Concrete Technology

Self-healing concretes are being widely recognized as a remedial technique to improve the durability o f concrete. Although, few review papers on self-healing concret e were published, a strong review on all aspects of self-healing concrete cannot be found. In this paper, natural, chemical a nd biological processes of self-healing concrete te chnologies were completely reviewed. The main focus of the study is for the biological processes. The review presents a new insight into the research for the treatment of unexpected cracking o f concrete. The information presented in this paper can be considered significant for biotechnologists and bioprocess eng ineers to have comprehensive updates on the current status-quo of self- healing concrete.

Abstract This study investigates the strength reduction associated with incorporating calcium nitrate microcapsules in concrete. It also proposes modifications to the calcium nitrate micro encapsulation procedure to minimize the concrete strength reduction. These modifications consist of altering the continuous phase composition and keeping that of the aqueous phase the same. Amounts of 1%–10% of low Hydrophilic-Lipophilic Balance (HLB) emulsifier and 0.1%–1.0% of oil-soluble sulfonic acid catalyst (by weight of water in the aqueous phase) were dissolved in an organic solvent to prepare the continuous phase. The average diameter and shell thickness of the produced microcapsules were characterized using Scanning Electron Microscopy (SEM). Mortar mixes were prepared for various calcium nitrate concentrations of microcapsules that were encapsulated using the modified procedure. The compressive and flexural strengths and the elastic modulus of the mortar mixes were determined. The results show that the use of the modified encapsulation procedure resulted in a statically insignificant reduction of both compressive and flexural strengths compared to the original encapsulation method. The SEM micrographs of the fracture surface of the samples containing microcapsules showed that the strength reduction may be due to the agglomeration of the un-hydrated particles on the surface (shell) of the microcapsules. The compressive and flexural strengths of samples prepared using the proposed encapsulation procedure were enhanced compared to those prepared using previous encapsulation techniques.

Reactive Powder Concrete (RPC) is a type of ultra-high performance cement based composite with high strength and ductility. RPC was developed in the 1990s by Bouygues' laboratory in France. It is a special type of concrete which has properly optimized micro grain, binder phase and steel micro-fibers. RPC can achieve compressive strength values between 150–800 MPa, while traditional concrete which is used in current structures usually has 20–50 MPa compressive strength. In addition, its high performance under flexural loads is the most important advantage of RPC in the field of civil engineering. RPC has the potential to compete with steel from the point of aesthetics and structural capability. One of the curing methods to enhance the strength of this composite material is autoclaving. Autoclave curing needs additional SiO2 source to fill micro pores and strengthen hydration products. In the scope of this study, the effect of volume fraction of steel micro-fibers and silica fume dosage as SiO2 source on mechanical properties of RPC under autoclave curing was investigated. High performance cementitious composites were produced with 0%, 1%, and 2% volume fractions of steel micro-fibers. Nine mixtures with three different silica fume dosages were produced. Workability of fresh state and flexural-compressive strengths of hardened specimens were determined. In addition, fracture energies of the mixtures under bending loads were evaluated.

This experimental field study interrupted the protection current offered by Impressed Current Cathodic Protection (ICCP) to ten in-service reinforced concrete structures. The study aimed to identify the long-term effects of ICCP after it was recognised that some of the systems are now reaching the end of their design life and require a significant level of maintenance. It was found that after five or more years of ICCP, the steel remained passive for at least 24 months after interrupting the protection current despite chloride contamination that would represent a corrosion risk.

The mechanical properties of sandcrete block greatly influenced the durability of structures built from it. This study was carried out to assess the compressive strength of sandcrete blocks produced in two major developmental and rapidly urbanizing zones of Delta State, Nigeria. 150 and 225 mm sandcrete blocks were samples from 18 blocks moulding factories in Ndokwa East and Ughelli North Local Government Areas of Delta State, Nigeria. Five sandcrete block was sampled from each block moulding factory, at the rate of 9 factories per Local Government Area. The compressive strength of the sampled blocks was in accordance with the ASTM International standards. The results of compressive strength test showed that the compressive strengths of the blocks, regardless of the block size ranged from 0.61 to 16.19 MPa. Analysis of the results revealed that apart from the customized blocks, the compressive strengths of all the other blocks fell below the Nigerian Industrial Standard (NIS) recommendations of 2.5 MPa for non-load bearing walls. The general poor quality of the sandcrete blocks is attributed particularly to the poor mix ratios adopted by the block producers which fell short of NIS recommendations. Thus, this study recommended that standard regulatory agencies should closely monitor all the block making factories in the state, to ensure that sandcrete blocks produced or brought into the state met NIS recommendations.

