34 Material Properties for Seismic Testing: Cement


Material Properties for Cement

Requested Research

  • Literature review on the influence of cement quality in mixtures for mortars and concretes, with a particular focus on freshness and local brands.
  • Literature overview of Building Biology and it’s components in general.
  • Main request 1. Determination of the key material properties of cement, that may be of influence on the strength development of mortars or concrete elements.
  • Research about what possible electromagnetic fields and radiations we may expect, in any kind of alternative construction type or building element.
  • Main request 2. Determination of suitable lab testing methods for obtaining the necessary material properties, including actual testing of specimens. Both main requests are preferably done in collaboration with Structural and Earthquake Engineering.
  • Develop tools and machines for on-site testing of material properties of cement in rural and remote areas. Preferably with Mechanical and Product Engineering.

Status of Research

This is a KEY assignment within the overall SMARTnet project, where all disciplines come together. Open for students and professionals of Architecture and Material Science, as well as for Mechanical and Product Engineering, as well as for Structural and Earthquake Engineering. For more info please contact Martijn Schildkamp at info@smartshelterresearch.com or see our website www.smartshelterresearch.com

Background: Material Properties of Non-Engineered Techniques

The knowledge of how conventional techniques behave in earthquakes is quite high and such techniques have been tested thoroughly. Brick masonry walls and concrete structures can be calculated because the material properties are well known. We can even make quite elaborate computer models of such engineered structures.

This is not the case for most traditional, natural and alternative materials. It is very difficult to model or calculate techniques like stone masonry or earthen structures, due to a high ratio of uncertainties and variables such as material inconsistency and local workmanship. Somehow, these variables must be taken into account.

Background: Rubble Stone Masonry

Our focus is on rubble stone masonry as it is still widely used in the Himalayan areas, which consists of field stones and mortar, which (in the case of cement mortar) is a combination of cement, sand and water. If we incorporate reinforced concrete bands into the walls, we must also add aggregates and reinforcement steel to the list of materials.

This particular research is focusing on each of these materials separately and aims to gain better understanding of the material properties of stones, cement, sand, water, aggregates and steel bars, by investigating the effects of this particular element within their combined actions into mortars, concretes or masonry.

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Traditionally, rubble stone masonry is built with mud mortar. In seismic areas the use of mud is not recommended, as was painfully demonstrated during the 2015 Gorkha earthquakes in Nepal, causing widespread damage and collapse among these low-strength masonry buildings. Therefore, cement mortars are recommended for the masonry with bricks, blocks and stones.

Cement is a binding agent used for construction purposes, that sets, hardens, and adheres to other materials to bind them together, such as sand for mortars, or sand with aggregates in concretes. Cement is characterized as either hydraulic or non-hydraulic, depending on the ability of the cement to set in the presence of water. Hydraulic types of cement set and become adhesive due to a chemical reaction between the dry ingredients and water. It comes in several types, such as Ordinary Portland Cement (OPC) and Portland Pozzolana Cement (PPC). Different grades of cement exist, such as Grade 43 or 53, and different types of cement can be used for different mortar types (S, N, M). Many different brands are available in the markets, with many quality stamps, such as in Nepal on the picture below.

The first step in this assignment is to undertake a literature review and to compile a clear and concise overview of all possible cement types, as well as the differences between cement brands in the Himalayan areas.

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Traditionally, rubble stone masonry is built with mud mortar. In seismic areas the use of mud is not recommended, as was painfully demonstrated during the 2015 Gorkha earthquakes in Nepal, causing widespread damage and collapse among these low-strength masonry buildings. Therefore, cement mortars are recommended for the masonry with bricks, blocks and stones.

Cement is a binding agent used for construction purposes, that sets, hardens, and adheres to other materials to bind them together, such as sand for mortars, or sand with aggregates in concretes. Cement is characterized as either hydraulic or non-hydraulic, depending on the ability of the cement to set in the presence of water. Hydraulic types of cement set and become adhesive due to a chemical reaction between the dry ingredients and water. It comes in several types, such as Ordinary Portland Cement (OPC) and Portland Pozzolana Cement (PPC). Different grades of cement exist, such as Grade 43 or 53, and different types of cement can be used for different mortar types (S, N, M). Many different brands are available in the markets, with many quality stamps, such as in Nepal on the picture below.

The first step in this assignment is to undertake a literature review and to compile a clear and concise overview of all possible cement types, as well as the differences between cement brands in the Himalayan areas.

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Cement is an expensive component for many people in developing countries, and for that reason they often reduce the amount of cement in their mixtures to save costs, resulting in a bad quality of mortar and concrete elements.
However, the amount of cement within the mixing ration is not the main focus of this research. This assignment looks into the quality of the cement itself.

In many places of the world cement is difficult to obtain, such as in rural and remote areas where cement must travel long distances before it reaches its final destination on the construction site. The cement bags are transported from the cities to the local market in the mountains, on bumpy roads by tractors or on top of local buses. Here they are sometimes stored for long periods of time before they are carried further on the backs of porters. The way and care of transportation, as well as the conditions of storage, are of great influence on the quality and freshness of the cement. It is often seen that the cement has become moist and that lumps have formed in the bags. People will try to pulverize the lumps and put these into their mixes anyway

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In order to determine certain mechanical properties of the cement, it is important to interact with the disciplines of structural and earthquake engineering, to understand which properties are needed for their calculations and models. For testing of materials, standard test procedures exist such as ASTM, RILEM or Indian Standards. Part of the literature review is to create an overview of suitable tests and to describe in detail which steps must be undertaken to create consistent test outputs. During the actual testing of samples and specimens, all parameters must remain constant, with the only variable being the cement. That is the quality of the cement, not the amount.
An important question that needs to be addressed is: how can we simulate old cement for our testing purposes? Also, we are interested to know if today there is still a big difference between the quality of Indian and Nepali types of cement.

Furtherly, this research assignment aims to develop field tests that can simulate the highly controlled lab testing. The challenge is to develop low-tech test procedures and methodologies by using low-cost testing equipment, that is locally applicable in the field, but with reliable test outcomes. This will enable the researchers to conduct simple tests in the field, and it helps the homeowners and masons to buy high-quality products and to use the correct materials.

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