Extrusion-based additive manufacturing of concrete products. Revolutionizing and remodeling the construction industry

Additive manufacturing is one of the main topics of the fourth industrial revolution; defined as Industry 4.0. This technology offers several advantages related to the construction and architectural sectors; such as economic; environmental; social; and engineering benefits. The usage of concrete in additive technologies allows the development of innovative applications and complexity design in the world of construction such as buildings; housing modules; bridges; and urban and domestic furniture elements. The aim of this review was to show in detail a general panoramic of extrusion-based additive processes in the construction sector; the main advantages of using additive manufacturing with the respect to traditional manufacturing; the fundamental requirements of 3D printable material (fresh and hardened properties), and state-of-the-art aesthetic and architectural projects with functional properties

Assessment of an expediency of binder material mechanical activation in cemented rockfill

This study is aimed to assess the expediency of applying the binder material mechanical activation in a cemented rockfill (CRF), consisting of ground smelter slag, waste of limestone and rock refuse at one of the largest mines, as well as at any other mines which use these components for CRF. The polynomial dependences have been obtained of strength variation of the CRF, which is used in the conditions of studied mine, on the time of consolidation and the ratio of backfill materials. In the CRF mixtures, the mechanical activation was carried out of the granulated blast-furnace slag, and the compliance has been assessed of CRF with the design strength of the backfill massif. In the studied conditions of the ore mine, with ratio of a binder material to filler of 0.5 and the existing cost of backfill materials, the use of mechanical activation of the binder material according to the two-stage grinding scheme turned out to be insufficiently expedient, since the production cost (materials + grinding) of the most economical backfill mixture is only 2.8% less compared with a basic composition. It is noted that the expediency of using the mechanical activation depends on the remoteness of the mineral raw material base, especially the main inert filler that significantly increases the cost of backfilling works. It is shown that in the operating conditions of other mines with a similar component proportion and a close rich mineral raw base, the mechanical activation of the binder material can be enough effective. It has been determined that with an increase in ratio of Cbin/Cin from 1.0 to 4.6, the difference in costs for the backfill mixture production in the considered compositions, where mechanical activation was performed, increases in a positive direction, but for the most economical backfill mixture, if compared to the basic one, it will be changed from 16.8 to 46.0%. An attention is focused on possible ways to increase the expediency of applying the mechanical activation of the binder material by means of forming the backfill massif with different strength along the height of the stope chamber

Experimental and Theoretical Study of Earth-Moist Concrete

No abstract

Influence of pozzolans and plasticizer on the performance of paste backfill in underground mines

Gideon Yowa investigated the possibility of using pozzolans to partially replace cement in mine filling to reduce the filling cost and make backfilling more environmentally friendly. He found that when pozzolans replace cement partially, the strength attained was comparable to the strength that pure cement attained. The results are useful for underground mines that use cemented paste fill

New modification of the hestenes-stiefel with strong wolfe line search

. The method of the nonlinear conjugate gradient is widely used in solving large-scale unconstrained optimization since been proven in solving optimization problems without using large memory storage. In this paper, we proposed a new modification of the Hestenes-Stiefel conjugate gradient parameter that fulfils the condition of sufficient descent using a strong Wolfe-Powell line search. Besides, the conjugate gradient method with the proposed conjugate gradient also guarantees low computation of iteration and CPU time by comparing with other classical conjugate gradient parameters. Numerical results have shown that the conjugate gradient method with the proposed conjugate gradient parameter performed better than the conjugate gradient method with other classical conjugate gradient parameters

A review of alternative approaches to the reduction of CO2 emissions associated with the manufacture of the binder phase in concrete

In this review we discuss a wide range of alternative approaches to the reduction of CO2 emissions associated with the manufacture of the binder phase in concrete. They are classified broadly as follows: (1) Use alternative fuels and/or alternative raw materials in the manufacture of Portland-based cements. (2) Replace Portland clinker with “low-carbon” supplementary cementitious materials (SCMs) in concrete. (3) Develop alternative low-carbon binders not based on Portland clinkers. The first approach mainly represents incremental improvements that can be achieved fairly easily and cheaply as long as suitable raw materials can be found. The second approach ranges from incremental improvements, if low levels of SCM substitution are used, all the way to major innovations for binders with very high Portland clinker replacement levels. The third approach is the most risky but also holds the greatest promise for truly significant CO2 reductions if it can be implemented on a large scale

