Product development

Ensuring strength and durability through slump retention

Published

3 years ago

October 14, 2021

admin

Manufacturers have been adopting various technologies to ensure slump retention in concrete. One of the effective methods is the use of admixtures. The admixture technology continues to grow as new challenges arise. Charles S Jones elaborates on one such aspect on managing longer workability in concrete without it affecting properties such as strength and durability.

Due to rising traffic and changing weather conditions, concrete producers not only find it very difficult to maintain the consistency of concrete but also to deliver concrete that can satisfy the performance requirement under stipulated costs. The average lead time for a commercial ready-mixed concrete to be delivered to any site is anywhere between 150 – 210 minutes. One of the solutions to counter the effect of delay is to use concrete admixtures.

The growth on the use of admixtures in concrete can be largely attributed to the understanding of factors that affect the durability of the concrete. Over the years, the change of admixture technology from lignosulphonates to napthalene sulphonates to poly carboxylates stands testimony to this transformation. Also, the insight gained on the contribution of supplementary cementing materials such as flyash, slag, silica fume, etc, have increased the use of admixtures in concrete today. Modernisation and mechanisation have also added new dimensions to the growth of this industry and to the launch of various new technologies thereto. The shortage of skilled labour has made self-compacting and smart dynamic concrete the preferred choice for most builders.

The movement of rural population to urban areas has taken its toll not only on the infrastructure but also in its management and maintenance. The traffic condition in metros in general, despite the number of flyovers being constructed, has become increasingly difficult to maneuver through. This has given rise to a unique concern for the concrete fraternity when it comes to maintaining the consistency of the concrete. The environment mandate exercised by the government bodies also adds to this problem.

A decade ago, typical lead times (slump retention time) to ship the concrete from one point to the other was about 2 hours for a city like Mumbai. This has changed dramatically and today it is impossible to have a lead time of less than 3 hours. It is a big challenge for producers to provide concrete that is not only pumpable at 3.5 hours but is also able to set within 24 hours, so that de-stripping of form-work is possible. The split dosing of admixtures have been heavily discouraged by consultants and clients, owing to the fear concrete not setting properly. This has pushed producers to over-design the concrete with extra cement content so that the mix can accommodate extra water in case of a slump drop during transit. The addition of water into the mix is a very sensitive issue and requires a good degree of understanding of the consistency of concrete. In the absence of a qualified engineer, it can lead to a severe strength drop and durability concerns. Neither the purchaser nor the concrete producer can guarantee the quality of the concrete with this system. This has led to consultants resorting to specify the grade of concrete marking it higher than required, which in turn, has led to an unnecessary increase in costs without any guarantee of the quality.

This unfortunate situation arises c only because concrete is specified for its performance requirement at the site rather than the performance and quality right from batching to pouring point. If care is taken to specify the quality and performance of the concrete in terms of initial slump and final slump, rheology, etc, then such concerns can be easily addressed.

Super retention technology -Suretec

Traditional super-plasticizers (napthalene-based) are the cheapest admixtures available but are not capable of addressing the issues in M20 – M40 grades, where long workability is required without affecting the strength. The Poly Carboxylic Ethers (PCE) based admixtures called hyper-plasticisers have paved the way for newer concrete technology and the demand for such admixtures has been ever increasing. PCEs in general, impart better control over the rheology of the concrete and that’s one of the reason such admixtures are always used for producing self-compacting, smart dynamic concrete. With the advent of the Super-Retention Technology by SureTEC, second generation PCE based admixtures by BASF, this issue of long workability and early strength gain have now been addressed.

Table 1: Details of cement

Particulars Cement	Test results
Physical Parameters
Fineness (m2/Kg)	310
Normal consistency	27.75
Setting time (minutes)
Initial	175
Final	240
Soundness
Le-chat expansion (mm)	0.70
Autoclave expansion (%)	0.065
Compressive strength
3 days	39.3
7 days	50.0

SureTEC provides improved short and long- term performance of concrete by controlling the two distinct features essential for high quality concrete, extended workability and high early strength. The SureTEC concept ensures that the concrete is of high quality as originally specified; the consistency of the concrete remains the same from the batching plant, to the delivery and placing, followed by its hardening process. Generally, in situations where longer retention is required, the concrete is designed at a higher slump and reaches the minimum slump requirement after the stipulated retention period. With SureTEC, it is now possible to make a concrete with fairly lower slump, where the slump fall is gradual so that the concrete placed is relatively better in its rheology. The demand for extreme performances of admixture has led to excellence in engineered polymers, which provide new understanding of chemical-cement interaction. It is an extension of the competencies from organic to inorganic chemistry of cement and concrete. This facilitates stronger water reduction for improved workability, faster hydration for rapid strength, longer workability retention time and better rheology control for easy form filling.

