Concrete Stone Research Articles

Высокоэффективный тяжелый бетон с использованием углеродсодержащего модификатора

Reducing the consumption of cement in the production of concrete mixtures has been a topical issue in the construction industry. The study aims to optimise the structure of concrete stone by selecting the particle size distribution of the components to nanoscale values. Such microfillers include silica fume, metakaolin, ashes, nanographite/graphene, etc. Thus, producing additives of complex action having a plasticising ability, as well as containing finely dispersed fillers forming binding material, is promising. Expandable graphite was dispersed in an aqueous medium and subjected to ultrasonic treatment using an ultrasonic bath with an 80 W generator. The particle size distribution in the graph-ite-containing suspension was studied using a laser diffraction particle analyser FritschNanoTeс with a wet dispersion system (measuring range of 0.01 to 2100 μm). Microscopic examination was carried out using a scanning electron microscope TESCAN Mira 3 with a magnification range of up to 1,000,000 times. In the present work, the physical-mechanical properties of heavyweight concrete containing modified oxidised expandable graphite were investigated. The results of microscopy and particle size distribution analysis of the graphite-containing suspension are presented. The research indicates the efficiency of ultrasonic treatment of a graphite-containing suspension and its effect on the strength characteristics of concrete. The presented results demonstrate the potential of ultrasonic treatment for additional disintegration of graphite particles in a graphite-containing suspension improving the physi-cal and mechanical characteristics of a concrete stone by adding this suspension to its composition.

Pattern of Intra Ocular Foreign Bodies in a Tertiary Care Hospital of Punjab

Purpose: To describe the epidemiological characteristics, management strategies and outcomes of intraocular foreign bodies (IOFB) presented in a tertiary care setup of Punjab.
 Study Design: Descriptive retrospective study.
 Place and Duration: Department of ophthalmology, Gujranwala medical college/teaching hospital, from January 2017 to December 2019.
 Methods: A retrospective review, of all the patients who had IOFB removal, was performed. Information regarding the nature and circumstances of injury, types of IOFB, operative procedure performed and patient’s pre-operative and post-operative Best Corrected Visual Acuity (BCVA) were analyzed. Descriptive statistics were used for analysis of data.
 Results: Record of 22 patients was retrieved. Out of which 18 (81.81%) were male and 4 (18.18%) were female. Mean age was 27.95 ± 9.325 years. Occupational trauma was the leading cause of injury (66.6%). Metallic objects were among the most common type of IOFB (66.6%) followed by glass, concrete stone (each 13.3%) and lead pencil (6.6%). Serious complications seen due to retained IOFB were phthisis bulbi (9.09%), retinal detachment (13.63%) and endophthalmitis (9.09%). On follow-up, 10 patients had BCVA less than hand movement (HM). 5 patients had BCVA of CF to 6/60, 3 patients had BCVA of 6/60-6/24 and 4 patients had better than 6/18.
 Conclusion: Most common cause of IOFB was occupational trauma and young age group of working class was the most common population affected. Treatment delay and complications contributed to poor prognosis. Ocular safety measures during high-risk work can reduce the risk of trauma.
 Key Words: Intra-ocular foreign Bodies, Retinal Detachment, Phthisis Bulbi.

Laboratory Evaluation of the Performance of Recycled Aggregate Concrete Containing Construction and Stone Factories Waste in Terms of Compressive and Tensile Strength

Nowadays, the rapid growth of waste production and, especially, construction wastes has become one of the main problems in societies. In the world, reinforced concrete structures are destructed for different reasons. These destructions generate increasing values of waste. Furthermore, there are several stone factories in every region that produce a large volume of decorative construction stone wastes. This experimental study has investigated the effect of using recycled aggregates of construction and stone factory wastes in concrete production. Different tests were performed on concrete samples in fresh state (slump) and hardened concrete (compressive and tensile strength and modulus of elasticity). The optimal percentage for replacement of each of the recycled materials was determined based on comparing the results of laboratory tests. Finally, a proper mix design was proposed for both recycled aggregate samples, and a comprehensive report of the results was also provided.

