class M20 range. Their pore size distribution guarantees good breathability and adaptability to the substrate. The final materials mimic the original stones, with good aesthetic compatibility.

On the thermal and visual pedestrians' perception about cool natural stones for urban paving: A field survey in summer conditions

While cool materials are widely acknowledged for lowering surface and air temperatures, mitigating Urban Heat Island, reducing emissions imputable to active cooling systems in buildings, concerns arise about their impact on pedestrians' thermal and visual perception. These materials are typically applied on roofs, urban paving and building envelope: when the application is on non-usable spaces for pedestrians, it represents a win-win solution, since it decreases thermal stresses with no penalties for pedestrians. Instead, if the cool surface is installed over a passage area, glare and thermal radiative stress could affect pedestrians' comfort perception. In this work, a naturally cool, light colored stone is considered in the form of aggregates with varying grain size for cool roofing and paving application. Therefore, given its intrinsic passive cooling effect, this paper wants to experimentally investigate if such sustainable and cost effective material can create sensible thermal/visual discomfort perceived by pedestrians. To this aim, pedestrians' perception is investigated by means of in-situ survey and continuous monitoring in summer variable weather conditions, by taking into account several paving systems, i.e. grassland, asphalt, natural stones, and the investigated cool stone aggregates. The study demonstrated how in hot and sunny weather conditions, pedestrians prefer grassland, while asphalt is the least favorite material in any case. Cool gravel based surface does not produce thermal discomfort but it produces some visual discomfort due to glare issue, only in sunny weather conditions. In fact, variable weather conditions significantly affect pedestrians' sensitivity and their preference, also in the same summer season.

Structural Performance of Precast Floor Panel Using Oil Palm Shell Solid Waste

The palm oil industry in countries such as Malaysia, Indonesia, and Colombia has been aggressively expanding over the years. Inevitably, the production of palm oil from fresh fruit bunches has generated solid waste, such as oil palm shell (OPS). Such exploitation of OPS when utilized as coarse aggregate in concrete can reduce the reliance of the local construction industry on the use of natural stone aggregates, which are depleting quantitatively. When and if huge amount of OPS can be effectively used, it will not only be a green solution but also a great advantage to both the local palm oil industry and the construction business. Particularly to highlight in typical modern buildings made of reinforced concrete, slab panels consume the most concrete compared to the rest of structural components because they occupy a large space in the floor. Precast floor panels cast with concrete made with OPS can comply with the Industrialized Building System (IBS) because they are innovative, involving the precast system. This paper reports the structural performance of precast floor panels made with OPS concrete under two-line load (TLL), both at the early age of 28 days and a later age of 400 days. Panels tested at an early age failed in a brittle manner, whereas the others, at the later age, failed in a flexural behavior. Results based on parameters, such as service and ultimate load capacity, moment capacity, deflection, cracking characteristics, and ductility, also revealed that the panels performed generally better at a later age compared to an early age.

Experimental Studies on the Effect of Ceramic Fine Aggregate on the Partial Replacement of Sand Is an One of Ingredients in Concrete

Scarcity of the construction materials using the natural resources like sand aggregate and stone aggregate. The partial replacement of aggregates is required for the future generation of concrete structures for the environment sustainability. The depletion of the natural resource gets exhausted. We have thick over the alternate replacement of the materials. The replacement of materials calculating concrete strength in the various parameter like compressive strength of cube, split tensile strength of cylinder and flexure strength of prism. The result is interpolated in the replacement of the ceramic fine aggregate with the convention concrete. The comparisons of the parameter are compression strength of cube, split tensile strength of cylinder and flexure strength of prism.

Evaluación del comportamiento mecánico de asfalto natural a partir de muestras a temperatura ambiente provenientes de Caquetá, Colombia

El objetivo de esta investigación fue evaluar el comportamiento mecánico del asfalto natural por medio de la fabricación de muestras a temperatura ambiente. En primera instancia se realizó la caracterización del material con el ensayo de extracción cuantitativa del asfalto y así conocer el contenido de asfalto presente en el material, luego se procedió a fabricar muestras con la asfaltita pura en el compactador giratorio y por último se ejecutó sobre éstas el ensayo de Resistencia a Tracción Indirecta, RTI, en estado seco y en estado húmedo, para así conocer la viabilidad de su uso en vías terciarias, sin tener que someterla a altas temperaturas de fabricación y mezclado. Como resultado principal se evidencia que las probetas fabricadas a temperatura ambiente presentan resistencias muy bajas, por lo cual es necesario probar con la adición de agregados pétreos a la misma temperatura y emulsiones asfálticas.