THE DEVELOPMENT OF BIOCONCRETE: A SELF HEALING CONCRETE

In partial fulfillment of the requirements for CHM031: Chemistry for Engineers

Julhany B. ButongkaySeptember 07 2019

THE CONCRETE

History

In the world we live in, buildings and infrastructures are common in our sight. These structures provide our basic needs like shelters, it also connects us to the place we wanted to go. So, these structures were made to be strong, durable and should last longer. Concrete is one of the materials that make our shelters safe for us. Through the years, started at around 7000 BC, concrete was already available and being used by early civilizations.

Concrete was used in making a famous structure from ancient times like the Pyramid of Giza, Eddystone lighthouse, The Parthenon, etc.

Concrete as defined by the Concrete technology, it is a mixed material used in construction which is made of cement, fine aggregates or sand, and coarse aggregates or the gravel which hardens in a period when mixed with water. The earliest discovery of concrete was dated about 7000 BC.

It was reported that the concrete was made from a lime concrete that was made from burnt limestone to produce quicklime. These materials harden when mixed with stone and water which acts as their concrete. Ancient Roman discovered stronger concrete than previously discovered. This was made out of volcanic ash containing silica and alumina which, when mixed with lime, creates a stronger form of cement which they named pozzolanic cement. Its name was derived from the place Pozzuoli where they discovered the said ashes. With the fall of the Roman empire, the Concrete lost in civilization.

The rebirth of concrete started when John Smeaton discovered soft limestones containing soft clay materials which result in hydraulic cement. This cement contains pozzolan which came from Italy. The hydraulic cement was used to construct John Smeaton’s famous Eddystone Lighthouse. In the early 1800s, natural cement was manufactured in Rosendale, New York. This result to a cement called Hydraulic cement which was patented by Joseph Aspdin which named because it was believed that it resembles Portland stone – high-quality limestone that can be found an isle in Portland.

At the year 1845, Portland cement was manufactured by I.C Johnsons of White and sons, Swanscombe, England. Generally, Portland cement was based on the Hydraulic cement that was patented by Aspdin. But this cement improved the properties made in the previous hydraulic cement. By the year 1860s, Portland Cement was imported to the United States and by the 1870’s it was properly produced in the United States. Portland cement became known for durability and it only hardens for several hours. But this Portland cement is weak in tension, and it is very susceptible to damage because of its porosity which is caused by frost and salts. These disadvantages were developed and made up new types of cement until it reaches the cement we know today.

Concrete is widely used in the world, every building, roads, canals, ports, and bridges were mainly made of concrete. According to an article by the World Business Council for Sustainable Development, concrete is used twice more than the number of all other building materials used in the construction like woods, steels, plastics, and aluminum. Thus, it makes it the second most consumed substance in the world which is next to water (Concrete Helper,2012). Concrete is being manufactured at around 25 billion tons each year throughout the world or it is equivalent to over 3.8 tons each person a year (World Business Council for Sustainable Development,2009).

Production

As defined previously, concrete is a mixture of cement, aggregates, and water. So, in producing concrete, we use Portland cement to act as a paste to our mixture so that the aggregates named as sand and rocks harden. Cement is not naturally available like other resources like water. To produce cement, we need limestones, shells, chalk, clay, slate, blast furnace slag, silica sand, and iron ore. There 2 ways to manufacture cement, the most common Dry method, and the wet method. Raw materials like limestones, clay, and other materials were being quarried down. After it was obtained, the rocks are crushed into a different stage. The first stage crushes the rocks, not over 6 inches big, then the second one crushes the rocks into 3 inches or smaller sizes. The rocks that were crushed is mixed with other ingredients like iron ore, or fly ash and ground, and put inside a cement kiln which will be heated up at the temperature of 2,700 degrees Fahrenheit. This method uses Dry method if Wet method was used the rocks were being crushed with water before being put inside the kiln. As it travels around the kiln, some elements get rid of in the form of gases. After the process inside the kiln, a Clinker will be produced. Clinker, a grey ball which is about the size of a marble, is the result of the materials mixed inside the kiln. This clinker will be cooled and will be ground after to become powder. Then it is ready to be distributed to construction as we named it cement. (Portland Cement Association,2018)

Chemicals reactions

Traditionally, Portland cement was used in making concrete. In making Portland cement, chemical reactions are present. As we are all knowledgeable Portland cement mainly came from limestones which are mostly composed of calcium carbonate ( CaCO3 ) which starts by producing Calcium Oxide (CaO) or the quick lime. In the process of making cement, there is about 5% of carbon dioxide (CO2)) released in the atmosphere every year. Thus it will be led to the Chemical equation. CaCO3?CaO+CO2.

Since Silicon oxides and Aluminum will be mixed with quick lime (CaO), in the mixing of cement to make the concrete these materials will be hydrated or mixed with water in order to make concrete harden.