Characteristics of autoclaved lightweight aggregates with quartz tailings and its effect on the mechanical properties of concrete

Herein, we prepared autoclaved lightweight aggregates containing quartz tailings (QT) and determined their effect upon mechanical properties of concrete. QT, by pelletizing and autoclaving, were directly mixed with quicklime, cement and fine river sand to prepare lightweight aggregates, denoted as autoclaved QT aggregate (QTA). The prepared QTA were then used as coarse aggregates in manufacturing concrete. QT were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and laser particle size distribution analyzer; whislt the CaO/SiO2 ratio of QTA was investigated. The compressive strength and the structure efficiency of concrete containing the preapred QTA were thereafter determined. Results exhibit that QTA with the CaO/SiO2 ratio of 0.4 has the highest cylinder compressive strength of 20.6 MPa. The 28-d compressive strength of the QTA concrete is 74 MPa, retaining 95% of that of crushed stone (CS) concrete. The oven dry density of QTA concrete however dips 19% relative to the counterpart (CS concrete). It results in a 37.88 MPa·m3/t structure efficiency of QTA concrete, or 24% higher than the counterpart. The research is expected to provide an effective appraoch to reduce solid wastes paricularly QT.

Cost-effective design of long cylindrical shells of high-strength sand concrete

The use of high strength sand concrete (HSSC) is an alternative to high-strength crushed stone concrete. Its use is economically viable for those regions of Russia in which crushed stone belongs to imported building materials. So, crushed stone is supplied to the Republic of Tatarstan (RT) from the Ural, and local sand reserves are significant.Authors give the information on the cost-effectiveness of designing prefabricated and monolithic long cylindrical shells from HSSC of B60 and B80 classes compared to heavy concrete of B20-B80 classes.The determination of the forces in the shell elements was performed by using the LIRA-CAD software package (SP). The calculation of the elements of prefabricated shells was carried out in the stages of operation, manufacture, transportation and installation. It was carried out by an engineering method according to the methodology of current standards. Calculation of monolithic shells was performed using an SP. The density of heavy concrete, its strength and deformation characteristics were accepted according to the standards. The same characteristics for HSSC were based on the results of the experiments of the department “Technology of building materials, products and structures” (TBMPS) of Kazan State University of Architecture and Engineering (KSUAE).The performed calculations showed that the use of HSSC of B60 and B80 classes compared with the heavy ones makes it possible to obtain a significant economic effect in the Republic of Tatarstan (RT). Namely: to reduce the consumption of steel (up to 30.6 % in prefabricated shells and up to 23.7 % in monolithic), concrete (up to 15.9 % in prefabricated shells and up to 14.0 % in monolithic) and the total cost of materials (up to 18.9 % in prefabricated shells and up to 20.3 % in monolithic).

Experimental Research on Quality Parameters of Recycled Concrete.

Concrete itself, and issues relating to the recycling and management of reinforced concrete waste, are highly relevant, especially when urban expansion is being achieved by increased building construction volumes. This research investigates concrete waste and its (re)usage possibilities and resolves several major issues related to the question of how natural materials can be replaced by compounds made from concrete waste, thereby saving natural resources. The experiment was carried out using concrete mixtures, which were combined with natural aggregates and crushed concrete waste (fraction 4/16). The resulting mix of concrete was achieved using natural aggregates, thus replacing natural aggregates with waste, which had partially and fully replaced bulky aggregates with crushed concrete waste. The main aim of the investigation was to investigate how aggregates made from crushed concrete waste impact the properties of concrete. The exothermic effect on the concrete mixture during the hardening process was investigated. Furthermore, a macrostructural analysis of hardened concrete was conducted using scanned sample images; the adhesion zone between newly formed concrete stone and aggregates derived from natural rock from crushed concrete waste was investigated. Using an electron microscope to observe aggregate from crushed concrete waste and the contact zone of hardened cement stone revealed that the aggregate from waste adheres poorly with hardened cement stone. Furthermore, both the mechanical properties of new, hardened concrete and determined resistance to frost indicators are weak. Concrete density and compression strength decreased (by up to 8% and up to 18%, respectively), and absorption increased almost twofold due to aggregates derived from crushed concrete waste, since their cleavage strength indicator was twice as high, while water absorption was four times higher than that of natural aggregate. The results indicate that recycled concrete obtained from demolished buildings is environmentally sustainable and can be recommended for lower quality concrete for use in related engineering projects.