The work presented below is part of the results of a research project at UPM.
The objective of the research consisted in the reconstruction of a selection of architectural projects chosen for both, its importance in the historical context and its geometry; so that the development of non-uniform rational Bsplines (NURBS) could be implemented as a tool for the graphical representation of architecture.

NURBS can represent complex geometries with precision (such as the hyperbolic paraboloid), either in the form of models or virtual models. Thus one can hypothesize and even complete information gaps -in the absence or loss of documentation-, of old or not constructed architectural projects.
During the communication it is intended to show the results achieved in one of the specific cases analyzed: the non-built market for Mexico in 1956, by Félix Candela.

Concrete plays a significant role within the development of infrastructure resulting in utilization of enormous amount of concrete. On the opposite facet, price of concrete is attributed to price of its ingredients that is scares and high-priced, this resulting in usage of economically various materials in its production. This demand is drawn the eye of concrete with partial replacement of coarse mixture with ferrochrome scum aggregates. The cubes and cylinders were tested for compressive strength and split durability when a natural process amount of 7days, 14days and 28days respectively and compared to traditional combine concrete. The ferrochrome scum concrete exhibited higher strengths compared to traditional coarse mixture concrete.

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In the present paper, a numerical and experimental study about creep and shrinkage behavior of a high strength self-compacting concrete is performed. Two new creep and shrinkage prediction models based on the comprehensive analysis on the available models of both conventional concrete and self-compacting concrete are proposed for high strength self-compacting concrete structures. In order to evaluate the predictability of the proposed models, an experimental program was carried out. A concrete which develops 60 MPa within 24 h was used to obtain experimental results. Several specimens were loaded: (i) at different ages and (ii) with different stress-to-strength ratios. Deformation in non-loaded specimens was also measured to assess shrinkage. All specimens were kept under constant stress during at least 600 days in a climatic chamber with temperature and relative humidity of 208C and 50%, respectively. Results showed that the new models were able to predict deformations with good ac...

La velocidad de succión capilar es un parámetro indicativo de las propiedades de transporte del hormigón, incorporado como límite prescriptivo en el Proyecto de Reglamento Argentino CIRSOC 201-2005 para estructuras en ambientes agresivos. El método está normalizado por IRAM 1871-2004. Allí, la finalización de la absorción capilar se establece cuando la variación de masa de la misma en intervalos de 24h resulta menor a 0,1%. Los aditivos reductores de agua permiten bajos contenidos unitarios de agua y, por lo tanto, menor volumen de pasta en el hormigón y menores propiedades de transporte. En este trabajo se examina el mencionado límite 0,1% a través de resultados de velocidad de succión capilar obtenidos bajo norma. Se analizan limitaciones de la representatividad del método, que pueden surgir cuando es aplicado a hormigones de muy baja capilaridad. Asimismo, se observa la capacidad del método para cuantificar diferencias entre distintos hormigones con muy baja capilaridad.

This paper shows the results of an experimental work on concrete containing different parts of silica fume. Silica fume is a by-product of the silicon and ferrosilicon alloy production the main aim of this work is to find the optimum quantity of silica fume to reinstate cement in order to get better properties of hardened concrete. To accomplish the purpose, workability, compressive strength, flexure strength, split tensile of concrete containing silica fume were find after 7, 14 and 28 days of curing. Furthermore, judgment between normal concrete and modified concrete containing 5%, 10% and 15% of silica fume was studied. The water/binder ratio was kept constant at 0.45 throughout the mixing process. The outcomes of this investigation indicate that compressive strength and flexural strength gives the highest improvement of 10% and 15% silica fume replacement respectively. This paper can be a useful basis of information for other researchers to understand the profit and bad effects of silica fume and have a summary of its optimum percentage when dealing with concrete.

