The performance of hardened wet-process sprayed mortars

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.

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

Proceedings of the International …

1999

2002

Materials and Structures, 2007

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 fine concretes. It follows on from an earlier paper by the authors on the performance of hardened wet-process sprayed mortars and some comparisons with these are made here 1. Work has also been completed by the authors on the pumping and rheology of the fine concrete mixes presented here 2. Nine laboratory-designed fine concretes were pumped and sprayed through a wetprocess piston pump and one through a dry-process pump. The properties measured included compressive and flexural strength, tensile bond strength, hardened density, elastic modulus, sorptivity and drying and restrained shrinkage. Insitu test specimens were extracted from 500x500x100mm deep sprayed panels. Hardened property tests were also conducted on corresponding cast specimens and, where possible, on specimens that had been sprayed directly into a cube or beam mould. The compressive strengths of the cast cubes, although very similar, were usually slightly greater than the in-situ cubes, the opposite of what was found for wetsprayed mortars 1. Inconsistent results for compressive and flexural strengths obtained from spraying directly into a steel mould suggest that this method is not as reliable when using a piston pump as it is when using a low-output worm pump 1. The bond strength of all the mixes exceeded 2.1 MPa at 7 days. The values for modulus of elasticity, when compared with the compressive strength, were similar to published data for this relationship. The sorptivity values showed only a slight relationship with the compressive strength. 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. Low-volume wet-process sprayed concrete: hardened properties Version 3 Chris Goodier

1996

This research project has proved to be unique in both its focus and scope, and has produced a substantial array of knowledge and performance data for wet process sprayed mortars/concretes for repair.

Repair mortars are being used with increasing frequency to maintain the aging US infrastructure. Durability is a key concern for such repair materials and both their volume stability and bond to the existing concrete are key attributes, the former to avoid excessive cracking of the repair and the latter to ensure that it remains in place as an integral part of the (repaired) concrete structure. This paper examines the volume stability of two commercially available repair mortars by measuring their autogenous deformation to an age of 28 d. Internal curing is examined as a strategy to mitigate the significant autogenous shrinkage encountered for both materials. The performance of pre-wetted lightweight aggregates (LWA), a superabsorbent polymer (SAP), and a superabsorbent polymer-coated sand (PCS) with respect to compressive strength and autogenous deformation are evaluated. Because these three internal curing agents have water absorptions spanning two orders of magnitude, they have differing influences on the proportioning of the mortars and on subsequent performance. In general, when proportioned with the same amount of internal curing water, the mortars based on LWA exhibit the highest compressive strengths and the greatest relative reductions in autogenous shrinkage in comparison to the controls formulated without internal curing.

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...