Pengembangan Jobsheet Praktik Batu Beton Sesuai Standar Kerja Nasional Indonesia Di PTB UNJ

This study aims to develop Jobsheet for concrete stone practices in Building Engineering Education as an effort to improve Student Competency Standards.
 This research is a Research & Development (R & D) research with a 4D (four-D) development research model. This research is basically carried out through four main stages, namely the process of defining (planning), the planning process (design), the process of development (develop), and the process of dissemination (disseminate). However, research only reaches the stage of the develop process. This study uses a questionnaire as a tool to test the feasibility of jobsheets through the validation of material experts and instrument development experts.
 The results showed that: Jobsheet Development of Concrete Stone Practice According to Indonesian National Work Competency Standards in the Building Engineering Education Study Program can already be implemented, based on the results of validations conducted by Jobsheet experts. Jobsheet validation results show a number above >81% thus the Jobsheet can be said to be very suitable to be used on the Jobsheet for concrete stone practice courses.

Stone Concrete: Composition Design and Preparation Technology

Amethod for designing a grout for making stone concrete depending on the required behavior of this material within a rockfill dam is described. Laboratory testing of stone concrete allowed us to establish the relationship between its strength and composition. Given strength parameters of stone concrete, the developed algorithm can be used to design a grout mix of cement, sand, mineral powder, and water with relative viscosity and stability such that the mix can be used to grout a rockfill to a required depth, filling well all the voids. The stone-concrete making cycle on the construction site is considered to determine the effectiveness of this type of work.

Implementing Multimedia-Based Integrated Learning of Concrete Construction and Entrepreneurship to Improve the Students’ Entrepreneurial Spirit

The objectives of the study were: (1) to formulate a multimedia-based integrated learning model of concrete construction and entrepreneurship and, (2) to measure the improvement of the students’ entrepreneurial spiritby implementing this developed integrated learning model in the classroom. This study was classified as a quasi-experimental study with a non-equivalent control group design. A pretest, treatment, andposttest were presented to the experimental and control groups. This study was conducted in 8 meetings at the Stone Installation and Concrete Constructionworkshop, Universitas Negeri Yogyakarta. Data were collected through tests to measure students' competence in entrepreneurship and Concrete Construction. The Concrete Construction skills were measured through product assessment. Testing of the validity and the reliability of the instruments used expert judgment and Cronbach Alpa respectively. Data were analyzed with a statistical t-test, with consideration of (a) the data normality, and (2) the homogeneity for the variance of each data group. This study concluded: (1) the integrated learning model was successfully formulated (2) there were positive and significant differences in the students' entrepreneurial spirit between the students treated with the developed integrated learning model and the students treated with the conventional learning model.

Stable microstructure of hardened cement paste – A guarantee of the durability of concrete

One of the main problems in modern concrete science is the low durability of reinforced concrete structures and constructions, especially those located in harsh climatic conditions and saturated with marine or mineralized water. Existing standards guide designers and builders to increase the density of concrete with increasing degree of aggressive impact, as well as through cyclical freezing of concrete structures, which taken as the main indicator of durability, air entrainment is mandatory. The problem is not only the provision of high frost resistance of concrete, but also finding a method of controlling it, which, as a rule, takes quite a long time. The destruction of concrete during cyclical freezing occurs not only due to the formation of ice in the pores of concrete, but also as a result of temperature stresses in concrete with ice, as well as the washing out of portlandite and aging of the cement gel – the main structural element of hardened cement paste. This means that the durability of the concrete can be ensured by maintaining the finely dispersed structure of the hardened cement paste, preventing crystallization of the gel from external influences or increasing its basicity. It is shown that only water reduction and pozzolanization, which provides residual portlandite content in Portland cement concrete stone 2–5 % by weight ensure the achievement of increased durability of concrete, reinforced concrete structures and constructions. A method is proposed to assess the stability of hydrate phases as well as the relationship between the durability and frost resistance of concrete.

