Radhakrishna Krishna

• PhD
• Head of Faculty at R.V. College of Engineering

GeopolymerGeopolymer has been considered a popular alternative to traditional cement. Materials which are rich in silica and alumina can be used along with traditional aggregates to prepare geopolymer mortar and masonry unitsMasonry units. This chapter deals with the development of geopolymerGeopolymermasonry unitsMasonry units such as brickBrick (...

Conventionally natural sand is used as fine aggregate in manufacturing of concrete, whose availability is decreasing day by day. This study investigates the properties of concrete with alternative fine aggregate-processed slag sand. M55 grade concrete was designed with natural sand as fine aggregates. Natural sand was replaced by slag sand from 0 t...

In the recent past, there is growing interest to study the two modes of cementing of materials - i.e., conventional cement concrete and geopolymers in the same investigation to bring about their merits and demerits. As a complement to such studies, in this investigation, the analysis and assessment of strength development within the basic framework...

Natural sand obtained from river beds are normally used as fine aggregates in preparation of cement mortar. Due to increased demand and excessive extraction of river sand; there is an acute shortage in different parts of the world. Various research agencies are striving to investigate the properties of mortar with alternate fine aggergates such as...

Most of the supplementary cementitious materials are derived from waste from different industries with varying properties. It is necessary to know the performance of these materials in cement composites. In this investigation, the effect of water-to-binder ratio and grade of concrete on the properties of the concrete containing stone dust and micro...

Natural sand obtained from river bed is conventionally used as fine aggregates in preparation of cement mortar. Present study investigates flow and strength characteristics of cement mortar at various replacement levels of alternative fine aggregate, M- sand. Plastering mortars (1:3 and 1:4 ratio) were prepared with natural sand as fine aggregates...

The increasing demand for cement and its adverse impact on the environment are well known. Replacing cement partially with microfine wastes of construction and other industries is perceived to be a way forward in partially mitigating this situation. While binders like fly ash and ground granulated blast furnace slag are found to be good supplementa...

Cement masonry units are not considered as sustainable due to consumption of fuel, cement and natural resources. It is essential to find alternatives. This paper reports about making of Geopolymers solid and hollow blocks and masonry prisms and wallets using non conventional materials like fly ash, ground granulated blast furnace slag and manufactu...

Concretes produced from puzzolona cements and those in which supplementary cementitious materials are added during the production of concrete have shown better durability properties in comparison to concrete made from ordinary Portland cement. This is attributed to improved pore structure, and the effect of secondary hydration. With the availabilit...

Self compacting concrete (SCC) of M40 grade was designed. The binder in SCC consists of OPC and fly ash in the ratio of 65:35. River sand was replaced by manufactured sand (M-sand) at replacement levels of 20,40,60,80 and 100%. An attempt was made to evaluate the workability and strength characteristics of self compacting concrete with river sand a...

Cement masonry units are not considered as sustainable since their production involves consumption of fuel, cement and natural resources and therefore it is essential to find alternatives. This paper reports on making of geopolymer solid & hollow blocks and masonry prisms using non conventional materials like fly ash, ground granulated blast furnac...

Geopolymers belong to a category of non-conventional and non-Portland cement based cementitious binders which are produced using industrial by products like fly ash and ground granulated blast furnace slag (GGBFS). This paper reports on the development of geopolymer mortars for production of masonry units. The geopolymer mortars were prepared by mi...

Background/Objectives: To determine the basic properties of masonry units, masonry efficiency for the different h/t ratios of the masonry prisms and wallets. Methods/Statistical Analysis: The geopolymer bricks were cured at ambient temperature. These bricks were tested for compression, Initial Rate of Absorption [IRA], density, water absorption, di...

Concrete is a composite material made from cement, water, fine aggregate and coarse aggregate Increase of cement production and disposal of waste materials into the environment results in adverse impact on the environment. Present study is focused on finding partial replacement for cement by waste materials or waste products that are harmful to the...

Concrete is a composite material made from cement, water, fine aggregate and coarse aggregate Increase of cement production and disposal of waste materials into the environment results in adverse impact on the environment. Present study is focused on finding partial replacement for cement by waste materials or waste products that are harmful to the...

This chapter illustrates the reaction mechanism, the choice of materials used in making geopolymers and proportioning in brief. Later, the methods to be adopted to prepare mortar samples, determination of the optimum dry density, casting of mortar specimens and testing the same are illustrated. The development of compressive strength with various p...

As the production of cement increases, its adverse impact on the environment also increases. With cement being the second most consumed substance after water, the need to reduce its production is the need ofthe hour. Replacement of cement by supplementary cementitious materials results in less usage of cement. In this study, cement is partially rep...

Geopolymer concrete is an alternate material to the conventional concrete. The research on heat cured geopolymers is well documented by multiple researchers. However, there is very little information available on ambient cured geopolymer concrete. This paper illustrates the mechanical properties of ambient cured geopolymer concrete synthesized by a...

Natural sand is commonly used as fine aggregate in concrete. Due to extensive construction activity natural sand is becoming expensive and scarce. The purpose of this study is to investigate the possibility of using alternative fine aggregates such as M-Sand, Pond ash and Slag sand with different replacement levels. Concrete of M25 grade was prepar...

The effect of addition of mono fibers and hybrid fibers on the mechanical properties of concrete mixture is studied in the present investigation. Steel fibers of 1% and polypropylene fibers 0.036% were added individually to the concrete mixture as mono fibers and then they were added together to form a hybrid fiber reinforced concrete. Mechanical p...

