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March 1992 - present
Publications
Publications (106)
Amidst the prevailing subjective pricing paradigms for high-rise apartments in India, this paper advocates for a paradigm shift toward thermal comfort–based differential pricing, recognizing its pivotal role in influencing residents’ well-being in hot and humid climates and energy savings. Understanding the correlation between thermal comfort, floo...
The present invention relates to the lightweight cellular foam concrete prepared by mixing pre-formed foam, obtained by mechanical foaming of aqueous solution of salt of unsaturated anacardic acid(s) and admixture for foam stabilization, and base mix, obtained from Portland cement or geopolymer binder, aggregate, and water.
Incorporating daylight inside occupied spaces has several benefits, including reduced lighting load, improved mental and physical health of occupants, and increased productivity during working hours. Several Innovative daylighting systems that utilize advanced technologies and design approaches are devised and tested to bring natural light into occ...
There is an increasing demand for fine aggregate for use in concrete and mortar. In this study, sand extracted from mine overburden from two locations through the wet-sieving process was used as alternative fine aggregate in mortar. The behavior has been benchmarked with mortar using conventional river sand and coarse and fine sand obtained from cr...
To enhance the foaming characteristics of a synthetic surfactant-based foaming agent using a range of admixtures and,
To study the performance of engineered foaming agent in fly ash and slag-based geopolymer mortar while assessing the foamed matrix stability
Prediction relations for estimating compressive strength of cellular concrete differ from those of normal concrete because of the entrapment of air. The objective of this paper is to propose prediction relations for the compressive strength of both non-autoclaved and autoclaved aerated concrete by extending two of the well-known relations available...
The lighting load can be reduced either by improving the efficiency of artificial lighting or by supplementing daylight to the building interiors with Innovative Daylighting Systems (IDS). Fibre optic daylighting system is an up-and-coming IDS that utilises direct and diffused sunlight to illuminate deep-plan buildings without location and orientat...
This paper reports the influence of the addition of slag in a fly ash-based alkali-activated aerated system, using both Class-F and Class-C fly ash. The factors considered in this study are dosage of aluminium powder as an aerating agent, dosage of slag as co-binder, the molarity of NaOH as an alkaline activator and curing temperature. The incorpor...
Foam characteristics, including density, stability, and texture, influence the properties of end products like foamed concrete. The present work investigates the individual and combined influence of xanthan gum and low-cost sodium-based admixtures (NaOH, NaCl, and Na2CO3) on the viscosity of sodium lauryl sulfate (SLS) foaming solution and the foam...
The potential use of large volume fly ash and its suitability in improving the properties of autoclave aerated concrete (AAC) is considered important in the construction industry. This study was carried out to design an AAC mix with high volume fly ash and with low cement content to enhance the properties of AAC, which has application for use as ma...
The study exposes a range of strength to density combinations of AAC for application as masonry units. The final product is a low cement Autoclaved Aerated Concrete (AAC) masonry unit using binary, quaternary and ternary mixes with fly ash, lime, and gypsum.
Global and acoustic–phonetic correlates of speech intelligibility are important measures of talker intelligibility. Speech characteristics have been evaluated using speech samples that involve reading pre-administered passages under controlled environments. In classrooms, lecturing is the mode of speech delivery. The presence of noise from ceiling...
Paper published in The Masonry Society Journal December 2000 pages 23-34.
Teachers are better speakers when compared to students with oracy built into
their professional experience over a period of time. Students’ perception and
judgement of teachers’ speech intelligibility has been reported abundantly in
literature. However, teachers’ perception of students’ speech intelligibility has
been rarely studied in the context...
In the interest of utilizing high-plasticity excavation soil as a replacement for fine aggregate in cement mortar, a study on the thermal treatment of soils containing 25% and 40% clay fractions was carried out. A range of tests including thermogravimetric analysis (TGA) and X-ray diffraction (XRD) were conducted to examine the transformation of fi...