Strength of concrete produced with different sources of aggregates from selected parts of Abia and Imo States of Nigeria

Purpose This paper aims to investigate the 28-day compressive strength of concrete produced with aggregates from different sources. Design/methodology/approach Coarse aggregates were crushed granite and natural local stones mined from Umunneochi, Lokpa and Uturu, Isuakwato, respectively, in Abia State, Nigeria. Fine aggregate (river sand) and another coarse aggregate (river stone) were dredged from Otammiri River in Owerri, Imo State, Nigeria. The nominal mix ratios were 1:1:2, 1:2:4 and 1:3:6, whereas the respective water–cement ratios were 0.45, 0.5, 0.55 and 0.6. Findings The compressive strength of granite concrete, river stone concrete and local stone concrete ranged 17.79-38.13, 15.37-34.57 and 14.17-31.96 N/mm2, respectively. Compressive strength was found to increase with decreasing water–cement ratio and increasing cement content. Practical implications Granite concrete should be used in reinforced-concrete construction, especially when a cube compressive strength of 30 N/mm2 or higher is required. Originality/value Granite concrete exceeded the target compressive strength for all the concrete specimens, whereas river stone concrete and local stone concrete failed to achieve the target strength for some mix proportions and water–cement ratios.

Functionality and durability of anti - graffiti - systems on concrete

Property damage and vandalism through illegal graffiti can be found worldwide. As graffiti increased, so did the interest in proper removal and the possibilities of a high-quality protection system. Anti- graffiti systems (AGS) can be used to protect objects and buildings from damage caused by graffiti. At present, AGS is still recommended for use in unspecified areas for plastics, metal, wood, brick, concrete and natural stone. In practice, it has turned out that no AGS is suitable for all surfaces. A specific reference to surface quality and properties is missing. For graffiti protection, however, the surface properties are of particular importance. They influence the liability of the AGS on the one hand and the removability of the graffiti on the other. This study is intended to demonstrate the extent to which concrete types and surfaces influence the functionality and durability of permanent AGS. This paper presents first results of practical tests on 180 concrete test specimens after currently one year of outdoor weathering. The results from three years of weathering are to be used to conclude the study for the development of an evaluation concept. Matching surfaces and AGS, with focus on the surface properties should be defined.

Experimental research on bearing capacity of special anchor

The bearing capacity of anchor can be greatly improved by adding anchor gills on the basis of traditional anchor. Taking the smaller particle pea stone concrete as anchoring cartridge, this paper conducted the bearing capacity pull-out test on special anchor with additional anchor gills and studied the relationship between bearing capacity of special anchor and layers of anchor gills, strength of pea stone concrete, the size of the block. The test results have revealed that adding anchor gills in anchoring section has an obvious effect on improving the bearing capacity of anchor and the bearing capacity of single-layer rod is 1.2 times - 1.7 times that of finishing rod. There is a non-linear relationship between the bearing capacity of special anchor and the strength of pea stone concrete when the strength of anchor gill is constant. However, as the concrete strength increases, the improvement of bearing capacity becomes smaller. Under the condition of single-layer rod, the bearing capacity of anchor increases with the increase of the size of the block, which shows that the bearing capacity of anchor is positively correlated with the thickness of concrete when the strength of anchor is constant.

The Effectiveness of Teaching Materials using Project Based Learning (PjBL) in Concrete Stones Practice Course

The magnitude of the impact of technological development (Industrial Revolution 4.0) has become a challenge for the world of education to continue to improve, even this situation demands very rapid change, which becomes a serious threat to the world of education, especially the vocational field. There are several problems in concrete rock practice learning such as (low student grades, not yet having teaching materials relevant to the demands of the industrial revolution 4.0, and not optimal use of technology in learning. Research development (R & D) with 4-D models (define, design, develop, disseminate) it aims to answer the challenges of the revolutionary industry 4.0 by creating effective teaching materials and learning strategies with video combination by optimizing the use of technology (smartphone). This research produces module and video that is valid (expert judgment), and effective that can evidenced from the increase in student learning outcomes (average pretest 50.72 and posttest average 86.04). Module teaching materials and video combinations are very suitable to be used for practical learning, especially in concrete stone practice course.