PCE admixtures have been widely used in the recent past, especially in self-compacting concretes. They are characterised by short principal chairs (the backbone) with long side chairs. Considering the many properties of such a polymer, such as the molecular weight of the whole polymer, backbone or side chairs, ionic strength, chemical composition, production parameter, an extra ordinary variety of special performing polymers is feasible. Figuratively, admixtures could be perceived to be consisting of building blocks, (Fig. 1) of differing configuration of molecular structure. ‘A’ block controls slump retention, ‘B’ early strength, ‘C’ final strength and ‘D’ water reduction. Either the building blocks are combined or formulated. Functionally ‘A’ controls the absorption speed of the PCE to the cement surface while it is not retarding. Block ‘B’ enhances the natural hydration process without influencing the hydration products. Contrarily, ‘C’ enhances strength by influencing the hydration and lastly, ‘D’ is a conventional water reducing component of PCE. Using the modular approach, a seemingly vast number of combinations are possible. An understanding of the individual polymers help in formulating a product that can literally have no drop in slump throughout the transportation and once the setting starts, hydrates much faster to achieve early age strengths.

Experiment using Suretec

M-25 grade of concrete mix was designed for typical Mumbai aggregates and details of cement used for trials conducted are given in Table 1 and 2. The control used BNS type admixture while the PCE admixture (SureTEC) PCE-1 was used for comparison. Various dosages of PCE-1 were tried out with a target of 150mm slump at four hours, and the same was evaluated for strength values.

Table 2: Mix designed with aggregates for construction Mumbai

Mix Grade	M25	M25
OPC 53 Grade	285	285
Fly Ash	95	95
Total Binder	380	380
CA I – 20mm	550	550
CA II – 10mm	500	500
Crusher Dust	900	900
Free water	171	171

W/C Ratio	0.45	0.45

Admixture:	1.2%	0.9%
	BNS based admix	SureTEC (PCE – 1)
Slump/ Flow (mm):
05 mins	230	175
30 mins	200	180
60 mins	180	170
120 mins	150	160
180 mins	120	140
240 mins	20	120

Setting Time
Initial Set	10 hours	9 Hours
Final Set	18 hours	15 Hours
Compresive Strength(MPa)
01 days	8.2	12.1
03 days	15.8	19.3
07 Days	25.5	27.5
28 Days	32.6	35.2

Remark	Bleeding and segregation seen for initial 30 minutes	No bleeding or segregation

Observations

While the initial slump was 230 mm (collapse) for the BNS admixture, it was only 175 mm for the PCE-1 which had the SureTEC component in it. The control mix with BNS had bleeding upto 30 minutes but yielded a slump of 200 mm slump; the SureTEC admixture continued to have almost the original slump. The SureTEC PCE continued to remain at almost the same slump even up to 120 minutes, with a slight drop of about 10 mm. The traditional BNS mixture, however, had reduced to 150 mm by the end of two hours which is a fall in slump by 80 mm. Moreover, the slight increase in slump seen at 30 minutes is due to the phenomenon that one of the components of the formulation was acting in a delayed manner. The BNS admixture-based mix was able to withstand a pumpable slump only upto 180 minutes and went on to about 20 mm with the mix becoming very stiff. On the other hand, the SureTEC PCE had good pumpable consistency even after four hours. The setting characteristics of both the mixes were studied to understand the effect these admixtures had on the setting. While the BNS admixture had ten and 18 hours as the initial and final setting time, the SureTEC admixture showed improved performance of nine and 15 hours respectively. The retarding effect of BNS formulations were very evident from these results, whereas the SureTEC formulations were unaffected by the admixture chemistry. It is also evident from the strength results that the early strength (24 hours) with SureTEC formulations are much higher compared to that of the BNS admixtures, whereas in the later age strengths, there was not much of a difference. This means that the SureTEC admixtures allows the cement to hydrate at a faster rate compared to the traditional BNS based admixtures.

Conclusion

The benefits that can be drawn out of the use of SureTEC admixtures could be immense and will help not only the concrete producer but also the client and the consultants in ensuring the ultimate quality of the concrete that goes into the formwork. For a consultant specifying the mix, the quality of concrete and strength achievement is assured. For the owner and client, the durability of the concrete is ensured as there is no re-tempering of concrete either with water or admixture. For a concrete producer, there is tremendous saving not only terms of QC time, cost of concrete, etc, but also in terms of mix optimisation. This can very well provide a concrete that sets early and develops strength faster. Therefore, specifying the performance of the concrete through the transit period needs to be emphasised at all the sites, since it brings about durability and better strength.

