This paper regards the axial behavior of reinforced concrete columns repaired by polymer-modified cementitious mortars. Tests were performed on eight columns with square cross-section: six were repaired with three types of polymer-modified cementitious mortars on all faces, two were in non-damaged and non-repaired condition (control elements). Tests were repeated varying mechanical properties (elastic modulus and compressive strength) of repair materials, maintaining the same repair thickness, including the reinforcement bars. Comparisons between repaired and control elements showed that polymer-modified cementitious mortars cannot restore the original load-bearing capacity of columns. In spite of this, selection of mortar mechanical properties plays a significant role. Among the three types of repair mortar tested in this experimental study, using the material with the most similar elastic modulus and higher compressive strength than that of the concrete substrate is recommended.

Efficiency of RC square columns repaired with polymer-modified cementitious mortars

Comprehensive study to accurately predict the water permeability of pervious concrete using constant head method

Fractional‐order freezing‐and‐thawing damage model for hydraulic concrete subjected to variable temperature processes

As buildings need to have not only high design but also durability, it’s necessary to think about multifunction materials. In this study, for the purpose of clarifying the basic properties of mortar and concrete using titanium oxide (TiO2) as an admixture, the authors have carried out experiments on the fresh and hardened properties focusing on the W/C and TiO2 ratios. The results suggest that workability properties could be satisfied and higher strength achieved by substituting optimum levels of TiO2. In addition, when examining brightness retention it was found that mortar containing 15% TiO2 had the best resistance to brightness degradation and self-cleaning performance with TiO2 as a photocatalyst. As a result, using proper TiO2 as an admixture in mortar or concrete can be useful for giving additional performance such as brightness retention and self-cleaning effects on the surface, as well as strength development and crack control of the specimen itself.

/pdf/experimental-studies-on-basic-properties-of-concrete-using-2bjbfe7ad8.pdf

EXPERIMENTAL STUDIES ON BASIC PROPERTIES OF CONCRETE USING TiO2 AS ADMIXTURE

The purpose in this study is to investigate the rational mix design method of water permeable concrete sat isfying environmental and structural requirements such as a proper coefficient of permeability and compres sive strength. Voids in the concrete were classified into the three types of void of permeable, non permeable and entrained air, and the absolute volume of aggregates, and the volume ratio of cement paste to aggregates were defined in this study. Thus, the new mix design method for a water permeable concrete by vibrating compaction was proposed and applied availably for the practical mix proportion. Mechanical properties such as modulus of elasticity, tensile strength and flexural strength of the water permeable concrete were also measured.

Mix Design and Properties of Water Permeable Concrete Compacted by Vibration

This paper describes relationships between physical properties, mechanical properties and performance of NOx remediation of mortar incorporating titanium dioxide powder, and incorporating ratio of the powder. Physical properties such as a mortar flow and an air content were investigated by controlling dosage of a high-range water-reducing and air-entraining agent and of an air-entraining agent. Compressive strength, tensile strength, flexural strength and modulus of elasticity of the mortar decreased slightly with increase of the incorporating ratio of the powder. However, ratios of tensile and flexural strength to compressive strength, and Poisson’s ratios of the mortars were almost constant if the incorporating ratio changed. The mortar with the incorporating ratio of 15% showed about 30% of NOx remediation ratio. Performance of the NOx remediation had an effect of the incorporation of the powder. The mortar investigated in this study can be expected to apply to concrete structures such as a handrail, large scale pavement and a box culvert because of a high strength and a performance of NOx remediation.

https://www.jstage.jst.go.jp/article/jsms/55/10/55_10_923/_pdf

Physical Properties and NOx Remediation of Cement Mortar Incorporating Titanium Dioxide Powder

Stress and deformation of concrete members repaired by polymer mortar

コンクリートの多様性を追求する様々な研究が行われてきているなかで, 多孔質コンクリートに対する開発および応用についての研究も活発になってきている. 本研究は多孔質コンクリートの一種である透水性コンクリートの振動締固め方式によって製作する場合の配合設計法を論じたものである. 透水性コンクリートは用いる環境に応じてその透水係数ならびに強度などを配合によってコントロールすることが一般に必要である. 本研究では, 設定した透水係数と強度を得るための配合設計法を構築するために, 空隙を透水性に関与する連続空隙, 透水性に関与しない閉そく空隙およびマトリックス中の気泡の3種類に分類し, セメントペーストと骨材の容積比, 骨材の実積率などを用いて, 配合諸量を決定する配合設計手法の構築を試みた.

Mix design method of water permeable concrete by vibrating compaction

本研究は酸化チタンを混和した高強度セメントモルタルの物理的性質，および窒素酸化物除去性能とその機構について実験的検討を行ったものである．酸化チタン混和高強度セメントモルタルの物理的性質には酸化チタンの種類や混和率が大きく影響し，また酸化チタン粉末の混和により硬化体組織中の200nm以下の細孔を増加させることも明らかとなった．一方，窒素酸化物除去性能は酸化チタン混和率の増加とともに向上するが，養生中の析出物により窒素酸化物除去性能が低下することも明らかとなった．さらに窒素酸化物除去試験後の窒素酸化物イオンの溶出試験結果から，酸化チタン混和モルタルの結合材中には硝酸イオンおよび亜硝酸イオンが滞留することが明らかとなり，窒素酸化物除去機構に影響を与えることがわかった．

Hidenobu Tokushige

Papers

Physical Properties and NOx Remediation of Cement Mortar Incorporating Titanium Dioxide Powder

Stress and deformation of concrete members repaired by polymer mortar

Mix Design and Properties of Water Permeable Concrete Compacted by Vibration

Mix design method of water permeable concrete by vibrating compaction

Nitrogen oxides removal function and its mechanism of high-strength cement mortar incorporating titanium dioxide