Bond strength between concrete and repair mortar and its relation with concrete removal techniques and substrate composition

This study investigates how concrete removal techniques affect substrates of different compositions, and as a result, the bonding with repair mortar. To this end, substrate surfaces of different concrete compositions, micro-concrete (MC), gravel concrete (GC) and crushed stone concrete (CC), were treated by using three commonly used removal techniques; hydrodemolition/water-jetting (WJ), jack-hammering (JH) and grit blasting (GB). Automated laser measurements (ALM) and the volumetric sand patch technique were employed to determine the surface roughness of the substrates. The effect of the substrates parameters such as aggregate size and uniformity on the bonding and failure modes was investigated. Uniformity of the substrates was evaluated by porosity measurements. According to the results, bond strength, surface tensile strength, failure modes and surface roughness were dependent on the aggregate size, aggregate shape and uniformity of mixture. The largest aggregate size and highest porosity along with the highest microcrack density and roughness belonged to CC mixtures. A high correlation was observed between the measured water transport and bond strength of samples. Micro-cracking and a weak interfacial transition zone (ITZ) seem to be the detrimental factors influencing the bond strength of samples treated with JH and WJ, respectively. The influence of WJ on the bond strength was dependent on the mix composition parameters such as aggregate size.

Influence of Polyfunctional Additive on Hardening Process and Properties of Cement Concrete

The paper presents results of research aimed at developing a new semi-functional concrete additive that provides an increase in rate and level of its strength growth while reducing energy costs to accelerate hardening process, as a basis for reducing energy intensity in manufacturing of concrete and reinforced concrete products and structures. Experimentally a rational ratio of components for a polyfunctional additive has been found of mass cement: a superplasticizer based on polycarboxylate resins (for example, “Stachement 2000” or “Relamiks PC”) – 0.5 %, ultradispersed microsilica (SiO2) – 1.0 %, sodium sulfate (Na2SO4), hardening accelerator – 0.5 %, aluminum sulfate (Al2(SO4)3), sealing additive structure ‒ 0.25 %. The mentioned components ensure the largest increase in strength of cement stone and structural heavy concrete. Results of derivatographic and X-ray phase analyses have shown that strength growth is based on formation of a fine-crystalline form of low-base crystalline silicates of CSH-silicate group, which complements traditionally formed C2SH by the reaction of threeand two-calcium silicate cement with water, as well as it is based on an increase in the number of neoplasms due to the reaction of Ca(OH)2 with amorphous SiO2 and ettringite 3CaO × Al2O3 × 3CaSO4 × 32H2O, being formed due to reactions with cement aluminates these are accelerating-compacting additive components, that in total provides an increase in density and strength of cement stone. While having the case with concrete, the effect is complemented by hardening the zone of contact between aggregate surface and cement stone due to the reaction between Ca(OH)2 and SiO2. These effects have been confirmed by growth (up to 38 %) of water which is chemically bound with cement in presence of a multifunctional additive in samples of cement stone, which is characterized by the largest strength. While using standardized testing methods, effectiveness of a multifunctional additive has been experimentally confirmed and it has been expressed in growth of quality characteristics and properties of structural heavy concrete: compressive strength – up to 40–60 %, flexural strength – up to 15 %, reduction of shrinkage – up to 50 % and water absorption – by 1.5–2 times, increase in frost resistance from brand F250 to F500, water resistance – from W6–W8 to W20.

Strength Development and Durability of Concrete Containing Recycled Roof Tile Aggregate

The use of recycled aggregate in new concrete has often been limited due to concerns over their quality and structural performance. This research aims to investigate the physical properties of recycled roof tile aggregate and its suitability for concrete production. Physical properties of recycled roof tile aggregate are compared to normal crushed stone aggregate. Effects of recycled roof tile aggregates on strength and durability of recycled roof tile concrete was compared with normal aggregate concrete using mechanical properties and durability tests. The experimental results showed that high water absorption and low strength of aggregate have a great effect on the workability and strength of the concrete containing recycled roof tile aggregate. Aggregate density, water absorption, crushing value and abrasion value of the recycled roof tile aggregate were found to be lower than crushed stone aggregate and concrete containing recycled roof tile aggregate had low strength and slow strength development. Similar durability performance of recycled roof tile aggregate concrete and normal aggregate concrete was observed except when exposed to freezing and thawing.