Concrete is basic construction material used for many kind of structure. However, in the majority essential structures such as nuclear plants, Power plants, Weapon Industries, weapons storage places, water retaining structures like dams, & etc., concrete structures have to be designed as self-protective structure endow with defense against any disaster or consciously engendered unpleasant incidents such as terrorist attack, war, missile attacked by war jets, and dynamic loading, dynamic local impact damage and global damage generated by kinetic missiles (steel rods, steel pipes, turbine blades, etc.). This study inquisitively is paying attention on verdict the numerical simulation on the behavior of concrete structures against local impact effect generated by hard missile. The fallout conquer from this study can be used for making design counsel and design procedures for seminal the dynamic retort of the target to foil local and global impact damage. This paper only endow with the appraisal of prior analytical model investigation connected with our study.

h i g h l i g h t s Solidification and stabilization of coal bottom ash waste (CBA) using CEM1 as the binder have been evaluated. Toxic elements can be immobilized successfully to nearly zero even in the case of a low CEM1 content. Based on leaching and compressive strength results, CEM1/CBA mixtures can be considered for the construction industry. a b s t r a c t Solidification and stabilization of coal bottom ash waste (CBA) using CEM1 as the binder have been evaluated in case of leaching as well as the possibility to use this mixture for the construction industry. For this, the CEM1/CBA mass ratio has been varied between 0.5 and 2 and heavy metals leaching of Cu, Cd, Ni and Pb evaluated. Two types of crushed block and whole block leaching tests have been conducted to determine the leaching properties of deionized water, acetic acid and nitric acid leachates. It has been demonstrated that all elements can be immobilized successfully to nearly zero even in the case of a low CEM1 content. Furthermore, it has been shown that more heavy metals leached from the matrix when acetic acid used compared to other leachates. Next to this, the mechanical properties have been tested. After 56 days a compressive strength between 25 and 40 MPa has been measured from 0.5 to 2 CEM1/CBA mass ratios. Based on leaching and compressive strength results, CEM1/CBA mixtures can be considered for the construction industry.

Several mineral and chemical admixtures,
commonly used in structural concrete, were studied to assess
their effect on the fresh and hardened properties of
cementitious systems. Pozzolana examined here is ZnO
nanoparticle, while chemical admixtures were air-entrainer,
water reducer/retarder and two super plasticizers. The
received materials were characterized for their chemical oxide
composition, crystalline and amorphous content, density,
fineness, specific surface area, and particle size distribution.
Several tests were conducted on binary and ternary mixtures
to assess the performance of the cementitious system.
Additionally, a limited number of investigations are dealing
with the manufacture of nano sized cement particles and the
development of nano binders.
The study attempts to evaluate the impact of six different
additives, including natural additives and nano-additives in M
40 grade concrete. The test design is adopted on for the mixes
and the optimum amount of admixtures are determined for
concrete mixes and their performance is analyzed. The
experimental work has been carried out by addition of nano
ZnO in 0%, 0.2%, 0.5%, and 1% brings to change in properties
of the concrete.
Thus the property of mixture can be enhancing on their
composition with decrease in weight on ZnO nano concrete.
The use of chemical and mineral additives is the most effective
way to improve the quality of the concrete, and to give them
specific properties.

Key Words: Chemical admixtures, Zinc Oxide (ZnO), High
strength concrete, Pozzolana

Addressing the use of reinforced concrete for restoration at archaeological sites, Paola Pesaresi, the conservation architect with the Herculaneum Conservation Project, reviews how concrete was employed at Herculaneum during the first half of the twentieth century, and how the subsequent deterioration of the concrete elements incorporated into the site is now being handled by authorities there.

This 1992 paper reports on work in progress in 'Design for Energy Efficiency,' one of fifteen task areas of the U.S. Department of Energy sponsored Energy Efficient Industrialized Housing research program. In this task, design studies establish visions of energy efficient housing systems and technologies for the year 2030 from which shorter term research activities can be defined. One study for a 'Multifamily Concrete Panel House in a Hot-Arid Climate,' a primarily passive solar design, responds to trends anticipating demand for small, minimum cost multi-family houses in sun-belt suburbs, diversifying household composition, declining wood resources, advancing concrete technology, increasing site density, and competition for cooling energy. Task background and progress is presented with an emphasis on passive solar systems and goals.

