Civil Engineering ETDs

Publication Date

Fall 12-2016

Abstract

Earthen structures have a long architectural and cultural heritage in New Mexico. Similar structures are evident around the world. With the current depletion of natural resources and high cost of materials, compressed earth block construction offers a sustainable building material alternative. Stabilized compressed earth blocks (SCEB) are compressed earth blocks with additives such as, hydrated lime or Portland cement to protect the earth block from absorbing water. SCEBs are being produced using native soils for residential construction on the Jemez Pueblo in New Mexico.

The primary goal of this research is to enable production of SCEBs with native soils from the Jemez Pueblo. The objectives of this research are to identify suitable local soils to be used to develop a compressed earth block mix design, compare the mechanical characteristics of SCEB to commercial adobe blocks, and investigate the mechanical behavior of SCEB prism and wall assemblies.

Close to 50 native soil locations at the Jemez reservation in New Mexico were investigated. These soils were classified according to the Unified Soil Classification System (USCS) considering their grain size distribution, plasticity limit and swelling potential. A method for down selection of the soils suitable for compressed earth block production was developed. In addition, the clay mineralogy of the suitable soils and soil mix designs were determined using X-ray Diffraction (XRD) and Scanning electron microscopy (SEM).

SCEB mix design included two selected native soils, two sands and either Type S hydrated lime or Type II Portland cement. These materials were mixed to fabricate SCEBs of nine different SCEB mix designs. Compressive and flexural strength tests of the SCEBs were performed and compared to commercial adobe blocks. Tests to determine water absorption characteristics in SCEBs including initial rate of absorption, total absorption and sorptivity were also carried out. The mechanical and absorption characteristics of SCEBs were correlated to the mix design and the native soil classification. The ratio of clay and sand in the compressed earth block mix has a significant correlation with the mechanical and absorption characteristics of SCEBs. The results from all the testing showed that an optimum mix design was found for the nine blocks evaluated.

SCEB assemblies, including prisms and wall panels were produced with standard type S mortar. Prisms made of SCEB units were tested to determine the compressive strength, bond strength, and shear strength. The time-dependent creep of the SCEB prism at 56 days of age was also evaluated. These measurements showed that creep displacement has a significant effect on the total displacement of the prism assembly. The approximately 570 mm x 570 mm (22 in. x 22 in.) SCEB wall panels made of the optimum SCEB were tested under in-plane shear using a diagonal compression test. The results of the diagonal compression test show that the SCEB wall assembly obtained a lateral strength comparable to rammed earth.

The results showed that some SCEBs have higher compressive and flexural strengths than commercial stabilized adobe. SCEBs provide a resilient, sustainable building material and are suitable for use in residential construction for the Jemez Pueblo in New Mexico.

Keywords

compressed earth blocks, masonry, earth structures, mechanical characteristics, soil classification, soil cement

Document Type

Thesis

Language

English

Degree Name

Civil Engineering

Level of Degree

Masters

Department Name

Civil Engineering

First Committee Member (Chair)

Dr. Mahmoud Reda Taha

Second Committee Member

Dr. John Stormont

Third Committee Member

Tom Bowen

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