It is well known that the production of cement is extremely resource and energy intensive process producing an equal amount of CO 2 per ton of cement. Hence, due to growing environmental concerns of the cement industry, there is a need to develop alternative materials such as fly ash, Ground granulated blast furnace slag (GGBS). Also there is a nee...

Pavements are subjected to severe condition of stresses and weathering effects from the day they are constructed and opened to traffic mainly due to its fatigue behavior and environmental effects. Therefore, pavement rehabilitation is one of the most important components of entire road systems. This paper highlights the design of concrete pavement...

Crack is commonly observed failure in the case of concrete. Crack may develop due to addition of excess of water to during mixing of concrete, or may be due to shrinkage and creep. In the present study, crack healing and improvement of physical properties of cement paste, mortar and concrete are studied. It is done by the addition of bacterial stra...

The progressive collapse of reinforced concrete structures is initiated when one or more vertical load carrying members are removed due to man-made or natural hazards. The building's weight transfers to neighboring columns in the structure, leads to the failure of adjoining members and finally to the failure of partial or whole structure system. In...

Fly ash, Lime and gypsum are industrial wastes generated in millions of tones every year. Utilization of these materials is effective way of disposing the pollutants. In this research fly ash, lime, and gypsum were used in definite proportion along with quarry dust to produce FaL-G blocks. These blocks were tested for compressive strength, water ab...

Geopolymer mortar compressed blocks were prepared using fly ash, ground granulated blast furnace slag, silica fume and metakaolin as binders and sand/quarry dust/pond ash as fine aggregate. Alkaline solution was used to activate the source materials for synthesizing the geopolymer mortar. Fresh mortar was used to obtain the compressed blocks. The s...

Cement in concrete mix, proportioned according to American Concrete Institute (ACI) method, was replaced with various percentages of fly ash by weight. Fly ash concrete cubes were prepared using a water content of 140 kg/m3 and a total cementitious material of 280 kg/m3. The concrete cubes were tested for compression at different ages. The compress...

The rapid increase in the capacity of thermal power generation in India has resulted in the production of a huge quantity of fly ash. The prevailing disposal methods are not free from environmental pollution and ecological imbalance. Large stretches of scarce land, which can be used for shelter, agriculture or some other productive purposes, are be...

Cardiovascular diseases, the main cause of death in the society imply a strong correlation between enhanced blood cholesterol levels. 3-Hydroxy-3- methylglutaryl–coenzyme A (HMG–CoA) reductase catalyzes the conversion of HMG–CoA to mevalonic acid, plays a significant role in cholesterol synthesis. Fungi are the important sources for the production...

Aspergillus niger PN2 an endophytic fungus, was isolated from the healthy tissues of Taxus baccata. The fungus was screened for the production of lovastatin on a solid state fermentation with wheat bran as a substrate. The fungal species were identified by their characteristic cultural morphology and molecular analysis. The presence of lovastatin w...

Compressive strength development of Portland cement concrete and geopolymer composites is studied together. In case of Portland cement concrete the bonding that takes place is by chemical reactions resulting due to combination of ionic, covalent and van der Waals forces. On the other hand, in fly ash based geopolymer composites bonding is initiated...

In the present investigation, strength development in ambient cured geo-polymer mortar using marginal materials / industrial by-products for sustainable development is studied. The materials considered are Fly Ash, Ground Granulated Blast Furnace Slag (GGBFS), Silica Fume (SF) and Quarry Dust. Geo-polymer mortar is prepared without using any conven...

In the present investigation, strength development in ambient cured geo-polymer mortar using marginal materials / industrial by-products for sustainable development is studied. The materials considered are Fly Ash, Ground Granulated Blast Furnace Slag (GGBFS), Silica Fume (SF) and Quarry Dust. Geo-polymer mortar is prepared without using any conven...

Strength is not the only property for which cement based composites are processed. There are many practical situations where enhanced workability is required for placement with the requirements of strength being far lower than normal for which cement mortars and concretes are processed. These are Controlled Low Strength Materials (CLSM) with requir...

ement concrete was prepared using cement and fly ash as binder, sand as fine aggregate and pumice as coarse aggregate. American Concrete Institute (ACI) method was used to proportion the concrete. The concrete and constituent mortar cubes were cast and cured in water. The cubes were tested at different ages to find the compressive strength. The fra...

FaL-G, a composite prepared using Fly ash (Fa), Lime (L) and Gypsum (G) in a definite proportion, was used as a binder. FaL-G compressed mortar blocks were prepared considering various parameters like fineness of fly ash, aggregate-to-binder ratio, degree of saturation, age, and water-to-FaL-G ratio. FaL-G concrete cubes were prepared using differe...

Fly ash based geopolymer composite cubes were cast using class F fly ash, ground granulated blast furnace slag (GGBFS) as binders. The fluid-to-binder ratio was varied keeping all other parameters constant. The geopolymer composites were cured in different conditions. The composites were tested for compression at different ages. It is interesting t...

useful for the chemical reaction. As the moisture escapes from the mix, air voids are created, resulting in a reduction of strength. It is a well-known fact that each percentage of air voids reduces about five percent of the strength in saturated Portland cement composites. A similar trend can be observed in geopolymer mixes. If the strength is plo...

This paper addresses the technology of making compressed geopolymer mortar blocks with class F fly ash. The experimental data generated is analyzed and a phenomenological model is advanced to arrive at the combinations of the ingredients to produce geopolymer meeting the compressive strength required at the specified age irrespective of the molarit...