An evaluation of repair mortars installed by worm-pump spraying

Magazine of Concrete Research, 2000

This paper, which reports on part of a three year research project into wet-process sprayed mortars and concretes for repair, investigates the hardened performance of wet process sprayed mortars. Seven commercially available pre-packaged repair mortars were pumped and sprayed through a worm pump, three through a piston pump and two through a dry spray machine. A laboratory designed mortar was also worm and piston pumped. The properties measured included compressive and flexural strength, tensile bond strength, hardened density, modulus of elasticity, air permeability, sorptivity and drying and restrained shrinkage. In-situ test specimens were extracted from 500mmx500mmx100mm deep sprayed panels. Tests were also conducted on corresponding cast specimens and, where possible, on specimens that had been sprayed directly into a cube or beam mould. A new test to quantify the degree of reinforcement encasement has been developed and an initial investigation into the measurement of the restrained shrinkage of in-situ repairs is presented. The compressive and flexural strengths of the laboratory mix were comparable with the best of the commercially available preblended mortars. The values for modulus of elasticity, when compared with the compressive strength, were lower than published formulas for this relationship would suggest, especially at lower strengths.

2000

This paper, which reports on part of a three year research project into wet-process sprayed mortars and concretes for repair, investigates the hardened performance of wet process sprayed mortars. Seven commercially available prepackaged repair mortars were pumped and sprayed through a worm pump, three through a piston pump and two through a dry spray machine. A laboratory designed mortar was also worm and piston pumped. The properties measured included compressive and flexural strength, tensile bond strength, hardened density, modulus of elasticity, air permeability, sorptivity and drying and restrained shrinkage. In-situ test specimens were extracted from 500mmx500mmx100mm deep sprayed panels. Tests were also conducted on corresponding cast specimens and, where possible, on specimens that had been sprayed directly into a cube or beam mould. A new test to quantify the degree of reinforcement encasement has been developed and an initial investigation into the measurement of the restrained shrinkage of in-situ repairs is presented. The compressive and flexural strengths of the laboratory mix were comparable with the best of the commercially available preblended mortars. The values for modulus of elasticity, when compared with the compressive strength, were lower than published formulas for this relationship would suggest, especially at lower strengths. The air permeability of most of the mortars was lower than that for normal wet-cured concrete and decreased with an increase in compressive strength. The sorptivity values showed no clear relationship with the compressive strength. The type of wet-process pump was found to have little effect on the insitu compressive and flexural strengths, but did affect the bond strength, although mainly due to the stream velocity and w/c ratio rather than the pumping process. The pump type also effected the reinforcement encasement with higher stream velocities producing better encasement. The mixes exhibited a wide range of drying shrinkage, but the data from the restrained specimens suggest an actual repair is influenced as much by ambient conditions as it is by the mix proportions.

1999

… of Dundee, Scotland, UK on 8 …, 1999

Construction and Building Materials, 1994

Increasingly, large sums are being spent on the repairs and maintenance of concrete surfaces using one or other of the hundreds of surface repair materials available on the market. Unfortunately, however, information on these materials has always been scarce and manufacturers have been unable to supply specific data on their products' resistance to harsh climatic conditions. The 5 year project described in this paper was initiated in an aim to evaluate and select surface repair mortars such as cementitious grouts, polymer-modified cement-based mortars containing styrene-butadiene rubber (SBR) and acrylics, epoxy mortars, etc., and eventually to install them at different dam sites in Quebec. About 40 mortars from different manufacturers were intensively tested for their physico-mechanical and durability tests in the laboratory. Of these, 21 mortars were then selected and installed on a small scale on the spillway of a Hydro-Qu6bec dam. After careful analysis of the laboratory data and periodic inspections of the products, the six best were selected and recently installed on a large scale on two spillway aprons and their adjacent piers. The paper presents some of the mortar evaluation and selection criteria, the small-scale installation and inspection of 21 products and, specifically, the large-scale installation of the selected mortars and their cost effectiveness,

Procedia Structural Integrity, 2019

Two types of lime-based mortars were used in the rehabilitation of wall coverings, and the need to study their mechanical behavior and durability arose. About the mechanical behavior were analyzed flexural strength, compressive strength and the peeling stress at the "pull-off" test. As to durability, particularly in view of the rising damp and infiltration, this study was performed by capillary water absorption test and immersion due to water absorption at 48 (atmospheric pressure) for the determination of water content, focusing on its state of degradation, in order to mitigate the risks of choice. In this study, the results obtained in the tests of a traditional lime mortar with a 1: 3 volume trace with the samples of a prefabricated mortar of hydrated lime were compared, and in both mortars obtained values close to those recommended. However, the traditional hydraulic lime mortar has a peel force resistance well above the prefabricated mortar, and the recommended amount in domestic articles.

Sustainability, 2021

The subject matter of the work presented here is the development and evaluation of novel lightweight mortars that meet the functional and technical criteria imposed on repair mortars. In a broad experimental campaign, lime, natural hydraulic lime, and lime–cement mortars were designed and tested. Lightweight aggregate, expanded perlite, granules from expanded glass and zeolite were used as full replacements for quartz sand. The hardened mortars were tested at the ages of 28 days and 90 days. The conducted tests and analyses were focused on the assessment of structural, mechanical, hygric and thermal parameters. The salt crystallization resistance and effect of salt presence on the hygroscopicity of the investigated mortars were also investigated. The use of lightweight aggregates in the composition of mortars resulted in their high porosity, low density, satisfactory mechanical parameters, improved water vapor transmission capability and water absorption. The mortars with expanded p...

2002

The present research investigates the polymer/cement (P/C) ratios (0, 5, 10, 15, and 20%) on mechanical and durability properties of modified mortar exposed to different curing conditions. These properties include compressive and flexural strengths, flow spread test, water absorption, density, coefficient of water absorption, sorptivity, and salt/sulfate resistance tests. The results show that combining seven days of water submergence and 21 days of ambient temperature curing (7W21D) along with 15% polymer content is more helpful to improve the mortar properties compared to other mix proportions and curing conditions. Interestingly, the same combination resulted in a better performance in terms of water absorption, the coefficient of water absorption, sorptivity, toughness and salt/sulfate resistance as compared to polymer-modified mortars (PMMs) containing 0, 5, 10, and 20% polymer.

Environmental Earth Sciences, 2013

Gypsum-based mortars were widely used during the Mudejar artistic period in Spain from the 12th to 16th century. During restoration works, compatibility between the new repair mortars and the original components is essential for an adequate intervention on the monument. The increasing interest of knowing the properties of the gypsum-lime-based mortars for restoration purposes justifies the research carried out. Different mortars compatible with traditional building materials were elaborated by varying the binder proportions, the type of aggregates, the binder/aggregate ratios and the curing time. The main goal of this paper is to characterize the mechanical behaviour and the pore structure of the mortars as a function of curing time. The influence between the different variables used to prepare the mortars and the development of the carbonation process over time is also considered. Mechanical strength and porosity measurements as well as X-ray diffraction and thermal analysis were performed after curing times of 1, 28 and 90 days. The results obtained confirmed a progressive increase in mechanical strength linked to the carbonation of the mortars prepared. Less lime binder and also aggregate contents showed the highest rise in strength over time, related to the highest initial porosity which favoured the carbon dioxide flow. The use of siliceous aggregates (GL-QS mortars) obtained the best results in the development of physicomechanical properties over curing time. The knowledge obtained from the studied mortars provides practical information to establish a suitable mortar mixture for restoration works on historic buildings and modern architecture where gypsum-lime-based mortars are used.