أجريت هذه الدراسة لغرض الوصول إلى نتائج معملية واضحة عن تأثر خواص الخرسانة المتمثلة في مقاومتها للضغط والخواص التي لها علاقة مباشرة بديمومتها مثل: المسامية، نسبة الامتصاص والنفاذية وذلك عند إضافة نسب مختلفة من ألياف البولي بروبالين إلى الخلطة الخرسانية. حيث تم في هذه الدراسة استخدام نسب إضافة للبولي بروبالين ضمن الحدود المسموح بها في المواصفات (0.05 – 0.2%) من حجم الخرسانة وأكثر منها بنسبة إضافة (0.4%) لمقارنتها مع نتائج العينات المرجعية للخرسانة المصنعة بدون ألياف.
أثبتت النتائج النهائية لهذه الدراسة أن إضافة ألياف البولي بروبالين للخرسانة بنسبة (0.1%) من حجم الخرسانة (والتي تعادل 0.9 كجم/م3) يعمل على تقليل مساميتها ونسبة امتصاصها وكذلك نفاذيتها إلي أقل ما يمكن بالمقارنة مع بقية العينات، وإن زيادة استخدام هذه الألياف بنسب إضافة أعلى يجعل من الخرسانة أكثر مسامية وشراهة على امتصاص الماء وأكثر نفاذية. كذلك بينت نتائج مقارنة تأثير إضافة ألياف البولي بروبالين على عينات مصنعة من خرسانة ذات مقاومات ضغط مختلفة ازدياداً واضحاً في قيم المسامية ونسب الامتصاص والنفاذية للعينات ذات مقاومة الضغط الأعلى بالمقارنة مع نظيرتها من العينات ذات المقاومة الأقل. كما أظهرت النتائج أيضا عدم جودة استخدام ألياف البولي بروبالين في تحسين مقاومة الخرسانة للضغط وذلك عند إضافتها بأي نسبة، لذلك يجب أن يراعى هذا التأثير في الاعتبارات التصميمية للعناصر الانشائية المصنعة من هذا النوع من الخرسانة.

Construction development at this point of modern time has growing up quite strongly, one of many critical elements in construction world is the material that used for construction activities. Concrete is one of the example of used material in construction work, but as a material that has other many composition within it and many of them are exploited from the earth, then it is our work as human to use it at optimum level by know and understand the properties and other ability of concrete itself.

Ceramic waste is one of the most active research areas that encompass a number of
disciplines including civil engineering and construction materials. Ceramic waste powder is settled by sedimentation and then dumped away which results in environmental pollution, in addition to forming dust in summer and threatening both agriculture and public health. Therefore, utilization of the ceramic waste powder
in various industrial sectors especially the construction, agriculture, glass and paper
industries would help to protect the environment. It is most essential to develop eco-friendly concrete from ceramic waste. In this research study, the (OPC) cement has been replaced by ceramic waste powder accordingly in the range of 0%, 10%, 20%, 30% 40%, & 50% by weight of M-20 grade concrete. Concrete mixtures were produced, tested and compared in terms of compressive strength to the conventional concrete.
These tests were carried out to evaluate the mechanical properties for 7, 14 and 28 days. As a result, the compressive strength achieved up to 30% replacing cement with ceramic waste. This research work is concerned with the experimental investigation on strength of concrete and optimum percentage of the partial replacement by replacing cement via 0%, 10%, 20%, 30%, 40% and 50% of ceramic waste. Keeping all this view, the aim of the investigation is to study the behaviour of concrete while replacing the ceramic waste with different proportions in concrete.

The world is facing the problem of controlling air pollution from vehicle emissions, especially in growing urban areas. This study innovatively investigates applying the photocatalytic effect of titanium dioxide (TiO2) onto the concrete pavement to remove one of the major air pollutants, carbon monoxide. Photocatalytic compounds have the potential to remove harmful air pollutants from urban areas. There are three methods for applying TiO2-cement-based thin coating, water-based titanium dioxide solution, and a sprinkling of TiO2-to the fresh concrete surface before hardening. We have adopted a cement-based titanium dioxide solution method. The samples' environmental efficiency to remove carbon monoxide from the atmosphere was measured using a newly developed laboratory setup. This study involves using titanium dioxide as a photocatalyst in the concrete mix, which develops into a self-cleaning concrete, reducing the air pollution in the surrounding. This paper recommends the effective use of ceramic waste as a 10% replacement of fine aggregate. An experimental investigation was carried out on concrete containing Tio2 in the range of 12% and 28% by the weight of M25 grade of concrete. The concrete was produced, tested in compressive strength test and emission test, and conventional concrete.