Use of ductless split air conditioners in small workspaces leads to accumulation of carbon dioxide due to the absence of fresh air entry. Additional mechanical ventilation is required to meet the ASHRAE standard. Providing constant rate ventilation would reduce the CO2 concentration but would lead to high energy consumption when there is variation...
Prolonged exposure to a higher concentration of carbon dioxide (CO2) affects human health, performance and cause Sick Building Syndrome (SBS). Accumulation of CO2 concentration beyond ASHRAE recommendation of 1000 ppm has been reported in ductless split air-conditioned workspaces due to the absence of fresh air vent and higher occupant density. Spl...
Lower ventilation rates and higher occupant density lead to accumulation of carbon dioxide (CO2) accompanied by human bioeffluents inside built environments. Research had been conducted to evaluate the effect of CO2 and bioeffluents using physiological measurements and correlated with reduced cognitive performance. However, no study has reported th...
The aim of this work is to broadly investigate the possibility of utilizing excavated soil as alternative for river sand in cementitious system. Three different types of soils with low, medium and high plasticity (with different proportion and type of clay) were used as fine aggregates to produce cement mortar. The same soil samples were treated by...
In this paper, the factors influencing the properties of aerated geopolymer concrete using low calcium fly ash through sodium-based alkali activation at a range of curing temperature is discussed. The parameters and their influence are statistically studied using design of experiments. The initial rate of reaction in the aeration process is control...
The possibility of reusing excavated soil as an alternative to river sand in the production of mortar was studied. The soil samples before and after wet sieving were used as fine aggregate in mortar preparation. The resulting wash water in wet sieving was analysed for the presence of soluble ions and its effect in cement hydration and mortar proper...
To explore the significance of geopolymer technology on producing environmental friendly waste based mortar which could be a sustainable replacement for conventional mortar; Low, medium and high plastic soil from different locations was used as fine aggregate to produce fly ash based geopolymer mortars. The experiments were designed using central c...
With a view to replace synthetic foaming agents in the production of foam concrete, renewable and naturally available soapnut (SN) fruit has been studied as a foaming agent. Soapnut foaming solutions are prepared in two ways, viz., water soaking for 24 h without heating and with heating of soapnut pericap over a range of temperature (i.e.70 °C–90 °...
The objective of the work is to examine the performance of tetraethyl orthosilicate (TEOS) modified microcrystalline cellulose (MCC) fiber, derived from cotton, as a mineral admixture that could be compatible in cement mortar composites. The effectiveness of surface modification of MCC is characterized by powder X-ray diffraction, FTIR, TGA and SEM...
The influence of fineness of aluminium powder through an evaluation of variation in the workability of the mix, rate of aeration and fresh density with time, dry density, compressive strength and water absorption of aerated cement paste and mortar were studied. Flow table test clearly distinguishes variation in initial workability of the mixes for...
This paper describes design of daylight collectors using multiple Fresnel lenses, each facing the sun for a particular period of time in a day. The influence of solar movement on flat Fresnel lens was studied. The influence of groove density of the lens was also determined by which the suitable Fresnel lens was selected. Passive and profiled north-...
This paper discusses the performance evaluation of anidolic concentrators in an overcast sky condition. The concentrators were designed, with acceptance angles of 60°, 70° and 80°, first by maintaining the profile of the concentrator’s uniform and secondly by keeping the height uniform. Studies were done using these concentrators with a model light...
This study identifies admixtures to enhance the effectiveness of Sodium Lauryl Sulphate (SLS) as a foaming agent by increasing the foam density and stability. Sodium hydroxide, sodium carbonate and sodium chloride were chosen based on common ion effect to increase the viscosity of the foaming solution in order to achieve ASTM recommended range of f...
