November 2023

Author: Sergio Moraga, Civil Engineer, Nicaragua

LC3 is an innovative blended Portland cement that includes the addition of metakaolin (calcined kaolinite clay) and limestone. The main components of LC3 are clinker, calcined clay, limestone and gypsum. It is an environmentally friendly cement that contains less clinker and uses less fuel for its production.

 The workshop

The theoretical sessions dealt with how to find the appropriate types of clays and their physical and chemical characterization. The selection of the raw material in sufficient quantities and heterogeneous quality makes it one of the fundamental steps for the manufacture of LC2/LC3.

It was “hands on”, the procedure and equipment required for sampling was demonstrated by a specialist geologist. The importance of working with geological maps, satellite monitoring systems and field exploration was highlighted.

Clays are weathering products of all types of rocks and, as such, are available in abundance near the earth’s surface in all geological environments. The most suitable clay types, containing kaolinite, are typical of tropical and subtropical environments.

Clays containing 40% to 60% kaolinite are ideal for LC3 production. Clay is the second most important component in cement crude (10-25%) and provides the necessary alumina. In many cases, impure clays are used, with a high calcite content (marls), which contribute to increasing the percentage of calcium carbonate in the crude. Common clay is usually used for gray cement. The additional alumina in the metakaolin reacts with the ground limestone, producing a less porous material and thus providing equal strength with higher levels of clinker substitution. Various criteria for clay selection and procedures for sampling, mapping, etc. were presented in the course.

Limestone is the main component (75-85%) for the manufacture of conventional cement. Its specifications for the manufacture of gray cement are less stringent than for other applications. LC3 blends usually contain about 15% limestone, plus 30% calcined clays, 5% gypsum and 50% clinker.

Another important issue was the type, equipment and procedure for grinding and calcining the raw material, the control of fineness and color, since these cements are usually reddish in color due to the direct effect of the clay.

In this globalized world, modeling by computational systems and the collection of data of the processes of calcination, milling, etc. through the automation of these processes, is important for decision making and optimization of the results. The small plant of the university has highly qualified personnel who have designed, monitored and developed such modern systems that make it possible to supervise the plant through a series of sensors that send the information to the command center and to a cell phone App of the supervisor in charge.

 We also visited the plant and were able to know the production procedures, equipment, chemical and materials laboratories attached to the plant, and explained the types of tests or protocols that the raw material and the final product are subjected to in order to guarantee quality.

A visit was made to the Santa Maria Keys where the research team has been systematically sampling concrete blocks manufactured with LC3 and Portland Cement for more than 10 years. These blocks are subjected to very aggressive agents such as salts, chlorides, effects of carbonation of the concrete, weathering, erosion caused by sea waves and wind, etc. All these tests are used to determine the durability of the concrete and the degree of protection offered to the steel reinforcements inside it.

In addition to the experimental plant, CIDEM scientists are working on different projects using LC2/LC3, for example, the rehabilitation of a water channel with LC2 mortar, whose function was to waterproof the cracks. In addition, they are working on an ambitious project at the country level, the rehabilitation of the  “Malecon”, the famous waterfront of Havanna, using 100% LC3 cement.

Conclusion:

The experience of knowing the production processes of LC2/LC3, offered the technical team a better perspective of the methods, procedures and studies needed to replicate the production in Nicaragua and Latin America.

The production and commercialization of LC2 can be a viable business idea as a partial substitute for cement in the production of prefabricated products, mortars and finishes. However, intense marketing work must be done and economic advantages and physicochemical properties that improve the quality of existing products must be supported.

It has been possible to highlight the advantages and opportunities of LC3 as a competitive material, suitable for any type of social or private project, since there are already solid studies of resistance, durability, consistency, physical and chemical properties applied to concrete. In fact, it is possible to compare it with traditional OPC concretes.

It has been demonstrated that the production of LC3 contributes to the reduction of CO2 emissions by up to 40% and to comply with the global agenda of decarbonization of industrial processes, energy and transportation.

We would like to highlight the perfect organization and development of this event. Thanks to the great effort of the professionals and specialists of CIDEM and Universidad Central de Las Villas, this seminar was successful. The scientific level and preparation of the speakers was excellent, the necessary coordination so that the participants had a great stay and experience in this beautiful country, Cuba, a country of unique and invaluable natural and cultural wealth. It is also worth mentioning the hospitality, affection and kindness of its people, who, despite the economic difficulties caused by a brutal blockade, always keep a positive spirit, a smile and a warm and sincere hug with a delicious Cuban coffee.