SEM image analysis in permeable recycled concretes with silica fume. A quantitative comparison of porosity and the ITZ

Recycled aggregates (RA) from construction and demolition can be used in permeable concretes (PC), improving the environment. PCs have a significant porous network, their cement paste and the interaction between the paste and the RA establishing their strength. Therefore, it is important to evaluate the porosity in the interfacial transition zones. The porosity of the cement paste, the aggregate and the interfacial transitional zones (ITZ) of a PC with recycled coarse aggregates (RCA) and silica fume (SF) is measured by means of image analysis–scanning electron microscope (IA)-(SEM) and by mapping the chemical elements with an SEM-EDS (energy dispersive spectrometer) detector microanalysis linked to the SEM and, as a contrast, the mercury intrusion porosimetry technique (MIP). In the IA process, a “mask” was created for the aggregate and another for the paste, which determined the porosity percentage (for the anhydrous material and the products of hydration). The results showed that using SF caused a reduction (32%) in the cement paste porosity in comparison with the PC with RA. The use of RA in the PC led to a significant increase (190%) in the porosity at different thicknesses of ITZ compared with the reference PC. Finally, the MIP study shows that the use of SF caused a decrease in the micropores, mesopores and macroporesPeer ReviewedPostprint (published version

Kesan penggunaan koswer multimedia animasi visual terhadap pencapaian pelajar dalam mata pelajaran matematik

Ramai pelajar yang bermasalah dalam topik Pelan dan Dongakan. Ini kerana pelajar sukar untuk membayangkan objek yang tersembunyi melalui proses pengajaran dan pembelajaran (P&P) secara konvensional. Penyelidik telah membangunkan satu koswer multimedia animasi visual dalam topik Pelan dan Dongakan dengan menerapkan kesemua elemen-elemen yang dapat membantu meningkatkan kemahiran visual iaitu elemen animasi, video, audio, grafik dan teks. Seterusnya, kajian kuasi eksperimental ini turut dijalankan bertujuan untuk mengetahui kesan penggunaan koswer multimedia animasi visual terhadap pencapaian pelajar bagi mata pelajaran Matematik di sekolah menengah. Ujian Pra dan Ujian Pos digunakan untuk melihat perbezaan pencapaian yang signifikan selepas menggunakan koswer multimedia animasi visual yang menggunakan teori Kognitif Visual Wiley. Responden yang terlibat dalam kajian ini ialah seramai 40 orang pelajar Tingkatan Lima yang dibahagikan kepada dua kumpulan iaitu kumpulan rawatan dan kumpulan kawalan yang dipilih daripada sebuah sekolah di daerah Batu Pahat, Johor. Hasil analisis menunjukkan peningkatan skor min markah bagi pelajar kumpulan rawatan. Hasil analisis ujian-t (paired-sample-t-test) membuktikan bahawa wujudnya perbezaan skor min markah yang signifikan di antara markah ujian pra dan markah ujian pos bagi kumpulan rawatan. Oleh itu, terdapat perbezaan yang signifikan di antara skor min markah ujian pra dan ujian pos bagi pelajar kumpulan rawatan selepas menggunakan koswer multimedia animasi visual. Manakala instrumen soal selidik yang digunakan untuk melihat tahap penerimaan pelajar selepas menggunakan koswer multimedia animasi visual berdasarkan tiga aspek iaitu aspek isi kandungan, aspek interaksi dan aspek persembahan telah memeperolehi skor min yang tinggi bagi ketiga-tiga aspek tersebut. Dapatan kajian ini menggambarkan penggunaan koswer multimedia animasi visual dapat membantu meningkatkan pencapaian Matematik di dalam bilik darjah terutama yang tidak melibatkan pengiraan