Performance of conventional vertical light pipes with acrylic domes is highly dependent on the solar altitude since for lower solar elevation the acceptance angle is limited due to the small inlet aperture. A profiled Fresnel collector with a multi-lens system is useful in enhancing light in a light pipe at low solar altitudes but suffers losses du...
Statistically designed experiments using Response Surface Methodology have been undertaken to identify the parameters influencing manufacturing process and properties of aggregate using coal pond ash (generated from bituminous and lignite coal sources). Based on the preliminary studies, Ca(OH)(2) and borax have been identified as pelletization and...
This paper explores the feasibility and the process of converting of pond ashes - a waste material into artificial aggregates - a value added product. As a first step, identification of the parameters influencing manufacture and properties of artificial aggregate withpondash has beencarried out. Pond ash of both bituminous and lignite type have bee...
This paper discusses the factors influencing the pelletization and properties of lightweight aggregate
using bottom ash through alkali activation and curing at ambient temperature. The experiments were
designed using central composite design of Response surface methodology. The alkaline activators used
for the synthesis of geopolymer aggregate are...
In a dense urban environment, sky obstruction caused by high rise buildings causes minimal daylighting for interiors on lower floors and in deep interior spaces. Innovative daylighting systems can be used to enhance daylighting indoors using available sunlight. This paper presents an overview of recent developments of innovative daylighting systems...
This paper combines two technologies, viz, interlocking blocks and foam concrete to study and develop solid foam concrete interlocking block masonry. Various aspects of the manufacture of foam concrete interlocking blocks are discussed. The density of foam concrete blocks ranges between +/-50 and 1250kg/m3. Class-C fly ash was used as set-accelerat...
Foam concrete is suitable for producing lightweight blocks. This paper deals with identification of suitable set accelerator for foam concrete made using sodium lauryl sulphate as foaming agent, i.e. facilitating demoulding within 2 h and also economical. As conventional accelerators, viz., calcium chloride, calcium nitrate, triethanol amine were n...
This paper reports the effects of variation in density, concentration and type of cation associated with sulphate on the expansion, mass and strength loss of foam concrete produced with two synthetic surfactants. Comparisons are made between behaviour of foam concrete of different densities and that of corresponding base mixes of mortar without foa...
A comprehensive research has been conducted to explore the influence of sintering on the properties of fly ash aggregate containing clay binders (bentonite and kaolinite). Fly ash aggregate containing clay binders, have been subjected to various sintering temperatures at different durations of 700–1400 °C and 15–120 min, respectively. The variation...
Considerable attention has been paid in evaluating the causes of delamination in two major prestressed concrete
containment domes in USA and a recent incident in India. Conventionally, prestressed concrete domes are analyzed by idealizing them using surface elements, which do not have provisions for evaluating the normal force across the thickness...
This paper focuses on the properties of sintered aggregates with low calcium bottom ash from coal fired thermal power plants using a wide range of clay binders through pelletization process. The experimental runs were designed using central composite design of response surface methodology. The aggregate was produced using a disc pelletizer. The pel...
Autogenous curing behavior of cold-bonded fly-ash-aggregate concrete for a range of cement and aggregate contents is studied by subjecting concrete to three different curing regimes, viz, mist curing, sealed condition and air curing. The moisture movement from the aggregate to concrete at various ages is estimated and correlated to the paste-aggreg...
Selection of the surfactant has an impact on many of the foam properties as it affects the surface tension and gas–liquid
interfacial properties. The objective is to produce stable aqueous foam of required density. These two characteristics are
influenced by the type of surfactant, its concentration and foam generation pressure. This study compares...
Cold bonding facilitates production of aggregate with minimum energy consumption compared to the sintered aggregate, which requires a heat treatment in the range of 1000–1200 °C. The strengthening of pelletized bottom ash in cold bonding at ambient temperature is due to the formation of CSH gel during the hydration from the chemical reaction betwee...