Charles S. Jones, Head of Business Segment Management, BASF India Limited

Economy & Market

Impactful Branding

Published

1 year ago

July 17, 2023

admin

Advertising or branding is never about driving sales. It’s about creating brand awareness and recall. It’s about conveying the core values of your brand to your consumers. In this context, why is branding important for cement companies? As far as the customers are concerned cement is simply cement. It is precisely for this reason that branding, marketing and advertising of cement becomes crucial. Since the customer is unable to differentiate between the shades of grey, the onus of creating this awareness is carried by the brands. That explains the heavy marketing budgets, celebrity-centric commercials, emotion-invoking taglines and campaigns enunciating the many benefits of their offerings.
Marketing strategies of cement companies have undergone gradual transformation owing to the change in consumer behaviour. While TV commercials are high on humour and emotions to establish a fast connect with the customer, social media campaigns are focussed more on capturing the consumer’s attention in an over-crowded virtual world. Branding for cement companies has become a holistic growth strategy with quantifiable results. This has made brands opt for a mix package of traditional and new-age tools, such as social media. However, the hero of every marketing communication is the message, which encapsulates the unique selling points of the product. That after all is crux of the matter here.
While cement companies are effectively using marketing tools to reach out to the consumers, they need to strengthen the four Cs of the branding process – Consumer, Cost, Communication and Convenience. Putting up the right message, at the right time and at the right place for the right kind of customer demographic is of utmost importance in the long run. It is precisely for this reason that regional players are likely to have an upper hand as they rely on local language and cultural references to drive home the point. But modern marketing and branding domain is exponentially growing and it would be an interesting exercise to tabulate and analyse its impact on branding for cement.

Concrete

Indian cement industry is well known for its energy and natural resource efficiency

Published

2 years ago

November 18, 2022

admin

Dr Hitesh Sukhwal, Deputy General Manager – Environment, Udaipur Cement Works Limited (UCWL) takes us through the multifaceted efforts that the company has undertaken to keep emissions in check with the use of alternative sources of energy and carbon capture technology.

Tell us about the policies of your organisation for the betterment of the environment.
Caring for people is one of the core values of our JK Lakshmi Cement Limited. We strongly believe that we all together can make a difference. In all our units, we have taken measures to reduce carbon footprint, emissions and minimise the use of natural resources. Climate change and sustainable development are major global concerns. As a responsible corporate, we are committed with and doing consistent effort small or big to preserve and enrich the environment in and around our area of operations.
As far as environmental policies are concerned, we are committed to comply with all applicable laws, standards and regulations of regulatory bodies pertaining to the environment. We are consistently making efforts to integrate the environmental concerns into the mainstream of the operations. We are giving thrust upon natural resource conservation like limestone, gypsum, water and energy. We are utilising different kinds of alternative fuels and raw materials. Awareness among the employees and local people on environmental concerns is an integral part of our company. We are adopting best environmental practices aligned with sustainable development goals.
Udaipur Cement Works Limited is a subsidiary of the JK Lakshmi Cement Limited. Since its inception, the company is committed towards boosting sustainability through adopting the latest art of technology designs, resource efficient equipment and various in-house innovations. We are giving thrust upon renewable and clean energy sources for our cement manufacturing. Solar Power and Waste Heat Recovery based power are our key ingredients for total power mix.

What impact does cement production have on the environment? Elaborate the major areas affected.
The major environmental concern areas during cement production are air emissions through point and nonpoint sources due to plant operation and emissions from mining operation, from material transport, carbon emissions through process, transit, noise pollution, vibration during mining, natural resource depletion, loss of biodiversity and change in landscape.
India is the second largest cement producer in the world. The Indian cement industry is well known for its energy and natural resource efficiency worldwide. The Indian cement industry is a frontrunner for implementing significant technology measures to ensure a greener future.
The cement industry is an energy intensive and significant contributor to climate change. Cement production contributes greenhouse gases directly and indirectly into the atmosphere through calcination and use of fossil fuels in an energy form. The industry believes in a circular economy by utilising alternative fuels for making cement. Cement companies are focusing on major areas of energy efficiency by adoption of technology measures, clinker substitution by alternative raw material for cement making, alternative fuels and green and clean energy resources. These all efforts are being done towards environment protection and sustainable future.
Nowadays, almost all cement units have a dry manufacturing process for cement production, only a few exceptions where wet manufacturing processes are in operation. In the dry manufacturing process, water is used only for the purpose of machinery cooling, which is recirculated in a closed loop, thus, no polluted water is generated during the dry manufacturing process.
We should also accept the fact that modern life is impossible without cement. However, through state-of-the-art technology and innovations, it is possible to mitigate all kinds of pollution without harm to the environment and human beings.

