A study into the effects of test variables on the results of concrete tests for salt scaling and alkali-silica reaction

The ability to accurately determine in-service deterioration of concrete remains an important facet of research. This research aims to develop more reliable laboratory testing methods to better replicate in-service conditions. Two concrete deterioration modes were studied; Salt Scaling (SS) and Alkali-Silica Reaction (ASR). For SS, wrapping slabs in plastic was adopted to provide the same curing environment as curing compound for comparison to standard moist curing. Slabs with and without supplementary cementing materials were tested. The two curing methods produced different scaling results; however, results of tested samples did not change in terms of meeting or failing the acceptance limit. For ASR, modified tests focused on changing sample size to attempt to reduce alkali leaching during testing, and hence produce results that mimic long term performance of actual structures. Cube moulds were designed, manufactured, and used rather than standard prisms. Increase of specimen dimension appear to reduce leaching at 38°C.

A study into the effects of test variables on the results of concrete tests for salt scaling and alkali-silica reaction

The ability to accurately determine in-service deterioration of concrete remains an important facet of research. This research aims to develop more reliable laboratory testing methods to better replicate in-service conditions. Two concrete deterioration modes were studied; Salt Scaling (SS) and Alkali-Silica Reaction (ASR). For SS, wrapping slabs in plastic was adopted to provide the same curing environment as curing compound for comparison to standard moist curing. Slabs with and without supplementary cementing materials were tested. The two curing methods produced different scaling results; however, results of tested samples did not change in terms of meeting or failing the acceptance limit. For ASR, modified tests focused on changing sample size to attempt to reduce alkali leaching during testing, and hence produce results that mimic long term performance of actual structures. Cube moulds were designed, manufactured, and used rather than standard prisms. Increase of specimen dimension appear to reduce leaching at 38°C.

Evaluating the Quality of Curing Applications on Concrete Pavements with Ground-Penetrating Radar

The management of concrete pavement curing must take several factors into account, such as the type of curing compound, the rate of the curing application, the uniformity of the curing application, the timing of the application, and the ambient weather conditions. This paper aims to elucidate a new curing application protocol for new concrete pavement construction and introduce a technique to address curing viability. Data for the development of the protocol were obtained from field investigations involving a series of test sections associated with concrete paving projects in: Victoria, TX; Itasca, IL; and Jacksonville, FL. For this undertaking, ground-penetrating radar technology was used to evaluate the efficacy of curing in relation to repeatability and uniformity. Statistical analysis was used to validate the utility of using dielectric measurements to qualify the curing quality. The rate of decrease in the dielectric constant was the critical parameter for evaluating a curing practice. Also, based on the coefficient of variation of data collection, the repeatability of data was acceptable. Finally, as a new method for checking the uniformity of curing applications, percent within limits (PWL) was implemented. Based on the PWL results, the hand-spraying led to a higher degree of non-uniformity in the spraying patterns compared with the spraying machine.

ANALISIS PENYEBAB RETAK MELINTANG DAN RETAK RAMBUT PADA PERKERASAN KAKU STUDI KASUS JALAN TOLL BAKAUHENI – SIDOMULYO (LAMPUNG SELATAN)

Pekerjaan perkerasan kaku pada proyek jalan toll trans Sumatera ruas Bakauheni- Sidomulyo, terjadi retak setelah pengecoran. Hal ini menyebabkan kerugian bagi pengguna jasa, sehingga peneliti tertarik untuk menganalisis terjadinya retak tersebut. Hasil analisis ini menjadi bahan pertimbangan dalam pengecoran perkerasan kaku, sehingga retak tersebut tidak kembali terjadi. Pengamatan dalam penelitian ini dilakukan sepanjang 39,4 km dengan 2 jalur 4 lajur, yang terbagi menjadi 31520 segmen. Retak melintang dibagi 2 tipe, yaitu retak pertengahan segmen dan retak saw joint. Jumlah retak melintang pertengahan segmen sebanyak 195 buah (0,58% dari total pengecoran), retak melintang saw joint 134 segmen (0,42% dari total pengecoran). Selain retak melintang terdapat retak rambut, retak rambut terjadi sepanjang 125 segmen (0,54% dari total pengecoran). Retak pertengahan segmen disebabkan adanya interval pengecoran yang lebih dari 15 menit antara beton yang telah terhampar dengan beton yang belum terhampar, sehingga terjadi perbedaan kembang dan susut pada batasnya. Retak saw joint dikarenakan bergesernya tulangan dowel dari as segmen dan keterlambatan pemotongan beton yaitu lebih dari 18 jam. Untuk penyebab retak rambut dikarenakan tidak meratanya penyiraman cairan curing compound saat proses pengecoran berlangsung. Retak ini juga dapat muncul saat masa pemeliharaan beton. Pemeliharaan dilakukan dengan cara penyiraman air ke permukaan beton, selain itu retak juga dapat muncul karena pemeliharaan yang dilakukan kurang dari 7 hari.

Study of the Effect of Different Concrete Treatment Methods on Concrete Compressive Strength

Proses pengikatan semen dengan air pada pembuatan beton akan menimbulkan efek samping berupa naiknya suhu pada beton yang biasa disebut proses hidrasi. Panas hidrasi yang terlalu tinggi dapat mengakibatkan keretakan pada beton, oleh karena itu perlunya dilakukan pekerjaan perawatan beton yang berfungsi untuk menjaga kestabilan dan ketersediaan air pada beton saat proses hidrasi. Penelitian ini menggunakan benda uji berbentuk silinder dengan ukuran diameter 15 cm dan tinggi 30 cm. benda uji yang dibutuhkan sejumlah 36 benda uji. Terdapat 3 jenis perawatan yang akan digunakan dalam penelitian yaitu perawatan perendaman, perawatan dibungkus dengan lembaran plastik, dan perawatan curing compound. Pengujian kuat tekan dilakukan pada umur beton 7.14, dan 28 hari. Hasil penelitian menunjukkan pengujian kuat tekan tekan umur 7 hari jenis beton dengan perawatan perendaman, perawatan dibungkus dengan lembaran plastik, dan perawatan curing compound berturut-turut 0.38 MPa, 1.68 MPa dan 2.29 MPa. Pengujian kuat tekan umur 14 hari jenis beton dengan perawatan perendaman, perawatan dibungkus dengan lembaran plastik, dan perawatan curing compound berturut-turut 21.97 MPa, 21.59 MPa, 20.29 MPa. Pengujian kuat tekan umur 28 hari jenis beton dengan perawatan perendaman, perawatan dibungkus dengan lembaran plastik, dan perawatan curing compound berturut-turut 25.89 MPa, 23.78 MPa, dan 22.48 MPa.

THE INFLUENCE OF DIFFERENT CURING CONDITIONS ON HVFAC RHEOLOGICAL AND MECHANICAL PROPERTIES

This research was conducted in order to evaluate the influence of different curing conditions on rheological and mechanical properties of high volume fly ash concrete (HVFAC) in comparison with the ordinary Portland cement concrete (OPC). Four types of concrete were made: two HVFAC and two OPC designed to have the same consistency and 28-day compressive strength for samples cured in water. Also, three different curing regimes were chosen: standard water curing (W), standard laboratory air curing (L) and curing in standard laboratory conditions using curing compound based on the polyolefin emulsion (C). The main objectives were to evaluate the influence of these curing regimes on the compressive strength, flexural tensile strength, modulus of elasticity development over time, water permeability of concrete and concrete shrinkage. The use of curing compound improved previously mentioned properties in some extent compared with the samples cured in standard air conditions.