Coal combustion residues which include fly ash, bottom ash and boiler slag is one of the major pollutants as these residues require large land area for their disposal. Among these residues, utilization of bottom ash in the construction industry is very low. This paper explains the use of bottom ash through pelletization. Raw bottom ash could not be...
The performance evaluation of a sodium lauryl sulfate to qualify as a foaming agent is presented in this paper. When new surfactants are used a systematic study of production parameters on the foam characteristics needs to be undertaken unlike proprietary foaming agents and foam generator for which manufacturer has predefined the parameters. The re...
The properties of sintered fly ash aggregate concrete are discussed. India produces approximately 100 million tones of fly ash annually. Lightweight concrete reduces dead load of a structure and consequently results in smaller foundations. It also facilitates segmental construction of larger components. Pelletization is a well-known technique in me...
In the absence of coarse aggregate, the relative influence of factors affecting the shrinkage of foam concrete are likely to be different as compared to normal concrete. This paper presents the shrinkage behavior of preformed foam concrete for the influences of basic parameters, viz, density, moisture content, composition like filler-cement ratio,...
Earlier studies have established that aggregates could be produced from fly ash through pelletization, which has the advantages of reducing (1) environmental pollution and (2) consumption of depleting natural aggregates. Though cement, lime, and bentonite were used for improving the properties of fly ash aggregates, limited studies have been report...
Though foam concrete was initially envisaged as a void filling and insulation material, there have been renewed interest in its structural characteristics in view of its lighter weight, savings in material and potential for large scale utilization of wastes like fly ash. The focus of this paper is to classify literature on foam concrete in terms of...
Cold-bonded fly ash aggregate concrete with fly ash as part of binder or fine aggregate facilitates high volume utilization of fly ash in concrete with minimum energy consumption. This paper investigates the influence of fly ash on strength and sorption behaviour of cold-bonded fly ash aggregate concrete due to partial replacement of cement and als...
This paper discusses the development of empirical models for workability and compressive strength of cold-bonded fly ash aggregate
concrete in terms of mixture proportioning variables such as cement content, water content and volume fraction of cold-bonded
aggregate through statistically designed experiments based on Response Surface Methodology. F...
This paper discusses first the properties of recycled aggregates derived from parent concrete (PC) of three strengths, each of them made with three maximum sizes of aggregates. The relative physical and mechanical properties of fresh granite aggregate are discussed. Using these nine recycled aggregates, three strengths of recycled aggregate concret...
Cold bonding facilitates production of lightweight aggregate from flyash with minimum energy consumption. This paper investigates the effect of cold-bonded aggregate on the properties of fresh and hardened concrete mixtures with cement content ranging from 250 to 450 kg/m 3 and varying water-cement ratio for threevolume fractions of cold-bonded agg...
This paper discusses the influence of normal water curing, autoclaving and steam curing on the properties of a typical class-C fly ash aggregate. The 10% fines value, water absorption, and porosity of aggregates are correlated with SEM and XRD results to understand the influence of various factors and material characteristics. An increase in durati...
There are several strength prediction relations developed for plain cement paste, mortar and concrete. In concrete where air
voids contribute significantly to volume of voids (like aerated and foam concrete), more general expressions including the
volume of air voids is to be developed as the better alternative. The objective of this paper is to pr...
This paper deals with the study of the influence of a mixture composition on the properties of foam concrete at the fresh state. The stability of the base mix in terms of the water-solids ratio for getting a stable foam concrete mix of design density was determined for different mixture parameters and their influence on the water-solids ratio requi...
Knowledge of sorption characteristics like absorption and sorptivity of building materials are of importance as they affect the durability and other properties. In the case of lightweight concrete like aerated and foam concrete, the moisture movement behaviour becomes more complex as such concretes contain much larger volume of air voids. This pape...
Layout planning of multistory buildings requires multidisciplinary participation in the decision-making process, which is governed by intuition, creativity, and experience of the designers, and available information. Optimization techniques are rarely applied to the layout planning stage. The present study aims at a hybrid approach by combining kno...