Tell us about the impact blended cement creates on the environment and emission rate.
Our country started cement production in 1914. However, it was introduced in the year 1904 at a small scale, earlier. Initially, the manufacturing of cement was only for Ordinary Portland Cement (OPC). In the 1980s, the production of blended cement was introduced by replacing fly ash and blast furnace slag. The production of blended cement increased in the growth period and crossed the 50 per cent in the year 2004.
The manufacturing of blended cement results in substantial savings in the thermal and electrical energy consumption as well as saving of natural resources. The overall consumption of raw materials, fossil fuel such as coal, efficient burning and state-of-the-art technology in cement plants have resulted in the gradual reduction of emission of carbon dioxide (CO2). Later, the production of blended cement was increased in manifolds.
If we think about the growth of blended cement in the past few decades, we can understand how much quantity of , (fly ash and slag) consumed and saved natural resources like limestone and fossil fuel, which were anyhow disposed of and harmed the environment. This is the reason it is called green cement. Reduction in the clinker to cement ratio has the second highest emission reduction potential i.e., 37 per cent. The low carbon roadmap for cement industries can be achieved from blended cement. Portland Pozzolana Cement (PPC), Portland Slag Cement (PSC) and Composite Cement are already approved by the National Agency BIS.
As far as kilogram CO2 per ton of cement emission concerns, Portland Slag Cement (PSC) has a larger potential, other than PPC, Composite Cement etc. for carbon emission reduction. BIS approved 60 per cent slag and 35 per cent clinker in composition of PSC. Thus, clinker per centage is quite less in PSC composition compared to other blended cement. The manufacturing of blended cement directly reduces thermal and process emissions, which contribute high in overall emissions from the cement industry, and this cannot be addressed through adoption of energy efficiency measures.
In the coming times, the cement industry must relook for other blended cement options to achieve a low carbon emissions road map. In near future, availability of fly ash and slag in terms of quality and quantity will be reduced due to various government schemes for low carbon initiatives viz. enhance renewable energy sources, waste to energy plants etc.
Further, it is required to increase awareness among consumers, like individual home builders or large infrastructure projects, to adopt greener alternatives viz. PPC and PSC for more sustainable
resource utilisation.

What are the decarbonising efforts taken by your organisation?
India is the world’s second largest cement producer. Rapid growth of big infrastructure, low-cost housing (Pradhan Mantri Awas Yojna), smart cities project and urbanisation will create cement demand in future. Being an energy intensive industry, we are also focusing upon alternative and renewable energy sources for long-term sustainable business growth for cement production.
Presently, our focus is to improve efficiency of zero carbon electricity generation technology such as waste heat recovery power through process optimisation and by adopting technological innovations in WHR power systems. We are also increasing our capacity for WHR based power and solar power in the near future. Right now, we are sourcing about 50 per cent of our power requirement from clean and renewable energy sources i.e., zero carbon electricity generation technology. Usage of alternative fuel during co-processing in the cement manufacturing process is a viable and sustainable option. In our unit, we are utilising alternative raw material and fuel for reducing carbon emissions. We are also looking forward to green logistics for our product transport in nearby areas.
By reducing clinker – cement ratio, increasing production of PPC and PSC cement, utilisation of alternative raw materials like synthetic gypsum/chemical gypsum, Jarosite generated from other process industries, we can reduce carbon emissions from cement manufacturing process. Further, we are looking forward to generating onsite fossil free electricity generation facilities by increasing the capacity of WHR based power and ground mounted solar energy plants.
We can say energy is the prime requirement of the cement industry and renewable energy is one of the major sources, which provides an opportunity to make a clean, safe and infinite source of power which is affordable for the cement industry.

