This research examines the significance of using carbon nanotubes (CNTs) on the mechanical characteristics and microstructural features of latex modified mortar (LMM). CNTs have been introduced recently as a new nanoscale material with excellent mechanical properties. This work examines the ability of various CNTs’ contents to alter the mechanical properties of latex modified mortars. Compression and tension tests were performed on LMM specimens with and without CNTs at 7 and 28 days of age. The experimental investigations showed that CNTs can enhance the strength and deformation characteristics of LMM. Microstructural investigations showed CNTs to be well dispersed and bonded to the polymer latex matrix. It is concluded that CNTs can be a useful alternative to enhance the mechanical characteristics of polymer modified cement composites.

It is generally accepted that the latex-modified concrete (LMC) overlay is a superior protection system for bridge decks. The incorporated latex acts as a plasticizing agent providing good workability even for low water/cement ratios. When exposed to air, the latex polymerizes forming a membrane around the hydration products resulting in a lower permeability and inherent flexibility to resist freeze and thaw cycles. Nevertheless, the latex imposes constructability limitations that dramatically increase the initial installation cost of the LMC overlay. The latex starts to polymerize within 15-30 minutes dictating the need for mobile mixers to install the LMC overlay. The cost of the latex adds to the cost of the LMC especially when the oil price increases. This paper presents and discusses the effect of different types and combinations of macro and micro synthetic fibers on the major performance characteristics and constructability of the fibrous LMC overlay.

The following paper documents the preliminary experimentation and analysis of a polymer fortified hydrated cement sample. Concrete is a brittle construction material. When compared to other construction materials, concrete can offer competitive structural resistance under compressive loads. But due to the brittle nature of the hydrated cement matrix, C-S-H network, concrete is poor when resisting flexural loads. The brittle C-S-H structures cannot absorb the flexural energy like a ductile material. The properties of concrete fracture are analyzed at the microscopic level to understand the method of failure. By including the acrylic polymer into the hydrated specimens it was the belief of the authors that the acrylic polymer would enhance the fracture behaviour of the concrete in flexure. The C-S-H hydrates precipitate from a saturated solution. The acrylic polymer, after being mixed into the cement paste while still fresh, becomes secured in the C-S-H structure as said structure hardens. Samples were cast, cured, and tested in order to determine if the acrylic polymer cause the C-S-H structure to behave in a ductile manner. The testing included compressive and flexural stress tests with microstructure observation via Scanning Electron Microscope (SEM). The compressive and flexural tests were used to discern a measured value of gain when using an acrylic polymer compared to a control mix. The SEM images were used to determine crack origin, type of failure, and acrylic polymer benefit. The tests and SEM images revealed that there was a negative reaction between the admixtures to cause an excessive air generation. Despite the setback, the SEM images revealed evidence of energy absorbing of the acrylic polymer mix.

Polymer modified concrete (PMC) was introduced to address some of the disadvantages of normal concrete such as low tensile strength and vulnerability to chloride penetrability. Latex-modified concrete (LMC), a type of PMC where latex-based polymers are used, is usually utilized in special applications that require some of PMC’s advantageous properties. Approximately 10% of all latex paint purchased in the United States becomes unused. This waste latex paint (WLP) contains volatile organic compounds (VOC), which makes it difficult and expensive to recycle. Using WLP in concrete as a replacement for styrene-butadiene rubber (SBR) has been found to produce a PMC comparable to LMC. WLP could produce a cost effective PMC as it can replicate the improved properties of LMC. Bridge overlays use LMC due to its durability under environmental conditions and traffic loads. Bridge overlays are subjected to chloride ion ingress, which may result in corrosion of the reinforcement and surface scaling of concrete. In this study, four concrete mixtures were evaluated. These mixtures consisted of a control mixture of normal concrete, one with SBR, and two with WLP. The experimental program included fresh properties as well as hardened properties. Results showed that a WLP mixture can meet the requirements for LMC bridge overlays. The success of the proposed technique can result in a total of one to two million cubic yards of inexpensive LMC produced in the United Sates yearly, with a substantial recycling of WLP.

Concrete mixtures, having a water/cement ratio below 0.4, may exhibit a considerable autogenous shrinkage induced by internal drying of the capillary pore structure. In order to compete with this issue and to avoid or compensate for the development of autogenous shrinkage of concrete, either the mix proportions have to be adapted or additional (internal) water has to be supplied with emphasis on the moisture state of the capillary pore system. Until recently, one of the most frequently used methods used to retain internal self-desiccation of concretes was by adding water saturated porous light weight coarse aggregates (i.e. Lytag) or wood pulp fibers to the cementitious matrix. One of the latest innovations in this area is the addition of shrinkage reducing additives such as Super Absorbent Polymers (SAP). In order to examine the pros and cons of SAP addition to a concrete mix, an extensive experimental programme considering eight different concrete mixtures have been tested at Delft University of Technology. It is investigated how the Super Absorbent Polymers influence the mechanical and viscoelastic properties of hardening concrete. Experiments are performed for water/cement ratios of 0.32, 0.39 and 0.5, for Portland cement as well as Blast Furnace Slag cement, with addition of three different percentages of SAP, i.e. 1, 1.5 and 2 kg/m3 (1.68, 2.53 and 3.37 lb/yd3). The mixtures are tested at isothermal conditions of 20 ºC and the early-age autogenous shrinkage strains are measured over a testing period of about 300 hours. Besides, the tensile strength, compressive strength, the elastic modulus and the creep strains have been measured for the different mixtures as well. The tensile, compressive strength and elastic modulus are tested at 28 days of age. The early age creep of the mixtures was measured from prisms and tested under a sustained compressive load of 40% of the compressive strength and were loaded at an age of 3 and 7 days. In this paper, the results of the experimental program are described in detail. A significant effect of the reduction of autogenous shrinkage due to SAP addition was observed. However, results also show that SAP affects the tensile and compressive strength and the viscoelastic properties like elastic modulus and the early age creep.