One of the main issues associated with fly ash is the variation in the fineness of fly ash produced within a plant and between thermal power plants, due to the variation in the quality of coal used and the production technique adopted in which pelletization of fly ash becomes complex. In this paper, the influence of fineness of fly ash is studied b...
The pore structure of cementitious material, predetermined by its porosity, permeability and pore size distribution, is a very important characteristic as it influence the properties of the material such as strength and durability. The pore parameter could therefore be a primary factor influencing the material properties of foam concrete and an in...
There have been several investigations in the past on the influence of mixture composition on the properties of foam concrete. Conventionally strength is related to density alone and few models have been developed relating strength with density, porosity, gel–space ratio, etc. Very little work has been reported in the literature in predicting the p...
Most of the investigations on foam concrete in the past have been confined to neat cement paste, cement paste with partial replacement with admixtures and to cement–sand mixes. This paper reports the results of a systematic study to ascertain the influence of filler type (i.e., sand and fly ash) and the particle size of sand on the properties of mo...
A pelletization process is used to manufacture artificial lightweight coarse aggregate using fly ash. Pelletization depends on the size of particles and their distribution, the wettability of particles and moisture content, along with the process related parameters. A review indicates that only limited studies have been reported on the pelletizatio...
Sustained research and development work on the utilization of fly ash for various productive uses have been carried out in the past. In the construction industry, major attention has been devoted to the use of fly ash in concrete as a cement replacement. The production of artificial lightweight coarse aggregate using fly ash has potential for its l...
This study is focused on the use of fly ash in mortar as an addition to and a replacement of an equivalent volume of cement. For each mix, the water content required for achieving a flow value of 135%, was first determined. The water requirement for each mix increases as the addition and replacement level of fly ash increases. Based on this water c...
Traditional masonry construction can be labor intensive and slow due to use of small-sized bricks, which also requires the use of numerous mortar joints. Desire to increase the speed of masonry construction prompted investigations that led to the development of surface-bonded and mortarless masonry using conventional and interlocking blocks. Among...
Delamination failure is encountered in prestressed concrete (PSC) shells. This type of failure occurs in the shell during prestressing, due to occurrence of cracking inside the shell parallel to its surface. One of the major factors is generation of radial tensile stress in the outer region of the shell thickness, having minimum intensity at the le...
Pelletization is a promising process for making artificial aggregates from fine-grained materials like fly ash, which facilitates its high volume utilization as lightweight aggregate in concrete. A review indicates that only limited studies are reported on pelletization of fly ash aggregates. A study on the process of pelletization for the influenc...
The limitations of conventional masonry cited quite often with respect to constructional, structural and functional performances are summarized, along with attempts to overcome these limitations through different methods of accelerating masonry construction (increasing size of masonry units, elimination of bedding mortar through adoption of: (i) co...
This paper discusses water penetration resistance studies on conventional brick/block masonry for variations in construction types and materials adopting ASTM E 514-90 procedure. The behaviour of interlocking block masonry for the influence of type of bedding (dry-stacking, thin-jointing, and mortar-bedding), surface finishes (stucco/plaster finish...
Masonry construction over the last century has undergone radical changes that have led to specific improvements in construction performance due to the advent of large-sized blocks, innovative methods like surface-bonded masonry, partially grouted masonry, and dry-stacked/mortarless masonry using interlocking blocks. This paper outlines relative pro...
This paper discusses the relative permeation characteristics (volume of voids and water absorption (ASTM C642-97) and sorption) of three strengths of concrete with (i) three maximum sizes of fresh granite aggregates (parent concrete), (ii) recycled concrete aggregates derived from each of three strengths of parent concrete, and (iii) two types of c...