What are the current programmes run by your organisation for re-building the environment and reducing pollution?
We are working in different ways for environmental aspects. As I said, we strongly believe that we all together can make a difference. We focus on every environmental aspect directly / indirectly related to our operation and surroundings.
If we talk about air pollution in operation, every section of the operational unit is well equipped with state-of-the-art technology-based air pollution control equipment (BagHouse and ESP) to mitigate the dust pollution beyond the compliance standard. We use high class standard PTFE glass fibre filter bags in our bag houses. UCWL has installed the DeNOx system (SNCR) for abatement of NOx pollution within norms. The company has installed a 6 MW capacity Waste Heat Recovery based power plant that utilises waste heat of kiln i.e., green and clean energy source. Also, installed a 14.6 MW capacity solar power system in the form of a renewable energy source.
All material transfer points are equipped with a dust extraction system. Material is stored under a covered shed to avoid secondary fugitive dust emission sources. Finished product is stored in silos. Water spraying system are mounted with material handling point. Road vacuum sweeping machine deployed for housekeeping of paved area.
In mining, have deployed wet drill machine for drilling bore holes. Controlled blasting is carried out with optimum charge using Air Decking Technique with wooden spacers and non-electric detonator (NONEL) for control of noise, fly rock, vibration, and dust emission. No secondary blasting is being done. The boulders are broken by hydraulic rock breaker. Moreover, instead of road transport, we installed Overland Belt Conveying system for crushed limestone transport from mine lease area to cement plant. Thus omit an insignificant amount of greenhouse gas emissions due to material transport, which is otherwise emitted from combustion of fossil fuel in the transport system. All point emission sources (stacks) are well equipped with online continuous emission monitoring system (OCEMS) for measuring parameters like PM, SO2 and NOx for 24×7. OCEMS data are interfaced with SPCB and CPCB servers.
The company has done considerable work upon water conservation and certified at 2.76 times water positive. We installed a digital water flow metre for each abstraction point and digital ground water level recorder for measuring ground water level 24×7. All digital metres and level recorders are monitored by an in-house designed IoT based dashboard. Through this live dashboard, we can assess the impact of rainwater harvesting (RWH) and ground water monitoring.
All points of domestic sewage are well connected with Sewage Treatment Plant (STP) and treated water is being utilised in industrial cooling purposes, green belt development and in dust suppression. Effluent Treatment Plant (ETP) installed for mine’s workshop. Treated water is reused in washing activity. The unit maintains Zero Liquid Discharge (ZLD).
Our unit has done extensive plantations of native and pollution tolerant species in industrial premises and mine lease areas. Moreover, we are not confined to our industrial boundary for plantation. We organised seedling distribution camps in our surrounding areas. We involve our stakeholders, too, for our plantation drive. UCWL has also extended its services under Corporate Social Responsibility for betterment of the environment in its surrounding. We conduct awareness programs for employees and stakeholders. We have banned Single Use Plastic (SUP) in our premises. In our industrial township, we have implemented a solid waste management system for our all households, guest house and bachelor hostel. A complete process of segregated waste (dry and wet) door to door collection systems is well established.

Tell us about the efforts taken by your organisation to better the environment in and around the manufacturing unit.
UCWL has invested capital in various environmental management and protection projects like installed DeNOx (SNCR) system, strengthening green belt development in and out of industrial premises, installed high class pollution control equipment, ground-mounted solar power plant etc.
The company has taken up various energy conservation projects like, installed VFD to reduce power consumption, improve efficiency of WHR power generation by installing additional economiser tubes and AI-based process optimisation systems. Further, we are going to increase WHR power generation capacity under our upcoming expansion project. UCWL promotes rainwater harvesting for augmentation of the ground water resource. Various scientifically based WHR structures are installed in plant premises and mine lease areas. About 80 per cent of present water requirement is being fulfilled by harvested rainwater sourced from Mine’s Pit. We are also looking forward towards green transport (CNG/LNG based), which will drastically reduce carbon footprint.
We are proud to say that JK Lakshmi Cement Limited has a strong leadership and vision for developing an eco-conscious and sustainable role model of our cement business. The company was a pioneer among cement industries of India, which had installed the DeNOx (SNCR) system in its cement plant.

Concrete

NTPC selects Carbon Clean and Green Power for carbon capture facility

Published

2 years ago

October 12, 2022

admin

Carbon Clean and Green Power International Pvt. Ltd has been chosen by NTPC Energy Technology Research Alliance (NETRA) to establish the carbon capture facility at NTPC Vindhyachal. This facility, which will use a modified tertiary amine to absorb CO2 from the power plant’s flue gas, is intended to capture 20 tonnes of CO2) per day. A catalytic hydrogenation method will eventually be used to mix the CO2 with hydrogen to create 10 tonnes of methanol each day. For NTPC, capturing CO2 from coal-fired power plant flue gas and turning it into methanol is a key area that has the potential to open up new business prospects and revenue streams.