Experimental Study on Corrosion Resistance of Carbon Fiber Reinforced Concrete for Sea Crossing Bridge

Ma, L., 2018. Experimental study on corrosion resistance of carbon fiber reinforced concrete for sea crossing bridge. In: Liu, Z.L. and Mi, C. (eds.), Advances in Sustainable Port and Ocean Engineering. Journal of Coastal Research, Special Issue No. 83, pp. 423–428. Coconut Creek (Florida), ISSN 0749-0208.The traditional method of concrete corrosion protection and reinforcement is to repair damaged parts with fine stone concrete, so that it cannot restore the structural bearing capacity lost due to corrosion of steel bar, and has poor corrosion resistance. In order to solve this problem, the corrosion resistance test of carbon fiber reinforced concrete for cross sea crossing bridge was analyzed and studied. Firstly, the main reasons for the erosion of concrete structures in seawater were described. The main characteristics of corrosion damage were extracted, and the mechanical properties of carbon fiber reinforced concrete and steel bar were tested. The improved effect of different reinforcement methods on the durability of the specimen was analyzed, and the loading test was carried out after the reinforcement of the carbon fiber for the corroded beam. During the experiment, the influence of corrosion on the flexural behavior of RC beam and the regularity of carbon fiber reinforcement on corrosion beams were analyzed. The experimental results show that the durability of reinforced concrete members is enhanced by carbon fiber reinforced technology.

PRACTICAL USE OF NONMETALLIFEROUS RAW MATERIALS COPPER-NICKEL DEPOSITS

Aim.Copper-nickel deposits are located all over the world. A large amount of nonmetalliferous raw materials is formed, when they are developed. It moves into dumps and creates environmental risks for the environment. In the dumps magnesium-containing rocks prevail, which must be disposed of. The purpose of the work is to study the possibility of their use in the production of building materials.Methods.The chemical analysis was carried out by gravimetry, photometry, and atomic-absorption spectroscopy. The mineral composition was studied using X-ray phase analysis. The mechanical parameters were determined on a test hydraulic press.Results.It is established that the crushed stone from magnesiumbearing rocks is of high quality and can be used as a large aggregate in the production of concretes. It is shown that the concrete, containing crushed stone from ultrabasic rocks - verlites show the most compression strength. The lowest values has ordinary concrete on granite crushed stone. The type of hardening conditions also affects the strength of the resulting material. Sand from the sifting of crushing rock mass has angular shape of the grains and a mineral composition as in the parent rock. This contributes to the design of a dense structure of concrete stone, which increases its strength by more than 10%.Main conclusions.The use non-metalliferous raw materials will reduce the volumes of waste rock formed during the development of mineral deposits. In this case, it is possible to obtain a finished commodity product - crushed stone from magnesium-containing rocks and sand from their crushing. This will solve environmental, economic problems, as well as produce the necessary building materials for their own needs.

How concrete removal techniques affect the bonding between concrete and repair mortar

Many bonding failures between the substrate and repair mortar are attributed to too aggressive removal of the contaminated concrete and incorrect use of repair materials. To this end, in this study the effect of concrete removal techniques on substrates of different compositions and, as a result, on the bonding with repair mortar has been investigated. Substrate surfaces of different concrete compositions, micro-concrete (MC) and crushed stone concrete (CC), were treated by using three commonly used techniques: grit blasting (GB), jack-hammering (JH), and hydrodemolition/water-jetting (WJ). Automated Laser Measurements (ALM), sand patch tests and surface tensile strength measurements were applied to characterize the substrate surface. According to the results, the co-lateral effects of removal techniques such as WJ are dependent on the concrete mix composition. Moreover, WJ- and JH- treated samples achieved a lower surface tensile strength and bond strength compared to GB-treated slabs.