Singly curved or doubly curved shells, most commonly used in large span structures, are analyzed using flat plate/shell/plate-shell. Depending on their structural actions and stresses generated, sometimes they are also prestressed. If the prestressing is in a direction where the curvature of the shell is negligible or zero, the shell structure coul...
This technical note discusses water penetration resistance studies on a solid interlocking block masonry system, adopting ASTM E 514-90 for the influence of the type of bedding (dry stacking, thin jointing, and mortar), surface finishes (stucco and plaster on one side or both sides), and simulated wind velocities (0, 50, and 100 km/h). Silblock mas...
Development of non-conventional methods of masonry construction techniques adopting interlocking blocks is a potential alternative to the labour intensive conventional mortar bedded masonry. A review of available interlocking block systems, which brought out their shortcomings, formed the basis for developing a simple interlocking concrete block ma...
The quantity of masonry demolition waste is higher than that of concrete waste. A review shows that extensive studies have been made of recycled concrete aggregates with only limited studies on recycled brick aggregate. The objective of this paper is to investigate the use of two types of low-strength bricks as lightweight coarse aggregate in concr...
Aerated concrete is relatively homogeneous when compared to normal concrete, as it does not contain coarse aggregate phase, yet shows vast variation in its properties. The properties of aerated concrete depend on its microstructure (void–paste system) and composition, which are influenced by the type of binder used, methods of pore-formation and cu...
Accelerated mortarless masonry constructions have been developed or are being used in different countries with limited research studies. This paper discusses first the salient features of interlocking-block masonry and then the development of simple interlocking-concrete-block masonry systems, keeping in view the requirements of shape simplicity an...
Aerated concrete is characterized by the presence of large voids deliberately included in its matrix to reduce the density. This study reports the investigations conducted on the structure of cement-based autoclaved aerated concrete (AAC) and non-AAC with sand or fly ash as the filler. The reasons for changes in compressive strength and drying shri...
Aerated concrete is a relatively homogeneous material as compared with conventional concrete since it is devoid of the coarse aggregate phase, yet it exhibits vast variation in its properties. Most of the investigations in the past have been confined to autoclaved products. This paper reports the results of a systematic study conducted to ascertain...
The process of drying of many materials is accompanied by dimensional changes, which induce cracks in the structure. This phenomenon is particularly significant in aerated concrete owing to its high total porosity and specific surface of pores. The factors influencing drying shrinkage of aerated concrete are widely different from that of normal con...
The compressive strength and density of aerated concrete are largely influenced by the composition and method of airing. Conventionally, strength is related to density alone, with little attention paid to the composition. This paper discusses the development of prediction relations for compressive strength and density of aerated concrete through st...
This paper discusses the results of a systematic experimental investigation on 306 stretcher bonded concrete hollow block masonry prisms under axial compression for the influences of block-mortar strength combinations, block geometry, height to thickness ratio (h/t) of block, mortar bedding, and thickness of mortar joint. The test results are then...
Cost reduction in roofs/floors has been achieved through the adoption of alternate techniques like filler slab, which works on the principle of filling a part of concrete in the tension zone with cheaper substitutes. Even though there are sound theoretical bases and proven methods of construction, there has been no systematic analysis of cost-effec...
Alternatives to conventional reinforced concrete (RC) slab like voided or filler slabs are based on the principle that a part of the concrete in the tension zone is either eliminated or filled with a relatively cheaper material, resulting in reduction in cost and/ or reduction in self-weight and better thermal insulation. This paper discusses detai...
Traditional masonry construction is labor intensive and slower. The inclusion of mortar joints affects the speed of construction, structural and functional performance. Hence attempts have been made to accelerate the masonry construction process. This paper first establishes the need for accelerating masonry construction process and also identifies...
Recycled aggregate concrete can utilise demolition material from concrete and masonry constructions. Though several studies have been made on the reuse of concrete waste, only limited studies have been made with respect to use of demolished brick masonry as aggregate. An attempt has been made in this paper to assess the physical and mechanical prop...