In determining the chemical reaction occurred in producing concrete, we add variable x to the chemical equation which represents different values or materials added to the mixed concrete which doesn’t affect its basic chemical reaction. So we will have three representation of chemical reactions when hydration occurs to the production of concrete. And these are:

3 CaO? Al2O3+6H2O?Ca3Al2(OH)122CaO?SiO2+xH2O ? Ca2SiO4?xH2O3CaO+SiO2+x+1H2O?Ca2SiO4?xH2O+Ca(OH)2The reaction involved in producing cement is at a very slow rate. That’s why engineers included curing time of the concrete in their time schedule of the project they are into because these concretes do not fully harden at short span of time. It needs some time for it to be fully cured and gets hard as we wanted.

Mechanical properties

BIOCONCRETE

Introduction

One of the most common and problem regarding concrete is having cracks (Ozinga,2016). When concrete starts to crack, its structure begins to degrade. By this problem, The microbiologist Hendrik Jonkers developed a self-healing concrete or the Bioconcrete. Bio concrete and the traditional concrete has the same method of manufacturing, the only difference is the healing agent that is added to the mixture of Bioconcrete. This Healing agent is a harmless bacterium which became active when water will react on it. One of the challenges in the study was finding the exact bacteria that could live in places like concrete and can live in a very long time. Concrete is a rock-like material which is very dry which some bacteria cannot live with that environment. Jonkers used the bacteria known as Bacillus Genus which can grow in alkaline conditions like the concrete, it also produces pores that allows them to live for years with the absence of food and oxygen. The bacteria remain dormant for years in the concrete without food or oxygen until water will enter a crack and activate them. Jonkers and his team added the nutrient Calcium lactate in the mixture that could act like a food to the bacteria for it to produce limestones that could heal the cracks in the concrete.

During the mixing, for the bacteria to survive, Jonker and his team set the bacteria and calcium lactate in a biodegradable capsule which will be added to the wet mixture of concrete. When cracks will appear on the concrete and the water will enter those cracks, it can activate the bacteria. The bacteria will begin to grow, multiply and consume the lactates provided for them. With this, they produce limestones or calcite to seal up the cracks.

Advantages

The basic concept of the Bioconcrete is the concrete that can self-heal. This alone has the major advancement to the traditional concrete because it doesn’t require a human to repair it which lessens the effort needed for repairs. Aside from that, with its ability to self-heal, it reduces the amount spent on repairing the structure. According to a research conducted by (Jones, Kisslinger & Yatsenko,2019), only 1% of the total cost of concrete is spent in the actual concreting process and the 99% is spent in repairs and maintenance of it. In addition, it also increases the durability of the concrete because according to (Winktor and Jonkers,2011) as cited in the study of (Ponraj et al.,2015), when a crack appears on the surface of the structure, the bacteria repairs it directly thus it prevents the steel reinforcement and the concrete itself to corrode and making the structure collapse.

Furthermore, according to (Ponraj et al.,2015) Bio concrete has an 18% improvement in compressive strength. Which shows that the Bioconcrete increases the strength of the concrete. It was shown in the study of (Ponraj et al., 2015) that at 28 days of observance, a 25% increase was evident in the compressive strength of the concrete when bacteria were added. Chemical reaction

The current and future uses of bio-concrete

As a part of the testing and studying of bio-concrete, it was tested and used in different environments with different temperatures. One of the current use of bio-concrete is being as the protective layer of a parking garage in Apeldoorn, Netherlands. The bio concrete was used there as a top layer of the garage floors with a dimension of 12,000 square meters to prevent water from leaking through the garage floors and destroying its structural aspects.

Furthermore, another use of Bioconcrete was making the irrigation canals in Ecuador. One of the problems they face is that the concrete in their irrigation was not reinforced with steels so the concrete began to crack in only a short period and allowing the water to escape onto the walls. As their, solution, they used Bioconcrete that was reinforced with abaca fibers to increase its tensile strength.

Lastly, For the future of Bioconcrete, it can replace the traditional concrete we use today. This means that it will be used in buildings, bridges, roads, tunnels, ports, etc. because all of the structures are very hard to maintain and it is very costly to repair.

References

Concrete Helper. (2011, October 28). Concrete facts. Retrieved from

The Future of Things. (2012, November 2). BioConcrete – Self Healing Concrete. Retrieved from

Ponraj, M., Talaiekhozani, A., Zin, R., Ismail, M., Abd Majid, M., Keyvanfar, A., & Kamyab, H. (2015, May 27). Bioconcrete strength, durability, permeability, recycling, and effects on human health: A review. Retrieved from

Portland cement organization. (2018). How Cement Is Made. Retrieved from

Stewart, A. (2016, March 7). The ‘living concrete’ that can heal itself. Retrieved from BIBLIOGRAPHY Brown, L. S., & Holme, T. A. (2011). Chemistry for Engineering students (2nd ed.). United States of America: Mary Finch.

Development, W. B. (2009, July). World Business Council for Sustainable Development. Retrieved September 06, 2019, from

Jones, E., Kisslinger, J., & Yatsenko, Y. (2019, March 08). University of Pittsburgh, Swanson School of Engineering. Retrieved September 6, 2019, from

Princeton. (n.d.). Princeton.edu. Retrieved september 07, 2019, from