Experimental Study of Adobe Masonry and its Adherence with Reinforced Concrete Confinement Elements

Jesús A Velarde Gil L,José A Espuna M,Rubén S Roux G,María T Sánchez M

doi:10.13189/cea.2021.090213

Abstract

The constructions with adobe masonry confined with concrete elements, experience a separation between them, mainly due to the inherent physical and chemical characteristics of both materials that are not very compatible with each other; adobe, a raw masonry with a high clay content, undergoes changes in its shape in the presence of humidity and temperature variation, which affects its adherence to concrete elements, compromising the confinement, function and stability of the walls. The different coefficients of expansion and contraction between concrete and adobe, added to their physical properties, make it difficult to achieve adequate adherence between these two materials. In the present study, 6 mixtures of earth (adobe) were designed, with different granulometry proportions to measure the adherence between adobe and concrete, identifying the most suitable one with the purpose of using it as a bonding material in walls for houses, from this study, with the best response being the sample MA-3. The test methodology was based on standards applicable to concrete and annealed brick masonry, as there is no available one for this material. Thirty-six adobe specimens adhered to concrete were tested, to which a normal load was gradually applied to their cross section, to a piece of adobe between two pieces of concrete, recording the ultimate horizontal shear stress between both materials. The scope is considered the result of the test of adobe pieces adhered to concrete subjected to horizontal shear force, considering different granulometry in the composition of the adobe mixture. This work provides a starting point for the standardization of the test and the justification of the need for an additional element that contributes to the confinement.

Highlights

The confined masonry arises from the need for perimeter reinforcement with reinforced concrete elements that guarantee the monolithic behavior between both structural materials [1]; the concept of confinement is based on the positive results that have been observed in annealed mud brick constructions, forming boards that provide deformation capacity much greater than that of unconfined walls [2]
Adherence is one of the most important physical properties in hardened glue mortars with variable and unpredictable responses, with aspects that have to be addressed such as resistance, adherence degree and durability [6]; these same standards refer to others that must be followed to measure adherence, but that does not relate this for concrete with adobe, there are few studies in this regard, being able to take as a reference experiment carried out with mud mortar in union of adobe pieces with an average shear stress of 0.038 Mpa [7]; or in the union of cement blocks with cement-sand mortar [8]
The adherence between adobe and concrete elements is of vital importance for the good structural performance of constructions based on these materials

Summary

Introduction

The confined masonry arises from the need for perimeter reinforcement with reinforced concrete elements that guarantee the monolithic behavior between both structural materials [1]; the concept of confinement is based on the positive results that have been observed in annealed mud brick constructions, forming boards that provide deformation capacity much greater than that of unconfined walls [2].The material most used in rural housing walls in Latin America is adobe, but the vulnerability of these systems to the presence of a seismic event, and the lack of rigidity of their walls, as well as their bond with the roof, has led to the adobe masonry proposal with confinement based onCivil Engineering and Architecture 9(2): 404-409, 2021 concrete elements, seeking to improve this weakness in stability; the lack of that confinement in the walls or elements that guarantee a union between them causes the existence of different modes of failure: by bending in the plane and outside it [3], compression, flexo-compression [4], shear stress, failure in wall joints, roof wall joint [5].In the union of adobe with concrete, there is an adherence problem after these materials are in a dry state, which causes a separation between them, and hinders the optimal work so that the wall works as a rigid diaphragm, considering that they are two materials with poor compatibility, different chemical composition and manufacturing process, in addition to possessing different physical properties such as shrinkage, compressive strength, modulus of elasticity and rigidity of the structural element.Adherence is one of the most important physical properties in hardened glue mortars with variable and unpredictable responses, with aspects that have to be addressed such as resistance, adherence degree and durability [6]; these same standards refer to others that must be followed to measure adherence, but that does not relate this for concrete with adobe, there are few studies in this regard, being able to take as a reference experiment carried out with mud mortar in union of adobe pieces with an average shear stress of 0.038 Mpa [7]; or in the union of cement blocks with cement-sand mortar [8].Even so, [1], mentions that the masonry-confinement tie-column connection can be toothed or flush, providing horizontal steel elements embedded in the mortar joint and anchoring inside the tie-column.This work seeks to establish parameters for the measurement of that adherence between the adobe and the confinement element without considering any type of additional reinforcement; identifying the one with the best physical and mechanical behavior out of 6 mix designs with different granulometries. Civil Engineering and Architecture 9(2): 404-409, 2021 concrete elements, seeking to improve this weakness in stability; the lack of that confinement in the walls or elements that guarantee a union between them causes the existence of different modes of failure: by bending in the plane and outside it [3], compression, flexo-compression [4], shear stress, failure in wall joints, roof wall joint [5]. In the union of adobe with concrete, there is an adherence problem after these materials are in a dry state, which causes a separation between them, and hinders the optimal work so that the wall works as a rigid diaphragm, considering that they are two materials with poor compatibility, different chemical composition and manufacturing process, in addition to possessing different physical properties such as shrinkage, compressive strength, modulus of elasticity and rigidity of the structural element.

Methods

Findings

Discussion

Conclusion